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The Craftmans Shop => New from Old => Topic started by: awemawson on November 14, 2016, 09:49:01 AM

Title: Titivating A CNC Plasma Table
Post by: awemawson on November 14, 2016, 09:49:01 AM
In early October I bought a CNC Plasma Table - motivated by needing a few bits cut for that Flail Mower, and always having hankered after one it seemed a good excuse  :clap:

It is a home made one with a capacity of approximately 1500 x 1500 (mm) - uses HiWin rails, stepper motors driving rack & pinions and came with a Hypertherm 45 Plasma cutter complete with a machine torch. Also it has an automatic torch height control which is a big advantage.

Although I'm glad to say it worked as bought it was obvious to me that it was going to have to be re-built as the wiring and arrangement of the control box was not at all to my liking.

Now when I got it, it got pushed into a corner of the welding shop where I used it successfully to make the bits I needed, but it became obvious that with it there no improvements were going to happen, as it wasn't very accessible, and it's rather chilly in there at the moment.

So today was the big day to move it - clearing all the odds and sods out of the way in the welding shop and fork lifting it into my operating theatre project space  :ddb:

So a few pictures for a start:
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on November 14, 2016, 09:57:36 AM
When a CNC Plasma table is going full tilt it blows burning metal particles downwards creating much mess, fumes and nastyness, so one of the first things I intend to incorporate is a powerful down draught extract system.

Basically an upside down hood under the bars of the table acting as a funnel to collect all the debris and fumes which are removed by a fairly beefy extractor fan - probably 12" diameter in this case though not fixed yet.

Googling about in various forums I came across a neat layout, and contacting the builder he was happy for me to do a direct crib of his idea - why re-invent the wheel - so these pictures are of his table and extract duct

I'll probably get a local duct work firm to bend it up, as although I've got the bender and guillotine they can probably do it for not much more than the materials would cost me to buy
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on November 14, 2016, 10:02:25 AM
Immediately under the support bars I'll fix a mesh to catch the larger 'drops' from cut outs, and the collecting box will have a spark arresting fine mesh on it's output.

So the way it looks at the moment the job list is:

a/ get an extract duct bent up

b/ source a suitable sealed steel enclosure for the drive electronics that can be fixed to the side of t he machine

c/ decide whether to put a PC inside same enclosure (ventilation issues)

d/ incorporate limit switches

e/ totally re-vamp all the wiring to hopefully a rather better standard than currently.
Title: Re: Titivating A CNC Plasma Table
Post by: AdeV on November 14, 2016, 11:00:25 AM

c/ decide whether to put a PC inside same enclosure (ventilation issues)


You can get some pretty decent fanless PCs these days. If you're not wedded to Windows, you could probably get away with using a Raspberry Pi 3 [and allegedly Windows 10 will run on one, but IMHO that's just cruelty to silicon].
Title: Re: Titivating A CNC Plasma Table
Post by: nrml on November 15, 2016, 02:46:31 PM
Or one of the increasingly popular DDCSV 1.1 or similar boxes? It would be perfect for this sort of environment.
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on November 15, 2016, 03:52:18 PM
No nice as they may be I don't want this to turn into a long & protracted learning curve. I have a spare Dell Optiplex ultra small form factor with an SSD fitted that'll do the job.

I've made a little progress in that I've been spending money on needed bits - I've sourced:

1/ a nice 800 x 600 x 300 Schneider electrical cabinet

2/ a blower that claims to shift 3900 cu/M/ an hour

3/ some jumbo non-flammable air hose 315 mm i/d

4/ some mammoth Jubilee clips to stick them together

5/ and a wall plate to get the fumes outside

Meanwhile my sketch for the under duct / inverted hood thing is with a sheet metal work place I didn't previously know existed only just over 1/2 mile from the house - hopefully getting a quote to me tomorrow  :ddb:
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on November 16, 2016, 06:51:52 AM
A bit more dismantling progress this morning:

The down draught exhaust duct is going in from the top, so the slats that support the work piece need to come off as well as the slat supports. Simple pull out for the slats - these are expendable, and inevitably get cut to pieces in use.

I've furnished myself with a complete new set, but obviously will only introduce them as needed - for the time being I've sorted the old ones into an acceptable pile and a grotty pile, and then removed the box section that supports them. One is rather bowed - not that it shows much in the picture, but I'm going to have to re-work them anyway, as the duct metal will be trapped by them to the frame, so the supports will need shortening by two metal thicknesses. I will probably introduce a third support that will have slots out of phase with the other two, allowing the slats to be held in a curve. This minimises slat cutting when rectangular parts are being cut.

The chap who built this welded a bit of 75 x 4 mm plate to the side frame to aid aligning big sheets - this will need cutting off before the duct is installed as it's in the way, also there are mysterious 'lumps' welded on in places that need dressing off for the same reason
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on November 16, 2016, 06:57:12 AM
So now I need to work out how to temporarily hook it back up to it's drive electronics so that I can move the gantry up and down, while I wheel it outside to attack those extraneous bits with an angle grinder  :scratch:

(The angle grinder is banned from the 'clean' workshop  :clap: )
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on November 16, 2016, 07:19:49 AM
Well looking again at the plate he'd welded on the solution was obvious  :bang:

He'd not made it full length as obviously the gantry was fitted before he fixed it, drive the gantry down the far end and all is exposed. OK still meant lashing the electronics back on, but no need to make them 'portable' when I drag the table outside for fettling  :ddb:
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on November 17, 2016, 10:49:50 AM
Not a lot done today - the morning was taken up by an interrogation by the local Planning Authority's consultant 'farming adviser' over my application for planning permission for a tractor shed. I wasn't looking forward to it, but in the event he went away convinced it WAS needed for agricultural purposes (honest!) and I almost managed to sell him a freezer pack of lamb  :ddb:

By the time he'd left, the heavens opened and there was no chance of pulling the table out side for grinding - so how to proceed :scratch: Then I remembered a recent 'impulse purchase' of a rather nice electric Die Grinder - this was occasioned by not being able to dress welds back as neatly as I'd wanted to on the Flail Mower - the usual 'fixing the previous problem' purchase  :lol:

...well the Die Grinder hasn't been banned from the clean workshop, as after all it doesn't chuck grinding dust everywhere, only filings, and as it's Tungsten Carbide bit is a small diameter they don't go far anyway  :thumbup:

So I ground back the welds aiming to weaken them enough to break them and leave the parent metal untouched - largely successful but a bit of filler before a coat of paint will hide any imperfections.

The locating bar came off nicely, then I attacked that odd 'lump' on the inside of the frame only to discover that in fact there were three of them. I suspect he had had the slat supports running at right angles to where they are now, and these are the artefacts surviving his re-make. Well off they came and with a bit of hand filing everything got dressed back to an acceptable level allowing the duct to fit (I hope - still not got the quote yet)

Anyway - have some pictures
Title: Re: Titivating A CNC Plasma Table
Post by: millwright on November 17, 2016, 02:03:42 PM
And so another saga is unfolding, looking forward to reading of your trials and tribulatations on the way, and your triumph and the end of it all when another piece of equipment is resurrected Andrew. i always enjoy your projects.  :clap: :clap:

John
Title: Re: Titivating A CNC Plasma Table
Post by: Pete W. on November 17, 2016, 02:06:20 PM
And so another saga is unfolding, looking forward to reading of your trials and tribulatations on the way, and your triumph and the end of it all when another piece of equipment is resurrected Andrew. i always enjoy your projects.  :clap: :clap:

John
 

I agree.    :bugeye:   :jaw:   :bugeye:   :jaw:   :bugeye:   :jaw:  :mmr:   
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on November 17, 2016, 02:49:44 PM
Kind words, and much appreciated chaps  :thumbup:
Title: Re: Titivating A CNC Plasma Table
Post by: DICKEYBIRD on November 19, 2016, 09:45:27 AM
Holy cow Andrew; do you ever sleep?  Watching what you get accomplished in one day tires me out.  I need some of whatever vitamins (or drugs) you take.  I don't care if they're legal or not! :)

Seriously, thanks for posting your work in so much detail.  It's very inspiring to watch you do all of these amazing projects. :beer:
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on November 20, 2016, 06:36:29 AM
Nothing physical on the Plasma Table today - resting up after quite a hike yesterday round Virginia Water / Windsor Great Park with the dogs and an extended pleasant lunch with my son and his fiancee preceded and followed by rather too long on the M25 !

However cogitation time ... I wanted to look at limit switches ... this table has switches on all three axis, however they are not wired in, and one is physically broken (he hit it with his fork lift he told me)  :scratch:

Now I want active limit switches, but I hate the way these have been mounted - they are the normal roller type but are effectively being used as 'long stops' - if an axis does over travel it will squash the limit switch and break it. In my book there should be a physical / mechanical stop at the end of axis travel - possibly with a buffer of some sort, but this should be preceded by a limit switch THAT CAN BE PASSED so a bar or ramp or what ever operates the switch in such a way that the roller ISN'T a physical stop. Re-engineering this is not going to be easy as it isn't how he designed it, and will probably involve a few bits bolted on to change the way the switches are triggered. (Space is tight on the Z carriage and gantry.)

First step was to locate a replacement for the IMI IMP switch that was broken, and fortunately it's an RS Components stock item so one should be here on Monday.
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on November 24, 2016, 09:19:50 AM
Well at long last I've been able to place an order for the duct to be bent up. The company I'd discovered very close to here didn't get their quote to me until this morning, and they can't start work until the new year  :bang:

So my 'second line of defence' is a small outfit a few miles away that are apparently less well set up looking at their rather shambolic workshop, but were very slightly cheaper and could start next week  :ddb:

Mean while I'm catching up on a few 'round tuits'
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on December 02, 2016, 09:50:24 AM
Still waiting for the duct to arrive, so I decided to make a start on the central third slat support rail. 40 mm square box section fixed on height adjustable brackets at top and bottom of the table, and carrying a 40 x 40 mm x 3 mm angle iron slotted every 50 mm to take the slats. I made the brackets a while back.

Now I'd been wondering what was the best way to cut the slots - the slats are 3 mm thick so a 4 mm slot would be ideal. The original pair of angles are rather uneven and look to have been cut with an angle grinder. I decided to use my Pedrazzoli cold saw, but it has a 2 mm blade, so each slot consists of two cuts carefully spaced - rather fiddly but it seems to have worked OK. I cannot cut the 40x40 support rail yet as it's length depends on how thick the duct ends up.

Then I thought I'd better get a bit of paint on the side rail where I'd cut off the previous owners alignment plate to allow the duct to fit when it comes (I'll bolt a plate back rather than weld it). This is really just to stop things rusting as most of the top of the side rail was bare metal.

Turns out that 'Ford Tractor Blue' in not too bad a match for whatever the frame has been painted in - at least it doesn't shout 'I'm different' and I had 5 litres on the shelf :lol:

Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on December 03, 2016, 06:13:26 AM
A little bit of progress this morning that is actually a big psychological boost as I wasn't looking forward to it -

I've down loaded a legal copy of Mach3 onto a Dell Optiplex Ultra Small Form Factor PC running Windows 7 that I've fitted with a solid state drive, and managed to transfer all the settings from his original set up on a wacking great Dell tower system he was using, AND IT WORKS - happily driving his original electronics. (These will be re-engineered in the electrical enclosure)

All this because at the moment my intention is to house the PC safely within the new electrical enclosure to keep it out of harms way - with just the monitor and keyboard on a stalk somewhere.

Having proved it works I'm now more motivated to plough on with the electrical enclosure.
Title: Re: Titivating A CNC Plasma Table
Post by: mattinker on December 03, 2016, 09:46:02 AM
I'm looking forward to seeing this when I come over to the UK!

See ya, Matthew
Title: Re: Titivating A CNC Plasma Table
Post by: Pete. on December 03, 2016, 11:51:54 AM
I have an enclosure here that I believe will suit that, if you want it Andrew.
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on December 03, 2016, 12:09:59 PM
That's very kind Pete, but if you look 'up thread' you'll see a picture of the one I've bought  :thumbup:
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on December 04, 2016, 06:57:23 AM
Catch 22 rears it's ugly head  :bang:

Experimenting with the Dell Optiplex 780 Ultra Small Form Factor, I can set it's power sequencing so that if it looses power it will start up again when power is resumed but the running software may well corrupt. However, if the PC is closed down in an orderly manner by pressing the 'Start' tab then selecting 'Shut Down', when power is resumed the PC doesn't start up and the front panel Power button has to be pressed. Sometimes Windows is happy if it is put in 'Sleep' mode before loosing power, but about one in three times it wants to start in 'safe mode'.

So why does this matter :scratch: Well if the PC is located in the electrical enclosure YOU CANNOT PRESS THE POWER BUTTON  :bang:

Now I've thought of hard wiring an external button, but that's a bit crude as the PC layout doesn't lend itself to this. So I'm coming to the conclusion that the PC will have to be strapped to the outside of the enclosure. Not the end of the world, and in practice means less plugs and sockets, as the monitor and keyboard and mouse are already external, as is the USB socket for transferring files. But it's not quite the neat solution that I'd hoped for.

As it happens I have a 'desk mount sleeve' for the Optiplex 780 USFF so actually mounting it isn't too much of an issue
Title: Re: Titivating A CNC Plasma Table
Post by: russ57 on December 04, 2016, 07:12:02 AM
A long time ago,  I  fixed a "power up after power failure"  on a large fleet of PC's (8000),  by hacking the power on lan feature.  I think we ended up with just a capacitor across the reset button -  it effectively held reset low until power was fully up,  then the pc saw it as the reset button being released .  Did you check through all the bios options?  Sometimes there is a feature to either power up,  or return to the state before power fail.
-Russell

-russ

Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on December 04, 2016, 07:30:38 AM
Thanks Russ, yes been through all the bios settings and experimented - even tried the 'wake up on Lan' as the 'network' is in fact the torch height controller via Ethernet and an Ethernet breakout board - I'd hoped that their activity might wake it up but no !
Title: Re: Titivating A CNC Plasma Table
Post by: DMIOM on December 04, 2016, 08:18:12 AM
Andrew - does it have a serial port? - some time ago I did something similar by using the "Wake on ring" feature in the BIOS.

Dave
Title: Re: Titivating A CNC Plasma Table
Post by: philf on December 04, 2016, 08:33:43 AM
Andrew,

According to the manual for your your PC these options should be in the BIOS:

Power Management
AC Recovery Determines how the system responds when AC power is re-applied after a power loss. You can set the
AC Recovery to:
Power Off (default)
Power On
Last State


Power on would be my choice with the program you want to run in Start Up. (Or a scheduled task to run on start up.)

I am using an old Dell PC in the power house of our hydro scheme and use this facility. It has a UPS but I had to remove the UPS software which turns the PC off in the event of a Power Failure after a preset time because the PC then didn't wake up.

Phil.

Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on December 04, 2016, 08:46:30 AM
Phil, yes those are the settings I've experimented with.

Reverting to 'Power On' works fine if power was lost when the PC was running, but of course Windows objects to just being turned off.

Reverting to 'Power On' Does NOT work if the PC was closed down in an orderly manner.

I reckon a strategically positioned spring loaded plunger on the enclosure door pointing at the 'Power' button may end up being used  :lol:
Title: Re: Titivating A CNC Plasma Table
Post by: PK on December 04, 2016, 06:12:59 PM
The power button will just go to two header pins on the motherboard. Could you not unplug it and run them to a connector on the back of the box?
That way you could plug an external power switch in. It'd be a neat and tidy solution for you. You could even keep the switch on the case in parallel (they are normally open switches.

I'm happy to put this and the external power switch assembly together for you if the electrickery stuff isn't your thing....

PK
Title: Re: Titivating A CNC Plasma Table
Post by: Pete. on December 05, 2016, 02:47:19 AM
I've had several SFF optiplex's and I do recall having this problem with one of them. Only trouble is I cannot remember how I got rid of it. Probably with a clean wipe.

Do you have a Dell install disk? With those you can re-install windows without the need of a key.
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on December 05, 2016, 03:00:28 AM
PK, the whole front panel electrics including two USBs etc as well as the relevant button are on one multi-way header and it's extremely cramped.. This thing is small! But thanks for the suggestion and offer.

Pete, I think it's working as they designed it, another Optiplex 780 USFF that I have does the same.
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on December 05, 2016, 10:02:02 AM
So today's job - mount the electrical cabinet.

Location concept -

a/ Make the top surface below the top rail so that it doesn't get nudged when mounting plates for cutting.

b/ Position it so that the PC in its mounting sleeve will fit on the left hand side of the cabinet leaving room on the right for a shelf for the Hypertherm 45 Plasma Cutter

Now the top rail on this end of the chassis is 40 mm further 'in' on the machine than the bottom rail so somehow it needs spacing off. I was going to make some mild steel spacers from fat hex bar and paint them blue, but decided to save a day of paint drying by making them from stainless steel round bar. Only down side - needed to drill a radial hole for a tommy bar to tighten them up.

So, cut two 40 mm slices off the bar - tapped both ends M8 - Loctited some M8 BZP bolts in the end - cut the bolt heads off and bobs you uncle - spacers ready to go.
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on December 05, 2016, 10:06:44 AM
So this let me hang the enclosure on the studs on those spacers, to let me mark out where to drill the cabinet to align with the lower horizontal bar.

Then it was just a case of marking and drilling the enclosure - tapping the rail M8 and fixing it on.

I have to say my hydraulic pump up table gizmo was very handy in this regard as the enclosure is blooming heavy
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on December 05, 2016, 10:11:58 AM
Then to mount the PC sleeve on the left side - I could have just used nuts and bolts, but as I want to hang the door on the other side reaching round it would be a pain, so I dug out my Nutsert / Hank Bush kit. Doesn't get used very often, but one of those things that's ever so handy when needed.

Just two M8 Hank Bushes, and bolt it on - I've positioned the PC so it is slightly back from other surfaces so hopefully not the first thing to get thumped accidentally when moving it about.
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on December 05, 2016, 10:19:55 AM
Then to reverse the door: cabinet obviously designed for this - just a case of pushing plastic blanking plugs out of the side that will now take the hinges, pushing out the hinge pins, unbolting the hinges and re-building it all on the other side.

.. then don't forget to put the plastic blanking plugs back where the hinges were originally - this bit took more time than the removal and re-fixing of the door - they DIDN'T want to go back  :ddb:

Like most of these enclosures, this one came with a steel 'back panel' that bolts inside to take whatever you are putting in there without having to put holes in the back of the cabinet. Very heavy - made from 2.5 mm plated steel. I will probably fit a pair of handles to it to aid taking it in and out, as with all the rest of the gubbins mounted on it, it will be very unwieldy.

So now with the cabinet mounted, I can give serious consideration to laying out the CNC modules and Power Supplies on that panel and have a proper feel for how cables will have to run.
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on December 07, 2016, 07:48:07 AM
Today the duct arrived  :ddb:

Quite nicely made, but I probably should have left more 'tolerance' on the size as it was a bit of a struggle to get it in place. The corners had to be peeled back (I'd had them leave them loose so I could) to get it into the plasma table. Then it was a case of locating the tapped holes for the two existing slat support rails and drilling through to them, and fixing it in place with umpteen 6 mm screws in drilled and tapped holes.

All went reasonably well - only broke one tap and sheared the heads off 5 screws  :bang:

If I was doing this again, I would have changed the shape of the funnel from symmetrical to uneven to locate the clean out door nearer the edge for ease of access.
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on December 07, 2016, 03:06:52 PM
This afternoon I shortened and re-fitted the two original slat support rails, and finished welding up the new third one and fitted it. They are not yet adjusted for height - a job for tomorrow.

Another job for tomorrow is to shorten all the slats, as now the duct is installed they, like the slat support rails, are 2.4 mm too long - not that they need to be such a tight end to end fit as they were - but at the moment they won't go in  :bang:
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on December 08, 2016, 07:28:17 AM
So having done the farm chores (including moving all the chicken into a sealed polytunnel due to the threat of Bird Flu H5N8 * ) I could get on with aligning the slat supports.

I set them so the top of the slat / bottom of cutting victim is 5 mm above the side rails for no reason other than it seemed sensible that they receive the sheet when being initially loaded rather than the side rails - previously they'd been a couple of mm below the rails. If it proves to be a wrong decision it is easily reversed as they mount on adjusting slots.

Having got to this stage it was time to insert a catching mesh - it will be a pain if little bits that you want fall between the slats and have to be fished out through the clearing door - at least with a mesh they can be recovered with a 'magnet on a stick' fairly easily. I'm not certain that this mesh will be entirely satisfactory as I fear that it might impede air flow too much. It just sits in so is easily replaceable - it started off as a one metre square of galvanised expanded mesh and I turned up the edges 25 mm to stiffen it a bit. (Actually it started as a full 1250 x 2500 mm sheet that was great fun manipulating single handed - amazing how often it catches on things including clothing  :bang: )

Right ho - time to trim those slats - no wait a minute, the whole idea about adding a third support rail for the slats was to curve them, which will reduce the 'chord length' - but how much. Answer - by just the right amount  :clap:

So the acceptable original slats have been returned to service along with seven new ones to replace the unacceptables.

Now I need to plot and scheme how things will be laid out in the electrical enclosure - I'm umming and arhing about whether to direct hard wire motors and sensors into the cabinet, or the use plugs and sockets. My thought at the moment is that there is no great benefit to the plugs and sockets, and its another thing to fail in the future. I intend to bring all wiring into the cabinet and first to a 'DIN rail mounted terminal strip' which will give an easy point of disconnection and also useful for test purposes.




(* http://www.edp24.co.uk/home/defra_tells_poultry_keepers_to_take_precautions_against_bird_flu_outbreak_1_4806869 )
Title: Re: Titivating A CNC Plasma Table
Post by: Spurry on December 08, 2016, 10:09:56 AM
Glad you have the slats sorted. I was surprised yesterday when you said they were too long. I thought I had read of your intention to curve them, but could not find that comment, so thought perhaps I had imagined you had said it. Seems not.  :bugeye:
Looking good so far.
pete
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on December 08, 2016, 10:44:09 AM
This afternoon I made the bits to add handles to the back panel of the enclosure that holds all the driver electronics and power supplies - It'll be too heavy to maneuver without them, and as I'm shuffling 'Blue Peter' models of the components to decide positions, they need to be able to speak for themselves in the debate  :lol:

Not exactly hi-tech - just four slices of 20 mm A/F brass drilled and tapped M8 and some flat strip I got years ago when Proops Bros were closing down - it's a bit more than mild steel (cracks if bent and is semi hard) and has rounded edges so is handy for this sort of application.

Been cogitating on the best way of getting all the existing (*) cables into the cabinet - went through a/ 50 mm galvanised conduit b/ weld up a duct from 70 mm box section c/ a length of 50 mm Adaptaflex flexible conduit - all designed to keep the cables away from the sparks. Then reason prevailed when I realised that the cable drag chain / flexible duct is plastic anyway, and the new extraction duct nicely shields things from sparks. So I've decided to use a bundle of perfectly ordinary corrugated 20 mm pvc cable duct, slightly influenced by the fact that I already have it on the shelf  :ddb:

(* I'm actually going to replace the cabling as it's rather tatty - two drums of 4 way screened on order in 0.5 csa and 0.75 csa )
Title: Re: Titivating A CNC Plasma Table
Post by: Will_D on December 08, 2016, 05:46:39 PM
Watching "How its Made" tonight on Discovery, they were building Big road rollers in Scandinavia (?).

They were plasma cutting 25 mm steel.

Question is how do you stop cutting the support matrix (i.e. your slats)?

Same goes for laser cutters and water jets
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on December 09, 2016, 03:01:13 AM
You don't - they are expendable. The reason for curving them is that you are less likely to cut all the way along a slat as most cuts are straight lines.
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on December 09, 2016, 06:10:03 AM
More layout cogitation this morning, aided by making 'Blue Peter' models of the items needed mounting just to make sure everything fits and can be 'got at' for wiring and later servicing.

Can't go much further until an order for more DIN terminals arrives - hopefully tomorrow.
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on December 09, 2016, 08:14:21 AM
Then I made and fitted a 'Plasma Perch' - just a shelf to put the Hypertherm 45 on so that it is out of all the muck and bullets on the floor.

Simple job bent up from 1.2 mm Zintec and re-inforced by a pair of brackets left over from making the pig-sty's  :ddb:

Trouble was that there are very limited places it could go, and no easy way of stiffening it up without those heavy duty galvanised brackets, which actually double up as stops for the Hypertherm, preventing it walking backwards or forwards - happen stance - not planned  :clap:

I will need to put a 90 degree fitting on the air inlet, or the pipe will go though an unacceptable bend radius.
Title: Re: Titivating A CNC Plasma Table
Post by: mattinker on December 09, 2016, 11:58:51 AM
What is Zintec ?[


Knit one, pearl one............

All the best, Matthew.
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on December 09, 2016, 12:26:34 PM
Zintec is electro-zinc plated steel Mathew. So essentially rust proof, but the zinc is nothing like as thick as on hot dipped galvanised.
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on December 10, 2016, 07:31:50 AM
Trying to knock off all the mechanical jobs before I start re-wiring. Yesterday afternoon, and today's task was to sort out the mounting for the 'Gallows Bracket' - this is the davit affair that supports the cable going to the plasma torch, allowing it to reach the full gambit of the table.

When I bought it, the 25mm square tube it's made from was tack welded to a bracket that was tack welded to the main frame tube. I'd had to cut it off with an angle grinder to clear the door when I brought the table home, and had crudely bolted it back on as a temporary measure to use the table.

I decided to remove the tack welds and get the original bracket off the frame, and re-work it into a trunion allowing the gallows bracket to swing, and also be lifted out for transport. First I cut and bored a length of 30 mm bar with a 19 mm hole axially, then trimmed the original bracket and welded them together to form the trunion.

Then from the same 30 mm bar I turned one end down to 19 mm and made the other end 22.5 mm square using the 4th axis on the CNC mill. This allows the square to enter the tube and rest on a collar that I formed.

Then bolting the trunion back where it was removed from it was time for a trial fit - yes works fine.

Just needs a nice coat of blue paint - I'm slowly accumulating enough little bits to paint to make it worth while using a spray gun.
Title: Re: Titivating A CNC Plasma Table
Post by: DICKEYBIRD on December 10, 2016, 08:59:31 AM
Following along with you projects is always a learning experience Andrew.  Where else can us Americans get such a worldly education for free?  Along with the many tips & tricks contained in your threads, I learned a new word (titivate) in this one.  I also learned the term "Blue Peter".  Had to look that one up on Wikipedia.

I hope you enjoy creating these threads as much as I enjoy reading them! :beer:
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on December 10, 2016, 10:33:42 AM
Dickybird, thanks for the kind words. Glad someone is following   :clap:

Motivation for the threads is largely to keep a record of what I've done, and also sort my thoughts out as I'm updating things - surprising how often I'll go back over an old thread to look something up, and if people are enjoying them then that's another fillip  :thumbup:
Title: Re: Titivating A CNC Plasma Table
Post by: DICKEYBIRD on December 10, 2016, 11:28:20 AM
....if people are enjoying them then that's another fillip
There's another one! :clap:
Title: Re: Titivating A CNC Plasma Table
Post by: Pete W. on December 10, 2016, 02:44:14 PM
Dickybird, thanks for the kind words. Glad someone is following   :clap:

Motivation for the threads is largely to keep a record of what I've done, and also sort my thoughts out as I'm updating things - surprising how often I'll go back over an old thread to look something up, and if people are enjoying them then that's another fillip  :thumbup:

I've been following!  And enjoying!!   :D   :D   :D 
Title: Re: Titivating A CNC Plasma Table
Post by: millwright on December 10, 2016, 04:02:47 PM
Same here,   your glad someone is following Andrew? With nearly 2000 reads on this project I'm sure we all are as usual.
John
Title: Re: Titivating A CNC Plasma Table
Post by: Will_D on December 10, 2016, 04:10:20 PM
You are an inspiration to a retired old Welsh Git

Following closely!
Title: Re: Titivating A CNC Plasma Table
Post by: AdeV on December 10, 2016, 04:12:42 PM
 :wave: Me too!

Andrew, your posts are always informative and entertaining - and some of them are damn useful! OK, maybe not so much the flail mower (still a great thread & highly entertaining, but how many of us really need a mower that big...)

Now as for this project... well, I fancy making my own CNC plasma table from scratch, I'll need to make a solid holder for my existing plasma torch, so I can disconnect it for freehand use.... but this thread has already shown me loads of useful tips & tricks - like the curve supports for example, I'd never have thought of that one!

So, a big thumbs up from over here  :thumbup:
Title: Re: Titivating A CNC Plasma Table
Post by: kayzed1 on December 10, 2016, 04:27:06 PM
Me to, sitting here taking it all in and trying to keep a record in my head of all the tips and tricks.
Thank you Sir...
Lyn.
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on December 10, 2016, 06:11:58 PM
Don't make me blush chaps  :palm:

I'm just a retired old fart who enjoys tinkering in his barn and if I see a bit of engineering that I reckon I can do better I'm too big headed not to get stuck in  :lol:

However very happy to have you all along for the journey, it makes it all worthwhile  :thumbup:
Title: Re: Titivating A CNC Plasma Table
Post by: AdeV on December 11, 2016, 07:46:15 AM
Quote
I'm too big headed not to get stuck in

Nowt wrong with that! I mean, who did I think I was designing and making a dry sump for a highly-stressed race engine? Me, with no engineering credentials whatsoever....? IMHO belief is a big part of what we all do here, and having a large book of excuses to hand is a useful back-stop if it all goes wrong  :lol:
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on December 11, 2016, 09:47:24 AM
Ade, it was your dry sump thread that tempted me onto / into the forum  :clap:

So today's task - and so far it's gone pretty productively - is to work out how to mount the very powerful extractor fan. After all most of this re-build has been aimed at achieving 'down draught extraction' through the slats.

First issue - the rear cross member of the frame obstructs the line of the duct were it to go horizontal. I'd originally intended that the fan sat on the floor and was connected by flexy duct, and it would work fine like that, but I wanted to integrate the fan. (Mainly as it is going to be stopped and started under program control from Mach3).

So I decided to replace the cross member with one at a lower level, and also form a 'hanging cross member', and let the fan straddle the pair of them, with it's rubber anti-vibration feet sitting in 'cups' to stop it falling off.

The output from the duct that I had made will connect to the fan by a short length of 12" circular flexy ducting, and the exhaust from the fan will go outside via a yet to be made wall plate.

So before breakfast I had all the bits cut to size (oh I love my Pedrazzoli cold saw !) and then after porridge I set too gluing them all together with the MIG.
 
That all went pretty well, and left me time to give them a good degreasing and a blow over with Ford Tractor Blue. The 'Plasma Perch' and the trunnion got a coat at the same time, so now it's wait for the paint to dry time  :coffee:
Title: Re: Titivating A CNC Plasma Table
Post by: DICKEYBIRD on December 11, 2016, 10:11:41 AM
I KNEW IT!:doh:  Your plasma machine is called "Blue Peter" which is the super-secret military code name of the RAC's hyper-speed simulation tunnel for testing advanced top secret aircraft models.

Harrumph, down-draft  extractor fan my sweet grannie's arse!  Oh yeah, how's that new "tractor shed"  coming along? (Wink-wink, nudge-nudge)
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on December 11, 2016, 11:03:17 AM
 :lol:
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on December 12, 2016, 10:06:04 AM
The newly blue trunnion and 'plasma perch' and gallows bracket got returned to their rightful places and I set too fixing the new rear cross member and forward hanging support for the fan.

Then I cut out the original rear cross member - as expected the rear legs moved a bit and will need clamping when I fix the replacement.
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on December 12, 2016, 10:10:13 AM
Tywrapping the hanging support allowed me to determine the correct height for the new rear cross member, so when that was clamped up tight, I could then adjust the fore and aft position of the hanging fan support rail.

That done I had a trial fit of the fan to check that the measurements were correct, and all was well  :thumbup:

Then it was a case of drilling and tapping to permanently fit the rails in place. Getting the flexible trunking over the lip on the fan was a nightmare - it's just too tight - it's 'on-ish' but I'm not happy with it - looks like it needs a slightly fatter trunking.

Powering up the fan it caused a huge draught in the workshop which I stunk out holding a smoking paper roll over the table to track the down draught. It's excellent apart from the extreme corners, which is perhaps not surprising.

On the subject of the fan - it's making funny noises for all the world as though its speeding up then slowing down. The rating plate says 2,800 to 3,300 rpm which I'd assumed was for 50 or 60 hz but just maybe it's a universal motor with some sort of speed monitoring. Normally if you block a pump or fan it's load (slightly against instinct) decreases. This one draws more current (1.7 amps as opposed to 1.5 unblocked) and the speeding up / slowing down stops - odd. It claims to shift 65 cubic metres of air a minute, which is quite possible from the blast it produces  :bugeye:
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on December 13, 2016, 01:00:54 PM
Today has hopefully seen the last of he 'mechanical' side of things - I've been pondering how and where to mount the monitor and keyboard - it's not possible to put them on an adjacent wall, and really I want this table to be self contained and able to be moved about without too much hassle.

I obtained a wall mount monitor / keyboard swively thing which is not ideal but was a good starting point. Clamping some flat plate to the frame of the table I experimented with various positions trying to  find somewhere that would clear all the moving bits, and yet still swing out of the way allowing plates to be loaded onto the table.

Ended up with a reasonable compromise which suited 'stand up typing' so I went ahead and fabricated a weldment - really a darn great bracket
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on December 13, 2016, 01:07:02 PM
Now although this weldment is made from 6 mm plate I was expecting some tilt or twist, and sure enough there was a bit too much to tolerate. My fall back plan was to incorporate a 'torque tube' made from heavy 40 mm box welded on the back to resist the twist.

Worked well and made things very rigid. So it was a case of drilling mounting holes, clamping it in place and drilling and tapping the table frame.

Then of course the obligatory coat of Ford Tractor Blue to add a bit of bling - well in all honesty actually to slow the rust down   :clap:
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on December 14, 2016, 11:03:02 AM
This morning I attached the monitor bracket gizmo and cut a bit of melamine chip board as a keyboard / mouse table (hate the stuff but it was all I had to hand.

The table is looking more and more like an oil rig out of the water, with all sorts of things hanging off it  :lol:

... anyway this means no more procrastination, I need to get on with drawing up a wiring schedule of the current set up, so that when I pull it all apart and mount things in the new cabinet I stand some chance of getting it right  :bugeye:

It's not that complicated, but as the various settings are already up and running I want to keep things 'as is' rather than re-invent the wheel.

Over the next few days I will go through the rest of the original wiring documenting it and try and decide how to implement the limit switches he currently ignores (he's only wired one on X, one on Y, and one on Z and I suspect that only -Z is actually used by the software) and also how to build in an eStop in a sensible fashion.

First thing - try and identify the stepper motors. X, X-slave, and Y are all the same - "Astrosyn MY259RE" and quote 0.8 ohms 4.3 amps on the case - can't find details of them on the web but they seem to work. The Z stepper carries no markings what so ever  :bang:

So far I have traced the stepper motor wiring from each motor back to the appropriate AM882 driver in his box of tricks, and also traced out the limit switch wiring back to the break out board and drawn out tables as a record. Initially it puzzled me that X and X-slave were wired differently, then I realised, as they face each other they must rotate in opposite directions  :med:

It seems he has implemented all limit switches as normally closed, with the exception of Z- which is wired normally open, but held closed by gravity assisted by a spring, until the torch touches down for height setting purposes.

I've attach the tables but really only to keep a record, pretty boring for anyone else !
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on December 15, 2016, 11:09:36 AM
I  >>>THINK<<< I've completed documenting the existing wiring to the extent that I can pull it apart and start re-locating the various modules into their new places .... time only will tell if I've forgotten something  :bugeye:

Anyway the document has grown to 8 pages and I attach it here for reference, but it's pretty dry stuff  :med:

Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on December 16, 2016, 05:13:57 AM
So I've decided to rip out all the stepper motor and limit switch wiring from the table and re-run it, and that's today's job. The master plan is to re-wire, then temporarily hook up to the existing controller box to prove all OK before pulling the controller box to bits, thus cutting down on fault finding (hopefully)

Firstly some little things to overcome:

a/ Z-Down limit switch is only fixed by one screw and has no cover as everything is very inaccessible

b/ How to run the wiring from the (missing) X-Far limit switch as it's a long way from the 'power chain' ducts

c/ How to connect to the stepper motors as present chunky car type plugs and sockets are not acceptable

d/ Best position to move the power chains to for threading, as as soon as I start removing wires I can no longer move the carriage about  :bugeye:


Starting with the Z-Down limit switch, I decided that the best course of action was to carefully measure up and drill a pair of access holes, allowing a screw driver to access the M4 mounting screws. Having done that and removed the single screw currently fixing the switch it turns out he's not drilled or tapped the hole for the other screw  :bang:

Now M4 needs a 3.3 mm tapping drill, and a standard 3.3 jobber drill is far too short to reach the plate that needs drilling. It just so happens that when I was rebuilding my Dominion Super Elliot Woodworker I'd had the same problem and had made an extended 3.3 mm drill - result  :ddb:

But what about an M4 tap 100 mm long - well extend one ! Across the 'points' of the square shank of the tap I chose measured 3.85 mm, so I drilled a 3.7 mm hole in a bit of 6 mm mild steel rod and used the lathe to press the tap into the undersized hole - worked a charm and ensured that they are concentric - problem solved  :clap:

As for the X-Far limit wiring, having thought about drilling the frame and threading the wire through I've come to the conclusion that it might as well be Tywrapped.

The power chain issue I think is OK as one side has 'open fingers' to allow wires to enter

Now the stepper motor connections call for a neat little 4 way junction box that can be fixed to the body of the motor - not sourced any yet and would welcome suggestions
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on December 16, 2016, 08:14:05 AM
Right-ho, that's all the wiring off the table  :clap:

Cropped off the original ends at the stepper motors so that there can be no confusion which core is which on replacement, but unscrewed the limit switches individually. For some reason best known to himself the wires had been stripped for about 2 inches and wrapped round the terminals about 10 times  :bugeye: They will go back with crimped on 'boot lace ferrules' with about 6 mm sticking out !

Removing the cable from the gantry, I realised that he'd left the angle iron support in bare metal and it was already getting rusty, so another job - remove, clean and paint - which I did. It's fixed into the slotted extrusion of the gantry with Tee nuts of the type that you can put in and twist - handy, but he's spaced it down about 1/2" using a pile of 6 washers on each bolt - so it looks like I'm turning up eight spacers this afternoon !

Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on December 16, 2016, 10:04:52 AM
So after lunch an off cut of 19 mm hex aluminium was turned into eight spacers - much nicer to handle than a pile of washers !

Waiting for paint to dry - already touch dry but pushing my luck to mount the chain support until the morning. At the moment I'm thinking I'll just use crimps to couple the stepper motors - much rather use a small junction box but every thing on the market seems to be far too big. I'll try and leave enough cable in the system that I can re-terminate in the future if anything suitable turns up.

... so it looks like re-wiring can't start until tomorrow ...  :med:
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on December 17, 2016, 12:55:35 PM
Late on Friday afternoon I located some small clip together boxes on Toolstation - not ideal as they aren't sealed, but definitely functional. Ordered on line and they arrived first thing this morning - pretty good.

I re-fitted the 'power chain' support now the paint has dried.
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on December 17, 2016, 01:00:04 PM
So I was able to start the wiring - so far the four stepper motor cables are pulled through, as are the six limit switch cables. The motors and limit switches are all connected and the controller ends brought back to the cabinet in flexy conduit awaiting drilling the cabinet bottom plate - a job for tomorrow.

Another job tomorrow is to finish off securing cables with 'P Clips', and binding the various bundles with spiral wrap.
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on December 18, 2016, 08:24:43 AM
This morning I bored out the right hand base plate for the electrical enclosure to take the four 20 mm flexible conduits that take the motor and limit switch cables, and also holes for the two connectors that interface to the Hypertherm plasma cutter. While I was at it I put an extra 20 mm entry, blocked by a blind grommet, as a just in case provision as it's much easier to do it at this stage than later.

Then I mounted the base plate, attached the flexible conduits and was then able to dress them to their final position with tywraps. The tidying up of the wiring continued by applying 'spiral wrap' to the cable bundles to keep them neat and out of danger.

Finally I temporarily lashed up the motor drive cables to the AM882 driver modules to prove I'd not accidentally interposed wires somewhere - glad to say it all worked as it should  :ddb:

Initially I didn't bother with the limit switches (he'd only wired in three) - interestingly MACH3 wouldn't 'go to X0 Y0' which is a software point not a home position and currently is miles away from the limit switches. Then I realised that as they are normally closed, but not wired, MACH3 was seeing the table as on limits. Quickly lashing the three switches in and it homed to X=0 Y=0 just as it should.  :ddb:

Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on December 18, 2016, 10:42:27 AM
So to finish the cabinet / electrical enclosure I made up the left hand base panel - rectangular holes for clip in IEC plugs and sockets - I don't like cutting rectangular holes  :bugeye:

Anyway, a bit of chain drilling and hand filing and an acceptable result - that's one IEC inlet socket, linked to three outputs (PC, PC Monitor, and a spare) and one separate IEC outlet socket which will be relay controlled for the extraction fan.

Round socket is a 'feed through' CAT5E which is the only connection from the PC to this control. I like ROUND holes  :ddb:
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on December 19, 2016, 09:51:18 AM
Today's task: strip out all the modules from the original controller, and physically mount them on the cabinet back panel.

Rather than use nuts and bolts, as I want all modules to be removable from the front, I've drilled and tapped the cabinet panel with about 10 million M4 and M3 holes  :bugeye:

Took forever but if a module fails it'd be a pain to have to remove the entire panel to get it out, and the panel is 2 mm which is as thick as an M4 nut anyway.

Not started the wiring yet as that needs a fresh mind probably tomorrow, but I did do a trial fit - took a bit of jiggling, but it did go in nicely - be almost impossible without those handles.

The majority of the wiring will be done on the bench, with just final connection of inputs and output actually fixed in the cabinet.
Title: Re: Titivating A CNC Plasma Table
Post by: Homebrewer on December 19, 2016, 09:02:12 PM
Looking great so far! 

Sent from my SAMSUNG-SM-G900A using Tapatalk

Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on December 20, 2016, 04:28:06 PM
Thanks Libby  :thumbup:

I spent an anti-social day today locked away in the workshop doing an intense wiring session - very productive  :ddb:

A/ I've completed the AC mains wiring distribution

B/ I've completed the DC power supply wiring and distribution

C/ I've completed the wiring for the four AM882 motor drivers, from the ports on the BOB to the AM882 and onwards from the motor driver outputs to the X, X-slave, Y, and Z DIN terminals

(I've yet to decide how to lash the cables down that feed the AM882's - they look a mess as they are. A possible solution is to use 'sticky pad Tywrap saddles', but they tend to come unstuck over time. I may have some with provision for a screw.)

D/ I've cut the capping for the trunking

E/ I've added a further six DIN terminals for the Torch Height Controller (which I'd forgotten  :bugeye: )

F/ I've added the 12v DC driven contactor for the fan as it was delivered this afternoon

All in all a very productive day.

The DC power leads to the torch height controller originally passed through a ferrite ring - presumably to cut down on noise coming from the plasma arc. Not sure if it's needed, but I've incorporated it and hidden it inside the trunking !

Yet to complete:

A/ The Limit switch input wiring

B/ The Torch height wiring

C/ The Fan relay wiring

D/ The CAT5E ethernet cables to the interface and the torch height controller - they just plug in but I'll probably need to make custom lengths.

(Then of course there will be another big session fitting it in the cabinet and making off all the input and output cables )

Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on December 21, 2016, 07:15:06 AM
I'm glad to report that the panel is FINISHED - bar testing  :ddb:

All the above list has been done, and I added an extra way to the DIN input for the the mains, and re-located the fan contactor to make the wiring neater. Just needs fitting in the cabinet, and thirty eight cables making off, but that won't happen today as I have to socialise (apparently)
Title: Re: Titivating A CNC Plasma Table
Post by: mattinker on December 21, 2016, 07:50:12 AM
Hi Andrew, I imagine that it's too early for me to bring a lump of steel to cut out on tuesday!

Keep on titivating, all the best, Matthew
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on December 21, 2016, 04:28:22 PM
Hopefully not long now Matthew  :thumbup:

I managed to sneak out for a couple of hours this evening to get a bit more done.

Firstly I found that the 'one in three out' IEC input module wasn't as I'd assumed all connected in parallel, but the 'three out' were in parallel and separate from the input socket - soon cured with some soldered links.

Then I installed the panel in the cabinet and wired in the mains and sorted the main chassis earth.

Then I started on the input / output wiring and managed to get the four stepper motors coupled up. No time to test but good progress. More socialising tomorrow (our wedding anniversary so out to lunch with the wife, and a drinks and nibbles party later so limited time, but hopefully I can get some of the limit switches wired in.
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on December 22, 2016, 06:29:00 AM
A productive morning  :ddb:

First I installed the PC in it's mounting sleeve on the electrical enclosure and connected it to the panel electronics by it's Ethernet port - this allowed me to test the stepper motor wiring that I did yesterday, and amazingly everything worked as it should and turned in the right direction  :clap:

Then I wired up the limit switches - just repetitive making off of cables, teasing out the screen and using a bit of heat shrink to hold it all together (hot air guns are HOT - ask my right arm how I know   :bugeye: )

Testing the limit switches MACH3 immediately went into ESTOP - it turns out that 'Z-UP' input has been programmed for ESTOP - as a temporary measure I've disconnected it, and will probably long term wire 'Z-UP' and 'Z-DOWN'  limits in series. At least it shows me how I can implement ESTOP easily - I have the button, just not mounted it yet. (Previously he had only implemented Z-DOWN, X-NEAR, and Y-RIGHT)

This just leaves me a few things to sort - mainly the interface to the plasma cutter. The existing cables are in a dreadful state. The control cable (like many on the original machine) had no cable clamps fitted, and wires were pulled out and VERY dodgy. I've managed to source clamps from similar (but not identical) connectors so will re-make the entire cable. The connectors are crimped, and the pins in the shell at the Hypertherm end are not ones I've been able to source, however the ones at the table end seem to be identical to the ones used in 'D-Type' plugs and sockets for which I have the pins and crimps. I just hope extracting the existing pins doesn't destroy the shell.

The second cable from the Hypertherm carries the full 'Arc Voltage' - which can be as high as 250v, so I don't think the original use of car type 'bullet connectors' is a good idea  :bugeye: Searching high and low for a plug / socket arrangement that was suitably compact there is not much to choose from. I ended up with "Neutrik NAC3FCA" or possibly NAC3FCB. It seems one conventionally is used as a source and the other as a receiver, but they look very similar to me (I bought a pair of each to let me choose) I've never seen these connectors before, so if anyone else has experience please advise.

Another thing to sort is the PC Monitor support - again it's taken on a list to starboard - a bit of judicious bending is probably called for  :lol:

Title: Re: Titivating A CNC Plasma Table
Post by: mattinker on December 22, 2016, 09:18:50 AM
I wish there was a like button!!

See ya, Matthew
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on December 23, 2016, 09:51:47 AM
Today was a cable sorting day - my main concern being the control lead from the Torch Height Controller to the Hypertherm cutter. It had seen better days, no cable restraints in place at all, wires stretched - why do people let things get this bad  :scratch:

It needed shortening considerably, and I had to be able to rescue the Hypertherm end as I had no way of re-crimping new contacts in it. By cutting the cable shorter, cutting back the torn outer insulation at the connector end, and warming the wire under an electric hand drier I was able to encourage the sheath to move back down to the plug so that the new cable clamp would grip it  :ddb:

Then, moving to the Torch Height Control end I (having taken a reference picture first!) pushed out the female pins, and crimped new ones onto the shortened cable. Now pushing pins out is not always successful, as the plastic of the shell has to deform to allow the pin out, and this means that the new pins are not always retained properly. As I was dismantling it, one wire came out with no pushing, and a pin wouldn't retain in the hole - so someone has been here before  :bugeye: Luckily I'd had a delivery of gap filling superglue this very morning, and a tiny drop on the pin did the job  :ddb:

It was a case then of making up the chassis sockets for the Torch Height Controller and screwing them in place.
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on December 23, 2016, 10:08:49 AM
Now the Plasma Arc Voltage lead emerges from the Hypertherm 45 plasma cutter though a 1/2" hole with no cable restraint (common theme here  :bugeye:)

So I decided to pull the Hypertherm apart to see what could be done - turns out I'm going to have to buy a special cable gland as nothing that I have will fit. While in there having blown the dust out, I made a crude temporary restraint from a Tywrap and I must order up the right bit.

While I was at it I added a 90 degree elbow to the air feed to get the pipe pointing in the right direction when the Hypertherm 45 is sitting on the 'plasma perch'

This let me put everything back together, and theoretically everything is ready to work. There are a few little things I'd like to sort though before it returns to the welding shop:

a/ New castors - it's sitting on some I had on the shelf, but they are not locking, and the table moves with the inertia of the carriage - new locking ones arrived earlier in the week.

b/ I want to re-do the mains input to allow me to power up the PC without powering up the controller, so incorporating a three position switch (OFF, JUST PC, PC and CONTROL)

c/ Remake the belt covers - the ones on it are crude and rattle all over the place

d/ Fit an ESTOP switch
Title: Re: Titivating A CNC Plasma Table
Post by: vintageandclassicrepairs on December 26, 2016, 06:39:26 PM
Hi Andrew,
This project has gone way way past titivating  :bugeye:

May I add my 2 cents worth on the electrical panel build ?
My job used to be a spark/ inst tech (34yrs) and I have built innumerable panels for new projects and retrofits

Where mains voltage is involved,  :zap:
The panel door should be interlocked usually through an isolator with door mounted handle, so the panel door cannot be opened when the isolator is in the "on" position
A second option is a micro switch on the door operating a mains contactor rigged up to perform the same task

Regards
John
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on December 27, 2016, 03:14:45 AM
John, i agree in principal, and I have both an interlock and a cut out that I could fit, but probably won't. The control box will only open with the right key, and it is for my own use in a non-commercial environment.

As it happens I'm slightly revising the mains wiring today
Title: Re: Titivating A CNC Plasma Table
Post by: John Swift on December 27, 2016, 05:57:16 AM
Hi Andrew

the Neutrik power connectors can be seen on this mains distribution unit with the blue colour coded inlet
http://www.canford.co.uk/CANFORD-MDU7-AC-MAINS-POWER-DISTRIBUTION-UNIT-12x-Powercon-outlet-Powercon-inlet-with-Powercon-loop-out

they look a lot better than the "mains XLR connectors"  :zap:

     john

Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on December 27, 2016, 06:14:32 AM
John, I've assembled and fitted the blue series and must say that I'm quite impressed with them as a robust solution - went in nicely with no drama's and are very compact for their 20 amp rating - not that I'm using them to carry that - probably a few milliamps at most !

... so much better than the previous 12v bullet connectors  :bugeye:
Title: Re: Titivating A CNC Plasma Table
Post by: John Swift on December 27, 2016, 07:01:41 AM

Hi Andrew

I have always thought Neutrik connectors are worth the extra money

I don't know if you found the mains connector you have used have passing resemblance to the
speakon connector -

http://www.canford.co.uk/Products/43-081_NEUTRIK-SPEAKON-NL8FC-Cable-connector

they could be a useful   2 to 8 pole connector 

    John

PS

I can't wait to see your project for  2017   :D
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on December 31, 2016, 08:47:46 AM
Sorted a couple of little irritations this lunchtime.

I was fed up with the PC/Keyboard arm being on the slant - I'd intended to pull it off and give it a permanent 'set' in the press, but if I changed the monitor or keyboard (quite likely) the weight would differ and it again would tilt. I can up with the idea of making it adjustable, pressing a stainless steel hinge (that I happen to have left over from another project) into service to mount a tilting flap onto which the arm could fix. Then a simple screw adjuster would let me tilt it at whatever angle that I wanted to achieve a level keyboard and monitor. Works like a charm  :ddb:

I was away yesterday and last night, and came back to a pile of electrical goodies to re-arrange the mains input side of this machine, which is something for another day. But also in the pile was a packet of PG9 cable glands, so at last I've properly secured the 'arc voltage' cable where it comes out of the Hypertherm Powermax 45 plasma machine.
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on December 31, 2016, 10:52:40 AM

The panel door should be interlocked usually through an isolator with door mounted handle, so the panel door cannot be opened when the isolator is in the "on" position

Regards
John

John, your post got me thinking, and I've decided that to put in a cabinet isolator is not only sensible, but resolves other issues on my mains wiring revision, so although I had one in stock I've ordered one that's slightly smaller and hence more convenient for this cabinet and fitting it is the next job, so thanks for the prompt  :clap:
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on December 31, 2016, 02:27:45 PM
After super this evening, I fitted the electrical interlock that prevents the cabinet being opened when powered up. Not wired in, but that's the easy bit - getting the door actuator part and the inside switch part correctly aligned takes a bit of careful measurement. To be effective the interlock needs to be on the far side away from the hinges, or there would be too much leverage and it would easily be broken. Ideally it should be on the right hand side at the same height as the mechanical lock, but that wasn't possible, so it's in a compromise position which will be fine.
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on January 01, 2017, 07:58:52 AM
I pressed ahead and mounted the controls on the cabinet door this morning. I debated long and hard (with myself!) whether to put them on the side where wiring would be much easier, or whether to put them on the door, where the ergonomics are much better, but the wiring will be a pain (hinged door, so cables need to flex, and be supported across a door that I don't want to drill holes in)

It's always a bit of a worry drilling that first hole in things like this - spacing has to be EXACT so that the engraved label would fit, and all sit nice and square on the door. I cheated, and using the same file that I created the engraving and cutout holes from, I made a drilling template with 3 mm holes where the 22 mm cutouts would be. Drilled the first 3 mm hole and bolted it with a nut and bolt, squared the panel up with a set square, clamped it, drilled a second hole, another nut and bolt, then drilled the remaining four 3 mm holes. This done, I opened them up with a 'step drill' to 22 mm for the controls. Step drills are superb for this sort of operation, and the final hole is remarkably concentric with the pilot.
Title: Re: Titivating A CNC Plasma Table
Post by: vintageandclassicrepairs on January 01, 2017, 05:49:27 PM
Hi Andrew,

Quote
so thanks for the prompt
You are more than welcome
Maybe some adhesive backed slotted trunking and or spiral wrap and some sticky back cable tie thingys
across to the hinge side of the door ?
Neat job on the switch mountings :clap:
I have a few Greenlee hole punches that leave a nice clean edge, since my "real job" days
(like this)
http://www.ebay.co.uk/itm/Greenlee-Knockout-Punch-and-Die-Set-1-2-CONDUIT-7-8-I-D-PAT-1817223-/302163983305?hash=item465a607bc9:g:quoAAOSwiDFYNlJa

Happy New Year
John
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on January 02, 2017, 04:45:15 AM
Thanks John.

In the end I used Tywrap sticky pads across the cabinet door. Scrupulous cleaning with IPA first as I've had bad experiences with these things falling off in the past. I used to have problems with printed labels curling off until it dawned on me that many painted surfaces have been buffed with silicone containing polishes, and the thorough wipe down with IPA has cured that problem. Hopefully it'll do the same for the sticky pads  :med:

The wiring is now mostly completed, just awaiting the arrival of a relay for the E-STOP circuit to drop the power to the stepper drivers, but E-Stop into MACH3 is up and running, as is separate switching for the controller and PC along with the relevant indicator lamps.

Still need to sort out the extractor fan duct, and cut a 12" diameter hole in the right place in the welding shop wall for the exhaust and make a cowl for it. Also need to sort out the driving of the fan relay from MACH3 - the plan is to bring it on when cutting first starts, and turn off 10 seconds after cutting ceases.
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on January 02, 2017, 09:36:19 AM
Still waiting for the E-Stop relay, but I went ahead and finished off the door cable form.
Title: Re: Titivating A CNC Plasma Table
Post by: RobWilson on January 02, 2017, 12:15:48 PM
Very tidy wiring job Andrew.  :thumbup:

Rob.
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on January 03, 2017, 03:44:18 PM
Thanks Rob.

Today I attacked the problem of driving the extractor fan from the MACH-3 program with some help from folks on the MYCNCUK.COM forum - thread is here:

http://www.mycncuk.com/threads/10490-MACH3-Plasma-help-please

After a few blind alleys I found my way through the maze, and now can control the fan either by G codes or by an on screen button  :ddb:

To clebrate, I thought I'd have a go at tidying the 12" ducting on the fan. The basic issue is that the 'suck' end of the fan has a flare making it too large to comfortably slide the flexible ducting over. I'd intended to buy larger ducting, but it's mighty expensive, so I decided to roll up a sleeve to fit inside the flare thus presenting a parallel 12" pipe.

As the fan had a grille fixed with four clips I decided to re-use it and have the sleeve fixed by the same bolts. Worked out very well and makes a far neater job of the ducting  :clap:

Title: Re: Titivating A CNC Plasma Table
Post by: AdeV on January 03, 2017, 04:02:56 PM
Tidy job as usual Andrew, but, no JCB yellow paint? :scratch: :lol:

Quick unrelated question - what's that "green graph paper" desk cover thing you've got, and where does one obtain such a thing?
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on January 03, 2017, 04:36:25 PM
Thanks Ade - no yellow, but it does have Ford Tractor Blue appearing everywhere I've been  :lol:


Cutting mats abound in my usual department store (eBay  :clap:)

An example:

http://www.ebay.co.uk/itm/Babz-A3-30-X-450MM-NON-SLIP-CUT-CUTTING-MAT-BOARD-ART-CRAFT-Babz-Media-Ltd-/152381802475?hash=item237aa9c7eb:g:hfIAAOSw241YbBGn

Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on January 06, 2017, 08:03:20 AM
I've been twiddling my thumbs waiting for a relay to arrive to use for E-STOP. This gave me a bit of cogitation time, and I came to the conclusion that I just HAD to sort out the wonky belt covers that were installed.  :bugeye:

It's one of those things that don't need to be done, but as they are they look tacky  :(
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on January 06, 2017, 08:13:23 AM
Now looking to see how to mount more satisfactory covers opened a whole bag of worms  :bugeye:

It tuns out that the HIWIN rail sliders, which each mount with four screws, all have two screws missing, and more to the point, the holes drilled for them are in the wrong place  :bang: It's almost as though the gantry assembly was originally on a different sized rail with different sliders :med: Now all it needs is holes drilling in the mounting plate in the correct locations, but realistically this involves dismantling the gantry - something I don't really want to do  :scratch:

The HIWIN sliders have ports to mount grease nipples but none are fitted - not sure if they should be in this application - comments welcomed  :scratch:

And even worse when looking at the Z ballscrew lower bearing it is at a significant angle - certainly not mounted perpendicular to the shaft, but it turns smoothly - I can only assume it is a spherical self aligning jobby - I'll have to dismantle it and find out - looking upwards from the bed using a mirror, of the four mounting screws, three are missing  :bang: :bang:
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on January 06, 2017, 08:22:18 AM
All rather frustrating, as I'd thought that as soon as that relay arrives and is fitted, I can wack a 12" hole through the welding shop wall, and start using the table. In fact to speed up the process I ordered an exhaust cowl for the outside wall rather than bend one from Zintec, but now it looks like I have a bit more to do before that can happen.

So today the relay and cowl arrived, but I've still not worked out how I'm going to mount better covers. Having to remove the end plates of the gantry may well help, as I can possibly bend something up to fit round the profile of the end plates.

... ah well, onwards and upwards, at least I've fitted the E-STOP relay and wired it all up and it tests out OK.

Incidentally the OMRON relay that I thought I'd ordered turns out to be an ONROM relay - sneaky cunning naming intended to confuse I'm sure, OMRON are a well respected brand - never heard of ONROM - but it works OK
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on January 07, 2017, 02:41:15 PM
OK time to sort out the gantry issues - I started the day intending to draw up the shape of the end plate in cad to aid me in making an all embracing cover but it got so complicated missing all the bits that needed missing, and covering the bits that needed covering I changed track. I decided to make just belt covers, as the original owner had done, but this time with 'joined up corners' and not mounted at that odd jaunty angle.

The covers for all three axis are identical apart from the brackets, so I've bent up three boxes, and I will sweat brackets on to match the existing holes in the gantry.

To get reasonably sharp bends in the 1.2 mm Zintec sheet that I'm using, having laid it out and notched the corners I ran a 1 mm cutting disk lightly down the fold lines before bending in my Edwards Box and Pan folder. Then I soldered the corners using lead free solder, as it takes to the zinc coating nicely, and is significantly harder than plumbers lead containing solder.

The boxes came out pretty well and will get an obligatory coat of blue paint before being fitted.

Next job is to remove the end frames of the gantry and drill holes for the HiWin sliders in the right place - hole spacing on the end plates is 45 mm whereas the sliders are 40 mm - not sure how that happened, as I said before perhaps a different rail system has been used previously  :scratch:

I intend to remove the ends one at a time, replacing the one I've worked on before starting the next to stop the gantry getting out of control. To this end I've made up a wooden packing piece and wedge to secure the cross beam during the operation.

End plates come off tomorrow hopefully.
Title: Re: Titivating A CNC Plasma Table
Post by: hermetic on January 07, 2017, 03:30:22 PM
 at last! someone has found something that lead free solder is actually good for!, Thanks Andrew, I will remember that one. Can't wait for the demo video, she's nearly there!
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on January 07, 2017, 03:54:36 PM
You and me both Phil, this should have been done and dusted by now.

I found the usefulness of lead free solder with Zintec when I was making boxes and panels for the Traub lathe - funny how these things accumulate as 'handy fixes'

Title: Re: Titivating A CNC Plasma Table
Post by: Pete W. on January 07, 2017, 05:19:40 PM
Hi there, Andrew,

It's looking good!

Regarding the lead-free solder - did you use a gas torch or a smouldering iron?  And what flux did you use? 
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on January 07, 2017, 05:32:29 PM
Propane Gas torch Pete

For years I've had a blue bottle of butane and a torch on a length of tubing - if fact I've installed central heating with it in five houses! But I got fed up searching for a lighter and wanted a 'click to light' one.

I thought that I was being extravagant buying a "Rothenberger Super Fire 2" torch kit complete with a 'hot bag' to keep it all in but it has been amazingly useful in the workshop - ready to hand - instant lighting - focused flame - idea for soldering box corners  :lol:
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on January 08, 2017, 09:57:05 AM
This morning I bent up a pair of fixing brackets for the belt cover for the left hand side of the gantry, and sweated them onto the box. This allowed me to mark hole positions on the pinion swinging plate, to be drilled and tapped when it is removed.

Then with slight trepidation I started dismantling the left hand end of the gantry assembly. In practise it went quite well. I started by removing the stepper motor and limit switch and associated wiring, then releasing the spring tension on the pinion I was able to unbolt the rest of it and pull it apart.

Having the main bracket plate off allowed me to mount it up on the milling machine, pick up the location of the holes that were being used, and with that as a reference place correctly located ( 40 mm away) holes so all fixings on the HiWin sliders can be used. As the incorrect holes were at 45 mm spacing, inevitably I had to form a slot rather than a hole.

After a quick check that the new holes were in the right place, it was a case of cleaning up a couple of nasty welds and re-making them, a good rub down and a coat of Ford Tractor Blue.

All together quite productive, but I will have to repeat all this on the other side when I've re-assembled what I've done today, but that will have to wait for the paint to dry. Very glad I made up that wooden gantry support - it made the job much easier  :thumbup:
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on January 09, 2017, 11:00:55 AM
OK paint dry enough to handle, so I've re-assembled the left hand gantry end.

The T5 timing belt is unbelievably tight even at the slackest adjustment, and is showing signs of fatigue - it's 5/8" wide 5 tooth per inch and every time I count the teeth I get 71 which seems an unusual number to choose. I'll replace it (them) with a 72 or even 73 tooth to get the adjustment in the centre of it's travel.

Then it was a case of 'rinse and repeat' - I've stripped the right hand gantry assembly, relocated the holes, cleaned it up and given it a coat of paint which will hopefully dry overnight.
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on January 09, 2017, 11:51:42 AM
It seems that these belts are metric specification 5 mm pitch 16 mm wide with 71 teeth and a "T5-355" which gives the belt length. I've ordered three "T5-365" which have 73 teeth so hopefully will put the adjustment about right.

All three original belts (X, X-Slave and Y) are the same, have the same over tension issue and are showing signs of distress  :bugeye:
Title: Re: Titivating A CNC Plasma Table
Post by: mattinker on January 09, 2017, 11:54:05 AM
Andrew, 71 teeth for regular wear? If it's not to long, a 73 rather than a 72 tooth.

Just got back, haven't unloaded the saw yet!

All the best, Matthew
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on January 09, 2017, 12:15:45 PM
Glad you are safely back Matthew. It seems 73 is the next standard size so that's what I've ordered
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on January 10, 2017, 06:48:10 AM
I re-assembled the right hand end of the gantry and tested it - all ok.

As I've gone so far, I'll try and pull off the Y drive and clean it up and give it a coat of paint this afternoon - it's box cover is already done.

Then I need to sort out what's causing the lower bearing for the Z ball screw to tilt at such an alarming angle  :bugeye:
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on January 10, 2017, 09:51:55 AM
So fortified by a spot of lunch (Pilchards in mustard sauce on lightly buttered toast - yum  :thumbup:) I cracked on and started dis-assembling the Y stepper motor mount. This is very integral with the Z slide, so all came off and were dismantled, cleaned, the odd weld splatter ground back, and - you guessed it - yet more Ford Tractor Blue paint.

Hence there is now yet another box of odd shaped bits to re-assemble tomorrow when the paint can be handled. I've decided to leave the peculiar alignment issue with the Z ball screw until I put the Y stepper mount back. There were shims tilting the slide mount, and I think perhaps we've got compensating errors somewhere. I will re-build it as though starting from scratch - it's only a case of getting the torch held reasonably perpendicular and the Z slide also moving perpendicular - how hard can it be  :scratch: (famous last words  :ddb: )

There is a 'mini slide' on a short length of HiWin rail that is used to touch down, operate the Z-Down limit, and hence find where the top of the piece being cut is. Dismantling the mount I jolly nearly had the slider off the rails, which I assume would shed ball bearings in every direction :bugeye: The eagle eyed amongst you will notice some brown electrical tape wrapped round it to prevent a repeat performance.
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on January 10, 2017, 10:41:18 AM
"Scope Creep" -  uncontrolled changes or continuous growth in a project's scope. This can occur when the scope of a project is not properly defined, documented, or controlled. It is generally considered harmful.


Well it obviously happened on this project - I've just found myself ordering six 6003-2RS bearings - the assembly that holds the  gear wheels that engage with the racks on the machine each have two of these bearings - and at least one set feels notchy. Easy enough to change, silly not to really, but ...........  :scratch:
Title: Re: Titivating A CNC Plasma Table
Post by: hermetic on January 10, 2017, 04:17:47 PM
 Scope creep be damned, do it once, do it right, never have to do it again! (at least thats the theory!) Cracking job Andrew, absolutely no point in leaving notchy bearings in a project.
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on January 11, 2017, 04:31:24 AM
Well things might just get a bit delayed this morning. I was walking across our field coming back from taking the dogs for an early walk when I spotted one of the Ewes on her own with two large black crows next to her. Getting closer I realised that those 'crows' were black lambs that had just been born  :bugeye:

Now the ewes aren't due to lamb until late March / early April, and this particular Ewe, a Dorset Down, certainly shouldn't be producing black lambs having been tupped by a Hampshire Down which should produce white(ish) lambs. So I reckon that there's been early hanky panky involving the Jacobs ram  :scratch:
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on January 11, 2017, 10:09:29 AM
I managed to get it all back together between sheepy things - sorry only one picture. The Z axis ballscrew lower bearing assembly, that was on a cant was squiffy for several reasons:

a/ The vertical plate that it mounts on was bent where it mounts

b/ The mounting surface of the bearing assembly wasn't at right angles to the axis of the bearing

c/ The (knackered) bearing was squiffed in the bore that it fits.

I reckon that it has had a significant crash at some time, that bent the plate and mangled the bearing (which is a 6000-2RS)

I re-machined the mounting face of the bearing assembly, bent the vertical plate as best as I could with a rubber hammer and much violence, and replaced the bearing. As it happened I had a 6000 bearing (26 mm o/d 10 mm i/d) with metal shields which should be fine.

(NB Ewe and Lambs doing fine. Mum is eating well and offspring are both up and suckling  :thumbup: )
Title: Re: Titivating A CNC Plasma Table
Post by: Pete W. on January 11, 2017, 12:44:24 PM
Hi there, Andrew,

When I saw the photo of that ewe in your earlier post, I thought to myself 'That ewe's got ATTITUDE'!   :lol:   :lol:   :lol: 
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on January 11, 2017, 01:20:43 PM
She's saying 'watch it mate - I'll protect my lambs whatever comes at them' mean while in the back ground I'm trying to stop the dogs eating the afterbirth  :bugeye:
Title: Re: Titivating A CNC Plasma Table
Post by: nrml on January 11, 2017, 02:38:37 PM
Couldn't you have put the vertical plate in your hydraulic press? It did an outstanding job on the flaps of your flail mower. Yet another amazing rebuild. Thanks for taking us along on the journey.
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on January 11, 2017, 03:20:22 PM
I was being lazy and didn't want to dismantle all the gubbins on the plate
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on January 12, 2017, 04:47:28 AM
The six 6003-2RS bearings arrived this morning by post. No point in fitting them yet as the belts aren't here yet and it's much the same dismantling to change either.

Belts promised for tomorrow, but as it's Friday the 13th who knows what might happen  :med:
Title: Re: Titivating A CNC Plasma Table
Post by: mattinker on January 12, 2017, 05:52:10 AM
Andrew,
I wish there was a like button! I follow your posts with pleasure!

All the best, Matthew
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on January 13, 2017, 01:02:37 PM
Thanks Matthew, good to have you along  :thumbup:

The new slightly longer belts arrived late this afternoon. I only had time to fit the Y drive.

First I pulled off the T5 pulley and the pinion bearing assembly and rebuilt it with new bearings, then it was just a case of putting it all back together and adjusting the belt tension. Previously the belt had been 'murder tight' even with the adjustment at it's slackest. At least now I can adjust the tension as I want it.

So that's Y done, just X and X-slave to do when time permits
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on January 16, 2017, 06:55:38 AM
Having replaced the other sets of bearings and belts it's now time to return the plasma table to the welding shop.

Now it came in quite cheerfully on the fork lift, but someone's added bits and bobs all over the place making it neigh on impossible to get the forks anywhere useful. The welding shop is down one concrete ramp across a yard of coarse road planings and up another concrete ramp, so not feasible just to roll it on it's castors. However there is an 18 inch step between the two ramps - if I could pick up the table on strops with the JCB 803 and gently lower it on the lower side of the step I'd be virtually there  :ddb:

Now rigging this beast is not straightforward - the only realistic places for strops are the four corner pillars, and because of the electrical enclosure the balance would be wrong - however it has the advantage that the strops would miss the gantry which is a bit delicate  :thumbup:

So, four strops duly fastened, then joined to a fifth linking strop and the JCB advanced into position. Sure enough it's hanging down as expected on the cabinet corner but the gantry is clear. I gingerly drove forwards having raised the boom a bit, and lowered the table onto the top of the welding shop ramp.

At this point the castor on the lower corner decided to collapse  :bang: It not only was taking the full table weight but probably a bit of inertia load as I came down. Rubber hammer was applied to get it roughly in line and I managed to roll the table safely into the shop.

Then a quick call to roadside assistance produced my 10 ton railway jack and I was able to replace the castor temporarily with one of the non rotating non locking ones that I'd taken off - I'll have to try and source a proper one when the dust settles.

Rebuilding the PC, the PC monitor table and Hypertherm cutter along with the swinging gallows bracket, all of which I'd removed for the journey, put it back in a state that I could test for any damage. I'm pleased to say it all still seems to work.

I just need to cut a 12" diameter hole in the workshop wall, and I can then test it in earnest actually cutting  :ddb:

This of course has released my 'project space' for more fun and games
Title: Re: Titivating A CNC Plasma Table
Post by: Spurry on January 16, 2017, 07:29:17 AM
Luvverly job Andrew.  :thumbup: So, just the hole in the wall to do. Are you going to get the boys who did the Hatton Garden job along to assist?  :bugeye:
Pete
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on January 16, 2017, 07:47:25 AM
It's only single skin 100 mm concrete blocks so I reckon they'd be over kill  :lol:

Current idea is to chain drill with my 50 mm diamond core drill, hopefully from both sides to avoid breakout. I do have 110 mm and 125 mm diamond tipped core drills, but the smaller diameter hopefully gets me nearer the circle that I want.
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on January 17, 2017, 07:43:23 AM
This morning I attacked the wall.

I'd thought long and hard the best way to space 2" diameter core drilled holes reasonably accurately to give a 12" 'wobbly edged' hole, and in the end I came up with the patented angular hole spacer. Simply a bit of wood with two holes spaced 5" apart, one being 2" from an edge. One hole was used as a pivot, on a screw in the centre of the hole, and the other was a guide for a masonry drill. Drill one hole, then rotate the spacer so that the edge of the gizmo lines up with the last hole, and drill another. Worked like a charm  :ddb:

I then drilled these hole out to the guide drill size for the diamond core drill, and drilled out the core - it went remarkably easily, with the expected conical break out on the far side.

Then it was just a case of fixing the inner wall plate and outer cowl, and connecting up the 12" heat resisting flexible air pipe to the extractor fan on the table.

Hopefully this afternoon I'll get a chance to use the table in earnest

Title: Re: Titivating A CNC Plasma Table
Post by: PekkaNF on January 17, 2017, 09:00:20 AM
"Scope Creep" -  uncontrolled changes or continuous growth in a project's scope. This can occur when the scope of a project is not properly defined, documented, or controlled. It is generally considered harmful.


Well it obviously happened on this project - I've just found myself ordering six 6003-2RS bearings - the assembly that holds the  gear wheels that engage with the racks on the machine each have two of these bearings - and at least one set feels notchy. Easy enough to change, silly not to really, but ...........  :scratch:

Luckily you haven't got feature creep!
https://youtu.be/aXQ2lO3ieBA

That happens to me at the end of design phase and then I need to weed extras out.

Pekka
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on January 17, 2017, 11:10:20 AM
Well oddities abound - all excited I loaded up a sheet of 3 mm mild steel (zintec coated) and set it to cut out a 'bearing baffle' that I'd previously designed and cut on the table before I started updating it. It started off ok, measuring Z=0 and setting torch height, but when the actual plasma should have been initiated, movement stopped and the Hypertherm 45 displayed an error light showing 'loose consumables'

In the guts of the machine torch is a micro-switch that closes when the consumables are tightened onto the torch - I buzzed out the cables to the plug and everything was fine - closed when tight - open circuit when loose. Nothing to do with the CNC controller, this must be an internal issue with the Hypertherm - maybe something I disturbed when I remade the plasma voltage cable :scratch: . So I pulled the torch and cutter off the table, opened up the Hypertherm, and buzzed the switch all the way through to the main board - no issues. Put it back together and back on the CNC table, and tried again - same issue  :bang:

There is a button on the screen allowing me to trigger the torch on and off manually. Out of curiosity I clicked it, and initially there was a very weak release of compressed air - I did this several times then the torch fired up, no errors and full air discharge. I've come to the conclusion that the air solenoid in the Hypertherm was perhaps sticky and has now cleared, but why that should make it report loose consumables is a mystery  :scratch:

After that everything worked as it should - very odd. So here is a video of it cutting, and a picture of the result. Not surprisingly the cut quality hasn't improved since I did the re-build, but that's due to worn consumables and non-optimal cutting conditions controlled by program. Also there is an issue with the cut not ceasing fast enough at the end of a feature - I need to tweak the post processor to stop the arc marginally before the end of the feature to eliminate the nick it's producing.


http://www.youtube.com/watch?v=NMHk7ua96l8

Title: Re: Titivating A CNC Plasma Table
Post by: hermetic on January 17, 2017, 12:14:18 PM
Excellent work Andrew, teething problems, you will soon sort them and have it humming! I could just do with it to cut a 24" circle in 1.5 galv , when can you deliver it to Yorkshire?
Phil.
Title: Re: Titivating A CNC Plasma Table
Post by: DMIOM on January 17, 2017, 12:34:49 PM
Bravo Sir - good to follow proper refurb and see it working.

....I've come to the conclusion that the air solenoid in the Hypertherm was perhaps sticky and has now cleared, but why that should make it report loose consumables is a mystery.....

Well, the air is a sort of consumable isn't it?  :coffee:

What you found does remind me of the travails I had when I got my first machine with TNC155 - it would NOT start as the E-Stop was triggered. No matter what I traced and belled out I could not find the problem - axis final limit switches were all closed, E-Stop button wasn't activated.  Eventually found that the float switch in the Bijur auto-oiler was wired in series with the E-Stop  :bang:

Thanks for taking us along on another well-told adventure.

Dave
Title: Re: Titivating A CNC Plasma Table
Post by: RobWilson on January 17, 2017, 01:27:05 PM
 :thumbup: Nicely done Andrew  :clap: :clap: :clap:


I wish I had the room for one  :(


Rob
Title: Re: Titivating A CNC Plasma Table
Post by: howsitwork? on January 19, 2017, 01:05:52 PM
Looks good Andrew

Was the bucket outside in case you"felt a bit pale when you'd finished" :lol: :lol: :lol:

Ian
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on January 19, 2017, 02:10:14 PM
Bucket was carrying away the spoil from knocking the 12" hole in the wall.

Been playing today trying to improve cut quality. If you can imagine the plasma flame being shaped like the picture below, the correct height setting of the plasma torch dictates the edge shape of the cut. It will always have curve, but you want it to be symmetrically placed about the depth of the plate.

To achieve this you need to know precisely where you are in the Z axis. Now this plasma cutter like many others, has a "floating Z axis slide" where by the Z axis can be slowly ramped onto the work by a probing cycle, the main axis carrying on travelling and the floating one stopping (as the torch has touched the work), until the Z axis limit switch is tripped, whereupon the controller raises Z by the switch and slide backlash amount and the Z axis is now on a true Z=0 position. This value is input to the software for accurate positioning. Measurement this evening implies mine is 2.5 mm or there abouts, however it was set up to 2.0 mm in software.  Meaning that any Z positioning commands would be out by 0.5 mm. Yet to repeat this a few times to get a good average value to work with.
Title: Re: Titivating A CNC Plasma Table
Post by: mattinker on January 19, 2017, 02:29:37 PM
How's the extraction?

Regards, Matthew
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on January 19, 2017, 02:35:27 PM
A major improvement Matthew  :thumbup:

No longer does the welding shop fill up with a noxious fumes. Not sure about that pile of bodies accumulating outside though  :lol:
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on January 22, 2017, 05:24:09 AM
I'm loving this plasma cutter  :ddb:

This mornings exercise - try it out on 1.2 mm Zintec mild steel. I'd done a little trial yesterday to optimise cut speed, and this morning the idea was to make a little simple box.

- Draw it in Autocad - save as a DXF file

- Import into SheetCAM and produce a G code TAP file

- Import into Mach3 and make a flat box !

- Bend it on the Edwards Box & Pan folder

Absolutely straight forwards - it took less than an hour including taking the pictures and writing up this thread - magnificent - and no laying out bend lines, or having to make corner notches that go squiffy

--- I love it  :clap: :clap:
Title: Re: Titivating A CNC Plasma Table
Post by: mattinker on January 22, 2017, 06:37:53 AM
Andrew, you got the over cutting problem sorted! The 29mm hole can't be far away!

All the best, Matthew
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on January 22, 2017, 06:50:51 AM
Matthew, I'll cut you a range of holes and you can keep them in stock for when you need them  :lol:
Title: Re: Titivating A CNC Plasma Table
Post by: mattinker on January 22, 2017, 06:54:37 AM
Just hang 'em on a sky hook for me and I'll pick them up next year!!
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on January 23, 2017, 09:23:28 AM
So what's all this box making all about  :scratch:

Well I decided that although bits nicely drop into the collection area at the bottom of the down drought extractor 'funnel', it would be much easier if there was a removable 'ash pan' in there that could come out for cleaning etc.

Ideally it would be the same size as the bottom of the drop box, but in reality it has to be able to pass through the door opening. In my enthusiasm to get it as tight as possible my first attempt ended up about 3 mm too big  :bang:

Never mind - it takes 65.06 seconds (according to sheetCAM !) to cut another slightly smaller one - I'm sure that the bigger box will come in handy for storing things  :lol:

I spot welded the fold tabs as I think it is neater than pop rivets. If too much falls at the periphery and hence misses the box, I can always fix deflectors further up the drop box.
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on January 31, 2017, 03:22:58 PM
Oh this Plasma Table is GREAT fun  :clap:

I've been trying to learn Inkscape, which is a very versatile but not very intuitive graphics program that let's me grab images, trace and manipulate them and do things with text that are difficult in other programs.

Here are a few things I've done recently - firstly a sign for the farm (*), then some name stencils to entertain grand children who are invading at the weekend  :bugeye:

(* sorry the pig is skewered by a red screw driver, I couldn't find anything else to hang it on ! )
Title: Re: Titivating A CNC Plasma Table
Post by: mattinker on January 31, 2017, 04:34:37 PM
Nice to see! The weather's got warmer, so the welding shed is accessible again. Your having fun! A 29mm hole soon?

All the best Matthew

P.S. Progress on the Warco, slow, but progress!!
Title: Re: Titivating A CNC Plasma Table
Post by: Pete W. on February 01, 2017, 05:21:33 AM
Hi there, Andrew,

I can understand your pleasure at the new capability afforded by the plasma table.

Reading your mention of Inkscape reminded me of a post (here or elsewhere, I forget which) from someone who was trying to identify the font used in someone's logo so he could make a replica ID plate.  Sounds like Inkscape would be just the tool for that job. 
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on February 01, 2017, 07:55:40 AM
Pete I think it was ME  :lol:

I was trying to replicate the FANUC logo for replacement reels for my wire eroder !


http://madmodder.net/index.php/topic,10211.msg115074.html#msg115074


With my new found knowledge of INKSCAPE it would be a doddle !!!!
Title: Re: Titivating A CNC Plasma Table
Post by: Pete W. on February 01, 2017, 10:28:30 AM
Pete I think it was ME  :lol:

I was trying to replicate the FANUC logo for replacement reels for my wire eroder !


http://madmodder.net/index.php/topic,10211.msg115074.html#msg115074


With my new found knowledge of INKSCAPE it would be a doddle !!!!


OK, you get off with a light sentence for handing yourself in and pleading guilty!!   :lol:   :ddb:   :lol:   :ddb: 

And we'll also take into consideration your record of community service!!   :D   :D   :D   :D   :D   :D   
Title: Re: Titivating A CNC Plasma Table
Post by: PekkaNF on February 03, 2017, 05:39:23 AM
Way past titivating...

Now, produce some mamaliars
http://c8.alamy.com/comp/DXJXY6/monty-python-and-the-meaning-of-life-br1983-graham-chapman-DXJXY6.jpg

Pekka
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on February 03, 2017, 06:16:38 AM
 :lol:

.... happens down the farm all the time  :ddb: :ddb: :ddb:
Title: Re: Titivating A CNC Plasma Table
Post by: PekkaNF on February 03, 2017, 06:25:10 AM
Once my wife said that she is pretty sure I would not mind that punishment from famous BR movie.

Pekka
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on March 19, 2017, 03:57:50 PM
Since I first got this machine I've not been overly happy with the Z Axis. It's main mounting plate had been bent at one time, and both the normal Z movement and also the 'floating Z Axis' used for material sensing only ran on single  linear rails, resulting in a bit of side to side wobble and tilt. Don't get me wrong - it works - but it's not overly robust in it's design and there were features that I wanted to incorporate - namely:

A/ Dual parallel rails for the main Z and the floating Z movements

B/ A Magnetic Breakaway Torch Mount

C/ Emergency Stop to be asserted if the Magnetic Breakaway is triggered

Now this is all very well, but I didn't want to strip down the existing Z axis and hence stop me using the machine, while building the new one. So I decided to start from scratch and make a modular Z axis that would be on plugs and sockets and fit existing mounts on the machine.

I procrastinated for a long time, looking at economical ways of getting the linear ways, ball screw and nut, bearings etc until eventually a 'Prototype Z Axis' turned up on eBay. It had been put together but obviously never used, and would need re-making, but it had the linear rails, ball screw and nut, bearings, stepper etc just as I wanted, but for far less than the total of buying the separate items  :clap:

Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on March 19, 2017, 04:05:57 PM
The end mounting plates will need re-making to spread the rails further to suite the existing machine mounts, the coupling between the stepper motor and ball screw was rigid, and I'll have to mount a new floating Z axis on it with suitable magnetic breakaway torch holder and limit switches.

So - buy an Oldham coupling and bore it to the correct sizes - simple (and done  :ddb:)

Draw up a CAD drawing to show how all the components potentially interfere with each other, to make sure that the new upper and lower plates will work - done  :ddb:

Buy a handful of limit switches - done  :ddb:

Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on March 19, 2017, 04:12:00 PM
Buy a big slab of 10 mm thick aluminium alloy ground tooling plate to make the bits - done  :ddb:

Source a (VASTLY EXPENSIVE  :bugeye: ) Magnetic Breakaway Torch Holder - done and customs duties paid  :ddb:

(I had intended to make my own, and even drew it out in CAD and bought the magnets, then I realised that the 'real ones' had been carefully developed to hold on in normal situations, and let got if the torch catches the plate and the amount of magnetic force needed was a great imponderable, and with torches about 600 each I didn't want to carry out tests !)
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on March 19, 2017, 04:21:35 PM
Source some smaller THK-10RM rails and sliders for the floating Z - done but will need cutting in half  :ddb:

So now it is a case of making the end plates - (simple but need doing accurately) so I extracted them as individual parts from the CAD montages and will probably CNC machine them.

Still quite a few details to work out re the floating Z and limit switch mounting, but I'll get the end plates made so I have something to prod and poke !
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on March 19, 2017, 04:23:18 PM
Incidentally, the pre-existing mounting slots that I previously referred to are these:

Title: Re: Titivating A CNC Plasma Table
Post by: philf on March 19, 2017, 05:46:36 PM

So - buy an Oldham coupling and bore it to the correct sizes - simple (and done).


Andrew,

I'm not usually a pedant but that coupling is a Lovejoy type coupling and not an Oldham!

An Oldham coupling wouldn't work in that application because they have no lateral stiffness and would need a bearing to support the screw.

http://www.oepcouplings.com/assets/ocanimationsmall.gif (http://www.oepcouplings.com/assets/ocanimationsmall.gif)

The Lovejoy type couplings allow angular misalignment only and no (or very little) axial misalignment.

Cheers.

Phil.
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on March 19, 2017, 05:53:06 PM
I bow to your knowledge Phil  :bow:


The vendor referred to it as a Plum coupling  :scratch:
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on March 20, 2017, 06:19:06 AM
Well the upper and lower plates are 'VIRTUALLY' done but no time yet for the real things, also need to resolve the usual fixturing issues  :scratch:

(I marginally altered these from the CAD drawing above, reducing them to 145 x 68 to take a bit of weight out of the assembly and also give a bigger  'waste' for the milling, as the source plate is only rough sawn at a nominal 150 mm wide.)
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on March 21, 2017, 11:58:42 AM
I got time today to finish the upper and lower plates for the Z axis.

Each was a two stage process - boring and drilling the holes, then making a profiling fixture and profiling their periphery giving the corners a 3 mm radius.
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on March 21, 2017, 12:00:24 PM
This has allowed me to get to 'first trial assembly' so that I can better decide what layout to use for the travelling stage that mounts the 'floating Z axis' and the actual torch holder
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on March 23, 2017, 10:16:29 AM
A bit tied up this morning collecting and distributing 'self assembly lamb kits' (ready for the freezer) but I did manage to do a bit of drawing up the 'front plate' that will hold the 'floating Z axis slider'.

This is a bit of reserved design, in that I am undecided on exactly how I will locate both the HSR-15 sliders and the ball nut location, so each have three alternative positions - being CAD then CAM it's as easy to let the machine do all three alternatives and I can pick and match as it evolves - then if I'm REALLY keen I'll make another with just the selected holes in it.

Meanwhile the plate will look like a bit of Emmental cheese  :lol:
Title: Re: Titivating A CNC Plasma Table
Post by: AdeV on March 23, 2017, 11:44:39 AM
What you need is a lump of plastic-like material which can be machined very quickly and easily in order to prototype the finished article. You know, something that doesn't cost a fortune, and doesn't break cutters if you get a tool-crash, and who's chips can be melted down and reformed into new blocks.... 

:lol:
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on March 23, 2017, 03:00:42 PM
 :lol: :lol: :lol:

Got a cupboard full of machinable wax Ade  :ddb:

Not really applicable here though - it would break  :(
Title: Re: Titivating A CNC Plasma Table
Post by: AdeV on March 23, 2017, 04:43:46 PM
Got a cupboard full of machinable wax Ade  :ddb:

You might very well think that, I couldn't possibly comment!  :palm:

Actually, you'd be surprised how thin you can go and have it hold together; but yes, one overtightened bolt and before you know it you've got a pile of bits all over the floor....
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on March 23, 2017, 04:55:08 PM
... No I really DO have a cupboard full of the stuff Ade, but now we know that you do as well   :clap:
Title: Re: Titivating A CNC Plasma Table
Post by: RodW on March 26, 2017, 04:32:27 AM
I am undecided on exactly how I will locate both the HSR-15 sliders and the ball nut location,

I don't know if this will help you, but this is how I made my floating head Z axis using HGR15 rails.

(http://i210.photobucket.com/albums/bb270/rodweb/Lathe/Plasma/DSC_7240_zpsxuyfurob.jpg)

This is the floating head
(http://i210.photobucket.com/albums/bb270/rodweb/Lathe/Plasma/DSC_7230_zpsetahm9yj.jpg)
I've added an adjustment screw on the other side so I can keep the switch movement before triggering the sensor to an absolute minimum. Its just a countersunk screw with a lock nut to keep the plates apart. One day, I'll replace it with a nice knurled knob...

I know how you feel working out the design. What I finally built was probably about version 87!

I've got everything built except the table but its all cut up and ready to weld.
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on March 30, 2017, 05:47:16 AM
Thanks Rod.

At long last I've found a bit of time to go from a rendered model of the front plate to making a physical prototype. This will allow me to develop the Floating Z bit, and finally decide on which alternative mounting positions to use for the rail slides and the ball nut mount.

Fairly obviously the final version needs to be a tad wider to accommodate the counter bores for the M4 cap screws fixing the rail sliders, but with this mounted I can develop my ideas a bit further
Title: Re: Titivating A CNC Plasma Table
Post by: PekkaNF on March 30, 2017, 06:01:07 AM
Thanks Rod.

At long last I've found a bit of time to go from a rendered model of the front plate to making a physical prototype. This will allow me to develop the Floating Z bit, and finally decide on which alternative mounting positions to use for the rail slides and the ball nut mount.

Fairly obviously the final version needs to be a tad wider to accommodate the counter bores for the M4 cap screws fixing the rail sliders, but with this mounted I can develop my ideas a bit further

Nah, just open then couterbore out with a slot drill, mechanically it will fine and look the part.

Out of curiosity....the "floating" feature is arranged with stepper motor control? Like Z-is sent from program and then there is a whizbox that superimposes torch control over that setpoint and drives the stepper?

Pekka
Title: Re: Titivating A CNC Plasma Table
Post by: RodW on March 30, 2017, 06:24:50 AM

Out of curiosity....the "floating" feature is arranged with stepper motor control? Like Z-is sent from program and then there is a whizbox that superimposes torch control over that setpoint and drives the stepper?

Pekka

Plasma is a bit of a funny animal when it comes to CNC. The floating head is to find the surface of the material when initially piercing. The torch basically hangs on a section that can slide up when the torch head hits the material. This triggers a float switch (proximity sensor in my example above).  So the torch then moves up to adjust for switch hysteresis and the material height is recorded. The torch then retracts to pierce height (say around 3-5mm) and turns on. The plasma machine sends a signal back to say the Arc has been established (ArcOK) and then the controller counts down for a pierce delay. After that, the Torch moves down to cutting height (say around 1.5mm) and then off it goes on its merry path to cut your part.

The problem then is that material is not dead flat and thin material can warp from the heat so most modern CNC Plasma controls measure the torch arc voltage as there is a linear relationship between cut height and arc voltage (voltage increases with Torch height). The controller then controls the Z axis height to keep the voltage at the desired level.

There are several other methods to sense the material. Ohmic sensing simply uses the material and the torch tip as an electrical switch (without the 300 volt arc frying your electronics).  Others monitor Z axis torque (or current) so that when it starts to stall as its driven into the material, the material height is recorded.

So in summary, the plasma table is simply an XY machine where the Z is let to do its own thing to keep a stable arc voltage.
Title: Re: Titivating A CNC Plasma Table
Post by: PekkaNF on March 30, 2017, 06:36:53 AM
Thank you, I was wondering the rollercoaster drive on steel plate. Long time ago I was watching often even then old "optical" tracker of semiautomatic oxyburner to cut plates. They were not that simple to use and adjust. Sometimes the "seeker went wild" and run ofcourse torch blasting thick steel plate to art forms :doh:

Pekka
Title: Re: Titivating A CNC Plasma Table
Post by: RodW on March 30, 2017, 07:18:36 AM
Thank you, I was wondering the rollercoaster drive on steel plate. Long time ago I was watching often even then old "optical" tracker of semiautomatic oxyburner to cut plates. They were not that simple to use and adjust. Sometimes the "seeker went wild" and run ofcourse torch blasting thick steel plate to art forms :doh:

Pekka

I think now most Oxy cutters use capacitive sensing between the material and a ring around the torch that never touches the plate.
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on March 30, 2017, 08:52:21 AM
Hypertherm (makers of arguably the best Plasma power sources) advocate the use of 'Ohmic Sensing' as being most accurate, but my concern was I will often be cutting plate that is slightly rusty so it might not work reliably. There are systems out there that use both 'Floating Z' and 'Ohmic Sensing' - the floating Z effectively being a back stop.

Certainly Ohmic Sensing is simpler to implement and it avoids the use of a secondary slider.


... talking of secondary sliders - I'd got the hole spacing wrong on the THK-10RM rails and drilled and tapped at 20 mm centres rather than the 25 mm they should be  :bang:

However as it was all made on an alignment fixture I've been able to return the prototype to the CNC Mill in exactly the same place as before, and run a little diddy program to spot face, drill and tap the relevant four holes (and also modify the Autocad drawing accordingly !)

So my Faux Pas is recovered from without raising a sweat  :lol:

I do love making things on fixtures - this particular one just clamps in the Kurt vice, and I've bored an accurate 20 mm hole dead on centre which becomes my datum point. If I need to remove the fixture and replace it all I have  to do is lower my Heidenhain touch probe into the hole and tell it to find the centre - fast and accurate. The various parts bolt to this fixture using holes that are part of the workings.

It also means in this case that the various parts are held about 10 mm higher than the vice jaws, allowing profiling of the edges without risking cutters and jaws.
Title: Re: Titivating A CNC Plasma Table
Post by: RodW on March 30, 2017, 09:24:35 AM
I know the feeling. I have one hole to fill in with weld and retap. I got all mine laser cut but until I could actually check for fit I was nervous as hell with $1000 worth of parts....

Hypertherm (makers of arguably the best Plasma power sources) advocate the use of 'Ohmic Sensing' as being most accurate, but my concern was I will often be cutting plate that is slightly rusty so it might not work reliably. There are systems out there that use both 'Floating Z' and 'Ohmic Sensing' - the floating Z effectively being a back stop.

Certainly Ohmic Sensing is simpler to implement and it avoids the use of a secondary slider.

I don't think you can get of that lightly. Everything I've read says you need a backup either sensing motor torque or a float switch for those Oh! sh1t moments when you don't get an ohmic connection. I'd like to experiment with measuring motor torque by sensing the current the stepper axis draws. Even if I had to use an Arduino as an intermediary. My Plasma has a wire for the material clamp on its CNC interface (via a 100k resistor) so I might try it later. I have drawn up a circuit that should work and lock everything out while there is an arc.

Anyway, here's a sketch of the circuit I came up with. Check it carefully.
(http://i210.photobucket.com/albums/bb270/rodweb/Lathe/Plasma/OHMIC%20SENSOR%20CIRCUIT_zpss7bildad.png)
It was based on something I found on the net and I added the loop through the torch on relay as an added safety feature.
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on March 30, 2017, 02:05:13 PM
So, next thing to do is cut one of the THK-10RM rails in half, as I only need a very short movement. So - first transfer the slider off one rail onto the other one so that it can be cut without contaminating the bearing.

Now received wisdom is that this size of slider will fall apart shedding ball bearings unless the rails are pressed well together end to end, and the bearing pushed over the join carefully

Well I've news for you - they shed bearings anyway  :bang: Hundreds of them, and they're tiny  :bang: And in my case they are magnetic and stick all over the place  :bang:

Now in the last picture that minute bit of black plastic is in fact one of the track guides that reverse the balls so that they circulate. Even with tiny tweezers it was very reluctant to go back into it's recess in the end cap.
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on March 30, 2017, 02:12:10 PM
So now the slider is in bits I decided that I might as well go ahead and cut the rail, so in the unlikely event that I can re-assemble the bearings at least it can be done on the rail it will eventually occupy.

Cut with a 1 mm abrasive disk on a 115 mm angle grinder held in a 'chop saw stand' (Thanks Spurry for the suggestion :thumbup:) I then tidied the ends up on the Clarkson T&C grinder
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on March 30, 2017, 02:31:16 PM
So what about putting the bearing back together  :scratch:

Well in the end it took over two hours of frustrating eye strain  :bang: Several times I was nearly there - down to the last ten or so balls - when something slipped and I'd have to start all over again.

On each side of the slider there are two bearing sized holes parallel to the rail that at their ends point at the tangent point on the rail where bearings are trapped between the rail and the slider. If initially the slider is held in the correct alignment, balls can be pushed down these tubes from one end, and they will emerge between the body of the slider and the rail where the bearing action is happening.

However if the slider is ever so slightly off alignment the balls escape and get jammed in the wrong places  :bang:

Eventually I carefully measured the slider that was still intact, and put a small packing piece between the top of the rail and the under side of the loose slider to keep it in vertical alignment, with a tight rubber band around it to keep it together. Then it was a case of getting a few balls between the the rail and slider at the four tangent points to get the side to side alignment. Then 'just' a case of pushing bearings down the holes one by one until the holes and tangent points are full. Then quickly get the end cap on before it falls apart.

I probably repeated that process ten times  :bang: In one way the fact that the balls were magnetic was a help in picking them up with a tiny jewellers screw driver. But it was also a disadvantage, as, as you approach 'full tubes' several balls would decide to leap out and stick to the driver  :bang: :bang:

If I had to do it again, not only would I pack the vertical distance, but I'd make up something to go round the rails to fix the side to side spacing, that could be gradually withdrawn as the tubes filled and the balls emerged at the tangent points.

Anyway eventually it worked, and my headache hopefully will subside over the next few hours  :lol:

Title: Re: Titivating A CNC Plasma Table
Post by: Spurry on March 30, 2017, 06:02:03 PM
You must have the patience of a saint, Andrew. You did well not to lose any of the bearings too.  :clap:
From your experiences with these, would it help if the two rails were bolted to a piece of metal to keep the two bar ends in perfect alignment?
Neat result anyway, with those dinky little rails.
Pete
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on March 31, 2017, 03:00:27 AM
Thanks Pete. Yes I think that you are right about bolting the rails together temporarily..the second bearing slider transferred ok but it was a  'heart in mouth' moment.

In fact I did lose two ball bearings. The way these work with the balls trapped in a straight line I don't think that it will make any difference, certainly there is no perceivable play or roughness, and comparing with the other one they feel identical.

I will have to transfer two more bearing sliders of the bigger THK 15 size soon, as I won a pair on eBay last night fulfilling my wish to have the main Z slide on four rather than two. All those holes in the recently made plate will now come into their own.  :ddb:
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on April 01, 2017, 10:31:50 AM
Got a bit of time yesterday and this morning to draw up and machine the prototype Floating Z slide. NB this slide will be limited to only about 10 mm travel by stops yet to be incorporated - it just needs enough travel to operate a micro-switch that detects the surface of the metal being cut by the tip of the torch touching and displacing the slide.

Again I incorporated three positions that the bearing sliders can occupy, as just with the full travel' Z slide, I'd like to source two more sliders to give more mechanical rigidity.

Next job is to hack these plates about to fit the limit switches, mounting for the cable guide and plugs and sockets. When that's done I'll incorporate the changes in the Autocad drawings and make the final versions. I also want to take a bit of weight out of them to reduce inertia.
Title: Re: Titivating A CNC Plasma Table
Post by: mattinker on April 01, 2017, 11:09:14 AM
I can see that your going to entirely rebuild the plasma table to your usual exacting standards!

Glad to see you having fun! Matthew
Title: Re: Titivating A CNC Plasma Table
Post by: RodW on April 01, 2017, 11:10:01 AM
Looking good.

Personally, I think adding extra blocks is overkill. a pair of them is rated to handle 457 Newtons of force. Divide by 9.81 and you end up with them being able to handle a 46kg weight at the end of  a 1 metre long lever! Your torch will weigh in at around 0.8 to 1.0 kg at a guess. Specs are here
http://docs-asia.electrocomponents.com/webdocs/0f44/0900766b80f448f1.pdf

Once I looked at the ability of my Hiwin HGR15 slides to handle such forces, I just went with one slide for the Z axis mount and the float switch.
Title: Re: Titivating A CNC Plasma Table
Post by: awemawson on April 01, 2017, 11:22:52 AM
Thanks Matthew and Rod.

Rod, I've no doubt that they'll take the loading, but the existing Z main slide and floating Z slide are both based on single  HGR15 sliders, but there is noticeable wobble at the torch from the magnified microscopic play in the bearings due to the distance from the bearing to the torch. (About 145 mm of beam length)

So by sitting both sliding platforms on (hopefully eventually) four bearing sliders set a reasonable distance apart there is a good amount of triangulation so even a small amount of play will be constrained. It just seems a better engineering solution - due to the slightly heavier construction my beam length is increased to 157 mm (*) but the whole thing is far more rigid  :scratch:


(* actually that measurement is from the Z axis mounting plane so the actual beam length is about 60 mm less)