Author Topic: CNC Engraver  (Read 1232 times)

Offline AdeV

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CNC Engraver
« on: October 25, 2018, 06:51:36 PM »
Well.... it happened. Again.

Yep - a new tool for the workshop  :lol:

This time, I threw the awemawson Book of Machinery Buying (Scale: Large) away... and bought a diddy little thing - a CNC3018 "Pro" engraving machine from China. £140 delivered to my door. After a couple of impatient weeks waiting, it finally arrived last weekend, so I immediately assembled it (didn't read the instructions, naturally, keep reading to find out why that wasn't such a bright idea), and to my delight, it worked right away! Of course, I immediately crashed it four or five times, whilst trying to get used to the control system...

Anyways... I spent a little time tweaking the speeds & feeds, so now I can crash it REALLY fast  :zap:

The attached picture of it is as it stands right now.

 :proj:

I've got a bunch of diddy microswitches on order (they should have arrived by tomorrow), so Saturday will be spent making the first modification: Limit switches. That way I can set up the homing function, and the hard limits should stop me crashing it on quite such a regular basis.

Second mod isn't really a mod... when I put the table together, I bolted the linear bearing pillow blocks on so they were as far apart as possible, for maximum stability. So I lost a full 2cm of Y-axis travel.... so I'll whip the table back off & fix that.

Y, Z and leftwards X travel are all excellent, but there's a fairly nasty graunching noise when the X-axis is travelling to the right from the left-hand-side. I'm not 100% sure what's causing it, I suspect it's an iffy linear bearing. I've tried adding lithium grease, but it just made a big mess & no discernable difference. I have about 20 litres of way oil, I may try a little of that, but I don't have high hopes. So a future mod will be to replace the plastic Z-axis carrier with a proper metal one, and fit some better linear bearings.

Finally, you may be wondering why I got this thing when I have a perfectly good* Bridgeport CNC machine... well, actually, I don't plan to do any engraving with it, or milling (it's not rigid enough for milling anyway) - actually, I plan to use it as a CNC PCB drilling machine. Allegedly the spindle motor does 10kRPM. I don't think it's doing anywhere near that frankly, but it should go faster than the 4kRPM that the Bridgeport can manage. And when it comes to drilling PCBs... the faster the better, especially with really small holes. With much less weight in the table/spindle than the Bridgie, it will move from place to place a lot faster; and with no side forces from the drilling, the lack of rigidity shouldn't be an issue. Plus PCBs only have to be drilled +/- maybe 0.1mm or so accuracy, and that should be well within this machine's capabilities, even with the spaghetti ACME screws/linear guides.


* Also there's a bit of a problem with the Bridgeport: 18 months of doing nothing seems to have caused some electronics rot, when I powered it up last week, all seemed to be going well until it tried to start the spindle, then a bunch of magic smoke came out from one of the circuit boards  :(  I've identified one blown capacitor, but there's some fizzing/crackling going on on a circuit board I can't see, it's behind another board. So now that's become a project too. My plan was always to use the machine as-is until the controller blew & then retro-fit a new controller (LinuxCNC seems favourite), but if it's just flakey caps as I suspect, I'll try to fix it as-is first.

Anyway. It's Saturday soon, so with a bit of luck I'll be making limit switch brackets for the new toy! :beer:
Cheers!
Ade.
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Offline efrench

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Re: CNC Engraver
« Reply #1 on: October 25, 2018, 09:52:48 PM »
You could try replacing the balls in the linear guides.  I did that to several mgn15's and it cured the ratcheties :med:. The ball size was 2.778mm.

Offline ddmckee54

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Re: CNC Engraver
« Reply #2 on: October 30, 2018, 01:22:04 PM »
Silly question, but when you added the grease did you just add it to the rail, or did you take the bearing off and pack it with grease?  If you didn't pack the bearing, then the wipers on the bearing probably did their job and wiped the grease off before it got inside the bearing where it would actually do some good.  You need to pack the grease around the balls and into the race.

I had the same issue on the Y axis of my 3D printer.  My printer was a fairly low-buck Prusa I3 clone, so they probably went with the lowest cost linear bearings they could find.  I figured that they had to cut every expense they could in order to make any money off the printer.  I replaced the bearings with something that cost a little more than $50 per hundred.  I didn't get the high priced Fafnir's at $30 each, but I only spent $2-$3 each for the LM8UU bearings that I got.  I wanted something a little bit better, but I didn't want to break the bank.  They made a BIG difference.

You hate to do it with a new machine, but you might want to consider replacing the linear bearings on the X axis, and maybe even replace the bearings on all of the axis. 

Don
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Offline AdeV

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Re: CNC Engraver
« Reply #3 on: October 30, 2018, 07:22:46 PM »
Hi Don & efrench,

Thanks for the replies - no, I didn't pack the grease inside, and yeah, I probably should do... I used pretty lightweight lithium grease, if I'm going to dismantle it all, I might look at something a touch heavier. On the other hand... I can probably live with the crunchies, I don't plan to do any (much) actual milling/engraving with this machine. Rigidity is not it's strong point...

The motor carrier/X-Axis unit looks suspiciously like 3D-printed plastic, it's pretty easy to deflect just with moderate hand pressure. I think I may (at some point.... maybe possibly) make an aluminium unit, at which point I'll put better linear bearings in, and maybe even ballscrews, depends how flush and/or motivated I'm feeling at the time. Rather than fixing up this machine, though, I may use it as inspiration to make a better one from scratch, & just re-use the electronics/motors.


So, onwards and sideways.... at the weekend, I managed to spend a little time working on some limit switch ideas. Unfortunately, the microswitches I chose need itty bitty M2 screws to mount them. Something I don't have, and something kinda hard to come by at 6pm on a Saturday, and definitely not at all on a Sunday. Not wishing to abandon the project entirely, I made do with some hot glue for the time being. Remarkable stuff...

So, first, a couple of glamour shots of the machine as it is now (attached).

Cheers!
Ade.
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Offline AdeV

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Re: CNC Engraver
« Reply #4 on: October 30, 2018, 07:31:58 PM »
The wiring is very much temporary at this point. Whilst in China I discovered you can buy that "chain" stuff they use on real machines to keep the wires under control. Various people have made various 3d-printed plastic end pieces/mounting brackets for this stuff. So I foresee some of that in my future (but I'll have to mill brackets for the time being).

Anyway... the goal of the weekend (finished today) was to put some basic limit switches in place. Only one switch per axis just now, the plan is to have switches on the far end as well, to prevent any chance of accidental crashes. Putting the 3 switches on, however, allows GRBL to run it's homing cycle; add soft limits, and it' just stops instead of trying to drive the x/y/z axis into the wall, door or ground, if you press the wrong button or send it some iffy G-code.

First up, the Z-axis. For this, I hot glued (will eventually fit with proper screws) a microswitch to the top of the carrier. A simple plastic block was milled to size, an M4 screw thread tapped in to one side, this is the adjuster screw; and an M6 at 90 degrees to affix it to the machine. This worked OK, except the M4 thread in the plastic really didn't work at all well. It ended up so loose the bolt could be pulled right through it! As a temporary solution, adding some sellotape to the screw has given it enough bite. If it every fails, I'll re-do that part in aluminium.

To adjust, simply run the Z-axis Pretty Damn Close to the top of it's travel, then adjust the screw until the microswitch just clicks. A couple of tiddly tweaks got me pretty much the maximum travel that I'll get. Total travel is about 44mm, but I lose a couple of mm to the homing pull-off, which is the same setting for all axes. And, one slightly silly (IMHO) thing, if you move the machine back to it's newly read origin, the switch clicks & it locks out until you re-home it. Personally, I'd have liked to have seen it zero itself at its pull-off co-ordinates, so I could tell it the full travel available to it (minus the bit lost to the switches) & have it stop without alarming. But, hey ho. Maybe I'll have a dig in the code one day & sort that...

Attached picture shows the Z-axis adjuster block & microswitch. Please avert your eyes from the huuuge blob of glue. Me trigger happy  :palm:
Cheers!
Ade.
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Offline AdeV

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Re: CNC Engraver
« Reply #5 on: October 30, 2018, 07:41:25 PM »
The Y-axis setup I'm a little bit more proud of, although again I can't hold the microswitch properly. This time it's pinched in a really clunky bracket. Again, once the M2 screws rock up, that will be thrown away and a much sleeker bracket put in its place. It's simply screwed (using a spare "T"-nut that came with the machine) into the top of the side extrusion, roughly in the middle of the table travel.

The ends of the table extrusion have a 5mmx10mm (approx) slot, which is perfect for the "1" shaped end stop I milled up. As it ended up being a slight rattle fit, I added a small screw which simply pushes against the back of the slot to hold it in place. I only made one so far, another will be added later, which will give the Y-axis a hard stop on both ends, using just one switch. The photos show the really crappy bracket, and the end stop thingy.

The 1-shape is so it doesn't just smash the end of the microswitch. :lol:

The X-axis switch is just glued to the frame... I will make a proper bracket for it, as I can't glue it far enough back to not lose around 10mm of travel. I'll probably mount it lower down too, to catch the bottom of the Z-axis carrier, just so it's less in-yer-face. Wiring will all be sorted properly as well, at some point. Probably.

With the usual apologies for crappy lighting, sound and editing; follow the link for a very short video showing it homing itself to the various axes:

Cheers!
Ade.
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Offline raynerd

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Re: CNC Engraver
« Reply #6 on: October 31, 2018, 10:18:17 PM »
Nice one Ade. Looks fun for the money!
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Offline AdeV

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Re: CNC Engraver
« Reply #7 on: November 03, 2018, 04:43:58 PM »
So, a spot of progress today. Not as much as I'd have liked... but, well, some is better than none, right?

The M2 bolts had arrived (2 sets of them... oops), but no M2 tap! Argh! Fortunately I discovered this before midday, and the local engineering supply shop had one in. So I bought two, on the theory that if I only had one I'd break it or lose it; having a spare will prevent either scenario  :lol:

Z-axis was easy, I just drilled through where the switch was already held on with hot-glue, prised it off, tapped the holes & fitted it back on with appropriate bolts.  :thumbup:

Next up was fitting the cable drag/tow chain I bought; this is the stuff you see on grown up CNC machines which stops the millions of wires from flopping about, causing a trip hazard, catching on moving parts or finding their way - somehow - into the cutter... First up was a bracket to hold the end of the chain to the head. Lacking a 3D printer I whizzed it out of a piece of ali. Holes were drilled & tapped by hand. I had to remove the Z-axis motor to tap the holes, what a palaver THAT was! Totally worth it, though!

I still need to lash up the bottom bracket (that'll be dead easy), for now I've put some electrical tape on it just to hold it roughly in place.

As I don't have a 3D printer (did I mention that already?) I've not yet done anything to tidy up the top. I probably never will either... knowing me... :palm:

Anyway, below is an extremely brief video of the cable chain doing it's thing.



Cheers!
Ade.
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Offline AdeV

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Re: CNC Engraver
« Reply #8 on: November 03, 2018, 08:22:06 PM »
PS: I think I discovered why my M4 thread in the plastic Z-axis Adjustment Screw Holder AttachmentTM is so loose and wobbly....


...turns out I used an 8-32 UNC tap!!!

 :doh: :doh: :lol:

I think I'll re-make that block in Aluminium, and use the correct tap next time....  :palm:
Cheers!
Ade.
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Offline AdeV

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Re: CNC Engraver
« Reply #9 on: November 04, 2018, 01:50:47 PM »
More progress today - despite another project interfering... I made (after a couple of false starts due to advanced maths failure  :palm:) some T-nuts to go in the machine slots. The eventual plan is to get a piece of plastic the size of the table clamped down, with a section milled out to hold the standard sized PCBs I'll be working on, but I wasn't feeling it today so instead I just lobbed a piece of plywood I found lying around on instead.

Had a little go engraving, which worked OK, but plywood's crap wood for that sort of job. I'll try on a piece of plastic once I've got some double-sided tape to hold it down.

After that, I messed around drilling a cheap PCB blank I've got - and that worked perfectly! So I'm one very happy bunny tonight  :D

Still got a few more things to do before I'll be ready for regular PCB work, but I'm very happy with the machine. £140 well spent I reckon  :thumbup: (wives/significant others may disagree  :scratch: :loco: :lol:)

No video tonight, as I can't find my tripod head, and holding the camera even close to steady whilst sending manual G-code commands to the machine is - like trying to strike a match on a bar of soap - one of the few things in life that's actually impossible...
Cheers!
Ade.
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Offline WeldingRod

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Re: CNC Engraver
« Reply #10 on: November 04, 2018, 03:46:30 PM »
Cable chain is well worth the time!  You will put a LOT of miles on that thing!

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Offline philf

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Re: CNC Engraver
« Reply #11 on: November 04, 2018, 03:59:19 PM »
Ade,

You could have a go at isolation milling the tracks on your pcbs as well as drilling them on the machine.

I've had some success doing it on my mill. It may not work so well with very small tracks or very densely packed surface mount components.

Phil.
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Offline AdeV

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Re: CNC Engraver
« Reply #12 on: November 05, 2018, 03:11:49 AM »
Hi Rod & Phil,

Yep - cable chains are almost as mesmerising as the shaper! Almost.... I'm extremely chuffed I've bought them, they make the machine look much more finished, if you know what I mean.

Speaking of chain - I've got about 570mm left over of the metre I had to buy, if any MadModder wants it for free, just drop me a PM. No end plates I'm afraid (I'm using both of them), but you could 3D print or mill something up easily enough I'm sure. UK only because of postage costs TBH, if you live in Forrin* then you'd probably be able to get it cheaper from a Chinese seller than I can post it to you...

Phil - Yeah... isolation routing... I've never really liked the idea much, not sure why as I know loads of people use it, there's no chemicals involved, etc. However, I've already got most of the chemicals & containers to do a full PTH production line... just need to start putting all the jigsaw pieces together... That will be the subject of another series of MM posts I'm sure (if anyone's interested!).

I'll be doing this "old skool" - using silk screen printing for various stages; lots of chemicals and so on; a UV light box (1st project... it needs a PCB... spot the catch 22!). So far the hardest job has been finding a silk-screenable photoresist, so I may end up going with dry film, which is not the process as I remember it from the 1980s when Dad used to run a PCB production line.

Anyhow... fun times ahead! Still got a couple of slightly more professional looking brackets to make for the little machine, I'm going to try to get a couple of evenings in the shop this week, to get things moving.



* Forrin = Foreign = anywhere outside the UK, in case that wasn't clear!!
Cheers!
Ade.
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Offline AdeV

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Re: CNC Engraver
« Reply #13 on: November 08, 2018, 05:05:04 PM »
That's more like it!

I suppose, one day, I might make some brackets which hide the microswitches away... but I kinda like them being out on show. It makes them easy to test too!
Cheers!
Ade.
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Offline AdeV

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Re: CNC Engraver
« Reply #14 on: November 10, 2018, 12:22:45 PM »
A couple of hours fannying about at the mill (about 1 hr of which was tidying up and lining the vice back up properly; I'd taken it off last week & only roughed it in...), and I produced a dead simple bracket from a piece of 6mm plate I had lying about. No process shots, it's all easy peasy stuff that we've all done.

The bracket is held to the machine with a single M4 screw. I did consider putting 2 in, but I can use the rotation to adjust it "just so" to maximise travel. And, somehow, I've managed to get the full 300mm width with the switch in its new position  :clap:

So, a few piccies of it in its new home.

Next up.. a full-size plastic sacrificial bed.... then I guess I'd better design a PCB to drill!
Cheers!
Ade.
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Offline AdeV

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Re: CNC Engraver
« Reply #15 on: November 10, 2018, 02:51:33 PM »
Aaaaand TADA!

OK, I make that sound like I've just done some spectacular milling work...  :lol:

The supposedly 10mm thick acrylic sheet is, unfortunately, only 8.5mm thick, which means I can't countersink the bolts as far as I want. Still, with a bit of care, I should be able to set my lowest Z-point a tad* above the bolt heads. And if that's not enough to guarantee a clean hole through a PCB, then I'll just sand the heads a bit flatter. They're only holding the plastic sheet down, there's 6 of them, and they're not in murder tight... so I don't need the full depth of the hex socket to tighten them up.

Onwards!


*A "tad", in space terms, is about half a million miles...
Cheers!
Ade.
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Offline AdeV

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Re: CNC Engraver
« Reply #16 on: November 11, 2018, 03:04:20 PM »
Another update on this machine... I've got a couple more things to do:
  • Find a way of accurately locating the PCBs on the bed, so I don't have to arse about aligning them every time (anyone who's set up a job on a milling machine will know what I mean...)
  • Setup the Z-probe so I can do tool-changes mid-program.

Taking the second one first, I've identified that the tip of the tool is, conveniently, electrically connected to the body of the motor, which isn't connected to either positive or negative terminals. So I need to find a way of attaching the motor body to one side of the probe pin. For the bed, I can either use the copper surface of the PCB being drilled, or I could make a standard "puck" to do the job.

Anyway, having proved the probe actually works, I decided to do the first item instead.

So, the way this will work is: At a specific machine position on the bed, I'll mount a couple of fences, to which the PCB is aligned, before being stuck down with double-sided sticky tape. The first photo will make it clear (and if not, some of the other ones will put it beyond doubt!  :lol:)

First job, therefore, was to mill a couple of slots in that bed plate. To ensure they're dead straight and aligned with each other and the machine... I chose to do them on the machine itself  :bugeye: Remember how I said I didn't intend to do any engraving (let alone milling!) on this machine due to it's rigidity issues?  :loco: More of that in a moment...

So. Recently I bought a 2mm end mill for another part of this project. Seemed ideal! Plus it fits in the only ER11 collet I have, which is a bit of a Brucie Bonus. Mount it up in the machine, knock together a nice simple bit of G-code, Billy's your aunt, Fanny's your uncle, and everyone's very confused :D I decided on 0.25mm cut depth, nice slow feed rate of about 100mm/min, as I'm really not convinced this machine's stable enough for heavy cuts, even in plastic. More about that in a moment...

So, off it went! I videoed the whole thing, and once I get time to edit it & do the timewarp thing (who wants to watch a noisy machine vibrate it's way around an "L" shape for 15 minutes?), I'll upload it into a post below. Thus, no photos of the process. However, it seemed to go OK. Noisy, like I said, and lots of vibration. This really isn't any cop as a milling machine... but it got there. I suddenly realised (3mm into the slot, which I'd planned to be 5mm deep) that my cutter was looking awfully close to the tapered section. A quick scan of Arc Euro's website for the bit showed - yep, the one I've got has only got 3mm depth of cut! As it was already onto the 3.25mm cut, I let it finish that, and stopped it. Result is the first photo, after a bit of a clean up.

Next, time to get the real milling machine out, and make an aluminium fence. First, I cut a piece of 6mm ali down to 2mm, 0.100" DOC (like NASA, I like to mix up my units. Keeps everyone on their toes  :scratch: :zap:). Figured I'd better test it in the slot before I went much futher and... what's this?! Wibble-wobble! Break out the digital calipers and - crumbs! The slot is 2.3mm wide! Not good! That's where the lack of rigidity/vibration, or maybe it's backlash, shows up. So, if anyone was wondering, no: This is not suitable as a desktop milling machine...

Anyhow, this was no disaster for my purposes; I simply hacked off the 2mm bit & did a 2.3mm bit instead (I even got the old digital micrometer out for a bit of exercise!). After hacking it off the parent metal with the Deadly Dangerous Circular Saw From Beyond The Grave, and a bit of clean up, cut to length, repeat (the piece of metal wasn't long enough to do both), you end up with 2 tidy looking aluminium fences, per photo 2. These, gratifyingly, are a nice tight press fit into the slots, resulting in photo 3.

Happy days! Now I can simply line a PCB up to the two fences, stick it down, and I'll know it's exactly (to within the tolerances I need) where it should be! Plus, as it's only 2 sides, I can put different sized boards on without any hassle. As they're just push-fit, if I ever replace the bed, or need to drill a bigger board than I've left space for, I can pop them out, and either cut new slots on a new bed, or replace them once I'm done with the big board. (photos 4, 5)

All in all, a happy couple of hours machining :)

PS: Sometimes, the Chinese aren't too sharp with the PCB cutting tools... see photo 6 - this board's a bit wonky! When it comes to making the real thing, I'll probably use UK-sourced board, which I hope will be rather squarer cut! In fairness to the Chinese though, that's the only one that I've found that's out of kilter.

Next episode should be Z-probing, and possibly drilling an actual board!
Cheers!
Ade.
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Offline paulc1

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Re: CNC Engraver
« Reply #17 on: November 15, 2018, 03:43:15 AM »
Looks like a fascinating project Ade, when you said that you were getting a CNC engraver I imagined it working right out of the box  :doh: lots of work but it is going to be worth it by the looks of it :thumbup:

Offline AdeV

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Re: CNC Engraver
« Reply #18 on: November 15, 2018, 01:28:05 PM »
Hi Paul,

In fairness - it did pretty much work straight out of the box; what I'm adding to it are the "nice to have" things, which just make it a pleasure to use instead of a chore...

The biggest issue I've found with it, is the bed's not level with the spindle - the first cut when I slotted the bed plate was 0.25mm deep, and the last 3-4cm of that first cut was an air cut. So not ideal in an engraver, but no big deal for a drilling machine. If one had the patience, it would be possible to set the machine off to level the bed by cutting it... One of these days, I'll give it a bit of a workout and see just what sort of depth of cut/width of cut it'll reliably take: but I need another ER11 collet or two before I can mount any bigger cutters.

I've got another feature to probe this weekend.... yep, a probe! As you'll see, this will be a proper copper bottomed sub-project  :) Spoiler alert: It turns out I can use the cutting tool itself as a probe, bonus!
Cheers!
Ade.
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Offline gerritv

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Re: CNC Engraver
« Reply #19 on: November 15, 2018, 02:36:12 PM »
Hi Paul,

In fairness - it did pretty much work straight out of the box; what I'm adding to it are the "nice to have" things, which just make it a pleasure to use instead of a chore...

The biggest issue I've found with it, is the bed's not level with the spindle - the first cut when I slotted the bed plate was 0.25mm deep, and the last 3-4cm of that first cut was an air cut. So not ideal in an engraver, but no big deal for a drilling machine. If one had the patience, it would be possible to set the machine off to level the bed by cutting it... One of these days, I'll give it a bit of a workout and see just what sort of depth of cut/width of cut it'll reliably take: but I need another ER11 collet or two before I can mount any bigger cutters.

I've got another feature to probe this weekend.... yep, a probe! As you'll see, this will be a proper copper bottomed sub-project  :) Spoiler alert: It turns out I can use the cutting tool itself as a probe, bonus!
Would it be simpler to shim the bed? If it is flat, them probing at the locations of the linear bearings should give you suggestions on which linear rail to shift and at which end.

Gerrit

Offline AdeV

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Re: CNC Engraver
« Reply #20 on: November 15, 2018, 03:53:02 PM »
Hi Gerrit,

It would be simple enough to shim the bed... but I can't guarantee it won't move horizontally, which would bugger up my milled slots  :doh: Anyway, for my purposes, it's good enough, I'll be drilling right through into the plastic anyway. I'm also not 100% convinced it's completely flat either - I believe there are programs out there to "map" the bed height for these type of machines; not something I plan to do, but probably worth doing if you're doing a very fine engraving (but, if you're doing very fine work.. would you do it on an unmodified sub £150/$200 machine from China...?)
Cheers!
Ade.
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Re: CNC Engraver
« Reply #21 on: November 17, 2018, 12:17:55 PM »
Can you guess what it is yet?

 :lol:

OK.. that's not fair. This little mini-project took a couple of hours on the lathe, once I'd finished procrastinating. I'll keep the writing short this time...

Photo 1: Some copper bar I bought ages ago to make spark eroder electrodes from; but which is proving rather useful today; and a lump of "mystery steel", I think it might have been a ginormous pin out of something, but goodness knows what. It's a bit of a bear to cut, but the price was right: £free  :med:

Photo 2: After chucking up the copper bar, turn around 1/2" down to 0.656", the major diameter for a 3/8" BSP thread. Chosen because it fits comfortably inside the diameter copper I have, the thread count is decent for such a big thread, and I have both taps and dies and the tooling to fit them  :headbang: I really need to sort my taps/dies/tapping handles/die holders out... a boring job for another day. Photo 3 shows the stringy, gummy, razor sharp swarf that copper makes. It's evil stuff to turn. I did wonder about work hardening it, but apparently it's its day off?  :scratch:

Photo 4: I cut a gutter at what will be the mating face, just so I could run the die right up to the shoulder & know it's cut full depth all the way. Follow up with the die, and a 19tpi thread file just to clean them up a bit.

Photo 5 & 6: Cut the threads down so around 3 were left (the part was far too tall), then parted off, leaving approximately 0.1285"/3.26mm of original diameter copper. OK, I admit it, those measurements were made just now as I write this... I left "enough" on.

That's it for the copper... for the moment.
Cheers!
Ade.
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Location: Wallasey, Merseyside. A long way from anywhere.
Or: Zhengzhou, China. An even longer way from anywhere...
Skype: adev73

Offline AdeV

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Re: CNC Engraver
« Reply #22 on: November 17, 2018, 12:32:46 PM »
Moving on, the steel goes in, and using one of those new-old carbide bits I was asking about the other week, was roughed down to something approaching its final dimension. The cutter is amazing - it needs a huge depth of cut, and it needs to be really thrown at the workpiece, otherwise it makes blue/black chips. Fantastic for hogging off big bits of material, which is handy, as that's what was needed today  :palm:

Photo 1: The heavy cuts have been taken, and the middle drilled out to 15mm to a depth of just under 1/2" (pointy bit), leaving approx 0.400" usable depth.

Photo 2 & 3: Setup for tapping (taper tap, followed by a plug tap (not shown). I start it under power @ 17rpm, but stop after a few turns and take over tapping by hand. I want to feel the bottom of the hole before the tap breaks, not afterwards...  :zap:

No photos of the finished thread. Well... that's not strictly true - I took three photos, and you can't see the damn thread on any of them! The contrast in the metal just isn't big enough... it all just looks like it's had a boring bar fitted with an axe head up its spout... Anyway...

Photo 4: After a bit of a cleanup with a brush, the copper part is now screwed in (whilst the thing is still on the lathe). It's a decent fit, requiring a pair of pliers to move it the last few turns. All remaining operations will try to force it to tighten up, so I'm not worried about that gummy muck from digging in and breaking the tool (you can absolutely guarantee it would do it if the cut was trying to loosen the thread....).

Photo 5 & 6: Trimmed down to the same OD, with just a skim taken off the copper. The surface finish really is that bad. I should have probably used oil.

Photo 7 & 8: Almost there now! The part has been parted off from the stock, turned around in the chuck & faced, and given a generous chamfer. In use, the copper side sits downwards - hence, a copper-bottomed project*

One more operation done (but not shown), I've drilled/tapped an M6 threaded hole in the side, about 1/2 way up, and above the copper baseline (but drilled/tapped into the copper slug). This will take a copper screw, with a smaller hole drilled down its centre... except that I don't have an M6 die I can adequately hold just now, so we're at a temporary haitus.

Anyway.... can you guess what it is now?  Answers later/tomorrow...
Cheers!
Ade.
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Location: Wallasey, Merseyside. A long way from anywhere.
Or: Zhengzhou, China. An even longer way from anywhere...
Skype: adev73

Offline AdeV

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Re: CNC Engraver
« Reply #23 on: November 17, 2018, 02:27:40 PM »
Lacking patience, but recalling that I recently bought an indexable threading tool.... much haste was made to the lathe! Miracle of miracles, the threading tool was already in a QC toolholder! No height adjuster yet ( :palm:) so I just eyeballed it in, after turning down ~10mm of that copper bar to 6mm. Got a fantastic surface finish... I wish I'd photographed it, but it was being turned into an icky thread anyway...

So: Switch the lathe into French Mode, reverse the reverser, etc. and dial in a 1mm thread pitch... and off!

I wish I'd recorded it with a video camera (or even a stills camera TBH), because it worked surprisingly well, even though I thought I'd lunched it at one point with a slightly over-aggressive cut. Still, after 6 or 7 passes, feeling my way to depth, it got to the point where it'd screw in, part way at least. That'll do for me tommy! So, I drilled a 1.5mm hole through the middle (that cost me a 1.5mm drillbit, I just HAD to have one more peck at it didn't I?  :wack: Screwed it into the main lump as far as it wanted to go & parted it off with a hacksaw. Using the same hacksaw I cut a slot across the middle for a screwdriver.

The result can be seen in photo 1, with a 50p for scale. If you're watching this in the colonies, that's about the size of a silver dollar. But not the value, unfortunately...

Next up, thread a wire through the 'ole (photo 2), solder it up (hence the copper; photo 3), and screw it into the block as tight as it'll go given the means I have to actually tighten it (i.e. sod all!) See photo 4 for the finished item.


Now, as I'm sure you've guessed, this is the probe "puck" for my CNC machine (hence being here in this thread  :palm:) There's a couple of ways I'll be able to use it. Toolbit mounted in the motor is electrically attached to the motor body - which is great; so I'll attach a wire to the motor body going back to one of the probe pins. The other will go to the puck. If I'm drilling a circuit board, I can simply place the puck on the PCB, and use the copper surface itself to get the Z=0 point. If I'm engraving/drilling something non-metallic (or a single-sided PCB copper-side-down), then I can simply measure down to the puck itself, which - serendipitously - is exactly 15.55mm high. So probe to the puck, set Z at 15.55 minus the stock height.

So, there we go! Just got to connect it all up to the machine, maybe make a little holder so it sits out of the way when not in use, and that's another useful feature of the machine enabled  :thumbup:


FAQs:
Q: Why the copper screw?
A: I did actually make another one, which I tried to solder the wire to directly. Problem was the solder froze waaay to quickly, and I just couldn't get enough local heat into it to make it melt again. And it looked a mess.

Q: Why didn't you just make the whole thing out of copper?
A: Shut up.
Cheers!
Ade.
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Location: Wallasey, Merseyside. A long way from anywhere.
Or: Zhengzhou, China. An even longer way from anywhere...
Skype: adev73