Author Topic: The Sequel - Oh Blimey I bought a CNC Lathe (Beaver TC 20)  (Read 52442 times)

Offline awemawson

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Re: The Sequel - Oh Blimey I bought a CNC Lathe (Beaver TC 20)
« Reply #850 on: June 04, 2019, 10:11:43 AM »
It was at this stage that I dug out my 'soft jaw clamping fixture' that I  had bought for similar service on the Traub lathe, only to find it was dinky compared to what was needed. I had been sure that it would work, but the difference between a 10" and a 6" chuck is rather a lot !

So what to do  :scratch: I could make something up for this one size, but this is going to be an ongoing requirement as jaws are changed in the future. Better to bite the bullet and get the right thing. A bit of ringing around  for best price set the dealers into a flutter, as behind the scene it turns out that they were ringing each other to see who had stock. Rotagrip won the day, and then minutes after I placed the order Cromwell Tools rang me back to say that their supplier had just sold their last one, and they were now on 8 weeks delivery. Yes says I, I just bought it  :lol:

Excellent next day delivery, so the clamp ring arrived this morning by Adrian with ParcelForce.

Now the theory is that you adjust the ring to such a size that the hydraulic chuck jaws bear down on it via pegs that go into the counter bores for the jaw mounting screws and it ends up clamped with a bit of 'meat' for you to bore out with a boring bar. It's actually quite a job juggling it, holding it in place, and operating the 'chuck close' button that is a fair distance away from the chuck.

It was at this stage I found that as these were new jaws and still fairly long, the clamping ring at its extreme would not clamp  :bang:

A bit of head scratching showed that as the clamp pegs are 18.5 mm and the chuck jaw counterbores are 25 mm, the slack was the problem. Quick solution, turn up some collars to slip over the pegs and sure enough we now have the correct travel to clamp, but we also have a pile of bits to hold in place at once while pressing that button, arm outstretched. Flying to my aid came some rare earth magnets, that not only held the collars on, but nicely held the clamp ring against the chuck jaws  :clap:
« Last Edit: June 04, 2019, 10:39:00 AM by awemawson »
Andrew Mawson
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Offline awemawson

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Re: The Sequel - Oh Blimey I bought a CNC Lathe (Beaver TC 20)
« Reply #851 on: June 04, 2019, 10:30:26 AM »
So at long last boring could commence  :thumbup:

I'd turned up a plug gauge on the manual lathe with 24.5 and 25 mm diameters, as this boring was going to have to be done the old fashioned way - cut - measure - cut again. (The boring bar hasn't been measured and put in the tool offset table yet!)

So, cut a bit, measure, cut again measure with the bore gauge, get a finish depth of cut a whip it off. I used the jog facility and MPG rather than a program as the tool disk gets rather close to the chuck jaws as I wanted to minimise tool overhang.

. . . so what should have taken a couple of hours took a couple of days !
Andrew Mawson
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Offline awemawson

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Re: The Sequel - Oh Blimey I bought a CNC Lathe (Beaver TC 20)
« Reply #852 on: June 11, 2019, 06:48:38 AM »
Some of you may recall that I went to great efforts to mount a Renishaw MP12 probe, only to find that it's optics looked in the wrong direction being intended for a milling machine not a lathe.

I did an experiment with transmission through glass that proved that the IR wavelength used would pass, so ordered some prisms off eBay that have been on a slow boat from China, hoping to turn the beam through 90 degrees.

Well the boat has docked at last and would actually appear to have come from Malaysia. I had ordered four prisms, knowing that two would when joined cover the width of the optical window in the probe, and the others could be spares. Just as well, as two of them were chipped. Frankly unlikely to affect the passage of the IR much, just unsightly.

So experimenting with the two chipped ones - not worth sending them back at the price they were(n't) - I super-glued them together with  the smallest drop that I could decant, then fixed them temporarily to the MP12 with a tiny dab of hot melt glue that will be easy to remove without damage to the probe.

Lo and behold - they WORK  :clap: Now I just need to devise a more robust method of retaining them on the MP12 probe that looks less crude than the experimental set up - but definitely a success  :thumbup:

Andrew Mawson
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Offline nrml

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Re: The Sequel - Oh Blimey I bought a CNC Lathe (Beaver TC 20)
« Reply #853 on: June 11, 2019, 08:47:55 AM »
A sung fitting 3D printed sleeve to go around the probe with a suitable mounting point for the prisms would do the trick.

Offline AdeV

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Re: The Sequel - Oh Blimey I bought a CNC Lathe (Beaver TC 20)
« Reply #854 on: June 11, 2019, 12:39:07 PM »
Lo and behold - they WORK  :clap: Now I just need to devise a more robust method of retaining them on the MP12 probe that looks less crude than the experimental set up - but definitely a success  :thumbup:

Something vacuum formed, perhaps?  :D
Cheers!
Ade.
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Offline awemawson

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Re: The Sequel - Oh Blimey I bought a CNC Lathe (Beaver TC 20)
« Reply #855 on: June 12, 2019, 09:23:00 AM »
Having had all the problems reaching over manually opening and closing the chuck to fit the jaw boring spider when I wanted to bore some soft jaws I went hunting for solutions.

Most commercial CNC lathes would have foot pedals to open and close the chuck so why not retro-fit some  :ddb:

I went hunting for spare digital inputs and some way of intercepting the drive to the 'open' and 'close' solenoids and drew up a simple schematic - it didn't even need any alterations to the PLC.

So, going to the termination strip for my selected input I was very surprised to find a wire already attached - it wasn't spare after all  :bang: So, attaching my 'tone tracer' to the wire I traced it all the way to the front hydraulic cabinet under the headstock and thence on to a socket on the side of the box that I'd never before noticed. Now this socket also has a double below it, and they are JUST where I would have put sockets for foot pedals . . . you don't suppose . . . no surely not . . . YES looking through the PLC code and relating it to the wiring diagram they are for foot pedals for the chuck and for the tailstock - whoopee  :clap: :clap:

Looking at the PLC code they both act on an already energised item - so if the tailstock barrel is pushed forward the foot switch will withdraw it until you take your foot off, where in it returns extended. Similarly a closed chuck will start to slowly open when your foot is depressed, and start closing when you take your foot off. EXCELLENT  :clap:

So I ordered up the appropriate connectors and a pair of sturdy foot switches and the later arrived at lunch time. OK cable them up and test them !

The foot switches are I think excellent value - cast aluminium with a proper heavy duty micro-switch. My only criticism of them is the cable management. The entry was a plain bush and a flimsy bent metal 'C' shaped clamp, but easily replaced by a proper cable restraint gland, and it's not so easy to route the cables so that they are not flexed each time the pedal is pressed, but it is possible.

OK Wired up, plugged in and tested - all works  :thumbup:




« Last Edit: June 12, 2019, 11:13:13 AM by awemawson »
Andrew Mawson
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Offline awemawson

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Re: The Sequel - Oh Blimey I bought a CNC Lathe (Beaver TC 20)
« Reply #856 on: July 03, 2019, 05:28:24 AM »
I've been doing quite a bit of work recently with 1" and 25 mm bar stock, and not been able to use long pieces for fear of it whipping when run at speed. The solution to this is a 'spindle liner' to reduce the internal bore of the spindle to a reasonably snug fit around the stock thus preventing whip.

So I decided to print up three 'Pucks' on my 3D printer with an o/d of a tad under the 66 mm spindle bore, an i/d of a tad over 25 mm for the stock, with counter bores to receive two spacers made from domestic ABS waste water pipe. As the pucks were printed in ABS this made the gluing together simpler as I could just paint the bits with acetone.

I designed the puck with an outer groove to receive an 'O Ring' to give a bit of friction to discourage 'walk out' and hopefully prevent it rattling too much. Not having the correct O rings I glued some up using O ring cord.

In the event the cord was a bit too fat and prevented the pucks entering the  spindle bore so I will order up some slimmer ones, but in the mean time I did a full speed test working up from 500 rpm to 3500 and in practice there wasn't a 'walk out' tendency, but I shall still fit those smaller O rings when they arrive.

One side benefit was the ease of inserting a 4 foot long bar that was already aligned by the pucks to side between the chuck jaws :thumbup:
Andrew Mawson
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Offline awemawson

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Re: The Sequel - Oh Blimey I bought a CNC Lathe (Beaver TC 20)
« Reply #857 on: July 20, 2019, 03:31:54 PM »
I was very fortunate recently in that I won for a modest sum a job lot of  VDI 40 tooling on eBay that included a Grippex Bar Puller.

Bar pullers are useful on a CNC lathe if doing repetitive work, in that you can automate the feed of the bar stock in the chuck between components. Advance the gripper over the bar, close it, grab the bar, release the chuck grip, pull bar out the length of the next component, close the chuck, release the gripper - all so nice and easy as it's automated  :thumbup:

Now this gripper sadly had one of it's hard steel 'talons' missing - never mind - spares still available for the not inconsiderable cost of 99 (inc postage and VAT) for a set of three - BUT you get the fixing screws AND an Allen key, so a bargain  :bang:

Biting my lip and remembering that these grippers cost 1400 new I shelled out my dosh and got the three spares.

Now I have a repetition job of 100 parts to do for a friend of a friend so time to mount it and play with some code. The gripper has a cylinder inside that can be operated by compressed air or coolant. No air service on this lathe so coolant it is. The sequence is, select the gripper, put it where you want it, turn the coolant on, do the pulling bit, then turn the coolant off again to release its grip.

Well, gripping works famously, but when the coolant is turned off it doesn't release. As the coolant is solenoid valve driven to the tool turret, coolant pressure is maintained in the line keeping the gripper firmly shut  :bang:

OK a modification is called for. Another solenoid valve working in anti-phase with the feed valve dumping pressure in the line to the sump. It would have been VERY easy if I could have sourced a 24 volt DC 1/2" BSP brass valve in a normally open configuration at a sensible price, but they are rare with the proper industrial ISO plug in connectors.

Never mind, use a normally closed valve, add a couple of lines to the PLC program to add another output for this valve in anti-phase to the feed valve and the job's a good 'un  :thumbup:

So valve and a few bits of plumbing have been ordered, and today I tweaked and tested the changes to the PLC program and now I'm just waiting for the bits to arrive .



« Last Edit: July 20, 2019, 03:58:10 PM by awemawson »
Andrew Mawson
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Offline AdeV

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Re: The Sequel - Oh Blimey I bought a CNC Lathe (Beaver TC 20)
« Reply #858 on: July 21, 2019, 05:23:24 AM »
A friend of mine is a CNC machinist by profession, I was talking about bar feeders to him one day, he said - don't bother... just turn up a piece of tube to be a 1 thou interference fit. Put a shallow taper in the front end just larger than your bar stock, so the end slips over. Now mount it in a toolholder. When you want to pull the bar; simply drive the tool onto the bar; release the chuck; pull the tool back the desired distance, close the chuck, then pull the tool off the bar... job done!

Obviously, you have to make one for every size of bar you want to pull; and it's no good if you need to pull something that's not plain bar; but it struck me as an elegant solution to the problem: Simple, cheap and reliable.

On the other hand... those grippers look cool!  :thumbup:
Cheers!
Ade.
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Offline awemawson

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Re: The Sequel - Oh Blimey I bought a CNC Lathe (Beaver TC 20)
« Reply #859 on: July 21, 2019, 06:48:39 AM »
The Grippex gripper works on a large range of diameters and also will grip hex. I think mine covers 2 mm to 60 mm without adjustment.

There are parting tool holders that incorporate a push fit forked gripper that grabs the bar by pushing in the X direction rather than Z - their concept is quite clever in that usually you want to bar pull after parting off so this avoids an extra tool change and associated move to a safe place, but like your tube the range of sizes is severely limited.
Andrew Mawson
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Offline awemawson

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Re: The Sequel - Oh Blimey I bought a CNC Lathe (Beaver TC 20)
« Reply #860 on: July 22, 2019, 08:24:51 AM »
Still no parts but at least today I ran the cabling from the digital output, across three cabinets within the existing trunking, bored a 20 mm hole for the cable gland and terminated the cable on the other side of the gland  in an illuminated DIN 43650 solenoid socket ready for when bits arrive.

I even bored a hole in the lid of the coolant tank to take the output hose from the currently non existent de-pressurising solenoid valve.


 . . . . . so back to thumb twiddling . . . . .I don't do the patience thing very well  :lol:

Andrew Mawson
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Offline awemawson

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Re: The Sequel - Oh Blimey I bought a CNC Lathe (Beaver TC 20)
« Reply #861 on: July 26, 2019, 10:11:20 AM »
The Valve and plumbing bits have now arrived so they got fitted this morning

As intended, the pressure is released from the coolant hose allowing the Grippex bar puller to release. Having this valve has the side benefit that the selected tool doesn't spray coolant for quite so long when the coolant is turned off. As the last operation is usually parting off, and the parting tool has a habit of spraying you with coolant previously left pressurised in the line, this is a GOOD THING :thumbup:



This video shows the new valve working as several tool changes and turning operations are performed. So now all sorted apart from a weep from one of the hose barb fittings that I must sort out. Probably just needs a new Jubliee Clip.

Andrew Mawson
East Sussex

Offline Johnny Bravo

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Re: The Sequel - Oh Blimey I bought a CNC Lathe (Beaver TC 20)
« Reply #862 on: July 28, 2019, 11:46:10 AM »
Great to see it up and running. Should have shouted,I have spare Grippex teeth  :thumbup:
Think I might be following your footsteps on this,have been offered a lathe with live tooling that could do with some tlc....Going to have a look in the week

Offline awemawson

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Re: The Sequel - Oh Blimey I bought a CNC Lathe (Beaver TC 20)
« Reply #863 on: July 29, 2019, 09:51:58 AM »
It was evident watching that last video that there was a danger of the coolant hose getting caught on the X axis termination box, so today I fitted a spring loaded support. I've a feeling that there was something similar originally, but can find no evidence on my earlier photos. The coolant pump and filter had of course been dragged from the tank and placed on the box ways (  :bang: ) when I got it, and that would have displaced any existing support.

While I was at it I solved that slight coolant weep at the hose barb fitting with a turn of thick gas rated PTFE tape.

Andrew Mawson
East Sussex

Offline Sea.dog

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Re: The Sequel - Oh Blimey I bought a CNC Lathe (Beaver TC 20)
« Reply #864 on: July 29, 2019, 12:36:10 PM »
I was thinking to mention a support for no other reason than it will prevent eventual collapse of the pipe.
A neat solution.

Offline awemawson

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Re: The Sequel - Oh Blimey I bought a CNC Lathe (Beaver TC 20)
« Reply #865 on: August 15, 2019, 05:09:44 PM »
Just to show I've not been idle, and have been actually USING the Beaver TC-20 here's a picture of two hundred parts I've run off for an acquaintance on another forum. One part is a taper adaptor and the other a simple spacer.

It was a very useful leaning exercise, using the bar puller, and involved boring more soft jaws. Although 'spot  on' soft jaws are still available they cost an absolute fortune. I was lucky enough to pick up eleven used sets on eBay that had the correct 1/16" by 90 degree serrations, but had M12 fixings on a closer spacing than the M16 originals, so this involved making stepped Tee Nuts to suit and re-machining the noses on the CNC mill to remove the existing curves prior to boring.

I also had to make a custom spindle liner

The exercise has made me think that a 'Tumbler' of some sort would be a useful addition to the workshop to de-burr parts like these that are very fiddly to do by hand. Has anyone built one?
« Last Edit: August 15, 2019, 05:39:42 PM by awemawson »
Andrew Mawson
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Offline hermetic

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Re: The Sequel - Oh Blimey I bought a CNC Lathe (Beaver TC 20)
« Reply #866 on: August 16, 2019, 01:08:01 PM »
I built this tumbler for my daughter, from an example on the internet, it is for rock polishing, so you would need to go up a few levels to get enough vibration, but any motor with an eccentric weight attached will do the biz.This uses a computer fan with a 10mm nut and bolt in one of the blades, and you can vary the level of vibration by using different sized bolts.

Offline PekkaNF

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Re: The Sequel - Oh Blimey I bought a CNC Lathe (Beaver TC 20)
« Reply #867 on: August 16, 2019, 04:12:25 PM »
I concider building one, but bought case tubler - the type reloaders use with corn or peanut husk. Maybe if I had all parts, but would have not got it any cheaper - probably whole lot bigger.

Brother has one of these:
https://www.amazon.com/Lyman-1200-Sifter-Promo-Model/dp/B0063GS1Y2/ref=sr_1_1?keywords=Lyman+Pro+1200+Tumbler+%28230-Volt%29&qid=1565985760&s=gateway&sr=8-1

Bought this type (230V with proper Schuko), it is rather small, but works for me.
https://www.academy.com/shop/pdp/frankford-arsenal-quick-n-ez-case-tumbler

There is also a rotary type where stainless steel pins are used. Those tend to be bigger, more expensive and proper canditates for build.

Tumbler is the easy part. Took a while to find a supplier for 5 + 5 kg of abrassive media. One for deburring (plastic loaded pyramids) and one for satining (small ceramic cylinders) and some tubling "oil".

Pekka

Offline mc

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Re: The Sequel - Oh Blimey I bought a CNC Lathe (Beaver TC 20)
« Reply #868 on: August 16, 2019, 04:19:21 PM »
I took the easy option and bought one of these - https://www.frost.co.uk/motor-parts-vibratory-tumbler-rust-remover-polisher-8kg/ as there was nothing else available that size for as cheap.

I made sure buy the media elsewhere though, as Frost was really expensive for it compared to the industrial suppliers.