The Sequel - Oh Blimey I bought a CNC Lathe (Beaver TC 20)

[awemawson]

The ironic thing is Cliff, I just tried the MP12 probe and holder in the machine, and the IR of the OMM isn't reaching the window of the probe. 

The MP12 is intended for the vertical spindle of a milling machine of course.

All is not lost, as the probe mounting is universal to a few Renishaw probes, and I have another (an LT02S) that has the window pointing in the right direction !

[awemawson]

Sometime these 'Gotcha's ' creep up on you unawares. Looking at the two probes side by side it is dead obvious that their windows point in opposite directions, outwards and left for the LT02S for a lathe turret, and upwards (if in a spindle in a mill) for the MP12

I've handled these things numerous times but the fundamental difference never dawned on me.

Oh well, honour redeemed by mounting the LT02s on yesterdays adaptor and I've proved that it works as fitted.

[tom osselton]

Glad it worked out! So why the difference in window direction? Or is that dependent on where the receiver sensor is positioned?

[awemawson]

The "Wrong" one is intended for the vertical spindle of a milling machine so the window points upwards with the OMM sensor at a highish level out of the muck and bullets.

Theoretically I could have moved my OMM to the roof of the enclosure but in practice the sliding door curves up there and stops that being  a solution.

[tom osselton]

Ok that’s what I thought my Son had ours moved from the right side to the left to accommodate the 4th axis on the Haas.

[JHovel]

Andrew, reading your exceptional progress with great interest.
Could you use a mirror to redirect the IR signal back to your sensor? While probing, I imagine there would be no coolant interfering with the mirror. Perhaps mounted high in the enclosure (even near the top of the door) might just work....
Cheers,
Joe

[awemawson]

Joe, I had considered making a prism that would sit on the existing window but 'look the other way' , but I'm not sure what optically clear (at IR wavelengths) plastics there are that are available, easily machinable, and able to be polished

Today I started gluing up a wooden box to house the LT02S probe and holder, and 3D printed a cover for the ruby probe itself. Hopefully tomorrow the PVA will be set enough to finish it off and fit catches and hinges. I used the offcut of the 12 mm ply that I got for the counter top of the Versatool cabinet. What horrible stuff modern plywood is - looking at the cut edges it was full of voids.

 

[awemawson]

So while the first coat of varnish is drying I did an experiment to see if the MP12 probe would work though glass. Casting about for glass in suitable sizes I came to the conclusion that it is surprisingly rare in my workshop 

Eventually I settled on my 100 mm  magnifying glass that sits at my desk - it has the advantage that the glass is pretty thick.

End result is that the probe is quite happy to function both sending and receiving through the glass, so I've splashed out and bought some small prisms on eBay. Coming by slow boat from China so not expected until the end of the month. To get the size right I need to mount two 10 mm x 10 mm x 10 mm next to each other so a bit of fiddling required.

I seem to recall that there is a special optical glue used for lenses in contact, but actually I don't suppose it'll matter in this case that half the signals go through one prism and the other half through the second one 

[charadam]

Canada Balsam used to be used for lens gluing, but has been superseded by synthetics.

[awemawson]

That's the stuff 

Not to be confused with Friars Balsam 

[nrml]

Friars balsam smells wonderful. If someone accidentally spills some at work, everyone in the area drifts that way to have a sniff.

[awemawson]

At long last the sticky backed green baize to line the Renishaw Probe box arrived this morning so I was able to finish it off.

First I made a closed box, pinned and glued which was left for the PVA to set hard. Then the closed box was sanded down to a fair finish which revealed the rubbish quality of the "12 mm 7 ply" that I was using. It turns out that actually it's 9 ply, with the extra two plys being paper thin and effectively just colouring at 5.5 thou thick! Bits got sanded off which proved to be very difficult to disguise with the stained varnish that I used.

Then the box was sawn into a top and a bottom, thus ensuring that they matched in 'unsquareness' though in fact they were pretty good.

Umpteen coats of dark oak varnish stain later I was able to fit the hinges and corner protectors. With water based and oil based paints I always suspend my brush in water to prevent it drying out over night, as it easily shakes / wipes dry ready for the next coat. Saves ages washing brushes

[awemawson]

And then this morning the baize went on. Knowing this stuff is great fun even on open flat surfaces, I thought that I'd be clever and make a paper template. It 'sort of worked' but this stuff stretches all over the place and when it's 'down' it stays down resisting movement. I'm not entirely happy with the result as it's not absolutely flat in places but it's definitely functional.

Some time earlier I had 3D printed a protective cap in ABS that slips over the actual probe itself, preserving the ruby tip (hopefully!)

[awemawson]

When I got this lathe it was evident that the main reason for it's demise had been a leaking Lithium battery used to back up some of the RAM within the controller, and it's leaking fluid had done major damage to the electronics, dissolving away copper track, i/c pins and the aluminium extrusions of the card cage.

I had always intended to re-locate the batteries (as there are two) to a place where were they to leak again no damage would be done, and to this end I had obtained a spare battery holder like the existing one so that rather than have a large button cell on a card and a C size cell in a holder, there would be two C sized holders remotely wired.

The problem was that the original rather over complicated battery holders were a pain to mount in an appropriate place low down so that leakages would be less of an issue. But then it dawned on me, If I used a pair of conventional panel mount cylindrical C cell holders, and put them in a plastic box such that it would contain leakage then where it was mounted became far less critical.

So an acrylic box and a pair of Bulgin battery holders were ordered from RSComponents and assembled.

First picture is of the original RAM card that was totally destroyed by the battery leak

[hermetic]

Very neat Andrew! Could you not (if needed) put another battery holder in parralell, or switched in, so that you could fit a new battery before removing the old one, or have you engineered out that memory volatility now?
Phil

[awemawson]

Now part of the delay in making this modification has been that I wasn't prepared to risk damaging my replacement RAM card, and I had been waiting until another one became available. This happened a couple of days ago, so I went through an exercise of backing up and restoring to the new replacement card and running it for a few days to prove it was OK.

Removing the "Button Cell" was easy enough, but then I had to attach a flying lead running to the new box while providing cable restraint and yet still be able to use the card extractor cover with which it is fitted. I say button cell, it's nearly the size of a beef burger ! I then used it's two negative plated through holes to mount a 'goal post' of stiff copper wire to act as a cable restraint, passing the wire through a hole that I drilled in the extractor cover.

[awemawson]

Next it was the turn of the C size battery that (very oddly) slid into a holder in the rear of the VDU monitor and was wired from there to the back board 

I decided to solder wires to my spare battery tray, leaving the other wiring undisturbed, and in doing so revealed a totally undocumented fuse wired in series with the battery. My modification keeps this fuse still in circuit

[awemawson]

 So now we need somewhere to put the box. I made up a shelf that is suspended from the 'roof' of the metalwork that houses the Siemens controller, and is in such a position that the battery holders CAN be accessed from the removable service panel without totally removing the 820T controller, unlike the previous design.

Usual thing - drawn in Autocad, exported to SheetCAM, plasma cut on the CNC Plasma Table by Mach3 and given a zinc rich primer and matt black top coat. Drilling it's mounting holes was 'interesting' from within the small space, but I had installed hank bushes in the shelf, so screws could be accessed from above and outside the enclosure.

It was then a case of plugging it all together, doing (hopefully) one last re-load and testing that the machine still works (which it does).

Now, with the power on, I can remove either or both of the batteries and replace them, and if I need to totally withdraw the controller, the battery box can remain connected, and come with it still retaining RAM

The shelf has a front lip upstand to prevent the box ratting off, yet allowing it to be tilted for planned removal

[awemawson]

Very neat Andrew! Could you not (if needed) put another battery holder in parralell, or switched in, so that you could fit a new battery before removing the old one, or have you engineered out that memory volatility now?
Phil

Phil,

The original (Beaver) design precludes that, as you can't actually get at the batteries, but with my new layout I can easily get at them while the power is ON thus RAM data is retained.

[RussellT]

Very neat!

Your problems with sticky backed baize reminded me of a technique I have used effectively a few times.  I discovered this when attaching golf club grips to a dinghy tiller extension.  Golfers use double sided carpet tape and stick that to the club and then wet the grip and tape with white spirit and that makes the glue really slippery so the grip just slides on.  I have adapted this when trying to position sticky backed tape inside the dinghy centreboard case.  Wetting it with white spirit makes it easy to slide into position.  I wonder whether this would work with the sticky backed baize.

Russell

[awemawson]

So yesterday and today I've finished off a job that was started back in November last year, but was put on hold when my Renishaw parts got hi-jacked in Australia. PK still isn't answering emails, but I decided to finish the job anyway.

Objective was to replace the retro-fitted Renishaw OMM / MI12 /  Siemens 820T  wiring, as it had been draped on the floor and not run in the conduit. And at the same time wire the MI12 interface box via plugs and sockets to make it removable.

Back in November I'd made up a box, fitted it and wired three XLR panel mount plugs / sockets, and laid the multi-way cable in trunking or Adaptaflex as appropriate, and got the OMM cable as far as an adaptable box on the end of some flexy conduit awaiting the return of the OMM from PK. In the mean time my bacon was saved by another member (thanks Cliff) who was able to let me have a replacement OMM to get me back on track.

Firstly I made up three 'umbilical cords for the MI12 interface (To OMM socket, To 820T controller Socket, and To 24v socket)

Then I fitted shoulderless boot lace ferrules to the OMM cable that I'd coiled in the adaptable box, and dismantled the OMM from the bulkhead and re-wired it using the new cable, with the conduit nut retaining the box on the bulkhead. Why shoulderless? The ones with shoulders won't fit through the OMM entry hole !

[awemawson]

Then it was a case of removing the original wiring from the MI12 interface, and attaching the three umbilical cords. Once that was done the controller had to be slid forwards to access the interface card that accepts the two probe contact closures, and re-wire it's connector to my already laid in cable.

Fingers crossed and power was put on and both probes tested and thankfully worked fine - they should of course as it's only a simple wiring replacement, but you never quite know what you are going to disturb in the process.

Once I was happy all was working it was just a case of carefully removing the original cables, again without disturbing anything else, or tearing them to shreds on the bare holes without grommets that they'd been threaded through 

[awemawson]

Having yesterday completed the outstanding wiring modifications there "SHOULD" be no more need to have the Siemens 820T controller and Operators Panel floating about unfixed as now there shouldn't be any more requirements for access by pulling it out.

It's been loose since the day the machine arrived and I pulled the control forwards for investigation - that was 12th May 2018.

I've seen countless pictures on the Interweb of these controllers with broken front panels and I'm not at all surprised. They are plastic and if you are not at all careful removing and installing puts far too much strain on the fixing flange which promptly breaks off. I was lucky - there was only one corner broken on mine from the Operator Panel, and the broken bit was still there and able to be re-glued. But the corners are incredibly vulnerable until all screws are bearing the weight. I think it is probably sensible should future removal be needed to remove all corner screws first, then the others.

When I was removing it on the day it arrived, unbeknown to me there was a hidden floating captive nut bar that greatly confused me getting the controller out despite the fact that all it's screws had been removed - easy when you know !

So, 820T screwed back in (14 screws and two bolts in the captive nut bar), Operator Panel back in (10 screws - careful of that glued corner!)

Now another dismantling puzzle had been how the end access panel was retained - answer inwards projecting welded on studs with brass inserted Bakelite knurled hand screws thoroughly stuck and requiring the use of pliers to unscrew at an unbelievably difficult angle for my hand - I seem to remember dropping at least one set into the machine that day. So when they went back on, each stud had a dab of 'Copperslip' hopefully to prevent such things in the future and allow hand unscrewing. I suspect this issue was made worse by the fumes from the lithium battery when it had died.

Then the filter retainer and filter and the machine is completely back together 

Now I can play with it without feeling guilty that there is still outstanding work to do 

[awemawson]

It was only gong to be a little job 

Remove the hard jaws from the chuck, mount up a set of three soft jaws and bore them for gripping 25 mm - how hard can it be 

It certainly started off well. Clamp the spindle to give something to torque against, out with the big allen key and unbolt the hard jaws. Stamp up the new soft jaws so we know what goes where in the future and fit them.

This is where it started to go down hill - the new jaws are too long to fit without overhanging the outer circumference and only using one retaining bolt - and this I was NOT prepared to do.

Looks like I'll have to start profiling them in the milling machine and finish bore them on the lathe - a bit of a pain

[awemawson]

So having drawn them up in AutoCAD to see what is what, I then transferred to FeatureCAM to generate a face profile for the jaw nose, deciding to have an initial 20 mm bore to let the boring bar in on the lathe.

Now with the 20 mm initial bore that dictated the largest diameter end mill that I could use (19 mm) and as these jaws are 50 mm deep and pretty tough I was somewhat concerned with endmill flex.

I wound the feeds back considerably from FeatureCAM's defaults but try as I may I could not eliminate horrible chatter within the 20 mm bore. In retrospect I think it was that the chips only had a narrow gap to escape, but in the end it really didn't matter as it was going to be finish bored on the lathe