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

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  :ddb: :ddb:

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

awemawson:
It was only gong to be a little job  :bang:

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  :scratch:

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
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