The Craftmans Shop > New from Old
The Sequel - Oh Blimey I bought a CNC Lathe (Beaver TC 20)
awemawson:
As is the way with these things it's one step forward, one back !
Last night I was experimenting with MDI and tool changes. I selected tool 10 and the machine did it's thing rotating the tool turret. It pushes the tool disk forward, rotates to location, then moves it back - I assume that there is a Hirth index disk (*) which it then precisely locates on. I then told it to select tool 5 (where we had been before) - it completed most of the move but failed to finish, and the tool disk looks to be 4 mm too far forwards, as the coolant pipe no longer reaches the port on the rear of the tool disk by that amount.
As a slight consolation I did get the tailstock moving out and back under program control !
So major investigation into the Turret. I removed as many covers as I could and managed to gain access to the internal terminal box where the 'position sensor' leads terminate - these are proximity sensors running off 24 volts (which is there) but oddly all four proximity sensors are saying 'no detect' - I'd have thought one or two would be active.
While climbing all over the turret I had opportunity to examine the Turret Crash damage that I'd known it had suffered in the past. Seems to be just to the tin work, and a bit of tin-smithing should sort it out.
Likewise the swarf cover above the turret was somewhat rusty so got cleaned up.
All a bit of a set back - but these things happen - I suspect I'm going to have to get at the inside workings of the turret - just not sure how yet :scratch:
(* Hirth Index disk looks like a flat bevel gear with teeth facing forward, and mates with another identical one in any of N discrete locations dependant on tooth count)
awemawson:
Well an extremely frustrating day today :bang:
I managed, by re-wiring hydraulic solenoids, to unlock the turret, allowing me to turn it manually and set it in the correct position, thus being able to initialise it - hooray. I could then select tools at will, jog where I wanted, and spin the spindle at great speeds forward and reverse.
However, once turned off and back on I couldn't even jog, the control reporting a fault with the KTK Mentor. Now I've been through EVERY wire into and out of the Mentor, documented them and inspected any that might report a fault. None do, and the drive says it's ready on it's front panel.
BUT - if the power to the Mentor is dropped and remade by dropping out it's isolator the fault very occasionally clears :scratch:
Once this fault is cleared I can jog as I wish. So two issues to bottom, the Mentor issue and the Turret issue - I did at least manage to winkle circuit diagrams for the Turret SMCC servo card out of Delta Tau in California today :thumbup:
I think tomorrow I will log the voltages on all 41 of the Mentors interface connections with the fault 'ON' and try to clear it and repeat the logging - hopefully that will show how the controller knows that there is a fault :scratch:
. . . meanwhile I'm going to finish off this bottle of Pinot, I'm sure things will look better after that :clap:
charadam:
Andrew, I'm curious.
Is this normal for machines of this vintage?
I mean, apprentices in a cold shed throwing components from 5 yards and installing them where they fall?
Or is the component layout and circuitry designed with no concept of maintenance or fault finding.
awemawson:
You have to remember that this machine has sat un-powered and unused in two locations over the past 10 years. Things deteriorate, connections corrode and problems are bound to emerge as it is brought back into commission.
It's not untypical that one fixes something only to find another issue emerge. Hopefully as I progress and a few hours are put on the clock (which isn't working by the way !!!!) the reliability will increase.
awemawson:
Another day going round in circles, but I've reached a tentative conclusion. But before I reveal that I took a break from diagnosis (to preserve sanity!) and did some metal bashing.
You may recall that when I pulled the turret apart, one of the complicated covers had suffered a collision with the tail stock when at the University. I was quite badly crumpled and unfortunately someone had welded up a crack on the corner while it was in the crumpled state. This of course makes a repair far more difficult.
I'd thought that with a good heating from my 'Rosebud' tip on the oxy-acetylene torch I could get most of the panel a dull red and tap in back with a hammer on the steel welding bench. No way :bang: I did manage to get the folds 'pointing in the right direction' so I decided to use the 60 ton press to flatten it. Worked quite well. I may well cut off the welded corner, and weld in a new folded piece - but I can't do that until the rest of the tin work is back to give me something to measure to.
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