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

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vtsteam:
This kind of thing seems all to familiar! My thoughts are with you, Andrew. You'll crack it, I'm sure. :beer:

awemawson:
Thanks Steve for the kind words.

At last I can report a little positive progress. I've spent the last three days going round a logical loop regarding the Axis Enable Line not being asserted. This involved 'fault' outputs from the internal Simodrive servo drive supervisory card reporting the error (yes I know it's not enabled - is that your error?) feeding into the 810M CNC controller 'PLC' logic where the signal to enable the drive unit emerges. So it's a circular argument and rather reluctantly I decided that somehow I had to break the circle.

It is fortunate that I spent months on end decoding and mapping out the PLC program several years ago - it was a big help.

The method that I chose was slightly risky (*) - remove the 'fault signal' from the PLC and drive it to a clear state to see what happens. Sure enough the 'Enable line' goes to the correct state (24v) and I can jog in X & Z axis's . A slight oddity was that the fault line had to start at 0 v then go to 24 v - presumably to satisfy some sequence needed by the PLC.

(*) risky in the sense that these are powerful servos reporting a fault so may not behave benignly.

So I deduce that the error is within the Simodrive not the 820T - most likely one of the two dual axis pre-drive cards. There is the supervisory card that I've mentioned (and changed!) that sources the error signal but it has monitoring circuitry looking at the pre-drive cards, the power drive cards and the power supply. Sadly card changing is pretty involved - not only loads of plug connectors but also a fair number of bolted high power connections for the servo motors themselves @ 40 amps. as well as numerous option settings on daughter boards.

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Just need to get down to it

awemawson:
Well that's two cards exchanged in then back out with no change :bang:

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Ah well I suppose it's now down to the power drivers

awemawson:
Well if I wasn't confused before I certainly am now!

I went through exchanging each of the analogue servos cards in turn using spares from my 'Christmas Tree' spare controller and in each case when the symptoms stayed unchanged re-installed the original

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Then I went through exchanging the power driver cards - again one by one and returning the originals when symptoms were unchanged.

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At this point I thought that I might as well return the supervisory card that I'd swapped out on the 13th. This is when things got very confussing. The green LED saying that the servo system wasn't enabled went out, and initially I could jog in X&Z however the machine started giving D to A error in X&Z and the X axis started moving the turret upwards but the motor was growling and the machine reported X clamping issue and went into eStop.

Had enough for today - yet again going to lick my wounds indoors!

vtsteam:
My guess is it's a Gremlin. Do you have rat trap you can put in the main cabinet at night? Bait it with a working Android cellphone, or a string of series connected incandescent Christmas lights. Bound to be some action overnight. :dremel:

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