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

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awemawson:
Well that last video was pretty useless - out of focus and still from a difficult angle. Hopefully this one is somewhat better:

I get the impression that there is still a slight settling clockwise on clockwise tool changes, but not so much on anticlockwise moves :scratch:

Proof of the pudding will be tomorrow morning when it's cold again I suppose

awemawson:

--- Quote from: WeldingRod on February 10, 2019, 03:57:00 PM ---Excel spreadsheet. Weigh all your tools, do the combinatorial thing (12 factorial or 12 × 11 x 10 x...) for lines, 12 columns for.positions, then do a net moment calculation for each opposite pair, and sum it up. Lowest net moment is your best choice.
Or, just take the weights and match the heaviest ones across the disc.

Sent from my SAMSUNG-SM-G891A using Tapatalk

--- End quote ---

Not quite so easy Rod, as the mass of the tools act from different points due to their differing shapes, which is why I went on to consider the 'analogue' approach using a mocked up disk.

awemawson:
Proof of the pudding will be tomorrow morning when it's cold again I suppose

I'm pleased to report that it's passed the 'cold test' this morning, behaving right from the get go :thumbup:

However last night I went through the various circuit diagrams and worked out the anomalies in the numbering scheme for the 'offset' adjustment, how to disable the servo brake (not mentioned in the book procedure!), and to the disable the X & Z axis so they cannot move. So if I get time this afternoon I'll see if I can perform the procedure.

hermetic:
I agree, that little extra move to get final alignment doesnt look right, partly as you say, because the movement is unequal in the different rotations, from my simplistic, completely non cnc point of view, could there be some small amount of slop in the servo drive system, like a slightly loose pulley, or a partially sheared key, caused by the machine crashing, which the alignment system is compensating for, I suggest this because many times in my life, looking for a complex answer to a relatively simple problem has always come back to bite me in the arse, especially if I have assumed that the fault always lies in the most complex part of the system, ie, the damned electronics!
Phil

awemawson:
Now I've roughly tweaked the 'offset' the Curvic Coupling seats nicely each time, so although I agree it could easily have been something 'a bit loose' it almost certainly was that the offset was wrong.

If you watch the last short video "Turret Exerciser Better Angle" you'll see that the servo hunts either side of set point then when on station fires the lock solenoid pushing the two parts of the curvic into mesh, and at that point there is very little (if any) relative movement implying that not only was it at set point, but that the set point is correct.

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