The Craftmans Shop > New from Old
The Sequel - Oh Blimey I bought a CNC Lathe (Beaver TC 20)
awemawson:
Well it's even simpler than Pete's 999 . . .
There is a parameter (#170) which is a one bit flag to say if the level one security code has been set. '1' = set but mine is '0' which means that only one code has been set.
However although putting the code '149' in parameter #97 for level 2 security enables the mode button that theoretically lets me change 'bit' parameters, and lights it's active light up, in practise I can't change the state of parameter #167 'ramp enable' from it's present '0' to the required '1' :bang:
Presumably it's hard wired or linked somewhere to prevent it. . . . oh joy the complications of life :scratch:
awemawson:
So a bit of intensive parameter investigation today - I put together a document with the best description of each (apparently) involved parameter concerning the Spindle Orientation and M19 that I could find in the various description that I have.
Having done this it became obvious parameter #4010 wasn't really concerned - it is an offset to make sure forward and reverse speeds are the same, and a bit of experimental tweaking showed that actually it needed to be set to '0' - had been '2' and almost certainly has no influence on the oscillating issue.
Then I concentrated on parameter #4270 'Cut off speed for M19' - apparently the spindle is slowed down to this speed, and travels towards the set point until 'captured' by the servo action. Well it had been '5' in the parameters that I had been given, but the spindle never starts to move at all if set so low - 9 or 10 was the lowest at which I could set it and get the spindle to rotate towards the set point, so a bit of experimentation was needed.
Forgetting all about the M19 and simply issuing an M03 S10 command (M03 = rotate clockwise, S10 is the speed in RPM) gets the spindle slowly turning at 10 rpm and the input to the mentor is about 90 milli-volts. Issuing an M03 S5 the spindle won't turn, but the Mentor has an input of 41 milli-volts.
So I still think that the issue here is that for some reason the Mentor isn't responding to small inputs. Now the Mentor has an input range of -9.9 to +9.9 volts and it's internal A to D converter has a maximum count of 1023, making it's least increment 9.7 x2 / 1023 or 19.1 mV if I understand their description so would expect movement at 41 mV
Conclusion - well I don't have one, but I have learnt a bit more, but equally obviously there is more to learn :coffee:
mc:
Sounds like there's a deadband set in the Mentor.
I'm assuming you can view the AD value on the Mentor some how going by that bit text?
awemawson:
I awoke to the realisation that although I thought that I'd eliminated the Measuring Card by substitution, that was BEFORE I'd cured the M20 fault, so M19 wouldn't have worked anyway :bang:
So first job, swap the cards again. At first I though that it was much improved, but measurements showed that the card had slightly different characteristics but the fault (oscillation when set to the correct gain) was still present.
I then set up the 'battery box' to drive the Mentor having added a passive 10:1 voltage divider to it to get low enough values with enough sweep on the pot. Essentially all it did was reproduce my findings driving it from the Measuring Card, although it did show a small offset with speed differing by a bit between forwards and reverse.
Then I decided to increase the field current in the Mawdsley DC spindle drive motor. I had set the field coil driver to 3 amps using my Fluke clamp meter - (this won't necessarily give an accurate reading due to the waveform of the current but relative readings should be OK). The motor isn't marked up with Field Current on the plate, just a voltage rating of 170. I'd chosen 3 amps to be conservative as the field coil driver was running very hot, but I've put a fan on it since then.
Again there seemed to be a marginal improvement, nothing stunning. Eventually I tweaked the gain and the 'target window' setting to give a working state just so I could seeing it positioning, and wrote a little diddy program stepping round in 45 degree increments. As the target window is now quite wide the positioning won't be particularly accurate, but it is 'sort of' working, but needs a lot of refining.
Have a video:
russ57:
Those bangs are clamping and releasing?
Russ
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