The Craftmans Shop > New from Old
The Sequel - Oh Blimey I bought a CNC Lathe (Beaver TC 20)
PekkaNF:
Line #19 "Set resiprocation speed"? Is it explained aqnywhere? Is it overshooting speed? What will happen if you set same than approach speed? I would test that 40/50/60 values (If set speed is 50) and see if overshoot characteristics change. I guess if you set it zero, it goes only one way and either stops inside the error or overshoots and stays there.
The reason I though it has cascade controller is that in that era they often did and this comment
--- Quote from: cnc-it on November 02, 2018, 12:16:33 AM ---Also on the Mentor drive there are pots for tuning..I used them for setting the rpm after I had my motor re built..worth a try?
--- End quote ---
Other reason for pots are discrete error signals from analog system. Is there a feedback loop from the motor (position or current) in the Mentor drive?
Pekka
awemawson:
Pekka, the reciprocation speed is used for lathes like this one with gear boxes, to let the gears 'rock in' as you change gear.
It is, you are quite correct, a 'loop within a loop' as the Mentor is handling current through the armature to achieve a set speed looking at the tacho, and the 'Measuring Card' is controlling the analogue signal to the Mentor to achieve in this case a set position, but normally a set speed.
Hot off the press when the system has failed to achieve position and is in it's 'deadband' I can measure a signal in terms of a few tens of millivolts supplied to the Mentor to turn, and if I rotate the chuck by hand to the other side of the set point, the polarity of the signal reverses. So I conclude that the measuring cards KNOWS it's not where it should be, but the Mentor doesn't respond to such small signals. Now I assume (dangerous) that were the gain set higher, the 'error voltage' would also be higher, so the next job is to wire a DVM back from the Mentor to the console so I can see the effect of changing parameters in real time.
. . oh what fun :ddb:
cnc-it:
So Andrew does the spindle have a brake to keep it from moving when milling and drilling etc ..and could you mill a large square thread for example by rotating the spindle and feeding the turret in the z axis..?
awemawson:
The M20 'preparatory function' for the M19 takes the brake off if it was on, and asserts 'Spindle Enable' and 'Servo Enable' . Once the M19 function gets to target it applies the brake, and removes 'Servo Enable'
Yes the possibilities are endless once this facility is functioning faultlessly. I still need to modify the drive arrangement for the power tooling to actually be able to use it, but things are getting closer :ddb:
cnc-it:
Yes when you think of the possibilities especially with the tail stock for holding long parts :jaw:
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