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Lathe Handwheel Over-Run

Posted: Mon Jan 22, 2018 9:17 pm
by tblough
When making fast handwheel movements on my Oak conversion, the handwheels appear to have a significant amount of over-run after the handwheel input has stopped.

I noticed in the PLC program that the MPG input has code to disable "Windup" mode if x100 selected. Is it possible to create something like this for the dual handwheels or is there some other setting I'm missing?

Re: Lathe Handwheel Over-Run

Posted: Wed Jan 24, 2018 1:24 pm
by tblough

Re: Lathe Handwheel Over-Run

Posted: Wed Jan 24, 2018 2:09 pm
by frijoli
What happens if you turn the wheel slowly? I don't believe this is over-run, but the carriage catching up.

One turn of the MPG puts out "x" pulses. The carriage moves that far at whatever speed it can until it catches up.


Re: Lathe Handwheel Over-Run

Posted: Wed Jan 24, 2018 5:10 pm
by cncsnw
By the PLC logic, it should enable "windup mode", where it will respect all requested increments and complete them before stopping (even if you stop turning the wheel sooner), only on the x1 and x10 increments.

Does it appear to run on significantly on the x100 increment, or just the x10 increment?

Part of the issue may be the leisurely accel/decel rate: perhaps it needs some distance to come to a stop, even once it recognizes that it needs to stop.

You should be able to cut your accel/decel time from 0.50 seconds down to 0.25 or 0.20 seconds. That should give you much crisper start and stop.

Re: Lathe Handwheel Over-Run

Posted: Thu Jan 25, 2018 4:25 pm
by tblough
The run-on was most significant on the X100 mode and dropping the accel down to 0.2 made a huge improvement. I looked at all the velocity mode tuning TSBs and the two drive tuning videos for Centroid out on the 'Tube and nothing mentions adjusting Accel on the PID screen. In fact, there seems to be very few resources available for velocity mode tuning for the Centroid controller. I'm going to go back and play with Accel, Kp, Kd and Kv1 this weekend.

TB234 has you adjusting Ki as part of the tuning procedure, but on my control, Ki values are grayed out and cannot be set. Are there any other resources available for velocity mode tuning (including Accel values) that are more up to date?