Re: [CAD_CAM_EDM_DRO] Re: PID setting in EMC

Tim (and others),
I just talked to Mariss. It turns out it was the high encoder count that was affecting the gain setting on my G340 drive. The gain of the PID loop is increased with an increase in encoder counts. Since my encoder has 2500 lines (10,000 in quadrature), I need to use a much lower setting on the gain pot (almost all the way counterclockwise). If my encoder was 500 lines like yours probably is, my gain would be five times less. This makes me feel a lot better. I should have been happy anyway...I am getting 240ipm rapids with my motors and the G340 drive. Anything faster on this size mill and I would probably have to do laundry.
Richard

Tim Goldstein wrote:The uneven pulses from steppermod.o are not an issue at all with the
G320/G340 drives. They are only a concern if you are using a stepper drive
that does not generate their own smooth pulse train (so all steppers except
G210 and even the G210 can be affected if running other than the 10x pulse
multiply mode).

I am using very large servo motors with my G320 drives (roughly NEMA 42
sized) and my setting are about mid scale on the dampening and gain and wide
open on the current. How old are your G340 drives? The newer ones have an
anti-dither circuit that keeps them quiet at rest. On the older drives they
would sit and dither fairly rapidly with quite a buzz at rest when set
correctly.

Tim
[Denver, CO]

> I am also using the Gecko G340 drive with some rather large servos. I

have only tried steppermod so far, and it seems to work ok. I agree that
there may be some issue with uneven pulse trains.

> On a side note about the Gecko G340 and larger motors, where do you have

your gain and damping pots set to? My motors go into bad vibrations unless
I have the gain set very low, with the damping set just above it. I
understand why you would get vibrations or oscillations if the drive was
underdamped, but I also get it when it is overdamped. Is having the gain
pot set to almost minimum ok?

> Richard

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