Axis DC servo drive adjustment on 6MB

[Andy Fritz]

Hi Guys,

I just replaced the X axis drive and top PCB on my Hitachi Seiki VMC. The drive amp p/n is A06B-6047-H003, the top PCB p/n is A20B-0009-0320/15E and the motor is a yellow cap DC 10M with pulse coder.
I just copied the jumper and trim pot settings from the old top PCB and I can run the axis and zero return so it seems to work ok. However I do notice that the X is not as smooth as it was before. It seems like the acclereation and deceleration is too fast as it nearly "jumps" into action.

I have a maintenance manual for a Fanuc 10T control which has a section on how to set up the top pcb trim pots, but it just gives the nominal positions which are 50% on most. I am sure there must be a more accurate way of doing this and I saw some other threads about it. Unfortunately they where describing other controls or top pcb's and I dont want to mess with this unless I am sure a description is applicable to my control and top PCB.

I have not yet done any tests to see if I can cut a perfect circle in Y and X yet. I would like to know if any of the trim pot settings can affect the measured distance of travel? Say if I make a 100 mm move in X + direction from the MDI, would any trim pot affect the actual distance travel by the X axis?

Also, I have seen "gain", "loop gain" and "velocity gain" in posts regarding servo control adjustment and in the maintenance manual. Are they the same?

There is one pot labeled "Gain" on the top board, but I think there are other "gain" related parameter settings. Are the trim pot setting and parameter settings doing the same thing?

I do have a good Fluke meter and I just bought an occilloscope but I dont know how to use it!

Any help would be greatly appreciated!

Cheers,

Andy

[MysticMonkey]

Have you checked the backlash and GIB friction ?

[Andy Fritz]

Originally Posted by MysticMonkey Have you checked the backlash and GIB friction ?

Hi Monkey,

Yes backlash is bad. About 0,1 mm in X. I have adjusted this out in lash comp and it does make the axis jump abit, but only at direction change. This was done before we swapped the drive and now it jumps in both directions.
I have not checked the gibs. After doing this on a small Taig mill that is the last thing I want to get into! Took days and never got it right. I do see your point. If gib is too tight the motor works harder and maybe this is the reason we had to change the drive.

Andy