Problem cutting arcs and circles

[jay77]

Wondering if anyone can give some advice.  Finally got my old CaMaster machine running about a month ago.  It needed some rewiring, adjusting, and new software.  The problem is when cutting a circle or arc I get a jittery, or whatever you would like to call it, result.  The circle is the right average diameter and from a distance it looks good but there is a fluctuation of +/- .040" along the edge.  The error is not consistant, I cut an O ring grove inside of a circle just to make sure.

The first circle I cut was very jittery but then I realized the feed direction was CCW and the spindle rotated CW.  The feed direction is now CW along with the spindle and the result is better but still not perfect.  I am using the Galil plug-in with linear interpolation checked under move settings and have tried different vector time constants and buffer levels settings to no avail, actually not much difference at all.  I have adjusted the motor tuning and kernel speed in Mach3 and tuned the servos (PacSci) with WSDK from Galil but as this is my first experience setting up a machine, I'm not sure everything is correct.  The gantry motion (axis A slaved to axis X) and Y axis are pretty smooth but not perfect.  The Drives (PacSci) are set to torque mode as recommended by Galil.

My first attempts cutting a circle were with G-code from Lazycam, then tried the circle wizard found in Mach with about the same results, maybe a little better.  I'm just hoping this is not a mechanical issue but after all the tweaking I fear this may be the case.

I also have an intermittent problem while jogging, sometimes the X axis decouples from its A axis slave.  A resest in Mach usually corrects it.

Any help will be greatly appreciated.

[Hood]

Best bet is to ask in the Galil part of the forum, obviously an issue if the slave is losing connection. This could be related to the rough motion as well although it could also be tuning or possibly even lack of rigidity. For the rigidity try cutting again on the same path you have cut so only a small amount of material is being cut, also go at a fairly slow speed and see if it looks better. If it does then it would seem like rigidity is a problem.
Hood