Gantry is jerky...

I've been having a time with my ShopBot. The gantry movement isn't very fluid and is causing irregular cuts. It isn't real apparent in wood, but when I am cutting plastics it's very apparent. Cut speed makes some difference, but it's still there cutting at .5 IPS.

I haven't determined if it is a single axis or a combination of the X & Y. Everything seems to be adjusted right. The rails are clean and everything is lubed.

Is there anything I can check or adjust to get rid of the excessive movement?

Aaron,

For sometime I had excessive amount of chatter marks even when using a new 3-1/4 hp PC router. The bearings in it finally failed and when I mounted another new PC router the amount of chatter mark were reduced alot. Conclusion: bad bearings in the first router.

Could this be your problem?

Aaron, suggest that you start out by testing the SB on another PC that is slightly higher spec. than the one you are using at present.

I had the same problem and I tried running in DOS instead of windows and for me that cured it.

I had a problem similar to your gantry problem. The allen head set-screw on the pinion gear was slightly loose.... The mis-positioning was pronounced in just one axis and one glitch for every revolution of the stepper motor.