Ovals - not circles

[bob]

I've been using my Shopbot for several years - moved from the cable to R&P about a year ago and have had no problems. All of a sudden, circles are being cut as ovals. The file can be defined in Vector or directly through the cc command. A 2" circle is about 1/8th " out. I've checked to make sure everything is tracking properly, is tight, and have checked the bearings in the router. Any ideas?

[mbass]

Bob just a thought. Try the VU command and check that your ratios are correct. (127.324 X&Y for the 20 tooth pinon) I think that the ones in the manual are incorrect. I hope this is correct info.

[davenadeau]

Bob,
Check to make certain that the set screw(s) on your pinion gears are still tight (assuming, of course, that the Xscale and Yscale factors of the CC command weren't inadvertantly changed from 1.0 as you would to create an oval). A motor shaft rotating inside the pinion gear due to a loose set screw can create the pattern you described

[bob]

Thanks for the input. My X and Y are set to 127.324, my pinion gears are tight, and the cc command is set OK. Looks like this might be an issue for ShopBot. Perhaps I'm missing steps similar to the problem being discussed elsewhere.

[bill.young]

Bob,

Does it just happen with the CC command, or is it out-of-whack for all moves? If it's in all moves, could one of your motors have shifted so that the pinion wasn't engaging in the rack correctly, giving you some slop in that axis?

Bill

[bob]

Hi Bill. No it was happening from my files so I did a quick check with the cc command so everything would be eliminated except the base command insofar as the program was concerned. I'll check tonight and see if the problem is as you described. Thanks.

[bill.young]

Bob,

FYI, there's a tech bulletin in the "From ShopBot" section of the forum about this that may be of help.

Bill