Problem with Curved Shapes

[chodges]

We have a fairly new (January, 2008) PRS Alpha with a 4hp spindle.

When we cut out shapes, the straight lines cut straight, but curves cut with badly staggered edges. We have also noticed that if we are cutting material that requires that we make more than one pass, even the straight lines have issues: you can easily see "steps" on the edges where each successive pass was made.

We are usually cutting thin (1/16" to 1/8") plastics, but these issues are more apparent when we cut something like 1/8" thick aluminum.

We have tried drawings originated in AutoCad, Corel Draw, FlexiSign, and ArtCam - all with the same results.

We have also made sure our material is securely held down so it won't move.

Any ideas on how to improve these cuts?

Thanks!

[kerrazy]

what is your error tolerance value set at. It sounds like you are sending line segments rather than curves. You could increase tolerance to .0001 and use an arc support output file, to help get smother curves. THat is about it from a software standpoint, after this it is typically mechanical in nature.

[myxpykalix]

try using the "shopbot arcs inch" postprocessor when saing your cutting files. That might help

[chodges]

I found the problem!

I sure wish there was some way I could blame this on somebody else, but it's just my fault ...

Back in January when we were putting our ShopBot together, we decided to leave the set screws on the motor gears loose until further along in the assembly so we could better determine how much the gear should stick out beyond the end of the shaft. We wanted to engage the pinon as best we could without rubbing the aluminum rails.

Guess what? We never remembered to go back and tighten the set screws!

We did this yesterday, and now our machine cuts beautifully!

Thanks for all the good advice!