Roughing Pass in PVC... How Can It Be Done?

[ChrisInEstes]

I don't see a built in way to do a roughing pass with PVC. So, what's the best way to do that?

My process: I convert the whole image to a grey scale .bmp in my design software & bring it into PVC, create tool paths, then bring the tool paths into VCP for routing from there because I want a start depth of 0.125", and I have other routing to do on the piece.

When I pick a larger ball mill, and create a tool path, the preview shows parts of the image cut into (X & Y Axis') further than I want. When I pick the final size ball mill and create the tool paths, the preview shows those same areas not cut into as much. So, it seems that the smaller the ball mill I pick, the more like the original artwork it is. I don't see a "tool offset" setting in PVC either.

The piece is 16" x 20" and the max depth from PVC is 0.25", and with the additional 0.125" start depth from VCP, the total depth of cut is 0.375". That's too much for the 0.125" ball nose bit to do in 1 pass. I figure it's a 3-pass job with the 0.125" bit. Should I do a 0.125" deep pocket with a flat end mill in VCP before I run the PVC tool paths? Should my pocket pass be 0.115" deep instead of the full 0.125"?

Am I asking too much of PVC & VCP with this job?

I've attached a full scale eps version of my artwork... (No Copyright violation) I also attached a 1/4 scale jpg version of the bmp (because .bmps aren't uploadable here) as it is when I open it in PVC.

Thanks
Chris