Skin cutting, acrylic

[clockmaker]

I am cutting clock dial parts out of 1/8" acrylic,and need to leave the bottom masking paper intact to hold the parts. I zero my Z axis to the table and set my plunge depth to a point just above the table the thickness of the masking.
My problem is that I'm getting inconsistant cuts, sometimes cutting all the way through the masking, sometimes leaving a lot of material not cut ( only several thousands, but a pain to clean ). ANY IDEAS OR SUGGESTIONS ?

[billp]

Doug, I have done similar stuff by using a foam backer board, and then placing double sided tape on the entire back of my piece. Then you can try to zero at the table surface (in this case the faom board..), and give it a very fine offset on top of that. This way even if it cuts through, the double sided tape holds the pieces in place.Only problem in the past has been that after a lot of pieces I sometimes get a buildup of the tape which I can clean off by either pausing the machine and wiping off the bit, or just touching the tip of the bit with a thin piece of wood while it is still running..How small are the pieces you are trying to cut? Bill P.

[gfacer@istar.ca]

The best way to do this is to add extra masking on the back, like sign pre-mask. A more accurate machine (like mine techno-isel), can get away with only the backing paper. Your table must be extremely level and stable to make this work at all. The light weight of the 1/8" acrylic doesn't help either. BTW, if you're not using vaccuum, it probably won't work at all.

Greg Facer, Industrial Plastics