Laser-cut fixture for milling polycarbonate
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Published on March 29, 2012
Description
I use a lot of polycarbonate, but unfortunately it's not laser-friendly, so I wind up milling it. I lasercut this fixture out of acrylic to hold 4" wide strips of 3 mm polycarbonate, a convenient stock size that works well in my Taig CNC mill.
It allows repeatable positioning (I can loosen the M6 bolts, slide more polycarbonate in, and tighten them again and run the same job without having to re-zero), keeps the material fairly stiff while cutting, and doesn't waste a lot of room with big clamps around the edge. NB make sure you have enough cutter length so the collet clears the M6 bolts at maximum depth. I run a 1/16" 2-flute spiral cutter at 600 mm / minute at top speed and it climb cuts nicely. Moving in the conventional direction I get strings of polycarbonate which wrap around the cutter and melt onto it, and scar up the work piece (circular scar in fixture at upper left side is an example of this).
It allows repeatable positioning (I can loosen the M6 bolts, slide more polycarbonate in, and tighten them again and run the same job without having to re-zero), keeps the material fairly stiff while cutting, and doesn't waste a lot of room with big clamps around the edge. NB make sure you have enough cutter length so the collet clears the M6 bolts at maximum depth. I run a 1/16" 2-flute spiral cutter at 600 mm / minute at top speed and it climb cuts nicely. Moving in the conventional direction I get strings of polycarbonate which wrap around the cutter and melt onto it, and scar up the work piece (circular scar in fixture at upper left side is an example of this).
Instructions
You will need 10 M6 x 20 mm bolts, an M6 hand tap, and some T-nuts to hold it onto the mill bed. This design is sized for A2Z Tuff Nuts and a Taig DSLS3000 CNC mill.
Laser cut. The perimeter hex bolts (M6) will go through all the layers except the one with no center cutout, that is the bottom layer. Use an M6 hand tap to thread those holes. Use T-nuts and appropriate bolts through the end holes (not sure of the exact length, I used some shorter #10-32 ones I got with the mill) to fix this plate onto the mill bed. Stack two of the plates with center cutouts, then the spacers (long thin bits), then two more plates. Then add the M6 bolts, slide your polycarbonate strip in the end, and tighten to clamp.
NB the fixture shown in the picture is version 1 which does not have access to the T-nut bolts through all 4 plates, version 2 is modified to include that to allow mounting & dismounting without having to completely disassemble the fixture.
Laser cut. The perimeter hex bolts (M6) will go through all the layers except the one with no center cutout, that is the bottom layer. Use an M6 hand tap to thread those holes. Use T-nuts and appropriate bolts through the end holes (not sure of the exact length, I used some shorter #10-32 ones I got with the mill) to fix this plate onto the mill bed. Stack two of the plates with center cutouts, then the spacers (long thin bits), then two more plates. Then add the M6 bolts, slide your polycarbonate strip in the end, and tighten to clamp.
NB the fixture shown in the picture is version 1 which does not have access to the T-nut bolts through all 4 plates, version 2 is modified to include that to allow mounting & dismounting without having to completely disassemble the fixture.
License
Laser-cut fixture for milling polycarbonate by MarkU is licensed under the Attribution - Creative Commons license.
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