From my limited experience, cutting acrylic successfully is quite difficult. What I’ve gleaned so far is that chip clearance is key to avoiding the melting problem. Using Fusion360, a 2D Contour cuts out the shape using the diameter of the bit but because the chips can’t escape the melting problem soon occurs as the depth increases. How can I tell F360 to make a wider contour cut? For example, if I’m using a 1/8" bit with a cutting depth of .01" I’d like to make two passes at each depth so that I cut a profile of 1/4" wide so leaving plenty of room for chip removal.
I’m using a 2 flute spiral upcut bit running at 12000rpm and feed rate of 25"/min and cutting depth of .01"
I don’t have a solution for the F360 question but, if you’re not already using it, cast acrylic is quite heat tolerant. I’ve carved it using Easel without melting issues.
I had an issue with both acrylic and HDPE melting somewhat until I changed to a single flute bit. It clears chips better and rubs the material half as much so creates less heat.
If you go faster, it’ll create less heat also.
To answer the question of making 2 passes, you could make an offset to the contour you are cutting far enough out to get the desired room and do a quasi contour cut with a pocket tool path. That way you would clear out the “pocket” area before the next depth. If you want to leave tabs just make 2 separate tool paths leaving the last depth for a single final path. best thing though is to do an offset contour path leaving only a little left for a final pass to true size at full depth. then any melting you get will be cut away on the final pass leaving a clean edge. the other suggestions above are good too.
I use light coats of WD-40 in the cuts just turns into plastic snow seems to work well for me.
+1 for single flute bit (ones specifically designed for acrylic are better) and fast as you can cut… 2Linc.com sells good acrylic bits.
Warren.
I have not cut Acrylic in a while, but I really found a 0 helix bit to work best with plastics that like to melt (ABS, HDPE, etc.). I got mine from ebay (drillman1) - limited diameter selection but good enough for what I’m after.
Also, as already noted, cut fast with a “medium”-ish spindle speed Iif you are using the stock “dremel”, 3-4-5 worked for me with an 1/8" 2 flute and my .0625 0 helix bit @ 22 ipm. I know I’ve done max speed with the 1/8" bit but the smaller bits really benefit from a much slow speed. I’ve done a speed setting of 2-3 with a 1/32" bit @ 22ipm without much problem with HDPE (0.015 depth per pass for such a small bit).
Hope this helps.
-Tom