Troubleshooting Chipping when Cutting Acrylic on the CNC

Bit issues and speed settings can create chipping problems when machining acrylic. June 17, 2009

We have a Weeke BHP200 and we are trying to cut 3/8" plex. We are using a 1/4" single flute cutter, 25,000 spindle speed, feed rate 275" min. The problem Iím having is "chipping" from the cutter. Any advice would help.

Forum Responses
(CNC Forum)
From contributor G:
You should be using a larger cutter diameter - at least 3/8". Also if your cutter has cut wood, it needs to be changed. Cutters that are used to cut acrylic should never touch wood. A new solid carbide or carbide tipped 1/2" - 3/8" cutter along with the parameters youíre trying should work.

From contributor R:
I too suspect your cutter. For acrylics, you should be looking at an "O" flute bit. The geometry tends to sweep the waste away more than chiseling it. Onsrud and Courmatt both make bits specifically for cutting plastics.

From contributor B:
I use an Onsrud "O" to cut 1/4" Plexi and the tool is 1/4 in diameter. If I had to go with thicker material I would just go to a 3/8 bit with the same configuration. Ramp or sweep in your starting cut and the same on exit. 25,000 rpm sounds kind of high to me for your feed rate. I would think the plexi would melt from the heat. I run my 1/4 in. at18,000 and 260 IPM and never get chipping.