Cutting Plastic, Feeds and Speeds

[ryan_slaback]

I am trying to make some interior signage. I have the file set to engrave .018 inches deep and am using a single flute 1/16" end mill to do so. I am having problems with the plastic getting on the cutter and then balling up and melting the plastic around it. Has anyone successfully routed plastic that can give me some pointers? It will work great when it cuts a straight line (I have a .5 inch by 4-5" long box it cuts out) but when it has to slow down a bit to cut the curves of the letters is when it tends to cause issues. I appreciate any help. The way it works right now I have to watch the machine closely and manually remove the melted clumps on the cutter and that is a PITA.
Cutter is moving at .5 in per sec (optimal speed) and is set at a 40% stepover.

[knight_toolworks]

have you slowed down the rpms? if you can't increase the cutting speed thats about all thats left. plus some plastic is worse then others. always try to get non extruded plastic.

[richards]

If you can't slow down the RPMs, try blowing some compressed air on the tip of the cutter. The 'chiller' ventri device is said to cool the cutter 100-degrees, but even using just plain old compressed air seems to help. Ten-dollars worth of fittings from your local pneumatics dealer, or even Home Depot, should buy you all that you'll need.

[ryan_slaback]

Mike, I have an air needle similar to Brady's design that I put on it for this purpose, but I need to rig up something different as this is hard to control the motion laterally to align the air hose and it blows either right or left of the bit.
If anybody who has an air line run to theirs could show a closeup of the aiming system I would appreciate it.

[Brady Watson]

Just use 2 90° fittings and close nipples. Hand-tighten (no teflon needed) and direct the nozzle wherever you need it.

-B