Build up of material on bits?

[nodnerb]

Is there any type of bit or technique that prevents material from building up on a mill bit? I am basically drilling hundreds of 0.13" holes into HDPE and every 10-20 holes there is so much plastic built up on the mill bit(1/8" upcut) that it starts melting the plastic and I have to stop it to clean. By then the holes are all becoming cruddy from rewelding anyway. Then I restart and sometimes the holes are off. And either way, the surface is a mess.
I realize that slowing down the spindle will help *some* with the melting but it won't prevent the build up of plastic and eventual heat build up.

Any help please on techniques or special bits?

[harold_weber]

Try using the drill geometry recommended here:
http://www.plasticsmachining.com/magazine/2001-09/PP-HDPE.html

Also, try peck drilling (frequently back out the bit till it clears the surface).

[knight_toolworks]

I was told doing peck drilling would help. so you don't drill the whole depth in one pass. but I had 20,000 holes to drill so it was not practical. I sprayed the surface with wd 40 as it was all I had and it took care of it.

[sailfl]

If you are getting a build up of material, you might want to look at the bit you are using - is it right for the material or the speed of the router / spindle - is it the right speed for the bit and material.

[navigator7]

[QUOTE=nodnerb;98209]Is there any type of bit or technique that prevents material from building up on a mill bit? [QUOTE]

Have you tried air? Or an air/water mister?
Another possibility is The Cold Air Gun or Ranque-Hilsch vortex tube:
http://www.newmantools.com/vortex.htm
http://www.newmantools.com/vor610.jpg

Runs off shop air but watch out for the hot end! Yoooowsers!

[garyb]

Sounds like you have the wrong tooling
Try a Ons 70-500 series they are a HSS Plastic Drill designed for drilling in hard and soft plastics

gary

[nodnerb]

Awesome! Thanks for all the replies everyone. Unfortunately the onsrud drills would not work in this case as it was a special size and I needed to 2d toolpath it. It always seems to be a special size. lol