Milling acrylic

[galacticroot]

I'm going to try making keychains to sell. They will be made out of thick acrylic sheet, and engraved/cut with a CNC mill.

I've tried using some engraving bits, but they don't work. The acrylic melts and hardens in a ring around the bit, which builds up and melts more of the surrounding acrylic from friction.

I've tried many different speeds the mill can run at(1,000 to 10,000 RPM). It works better if I decrease the feed rate to 1 or 2, but I still have to run the program several times, and it can take hours to make a single keychain.

Since I'll be engraving text and graphics, the bit needs to be pretty small.

Does anyone here know what the best end mill for engraving acrylic would be?

 

[breezer]

this of any use ?
http://www.bayplastics.co.uk/product guide/Altuglas-guidenavbar/prod-altuglass-tech(turning).htm#en

it also says how to engrave it (sorry but you will have to cut / paste the url

[Edited by breezer on 06-01-2003 at 7:33 AM GMT]

 

[AndyB]

My father can machine engrave on his CNC, you have to keep the spindle speed as high as possible. Engravers use speeds of 10-20,000 rpm (electric motor) as the actual speed of the cutter is very low due to cutter size. The cutter makes a big difference too and you need a good sharp edge ground at the correct angle. Acrylic should engrave very easily as its so hard. We did consider fitting a Dremel type motor to the CNC to get the correct cutter speed but then he bought my engraving business so didnt have to bother!

 

[galacticroot]

I read that page before, but it didn't tell much about the correct bit to use. It says "plain cylindrical milling cutters with two or several cutting edges made of high-speed steel, HSS or carbide".

The best bit I've found so far is one which has many straight flutes, and is conical in shape. It's designed for manual use with a dremel though.

Maybe I could do a scratch test to determine the hardness of acrylic, and pick out a bit based on that. I don't want to get a bit set that won't work, since they are kind of expensive(a diamond bit is $60, a carbide one is about $35).

 

[AnonymousImport]

Industrial tooling distributors in your area will help. A 1/64 2 flute spiral cut ball nose endmill with Zirconium coating will work AOK. You will not find this cutter in your local Home Depot. Look in the book for your local tooling distributor. Don't be suprised if you pay $30 or more for a mill this size.

 

[mrbreckles]

I use an SMX 5000 CNC miller at work every day. Ive hardly had to do any engraving work but when i have ive always used a centre drill at the highest rpm i can get. Worked every time so far.

 

[foxhole]

I use an SMX 5000 CNC miller at work every day. Ive hardly had to do any engraving work but when i have ive always used a centre drill at the highest rpm i can get. Worked every time so far.

Only 8 years late

 

[mrbreckles]

I use an SMX 5000 CNC miller at work every day. Ive hardly had to do any engraving work but when i have ive always used a centre drill at the highest rpm i can get. Worked every time so far.

Only 8 years late

I immediately felt dumb after hitting reply; noticing the date.