I am trying to route a logo into .220 Clear Acrylic.  I am using an .125" End Mill bit and i'm only plunging .09375" into the material. Can anyone give me advice on what my feed rate, spindle speed, etc..etc.. should be in order for me to get a smooth cut? Ive been toying with it but it seems everything i try still comes out poor. The acrylic is basically melting and re hardening where i'm cutting. The edges are coming out not as smooth as I'd like. Acrylic isn't cheap- so I'd like to stop this shoddy work! Please help acrylic masters!

Thanks- Brian

I have done acrylic quite a few times and its always come out well but it was on the Bridgeport with flood coolant. If you dont have coolant maybe spraying some WD40 would help.
Hood

I'm running a spindle without coolant- so spindle speed and feed rate don't matter much?

With flood coolant it wouldnt really matter too much as long as you were not going too slow for the feed. Sorry I cant be much more help as I have never tried without the flood.
Hood

I am trying to route a logo into .220 Clear Acrylic.  I am using an .125" End Mill bit and i'm only plunging .09375" into the material. Can anyone give me advice on what my feed rate, spindle speed, etc..etc.. should be in order for me to get a smooth cut? Ive been toying with it but it seems everything i try still comes out poor. The acrylic is basically melting and re hardening where i'm cutting. The edges are coming out not as smooth as I'd like. Acrylic isn't cheap- so I'd like to stop this shoddy work! Please help acrylic masters!

Thanks- Brian

If it's melting, then you need to reduce RPM, and/or increase feed.  But, to get the best finish, you want higher RPM and lower feed, so best results do really require coolant.  Just air might suffice.  It might also help to use a very high helix cutter.  You should be able to find tooling made for plastics.

If you're looking for a really smooth finish, do the best you can with the router, the flame polish to remove the machining marks, which will leave the cut surfaces clear and glossy, just like the unmachined surfaces.  You can do this with a cheap propane torch set on a pretty high flame.  Hit it *just* long enough for the surface to gloss over, then move on, before it catches fire.  Takes a little practice, but leaves a really ncie finish when done right.

Regards,
Ray L.

Hi, From your description"I am trying to rout" i assume you are using a router which is probably 10k rpm or more.
I cut acrylic on my router using an onsrud or micro 100 1 flute (The Onsrud is super- o flute) I have cut through 1/4" in one pass. at 30"/min 10K rpm. The Edge or bottom finish, if not a through cut are great.

What I would suggest is, increase the feedrate A LOT, use compressed air to blow the chips out. the problem with an endmill on acrylic is the chips don't come out fast enough and stick to the cutter or the work piece.
You need the chips to come off and carry the heat with them, not the chips to heat the cutter.

Hood's solution of flood cooling works if you have that option too, But my MDF table is not conducive to Flood!

hope that helps,
Cutmore

I am operating with a 6hp spindle. If that makes a difference.

It also makes a big difference what type of acrylic you are using. Cast acrylic is best for machining, extruded has a much lower melting point. There is also tooling specifically designed for routing/milling plastics as well.

Just general stuff:

Definately test any coolants on the acrylic before use. Some oils can cause permanent discoloration, clouding or even micro stress cracking in certain plastics . . . including arcylic.

Constant stream of high velocity compressed air, single flute cutter (two flute at most)

Consider using polycarbonate instead of acrylic.

What is the best router bit for this application? I've been told single and or double flute - O Flute? Any suggestions?