Need Help!- Acrylic routing problem

[marc.brunet.gag]

Hello,

I'm working in a signs manufacture company and we are machining acrylic. Now the process is that we cut the acrylic with a CNC router, but the finish is not good so we need to sand it, after and we burn the edge to give a perfect transparent finish.

My objectif is to eliminate the sanding process because it is very long.

I tried several bits on the router to give a perfect finish, 1 flute, 2 flute, 3 flutes, spiral, straight, ... my main problem is that I don't know what RPM and feed to use to have a perfect finish and with with bit.

I want to make it in one pass.

Can you help me?

Thank you

Marc

[LeeWay]

I route a lot of polycarbonate as opposed to acrylic, but some things are similar I would think.
Acrylic does melt easier than poly.

The finish on my stuff is not crucial. I don't flame polish the edges, but have played with it.

I think one way to get a better finish is to actually use a finish pass. Just set that up on the Cam side. A very light high speed pass should yield pretty good results and reduce sanding at least.
Any slop at all in the machine or spindle will show in a single plunge pass, but if you do a finish pass, it's a high speed light cut and should easily produce a smoother edge.

[beone]

try painting dish washing soap on the plastic before cutting. improves the finish greatly

[elogicca]

I use onsrud 2 flute downcut, great bits give a great finish 18,000rpm 160ipm 0.165doc.

But i do get some chatter on the edges, if an optical finish is needed you have to sand.

I imagine a 100% rigid machine would not leave tool marks on the work piece.

[elogicca]

Originally Posted by beone try painting dish washing soap on the plastic before cutting. improves the finish greatly

Imo I would not put any detergent near acrylic, if he was to put detergent then cut then flame he would get crazing.

[SCRAPWOTSCRAP]

What thickness acrylic??? Elogica is correct about the detergent....you don't need crazing at the flame polish stage. 14,000 rpm/180 in min creates less melt in the acrylic.......thus less sanding. A .020 finish pass at very high feedrate will reduce sanding dramatically.

[Geof]

Originally Posted by elogicca Imo I would not put any detergent near acrylic, if he was to put detergent then cut then flame he would get crazing.

Not necessarily, use a very mild detergent. I have machined a lot of acrylic using a water-detergent mix without any problems.

Don't use the uber powerful degreasing detergents, they may cause problems.

[elogicca]

You'd be surprised what will react though when you get to flame polishing, even acrylic polishes respond bad to it.

[rhundl]

Why dont you try a buffer like you would use on a car... You still may need to sand it though... if you use a heavy enough polish it may yield the results you are looking for

[cutsall]

spray mister with minimal pure water has been most effective for me. air clears chips and water cools and eliminates weld back or frosty look to cut edge. have been able to get nice traslucent edge but for transparent still requiers polishing.

[automizer]

i ran the router table for a sign shop for 3 years and i ran onsrud O flute cutters with a vegetable based oil mist and after some play you can get the speeds down to almost not need the flame