Getting that perfect edge on acrylic

Hey all,

I was wondering if anyone had any tips for getting a good edge finish on cast acrylic. Specifically 1/4 inch thick cast acrylic. Our shop has purchased an edge finisher machine to clean up the edges on what we cut on our MultiCam 3000 CNC Router. This machine is painfully slow and is the bottleneck in our operation. We are trying to avoid a diamond polishing bit as those are very expensive and not much faster than our edge finisher machine.

I convinced my boss to purchase a bit from GUHDO that promises to deliver an amazing edge finish. It was features on their blog post a while back and I was wondering if anyone here has experience with it. It's a solid carbide upcut bit 8mm. Part number is 6201R080A20, but it's near impossible to find info on it.

If no one has any experience with this bit of tooling, could you recommend methods you may use to get a good surface finish on acrylic straight off the router?

Not sure if it will work on your material / setup, but we used to flame polish edges in the signage industry.

It takes a bit of practice and is a really easy way to wreck a part, but when done well it seems to be pretty fast and look good.

If you can use and edge finisher, why cut on the CNC at all?. All edge finishers i know of only do straight edges, though i suppose you could have shapes still best cut on CNC with only straight edges. Never tried the diamond bits, but i gather they aren't really as good as a flamed edge or an edge finisher .020" final past with good polished acrylic onsrud bit shoved up onto the spindle as much as possible would be my suggestion.

We use the CNC to cut the actual parts. We manufacture decorative plaques so everything is a rectangle with straight edges. I'm mostly wondering if anyone has experience with the bit I stated. I will attach the pdf for the bit if I'm allowed to with such a low number of posts.

If you already have on order, try it out....can't the mfg. tell you what's special about it? Onsrud makes a bit of a deal about polished bits, but I think the main step up is to diamond coating.....although that may be different from the diamond CNC polishing tools out there....those might have actually diamonds in them and not as a coating....again never looked into them as I don't think my machine is good enough to get the most out of them....3000 series might be a bit better, but I've always imagined they are best on a CR onsrud/thermwood/komo type machine. But again, finish pass is probably a sound approach, and even cutting with a solid carbide first and then the new tool for last 20 thou if you have an ATC might make the most of the tool life if it works in the first place.

However, I think you'll never get the same result from any CNC bit as the edge finisher / flame polishing/ or buffing. You might however get close enough to use a quick pass of a buffer....or do you need to leave glueable edges?

Quote:

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Originally Posted by gfacer

If you already have on order, try it out....can't the mfg. tell you what's special about it? Onsrud makes a bit of a deal about polished bits, but I think the main step up is to diamond coating.....although that may be different from the diamond CNC polishing tools out there....those might have actually diamonds in them and not as a coating....again never looked into them as I don't think my machine is good enough to get the most out of them....3000 series might be a bit better, but I've always imagined they are best on a CR onsrud/thermwood/komo type machine. But again, finish pass is probably a sound approach, and even cutting with a solid carbide first and then the new tool for last 20 thou if you have an ATC might make the most of the tool life if it works in the first place.

However, I think you'll never get the same result from any CNC bit as the edge finisher / flame polishing/ or buffing. You might however get close enough to use a quick pass of a buffer....or do you need to leave glueable edges?

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I do not need glueable edges. I do like the idea of using my normal carbide bit for a rough cut and then the new bit as a finish pass though. Good call on that. Either way the bit should be in on Monday so I'll try it out and let everyone know how it works. Is there a spot on this forum for tooling reviews?

A few little notes to some of the comments on this thread.
Cast acrylic cuts smother and doesn't melt as bad as extruded acrylic.

Extruded acrylic flame polishes very nicely. Cast not nearly as well and takes more edge prep usually sanding or scraping to achieve similar results.

Both can also be buffed to a polish but cast buffs nicer then extruded. Cast is also more optically clear then extruded.

Edge finishers have 1or2 actual diamonds embedded in the bit. They are expensive to replaced or have the diamonds repaired. Usually 1500 plus.

Edge finishers give the most attractive glue edges. Saw edges work well also with the right blade.

Never flame polish acrylic before gluing together. It will case the material around the area you glue to develop lots of unattractive little fractures or crazing. Gluing and then waiting over night before flame polishing the already assembled piece is the best and most attractive way to go.

Please let us know here how those tools work. I am interested in seeing how well they do. Post pics!

Thanks
Ben

You can also vapour polish acrylic.

bob

Add a couple things to keep in mind
Part rigidity is important . if material flexing in anyway will result in poor finish.
Machine rigidity is important also if there is any flex in the tools this will also cause problems with finish.
I use whiteside spiral up/down and compression cut solid carbide router bits as my end mills.
Speeds and feeds need to be tested and tuned for best results "this can take time" and change if you change brand or type of acrylic.

Attachment 288802

The picture above shows all parts made and assembled with no polishing or hand work of any type. even threads for fittings are thread milled.

Quote:

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Originally Posted by mountaindew

Add a couple things to keep in mind
Part rigidity is important . if material flexing in anyway will result in poor finish.
Machine rigidity is important also if there is any flex in the tools this will also cause problems with finish.
I use whiteside spiral up/down and compression cut solid carbide router bits as my end mills.
Speeds and feeds need to be tested and tuned for best results "this can take time" and change if you change brand or type of acrylic.

http://www.cnczone.com/forums/attach...d=288802&stc=1

The picture above shows all parts made and assembled with no polishing or hand work of any type. even threads for fittings are thread milled.

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That's some pretty nice acrylic you cut there. That slight bit of cloudiness would put my boss off though. He wants a perfectly smooth, shiny, see through edge. Even our 10k edge finisher can't provide that.

mountaindew: for your contours / cutouts, which tool are you using? Can you share feed / speed as starting point? I'm considering switching tools to improve my finish, your parts look great.