Cutting 1" acrylic?

[wespor]

This is kicking my butt, my otherwise awesome settings for cutting 1/8" acrylic (for a near flame polish ready edge) are destroying my 1". I'm getting chatter and melting (air bubbles) on the edges.

Having trouble figuring out what direction is warm and cold to move in, right now I'm doing 4 passes 18k / 140 with ramps and a .3 offset and another, final single pass without offset. I broke it up to get some extra retraction, I am having pretty gnarly chip buildup though none of it seems solid.

For shits and giggles I threw on my micro drop mister and I'm not seeing much of an improvement.

This is the bit I'm using, new as of a few hours ago.

https://www.amanatool.com/51767-solid-carbide-cnc-spiral-double-o-flute-plastic-cutting-1-4-dia-x-1-1-4-x-1-4-shank-x-3-inch-long-up-cut-router-bit.html

Any pointers?

[robtown]

This is kicking my butt, my otherwise awesome settings for cutting 1/8" acrylic (for a near flame polish ready edge) are destroying my 1". I'm getting chatter and melting (air bubbles) on the edges.

Having trouble figuring out what direction is warm and cold to move in, right now I'm doing 4 passes 18k / 140 with ramps and a .3 offset and another, final single pass without offset. I broke it up to get some extra retraction, I am having pretty gnarly chip buildup though none of it seems solid.

For shits and giggles I threw on my micro drop mister and I'm not seeing much of an improvement.

This is the bit I'm using, new as of a few hours ago.

https://www.amanatool.com/51767-solid-carbide-cnc-spiral-double-o-flute-plastic-cutting-1-4-dia-x-1-1-4-x-1-4-shank-x-3-inch-long-up-cut-router-bit.html

Any pointers?
Are you using the same kind of acrylic?
Cast acrylic cuts nicer than extruded (if memory serves)...

[bleeth]

O-Flute will give you best results with cast acrylic.
Extruded acrylic cuts better with a straight bit.
I almost always used Onsrud's for Acrylic.
My favorite go to was a single flute upcutter. Always did a thin skin last pass to avoid part movement at the last second, particularly with smaller parts.
Try speeding up your movement bit by bit and observe the results.

[garyb]

18k at 140 is way outside the chipload range for a clean cut using a 2 flute
use the chipload formulas then fine tune, recommend a single O flute
gary

[wespor]

18k at 140 is way outside the chipload range for a clean cut using a 2 flute
use the chipload formulas then fine tune, recommend a single O flute
gary

Yeah, I'm noticing that the recommended speeds on their pdf's don't add up. I'm not sure where to start with the RPM through. When cutting thick acrylic is it just a "whatever, just adjust feed rate" kind of thing or does it cut cleaner at slower speeds? I've already broken one bit, I'm afraid to do too much blind experimentation.

New job, I've been cutting plywood and MDF for years but the new boss just keeps throwing thick ass plastic and aluminum at me. Now he's talking about brass. I'm going to throw myself under the bit.

EDIT: Here is an example of my problem, this is half inch acrylic with a rabbit on the edge, so ignore that center line but it's the little clear speckles that are killing me. It reminds me of bubbles rising the surface of a resin cast, they are deep and resist sanding and polishing. I seem to get them at any speed I try, not sure if it's me or a characteristic of these double o flutes I'm using. The surface quality on the pockets is nice but the edges are like this. Maybe I'm being picky but I have to sand and polish these myself and I need to minimize the labor it takes as much as I can to keep up.

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