Machine cutting of plastic is not much different than cutting metals. The
cutting tool applies pressure which increases the temperature of the
material just ahead of the cutter. The sharp edge then peels away the heated
region. Since acrylic materials don't conduct heat well, the region just in
front of the cutter will heat very quickly, and will stay hot longer than
say, aluminum or steel. The two things to master in cutting plastics is to
make sure the cutter doesn't stay in one place too long - meaning that the
feed rate has to be pretty high, or else it will make an ever-increasing
pool of molten plastic from which chips can't escape; and that the feed
isn't too fast, or a tooth will try to peel off material that is still too
cold and hence hard, causing a fracture. The same is true with rotating
cutters and reciprocating or band saws.

I second the comments about work holding. Good clamping will prevent
fractures from the occasional blade hang-ups that can occur. I routinely cut
acrylic sheet with end mills, band saw & saber or jig saw, depending upon
the thickness and complexity of the cut. I have developed my own speed &
feed technique with two-flute end mills or blade tooth pitch similar to what
I would use for aluminum, and my feed rate is between two to three times
that which would be used for cutting aluminum. Once you start a cut, you
have to just keep going without hesitating once you have found a comfortable
feed rate.

A router or rotating Dremel tool should work, but the super-high RPM's would
make the needed feed rate higher than I would want to try by hand. I would
think that with a good speed controller one could get good results.

If you want to calculate where to start, figure somewhere between 1 & 2,000
surface ft per minute cutter speed, and no more than .010 in. of feed per
tooth. For example, if a round cutter is used, try: rpm = 4 x sfpm/dia.
This should give you an idea of how fast to feed thru the plastic at various
RPM's. You can approximate the surface feet for saws and it should work just
as well.

Chris

> -----Original Message-----
> From: pic microcontroller discussion list
> [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Pic Dude
> Sent: Tuesday, May 14, 2002 6:41 PM
> To: PICLIST@MITVMA.MIT.EDU
> Subject: [OT]: Cutting acrylic/lexan/plexiglass
>
>
> Looking for suggestions on making smoother curved cuts in 1/8" and
> 1/4" acrylic. urrently I use a Dremel rotary tool with a Roto-zip type
> cutting bit (rotary/spiral saw bit) but get very jagged edges.
>
> Anyone know if there a better bit I could use for this?  Perhaps a
> Dremel 194 high-speed cutting bit would work better?
>
> Or is there another process I could use for this?  Scoring/snapping
> and circular saw with carbide-tipped bit are the only other processes
> I know for this, but they are just for straight cuts.
>
> Cheers,
> -Neil.
>
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>

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