I need to cut a Plexiglass backlighting panel for an address plaque I’m building as my first real project, and I’m looking for a good feed rate.
For starters, I programmed it at .020 deep per pass @ 20 IPM to cut out a 3/16" thick panel. Haven’t run it through a feed and speed calculator being this stuff is a little tricky to cut. Figured I’d start here and look for advice, and tweak my programming accordingly based on what y’all know to work.
I have 3 single flute carbide cutters, and was going to use the 1/4" cutter. I’ve also got 1/8 & 3/16 cutters I can use if they work better. I figured the larger flute of the 1/4 cutter would help evacuate material quicker to prevent melting.
I’ve cut Plex and Lexan manually on the Bridgeport, but I know that’s a different animal. We left the paper backing on to help keep the edges from chipping once the cutter breaks through, and cut it low and slow with lots of WD40 to lubricate. Trying not to use WD here though so I don’t screw up my MDF spoil board.
When I cutout acrylic (plastic) I use a 1/8" endmill (3.175mm) - 2 flute and run at 14000 rpm at 2000 mm/min. Pass depth of 1mm. I also leave the paper on.
I found that if I do not run fast enough the acrylic will melt to the endmill. Running faster gives me a clean cutout with no lubrication necessary. My experience tells me that 20 IPM (508mm/min) would cause melting issues. Your pass depth (0.5mm) could be higher but should work fine.
I use mostly cast acrylic. Standard plexiglass seems to melt easier than the cast acrylic.
I cut all my dust shoe from 1/2" and 1" acrylic. I left the protective sheet on while cutting. I used a 1/8" o-flute bit, set the Makita to between 2 and 3, and fed at 35 ipm. I had no melting and the finish was surprisingly good.
I’ve cut and routed Corian using the same parameters.
@DangerDog I am also looking to cut some acrylic soon for some projects, so perfect timing creating this topic! @gwilki what was the depth of cut you used? I have some 1/8" single flute bits (not sure if they are “O” flutes or if “O” flute just means single flute) that I was planning on using.
Since I already had it programmed for a 1/4 cutter, I just went for it since I didn’t feel like defining a new cutter. Ha!
Bumped the feed up to 80 IPM, left the DOC at .020, ran the router between 2 - 3, so prob around 15000 RPM, and the cut went smooth with no melting using a 1/4 carbide O flute. Pretty small chips, maybe a tad larger than a pepper flake, clean entry and exit edges cutting an outline through a piece of 3/16 plex.
Thinking I’m pretty conservative on my feed & DOC with the tiny chip size. Any pointers there? Cutter made a little noise in the direction of the sheet extrusion, but the cut came out clean.
Haven’t completely checked it dimensionally as I only have my little calipers here at the moment, but in the short direction the cut did come out .010 large on an intended dimension of 4.750. Is this a normal expectation?
@DangerDog The discrepancy in dimension is not unusual, I think. In my experience, it has been because the actual diameter of the bit is not as advertised. I have some single flute “1/8” bits that are actually .117" and others that are closer to .119".
I would imagine that the higher priced bits are better in this regard, but I stick to the lower priced ones and make test cuts to determine their actual size.
As an aside, I have two drill indexes of very good quality bits. I can drill a “1/4” hole with the 1/4" bits from each of them and they are definitely not the same size. I realize that wood moves as soon as it is drilled, but I would think that two holes side by side in the same piece of wood would move by the same amount.
Thanks Grant, that totally makes sense. I didn’t measure these O flute cutters, but got them in a 3 pack, branded as “Foos” off Amazon. I’ve noticed the same thing with cutters being undersized on some of the others I have that are private label type cutters not from known brands, so I’m sure that’s a big part of it.
Deflection wise though, and poor machining practices aside, I’d imagine we have to be prepared for a few thou variance, no?
@DangerDog I don’t believe that we need to live with a few thousandths variance, Danny. That said, much depends on what you are cutting, what you are cutting it with and how you are cutting it. I am playing with jigsaw puzzles,using a 1/16" bit. I was having a problem finding the correct offsets to get good tight joints. In the end, much of my problem getting consistent results was that I was pushing that small bit too hard. Depth of cut was OK, but speed was not. As soon as I slowed things down, my jobs improved.