Polycarbonate (Lexan) Advice

I’m preparing to cut out 4 24"x24" sheets of 3/8" polycarbonate (lexan) to make ~180 coat hooks for our youth organization. If it were acrylic, I’d do this on our 100w laser, but the lexan is a big no-no there as it likes to melt (then catch fire) instead of sublimate.

Anyone have advice on setting up this project as I’d rather not screw-up stock if I can avoid it.

A layout is below - there is .34" between pieces (each piece is 1.5"x7"). I’m debating 1/4" vs 1/8" single flute endmill for the cutouts (1/8 is needed for the screw holes).

Probably will go full tape & glue for workholding all these these small parts. I also thought about cutting all the holes first and screwing them all down, but 90 screws would be a pain. If I use an 1/8", I’m not sure that tabs would be helpful as so little stock would be remaining, but am interested in any advice.

Coat Hook

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DISCLAIMER I have never actually attempted this on a CNC*

Personally, I would cut out the bottom half the piece for each row then securing it with a board across the entire row. I would face the board with a piece of non-slip rubber mat. This would prevent slippage and protect the surface from scratch resistance, as that is PCs weakness.

Concerns with this plan:
Board must be narrow enough to not interfere with the path of the cut below or above it.
Board must be sturdy enough to apply sufficient down force to the center. If board has any discernible bow, be sure to place that side down.
Ensure that your retract height is sufficient to clear hold down configuration.

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High feed, low DOC. Fast and shallow. Single flute.
Glue and tape will work well, just make sure you have good coverage for all the small parts.

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Not an expert…but thinking about it. I’d use the 1/8" bit…the more surface left behind, the better your tape will hold. Plus, there’s really no difference for cut outs and you have to chuck the 1/8" bit anyway.

If you use the 1/8" bit, make sure your screw holes are larger than 1/8". I’ve heard 10% larger, but I have standardized on a 9/64" hole for my 1/8" designs.

Tape and glue will work for workholding, but make sure you get two stripes under each row of parts.

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@Biologyben Are you going to heat bend all of them? I’m curious how you’re going to do that with so many?
I’ve got some scrap 1/4" PC that I might be able to try later on.

No bending - These are placed flat, parallel to the wall, mounted onto a poplar 3.5" x 1.5" board every 6-ish inches using washer-head screws. The tall hook is nice to ensure each kid can hook a lunch box, backpack & jacket all on 1 hook.

This vertical arrangement ensures that kids don’t get caught or poked by them when near the wall or reaching up to get their stuff (as every kid seems to love placing their stuff as high as they can possibly reach.) We’re mounting three 6’ boards on each wall (@ 30", 54", 78") and we’ll have 4 walls of hooks for a total of 150-ish hooks on 72 linear ft of hanging area in our entrance area. The rest will be mounted in another room (if I don’t screw them all up!)

In normal years, we’ll serve 200-250 kids a day, so this is just a start!

Will look something like this…

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I see. Much simpler than I was envisioning. Like I said, I’ll give it a shot on a scrap and let you know.
Were you going to countersink or bore the holes?

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I was just boring holes to slightly larger than the screw thread diameter. I intend to use a 1 3/4 Kreg pocket hole screw as an easy to source washerhead screw to spread the load

Bore holes first, then oval outline, and all that other work holding advice.

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I cut polycarbonate all the time. I use this bit:

https://www.toolstoday.com/v-13807-hss1621.html

It’s 3/16" diameter. They make it in 1/8" and 1/4" too. I feel like 1/8" might be too small a diameter for chips to clear out of the slot, but I could be wrong.

I’d cut 3/8" in (3) 1/8" passes. I leave tabs on the parts, then use flush cut nippers to (easily) cut the parts out of the sheet, then flush cut the tabs off.

I’d hold the material with double sided tape - horizontally at top & bottom & maybe between rows, but your layout might be a little tight for that. If you shortened your part a little bit below the bottom hole, you could maybe make room for that?

And I wouldn’t cut ALL of the holes, then ALL of the profiles. The most I would do is a row at a time… row of holes, then row of parts. Then if something goes wrong you have untouched material left to work with.

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@Biologyben
Fast and shallow with a cheap 1/8" single flute.


2500mm/min
1.5mm DOC
Fusion Bore & 2D contour

Had a communication buffer issue in the top curve…think I tracked it to a chord tolerance setting that somehow got changed to .001mm . Otherwise, smooth and easy.

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