Cutting expanded PVC sheets

How To
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Hello,

I have a few questions regarding expanded PVC.

I have a bunch of 1/2" black expanded PVC material and a few months ago I tried cutting it, with pretty poor results. It seemed to melt on the edges and the final cut resulted in a bunch of hard rough edges.

I can’t figure out if it was the bit or the profile I chose to cut it. I’ve heard too fast melts, but I also hear the opposite, that you need to go fast for that kind of material.

Are there any suggestions for the best bit and profile to cut expanded PVC sheets for lettering?

Thanks!

2

And what bit were you using? The consensus here is that if the edges are melting, you either have to slow down the rpms of the spindle, or increase your feed rate, assuming your cutting tool is in good shape.

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I had tried with the Amana 46202-k which is 1/4” down cut bit. I’m a little hesitant to use manual settings with the material, as it’s expensive.

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I can almost guarantee that you aren’t going fast enough. What are your speeds and feeds?

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I wouldn’t use a downcut in plastic — it will lead to recutting of chips and buildup of heat.

I use the Carbide Create soft plastic settings and they’ve worked well.

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Might be worth noting the difference between cutter fast and machine fast as that may be some of the apparent difference in recommendation.

When the cutter is spinning fast (router RPM fast) and moving slowly through the workpiece (machine feed rate slow) then it hangs around stirring the plastic and melting it, it’s like dragging a hot iron through the plastic.

You can either reduce the RPM on the router or increase the speed the machine is moving the cutter through the plastic.

If you feed too fast without enough router RPM you’ll get chipping, tearing or fracturing in the plastic. What you’re currently seeing is too little feed rate for the router RPM.

If you’re nervous about just running the machine movement faster, you can reduce the depth of each cutting pass and take smaller bites out of the material in each pass.

Dust extraction is pretty important too if you want to get good clean finishes on plastics, as Will said if the chips hang around they get melted into the cut.

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Thank you everyone! This is all helpful information and thank you @LiamN for explaining it to me in simple terms. I get it now!

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