Foam cutters and LR?

Hey guys, Just wondering if anyone has experience cutting foam with their LR?
I am a big Airsoft fan and would like to cut to spec the foam for a gun case and have everything fit perfectly.

Has anyone used any form of foam cutter in the past?

@dkj4linux is the man to talk to…

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+1 for @dkj4linux if you’re looking at hot-wire foam cutting.
Several people have reported success milling EPA foam (e.g. Harbor Freight floor mats) with standard milling tools. Tool Shadowbox and Tool Box drawer liners


Oh, forgot about those! :man_facepalming:

Gee, I was trying to hide from this but you guys

I’ve used 2 methods for cutting foam… needle-cutting and hot-wire. Needle cutting is good for cutting the dollar-store foamboard (DTFB) popular with the RC folks… and is limited to 1/4" or slightly more by the stroke length of the reciprocating needle. Thicker foams are easily cut using a hot-wire… but this has the disadvantage of not being able to reach inner shapes without having to cut through an area you’d rather not cut through.

Here’s a hot-wire machine cutting a “donut/tire” from 2" thick construction foam from HD… the undesired cut is middle-left, between the circles and the one above is a score-cut in the foam as it comes from the factory

What kind of foam are you wanting to cut… and how thick?

I suppose it possible to mount a soldering-iron/hot-probe that could be lifted from the material when moving from shape to shape… but I’ve never tried it. It suspect with a large Z-movement the probe might leave a “dwell and melt” artifact there as well.

– David

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This is awesome, with a hot needle do you have to cut on the Z axis or can you cut straight down on the X?

I’m not real sure what you are asking here…

Assuming you are talking of the hot-wire video, the large flat surface of the foam is in the XY plane… X is horizontal and Y is vertical. The hot-wire is parallel to the Z axis… however there is no movement in Z. This is really just a 2-axis XY machine… with the towers, front and back, electrically slaved to one another. Simple straight-through cuts only… i.e. no tapers.

I guess what I’m asking is would I be able to put the cutter on my low rider and place the foam on the spoil board and cut it from the top down.

Not with a hot-wire. You need two moving ends to use a hotwire system. You could use a needle cutter, but as mentioned, that really works best for foamboard. What you may want to look at is using a bit with the EPA foam. Short of building a purpose-built machine for hot-wire cutting, that’s likely your best bet. Either that, or just build a hot-wire table (look at bandsaws and jigsaws for reference), and make the cuts by hand. If you’re just doing it for yourself, it should be no problem. If you’re doing it for a business, then you’ll probably want to look into foam-cutting bits (Google Datron)…


As @kvcummins said about the two moving ends with the hot-wire stretched between… note the tower and carriage behind the foam moves in sync with the tower and carriage in front

A ~4" section of 30 AWG nichrome wire is heated between connections by passing 1.5 - 2.0 amps through it… giving 800F - 1200F. Here, the power supply, operating in constant current mode, has adjusted to 6.33 volts to provide the 2 amps through the wire.

And the wire is just faintly glowing red at 2 amps… and way more than required to cut foam.

I started at 1.5 amps for the 2" styrofoam Tux above… but found that the construction foam (Foamular from HD) is more dense and upping the current to 2 amps allowed me to power through its 2" thickness at 800 - 1000 mm/min feedrate.

Hope than helps. – David