Foam Cutting with Stencils

The Helmet

I cut a piece of foam with a stencil, and it turned out terrible! So I tried again, and it turned out better…

A member of Milwaukee Makerspace loaned me his Proxxon Hotwire Cutter Thermocut to cut some foam. If you remember one of my previous foam cutting experiences using a drill press, that worked ok, but I wanted to try another method, the hot wire foam cutter actually designed to cut foam.


I started with not one, but two stencils, with the idea being I’d put them on the top and bottom of the piece, lined up with each other.


Why two stencils? when I tried to just use a top stencil with the wire cutter, the wire flexed a bit and I got not-straight lines.

Taping to foam

I attached the top of the “stencil placement guide” to the top of the foam with tape…

Taping to foam

…and then attached the bottom to the bottom, lining them up with the corner so they’d be in alignment with each other.

Spray glue

I then spray glued the actual pieces I wanted to stick to the foam with spray glue (using our spray booth!) Note that one piece is flipped upside down and one isn’t, so they match each holder.

Put it on the foam

Here’s the top piece glued into place…

Put it on the foam

…and the bottom piece glued into place.

Stencil on foam

Once glued in place I remove the top stencil holder…

Stencil on foam

…and the bottom stencil holder. Now we can cut. Hot wire goes through foam so fast I didn’t even get a photo!

Stencil on foam

Here’s the helmet cut out of foam. Top view…

Stencil on foam

…and bottom view. Yes, there are some rough spots, but the wire stayed pretty well aligned thanks to the top and bottom stencils. You just need to glide the wire along the paper’s edge. Much easier than trying to freehand a line drawn on the foam, and better results too!

You may have noticed a hole show up in the helmet. The reason for that was to feed the wire through to cut out the middle, but I forgot the wire was on a spool, so… bigger hole!


I cut a hole just large enough to fit the spool through…


…and once it was through, reattached it to the cutter so I could cut out the middle piece.


The middle piece came out pretty good… Now that’s a helmet!


A few of the cuts are a bit rough, but some sandpaper makes light work of them.


Ahh, now here you can see the terrible results of only using a top stencil from my previous attempt. The wire tended to cut deeper into the bottom of the foam where there was no stencil to guide it.


Our new improved helmet cut with top and bottom guides is much better. And hey, now it’s ready to be cast in aluminum!


While the Proxxon is nice, there are a lot of DIY foam cutters that can be built with scrap materials. Ultimately though, I think a CNC cutter would be cool. Just add an XY table and away you go!