Foam Help


New Member
Hi RPF folks! I've recently been trying to make various foam items such as magnetos new costume and some iron man parts and I've faced a few problems that I need help with. The foam, whenever I cut it, has fringes and I can never seem to cut a straight piece of foam. This has been very annoying and hard to look at too. Also thing such as magnetos horn part are small and feature slants and I was wondering if any of you guys knew how to make such slants with foam. Thanks for you time!



Merely a general remark; Is it possible to add a Tutorial option to the menu line? With sub-sections for materials and category? It might cause fewer new threads on the same topics.
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Active Member
What are you using to cut it with? The important thing with cutting foam is to make sure you use a sharp blade. I cut 10mm Eva foam with a scalpel and that gets blunt after about 2m of cuts.

Try and cut with the blade at an angle, you don't want it to be 90 degrees to the surface. You want to drag the blade behind, not try and push through.

I usually cut with the cutting edge as close to the surface as possible. The cutting action is almost effortless as the blade will glide through the foam


Sr Member
Blade sharpness is key. Get yourself an x-acto knife. A fresh blade will make a sharp, smooth cut at any angle. It also makes the cuts much easier, like a knife through butter.

I bought a box of 100 replacement blades for like $11 on amazon. This is especially helpful if you have big pepakura plans and will be making lots of cuts.

Replace the blade often while you work. If one of your cuts starts to get ragged, stop and put a fresh blade in.


Sr Member
It COULD be the foam, but i would try a new blade and see if that makes it better. It really is a world of difference. You say 'box cutter' and I pictured the dirty old one we've all have in our toolbox for 5 years.

Also, you'll never get your glue seams to be clean and smooth with that ragged edge, the gluing surfaces need to be really smooth so the joint is very tight.


Active Member
I've never had great luck with exacto knives and that thicker floor mat foam. Even with a fresh blade I find it just tends to tear that foam (similar to your results) versus slicing it cleanly. I had fairly decent luck with a hot knife but lately I've just been using good KitchenAid scissors. My lines are cleaner and straighter than I've gotten with the exacto blades. I still use the exacto for tighter spots I can't maneuver the scissors into.


Active Member
I was having the same problem while trying to cut with an xacto knife. I ended up buying a hot knife for about $10-15 and it cuts much more smoothly.


Master Member
I agree with IronManiac, you always want a sharp blade, and change anytime you start tearing the foam instead of cutting it. Also do not buy crap brands; When I'm using my X-acto cutters, I use actual x-acto blades. I'm not saying that other brands don't work, but I've also got off-brand blade sets (the cheap ones) from Menards that look identical, but will not cut for anything. A fresh blade should be able to cut a 45 degree angle through 6mm foam with no problem.

As for using a box cutter....
The following is just my preference, but I actually cut 95% of my foam with a box cutter identical to this:

....loaded with these:

I go through around 20-25 blades for a full suit.


New Member
I've not seen this posted anywhere but I discovered that an electric knife - yes like the one you carve a turkey with - is an excellent tool for cutting all kinds of foam from eva to acoustic foam. Leaves very smooth edges.


Active Member
I've had a similar problem when I was testing out different versions of foam and I always had those problems when I was using foam that was pretty soft. I'm now using pretty rigid foam. Not that easy to bend but pretty good to cut :)