Why use a foam cutter? Well let's look at this picture below. The piece on the left was broken naturally while the piece on the right uses the cutter. Now do you want your sword to look all bumpy? That's going to slice up a body really cleanly.
But playing with foam is stil great for cosplay so over the past 4 years I have purchased two foam cutters (between $10 - $25).
So you can start off with a foam cutting knife and slice through your foam with a cutting drawn on. But many time after i do it, and i flip the piece to the other side, I realized that I had not been holding the knife exactly straight. So all my sizes on the drawn side is pretty, but but all the work on the backside is all misproportioned. Looks quite bad.
hard to tell in the photo, but in real life the two sides aren't even . . . .
I used a foam cutting table (like a band saw table but with a hot wire) back in high school. It was pretty fun to play with, but why would you pay that much for something that would just take up space and you would rarely use? So let's make our own
I used a small bed side dresser to tape the foam cutter and let it stick up straight past the end of this computer desk.
Be careful you dont hit the knife on the table. I accidently melted a line on the table molding (my boyfriend wasn't very happy to see that damage on his desk).
So just like using a bandsaw, you start sliding your piece against the knife and push it naturally to let it cut.
It's also awesome on holes because you slide the piece onto the knife.
Here's my cut piece. Lines are smooth as much as my hand can glide (if you are more picky you can you a straight edge to act as a guide if that's what your piece calls for).