I'm not going to go into too much detail on building a hot wire foam cutter here. There are tons of great instructables and videos already. I am going to show you how my laziness and impatience in building one paid off with a new material to use that will allow you to bend the wire into shapes to cut with.
If you like this, check out my other instructables here.
I also made a video podcast of this below.
Step 1: The Wire
So when I was building my foam cutter, I did not want to wait for a roll of nichrome wire to arrive in the mail. I started looking around my house for something else I could try out. I know that stainless steel conducts electricity but not very well and I happened to have some 1/16th tig wire in my shop. This stuff is so handy to have around and I have used it for many projects in the past, most notably my make your own springs in seconds instructable. I decided to try it out and it works. You sometimes have to adjust the resistance by extending the wire longer because this is pretty hard on the power supply. I can tell if the resistance is too low because the power supply sounds like a weightlifter going for the world record. The wire does not get red hot but will cut foam easily enough. The best part about this is because it doesn't get red hot it can easily hold any shape you bend it into.
Step 2: Basic- Cutting Profiles
if you want to cut a specific shape, you can draw or print it on a piece of paper, then use that as a template to bend your wire. For straight cuts, clamp anything straight to the table to act as a race or guide.
Step 3: Intermediate- Round Profiles
By drilling a 1/16th" hole in my cutter table, I can poke a scrap piece of wire up and into a block of foam. This acts as an axis for the block to rotate around. You have to break the surrounding material away to get at your piece. It is really fun to break foam and have a cool part fall out in a christmas morning kind of way. The only thing to remember is that you have to cut into the foam block first, then push up the axis, then rotate, pull the axis and draw the block back away from the wire. If you try it it will be pretty obvious i think.
Step 4: Advanced Part1- Multiple Curved Cuts to Make a 3d Mold
I wanted to see if I could build a fiberglass skateboard so I needed a mold. I modeled the deck up in solidworks (but google sketchup would work and is thousands of dollars cheaper [its free]) From the 3d virtual model I created a side profile and a top profile. I made 2 cardboard templates from the side profile and stuck them to the sides of a large block of styrofoam. Cardboard will not burn or melt with the stainless wire so it makes a great guide. I printed out the front profile or dish shape I wanted the board to have and carefully bent the wire to match it. This I attached to a handle cutter and dragged it along the templates.
Step 5: Advanced Part 2- Finishing the Board Mold
I pinned the two halves of the cut foam back together with scraps of tig wire. (I told you this stuff was handy) I traced the top template out and used the table mounted cutter with a straight wire to cut along the line. This gave me 4 pieces of foam. If you pull the middle sections out of the top and bottom slabs and then pin them back in place but keep them offset a 1/4" each, you will create a 1/2" cavity the exact shape of your virtual skateboard. From there you bondo it into a usable fiberglass mold. But I won't get into that, one because its an instructable on its own and two because I haven't finished it yet. I just wanted to show you what the bent wire cutter can accomplish.
Step 6: Finding the Wire
If you go to a welding supply store, they will want you to buy a minimum of about $100 of the tig wire. If you go to a welding shop, they will probably give you a bunch for a couple bucks or a trade (beer and or pizza go further than their monetary value).
Thanks for making it this far! Ill embed the video podcast one more time