I need to make a large hotwire bow like this one and I have a couple of questions. First, I’ve been using .2" diameter stainless steel wire. Should I consider going thicker for a 28" wide bow? Would you make any changes to the way the bow is constructed? I’ve used it and it works really well, but could it be imporved?
Here’s a great tip for new foamcutters, BUY A VARIAC! I’ve been struggling with my homemade power supply. After using Ken’s (Airframes) bow and cutter I realized how lacking my setup was. I bought this cheap variac on ebay for $55, and played around with it last night. My cuts never looked better.
I just made a larger hot wire bow that will cut up to 39 inches wide, and utilized the same construction as the smaller one in your photo. As for wire size, I use wire size between 22 and 24 AWG. I talked with the production guys at Insulfoam, because I was curious what they used, and they are doing pretty much the same as we are. Also, I found the varaic you posted from a place in Mesa AZ, and I think they were about $44.00. I ordered two of them, and they threw in a nice digital multi meter for free! I paid about $8 for shipping, but no tax. Seemed like a pretty reasonable deal.
Make sure you add the spring tension to the wire, as the wire expands as it gets hot, and the spring will compensate for the expansion. Another suggestion would be to make sure you have a good size fan running while doing your cut, to help keep the ends of the wire, where it attached to your harp, cool. If the wire gets too hot, It may break. The harp you showed is the first one I made, and have cut about 50 blanks so far, and am on the original wire.
I think you are correct. Same place. You can use your piano wire, although I havn’t tried that, or Nichrome hard drawn wire or Inconel spring tempered wire. The wire is available through Wire Tronic Inc, in Pine Grove, CA. www.wiretron.com I’m sure there are lots of places to get the wire, this is just the place I happened to use.
