Topic Author's Original Post - Jun 6, 2014 - 02:52pm PT
This question is for a good friend...
He needs a hot knife. He's not sure on hand held vs fixed, or brands/temperatures. Any recs or advice from the soft goods makers out there?
Here's his question/info:
"For me it's about speed. Right now I'm cutting with scissors, then sealing with a lighter. I'd like it to be as fast as that, and a cleaner edge.
If something cuts slow, but clean, that'll be frustrating, and I'm hoping to have something that can do a high volume of cuts without having to do a major pause to clean it every 5 minutes in a 2 hour cutting session.
The material is cotton with acrylic core. 2.5mm thick and 1.5" and 1.25" wide."
We don't hot knife in the volume it appears your friend does but with sailing and climbing we do a lot of hot knifing.
We use Weller products...both the plug in type and the butane powered hot knife/soldering for jobs when we don't have access to power.
Weller makes a variety of hot knife products.
Your friend might want to experiment with soldering iron on such to see if his material actually cuts with heat. Cotton won't melt, but might burn through with high enough temp.
You can make a hot cutter with a car battery and steel wire strung between bolts or nails in wood. You experiment with the length of wire to get the right temp, so it melts the webbing without melting the wire.
Seems like using a lighter to melt the ends would be pretty slow. How long is it taking him per cut and melt on average. How long is it taking him to do say 10 or 20 cut and melts?
You need "nichrome wire" for this type of application ......
Well, no you don't, at least if all you want to cut is webbing or foam. Any metal with some small resistance will work. Some better than others. Copper and Silver will suck because they have such low resistance you have to get more current running through them to heat them up and they get soft at low temps, but for cutting nylon webbing you don't need a very hot wire (comparatively) cotton is harder, but still doable. I'm not sure why you would want to hot cut it since it probably won't fuse.
There are several types of wire that will work. Stainless is one, and is often used in electric space heaters. Stainless has nickel in it (and often Chromium, Vanadium or Manganese) nicrome is largely Nickel and Chromium, as it's name implies.
Even a guitar E string will work.
Google "Stainless steel hot wire cutter" and you will get several commercial products. I believe the one you posted uses a Stainless blade.
Google E string hot wire cutter and at least one instructable will pop up. http://www.instructables.com/id/Guitar-String-Hot-Wire-Cutter/
I've made a foam cutter with a guitar string and a wall wart and a couple high current resistors from Radio Shack.
The key is sizing the Amperage to the wire. Try about 1.7 amps @ 12 volts (abt. 20 watts) through the E string. Use some sort of Spring tension system on the wire. Most metals expand more than nicrome.
Stay away from ordinary steel wire. It will oxidize too fast.
I have a Weller, works great, plus like Mucci says, you DON'T want to break those fumes, and I can walk the little bugger outside with a role of 1" tubular - plug the cutter into the outside outlet on the house and not worry about snuffing out my dog. :-) You can get used ones on ebay, I think mine was @ 20 bucks, but it only came with the rope cutting tip, not the soldering tip. As you want to cut cotton, Werners device might be the correct one. For nylon, the little Weller does a great job.
"The material is cotton with acrylic core. 2.5mm thick and 1.5" and 1.25" wide."
I don't think the Weller will speed up your cotton cutting. Probably just catch it on fire.