Um, new guy with a homebuilt hot wire foam cutter...

[powerlinemanco]

First of all, Hey everyone! I'm pretty new to this awesome hobby, and have been having a ball for the last month scratchbuilding planes and crashing them... lol.

Anyway, I have been creeping around the forums before I registered trying to pickup any useful hints and tips to this hobby to try and make it easier on myself. I have been cutting and building foam planes like crazy for the last few weeks(mainly because I keep crashing them so often) and was going through razor blades like crazy. I started scouring the web thinking there has to be an easier way, when lo and behold I came across a thread somewhere in this group about a hot wire cutter. That sparked my curiosity and I had to begin a search of epic proportions for more detail and information on this device that was to simplify and hasten my return to the skies after each air-to-ground catastrophe...

Here is my solution Its still being tweaked here and there. Mainly I'm trying to find the perfect wire to use with my power supply. I keep having issues with it overheating and the hot wire breaking after a dozen or so cuts. If anyone has any suggestions I would love to hear them. I am currently using a .013 electric guitar string.

Built this puppy with mostly scrap i had in my garage. Had to buy a few things, like a spring, some eye bolts, the alligator clips, and some 14awg wire.
Works pretty well with the 12v power source, but always looking to improve if you guys have any ideas. you all are way ahead of the curve compared to me I'm sure! LOL

Anyway, let me know what you guys think. Would love some feedback!

See you in the skies! (Eventually!)

 

[powerlinemanco]

Here's a few more pics. Used an old computer power supply.

 

[powerlinemanco]

Please disregard the horrible narration. I sent this to a friend who is also getting into the hobby.

 

[Julez]

It's a very band saw-esque hot wire cutter. Very clean build!

One thing- if you're planning to use it like a band saw (Foam resting on the base while cutting) you might want to consider putting something on top of the plywood to avoid getting splinters in or sandpapering the foam

 

[powerlinemanco]

I was thinking of using some spray adhesive and covering the top in posterboard? And Im going to use a fender washer around the wire hole to keep the wire from burning the edges as it stretches.

 

[RAM]

I use nichrome wire. You might be breaking it because it's too hot (it's not red hot is it?) or it's too cold and you are pushing too hard.

Also, did you rig it with a spring? That not only keeps the wire tight as it expands from the heat but it gives a little if you push too hard.

 

[powerlinemanco]

It is getting red hot... would a dimmer switch on the dc side help to control this?

I did rig the spring and it seems to work much better.

Also, what size nichrome?

 

[RAM]

I used 40 gage

and this calculator helps a lot to sort out the distance of wire needed to get the correct temperatures.
http://www.jacobs-online.biz/nichrome/NichromeCalc.html

Also got a lot of ideas from this site. Not exactly what we are doing but good information.
http://www.sciencetoymaker.org/airSurfKit/part6.htm
https://www.youtube.com/watch?v=fxbR2bwnjcw

 

[powerlinemanco]

Awesome! Some great info! Thanks!

 

[willsonman]

Yup, use a spring, and the wire only needs to be hot... not red-hot. My "scroll wire" is a bit smaller than yours so that I can store it more easily and I use a C-clamp on my bench to keep it stable.

I mostly use a bow. I used cheap pieces of aluminum so that it is more rigid (as compared to typical PVC bows). It allows me to adjust the tension on the wire as well. It allows me to cut very wide wing panels but I try to limit myself to 18" at most. They are just better cuts.

For wire I use piano wire. Like from a piano repair shop. While its not nichrome (everyone swears by it) it takes the heat and tension a lot better due to the higher density. Keep in mind that a piano has a combine tension of 2 tons! This wire will take a beating. In my bows I have had the same piece of wire for over 5 years, and I scratch build a lot. Say what you will but I swear by the stuff and you get it for pennies from your local shop.

 

[RAM]

I have a music shop nearby. If I didn't have a lifetime supply of nichrome already that's where I'd be headed today. Which piano wire size are you using wilsonman?

 

[jhitesma]

Are you just feeding it straight 12v from the power supply? That would explain why you keep burning up the wires. You really need some kind of current limiter in there otherwise either the wire is going to burn or the fuse in the power supply is going to.

You can use a brushed ESC with a servo tester as a fairly simple solution.

I use an old adjustable current battery charger from the early 80's designed for Pb and NiCad packs I found laying around.

A dimmer won't really work for this.