Hot Wire Current

[spitzy]

Just started cutting out large blocks of foam for my canard using the straigh templates I made. (masonite templates seem to work better than wood)... Anyway, I set the temperature per the video (using a small piece of foam to adjust cutting speed) but when it's time to cut the foam on a large piece there seems to be a pretty big sag in the middle of the wire. I don't like how long it takes for the middle of the wire to come out of the foam once each side is out. If I don't push the hot wire through the foam it REALLY seems to cut slow. Also, the foam cuts much slower as the piece to be cut gets bigger.

 

Has anyone recorded an optimal current per span of cut using the .032 SS safety wire supplied by aircraft spruce?

 

I'm making 70" cuts using a very acurate 3.6 amp dc current through the .032 wire. This is resulting in what I "think" is a slow cut...

[Kent Ashton]

Can't answer your question but here are a couple of tips that might help:

-Let the wire temperature stabilize before you start a cut.

-tighten the wire after the temp. stabilizes

-the wire will cool in the foam, so expect the cut-rate to slow down after about 3/4 to 1 inch.

-if you are using wood templates, you might put some 1/4 inch copper tape--available from stained glass shops--over the edge of the templates to make the wire run smoothly over the templates. Personally, I like formica templates.

-when you pause at corners, listen for the hiss to stop, then move on

- Replace the wire after a few cuts so it doesn't thinout and break.

- don't force it. Just gentle pressure. Let the wire do the work

[Wayne Hicks]

Sounds like you're getting wire sag. Try these:

 

(1) Use a bigger wire. I used 0.041 iconel wire with good results.

 

(2) Tighten the hell out it, like Kent said.

 

(3) Run the wire hotter. Not a lot hotter, but hotter than when testing the hotness with the small piece of foam. You will hear a sizzling when the wire enters the foam block

 

(4) Go a little bit slower. It should feel like you're guiding the wire along. If it feels like you're pulling the wire through, you're probably moving the wire too fast. That definitely causes wire sag.

 

Click here for my other hotwire tips.

[Jerry Schneider]

If I could add a little to the "tighten" technique:

 

1) Turn the power on.

 

2) Tighten while strumming the wire 'till the pitch doesn't go up any more. (Torque-to-Yield)

 

3) Make your cuts.

 

4) LOOSEN the wire as you turn off the power.

 

#4 is very important if you don't want to break wires. I've never broken a wire using this technique. The only time I had any sag, is when I tried to cut too fast. Patience, Grasshopper!