Quick/easy and (almost) free hotwire cutter for foam!

[sl33py]

There are quite a few hot wire kits and how-to's out there...

It's not rocket science - some simple nichrome wire and set the voltage/amps for temperature you want.

I was going to fab up a nice sturdy spreader to keep the wire tensioned, but figured a quick cut or two on the foam to get it to a more manageable size would make it easier.

Let's make it simple - you get a certain gauge of nichrome wire which has a known (or measured) resistance. You then use a measured length (or measure resistance of your length), and use a power supply with that voltage/amps to get your target heat to cut through the foam.

For a good calculator:
Do the math or use the calculator here.

Here's the cheatsheet on the wire gauge, length, and volts/amps needed for your temp range. (hotter cuts faster - not rocket science).

Inexpensive "vape" wire - $9.50 for 100 feet!

Now to my "fancy" setup...

I just took some of the 28g nichrome wire and strung it on this bike rack (was using as a place to set my board). Insulated and worked pretty well if i do say myself. Leaves my hands free to keep the cuts reasonably straight.

So $10 and the cost of the lab power supply i already had. You can do the calculations and easily find a 5v 2a (like just about every USB phone charger around now). You can do the calcs and add some resistors to fine tune your temp. Lots of options!

I plan on getting a table top setup for this next. Just to make it easier to keep tension and 90* perpendicular/square cuts. I'm planning to use the foam for both GF/CF layup and vacuum molds for Kydex/ABS. So i want to get it close and then finish sand it to the shape i want. The better it looks the better the forms will work out.

OK, you can now proceed to make fun of my messy bench!

 

[Living E Caveman]

I got a nice glow by touching two USB cable wires together as I tried to charge a 3v battery. This stuff is what I dig. Like making my own heated jacket, with insulated resistance wire tho. Thanks for the post

 

[sl33py]

v2:

Harbor freight wooden clamp - you can tighten the bottom which spreads the jaws and tensions the wire nicely! Let's you get it to "twang" and further tighten it later as needed.

Same power supply and alligator clamps to the wire. I need a slightly deeper "C" clamp to get it flush with the work bench next. I can take it apart in just a few seconds and use the clamp normally, then just set it up when i need to cut foam. Handy!

Clamp was ~$12 iirc.

 

[sl33py]

v3!

As part of a vacuum table workbench extension, I setup the hotwire cutter on the end where i can use it when needed and take it off when not needed. Very simple setup but works really well it seems!

I took some 1" wide and ~12" long wood pieces i had kicking around. Add in a couple eye bolts and a small turnbuckle to tension the wire:

Super simple and what i had laying around! Works perfect to tension the wire to a "twang!".

Plenty of working room for my needs - 8" deep and 12" long wire / height.

Top and bottom. Top is slotted to let the wire go in with the wooden dowel (or scrap i had). Bottom similarly around a dowel with clip closest to table (on both - why heat the wire going around your dowel/block? - instead it is below the top dowel and above the bottom dowel)

Somewhat dry run:

Playing with angles - a bit of sanding yet to do before i'd mold or fiberglass over it...

Here's what i was thinking - A protective cover (angles to deflect impact) to put the Rx and ESC) VESC and XERUN for scale.

Rough but i think with a bit more practice and some sanding of these it would work great!

 

[okp]

nice piece of art ! take care about your truck/motor clearance vs the enclosure. I would also definitely add some smooth curved borders

go epoxying !!!

 

[Vulthor]

Hey Sl33py that sounds good, soon you will make art pieces like okp .

 

[sl33py]

nice piece of art ! take care about your truck/motor clearance vs the enclosure. I would also definitely add some smooth curved borders

go epoxying !!!

I just set it for scale and it wouldn't be that far back near the motor. I got some decent angles - just need to sand it a bit before doing anything. It's all your fault okp...

 

[akiraEC]

These are some really clean cuts.
I have never been able to cut it as straight as you !!

 

[sl33py]

These are some really clean cuts.
I have never been able to cut it as straight as you !!

Thanks Akira! That was kind of my goal - getting nice smooth/clean cuts. I'll still need to sand quite a bit, but a nice flat start makes it sooo much easier. My biggest issue is that it's not symmetrical... (i have issues if it doesn't balance - my own OCD).

I used a wooden dowel, a speed square, and a small clamp to hold the wood guide in place. Having it on the smooth surface and both hands to guide definitely made it much easier!

You've literally seen my first cut to this first attempt to do it super straight. I know i can do better (symmetric), but pleased with the first attempt! I'll be refining and getting better with this. It's only two bolts and unwind one end to pull it through the hole - relatively quick and easy to setup/breakdown!

 

[Kin]

Do you get a lot of cycling, or do you pretty much turn on your wire once then let it run hot until you're done?

I ask because my experience with tightening after hot, is that the wire ended up snapping a lot. I thought perhaps it was the stress from when it cools down and becomes taught. In my case it was being turned on and off a couple times while using it.

 

[sl33py]

Kim - limited use so far and the wire is seriously tight. No breaking yet.

I do power it off if won't use it for a little while.

 

[okp]

awesome ! can't wait to see it evolving