I recently acquired two hard cases, one I want to use for my SBR and suppressor (if I ever get it) I started yesterday by laying everything out on the foam, now I'm ready to start cutting.

I work for a defense contractor (aerospace), we purchase and supply Pelican cases with custom foam all day long for our customers, and for whatever reason, we struggle with the foam cutting process. When I first started, we would use knives and electric knives to make the cut outs. A few years ago we bought a laser, and everyone was so excited that we could start using this for the foam. The problem with the laser is it usually melts/ burns the foam beyond use.

So, long story short, I want to build a wire foam cutter for my case, and if everything goes well I would like to make a bigger one that we can use here at work. I did some looking last night on how to make them, but I'm still not real clear on the power source, and the type of wire used.

Has anyone built one? Anyone want to share how they did it and what materials they used?

I seem to remember a pretty good thread in the past that had a lot of detail about hot wire cutting and a poster chronicling his project. See if you can find it in a search, or maybe someone will come along that remembers it better than me...

Pure SWAG, but I suspect if you call Pelican, someone will tell you what wire temp and speed to cut their foam, if you are buying them in bulk

A liquid nitrogen "water jet" would be interesting. I heard of them being used to cut stacks of heavy fabric.

Hot wires are easy to make, and hard to use.

Power source: Variac (variable autotransformer). Uses AC power and changes the voltage, not frequency like a VFD. Router speed controls are an example. You adjust the voltage to suit the wire diameter. Length of wire determines what amperage output you need.

Wire: Nichrome wire, small (.030) works best. Need springs to takeup slack as wire gets hot and expands in length. Most people pass current through strings on handheld units. Obviously, THE BOW MUST BE ELECTRICALLY INSULATED from the wire w/ AC current flowing down it.

I would just buy a pre-made unit from hotwire direct or similar if you don't have a variac.

I just found the Hotwirefoamfacroy.com website! You can buy a scroll style hot wire foam cutter for $60. They even have a 4 axis CNC wire cutter that I'm trying to convince the poweres that be that we need to purchase one for all of our foam work.

Here is a thread you should check out on AR15.com:
https://www.ar15.com/forums/t_3_4/292695_.html&page=1

Keep us updated on how everything goes and what you ended up doing!

If you want to buy something try http://www.mycasebuilder.com/ if you have a case you can just buy the foam. They have a lot of pre-designed cutouts for a lot of popular guns and accessories. Try thier case designer.

If you want to DIY---

I helped a friend make something very similar to the link below. He had made a lot of gun cases molded insides. Instead of the light dimmer I used a motor speed control similar to the second link.

The big thing is to find a transformer. With a good motor speed control that has a finer adjustment you can probably get away with a 24vac secondary transformer.

Otherwise 12 to 14 vac will be the sweet spot. If you have a 9 vac xfmr laying around it may work. I wouldn't order a 9 vac but would try it if you have one.

http://archinect.com/blog/article/21450561/11-06-05-make-your-own-hotwire-foam-cutter

https://www.amazon.com/gp/aw/d/B00OZ5MBM6/ref=pd_aw_sim_60_1?ie=UTF8&psc=1&refRID=FJ6WDYZPXKXKXXWJ2WQN

AgEng06 said:

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I seem to remember a pretty good thread in the past that had a lot of detail about hot wire cutting and a poster chronicling his project. See if you can find it in a search, or maybe someone will come along that remembers it better than me...

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Yeah there is a thread on this topic. Don't remember the poster though.

Here is one of the posts from a couple years ago.

https://texags.com/forums/34/topics/2707010

Here is a more recent one:

https://texags.com/forums/34/topics/2803920

You say a 12-14va transformer is the sweet spot. The wire I bought is 34 ga ni-chrom. with 16.3 ohms. By doing the calculations, I would need a 24v 40va transformer. What type of wire were you using?

I will make my diy wire cutter this weekend, hopefully if everything goes good I should have the case done and I can post some pictures. Thanks for all of the help!

I built one and posted the results in the thread below.

https://texags.com/forums/34/topics/2707010

Most of the literature I found showed 26ga to be a good middle of the road thickness for nichrome based on my wire length. Supposedly it wouldn't get too hot to warp or deform/break, but wasn't so thick to require a beefy power source.

Whichever route you go, make sure you get a power source that's got enough juice, as you don't want to run it through with too little and have to go slow as molasses. Jacobs Online has some great reading material and is where I got most of my gear.

I've made a few modifications to my board from the original thread:
- I added additional 2'x2' leaves attached on the edges via small hinges that fold over to a 2'x4' work surface in compact mode and open up to 2'x8' in extended mode. One thing I noticed on the smaller table top was that it was a pain to run a long 1750 size pelican sheet through the burner without it getting hung up on the side or flopping off the other end and making it harder to run it through the wire straight.
- Also added some 100lb drawer slides on the underside that slide out and catch the leaves when they open up. Had a coupon to Rockler an they were on sale so they cost me about $8 for the pair.
- Added some velcro strips to keep the leaves closed when in transit. Not that I've ever taken the thing anywhere since it's pretty damn heavy at this point...but it does keep it tidy when moving it around the garage.
- Waxed the heck out of it to make it a lot slicker so my foam would glide easier. This really helped and was a lot cheaper than coating in formica, plexi or similar.
- Need to add a counter tension arm on the pvc to keep the cutting arm tight. The pvc has a little more play than I'd like and I can only add so much tension on the wire side via springs before the pvc arm starts to dip over the board surface.
- Also need to add flames to it since everything looks cooler with flames.

Anyway, thanks for resurrecting this topic! I got started laying out another set of foam sheets but never got around to cutting it a while back. Maybe it'll give me something to do this weekend.

civilized05 said:

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- Also need to add flames to it since everything looks cooler with flames.

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why haven't I thought of this already?!? I will add the coolest flame job you've ever seen!!

Thanks for posting, that's a lot of good info.

It was nichrome 80, 26 gauge wire. 24 vac will work, especially with a dimmer or some kind of "speed" control. After using it 14 volts was a bit too hot for us.