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Oct 20, 2017, 10:46 AM
Foamy and Glider fanatic
Blacky's Boy's Avatar

Shop built hot wire foam cutter?

Hey gang,

I've been meaning to make one of those hot wire cutters for a bit now. I've watched a couple of videos online where people have used 12vDC power supplies and an E Guitar string to make their own. While it appears very do-able I'd like to hear from other members that have made their own. The odd thing about looking it up online first is that usually there is a bit more involved that it appears. I'd just like to make a nice sturdy unit that I can use for a couple years.

The bow section seems pretty easy to make. I've made several bow saws (woodworking is my other hobby) and know how to knock something together pretty easily that will maintain the tension and be comfortable to use. Heck, I could probably use some PVC pipe like everyone else seems to use.

As far as power supplies go, I understand that you can modify an old PC power supply. My Reactor Lipo Charger has a "hot wire cutter" setting but I'm not sure I want to use that since it's my primary source of charging. I understand that you really should use a voltage regulator to control how hot the wire gets.

Is there a link to a good "how to" for making your own?
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Oct 20, 2017, 03:26 PM
Registered User
Here is one with a simple variable power supply with a shopping list.
Oct 20, 2017, 04:22 PM
Registered User
ninjasword71's Avatar
I have a CPU power supply cutter. It's very very slow at 24". I use 30 gauge monochrome wire. Thinner wire breaks during cutting. Not efficient at all and barely does the job but was free.
Oct 20, 2017, 09:28 PM
Foamy and Glider fanatic
Blacky's Boy's Avatar
Thanks for the link!
Oct 21, 2017, 12:02 AM
Registered User
psychedvike's Avatar
Here a couple links to videos I made a while back. They might be helpful.
This is a easy way to build a bow. Since your a wood worker it should be right up your alley.
Easy to make hot wire bow with a DIY drill jig (13 min 40 sec)

These are a series of vidos showing a couple different power supplies and some tools you can make for them.
PowerSupplyPart1 (12 min 42 sec)

PowerSupplyPart2 (13 min 3 sec)

PowerSupplyPart3 (8 min 23 sec)

I'm kinda long winded. I think I build better planes than I make videos, but if you can take to amateur video you might be able to use some of the info.
Last edited by psychedvike; Oct 21, 2017 at 12:19 AM. Reason: Wrong links
Oct 21, 2017, 10:21 AM
Registered User
I use the ole door bell transformer, dimmer switch one in my table top one. For the bow, as it is 48 inches long I use a small veriac. That thing would power a 100" bow with ease. But they can be bad for your health if you wire them up wrong. Will give you a shock that will straighten you hair.

Oct 21, 2017, 03:03 PM
Ft Lauderdale
Number_6's Avatar
Previously tried a battery charger and 3 cell batts....not
controllable enough.
Last edited by Number_6; Oct 21, 2017 at 04:50 PM.
Oct 21, 2017, 05:53 PM
Registered User
I have built a foam cutter using stainless steel fishing leader. You can get that at a tackle store. A few dollars for several feet. A 12 volt battery charger for current. It works good at minimum cost.
Oct 21, 2017, 06:59 PM
Retired CAD guy
birdofplay's Avatar
I presume that you have Bing'd for transformers

Plus that site has some nice Safety tips and All the Hookup info

Long cut lengths need more power and will cost $30-40 or more for the tx alone.
Oct 28, 2017, 09:38 AM
Registered User
aymodeler's Avatar
There are many good options. I happened to use this link as my guide, but most are variations on a common theme.

After burning out "bargain" priced transformers, I ended up opting for something a bit more heavy duty:

Also, you can buy a lifetime's supply of high resistance wire on Amazon for next to nothing:
Oct 29, 2017, 10:49 PM
Registered User
Bummed out here. I was in the middle of cutting, oh the foam was flying. I was cutting arts and stacking them up. I was on the last part and I had just started, gone about 2 inches, POP, nothing. Flipped the cutter over and the door bell transformer was SMOKIN HOT!!!!!!!!!!!!!!!!

Well time for a better one or just a small vairac. The transformer is $30-$40, a small Vairac is $55.00? I have a variac, but man that thing weighs 10 pounds. Granted I could heat a wire 20 feet long, the variac was free but setting it up every time is a pain. I will be building a foam table, were I can cut core, shapes at one spot in stead of where ever I have a flat spot not covered in 2 feet of other projects.

Oct 30, 2017, 12:16 AM
Registered User
tspeer's Avatar
Try shopping for a variable DC power supply. It's safe and will let you dial in the amperage you want, so you get consistent cutting and can handle different sizes of cutting bows. I've been happy with mine, and I thought the cost was quite reasonable.
Oct 30, 2017, 11:26 AM
Registered User
That is a nice unit. Would be able to use it for everything I have.

Nov 01, 2017, 08:15 AM
Ft Lauderdale
Number_6's Avatar
Originally Posted by tspeer
Try shopping for a variable DC power supply. It's safe and will let you dial in the amperage you want, so you get consistent cutting and can handle different sizes of cutting bows. I've been happy with mine, and I thought the cost was quite reasonable.
I have this one, OK, but came without power cord
or output cords!

Old computer power cord worked though.
Had some output cables from LIPO charger.

Anyway, all is well now....
Nov 01, 2017, 09:48 AM
Registered User
flypaper 2's Avatar
I 've been cutting with a hotwire for many yrs. I used to have a frame made from a 2 by2 s and 1/4 in. piano wire but after many yrs, decided it was too heavy.
made this one from 1/2 in. plastic hot water pipe.
Pic. is worth a thousand words.


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