Help! Looking into building a hot wire cutter

[RossFPV]

I want to build a bow slightly over 24 inches to cut 24 inch epp blocks. I would like to use a 3s 2200mah lipo to power it but i can buy a 4s if needed. Im lost when it comes to what nichrome wire to buy. Any ideas?

 

[Slatroni]

The one I made used 120v ac and a light dimer switch. As for wire I used stainless steel safety wire. SS wire is much cheaper and available at the big box stores.

 

[Merv]

Hot wire cutters are very simple, cheap and easy to make. Use whatever materials you have on hand, scrap wood, leftover PVC pipe, etc. Here are a few of mine, I have various size for the task needed. Lightweight frames are the best, very little strength is needed. The smaller frame is the one I use most often, it’s just stiff wire stuck into an scrap board. I added an on off switch for convince.

You can experiment with steel wire from the hardware store. There is no substitute for nichrome wire, it’s hands down the best. The site below has a great selection of wire and transformers, both in various sizes. Also has the calculators to help you pick the size for your needs. I use 26 gauge for cutting straight things like wings. Use 16 gauge for molding shapes, like crown molding or servo pockets. Bend the wire into whatever profile you want and cut away.

I use 12v & 5v transformers with a simple light dimmer switch to control the heat. I also use the same dimmer on my cheap hot glue gun. Full power at first to get it hot, then dial it back to about 60% to keep the glue from boiling.

https://jacobs-online.biz/index.htm

Last edited: Nov 4, 2021

 

[LitterBug]

Great info Merv! I have a couple super old RMRC kits that Don't have servo or battery pockets molded in, but have recommended size/locations in the instructions. Have you ever made some sort of hot knife out of a soldering iron for smaller/detailed work?

 

[Merv]

...Have you ever made some sort of hot knife out of a soldering iron for smaller/detailed work?

Yes, for that kind of work I use the heaver 16 gauge nichrome wire. It will hold whatever shape you bend it.
Simply bend it into the shape you want, attach it to a scrap of wood, hook up the transformer and cut away. Usually takes longer to setup than to cut but is way faster and less mess than other methods.

If I recall the heaver wire uses lower volts and higher amps. Here is a site that I often consult to get the volts & amps in the correct range. Once you have a transformer that will get you close, use the dimmer switch to dial in the wire temp.

Dimmer

Transformers for hot wire foam cutting and other applications. 50VA, 100VA, 150VA. 3V, 6V, 12V, 24V output. Single and dual secondaries

jacobs-online.biz

I highly recommend you spend some time exploring the Jacobs site, he has s lot of good how-to information.

 

[RossFPV]

What temp is recommended for cutting epp? i used a calculator and with nichrome 60 26 gage wire at 24 inches and 12v (3s voltage) it would have 650 degrees

 

[Merv]

I cut XPS, I've never had any access to EPP, I'm guessing it will be similar cutting temp. 650 is going to be very hot, the wire will be bright cherry red. It will cut fast, but the kerf is going to be fairly large. I prefer to cut at a bit lower temp, a dull red wire. I turn the dial on my dimmer switch until it looks about right.

 

[Merv]

I stumbled across this guy a while back. Looks like he has taken hotwire cutting to the next level, CNC controlled. I hope to build one of his machines this year.

https://rckeith.co.uk/

 

[RossFPV]

I cut XPS, I've never had any access to EPP, I'm guessing it will be similar cutting temp. 650 is going to be very hot, the wire will be bright cherry red. It will cut fast, but the kerf is going to be fairly large. I prefer to cut at a bit lower temp, a dull red wire. I turn the dial on my dimmer switch until it looks about right.

How strong is the xps? Im trying to build a super strong combat wing

 

[Merv]

How strong is the xps? Im trying to build a super strong combat wing.

The XPS that I use comes in 4x8 sheets, in my area it’s pink or blue. I’ll use whichever is cheaper. It comes in a variety of thickness, I usually get the 2” thick. I’ve heard there is a green, never used it.

If you lay a sheet on the ground, you can stand on it & not leave a mark. Bang it with a hammer & you can dent it. Covering it with laminating film or fiberglass will make it tougher and lessen the dent of a hammer blow. It definitely needs a spar. There is a lighter foam used under a stucco finish. It comes in a 2x8 sheet, I’m going to try it when I use up my XPS.

 

[RossFPV]

The XPS that I use comes in 4x8 sheets, in my area it’s pink or blue. I’ll use whichever is cheaper. It comes in a variety of thickness, I usually get the 2” thick. I’ve heard there is a green, never used it.

If you lay a sheet on the ground, you can stand on it & not leave a mark. Bang it with a hammer & you can dent it. Covering it with laminating film or fiberglass will make it tougher and lessen the dent of a hammer blow. It definitely needs a spar. There is a lighter foam used under a stucco finish. It comes in a 2x8 sheet, I’m going to try it when I use up my XPS.

Looks like i will use xps for my combat plane and if its too heavy i will get epp, thanks for the help!

 

[RossFPV]

is this everything? I have pvc and i will give it some back-bend so it will be simpler and not need a spring. I will also use a brushed esc and servo tester for temperature control. I feel like i might be missing something but maybe its just that simple.

 

[Draftman1]

When I had one, I used what was called. “Renee” wire.
These guys have it

 

[danskis]

@Squashymoon125 Take a look at this thread.

Fellow hot wire foam cutters, please feel free to weigh in.

I am currently building a 1/5 Gee Bee Sportster using old school methods with a foam core wing. This is my fourth but most challenging wing to date. I am pleased to say that so far, this cutting method I've used worked out very well. I am sure there R many cutters out there & many more who R...

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