Foam cutter

[tossedman]

I've been meaning to make a hot wire table foam cutter for a long time now and finally got around to it this afternoon. I found instructions on the inter webs and after an hour or so of putzing around and running to the hardware store to get a bolt I came up with this. I'm pleased with the initial testing and will be using this to create the base for my Ochinomizu layout. All told it cost me 9¢ (that's 8¢ to you Yanks, 9¢ to the Aussies, 9¥ to our Japanese readers....) as I had everything else kicking around the house.

 

Edited February 23, 2020 by tossedman
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[cteno4]

Todd,

 

Very cool! These are great. So simple but sooo useful!

 

At the aquarium long ago I cut gobs of foam with home made cutters like this to make mock up rock faces. Once you get the basic components you can make all sorts of them to carve up foam so easily!

 

Will be fun to see your creations with this!

 

Btw you can also use a sand blaster on the foam as well! Takes playing with the pressure and the boasting medium, but you can do some nice carving.

 

Jeff

[Bernard]

tossedman - Great idea and I'm only 8 years late in doing this idea :)

[tossedman]

Yeah, I've been thinking about it for about that long as well. The time had finally come I guess.

 

Todd

[cteno4]

I've been lazy at making one for larger cuts like this as i usually use the table saw or band saw, but thats sort of pushing in pins with a hammer! cuts better than cutting butter, when I've tried the butter on the table saw it tends to just fly everywhere. I should get off my ass and make a table one like this! 

 

jeff

[gavino200]

Any feedback on this? Did it work well? Have you made any changes? Anything you would have done differently? Do you use this for all your work or do you also use a hand-held foam cutter?

 

I'm thinking of making one of these. but I imagine that I'll need a handheld as well.

[gavino200]

I'm thinking of getting a free-hand cutter like this. Anyone have any opinions on this or other hot wire cutters?

 

https://www.micromark.com/Freehand-Router

 

Also, is the wire always thin like this? Is it possible to make a hot cutter that is molded into a defined shape (like a tunnel cross-section). Idea would be to construct a cutting table and then spin a section of foam through it fixed at a pivot point the same distance from the cutter as the radius of the track. Anyone think this is a viable idea? Pure madness?

[gavino200]

Precision foam cutter?? Wouldn't a soldering iron work just as well?

 

https://www.micromark.com/Precision-Engraver

[gavino200]

What would be considered the basic necessary foam cutting tool-set?

[Kiha66]

Back in high school we had one of the homemade cutters, it worked pretty well.  I may have to make one of my own over the winter break.

[cteno4]

Soldering irons are messy for foam cutt8ngnanusually much too hot. 

 

There are two two kinds of hot cutters, the blade or rod ones where it all heats up to cut and the wire cutters where a strip of nichrome wire heats up. Both are useful. The hot knifes are nice to do basic hacking 

 

https://www.harborfreight.com/130-watt-heavy-duty-hot-knife-61423.html

 

some of the rod cutters you can bend up to make a shape of you need to say cut a particular shaped culvert uniformly.

 

the wire cutters basically apply power to each end of the wire to heat it up. Good for doing long cuts or forming things in slabs or scroll sawing.

 

i did gobs of foam cutting years ago when we were mocking up lots of fake rockwork for the aquarium. Hot cutters were good for working with big slabs and knocking out a big crude shape, but for most of the carving it was more useful to use rough rasps, sand papers, and serrated steak knives. Rotary tool with sanding drums, grinding discs and saw blades also helps.

 

one issue with using hot cutters is it does tend to form a very tough skin where you cut that can be hard to shape well then with sandpaper and rasps. That’s why if you whack out a shape with a hot wire cutter it’s good to cut wide to remove these hard bits.

 

Before you get into too much give a try with some foam with a hacksaw blade, serrated steak knife, sand paper and rasps. They can really work well. Also some speak to you better than others, so see what works for you.

 

jeff

[inobu]

Your best bet is Woodland Scenic Hot wire cutter. After using it a while you will get a better understanding of how it works and make your own tools. I used Woodscenics hotwire cutter and Kato Blue power pack to make this.

This is an O Scale viaduct made out of Pink foam

 

 

Inobu

 

 

[gavino200]

This is an interesting product. It's a bit pricey though. 

 

https://hotwirefoamfactory.com/035I-Sled-For-Industrial-Knife.html

 

I bet I could "Jerry-rig" something like this.

 

Cheaper source for hot knife

 

https://www.walmart.com/ip/OUTERDO-Hot-Knife-STYROCUTTER-230-Watt-Electric-Foam-Knife-Styrofoam-Cutter-VARIOUS-KIT/885397314?wmlspartner=wlpa&selectedSellerId=15784&adid=22222222227093580386&wmlspartner=wmtlabs&wl0=&wl1=s&wl2=c&wl3=207476996781&wl4=pla-338484670697&wl5=9024571&wl6=&wl7=&wl8=&wl9=pla&wl10=118780321&wl11=online&wl12=885397314&wl13=&veh=sem

 

If the sled construct were build upside down, it be possible to pin a piece of foamboard down with a nail at one point and rotate it through the hot knife assembly to make a curved fixed-radius circular custom outline cut.

 

Of course, I'll hold on this until I've build up some skill with the basic hot wire cutter and sand paper.

[cteno4]

Yep it’s pretty easy to make your own. Circle cutter is easy like you say, vertical wire on a deep bow and then pivot nail to run the foam around past the blade. You might be able to make your tunnel cross section in thick wire or blade and then even cut the circular tunnel, but that’s going to be challenging combo to get it all just perfect.

 

one thing to note is the glue layer does not tend to cut the same as the foam. Pva is the roughest and liquid nails not quite as bad, but it is something to test in any cutting set up you want more perfect cuts as it can behave differently depending on glue and how you hit the seam with the wire.

 

jeff

[gavino200]

7 minutes ago, cteno4 said:

Yep it’s pretty easy to make your own. Circle cutter is easy like you say, vertical wire on a deep bow and then pivot nail to run the foam around past the blade. You might be able to make your tunnel cross section in thick wire or blade and then even cut the circular tunnel, but that’s going to be challenging combo to get it all just perfect.

 

one thing to note is the glue layer does not tend to cut the same as the foam. Pva is the roughest and liquid nails not quite as bad, but it is something to test in any cutting set up you want more perfect cuts as it can behave differently depending on glue and how you hit the seam with the wire.

 

jeff

 

Have you heard anything about this trick, using the "Gripper" paint instead of glue?

 

https://makezine.com/2016/07/21/sb-styrofoam/

[cteno4]

No but sounds very promising and the best on all fronts of drying between sheets, gripping, shaping and not thick. Gunna have to get a pint and try! Nice find. Maker world is really adding new thoughts and dimensions onto the hobby.

 

Gorilla glue is a hard expanding polyurethane which grips well but does expand and is very crusty to cut and shape and very very sticky mess when using. It also does not keep well once open for long periods, so best bought in small bottle unless you use a lot or often. But it is a very strong glue and versatile.

 

liquid nails has the problem that it’s thick and hard to get a thin layer to cleanly bond two sheets together. Spreading it with a putty knife is not easy and even then it’s usually a em plus joint. Really is made to take up space in joint of foam to rougher surface and gap in joint is no issue.

 

Cheers

 

jeff

[tossedman]

On 2017-12-07 at 6:20 PM, gavino200 said:

Any feedback on this? Did it work well? Have you made any changes? Anything you would have done differently? Do you use this for all your work or do you also use a hand-held foam cutter?

 

I'm thinking of making one of these. but I imagine that I'll need a handheld as well.

Yeah, this works great. Haven’t made any changes. If I was working on a big layout I’d make it a bit deeper but it works fine so far. 

[tossedman]

On 2017-12-16 at 10:26 AM, gavino200 said:

This is an interesting product. It's a bit pricey though. 

 

https://hotwirefoamfactory.com/035I-Sled-For-Industrial-Knife.html

 

I bet I could "Jerry-rig" something like this.

 

Cheaper source for hot knife

 

https://www.walmart.com/ip/OUTERDO-Hot-Knife-STYROCUTTER-230-Watt-Electric-Foam-Knife-Styrofoam-Cutter-VARIOUS-KIT/885397314?wmlspartner=wlpa&selectedSellerId=15784&adid=22222222227093580386&wmlspartner=wmtlabs&wl0=&wl1=s&wl2=c&wl3=207476996781&wl4=pla-338484670697&wl5=9024571&wl6=&wl7=&wl8=&wl9=pla&wl10=118780321&wl11=online&wl12=885397314&wl13=&veh=sem

 

If the sled construct were build upside down, it be possible to pin a piece of foamboard down with a nail at one point and rotate it through the hot knife assembly to make a curved fixed-radius circular custom outline cut.

 

Of course, I'll hold on this until I've build up some skill with the basic hot wire cutter and sand paper.

 

Now that sled is cool!

 

[inobu]

There are an inherent problem with these types of cutters.

 

In order to achieve these shapes you need thicker gauge wire. The thicker wire requires more current which drives the temps way up. This temperature starts to radiate heat around the wire which melts through the foam instead cutting through it. You cannot control the cuts any longer and the speed need to be increased and regulated. It becomes difficult to control.

 

The second problem is higher temps cause foam in some foams to become toxic.

 

Inobu

[cteno4]

Yes this is the juggle you have to do with the nicrome wires getting thickness, stiffness, resistance, and power right to get in the right range to cut well. Can’t always get the permutation you want.

 

always work in a super ventilated area or best outside when cutting foam as it does throw off noxious fumes at most all cutting temps. Just having a fan blowing is not enough if you are doing a lot of cutting as it does throw off a lot of fumes.

 

personally I rarely use hot cutting with foam as I usually find it easier to whack it up with power saws, steak knifes, sandpaper etc as it’s easy and just fits how I’m use to working with materials. It is messier this way though and requires good dust collection and vacuuming! I find you really have to do the final work by abrasion so you are going to make a mess anyway in the end!

 

I did a huge gob of hot wire cutting ages ago but we were building large 1:1 mock ups of big rock walls so it was fast and easy for the giant hacks and whacks we were doing and many times didn’t need fine details as many got shot with FRC and that surface textured with latex rock moulds. Even then when we needed any surface detail we did it all with low pressure sand blaster and crushed walnut shells. The sand blasting technique did not like the hard melted bits on the foam. So we usually roughed up the hot cut areas with 60-80 grit sand paper back to foam before sand blasting.

 

jeff

[cteno4]

interesting i just stumbled across this woodland scenics foam putty in an amazon email of all places. Ive never seen it but looks great to fill in where needed and sands like foam does!

 

https://woodlandscenics.woodlandscenics.com/show/video/FoamPutty

 

jeff

[gavino200]

7 minutes ago, cteno4 said:

interesting i just stumbled across this woodland scenics foam putty in an amazon email of all places. Ive never seen it but looks great to fill in where needed and sands like foam does!

 

https://woodlandscenics.woodlandscenics.com/show/video/FoamPutty

 

jeff

 

Looks useful, thanks!