Hot wire cutters are tools for cutting polystyrene foam and seem to be objects of desire for those terrain modellers who don't own one, while being a source of endless entertainment for those who do.
This document explains how they work, how to used them, and what to look for if you're thinking of buying one. TerraGenesis has a number of other documents about hot wire cutters including reviews, a list of sources, and instructions for making your own. Direct links to these articles are provided at the bottom of the page.
Hot wire cutters work by heating a thin wire, with a low voltage power supply, thus enabling the foam to be sliced and sculpted very easily. You can buy hand held and table top versions. Table top versions are usually mains powered while hand held versions are sometimes mains powered and sometimes powered by batteries.
The important points to note are:
The wire is heated using a LOW VOLTAGE. We've seen instructions on the web for making your own using mains voltage to heat the wire. Never, never, never attempt this. Commercially available mains powered hot wire cutters use a transformer to reduce the mains voltage such that the voltage flowing through the wire is only about 12v.
Most hot wire cutters use special nichrome (nickel chrome) wire. Some, like the Styrocut 3D, use ordinary steel wire but these are exceptions. Nichrome wire looks about like fuse wire, but it isn't. Please don't try making your own hot wire cutter using fuse wire. It won't work. You'll simply short out your battery/power supply.
Hot wire cutters 'cut' by melting their way through the foam. They are intended for use with polystrene foam and don't work with upholstery type sponge foam, polyurethane foam, hard plastic, or most other things that you might consider trying. They are designed to cut polystyrene foam.
Hot wire cutters 'cut' by melting their way through the foam and this has a number of implications:
Perhaps the first thing to understand is that the action of cutting 'takes' heat from the wire cooling it down and thus slowing down the speed at which it melts its way through the foam. Thus you can cut through a thin sheet more quickly than a thick one. Denser foam also takes longer to cut. Most of the time this won't be an issue but if you're planning to cut up lots of big sheets you might find that you'd be better off using a band saw.
It also follows that you need to present the foam to the wire as the correct speed. It's not 'super-critical' but if you go too quickly you will break the wire. If you go too slowly then the cut will be wider because you will be giving it more time to melt the surrounding foam. This also increases the risk of creating hazardous fumes (see below).
Hazardous fumes are probably the most important consideration when using a hot wire cutter. Good ventilation will overcome the problem however Gary has track down some interesting information about this hazard and we strongly recommend that anyone who uses, or who is thinking of using, a hot wire cutter takes a good look at it. We've linked to it here and again at the bottom of the page.
A final safety consideration relates to the fact that the wire is hot. As cutting tools go, hot wire cutters are pretty safe. You might manage to burn your fingers a bit if you're clumsy but you're not going to chop them off. Neither will you be able to electrocute yourself as the voltage passing through the wire is way too low for that. The most important consideration relating to the hot wire is therefore: where you put it when you've stopped cutting.
This is not so much of an issue for table top cutters, and some commercial hand held devices (such as the Woodland Scenics cutter) have a switch that you engage when you're cutting and release as soon as you stop. If you buy a cutter that doesn't have such a switch then be careful where you put it down when you stop cutting.
It is in fact good practice to switch off ANY hot wire cutter when you finish making a cut. Apart from the safety issues, this will reduce the chances of the wire overheating and increase its lifespan.
There's something addictive about hot wire cutters and you'll probably find yourself cutting bits of foam up just for the sake of it. If your cutter is mains powered this isn't going to be a problem (until you run out of foam) but if you are using batteries...
Heating a wire uses quite a bit of power (when compared to lighting a torch bulb or powering a pocket calculator). We're not talking huge bills from the electricity company, most hot wire cutters use less than a household lightbulb, but if you are trying to run it from ordinary household batteries you can expect to go through quite a lot of them.
In my time I have used a number of hot wire cutters and the cheapest one that I can recommend is the Woodland Scenics (currently about 30 UKP). Quite honestly, if you can't justify the cost of one of those then you're better using a bread knife for big cuts and a scalpel for small cuts. I have used used a number of cheaper, battery powered units, including the one from Games Workshop, and in my opinion they are suitable only for very occasional, light use, and considering the cost of batteries, a waste of money that would have been better spent on a decent hot wire cutter... IF you actually need one.
That said, here are a few other things to consider when thinking of making a purchase:
Hand held or table top? Be realistic about what you plan to use it for. Table top models are much easier to use as you have both hands free to manipulate the workpiece, however they are about three times more expensive than a decent hand held version. Bear in mind that there are also occasions when you can use a hand held but it would be impractical to used a table top model i.e. when you're sculpting something 'in situ'.
Length of wire and throat depth. Again, be realistic about what you intend to use the cutter for. I personally own both a Woodland Scenics hand held cutter and a StyroCut 3D and swap between them depending on the job in hand. However, when I have large or thick sheets to cut up I do it on a scroll-saw. The hot wire cutters are just too slow. Hot wire cutters come into their own for sculpting, not bulk cutting. Given that, you probably won't need a huge throat depth or length of wire.
Consider the position of the on/off switch. The Woodland Scenics cutter has the switch on the handle. You push it to the on position when you want to make a cut and when you stop cutting and release it, it slides back to the off position. This means that you can put it down safely as the wire cools very quickly. I find this very convenient. Some table top cutters have a footswitch which is a very convenient feature.
What type of wire does it use and where can you get more? If you don't feed the foam into the cutter so quickly that you are pushing against the wire (as opposed to giving it time to melt it's way through the foam), and you switch off when you're not using it (so it doesn't overheat) the wire will last quite a long time, but you WILL need to replace it. Make sure that replacement wire is availble.
If it uses batteries, where can you get them. I once had a cheap battery powered cutter that used a weird shaped 4.5v battery which was really difficult to get hold of.
Anyone who uses, or who is thinking of using, a hot wire cutter should read this information about the potential hazard from toxic fumes.
Check out our Reviews Section for reviews of the Woodland Scenics Hotwire Cutter, the StryoCut 3D and the Hot Wire Foam Factory 3-in-1 Kit.
Click here for our international list of sources for hot wire cutters and nichrome wire.
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TerraGenesis was created in 1997 by Gary James and is currently owned, edited and maintained by Andy Slater, however the ideas and opinions expressed are those of the individual contributors. TerraGenesis and its content are © Andy Slater, unless otherwise stated, and should not be reproduced without permission.
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