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A Hot-Wire Cutter With Inbuilt Heat Controller

If you've ever tried to cut polystyrene (especially!) and polyurethane materials using a saw, razor blade or knife, you'll know that the results are invariably less than satisfactory. If you are after a clean, precise cut, a hot-wire cutter is the answer. The hot wire actually melts the material and results in a very neat, very fine cut, without the thousands of bits of foam flakes you normally get.

by John Clarke

For modelling, hobby and furniture upholstery work, a hot wire cutter is a must-have.

No more material deformation, no more jagged edges and crooked cuts, no more beads of polystyrene broken off and flying about – and the cut is so much more accurate into the bargain.

But wait, there’s more: this SILICON CHIP Hot Wire Cutter includes a controller to allow the wire temperature to be adjusted to produce a clean cut regardless of the thickness or even the type of material being cut.

Click for larger image
Do we really need to tell you not to touch the hot wire when the cutter is in operation? The wire is HOT. You will get burnt!

It suits a variety of low-melting-point “thermoplastics” but with polystyrene it really comes into its own.

There are two common forms of polystyrene – the beaded type, popular as packaging material and as the “beans” inside beanbags.

When all those beads of polystyrene are extruded into a block, we get the type of “foam” we’re so familiar with. Extruded polystyrene has an enormous variety of uses. It’s widely found in consumer goods packaging, it’s used in modelling, it forms the basis for surfboards and other floating aids and is used as an insulator – sometimes on its own but more often “sandwiched” between two tougher materials, as on its own it’s quite brittle.

Believe it or not, the letters in the photo above were actually cut (using our new Hot Wire Cutter, of course!) from offcuts of 50mm-thick Polystyrene foam used as part of the cladding on the home of one of our staff members.

Polyurethane, at least in the form we are talking about, is often called “foam rubber”, though of course there is no rubber in it.

Its most common usage is for padding in furniture and even car seats. It’s also shaped into many products such as bedding underlays. In its “crumbled” (or crumbed) form it too is used extensively as a packaging material.

Both types of plastic have a relatively low melting point of around 170 - 240°C and both are delightfully easy to cut with a hot-wire cutter.

Other types of plastic that could be cut with a hot wire cutter include PET (eg, soft drink bottles), ABS (eg, “plastic” cases and parts) and clear or coloured Acrylic or Perspex.

We’ll have more to say about cutting these different plastics later.

Our hot wire cutter design

Hot wire cutters are relatively simple and comprise a frame that supports a length of heated resistance wire which is kept taut by some form of spring. The wire needs to be taut so that the cut is straight and the wire does not bend while cutting the material. Tensioning is also required to maintain wire rigidity, as the wire expands when heated.

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