Saturday, 23 February 2013

Hot Wire Polystyrene Cutter

There are definitely two schools of thought when it comes to carving polystyrene. On the one hand, there is the sharp knife, saw, rasp and sandpaper camp. The benefits of using hand tools is that you have the pleasure of being able to handle your material and the designs can be more organic. The down side to this method is … polystyrene dust. I have seen some truly awesome models using this method of carving. On the other hand, there is the hot wire camp. Hot wire gives you a clean, crisp. The down side there are fumes from burning polystyrene.

I’ve tried using the saw and knife method and, clean-up is a pain in the ass. I used to have a little hand-held hot knife that I used to use for making terrain for wargaming. It was a little 9V battery in a plastic grip connected to a U bar with a wire running between the ends of the U. This was a pretty easy way to cut polystyrene.

Finish is the other determining factor with the choice of methods. Knife, rasp and sandpaper leaves you with a rough surface. Hot wire leaves you with a sealed surface … but one that has been melted.

I’ve decided to make a bench hot wire cutter. The machine will have a opening that is about 12” high and the bench itself will be about 12” x 24”. The first job is to make the body of the cutter. This is basically a 12” x 24” box with a L shaped box added to the short end. The L has a hole in it for the wire to pass through and the bed has a hole that takes the other end of the wire.


Add a wall adapter, a fuse and a switch and we should be away.

I had an old mobile phone charger (5V) which is, basically an AC to DC transformer that steps the power down from 240 to 5V. I’ve cut the plug from the end of the adapter and exposed the two wires (black and green). I have soldered a red wire to the green and a black wire to the black wire of the adapter.

I’ll put an in-line fuse into the wire and mount a switch onto the arm so that I can easily turn the cutter off.

The cutting wire attaches between the red and black wires to complete the circuit. I am planning on using fine steel guitar string as the cutting wire, so I’ll either take one off the Fender, or go and buy another one.

I plan to put a spring loaded connector at both the top and bottom attachment points to that the cutting wire is held taught.

Today I did the timber work. I had some old plywood sitting around with nothing to do, so I did some cutting, gluing and screwing in the workshop. Tomorrow it’s back to the electrical store to get a switch and fuse. If the music store is open tomorrow (Sunday in Hobart) then I’ll get a guitar string as well.


To get the position of the wire hole in the base, I had the arm detached and positioned in the right place in relation to the body, but with the arm resting on the base and then drilled a pilot hole through the arm and base at the same time.

The arm is attached to the base with four bolts that pass through the inner wall of the arm and then into the wall of the base. I want the arm to be able to be removed for when I want to store the tool on the shelf.


Well … now I’m going to go to the electronic store and get some more electronic stuff to make the hot wire circuitry. If they have NiChrome wire at the store, I’ll get that instead of using a guitar string.

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