Monday, June 7, 2010

Hot wire automated styrofoam circle cutter.

Here's a step-by-step to build your own automated stryrofoam circle cutter for dirt cheap. Mine was free since I had all the parts laying around the shop.

The reason I made this cutter is because I need to cut round pieces of styrofoam that will be glued together to make large pillars.

The automation part is just a windshield wiper motor that is hooked up to a computer power supply . The power needed is 3.3V . 5V and 12V make the motor go too fast. The 12V part of the power supply is for the wire.

The first step is to cut a piece of mdf / particle board ,...or whatever you want to use to the size of the table that you would like .

My table is around 20" wide .

Then position the wiper motor to see where you need to cut your hole so the shank comes out the other side.


I marked where the slot is going to go and the 2 holes on the end .

One hole for the wiper motor , the other because it lookes better :-)

Now is also a good time to cut your angle aluminum to the length that you will need for the gantry to move.

My aluminum pieces are about 12" long.


Drill the holes with a spade bit .

Chamfer the sides of the board like this.

This is where the angled aluminum pieces will go.

Clamp a straight piece of lumber or metal to serve as a guide to cut out the groove where the hot wire will travel through.

Then cut the groove with a router.

Then you mark the position of the windshield wiper motor and drill the holes that are needed to screw the motor onto the board.

Attach the motor with either long bolts or a piece of 1/4" rod with nuts.

After screwing the aluminum pieces into place , your work table should look like this.

I attached 2x4 scrap pieces of wood to the bottom of the table so the motor is suspended plus there'll be enough clearance for the gantry.

Cut some 6" pieces of angled aluminum to accomodate your ball bearings.

The ball bearings will ride on the angled aluminum that is attached to the table and will be the moving part ( gantry ) for the hot wire.

Drill 2 holes per side in the short aluminum pieces to attach the ball bearings.

The inside diameter of the ball bearings are 1/4" . The screws are 2" long.

4 screws , 4 nuts and 4 ball bearings are needed for one setup.

You will need to make two setups.

Cut two strips of MDF ( around 6" wide and 15" long ) that are needed to set the height of the wire. In my case , I don't need more than 12" clearance.

Cut two slots per side and place the setups in the grooves.

Attach using one screw in the center.

Place the two gantry sides on the tracks ( you could use an extra set of hands ) and measure from one side to the other to determine how long you have to cut the top and bottom piece of lumber that will keep your gantry together.

Both top and bottom will need a hole in the center where the wire will go through.

Hand drawn tape measure to give me a clue how big the circle will be.

Attached the motor wires to the 3.3V input of the computer power supply and the hot wire wires to the 12V input.

Cut a couple of pieces with a guitar string as hot wire as a test.

I will need different type of wire plus a spring to keep the wire stretched out while it's hot. That will be something for later.

With the gantry setup , you can roll the wire back and forth to set the diameter for the styrofoam.

The motor keeps the styrofoam spinning so you don't have to do that.


  1. That is super cool! Wow, very creative piece you have there. Anything that makes cutting foam easier is good in my book!


  2. I just wanted to tell you how impressed I am with your Egyptian decorations. I stumbled upon your blog while doing a search for Anubis stuff. I'll be doing an Egyptian themed adult Halloween party in 2011 and am already trying to think of ideas. You have some fantastic stuff!



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