Super Simple Hotwire Cutter

Hotwire cutters are useful for cutting all sorts of materials. Although they are not too tricky to make there can take a bit of guesswork to build something portable and easy to construct. This super simple wire cutter just uses an old computer power supply (or laptop supply) and tension from a PLA/ABS bow to keep the wire tight. No springs or funky tension systems are required just cut your nichrome to length. 

An inexpensive speed controller allows you to get the temperature perfect and the rest can be easily found around your shed. I made mine from scraps!

Some 3D printing is required.

20 × Self tapping countersunk wood screws 13x3

10 × Self tapping countersunk wood screws 25x3

2 × M4 x 10 screws with wingnuts

1 × M4 x 15 with wingnut

1 × M6 x 40 bolt and wing nut

1 × M4 x 100 + 3 nuts and washers

2 × Wood or acrylic 200x300

1 × Motor controller (12V tolerant)

1 × Red and black hookup wire approx 1 meter of each

1 × Wood framing. I used 18x40mm wood but you could use anything around this size.

1 × 3D printed parts, check files.

1 × Nichrome wire approx 300mm

1 × Banana terminals 1 black, 1 red

1 × Computer or laptop power supply.

• Any supply will do, even one from a laptop.
• The red wire from a desktop supply is the 12 v
• Some power supplies might need a ballast mine did not. More details here: https://www.instructables.com/Computer-Power-Supply-to-Bench-Power-Supply-Adapte/

1 x 10mm washer

All STLs are here: https://jasonwinfield.nz/my-stls/

Cut your wood to the dimensions shown in the picture above. I used 18x40mm wood for this project. Don't join the frame together yet.

Join the two sides and the back of the frame together only. I used long wood screws and glue for a strong frame. 

I used some scrap material I had around my workshop both around 5mm thick. You can either print the SVGs I supplied and use these as a template or mark out the dimensions shown above. 

Attach the baseboard to the frame with screws and wood glue. Assemble your bow (I don't have the bolts in the picture) Use the M6 bolt and wingnut and the M4 bolt and wingnut. The right-hand side of the bow (from the back) should be 93mm from the edge of the frame (see picture). Mark the holes with a pen. The hole in the center of the mount is for the wire to the top of the bow. 

Center the terminal plate where you like on the back of the frame and mark the holes out.

Drill out the holes for the screws with a 1-2mm drill to prevent the wood splitting. The larger holes should match the size of your banana terminals.

With the last piece of cut, framing mount the bottom tension point. It should be 67mm from the edge of the frame (see picture) also drill a hole in the frame where you like. This is for the wiring to the speed controller. Drill holes on either side of the tension point for the screws. This part should move up and down freely. Drill a 4mm hole in the middle slot for the tension bolt. 

Prepare your nichrome wire with a loop in the end. Feed the long M4 bolt from the back and use one of the bolts to hold the bracket in place. Between two other nuts place the nichrome wire so the wire is in the middle of the hole at the top of the bracket.

Place the bottom framing with the tension bolt into the rest of the framing. Tighten the nichrome wire around the top of the bow with enough tension that the wire is tight. 

The wire gets hot and PLA doesn't like hot so you should use a locking bolt like on the bottom tension point to absorb any heat. Then add a further locking nut. 

Move this framing back and forward until the wire is at 90 degrees to the rest of the frame. Use a square if you need to check this. Mark the position on the frame and drill the last piece of framing in place.  

Potentially you may need to move the bottom mount bolt left or right to get the correct angle. Later this plate will be screwed in place.

Using a ruler measure the distance between the cutting wire from the back and side of the frame. 

Mark this same distance out on the top board and drill a 12mm hole. 

Screw in the front facia and check the speed controller for enough space. 

Run the positive and negative wires from the back of the frame to the speed controller input. Check your speed controller as the contacts can vary. Run the negative wire from the output to the bottom tension bolt. Run the positive wire from the output of the speed controller to the back of the frame through the hole drilled earlier. 

Run the wire from the back of the frame to the top of the bow.

Remove the cutting wire and place the top cover, screw this down in place. The bottom tension point can now be moved in place. Screw two further wood screws on either side of the mounting plate to fix it in position. Place a 10mm washer inside the top of the bottom mounting plate. This prevents the wire from cutting the PLA/ABS when it is pushed against it. 

Install the guide rails with the remaining screws and wingnuts

Lastly, place the bottom inspection panel on and rubber feet on each corner.

Run 12V from a computer power supply to the terminals at the back of the frame.

Check my video but essentially you turn your speed controller up until it cuts the material you are using. It generally doesn't take much power to do this. 

Move the guides back and forward to get the thickness you need. 

When not in use always drop the bow down to prevent any tension from being lost and easy storage. 

Check out my site for more of my projects https://jasonwinfield.nz/