Introduction: Plywood Hot Wire Foam Cutter

About: Mechanical Engineering student that likes robots, CNC, 3D printing and more.

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Styrofoam is a great material and can be used for many things like prototyping, prop making and even RC airplanes. Cutting styrofoam can be very tricky though. The best tool for this is a hot wire foam cutter. I wanted to be able to recycle styrofoam for future projects, so I decided to make my own.

A hot wire foam cutter is fairly easy to make and many people have done so already. I didn't want to just copy someone else's design, so I designed my own with the best features I could think of. I tried to make it look cool as well and also added laser engravings to the table!

This project was designed to be cut on a CNC router, but can definitely be made by hand! I have included all of the design files, so you can make your own. Let's get started!

Always cut styrofoam in a well ventilated area, you don't want to breath in the fumes. The wire is HOT, don't touch it!

Step 1: Design and Features


Because I wanted to use my CNC router to make all the parts for this project, I had to make a 'complete' drawing in Solidworks. This project is fairly simple, but I wanted to make it look good as well. As you can see I added a lot of curves and other features to the parts that are mainly aesthetic. It looks kinda like a spaceship (with enough imagination..), which I think is pretty cool! I exported all the parts as DXF files (see next step), so I could create the toolpaths for the CNC router. I have included the drawings I made below.


  • Cut capacity
    This foam cutter can cut a maximum height of 200mm and 200mm wide.
  • Fence
    It features an adjustable fence that allows you to make accurate straight cuts
  • Laser engraved table
    Laser engraved markings on the table allow you to set the fence at an accurate distance from the cutting wire. The table also has an Instructables logo on it :)!
  • Metal table protector
    A removable metal washer, protects the table from accidental burnings.
  • Spring tensioner
    Nichrome wire expands when it heats up. Without a tensioner the wire would become loose when you heat up the cutter. The spring in the upper attachment point keeps the wire straight.
  • Banana plugs
    The machine can be easily plugged into a benchtop power supply with some banana cables (test leads).
  • Easy to assemble
    I added pockets to all of the pieces, which help to align them when assembling the machine.
  • Looks kinda cool!

Step 2: Tools and Materials

This project was made with things I had lying around. If you need to purchase all of the components, it will probably cost around 20-30 dollars (excluding the power supply). I used a variable benchtop power supply, because this allows you to change the temperature of the wire.



Step 3: Cutting

With a CNC router
This project was designed to be cut out on a CNC router. I used CamBam to convert all the DXF files into tool paths for the machine. CamBam is a very easy to use program and works very well for simple 2D pieces. I have included all the DXF files down below.

Feeds and speeds:
- 1200 rpm
- 1500 mm/min
- 3 mm depth per pass

Downcut Spiral End mill
For this project I used a special carbide downcut spiral end mill. This end mill does not pull the chips up, but pushes them down. This type of end mill (see picture) works very well in plywood. I have found that normal end mills can leave a very rough edge, because they pull up the top layer of veneer. The downcut end mill leaves a very clean edge! The main advantage for me is that I don't have to use tabs to hold the pieces in place. Because the saw dust gets pushed in between the workpiece and the scrap piece the pieces are held in place firmly enough to cut all the way through. For plywood I always use carbide end mills. The glue in the plywood really dulls HSS end mills very fast. The one I used can be found here.

By hand
If you don't have a CNC router, you can definitely still make this project. You can print out the DXF files as templates and glue them onto the plywood. A bandsaw, jigsaw or even a scroll saw, should work well to cut out all the pieces. Note that all of the curves and the holes in the arm are purely aesthetic. You can leave all the pieces square if you want. The pockets in the table and base, are there for extra support and to align te pieces, but are not completely necessary.

Step 4: Drilling

I used the CNC to pre drill all the hole positions. On the drill press I drilled them to their final size. All the screw holes get countersunk and the base gets a larger hole on the bottom for the nut and washer of the eye bolt. The arm receives a 8 mm hole for the bronze bushings. I also drilled holes to install some female banana plugs. These will be used to provide power to the cutter.

Next I installed the table and transferred the hole locations to the support pieces. I then pre drilled these holes, so the wood won't split when you drive in the screws later.

Step 5: Sanding and Fitting

Now comes everyones favorite part of the whole project, sanding... It's easier to sand the pieces now, then when it's all assembled. I used a pad sander for the surfaces and rounded over the corners by hand.

The plywood I used ended up being a little bit thicker than I had planned. I should have measured this beforehand, because now the pockets where a little bit too small. I used a sharp box cutter and chisels to widen the slots slightly.

Step 6: Laser Engraving the Table

About a year ago, I received a Shapeoko CNC machine from Instructables. Because I already have a homemade CNC router, I decided to convert it into a small laser engraver.

I wanted to add some 1 cm markings to the table. This allows you to precisely set the fence a certain distance from the wire. While I was at it, I also put the Instructables robot on there, to make it more awesome :)!

As you can probably see in the picture, I originally messed up the numbering of the lines... I should have started at 0 instead of 1, so I had to sand them off and redo the numbers.

Step 7: Glueing

Now that all the pieces are finished, it's time to glue everything together. Make sure all the pieces are square when they are glued up. The table is only screwed down, this allows you to remove it to access the eye bolt.

Step 8: Finishing

I used some furniture oil to finish all of the pieces. I don't think it's really necessary for this machine, but it does make it look a little better and will protect it from greasy fingers.

Step 9: Installing the Nichrome Wire

Step 1: Connect the wire terminals to the wires and install the bottom eye bolt with two washers and two nuts.

Step 2: Put the nichrome wire through the eye bolt and twist it around itself to secure it.

Step 3: Install the table and thread the wire through the table and the washer.

Step 4: Temporarily clamp the arm to the base, it's position will be adjusted later.

Step 5: Install the bronze bushings

Step 6: Install the top eye bolt with the spring and wire attached (see picture).

Step 7: Push the top eye bolt all the way down and connect the wire in the same way as on the bottom eye bolt.

Step 8: Check if the wire is square to the table and adjust the arm position accordingly.

Step 9: Secure the arm in place with some screws. I also added an extra bolt through the base and the arm to make the connection even stronger.

Step 10: Installing the Fence

The two carriage bolts slide in the slots of the table, the square parts under the head prevent them from turning.

Step 11: Wiring

I installed two female banana plugs on the base to easily connect the cutter to a benchtop power supply with some test leads. The cables are connected to these plugs and secured with cable ties to the arm.

Step 12: Watts, Amps, Volts?

I used this nichrome wire calculator to select the correct voltage and amperage. The bench top power supply I used has an adjustable current limit. For me 3 volts and 2.2 Amps worked well. You want to cut styrofoam at around 200 degrees Celsius.

Note if you don't have an adjustable power supply, you can try to find a power supply with the correct wattage.

Step 13: Test Cut

In the pictures above, you can see a couple of test pieces I made. I used a template for the reindeer, which can be found here.

Step 14: Conclusion

As you can see in the previous step, the cutter works very well! I really like how it turned out and it will be a great tool to use in the future. The fence and laser engravings turned out to be very handy for preparing styrofoam blanks.

I hoped you enjoyed reading this Instructable and would love to hear your ideas and suggestions about this project in the comments. If you you have any questions feel free to ask!

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Wood Contest 2016

Runner Up in the
Wood Contest 2016

Maker Olympics Contest 2016

First Prize in the
Maker Olympics Contest 2016