Foam Hot Wire Table

Here's a simple DIY, 90% printable foam hot wire cutting table for hobbists who want to make stuff out of foam. This low-power tool is simple to make, and allows you to cut foam of various thickness. Of course, the thicker the foam, the slower the cutting, but the tool will be useful to many hobbists.

The whole thing is powered by a simple DC 5V and 2A power supply.

I call it “Foam cutting table for dummies”, since I'm not an expert when it comes to electricity :).

You can print everything with PLA except the Upper Wire Holder - this one should be printed with PET-G.

Warning

As you're working with electricity and hot temperatures, be very careful. If you're underage, seek adult supervision!

You will need:

• 2x V-Slot 2020 24cm long for the sides
• 1x V-Slot 2020 20cm long for the fence
• Hot wire (resistance wire) - 0.3 mm
• Power supply: 5V and 2 Amps with jack pin
• Power Switch - 3 pins rocker switch 30x13mm
• DC socket 5.5x2.5mm for jack power supply
• 2 electrical connectors
• T-Nuts M4
• T-Nuts M5
• M3x8 - 1x
• M3x10 - 8x
• M3x12 - 4x
• M3x16 - 3x
• M3x30 - 2x
• M3x40 - 2x
• M3 Nuts
• M4x6 - 8x
• M4x20 - 1x
• M4x50 - 1x
• M4 Nuts
• Small spring - 15 to 20mm in hight, for the tensioner
• 22x2mm round washer to act as a heat sink
• Wire/cable to connect everything
• Plastic ties to hold the cable
• Soldering gear

Known Issues:

Printing the flat bed proved to be the biggest issue for me, due to the warping of the corners. Use any methods you can think of to prevent such warping - use a brim, mouse ears, skirt, enclosure, or glue stick to increase the addhesion on the corners of the print.

Since the printed parts can get hot and melt, I recommend using this tool for short cutting sessions and letting the parts cool down. You can also print the wire holder pieces from PET-G that is more heat resistant. More updates to this design are coming so that this issue can be solved with future releases.

Update 10.11.2024

I added a new upper wire holder, that holds the wire on a spring and connects it with an alligator clip. This should deal with the melting problem of the upper holder.

How to Build

After printing all the parts:

Use M4x6 and M4 T-Nuts to connect the bed to the two side V-Slots 2020. Put the power supply socket in the proper slot of the bed, and fix it in place with the Power Supply Holder piece. To do so, use two M3x12 screws.

You can also push the four legs into the V-Slots. To print the legs, I recommend TPU.

Use another two M3x12 screws to fix in the place the power button. The 30x13 rocker switch should fit the printed frame nicely.

There should be three digits on the power switch: 1, 2 and 3. Connect one cable to the 1st pin, and the other cable to the 2nd pin - it doesn't matter which is which, because the circuit will be closed as long as you use the 1st and 2nd pin on the switch. The 3rd pin is used for the light inside the switch.

I've placed a flat washer in the center slot of the bed. This will act as a heat sink. 

Now, screw the Arm Holder to the bed using at least 4 M3x10 screws. Then, slide the Arm into the slot you just created in the bed. 

The bottom wire holder is a simple thing. I used an M4x50 screw with a flat head, but you can use a different yet still long M4 screw. I've connected the wire to one end, then used a washer and an M4 nut on both sides of both printed extrusions. The washers and nuts are screw tight so they hold the screw in place. The hot wire is wounded around the center of the M4x50 screw.

While one of the cables goes from the power supply socket to the power switch, the other cable goes from the power supply socket onto the arm, and then right up to the upper wire holder. Everything is held in place with plastic ties I got with my Prusa kit :).

On 10.11.2024, I've uploaded a new upper wire holder. Look for “Wire Holder V3.stl” and print this one. Mount it just like the original one. But this time, the upper wire is connected with an alligator clip holding the wire just below the mounting spring, and the spring is mounted to the top screw (I used M3x30). The holder is mounted using M3x30 as well.

Use this version of the wire holder if you experience any melting problems with the first version of the holder.

Alternatively, you can build the first version of the upper wire holder:

The cable is connected to the upper wire holder. Let's have a look at this holder from the opposite side:

Now for the upper wire holder and the tensioner mechanism.

Use an M3x16 and an M3 nut to connect Spring Holder piece to the Arm.

Then, take Upper Wire Holder piece. Put M3x8 inside the single threaded hole, and secure this screw with an M3 nut on the bottom side. These two M3s will hold the spring between the two printed pieces.

Take two M3x40 screws and put both through the wider holes in the Upper Wire Holder piece. Screw the two screws into the Spring Holder piece. The Upper Wire Holder should „slide” on these two screws, this is why they’re wider than the M3 screws. Place a small spring between the two pieces like on the photo. It’s not secured in any way right now. It will be secured in place once you place the wire holding vertical screw with proper tension on the hot wire. 

For the upper vertical wire screw, I used M4x20 screw, and I did the same thing I did to the bottom screw. I connected the screw to the power cable, and used nuts to hold the piece in place. The nuts are used to make sure the screw won't slide left or right and will remain in place. The tension on the hot wire is what really holds it in place.

The idea is to attach hot wire to the bottom screw, then wound it around the upper screw while it's not yet placed in the upper “cradle”. When the wire is attached, press the upper wire holder down, compressing the spring, and place the wire in the cradle, then release the part. The arm and the spring should provide enough tension to streighten the hot wire. Now the electric circuit is closed.

Fence

Here's the first version of the fence:

Take the 2020 V-Slot, the one that is 20mm long. First, use an M3x10 and M3 nuts to connect Fence Holders with Fence Mounts. There are two pieces for each side. On the photos, I used longer M3s, but M3x10 should be enough. 

Now use two M5 screws and M5 T-nuts to connect the two Fence Holder pieces to the V-slot profile. I used M5x8 screws with two washers, because I didn't have any shorter M5 screws at the time. If you do have shorter M5s, you don't need the washers :).

Place a square M4 nut inside the slot, and then drive an M3x16 screw with hexagonal end through the nut. Add a screw holder to the screw's and, and add a rounded Fence Holding Ball. Repeat this step on the other side. You'll be able to use these two screws to hold the fence in place.

You can also use the second version, heavily inspired by the one made by KendinYab (https://www.printables.com/model/736387-very-useful-mini-table-saw-v20). While I redesigned the mount, the nut is the same file Kendin made.

The Wiring

The wiring is very simple:

Connect positive slot of the power supply socket to the 2nd pin on the power button. Then, connect 1st pin of the power button with the screw marked as „Cable Connection”. Wound the hot wire around the screw, marked as „Hot Wire Connection Point”.

Then, wound the hot wire around the upper wire screw. Connect that wire screw, using a cable, to the negative slot on the power supply socket. This completes the electric circuit and allows for the power to flow.