DIY Variable Depth Hot Wire Foam Slot/ Hole Cutter

Hi all DIY enthusiast, this is my first Instructable.

I was into RC foamies in the recent months. I made DIY gravity feed cutter for cutting various wing profiles easily but I found its very difficult to use reinforcement. Generally I used plywood as stiffeners in my foam wings. I need to use my dremel tool to make the slot for fixing 4mm plywood. It was not smooth and finishing is not as expected.

So I made a variable depth hot wire foam cutting scoop tool for making slot/ hole or to cut foam boards at any angle.

Hope you all enjoy and use this DIY in your upcoming foam cutting techniques!

Step 1: Materials Required

Following materials and tools are required.

1. 5mm ply wood strip
2. Wire
3. 22 SWG Nichrome wire
4. 3.5 mm male and female connector
5. Lug
6. 4mm nut & bolt
7. Shrink tube
8. 5 min cure epoxy
9. Quick fix
10. Soldering kit
11. Screw drivers
12. Drilling machine
13. 4mm Drill bit
14. Dremel Tools set
15. Scroll saw (else axe saw)
16. Nose pliers
17. Scale

Step 2: Preparing Wood Strips

Cut the wood strips for below dimension. (you can vary the dimension as per your need)

There are four strips

1. Main support strip - 70mm
2. Spacer strip - 45mm
3. Sliding strip - 55mm
4. Bottom support strip - 30mm

Use 4mm drill bit to drill as per the shown in the 2nd picture and make a slot in the sliding strip as shown 3rd picture.

Pitch to pitch distance for main & spacer strip is 25mm and 8mm for sliding strip

Use your dremel router bit to remove excess wood to fix the nut as shown in the 4th picture.

Step 3: Applying Epoxy to Wood Strips

Ensure all the nuts are placed at 2.5 mm depth and apply 5 min cure epoxy.

Note:

1. Nut to be fixed inside between main support strip and sliding strip using 5min cure epoxy.
2. Ensure there is no epoxy applied on to the sides only.

Step 4:

Solder the wire with lug and 3.5 mm male connector and fix it with shrink tube.

Fix the soldered wire to the sliding strip using quick fix.

Fix the bottom support strip to main strip using quick fix.

Step 5: Now Assemble It!

Now fix the nichrome wire profile into sliding stip, and fix the sliding strip on the main support strip.

Paste a graph sheet for easy measurement on the side.

Your HOT WIRE SCOOP TOOL is ready!!!!!!

Step 6: Nichrome Wire Profile

Use 22 SWG nichrome wire. Its more optimum to use this wire since its rigid and gives clean cut without much deviation. You can simple bent the wire using nose plier.

Profile:

1. Rectangular
2. Circular
3. Square
4. Half circle
5. and more

Step 7: Using Foam Scoop Cutter

Comments

[eisnic]

Hi samayaraj. I'd like to try making foam cutters capable of doing the depth cuts like your demonstrated here, plus doing a bit of shaping and sculpting. Looks like you've got the right tool for the job here. I've looked up the Turnigy Reaktor you used here and it's variants, so I at least know I can get one from an online mail order house.

The input for it is a computer power supply, is that correct? (The modified ATX power supply you mentioned in answer to bwh13.) So I should be able to find one like it in a computer component supply shop. Can you outline the modifications you made to it so you could connect it with the Turnigy device?

I'm in Canada where the domestic power supply is 120 VAC @ 60 Hz, so I was wondering if I could even use the Turnigy. I couldn't tell whether it was only designed for British & European use where the power supply is 230 +/- 10VAC @ 50Hz. Thanks.

[samayaraj]

Hi eisnic,

Yes, its the SMPS/ATX which is powering our desktop computers. I have modified my old PC's power supply for Turnigy Reactor.

1. If you want to use Turnigy reactor only for foam cutting, I think 12V, 2A power supply is enough. Simply buy a 12V, 2A power supply adapter and push it in 5mm socket.

2. If you want to use Turnigy reactor unit for battery charging/ balancing/ motor drive/ foam cutting etc., then you need around 250W (max) of input power. So instead of spending more money in buying a power supply adapter, I modified ATX power supply. My ATX will power 12V 14A (162W).

3. If you want to modify ATX power supply, there are many instructables in this site. Just flick through this website.

4. If you need dedicated power supply, Hobbyking's 350W unit you can buy. https://hobbyking.com/en_us/hobbyking-350w-25a-pow...

Alternatively, you can find chargers with inbuilt power supply if you feel uncomfortable with making/ buying separate power supply unit.

5. If you want to make if further simple, try using various resistance nichrome wire with 5V power supply directly from adapter to find ideal one for cutting.

If you have further query, please ask me.

[eisnic]

Oh, and a follow-up question: Did you consistently use 22 gauge NiChrome for your cutter wire? I was just thinking that a slightly thicker gauge might be stiffer and so handier for sculpting, though of course it would require more current to reach cutting temperatures. How long were you able to operate the cutter before the supply wire into the hand tool heated up and became a problem? Or was it not a problem at all? Thanks again.

[samayaraj]

Hi eisnic!

Sorry for the delayed reply. I feel, 22 gauge wire is sufficient. You can use lower gauge if you want to make cutting profile sizes bigger than 10mm. There wont be much heating in the handling part as the nichrome wire is under the handling area. If you use this cutter prolonged, the hot wire surface in contact with wood becomes charred. That has to be rectified. Else, you can paste a piece of fiberglass/carbon fiber/kevlar with epoxy on behind nichrome wire where it touches the wood surface to avoid charring.

[shadnlyd]

Nicely done! Thank you, samayaraj!

[samayaraj]

:)

[Swansong]

Thanks for sharing :)

[samayaraj]

:)

[bwh13]

Great work Citizen!
Would love to know more about your power supply

[samayaraj]

Thanks!

I used turnigy reactor 250W 10A battery charger. There is an option for foam cutting. I kept 5V & 3A and power used would be around 11W.

It was power by modified ATX power supply.