Hot Wire Polystyrene Cutter

[OnOff]

Anyone made one?

Looking to knock one up for cuttiing 1" thick polystyrene sheets to line a storage shed. Yes, I could use a saw / knife but it's messy and where's the fun in that?

Anyway, I've gotten some high resistance 0.30mm dia Kanthal wire from a mate who's into "vaping" apparently. (Not 100% sure if that's a legit pastime or not!) This is the ONLY wire I have so want to use it.

Resistance for the stuff is 20.11 Ohms/m. Thinking I can take a few strands of the stuff and twist together to make a "thicker" cutting wire. Using the wire in single strand form is firstly fragile and with too thin a wire the sheet will stick back together as it passes the wire. Most sites suggest using a variable power supply but I've a whole bunch of various fixed voltage, plugtop PSU's from various kit binned over the years.

Figuring I can maybe select a PSU from the collection and then make the cutting wire to the appropriate resistance (RT) from a bunch of the thin wires in parallel? For instance, 6 wires, 150mm long in parallel would give me an RT of 0.5 Ohms etc (as in 20.11x0.15=3.0165 Ohms, then 1/RT = 1/3.0165 x 6).

Try it I suppose.............and test it OUTSIDE!  :lol:

 

[kerching]

Or.....get wife to test it

That way, if it goes pants you will be able bodied enough to have another go

 

[apprentice87]

Ii would expect it to work!! Will you have to incorporate some sort of spring loaded tensioner to keep the wire taut?? Just thought it may go a bit saggy when hot. I used one of these in school when i was about 13, but have to admit i cannot remember what i did with it or even what it looked like!!

john..

 

[Blue Duck]

Photon can help

https://www.youtube.com/embed/b1mXQ8f4zgs?feature=oembed

 

[OnOff]

Good point on the tensioner John and you have to love Photon too! Scoobed both.

So down the "that'll come in useful one day" box of adapters and have found  12VDC, 500mA adapter from the well known Chang Zhou Tai Yu Electrical Equipment Co. Ltd...........UK made then! 

 

[ProDave]

I made one as a boy.

Simple really.  I just used a bit of wire from one of those old electric bar heater elements. You know the old things about a foot long with a coil of wire wound around the outside of a ceramic former.

They were rated at 1KW, so with about 4 amps flowing through them they would glow red.

So just a short length of that wire, connected to a variable voltage dc power supply capable of supplying up to 4A and bob's your uncle.

It didn't need to be particularly hot to cut polystyrene, not even glowing red hot, so only a couple of amps needed.

 

[Richard-the-Ninth]

I believe you want  nichrome wire. You can get it from ebay

 

[OnOff]

Thinking about it I'm sure I've a power supply I built years back based round a L200 that I built for a printer (base kit from Maplin I think......too long ago / memory's going). Think it's set at 24VDC and 2A. Has presents for the voltage and current - could bring them out to pots. Dig through the shed tomorrow!

 

[Phoenix]

I've seen similar made from a microwave transformer with a re-wound secondary... about 3 turns of 16mm on the secondary... I Don't know what the cutting wire was probably quite a bit thicker than the vaping wire I suspect, As the thing could cut easily melt three strands of 30A fusewire twisted together!.

 

[OnOff]

All I found in one of the sheds was the build instructions for the L200 PSU (it was from Maplin)...........the actual unit must be in one of the lofts.............thinking I built it for an old Thinkjet printer........maybe it needed nine point something volts or was it nineteen point something............

BUT.......I did find a few old trannies. Various inc a bunch of torroidal ones offering 12VAC at 250W which look serviceable. Will try and slope off from tree house building duties tomorrow and have a bash!

 

[OnOff]

Well..........made a start with some offcuts:

 

[OnOff]

Well.......from the "it's not rocket science" school of experimentation:

12VDC 500mA plug top adapter. 150mm of 0.35mm Kanthal wire, it works:

 



The rule of thumb on the radio control model forums seems to be 50W/m, think this was 0.5mm dia Katnthal. This was AFTER I'd made the frame and I've only got 0.35mm dia. So.....figured beforehand the 6W I had to play with might be a tad light for a 150mm long "element" .........s@d it try it anyway! :lol:

It works if a tad slow to cut. At the mo I just want this to cut large sheets of 1" polystyrene (to line a shed). I don't want to be there all day so I'll just change the top connection to a crocodile clip and have my own rheostat - can vary the element length that way.

And YES, it does go instantly floppy when you apply power so a little tensioning cam / screw is in order.

If I could only find my variable psu!

p.s Cost £0.00!

 

[Sharpend]

I still say a sharp knife is quicker!

 

[Blue Duck]

Not as fun and less messy!

Knowing Onoff that frame is probably just the right size for what he is cutting

 

[OnOff]

Tried those craft knives with the long, break off blades they seem to "stick" and even an old bread knife with serrations. Drives me nuts hoovering up all the little polystyrene "baubles" that escape............just got to make a cutting fence now...........

 

[Apache]

You'll be as high as a kite!

 

[OnOff]

You'll be as high as a kite!

Now there's a thought...........a polystyrene kite! Has it been done?

 

[Sharpend]

Circular or jigsaw?

 

[Andy™]

And YES, it does go instantly floppy when you apply power so a little tensioning cam / screw is in order.

use something a bit stronger. like a hacksaw blade. with induction coils net to it to get it glowingly hot

 

[OnOff]

Here we go! It's kept me out of the house and I even managed to sneak out to Machine Mart (plumbing related).

Subject to the longevity of the element this set up works a treat: 12V, 830mA adapter so a few more watts than previous. Also added a tension spring. Did try a croc clip with the previous set up but figured maybe not as I may want to cut thicker polystyrene in the future. Going to make some spare "elements". Found easiest way was to tie a bowline knot in the ends of the lengths of the 0.35mm dia Kanthal wire. Got to make the fence able to lock on, bit of paint etc: 





Then line the shed (& move in). Will probably never use it again.

:lol: