DIY Plunge Foam heat wire cutting

[Boyan Silyavski]

At the moment i am looking to buy and try this one https://hotwirefoamfactory.com/CNC-Hot-Knife.html


I was also thinking about sth like the mini induction heaters sold around in ebay for 10$ combined with 0.4mm disposable stainless steel rod or the 0.5mm TIG electrodes i found in aliexpress.

I dont know anything about that induction heaters, maybe i will have to cool the coil or sth.

[cropwell]

I had a quick look on Aliexpress and they have hot knives for $15 - $22, they seem to be 2mm dia and various lengths, up to 100mm. (for cutting styrofoam)

My experience of goods from China is that they are slow to arrive, Aliexpress is slower than eBay. American goods are always saddled with customs charges and handling fees, which generally pisses me off, especially when you can't always find out the total cost in advance.

[magicniner]

Forget rods, you will not get adequate conduction.
Small stainless steel tube = medical needle.
The steel is perfect for generating heat with a controlled current, enamelled (not lacquered-that's no good) copper wire through the middle and brazed at the bottom gives you a circuit with the greatest heat generation from the steel.
The fan is to keep the connections, mounting block etc. at the top cool.
Any good? :-)

- Nick

[Boyan Silyavski]

Forget rods, you will not get adequate conduction.
Small stainless steel tube = medical needle.
The steel is perfect for generating heat with a controlled current, enamelled (not lacquered-that's no good) copper wire through the middle and brazed at the bottom gives you a circuit with the greatest heat generation from the steel.
The fan is to keep the connections, mounting block etc. at the top cool.
Any good? :-)

- Nick

I was leaning that way. last night found some wires . The mechanical part as you say is buy the wire and make the tool. have absolutely no clue which of these wires will be any good, i assume any? As anyway i will be connecting this to a lab PSU so i will turn the knobs until it heats adequately

I found 1mm diameter Hot Wire Foam Factory knife , but it becomes very expensive with shipping and tax and duty. I believe it will do the job way better than the Chinese foam knifes which all are 2mm thick.


I think my next build will be foam cutter. They seem way under rated but from what i see for now, foam letters here is what people want most of all. As they are cheapest of all. But money are made.

[Boyan Silyavski]

Forget rods, you will not get adequate conduction.
Small stainless steel tube = medical needle.
The steel is perfect for generating heat with a controlled current, enamelled (not lacquered-that's no good) copper wire through the middle and brazed at the bottom gives you a circuit with the greatest heat generation from the steel.
The fan is to keep the connections, mounting block etc. at the top cool.
Any good? :-)

- Nick

I believe you gave me the best idea till now. Just bought the needles from China.

Inter Diameter(ID):0.232mm

Outer Diameter(OD):0.5mm

Tip Length:100mm,3.9"(needle length,not contain the base)



I consulted with the guys from wire.co.uk and they said oxidized constantan wire will do the job and resist 400C, the temperature i need / 200-300C/. Was going to buy from them but quick check on ebay i found some military surplus from the cold war.

So now soon i will have the needles and the wire. I hope there will be no problem inserting 0.16mm wire in 0.232mm needle. Whats left is the silver solder. I have some silver wire but i was going to figure the exact flux needed for that wire.



The challenge as i see it is to terminate mechanically properly the whole contraption . may be solder the thick wire to needle body and other thick wire to the thin wire. Then fit this in needle with some teflon separator and pot it. solder then the tip side. cut off the extra wire and thats it. If i am lucky.

[magicniner]

Boyan,
Silver Solder a collar near to the top of the needle, use a fitting like a hollow brake pipe nut to clamp the collar into the mounting block whilst allowing the top of the needle and wire to show above the nut.
Silver solder a small block to the top of the wire, power can then be connected quickly and the tips can be swapped out quickly and easily,
Regards,
Nick

It's not an idea, more of a design description, with the right implementation it will definitely work ;-)

[Boyan Silyavski]

Meanwhile here is a LOW FI/ i broke my edge 7/ video of my new contraption, while i am waiting for the needles and stuff. it could cut 1200x600mm foam sheets. ceramic contact block, isolated by silicone pad, 0.5?? mm mig wire , 2 old pc fans and 25x25mm steel profile . 700mm deep. Could cut 200mm thick foam
300 mm/ min cut , radiation cutting, no pushing the wire