Homemade hot wire cutter for foam/styrofoam

[TheRunningMan]

I'm wanting to make a hot wire cutter to use with foam/styrofoam for model making etc. Does anyone here have knowledge of making one of these.

I was thinking after doing some research of using a mobile phone charger (or similar) that provided a 12v 2-3amp DC output and connecting the 'hot wire' to that to provide the basic function. Would I also be able to regulate to amps to the wire and intern lower/higher the heat output if needed and what about light to signify that the device was switched on.

I would idealy like to create something similar to this

View media item 56786
Any advice/opinions would be gratefully received

I know it's not technically household electrics but as it will be run from a mains socket I thought it would be best to post it here

Cheers folks

 

[Adam_151]

A phone charger is not going to have enough power.

For an easy soluation you could try a soldering gun with the tip removed as the source.

Seen a microwave transformer with a re-wound secondary used for this sort of thing before, but that was probably quite overkill as it could managae to melt 3x30A fuse wire twisted together

Deli counters after use a machine to cut cling film wrap which consists of about 400-500mm of nichrome wire driven from a 12V 2A transformer. Last one I had to repair I ended up ordering a suitable tx from RS

 

[ricicle]

For a starter you need nickel/chromium wire and a low voltage DC source...

 

[TheRunningMan]

Deli counters after use a machine to cut cling film wrap which consists of about 400-500mm of nichrome wire driven from a 12V 2A transformer. Last one I had to repair I ended up ordering a suitable tx from RS

Continuing my research I found that 26 gauge nichrome wire is a good choice at 0.4mm thick. I could use a 12v 3amp power supply sourced from eBay. Would it be possible to alter the amps via some sort of resistor?

 

[Taylortwocities]

Would it be possible to alter the amps via some sort of resistor?

Yes of course, that's what Ohm's Law is about.

 

[ban-all-sheds]

For a starter you need nickel/chromium wire and a low voltage DC source...

Very dangerous.

Extra-low voltage should be used.

 

[TheRunningMan]

Would it be possible to alter the amps via some sort of resistor?

Yes of course, that's what Ohm's Law is about.

Thanks. What would you suggest I use to achieve this?

For a starter you need nickel/chromium wire and a low voltage DC source...

Very dangerous.

Extra-low voltage should be used.

What would you use instead?

 

[bernardgreen]

I have made a 1.5 metre long hot wire for bending plastic sheet but the same principles apply to a foam cutter.

When heated nichrome wire expands a lot so there has to be a tensioning system to take up that expansion. To cut foam with a straight cut the wire has to be tensioned otherwise it bends as it moves through the foam.

Bear in mind the tension system will be heated by the wire.


Being able to control the current is essential. The ambient temperature will affect the temperature of the wire so the current has the adjustable to have the wire at the right temperature.

Using resistors to control the current is going to create a lot of heat in the resistors

My current control is a mains variac transformer ( 0 to 260 volts ) feeding a 230 to 24 volt 10 amp transformer. Adjusting the variac alters the "24 volt" from 0 to 26 volts.

Variacs are NOT isolation transformers and even if the output is turned down to be only a few volts it is still directly connected the mains. so treat the ouput as if it is 230 volts

Give some thought to removing fumes from the cutter, some foam produces toxic fumes when heated to melting point.

Some foam will melt, let the wire through, and then weld back across the cut behind the wire. These foams have to be burnt or vapourised by the wire. Fume extraction is then essential. Vacuum cleaner outside in the garden with a long hose in to the work station is a good temporary solution.

 

[ricicle]

For a starter you need nickel/chromium wire and a low voltage DC source...

Very dangerous.

Extra-low voltage should be used.

Thanks - that will teach me for posting when I come back from a night out!

 

[Monkeh]

Perhaps you should pick up the December 2012 issue of EPE: http://www.epemag.wimborne.co.uk/acatalog/2012.html

It should cover everything you need to make a hot-wire cutter.

 

[TheRunningMan]

When heated nichrome wire expands a lot so there has to be a tensioning system to take up that expansion. To cut foam with a straight cut the wire has to be tensioned otherwise it bends as it moves through the foam.

I was going to combat this by attaching the wire to a spring and letting the spring expand. Then when the wire expands the spring will shrink and keep the tension on the wire.

I've looked at those variac transforms and they look like a good piece of kit. Is there a cheaper alternative though as I think having 10amps will be overkill for what I want to do. I was hoping to make it as cheap as chips but maybe that won't be possible.

 

[TheRunningMan]

Perhaps you should pick up the December 2012 issue of EPE: http://www.epemag.wimborne.co.uk/acatalog/2012.html

It should cover everything you need to make a hot-wire cutter.

Thanks. Ill have a look at this

 

[mfarrow]

You're best varying the output current of a regulator rather than using resistors.

There are plenty of cheap, readily available 12V regulators around. Look at the link below and there's even some application circuits drawn in the back.

http://www.st.com/internet/com/TECHNICAL_RESOURCES/TECHNICAL_LITERATURE/DATASHEET/CD00000449.pdf

 

[Monkeh]

You're best varying the output current of a regulator rather than using resistors.

There are plenty of cheap, readily available 12V regulators around. Look at the link below and there's even some application circuits drawn in the back.

http://www.st.com/internet/com/TECH...L_LITERATURE/DATASHEET/CD00000449.pdf[/QUOTE]

Ugly, hot way to do it, and very limited current.

 

[TheRunningMan]

You're best varying the output current of a regulator rather than using resistors.

There are plenty of cheap, readily available 12V regulators around. Look at the link below and there's even some application circuits drawn in the back.

http://www.st.com/internet/com/TECH...L_LITERATURE/DATASHEET/CD00000449.pdf[/QUOTE]

Thanks. Ill have a flick through when I get home but so far it all seems German to me lol