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Author: Subject: DIY Foam Cutting Tool Using Nichrome Wire
BetaTest
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[*] posted on 9-1-2012 at 22:41
DIY Foam Cutting Tool Using Nichrome Wire


Hi All!

I'm trying to cleanly cut and shape some Styrofoam chunks i have sitting around. If I use a knife or saw it shreds and I get little pieces of Styrofoam falling off the cut face. So in order to get a clean sharp cut I'm going to use a heated wire.

After searching around online I developed a theory that I could build a DIY version of this using a Nichrome wire and a 9 volt battery. Basically the resistance of the wire would cause it to heat up enough to melt/cut through the Styrofoam block!

Does anyone here have any experience with cutting foam? or with Nichrome wiring? I've never build anything like this before, will it work?

My main questions are, what gauge of wire should I use, and will the 9 volt battery be enough to heat up the wire. (or said differently, what gauge wire will a 9 volt battery work on?) I can use a think wire, but it can't be too thin i think.

Thanks for reading and I look forward to you advice / comments!

[Edited on 10-1-2012 by BetaTest]
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Aqua_Fortis_100%
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[*] posted on 9-1-2012 at 23:18


I doubt there will be going a decent current from battery to Ni-Cr wire.. Any if so, it wont last...

Couple of days ago I took a resistance from a broken shower and wound around a ceramic tube to make a little quick-drying tube. I measured the resistance with multimeter and gaves about 5 ohms..

Ive used an old used PC power supply to power it.. There is no need to buy batteries.. When 12V wires are used, from ohms law and power law it turns that current should be about 2,4A (2,7A was measured) and power 28,8 W (about 30 W).. That power is the same of a mild-moderate soldering iron.. So surely will cut styrofoam.. Other power sources could give even more power, but for styrofoam is not necessary..







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Pulverulescent
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[*] posted on 10-1-2012 at 02:19


You need a mains transformer with a low-voltage output current high enough to just melt the foam, giving a clean cut ─ too high current will give a wider, erratic crude cutting action!
And any straight, thin steel wire will suffice!

P
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dann2
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[*] posted on 10-1-2012 at 05:18



You can also use a 12V (or a 6V) battery charger.
A car battery will do to. (careful of burns etc if wire is too low a resistance).
A computer power supply will do if you put a resistor in series.
It will depend on the length of your resistance wire (or simple steel wire if you are stuck) and how hot you need it.
If you are getting too much current going through the wire (getting too hot) then put a resisistor (made from more of the resistance wire) in series with the supply (battery charger or whatever).

What you idealy want is a controlled current supply. You can purchase them on ebay.
A simply lab power supply with 'controled current' out facility is great.

You can get suitible wire from old electric resistance heaters (electric fires). You can also buy a replacement element for same and use some of the wire. (10 dollars or so)

Dann2

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watson.fawkes
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[*] posted on 10-1-2012 at 05:46


Quote: Originally posted by Pulverulescent  
You need a mains transformer with a low-voltage output current high enough to just melt the foam, giving a clean cut ─ too high current will give a wider, erratic crude cutting action!
I have a hot-wire rig I made by re-"winding" the secondary of an old microwave oven transformer. I put "winding" in quote marks because the secondary is five loops of 10 gauge stranded copper. That works well for the particular length of nichrome I have attached to it. I've been meaning to make it more useful by making a plugboard and putting on multiple secondaries. Four secondaries of one, two, four, and eight turns would give a good range of voltages which easy reconfiguration at the cost of some connectors.
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fledarmus
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[*] posted on 10-1-2012 at 06:00


Something like this?

Hot wire foam cutter

I used one for years making terrain for tabletop miniatures games that used 3 "D" cells.

I don't know why a 9 volt wouldn't work, but I don't know what the energy density of a 9 volt is. You may be going through batteries too fast.

Replacement wires and bows are available for many of the hot-wire cutting systems available if you want to experiment with different power options.
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overload
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[*] posted on 10-1-2012 at 06:12


The only problem with putting a hot wire to styrofoam is fumes are generated. Not healthy.
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Pulverulescent
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[*] posted on 10-1-2012 at 06:22


If any fumes are emitted, the wire's too hot!
Melting the foam cleanly without vaporisation is what's required . . .

P
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[*] posted on 10-1-2012 at 09:43


I've recently been dabbling with nichrome wire and simple circuits. I built a little mini-test-tube-heater-wannna-be glas-col hehehe. In one of my tests before I weaved the wire into fiber-glass cloth I was moving the nichrome through a candle with ease(granted the wax would cool and not make a cut)

If you don't have a power supply, I would take an old cellphone charger hack off the charging attachment(hopefully it as sufficient current for your needs), an SPST switch(on/off for one 'pole'), and a potentiometer. Play with the current on the potentiometer to find what satisfies your desired heating consistency per given length of nichrome. Then find a way to mount the project.




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dann2
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[*] posted on 10-1-2012 at 13:13



A variable voltage transformer (a variac) before the low voltage transformer would be very useful for trying different powers. They may be a bit too expensive for the project.

Lots of different taps on the homemade secondary on the microwave transformer would do the same job I guess.

Dann2
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[*] posted on 10-1-2012 at 13:24


Quote:
They may be a bit too expensive for the project.

And you may not be kidding, dann2 . . . (:D)

P
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zoombafu
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[*] posted on 10-1-2012 at 14:50


I have a cutting tool for styrofoam that works on this principal, so I dont see why your plan wouldnt work




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Endimion17
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[*] posted on 10-1-2012 at 18:02


Quote: Originally posted by overload  
The only problem with putting a hot wire to styrofoam is fumes are generated. Not healthy.


That would be a thing to consider if he wanted styrofoam cutting to become his daily job. Cutting up few pieces, even if any fumes are emitted during the proper heating, won't harm anyone.




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[*] posted on 10-1-2012 at 20:15


Wow guys, first let me say thanks for all the great responses!

Aqua I really like your idea about using an old computer power supply. Is it possible to start one without a motherboard attached?

Fledarmus - thats what i'm going for, but I need something bigger.

smaerd - I like your idea about using the phone charger, Is there any specific type I should look for?


I actually got another idea after reading all of your posts. What if I just got a simple metal wire, and curved it to the shape I need and heated on a stove. then used that to make a couple of cuts. Would that be clean enough? Also what gauge of wire is needed for a wire to hold a bend or shape?

Thanks again!!
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[*] posted on 10-1-2012 at 20:54




Heating on the stove might work if it's a really small project, and a thicker, less thermally conductive wire. Else it will probably cool down and stick during the cut.

[Edited on 12-1-2012 by Bot0nist]




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[*] posted on 11-1-2012 at 11:06


Quote: Originally posted by BetaTest  
Is it possible to start one without a motherboard attached?


Hook up the green wire with any black wire.

http://www.youtube.com/watch?v=4askospjx0E&feature=relat...

[Edited on 11-1-2012 by Aqua_Fortis_100%]




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[*] posted on 11-1-2012 at 11:22


beta test I was using 36 gauge nichrome with a length of about an inch, a 5v and 500mA cell phone cord, and it was melting through a candle red hot with no problems. It all depends on the gauge of nichrome, how long you need the wire to be, and how hot you need it to get.



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[*] posted on 11-1-2012 at 12:08


I can second the cellphone charger method- The voltage it provides is consistant right as the coil warms (which increases resistance and lowers heat, finding a balance on it's own).

I personally have set up a 12" Nichrome wire planer for making foam sheets- I use a 9V 250mA supply which works quite well.

You can also cut smoother with less heat and slower movement. I know through experience,faster cutting makes lousy cuts- Wavyness, warping, and stop-and-go marks.
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[*] posted on 11-1-2012 at 22:43


Hi Guys,

Thanks again for taking the time to help me out!!

Aqua - thanks for the video I'm pretty sure i can jump start a PSU now! Can you please describe the best way to connect the resistance wire to the 12V rail on the PSU?

smaerd - i'm pretty new to this type of stuff, do you have any pictures or diagrams of your setup? What goes where and what connects to what. That would be awesome!

Wizzard - I need the wire to be about 12" long in a semi circular shape. So the wire has to be able to hold some kind of shape.

Where did you guys get your nichrome? osh, lows and home depot don't have it in my area. eBay has a few vendors selling it. Any place i didn't think of?
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[*] posted on 12-1-2012 at 04:55


Quote: Originally posted by BetaTest  
Where did you guys get your nichrome? osh, lows and home depot don't have it in my area. eBay has a few vendors selling it. Any place i didn't think of?
I have purchased nichrome resistance wire locally from an independent appliance repair business, who stocked it for repairing toasters.

As for mail order, I have found that eBay sellers are all rather expensive compared to buying from a specialty seller. I've used Duralite with satisfaction in the past.
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[*] posted on 28-1-2012 at 22:31


Hi Guys and thanks for the responses.

I've managed to find some 24 gauge nichrome wire and a couple of old cell phone chargers.

One is 4.5V DC 600mA out the other is 5.9V 375mA out. Which one is better for this experiment.

Once I pick the charger, what do I do? Do I cut of the end and solder it to the ends of the nichrome wire? What should I use to tension the wire? Does anyone have a pic of their setup?

Thanks for reading!
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