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Old Feb 28, 2012, 05:00 PM
Registered User
United States, OH, Cincinnati
Joined Mar 2008
268 Posts
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Foam cutting

I need to cut foam wing cores for the F-100 I am buildi9ng, (and other things in the future, I got the scratch build bug now!)

I ordered some nichrome wire, and am going to build a bow, however, I am not sure what to power it with.. some have said a 12v battery charger, however, this does not allow adjustable current (for varying lengths of wire/heat needs)

Any recommendations are appreciated!

Matt
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Old Feb 28, 2012, 08:02 PM
Registered User
Brasil, GO, Goiânia
Joined Feb 2009
363 Posts
Hi Oryon,

I use an old PC power supply +12v, and a 700mm fixed wire lenght, cuts very well.

Humberto
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Old Feb 28, 2012, 08:30 PM
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United States, OH, Cincinnati
Joined Mar 2008
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70cm is a bit short... Im cutting 30+ inch (per half) wings on this project....thats why I wanted a variable suppky, so I can make 2 or 3 bows of various sizes...

Sent from my SGH-T849 using Tapatalk
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Old Feb 28, 2012, 08:35 PM
turbonut's Avatar
upland CA
Joined Dec 2004
7,003 Posts
aircraft spruce has a kit that is variable for about 40 dollars
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Old Feb 28, 2012, 11:58 PM
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United States, MN, Hermantown
Joined Dec 2008
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I just build one recently. I went with a 4amp transformer. http://www.jameco.com/webapp/wcs/sto...0001_221365_-1 I see it has went up a few bucks since I bought mine. Basicly all you need it the trans, a fuse, and a dimmer switch. With this amount of power, it was said to be able to cut cores up to about 36". I think it cost just a little over $40.00. Works well.
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Old Feb 29, 2012, 01:19 PM
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Columbus Ohio.
Joined Aug 2006
151 Posts
If you've got enough moola...this is what you need.
A Mastech HY3005D Single Ouptup Linear DC Power Supply 0-30V @ 0-5A.
On EBay for $115.00 free shipping.
Digital readouts on Voltage and Amperage...including fine tuning.

Also Nichrome C wire at www.nichromewire.biz.
Get and play with the following sizes(free shipping):
10' of 22 guage $5.25
10' of 24 guage $4.25
10' of 26 guage $3.50
10' 0f 28 guage $3.25


Ebay Link:
http://www.ebay.com/itm/Digital-DC-P...item4ab3c4bf10
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Old Feb 29, 2012, 02:01 PM
“Do it Right The First Time!”
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United States, MN, Hermantown
Joined Dec 2008
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nichrome wire. http://jacobs-online.biz/nichrome_wire.htm Free shipping


RKKIRK, Thats a whole lot of mony to cut a few cores. Might as well have them cut for you. On mine it puts out 28V, 4A. Used it for cutting a plug out of pink foam. This was 25# density foam, and easy to cut, but you have to go slow. On "white" foam 1-11/2# density, it would cut like a hot knife through butter.
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Old Feb 29, 2012, 02:27 PM
It wasn't me...
DanSavage's Avatar
Trabuco Canyon, CA
Joined Nov 2000
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Quote:
Originally Posted by CoolerByTheLake View Post
I just build one recently. I went with a 4amp transformer. http://www.jameco.com/webapp/wcs/sto...0001_221365_-1 I see it has went up a few bucks since I bought mine. Basicly all you need it the trans, a fuse, and a dimmer switch. With this amount of power, it was said to be able to cut cores up to about 36". I think it cost just a little over $40.00. Works well.
I use a 5A Nicad battery charger. It already has the transformer, fuse and dimmer switch built in.
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Old Feb 29, 2012, 04:14 PM
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United States, WI, Fond du Lac
Joined Sep 2008
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24V 40VA (if I recall correctly) transformer for furnace/AC control systems. Get them at home centers for under $20. Power it with 120V through a simple light dimmer switch. The higher voltage can run longer wires. I use steel fishing leader for the wire. I can run a 40" bow with this. More if I used nichrome wire.
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Old Feb 29, 2012, 05:11 PM
Rhys - Forever Learning
United Kingdom, Wales, Nelson
Joined Feb 2007
359 Posts
What size wire is the best?
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Old Feb 29, 2012, 06:16 PM
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United States, OH, Cincinnati
Joined Mar 2008
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wow, lots of good advice here! keep it coming, the more I have the more I can evaluate and make the best decision for myself!

Thanks a million everyone!
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Old Feb 29, 2012, 11:24 PM
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Columbus Ohio.
Joined Aug 2006
151 Posts
Yes, you can go cheaper, and your satisfaction and success will vary. But if you're really serious for the long haul, and want to get into scratchbuilt foam cutting in all its variations, I recommended the 30V 5A $115 power supply because once you use something like it, you'll never go back to something home brewed.

It's like the old saying...buy the best radio you can afford. The same holds true when cutting foam.

It's the voltage adjustability of the power supply that is key to heat control, which is the primary factor in good foam cutting. Dimmer switches are very coarse in voltage adjustment. The same holds true for analog voltage meters. The power supply I recommended has very fine voltage adjustment and digital readouts, thus it has very precise temperature control.

I also recommend that you stick to nichrome wire, it has high resistance, thus is best for heating. Stainless steel has less resistance, thus requires more amps(voltage), to attain the same heat as nichrome.

Attached below is a PDF chart of ohms per foot and the various gauges of nichrome. Also the chart lists is the number of amps needed for specific gauges of the wire to reach specific temperatures.

To find out how much voltage is needed to heat a specific gauge of wire to a specific temperature...go to the chart and find the amperage required for the desired gauge and temperature. Then go to the resistance section at the bottom and find the gauge and Ohms per foot resistance. Multiply the feet of wire you plan to use for your cutter by the ohms per foot...multiply that number by the amps value you found first...that gives you the amount of volts required to heat the wire to the desired temperature. You must choose a gauge and length of wire that will fall within the voltage and amperage maximums of your power supply.

In most cases in finding the ideal cutting settings, I cut samples...increasing the voltage by 1/10 volt increments. There will be a point where the foam cuts with little resistance. Then the next 1/10 volt hotter temperature will result in increased melting leading to wider kerfs. From there, hotter temperatures will lead to melted holes if the wire does not advance at an constant rate. Too hot a wire also results in noxious fumes...even smoke.

For longer bows 3-6' I would recommend 22, 24 or 26 gauge nichrome.
For shorter lengths I'd recommend 26 or 28 gauge.

Assuming 800 degrees Fahrenheit(which is overkill), the power supply I recommended could drive bows up to the following lengths.
22 gauge 6'.
24 gauge 5'.
26 gauge 4'.
28 gauge 3'.
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Old Feb 29, 2012, 11:56 PM
“Do it Right The First Time!”
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United States, MN, Hermantown
Joined Dec 2008
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Oryon, do yourself a favor, PLEASE read the link I posted. There is all the info contained within that link to satisfy most anyone. Go to the very bottom of the page, and you will see a nichrome wire calculator, click on it, tons of info. Also check out the side bars, lots more info. I have used my home made PS, and have cut pink foam up to 8" thick and 12" wide one pass, and can cut core up 36" with no problem. Bt the way, I can't say I have ever seen a 6 foot core used by any one here.

If you are going to make a living cutting foam, by all means spend the cash, but I don't quite see it. Take your time, and you will make a wise choice.
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Old Mar 01, 2012, 07:12 AM
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Bradford West Yorkshire, UK
Joined Apr 2010
1,532 Posts
Music wire cuts just as good/better than Ni-chrome.

Regards Ian.
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Old Mar 01, 2012, 09:34 AM
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Columbus Ohio.
Joined Aug 2006
151 Posts
Oryon

Here's another good site dedicated to foam cutting.
http://www.hotwirefoamcutterinfo.com..._Info.com.html
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