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Discussion Starter #1 (Edited)
As promised, the following is a short guide to making an inexpensive hot wire cutter for making budget custom cases(not just for guns)

First, a few pics of the cases I've made for those that haven't seen them:

Empty.800.JPG Full.800.JPG HBR.FRT.a.800.JPG HBR.FRT.b.800.JPG


Shotgun Case Here

Physical construction:
Construction of the cutter Base isn't critical, just make it big enough to hold longer pieces of foam without catching on the edge, and use material with a smooth top(I used a piece of old desktop with Formica laminate on it) Mine is 28" x 28" Give yourself 4" or so of clearance underneath for electronics.



I used 1/8" x 1/2" flat steel for my bow, it provides just enough tension on the wire - just be careful when bending it initially - if you go too far you'll ruin the tension.





The wire attachment on the bow is a bent screw, allowing adjustment to square up the wire.(You can see I left a loop in the wire so I can remove it to pass through foam.)





Attachment under the base is another screw, 90 degrees to the top screw for adjustment to square.



Electronics:

Wiring diagram:



The transformer can be found at any Radio Shack, about $15 from what I remember.

Ni-Chrome wire can be found at any hobby shop that carries radio controlled planes, or online(I use 26 ga)



I pulled the guts out of an old computer power supply because I wanted a removable power cord and a switch - you can always use a cheap cord and switch instead.





A very inexpensive light dimmer(120V) controls the heat.



The top electrical connection for the hot wire can be made directly to the steel bow(low voltage at that point so no danger) You can see that I attached the bow with a wing nut so the bow can be swung down for angle cuts.



Doesn't everyone have an old power supply? Sure makes a nice clean switch/power connection...



A couple of my templates - I like to use "negatives" when I can, if you screw up the inside, it's ok, that's what you discard.(not all of it, after you have made the cutout for the gun, cut the "plug" to the width of the gun and place it back in the hole to cushion the bottom)

When you trace the part, go INSIDE at least 1/8" - 1/4". This will make the foam tight around the part or gun, holding it very firmly.



This is what I use to pull the wire through the foam - just make a plunge cut with a knife after positioning the template and pull the wire through, looping it back over the wire on the bow.

 

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Very nice and informative. I will be giving this a try as I really like what you have done. ONLY IN AMERICA!!!(sorry)
 
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Thanks for posting this.
 
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Nice job on the fab work. Thanks for sharing your idea..
 

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That is great. Stupid question, you don't get shocked if you touch the bow or wire?
 

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Discussion Starter #7
That is great. Stupid question, you don't get shocked if you touch the bow or wire?
No shock because it's low voltage, but if you touch the wire when it's on, you will regret it! With the light dimmer, you can make the wire glow red-hot, but that is too much...the wire won't last as long if you do. Also, the bow doesn't get hot, just the wire.

Here's a couple pics of my latest and greatest...



 

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That is a nice DIY hot wire cutter and just my style, cheap!

Now any good sources on cheap foam?
 

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A bit far for my legs.
 

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Howdy VTB,

Nice cutter!

Back in the 90's I worked at a place that made styrofoam and they had a very similar shop built foam cutter that production used to cut big blocks into smaller pieces.

Thanks for posting your project.

Paul
 

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Fantastic. I am also constructing a hot wire foam cutter to make custom case inserts, and I'm running into some issues... namely my hot wire will not heat up.

I'm currently using a #10 plain steel guitar string connected to a 12VDC 1.5A wall wart. After no heat in the setup, I stripped it all the way down to just twisting the power supply's stripped copper wiring directly to the string. I've left it on for a good ten minutes (even the power supply is getting warm so I know it's juicing) but still no heat on the wire. Any idea what I'm doing wrong? Thanks.
 

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You need the actual Nichrome wire because it is made for this process. Any other wire just will not work. Google "Nichrome Wire" for it's characteristics.
 

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Very nice work.
 

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Discussion Starter #15
You need the actual Nichrome wire because it is made for this process. Any other wire just will not work. Google "Nichrome Wire" for it's characteristics.
Other types of wire can work, but Nichrome is by far the best. If the wire doesn't heat up immediately(faster than you can get the foam moving), it's not going to work. I think I paid $5.00 for 4ft of Nichrome...
 

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That's a basic tool used for building Foam RC Aircraft. I've seen variations of it for years. Your's adds in the bow for tension which is definitely a step up over 90% that I've seen. The use of Nichrome wire is crucial to low voltage operation. Excellent design and even a better presentation. Now I'll have to buy more guns to facilitate the need for the foam cutter.
 
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I use to be a flying wing vendor for over 12yrs. Still have my CNC foam cutter. Just wanted to post a tip for those who may try this. I always measured the AC voltage to keep from trying to find the right amount of power to run with-keep in mind it will change with wire length as the resistance will go up .This will eliminate guessing every time you use it.

Also another idea is to use nylon bushings or ceramic to attach your wire to. This will help isolate the wire from direct metal contact as well as reduce the load.Attaching the wire directly to metal will increase the resistance.I agree with the other posts about the use of Nichrome then a steel guitar string.The same thing applies when it comes to resistance.It does work ,but is far less efficient.I would compare this to a short duty cycle on a welder.

With what I mentioned above I was able to use the same transformer for 10yrs and hours on end with little worries of over heating. I would usually give a 30 min cool down after 2hr of continuous use.

thanks for the great post. These variations of foam cutters have a very wide range of use,
 

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Fantastic. I am also constructing a hot wire foam cutter to make custom case inserts, and I'm running into some issues... namely my hot wire will not heat up.

I'm currently using a #10 plain steel guitar string connected to a 12VDC 1.5A wall wart. After no heat in the setup, I stripped it all the way down to just twisting the power supply's stripped copper wiring directly to the string. I've left it on for a good ten minutes (even the power supply is getting warm so I know it's juicing) but still no heat on the wire. Any idea what I'm doing wrong? Thanks.

The resistance of the wire you are using is way too low. It will never heat up because it's not enough of a resistor. Get the listed wire the OP uses and it should heat up.
 

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I wish I'd seen this before I hacked up the barrel cutout in my Beretta shotgun case, attempting to enlarge the area for a longer barrel with an extended choke attached. This post has prompted me to build one of these slicers and redo the foam insert in that case.
Mucho thanks!
 
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