Making a foam hot wire cutter

[flanajb]

I want to make a hot wire cutter for cutting my foam vacuum form templates and wondered whether anyone can comment as to what I will need. A lot of the articles online are for small cutters used for cutting aircraft model wing components, where as I need one that can cut upto 600mm across.

Thanks

 

[Mcluma]

Soldering pistol with a long coper wire

 

[Dibs-h]

I've tried it - guitar wire is good to experiment with and cheap. Get a ones of a few different thicknesses. Cheap as chips.

Power supply - 12v with a bit of umph is required. Also depends on the density of the foam you want to cut. I was using a power supply that had an output in excess of 1.5A and it wasn't a huge success. Might have had something to do with the fact that I was trying to make one 1m wide and the foam was very dense.

Also note that as the wire heats up, it will lengthen, therefore sag.

2' might be doable. I'd be inclined to knock up something resembling an H frame. Pivots (screws should initially do) on the intersections between the horizontal and the verticals, wire across the bottom and you can adjust the tension by hand, by pulling the uprights, inwards at the top.

Worth a punt.

HIH

Dibs

p.s. model railway power supplies usually have enough grunt and have a dial to vary the output. :wink:

 

[flanajb]

p.s. model railway power supplies usually have enough grunt and have a dial to vary the output. :wink:

Thanks. Never thought of using a model railway power supply. One of those wired to a car battery should do the trick?

 

[Lowlife]

I'm not sure a model railway transformer would be up to it? Certainly when I tried it at home years ago it didn't work, I tried a cheap car battery charger too but both just kept cutting out.

The one we use at work runs off a heavy duty battery charger with a car battery as a buffer, the wire is nichrome which is easily obtainable, you can buy it in lengths with a loop already formed at each end if you want. To take up the slack as the wire heats and expands you need a spring of some sort, the "terminals" on ours are lengths of piano wire which has enough spring in it to keep the wire taut, each terminal has a groove filed around the tip in which the loop of the nichrome wire sits so it doesn't slip.

Temperature control on ours is simple, a length of wire from an old electric bar fire with a croc clip that can be slid along to adjust the power.

 

[Dibs-h]

You need one with wire wound transformer in it as opposed to one of the newer type of power supply units (the phrase that describes them escapes me for the moment) that can sense a short circuit and will cut out.

Dibs

 

[lincs1963]

In 1996 I was working in China building blast freezers for the Chinese Administry of agriculture at some poultry processing plants in Shandong provence. These freezers were built out of polystyrene cored panels and here in the UK we were cutting the rebates with a throw away hardpoint saw, it's hard work but effective. after a day rebating panels with the native labour force, they decided there was an easier way. So the next morning they had made what looked like a bow saw with a wire instead of a blade, long enough to rebate a 4' panel. this was powered by a small arc welding plant. It worked very well you just had to be very careful not to catch the metal skin on the panel as this seemed to form a hotspot on the wire and snap it!
I found the Chinese to be very resourceful and they had a different approach to most jobs.
hope this is of interest, neil