Sunday, February 26, 2017

Hot Wire Foam Cutter

Over the last few weeks I started looking at different soft cases available for my AR15. The particular cases I was looking at were in the $50-$80 dollar range when I came across the Plano All Weather Rifle Hard Case for $62.00.

Plano claims their All Weather cases "create watertight and airtight shields that protect your guns even in the most extreme conditions" and "are designed to withstand the continuous bumping and jarring of airline travel". I found a lot of positive reviews on it so I went ahead and ordered one.

The main layer of foam in the case consists of approximately 2.5" of "pick and pluck foam" which consists of partially cut 1" squares. Once you have traced an outline on the foam you pluck what is not needed. It makes it easy to make a cutout for the gun but it gives it an unsightly appearance and it is not at all durable. It is not as supportive as solid foam and if anything catches on the foam it will pluck that piece out.

Here is a picture of a newly done gun case with pick and pluck foam, note how the pieces around the gun are already starting to be displaced.

 This one shows the same type of foam after it has been in use for a while. You can see where it has started to deteriorate and separate.

 The alternative is using solid foam that is cut specifically to the items you are trying to protect. This is a far more durable option that produces a more professional appearance. There are various ways to cut solid foam from regular knifes to water jets and lasers. Hot wire cutters are fairly simple and make very clean cuts so I decided to build one.

I purchased a folding tailgate table from "The Walmart" and using some scrap metal I had along with some uni-strut constructed a, way more complex than it needed to be, hot wire foam cutter.

The folding table made the entire project much harder than if I had just used a simple piece of wood. I wanted something I could fold up and put away when I wasn't using it.

The top piece of the cutter has an adjustment knob for when the wire heats up or stretches. The wire itself is Kanthal and seems to be fairly durable. The adjustment knob also allows for the wire to be quickly disconnected and strung through the foam for making inside cuts. The fan was a last minute addition to blow the smoke away from the cut.

The cutter clamps to the sides of the table by interference fit. There is a common beam across the bottom that has a tongue which fits into the main piece. This is also interference fit which allows the entire cutter to be quickly installed or removed.

A simple automotive battery charger is used to apply 12v @ 2 amps to the cutting wire.

This video shows the cutter in action with an old piece of 3" thick foam. This was the first time I tried using it.

With the cutter working the next step was to make templates for the items I wanted in my gun case. Using poster board allows the wire to be run along it, because the wire wont quickly cut the poster board it makes for very accurate cuts.

The templates are difficult when the item does not sit flat, the gun itself took me about 90 minutes to accurately trace. This can be done more quickly if fit is not a big concern.

Once it was traced out I cut it with scissors and pinned it to the foam. It took about 6 minutes to cut it out with the hot wire. The cutouts are then placed on their side for a perpendicular cut this is to make a piece that goes back in the cutout hole and raises the item in the cutout hole. In the picture below I set up a simple fence for the amount I wanted to cut off the gun cutout. If I were to make a hot wire cutter again this would be something I would include in the design.

Overall I am very happy with the hot wire cutter, I have about 45-50 dollars invested in it. The foam itself can be very expensive, I was lucky enough to find a few pieces in the trash at work that were close to the size I needed. Below is a shot of my first try at foaming my gun case, It was a lot of work but I am very happy with the outcome.

I positioned the gun to the left side in anticipation of the Hearing Protection Act. To offset the weight of the gun I have 5 loaded mags positioned to the right with a minimum of 1" spacing from any item to the edge of the foam.