Semirugged Cellphone Case

I’ve had a cell phone of one sort or another since the early 1990s but even when they finally shrunk to a size that made them comfortably pocketable, I rarely carried one. You can’t do real work or efficiently surf the internet with a smartphone so I always carry a tablet. And because I’m a serious amateur photographer, it’s with disdain that I view the camera capabilities of any smartphone.

So when I heard of the Panasonic CM1 Android based smartphone with a one inch 20 megapixel sensor and a Leica lens, I knew the future had finally arrived. But the retail price of over $1000 meant I did nothing for nearly a year until Panasonic slashed the price in half just in time for additional Black Friday savings.

Being such a niche product, Panasonic never expected to sell many of these units and as a result there are no available aftermarket protective silicone cases. The type of case that is energy absorbing and able to protect your phone from a mild drop while adding minimum bulk.

Apparently I was destined to make my own.

I thought the silicone polymer material that dental mouthguards are made from would be an ideal material to make a custom fitting cell phone case. The material typically comes in 5”x 5” sheets so I had to use a butane fueled torch to heat and melt two sheets together to form one sheet large enough to cover the cell phone.

A very accurate mold of the cell phone was made with polyvinylsiloxane putty, used to take oral impressions for fabricating dental prosthetics. Alternatively you could use a variety of urethane liquid rubber products (www.smooth-on.com) available widely at arts and crafts stores. A stone model was made from this mold and was placed on a short stack of coins to elevate it above the perforated vacuum forming box.

This box was constructed out of pine with a single 2.25" circular opening to accept the hose of a Shop-Vac.

The extensively perforated top surface is where the vacuum delivered by the Shop-Vac would be drawn down from.

A pair of rectangular steel frames made from common steel stock available at hardware stores was very poorly MIG welded together . The 10"x5" polymer sheet was sandwiched by the pair of metal frames and held together with binder clips. The whole affair was placed in a 400 degree oven for about five minutes until the material was seen to sag and turn clear.

Wearing oven mitts, the frame was removed from the oven and quickly placed over the top of the wooden box, pressing down over the stone model with the Shop-Vac running. The hot and pliable polymer sheet can be seen to be drawn tightly over the stone model by the vacuum. Wait for it to cool sufficiently to handle.

After you separate the material from the metal frame and stone model, you need to trim the case grossly with a pair of scissors, and then finely with a razor blade.

And there you have it, a custom tight fitting case that looks store bought.