After watching this thread for a while, and valiantly resisting
chipping in my two cents worth - I gotta give in and let it out.
Number one - Unless you have an agreement with the cell phone
manufacturer - in advance - you are setting yourself up for a
lawsuit. Copying the shell or cover IS copyright infringement.
The design belongs to the cell phone company. You could, perhaps,
legally make your OWN design to fit their phone, as an "aftermarket
accessory," but you cannot copy what is already on the phone. (And it
better not look like theirs - that idea that constantly floats around
about how you can change 20 or 30% of someone's design and call it
yours is absolute BS)
Number two - While there are lots of things that lend themselves
well to small studio casting, this is NOT one of them. The myriad
problems you will encounter in trying to make a functional mold,
cast, hand fit, and finish this article would make the cost so
prohibitive as to wipe out any real profit. Profit is usually the
reason that we take on jobs. (grin)
Number three - The advice you've gotten thus far about casting an
article with this large and thin an area, seems to have come from
people who have not tried something like this. I have. Not cell
phones, but a similar enough item...
The first thing that has to be done is to allow for shrinkage.
Everyone seems to agree on this. Sure there are investments that will
cut that down, but you still have the shrinkage of the injection wax,
the liquid metal when it cools, and the fitting and finishing will
remove more metal.
IF I were to attempt something like this (and I wouldn't) I would
first ADD to the outside thickness of the cover. Then I would grind
away enough of the inside of the cover to have a loose fit to the
innards of the phone. The exact amount would have to be done by trial
and error, and it would have to be done perfectly evenly throughout
the entire inside. Probably lots of errors... Several molds, several
failures, to get it even close to right - so that after casting and
finishing it would fit as well as the original.
One other factor is that plastic flexes differently than metal. Is
the original made of plastic or metal? Cast metal will be more rigid
than thin sheet metal and may damage the inner workings of the phone
when pressed into place. I don't know enough about the model of phone
you're trying fit to say much about this. Is it a snap fit? Castings
are not "springy," but could be coaxed a bit by some judicious
hammering. But all of this depends on your getting an almost flawless
casting to work with!
Number four - No one seems to have mentioned that forming thin sheet
metal would be a far better option with more chance of success.
I'm sure that if he wanted to, Valentin Yotkov could do this by
hand, with nothing more than some hammers and a stake shaped like the
working part of the phone.
Another method, better suited to multiple copies - would be to make
a steel die set, and form it in a 50 ton or larger press. You could
make it of very lightweight sheet metal, and this would have a bit of
"spring" to it if you need a "snap fit" to attach the cover.
I am not in any way trying to discourage the idea of making cell
phone covers. Only trying to point out some pitfalls in the
"duplicate" casting method and offering ways to get around them -
legally, and technically - and without suffering as much as you might
if you pursue the direction(s) discussed so far.
All of us have taken on ill-advised or miserable jobs at one time or
another. This one sounds like it could have some of the makings to
become one of those...
Brian P. Marshall
Stockton Jewelry Arts School
Stockton, CA USA