I'm getting a bit into metal casting, and I was wondering if there was a good way to press images into the metal while it's molten. I'll be working
with zinc. Is there a recommended material to press with? What should the cast be made out of? Thank you for any input.12AX7 - 10-8-2006 at 14:40
Pour into a mold.
Use a die.
Material doesn't matter, so long as melting point is greater than the metal you're touching, and it has a nonstick coating (rust works well).
It sounds like you don't want die casting, which is good, since the pressures and molds required are both rather annoying outside of an industrial
budget.
Timfranklyn - 10-8-2006 at 18:02
The fact that you're posing this question at all tells me you're getting
in over your head too. Read up on this first, the library will have some
books on metal arts and crafts. These will tell you everything.
Small hobby casting of decorative items usually in relief ( raised image )
can be done by carving a pattern in wood or plastic of what you want
the piece to look like. This lightly oiled master can then be covered with
plaster of paris to make your mold. After it hardens the pattern can be
removed and the mold is ready to pour.
L A R G E production runs , tens of tousands at least, are done by die
casting. You'll need to hire a tool die machine shop to make the die parts
of molybdenum , by electric discharge machining. You can buy a new
sport utility Hum Vee for what it will cost you. You'll also need to hire
a factory that will use your dies to turn out the castings.
I have looked into this with the idea of making a reasonable production
run on a shoestring budget. I determined that lead bullet casting machines
and molds could be adapted to other simple shapes and the operating
temperature is similar, about 800 Farenheit for Zamak and ZA 8 alloys.
Mind you, no one casts zink bullets so you will have to obtain expertise
from a die casting engineer to make something that can work with this.
This company expressed a positive interest in my project, http://www.ballisti-cast.com
try this one also, http://www.magmaengineering.com
.12AX7 - 10-8-2006 at 18:56
A large die may cost a Hummer. A smaller one, made of tool steel BTW (what would you use molybdenum for, die casting steel!?!?) should be in the
$1-10k range.
Hand molding methods can be used for suprisingly large quantities...(say up to a thousand). It's just tedious to do all the work. Incentive to get
fast at it!
But that's if you want quantity anyway...you didn't say.
Timfranklyn - 11-8-2006 at 08:02
Quote:
Originally posted by 12AX7
A large die may cost a Hummer. A smaller one, made of tool steel BTW (what would you use molybdenum for, die casting steel!?!?) should be in the
$1-10k range.
A die made of steel is a great idea if you use lead, with zink it will become a
paperweght of galvenized steel, the reason molybdenum dies are used to
cast zink. Mind you this is a die not a mold, if you know the difference. Die
cavities can be made with nitrided surface treated steel but it doesn't last.
BTW ( Steel is never die cast, it can be die forged though ) I have actually
costed these things some time back. If dies of any kind can be produced
for 1-10 dollars this under bids even the chinese.
Post the name of a maker I'll put an order.
[Edited on 11-8-2006 by franklyn]12AX7 - 11-8-2006 at 13:21
$1-10? Do you understand "k" (kilo = 1,000 x)??
A quick Google shows no relevant hits for "molybdenum dies". You'll have to try better than that. I would believe molybdenum-CONTAINING steel alloys
though.
Another quick check shows chromium and carbon are the primary die alloy additions, with smaller, variable amounts of V, W, Mo, etc.
Timfranklyn - 13-8-2006 at 00:23
After google searching I will conceed that this seems to be an esoteric
industrial art. It has been a few years ( 15 or more ) since I investigated
permanent mold die casting. It may be that the technology in use then
has been superseded. Understandable because of potential cost savings. http://www.jobshop.com/techinfo/papers/dcp_diealloys.shtml
Improvement in surface treatments for steel substrates may be the key http://www.tdcoating.com/SME_June96.htm
In the hot chamber process ( which is all that I considered or contemplated )
alloys of molybdenum were in use for die cavities because of its high thermal
conductivity and resistance to soldering. The aluminum , zinc , eat away
at ferrous die components, why I metioned before it didn't last.
See Die Casting Machines page 35 and 36 here -> http://www.epa.gov/compliance/resources/publications/assista...
this is the same as above http://www.p2pays.org/ref/01/00388.pdf
The gooseneck mentioned is the cold chamber procees in which measured
amounts of the metal being cast is ladeled into the die.
For the cold chamber process an appropriate steel alloy works because
of the lower operating temperature and the surfacing of the die cavity
between shots with a release agent which, interestingly, is
molybdenum disulfide.
