Subject: Re: Any way to re-use plaster molds

From: [email-masked] (Andy Dingley)
Date: Thu, 06 Jun 1996 00:12:08 GMT

The moving finger of [email-masked] (Nick Irias) having written:

>I want to cast a large number, about 170, of small aluminum parts.  Is
>there any possibility of re-using a plaster mold for this?  

I'd approach this by making a slightly flexible positive master in
catalyst-cure polyurethane, with maybe half-a dozen links on it, and
all the sprues. From this I'd cast as many plaster moulds as I needed,
then cast all my metal in one pouring.

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From: [email-masked] (Mike Schechter)
Date: Thu, 06 Jun 1996 17:18:04 -0400

In article <[email-masked]>, [email-masked] (Nick Irias) wrote:

> there any possibility of re-using a plaster mold for this?  The parts
> are scale tank track links, about 3"x1"x1/4", and should have good
> parting angles.
> 
> Thanks for any suggestions re: how to do this
Use 2/3 plaster, 1/3 pure silica sand.
Used for bronze casting, and can be pre-heated to 1300F
before breakdown of the material. so it should last
for quite a few aluminum castings.
Also, don't forget to do multiple parts/cast if possible.
Also (ain't i great)- consider making a master mold, that you
can pour wax or lead into, then take apart to get wax/lead parts out of,
use several of these to build up a tree of parts, then
make a master of THIS, with 10-20 parts on it.
Then use this new master to make a wax or lead  with 20 of 'em onit.
then pour plaster waste molds around this 20-masters.

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From: [email-masked] (Peter Brooks)
Date: 7 Jun 1996 17:09:14 GMT

Nick Irias ([email-masked]) wrote:
: I want to cast a large number, about 170, of small aluminum parts.  Is
: there any possibility of re-using a plaster mold for this?  The parts

While my foundry knowledge is from a couple of books and the net (haven't 
built my melter yet), it sounds as if you'd like to make a bunch of cores.

I'd think about making a single core (or possibly two core halves) and casting
up a bunch in whatever is cheap and easy to work with.  I'd guess plaster
would be OK if you could protect it, perhaps with an epoxy to toughen the
surface.

Mount about 10 sets of the cores on a match plate any you would only have
17 melts, assuming you can melt that much metal in one shot.  Adjust the
numbers to suit your needs.

I'd guess there's no real reason you couldn't make core sets from aluminum,
though you'd have two increments of shrinkage to deal with.

Any *real* casters care to chime in?  I'd like to learn, myself.

Pete Brooks

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From: PPIERCE <[email-masked]>
Date: Fri, 07 Jun 1996 21:48:30 -0700

Peter Brooks wrote:
> SNIP...

Try http://ourworld.compuserve.com/homepages/brnzcaster.

Paul in AJ AZ
A wannabe caster
probably never tho'

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From: [email-masked] (Edward Haas)
Date: 9 Jun 1996 20:14:00 -0700

: Mount about 10 sets of the cores on a match plate any you would only have
: 17 melts, assuming you can melt that much metal in one shot.  Adjust the
: numbers to suit your needs.
	--If you arrange them like a tree and do investment casting, you 
gain the third dimension and can cast many more. I did this for bronze 
casting of some tricly stanchions and I got all I needed in one pour...
-- 
	"Steamboat Ed" Haas	:	Another proud member of 	
	COMING SOON		:	The Anti-Virus Vigilanties
	http://www.west.net/~steamer  	
		---Decks a-wash in a sea of words---

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From: [email-masked] (Edward Haas)
Date: 9 Jun 1996 20:27:54 -0700

Edward Haas ([email-masked]) wrote:
: casting of some tricly stanchions and I got all I needed in one pour...
	          ^^^^^^ 
	That word is "tricky" as in they were wax pieces, affixed to a 
central "tree" of wax, then put in investment for burning out prior to 
casting in bronze... The use of the "lost wax" process is simple and 
allows one to make many copies of the original in a relatively short span 
of time and to incorporate unusual geometries, without the problem of 
"coping down" to a parting line, since there is none...
-- 
	"Steamboat Ed" Haas	:	Another proud member of 	
	COMING SOON		:	The Anti-Virus Vigilanties
	http://www.west.net/~steamer  	
		---Decks a-wash in a sea of words---

---

From: [email-masked] (Raymond Frye)
Date: Mon, 10 Jun 1996 11:00:00 -0800

References: <[email-masked]> 
Nick Irias writes:
NI> I want to cast a large number, about 170, of small aluminum parts.
NI> Is there any possibility of re-using a plaster mold for this?  The
NI> parts are scale tank track links, about 3"x1"x1/4", and should have
NI> good parting angles.

-----------
The volume / weight of your pour is small so it's best to have all your
molds made and preheated for one melt.

Gang your parts. It would be better to make 17 molds of 10 parts each or
10 molds of 17...

The quantity is such that either a rubber molds can be used to make
parts that assemble into the molds or wax parts to be assembled prior
to coating with investment. Arrange the parts to make best use of your
equipment.

Since this is scale tank track you may want to add details that allow
casting urethane rubber pads onto each track. This can be done with
reusable molds but a reusable mold/pattern to make all the molds for
all the parts. You only mix one batch that way.

Ray

Oh, and keep us informed on how the project is coming along. Not just
castings but road wheels, drive train, M4, M60, T34....

 * RM 1.3 02229 * It's metal, it moves.....Fun Stuff!