A guide to permanent mold casting.

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These are some pictures I took when I toured a pewter factory in Malaysia.
The permanent mold casting process uses molds, often made from metal, which are used over and over, as opposed to other techniques like sand casting, lost foam or investment casting where the molds are destroyed to remove the casting. The molds in this picture are for a handle on a mug, there are pins in the mating faces of the molds to align the halves correctly and steps cut in the top corners of the molds so the halves can be levered appart when it's time to remove the casting. When the molten pewter is poured from the ladel into the molds, the molds are clamped together and tilted up on an angle to reduce the likelyhood of an air lock in the casting, as the molds start to fill the angle is steadily reduced to horizontal. Pewter has a very low melting point and solidifies extreamly quickly.

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As soon as the mold fills and pewter flows up through the riser, the lady turns the molds upside down to tip out the excess pewter left in the sprue and riser, puts the ladel back in the crucible then seperates the two mold halves. The time from the start of pouring to seperating the mold halves is about ten seconds, pretty quick. She then uses pliers to remove the casting from the mold.

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Once the casting is free of the mold, the sprue and riser is submerged in the molten pewter in the crucible so they are melted off and reused, the casting is wiped (where the sprue and riser was) across the edge of the crucible to smooth of the surface in preperation for further processing.

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This picture shows a few handles, the one at the bottom still has the sprue and riser on it. The handles are debured along the parting line, as there is usually a small abount of pewter which makes its' way outside the mold line which needs to be cleaned up. They are then fused to the body of the mug, polished and put in the show room for sale.

[trubleshtr]

Neat little process, what temp is the pewter at? she does not seem to be wearing much in the way of safety gear?

[Lion's Den]

Great Pics! Thanks for shareing

D

[sendkeys]

nice pics. I was thinking of doing some pm casting like she is doing there. But now that i see the parting line size. sure would make ALOT of work to clean it up.


as for another question pewter pours around 600-650f. If it was me i still have a little more protection haha.Pewter is cool but it's soft and cost is high.

[Splint]

Thanks guys,
I dont think there's really that much work in processing the castings, the picture of the handles shows the bottom one with the sprue and riser still attatched but they are simply melted off by submerging them in the molten pewter. After that you would need to use a scraper,file or deburing tool to give the parting line a clean up around the entire parting line (where the two halves of the mold join). Next you would file the surface (which would be done in a jig) where the handle mates to the body of the mug, after fusing the two together you wuld then polish and buff the part which wouldn't be overly difficult or time consuming if you had a buffing wheel on a bench grinder.
Cheers
Splint

p.s. Sorry, I dont know the exact melting point of pewter, perhaps around 200 to 250Deg. Celcius. There was a perspex sheild between the crucible and the audience, but I suspect pewter is faily stable and safe if you use a little comon sense. Having said that, I'll be covering up as much as possible and taking many precautions when I eventually start casting aluminium.
Cheers guys....