Wax casting


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Posted by Jack Davis on November 07, 1999 at 08:11:57:

Probably the weakest part of my foundry is wax casting. Though what cast is very workable, it still leaves room for much improvement. Air bubbles of course. I have cut small evac slits/holes into my silicone molds in a few problem areas (upward pockets) to let the air escape and hope they "freeze quickly". With pressure method (leakers everywhere)and doesn't get to the air pockets. With vacuum the wax is setting before the vacuum can do it's thing, unless you have a large fast source. Vibrating which I haven't tried, but it could do some good. Or jogging or rolling in side to side motions as you pour, which becomes an art to hit the pour hole. I spend too much time in wax chasing, and need to rid some of the problems. My designs of very high detail with many appendages and about 2 to 4 lbs of wax (14 to 20 inches). Just for example; an octopus with legs going in all directions including up and down. I have even tried the slushing and pourout method once, but the wax was in too many differing heat stages, and poured out totally in the heavier mass areas. If I precool the mold the problems even get worse. I normally somewhat preheat my molds to give me extra time to work with the voids and small surface bubbles, but if they are too warm the wax tends to leak out the mold a lot. So far I have got my best results with a slightly warm silicone mold, a cool and even wet mother mold, with wax temps within a critical 5 degrees and rolling from side to side and in a wide circling pattern as I pour the wax in about 3 to 4 quick stages. To summarize this long inquiry, I would emphasize the amount of time that many of us spend in the wax chase, and the amount of time used in chasing a bad wax over a good one. Thanks for any input,,,,Jack

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