Re: Mold Plate for Aluminum sand casting.

ArtMetal
Bramblebush


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Posted by Rob Frink on April 20, 19100 at 21:35:25:

In Reply to: Mold Plate for Aluminum sand casting. posted by Robert Brown on April 19, 19100 at 14:57:27:

Hello Bob,

I'm not sure what you mean by "mold plate" but I have some ideas that I hope will help.

The first is a match plate which is simply a plate with the patterns mounted on both sides so that you can ram the cope and drag with the plate sandwiched in between. After seperating the cope and drag and removing the plate, the mold cavity is left behind and nearly ready to pour. Great for speedy molding with high quality repeatabilty because they can eliminate the hand work associated with carving gates and runners as well a carving to a parting line in a solid pattern. If the pattern is simple and symetrical then the construction of the match plate is simple. You just make the pattern in pieces about the parting line and fasten them to the plate. You can add the gates, runners and risers as well.

Since your pattern..(a propeller)...does'nt have a very straight parting line, I would opt for an "odd side" plate. The odd side is a pattern plate in which the loose pattern (your propeller) is molded into a female form on a plate. The form on the plate is the shape of the sand that you would have to scoop out to get to the parting line. They are somewhat easy to make. I'll take a flat board and plop a pile of wet Bondo in the middle. Before the Bondo sets, I press the oiled pattern (propeller) into the bondo and allow the bondo to ooze around the pattern. When the bondo stiffens up, I carve it away down to the parting line. (for the prop, I would carve down to the leading and trailing edges of the blades and to the center of the hub.) You can do the same for runners and such. Then work the pattern loose and relieve the female impression in the bondo so the the pattern will easily drop out. In the foundry, you simply place the pattern in the female impression on the plate and ram half of the mould. The flip it, remove the plate but leave the pattern....sprinkle some dry parting and ram up the other half of the mold. Seperate the two halves, remove the pattern, cut your gates, sprues..etc and your ready to pour.

If you are only making a few castings, I would probably forget the idea of plates and simply carve out the first half of the mold by hand to the parting line. In the time it would take to make a plate, I think you could manually cope out a dozen molds or so.

I'm guessing that you've inquired with a local foundry and they responding with match plate requirements to fit their molding machines. If this is the case, you might be better off checking with the industrial arts in a local school or college to cast the props for you...or inquire here. I'm sure several of us would kindly help you out.

If you would like to learn more about pattern making, molding etc. I can recommend books by C.W. Ammen. His focus is at the small shop and backyard guy. Try amazon.com for them.

Well, I didn't mean to ramble...I hope it helps and feel free to drop me a line if you have questions or comments.

Have fun

-Rob


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