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The best castings come from patterns and coreboxes made by professional pattern makers. Patterns work best when half of the part is mounted on to one side of a board and half on the other. We have three professional pattern shops that we work with locally that make really good patterns at reasonable prices. They can work with your prototypes or with just your sketches and drawings.
We work with the pattern makers to find the best way to put as many patterns on one board as we can to reduce castings costs. We also help the pattern makers with gating and riser design.
For castings that are hollow or have difficult cavities or holes, we will need to use cores in the cavities. Cores are made of a hard solidified sand that the metal flows around and then is removed by knocking out the hard sand when the casting is cool.
We make our cores from sodium silicate and CO2 or with a shell core machine that uses resin coated sand. For high production jobs it is best to make core boxes out of aluminum and use the shell core method. But for most of our jobs we use wooden coreboxes and use the sodium silicate C02 method because it decreases tooling costs.
It is possible for the customer to try an make their own pattern but there are several things to remember. We can make castings from loose patterns (those not mounted to a board) but it is more time consuming so we have to charge a little bit more per casting. But this is usually the best way to go for prototyping and small runs because it reduces tooling costs.
Patterns are best made out of hardwoods, aluminum or a very stiff plastic so they can be polished and will be smooth enough that the sand will not stick to it.
The parting line should be clearly defined on the pattern so we will know where to split the mold. The sides of the part should have at least 3 degrees of a draft angle so it will be possible to pull the pattern out of the sand.
The best castings have an even thickness over the entire part but on a lot of designs this is not possible. We can make up for this in molding by adding risers, insulating sleeves and chills to help control the shrink in the heavy sections. Remember that the better the pattern is, the better your casting will be.
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Contact us for more information: Nyland@CreativeCastingCo.com
or send drawings or prototypes for a pattern and casting quote to:
Creative Casting Co.
3762 S. 60th St.
Tacoma, WA 98409
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