How Stack Molding Benefits Your Plastic Injection Process

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Stack molding is a powerful tool to enhance the plastic injection molding process. The simplest definition of stack molding is in its name. Stack molding is stacks of two or more mold parting surfaces, also called mold split lines. stacked together in parallel layers. Using stack molds can double an injection machine’s output, provide versatility, and lower the cost of operation.

Stack molding increases output capacity without a complimentary increase in mold or machine size. Each mold parting surface is adds a parallel layer of cavity grids. The most common cases for stack molding in a plastic injection molding process is to create identical copies. So a stack mold with 4 + 4 cavity grids will result in 8 copies per cycle. Fill, pack, and cooling times remain the same since the area involved is the same. Only the mold open and close times add any overhead to the process.

Identical copies might be a very common use of stack molding, but it is by no means the only configuration. Stack molding removes the necessity to make several runs in order to create parts for a product. Cavity grids can be made to create several different parts for one finished product in one run by using stack molds. Stack molding will also support multiple material injection allowing for a broad set of possibilities.

Output increases but cost of operation goes down when using stack molding. A stack mold only needs half the tonnage of a similar single phase mold with the same number of cavities. Part cost comes from the machine hour rate which is affected directly by tonnage; the reduction in tonnage with an increase in output means each part costs less to produce.

Stack molding has great potential to improve the field of plastic injection molding. Reducing cost while increasing capacity with a limited increase in overhead time would be welcome to any bottom line. The versatility and savings provided by stack molding means its use will only increase over time.

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