Plastics Mold Design | Technologies & Technical Expertise | Cove

Steps and components of mold design

Technologies for optimizing the mold design process

A mold plays an integral role in part creation – determining a part’s shape, surface texture, dimensions, molding cycle, efficiency and end-use performance. An injection mold must be precise, but strong enough to withstand thousands of high-pressure molding cycles. Successful molding depends heavily on the mold’s design and construction.

Common draft guidelines for mold design
Common draft guidelines for mold design

In thermoplastic molding, molds perform three basic functions: forming molten material into a shape, removing heat for solidification and ejecting the solid part.

Basic molds have two main components. The cavity forms the external surfaces, and the core forms the internal surfaces.

Specific materials require adjustments to the design of the runner system - a material delivery system consisting of a sprue, runners and gates - which channels the resin through the mold into the cavity. Amorphous resins, such as Makrolon® polycarbonate and Apec® high-heat polycarbonate from Covestro, require larger sprues and runners than semicrystalline resins.

Mold cooling-channel design should be addressed early in the design process, as good mold-cooling design maintains required mold temperatures, provides uniform cooling and facilitates short molding cycles.

Thermoplastics typically shrink significantly as the part cools and solidifies. Covestro publishes typical mold shrinkage ranges for our materials, which mold designers can reference when compensating for shrinkage. The mold designer should be aware of part geometry or mold construction factors that can determine where, within or beyond the typical range, the actual shrinkage will fall.

Materials experts from Covestro can help in the mold design process, resulting in a well-engineered and constructed mold that contributes to enhanced molding efficiency, reduced down time and scrap, and improved part quality.  


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