Mold Design and Tooling for Injection Molding

Injection molding is a high-precision manufacturing process that injects molten plastic into a carefully designed mold, where the plastic cools and hardens into the specified part or product. The piece is then ejected from the mold, either as the final product or as a near-final product that is sent on for secondary finishing.

The injection mold consists of two parts: the mold core and the mold cavity. The space that these two parts create when the mold is closed is called the part cavity (the void that receives the molten plastic). Depending on production needs, “multi-cavity” molds can be designed to create multiple identical parts (as many as 100 or more) during the same run.

Designing the mold and its various components (referred to as tooling) represents a highly technical and often complex process that requires high precision and scientific know-how to produce top-quality parts with tight dimensions. For example, the proper grade of steel must be selected so components that run together do not wear out prematurely. Steel hardness must also be determined to maintain the proper balance between wear and toughness. Waterlines must be well-placed to maximize cooling and minimize warping. Tooling engineers also need to calculate gate/runner sizing specifications for proper filling and minimal cycle times, as well as determining the best shut-off methods for tooling durability over the life of the program.

what Mold Design is Most molds are made from hardened or pre-hardened steel. Hardened steel (heat treated after machining) has superior wear resistance compared to pre-hardened steel and lasts longer. Although steel molds are more expensive than molds made from other materials, such as aluminum, they are more durable and support a higher rate of production before they need to be replaced.