Molding

Tooling for molding consists of two halves that are joined together under pressure. Molten material then enters and fills the tool. In other cases, material is placed in the mold cavity and then expands under heat and pressure. Most types of molding require engineers to keep certain factors in mind when designing parts. Specifically, avoid overhangs, sharp corners and changes in wall thickness and incorporate draft for efficient ejection of parts from the mold.

During the molding process, heat and pressure force the material to completely fill the mold cavity. The part then cools and solidifies. In the case of injection molding, cooling channels may be incorporated into the tool to speed this process. A draft angle on the part and tool helps ensure the part can easily be removed or ejected from the tool. For certain processes, curing may be required to complete the solidification process.

Molded parts may go through multiple steps after the molding process is complete. Flashing (excess material that escaped through the parting line between the two halves of the mold) may need to be trimmed. Witness marks caused by gating and parting lines may need to be sanded. Inserts may be molded into the part or heat staked during post-processing. Painting, coating, labeling and assembly are other common finishing steps for molded parts.