How Can Inserts be Used in Thermoset Molding

Designing a part for injection molding can allow for complex part geometry. Aside from molding intricate and complex parts, designers must also take into consideration how different parts are assembled or fastened together in a product assembly. One of the most common and inexpensive way to join two parts together is through the use of threaded inserts. Designers and OEMs rely on inserts as fastening mechanisms to mate multiple parts of an assembly. In thermoset molding, inserts can be installed in a secondary process after the part is molded, or they can be molded in and assembled within the molding cycle. Each process has it’s own benefits and advantages.

Molded-In Inserts

Molding-in inserts within the molding cycle is an economical way to implement inserts as there is no secondary step and secondary labor required to install the inserts after the product is molded. Molded-in inserts will require either an operator or end of arm tooling automation load the inserts into the mold prior to molding around them. The bonding between plastic and the insert is created during the as the resin material encapsulates the outside of the insert, which are usually knurled, holding the insert in the correct position into the part. Molders will need to account for a slightly longer molding cycle to account for insert loading time.

Post-Tapped Inserts

Post-tapping inserts is a secondary operation performed after parts are already molded where threaded inserts are mechanically driven into a molded part. Self-tapping inserts are an excellent option for molded parts that require a consistent cycle time that cannot be affected by manually loading molded in inserts. Loading molded-in inserts at the press can keep the mold open for too long, affecting the mold processing temperatures and potentially resulting in a rejected part or higher scrap % over of the course of a production run.