Threaded Inserts | Ultrasonic/Heat-Staking Inserts

Amorphous plastics are the most forgiving with this method given the broad softening properties of the glass transition, but semi-crystalline thermoplastics require more energy to cross its melting temperature. On the other hand, heat-staking machines directly conduct heat through the insert tuning only the temperature to 50°F (or 20°C) above the melting temperature of a semi-crystalline thermoplastic. This quickly melts the material without burning it, but amorphous plastics require more trial and error to optimize the install temperature. Thermosets do not accommodate either of these installation methods.

Application

Heavy-duty power tools like a cordless drill must be both sturdy enough to withstand the dirt and wear and tear associated with a construction site while also being light enough to comfortably use for the entirety of a workday. This is accomplished using an amorphous, thermoplastic housing with threaded inserts to securely seal the electronics of the drill from its environment. The amorphous plastic is light and extremely impact resistant as opposed to semi-crystalline thermoplastics or thermosets, and the glass transition allows for ultrasonic inserts to be installed faster and with less energy into the molded bosses than heat staking inserts.

Heat staking inserts can provide strong threads in molded plastic housings for heavy-duty tools and equipment.

Alternative Solutions

Given the complex shapes of handheld power drills, molded-in inserts might make mass production faster, especially for higher volumes, and would provide the best performance. However, for a smaller, less established brand that doesn’t have access to the tooling and equipment, ultrasonic or heat-staking inserts could serve as a more economical means by which to put strong threads in plastic enclosures. Fasteners could be foregone altogether by designing clips into the housing but would greatly complicate the molding process and in turn increase production costs.