Machine Design magazine recently published a good article regarding the different installation methods for threaded inserts in plastic parts. These inserts are commonly used to create stronger threads for attaching fasteners that would strip out of the plastic material. Installed correctly, they can provide significant resistance to both torsional and axial forces.

Threaded Insert

Threaded insert designed for heat installation

Installation is performed by melting the plastic and pressing the inserts, which can be accomplished through ultrasonic vibration or heating the insert itself. Heating is certainly easier for prototyping, but it can also provide a stronger bond. The article compares the two methods and details some of the pros and cons of each.

They don’t discuss insert molding, which is applying the insert directly into the mold of the plastic part. I imagine that is probably the strongest bond due to the high temperatures and pressures, but I don’t have data.

Which installation methods do you prefer?