Alteratives to Fastners
Plastic parts and assemblies are becoming more common as engineers work to reduce costs and weight in their designs. But plastics often aren’t strong enough to support fasteners such as screws or bolts. Using screws to attach parts to plastic housings, for example, often ends with stripped threads, failed housings, and assemblies that fall apart. Forum
Plastics can offer two alternatives to get around these limitations. Both options provide a permanent and accurate placement of the insert.
Ultrasonic Insert Welding
High-frequency vibration coupled with a relatively small down force generates enough friction to melt the plastic around the insert during assembly into a predrilled or molded hole.
- Relatively fast for smaller insert sizes
- Machines can be easily adapted to a variety of insert sizes and shapes
- Ultrasonic welding machines can also be used to join plastic-to-plastic as well
- Metal inserts can be purchased generically or can be custom machined
- Ultrasonic insert installation is typically set-up for one insert per cycle
- Limitations on insert locations due to the ultrasonic horn accessibility.
As the insert is being pressed into the part, heat is transferred through the insert causing it to melt its way into the pre-drilled holes or molded pockets. The two most common insert materials are Brass and Aluminum due to their good thermal conductivity.
- Multiple inserts can be installed in one operation and at different planes
- Better performance over ultrasonic insertion due to a better plastic flow into retention features
- More options regarding insert location within part.
- Insertion into thin-walled parts which would be destroyed during ultrasonic installation.