Assembly Considerations
Welding of injection molded thermoplastics parts involves softening the surfaces being welded by heat and maintaining intimate contact between them during the re-solidification of the softened material. The means of providing heat energy at the welding interface varies from technique to technique. In hot plate welding, the heating source comes in direct contact with the surfaces being welded. In ultrasonic, vibration, and spin welding techniques, the contact with the energy source is indirect. Mechanical energy is transmitted through the part to produce frictional heat at the interface. Induction and laser welding processes transmit energy to the welding surfaces remotely without any direct contact with the surfaces or the components being welded. Most thermoplastics can be welded using one or more of the aforementioned techniques. Selection of the appropriate technique for an application is determined by factors such as component geometry and size, material type, aesthetics, joint strength, tolerance required, and process economics. Unlike mechanical fastening methods, welding of thermoplastics is suited for one-time assembly only. Even though induction welding can be used to disassemble the components, it is generally used for reclaiming the captured parts in the assembly. Reassembling the same components is generally cumbersome and cost prohibitive. Additives such as fillers, lubricants, mold-release agents, flame retardants, pigment, and plasticizers affect the weldability of thermoplastics regardless of the welding method. It is important to decide on the welding method early in the design phase so that the components can be designed to suit the welding method. Refer to our Joining Techniques Design Guide for more information. |