Although injection molding and ultrasonic welding are both well known and documented processes, the interplay of the two oftentimes is not understood. Hopefully, by discussing problems and solutions in this interplay, this article may aid those who produce assemblies that are ultrasonically welded.
Ultrasonic welding is a common method of assembly due to its accuracy, repeatability, low cycle times, energy efficiency, and low relative costs. However, the success of the process is strongly dependent upon the input of well-molded parts. Both the molding process and the design process have direct influences upon the success of the ultrasonic process. Understanding the interdependency of the design, molding, and welding processes is imperative to be successful in this segment of the industry.
Much has been written about proper design techniques for plastic parts, and those responsible for design should assure they have the technical knowledge before designing a thermoplastic part to be ultrasonically welded. The influences of good plastic part design can be shown to also affect the other joining processes, e.g. hot plate, laser, and vibration welding.