Plastic Welding Process Signature

This paper describes a method developed to control the ultrasonic welding quality applied on fuel rails of internal combustion engines. This method consists in monitoring some physical phenomena involved in the welding process, as vibration amplitude, weld energy and process duration. Based in statistical analyses, durability and thermal ageing tests performed with a great population of manufactured parts, it was possible to classify some welding parameters and build a real time filter, able to segregate poor quality parts in less than one second, right after process has finished. In this way, it is possible to eliminate nonconforming parts before performing the functional tests in the assembling line, reducing the process cycle time and saving resources. Based on the observation of rejected and approved parts on the functional tests, patterns could be created for the welding quality. Therefore, the measured parameters indicate the weld characteristics, corresponding to its signature, which can be compared to the established patterns. Figure 1 – Assembled mini fuel rail [6].