Ultrasonic investigations of the thermoplastics injection moulding process

The ultrasonic measuring technique constitutes an interesting possibility for process analysts to gain a deeper understanding of a particular process. During initial tests for thermoplastic compact injection moulding it was found that the ultrasonic signal can sometimes supply information for much longer than, for example, pressure signals. It was also found that a relationship exists between the signal and the shrinkage process of the moulded part. The point when the signal ceases coincides with the time the moulded parts become detached from the cavity wall during the cooling phase. The measuring method reflects all variations in the process conditions very sensitively indeed.