Online Monitoring of Flow Front Arrival by Ultrasonic Waves in an Injection Molding Process

Nondestructive ultrasonic test using Pulse-echo technique has been performed to online monitoring in plastic injection molding process of a cubic part. The received signal amplitudes versus the injection time have been saved as a diagram for each point on the outer interface between the melt plastic and the mold wall. Using the acquired diagrams, detachment process and the time of emerging air gaps which are formatted due to polymer shrinkage, have been online monitored. This information are required to investigate solidifying phase and also the cooling phase which have being gathered superior with using the conventional pressure sensors. Flow front arrival has been online monitored and the time of arrival of the melt polymer at each point has been determined. Thus the last point where the melt plastic reaches i.e. the position of the air venting openings has been obtained.