An Experimental Investigation of Resin Flow Sensing During Molding Processes

Abstract

The present investigation focused on the need for sensing subsystems for the monitoring of resin flow dynamics during molding processes. Such subsystems, when combined with process parameter control, will produce intelligent manufacturing systems that could significantly improve manufacturing capabilities. A concise review of potential resin flow monitoring methodologies is included, and a detailed analysis of one particular sensing concept originally investigated at the U. S. Army Materials Technology Laboratory is presented. The concept is based on embedded electronic sensors, and during the present study a resin front monitoring system based on a modified version of this concept was developed. Electrically conductive wires were embedded orthogonally in a nonintersecting manner within mold cavities. Subsequent resin flow was sensed by monitoring the electrical characteristics of circuits which resulted during processing. A novel modification of circuitry was included to allow for the monitoring at multiple locations with a single electronic circuit. The net result of this modification was an improved response time of the overall sensing subsystem. The concept was verified experimentally through the performance of both one-dimensional (TD) and two-dimensional (2-D) experiments. The resin system utilized consisted of a mixture of epoxy resin (EPON 826) and a curing agent (MHHPA). The sensed flow front progression information was validated through controlled injection rate experimentation and flow visualization results obtained with transparent molds. It was concluded that the resin flow sensing subsystem could be applied to relatively slow molding processes. Positive and negative aspects related to the applicability of the sensing method to actual manufacturing processes are discussed.