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Many factors influence SMC cure behavior including mold temperature, SMC temperature, formulation, and aging. Although most of these factors are controlled to some extent, small uncontrollable variations will always cause some degree of fluctuation in cure behavior. The recent development of in- mold cure sensors allows the analysis and control of these variations from part to part and from batch to batch. In this study, SMC molding was monitored for thousands of parts and analyzed using Statistical Process Control (SPC) methods. The standard deviation in part to part cure times was found to be on the order of 1 to 5 seconds depending on factory conditions. A strong correlation of cure time with mold surface temperature was found, however, other uncontrolled parameters were found to have an additional significant influence. The cure sensor and monitoring system was connected to the press controller thus implementing closed loop control.

Implantable microdielectric sensors are routinely used to monitor the cure of thermosetting polymers. Until recently, the cure monitoring of Reaction Injection Molding (RIM) processes has been difficult due to the short reaction times of RIM materials in relation to the time required to make the dielectric measurements. New high-speed hardware and software (8.3 milliseconds per measurement) has been developed for the dielectric cure monitoring of RIM systems. Dielectric curing data collected with both the existing and new hardware and software are discussed.