Real-time digital characterization of two-phase flow during expandable polystyrene (EPS) pattern molding for the lost foam casting process .

摘要

To better quantify process variability during injection molding of expandable polystyrene (EPS) patterns, an industry need exists for a measurement device to provide real-time feedback on the performance of EPS injection molding systems. One such application of EPS pattern making is the lost foam casting (LFC) process, where the end-quality of cast metal parts is highly dependent on the quality of EPS patterns.; This thesis explores various means of developing a non-contact flow measurement device to provide live feedback on out-of-spec injection fill gun operation to the factory technician. A method that utilizes acoustic standing waves within a rigid tube in-line with the fill gun supply hose was chosen for further refinement and testing.; Analytical and experimental methods were employed to validate the concept of this two-phase standing wave acoustic flow meter. High speed videography and video image analysis was used to record the flow of EPS beads through transparent tubing for the purpose of determining actual flow rates of beads under baseline conditions.; At an operating frequency of 3,000Hz, the standing wave flow meter was shown to under-predict acoustic amplitudes at a microphone downstream from the acoustic source when known volume fractions of EPS beads flowed through the tube. The analytically-predicted acoustic amplitudes were shown to be predominately based upon the bulk pressure within the tube and vastly less sensitive to flow velocities and solids volume fractions. While test data showed that bulk pressure alone is a good indicator of qualitative process performance, it was also demonstrated that measured attenuations of standing waves, with the effects of bulk pressure subtracted, can serve as an indicator of solids volume fraction within the fill gun supply hose.