Real-time ultrasonic diagnostic technology for polymer injection molding processes

Integrated high-temperature (HT) ultrasonic sensors have been developed successfully by using piezoelectric bismuth titanate and lead zirconate titanate films HT ultrasonic transducers for real-time, non-destructive, and non-intrusive diagnosis of polymer injection molding (IM) processes. The HT ultrasonic sensors can be integrated onto the barrel and/or mold of IM machine, according to the customer's requirements. These sensors can be operated up to 400°C without cooling system and ultrasonic couplant, and can be miniaturized with sufficient signal strength and signal-to-noise ratio.The chosen IM processes are grouped to large- and small-scale 1M processes. The large-scale ones include conventional IM, co-injection molding (COIM), and fluid (gas/water) assisted injection molding (GAIM/WAIM). A filling incompleteness of 1 volume-% for IM of polycarbonate (PC) part, the core (PC) material movement and layers dimensions for COIM, the fluid motion, thickness and deformation of the hollowed high-density polyethylene (HDPE) part for GAIM/WAIM were diagnosed during processing by ultrasonic sensors and techniques developed.The small-scale ones include IM for microfluidic device (IMMF) and micromolding (MM). The optimization of holding pressure for producing a flat polymethyl methacrylate (PMMA) part (surface roughness < 5 mum) having micro structures for IMMF, estimation of temperature of polyacetal copolymer (POM) melt in the barrel and filler concentration of nylon 66 (PA66) mixed with polyhedral oligomeric silsesquioxanes (POSS) part in the mold for MM, and evaluation of thickness variation of molded alumina ceramic powder part for MM were demonstrated. The melting stages and quality of low-density polyethylene (LDPE) in the barrel has been successfully monitored using ultrasound. The important phenomena during melting processes, such as partially melting pellets, air bubbles, melting completeness, and effects of melting temperature and rotation speed have been diagnosed by ultrasonic signatures.These diagnostic results verify that the developed integrated HT ultrasonic sensors and techniques are capable of monitoring various IM processes to fabricate parts and products having complex formation, tiny size and micro structures, and evaluating the part quality in order to provide timely information for process optimization