Abstract
The precise measurement of three dimensional shrinkage at different locations within molded parts is seldom reported. In this research, we compared the measured shrinkage (relating the difference between the dimensions of the metal mold and the resultant molded plastic parts) with calculations based on PVT measurements for parts made from AS and ABS resins. With increasing packing pressure, the shrinkage was minimized in the normal direction (ND) more than in the melt flow (MF) and transverse (TD) directions. The ND shrinkage was proportional to the volume shrinkage, while those of the other directions were proportional to less than the 1/3 power of volume shrinkage. The TD shrinkage was larger than the MD shrinkage. With increasing packing pressure, the gate seal time increased for ABS, but hardly changed for AS. The molecular orientation, obtained from birefringence measurements, increased with packing pressure.
