Fully automated injection molding machines for producing a number of molded plastic products consecutively from a plastic predecessor have already been developed and put into commercial utility. While these machines minimize the operator's intervention over repetitive molding cycles, the qualities and reproducibility of their molded products remain not entirely satisfactory. Thus, unqualified or defective products unavoidably develop which are most often comparable in proportion with products of a desired quality. The unqualified products are characterized by dimensional inaccuracy and the formation of microvoids and/or internal cracks. It has now been observed that these defects tend to develop a lack of proper control and arrangement in the conventional injection molding system.