An injection molding quality control system which seeks to ensure greater accuracy and consistency in parts, more specifically more accurate and consistent part weight, utilizes measured part weight to adjust mold separation to better achieve a desired part weight. The mold separation is controlled via both a cycle-to-cycle adjustment in switchover point (preferably based on injected mass within the cavity), and within-cycle adjustment of holding pressure. The system can result in superior accuracy and consistency in molded parts in both the long term (i.e., over many cycles) and in the short term (from cycle to cycle).