One of the most common processes to produce a part with thermoplastic material is surely injection molding. The primary reason for this is the possibility to produce in a single shot with a short cycle time a part of desired shape. However, not only the high production rate but also high quality of the parts is a success factor of an industry. The quality of molded parts depends on the processing conditions and therefore on the thermo-mechanical histories experienced by the material during the processing. One of the most common quality issues for injection moldings is part shrinkage. In this work a series of injection molding tests with a general purpose Poly-Carbonate (PC) was conducted changing the holding pressure and time. Local measured pressure evolutions have been analyzed to estimate the local solidification histories and thus to obtain the local average solidification pressure. This parameter was already identified as a suitable parameter to describe the quality of the parts in terms of in-plane shrinkage. A procedure was developed to determine a master-curve that allows to monitor on line the quality of the molded part starting from the measured local pressure evolutions.