Injection molding is defined as a cyclic process for producing identical products from a mold and it is the most widely used polymer processing operation. The main advantage of this process is the capacity of repetitively fabricating parts. Certain challenges face this process in order to get a defect free product. The control of the cavity pressure is important for maintaining the quality of the plastic product. The common practice in industry is to have a fixed value for the pressure during the filling phase and also during the packing phase of the process. This may lead to the introduction of defects in the final product. This paper presents a mathematical model and experimental verification of a strategy to control the cavity pressure profile during the filling and the packing phases to minimize the flow marks, warpage and shrinkage for an ABS injection molded product. For the packing phase, the efficient frontier method is used to obtain the optimum pressure for minimizing the combination effect between the warpage and the shrinkage. This may be used as a tool for weighing the behavior of these two defects with the variation of the packing pressure. The results showed the effectiveness of the mathematical model used for predicting the filling and pressures to minimize the investigated defects.