In the present research, the authors investigated the lens manufacturing with the injection molding process by using the geometrical contour errors as the quality criterion. In order to produce functional injection-molded optical components, a special cavity mold was used to perform experimental testing for biconvex spherical lenses and numerical simulation was used to help during mimic of the process behavior. The approach was divided into validation step and optimization step. In the validation step, a reliable numerical model was designed to reproduce material features during filling and shrinkage, in order to correctly evaluate lens deflection. In the optimization step, the Grey Relational Component analysis coupled to the Taguchi Design was used to identify the optimal parameter set leading to the best values of lens total deflection, Peak-to-Valley and Root Mean Square between real and ideal lens surface geometry.