A novel concept of microinjection molding system was designed and presented. The system was designed as a multimicroinjection module, which is matched with a vertical injection molding machine (IMM) and can be applied on commercial IMMs. A planetary gear pump was integrated in this system to complete the multi microinjection molding (M mu IM). The module is fixed between the stationary platen and the mold of IMM. The plasticizing unit of the IMM provides the melt and initial pressure for the multi microinjection molding system. With this system, a commercial IMM could be upgraded to a precise microinjection machine and has the capability of precise metering for the microinjection molding. Melt flowing behavior was predicted through the 3D injection molding simulation and experiments were carried out to testify the performance of the M mu IM. The injection molding performance was evaluated and the results revealed that the M mu IM system could effectively realize the microinjection molding. POLYM. ENG. SCI., 2012. (C) 2012 Society of Plastics Engineers