These are the most common plastic materials for injection molding: acrylic (PMMA) acrylonitrile butadiene styrene (ABS) nylon (polyamide, PA) An injection molding machine consists of 3 main parts: the injection unit, the mold - the heart of the whole process - and the clamping/ejector unit. In this section, we examine the purpose of each of these systems and how their basic operation mechanics affect the end-result of the Injection molding process.