Injection Molding Process

The plastic injection molding process is a manufacturing technique used to produce molded plastic components. Manufacturers worldwide utilize this technique to mass-produce all kinds of goods, from cell phone cases to garbage cans. The parts are created by inserting plastic materials melted by heat into a mold, then cooling the product and waiting for it to solidify. The mold preparation is one of the most critical parts of the process and must be perfected by a designer before production begins. 

Manufacturers use the molding process to produce a high quantity of identical parts. This method is also suitable for creating complex, irregular shapes, and components. Special Tool & Engineering provides a total solution system for injection mold clients, providing expert service during the entire process from product design to prototyping and final production. Here is everything you need to know about the injection molding process. 

Product Design 

Product design is the first step in the injection molding process and is one of the most critical steps. Completing a comprehensive design and evaluation process allows mistakes to be identified and fixed early in the process. Besides identifying errors, the goals for the product design phase include determining function, manufacturability, assembly, and aesthetics. Producing an efficient design takes a great deal of trial and error and creativity. Design plans are often completed using computer-aided design software. 

Mold Design 

The mold design process is one of the most crucial parts of the injection molding process. A mold is a hollow metal block used as housing for molten plastic. Molds are constructed to resemble the component or part to be manufactured precisely. Molten plastic is injected into the mold, which will take on the shape of the mold once cooled. During the molding process, the plastic materials flow through a spruce into the mold, filling cavities by using runners and gates. After the mold design has been tested and evaluated, it is prepared for injection mold manufacturing. Molds are commonly made from various metal types, including pre-hardened steels, aluminum, and Beryllium-Copper alloy. 


After the completion of the product and mold design processes, the manufacturing process begins. The injection molding process requires several steps. These steps include: 

  • Thermostat or thermoplastic material in granular form is fed through a hopper, a sizeable cone-shaped container used in industrial manufacturing. The material is then transferred into a heating barrel.
  • The thermoplastic material is heated to a specific temperature, pushed through a large screw, and urged through the gate and into the injection mold.
  • Once the mold is packed with molten plastic, a screw applies a predetermined amount of pressure to the material while it cools.
  • After the material cools, the screw is extracted, and the part is removed from the mold. 

The injection molding process described above is repeated as often as necessary, creating hundreds of identical parts in form and function. 


Prototype molds are designed to be temporary versions, which can be used as part of a phased approach to identify errors and perfect features before building a final mold. Unlike the final mold, prototypes often use inexpensive materials such as aluminum. A small number of parts are produced during the prototyping phase, which can be used for testing purposes. Some manufacturers also prototype molds to satisfy low-cost, low-quantity production runs. 


After designs have been perfected, prototypes made, and errors fixed, the production phase is the final stage in the injection molding process. Special Tool & Engineering has the personnel and equipment required to satisfy high-quality orders quickly. We are committed to delivering high-quality parts that are not only uniform but consistent with requirements. 

Special Tool & Engineering is a full-service supplier offering engineering, design, and complete tool manufacturing services for various industrial applications.

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