Custom injection molding is a process performed at many injection molding companies, it is a name for any injection molding project that is customized or changed to fit a customer’s needs. This could consist of developing a design for a new invention, changing an old design, or simply updating a color or plastic type of a common product. Custom injection molding is often used by individual inventors with new products that they want to sell to a large audience, or by big businesses who want to create something new for their consumer markets.
All custom injection molding jobs have to start with a design. Large businesses may already have their own designs and molds, in which case they would skip to later steps. But smaller businesses or individual inventors will likely need to create designs for their products. Digital designs can easily be made using 3D CAD software or other computer programs. These programs allow designers to see the exact dimensions of the future plastic product, and can give inventors a realistic model to make sure everything is correct before a custom injection mold is made. After the design is completed, an injection mold is built from metal to the size specifications given in the design. Injection molds may be crafted from aluminum, steel, nickel, or other blends of metals. These provide the sturdy framework for hundreds of thousands of plastic parts that could be made from the same mold. Before plastic injection molds can be filled to start producing parts, the right plastic polymer has to be chosen for the job. Thermoplastics, elastomers, and thermosets could be options for a product, and each could be available in different colors and textures. In cases of products that will use over molding, two or more types of plastic may be chosen. When the mold is ready and the correct polymers are in place, the first stage of the process is ready to begin by feeding dry plastic pellets into a hopper, which then feeds into a heating cylinder by using a hydraulic pump, motor and gears. Within the cylinder there are multiple heating zones which systematically increase the temperature of the material as it moves closer to the gate where it is injected into the tool. Each heating zone is constantly monitored and adjusted. The peak temperature of the plastic depends on the combination of materials being injected, but can reach as high as 725° F. With the help of a stationary and movable platen, the mold is held in place as a nozzle prepares to inject the molten plastic. Next, a clamp mechanism closes the mold halves. The action is performed by a motor rated by the maximum amount of force the machine is capable of creating. Then, the molten plastic is injected into the mold as the clamp keeps the mold closed. As the product solidifies and cools down, the finished product is ejected from the mold so another part can be produced. This cycle continues creating hundreds and in some cases thousands of parts per day until the order is filled. Once injection molded parts have been inspected for quality, they can be packaged and shipped, or assembled with other parts to make a final product.