The 2 shot molding process is used for manufacturing a variety of plastic products. It allows the combination of multiple materials in one production run to produce a product with enhanced functionality, improved ergonomics and added aesthetic appeal. This multi-material injection molding technique can be effective in producing a wide range of items, from toothbrush handles to complex medical equipment. It can also be used for items that require a hard and soft touch material, or a combination of different colors. It is particularly suited for plastic electronic devices with LED lighting and translucent inserts that can help spread or color the light. Two-shot molded items often improve hygiene as they have fewer crevices where sub-parts interface.
The two-shot injection molding process, sometimes referred to as double-shot, dual-shot, or multi-shot molding, is an in-mold assembly (Im) process in which multiple layers of different plastics are injected into the same mold in one machining cycle. This can be done in one of two ways, either by using a single tool that produces both the substrate parts and the over-molded components, or by using a separate injection molding machine to produce the base and then transferring it into the second injection mold that over-molds the product.
During the first phase of the two-shot injection molding process, a shot of the primary plastic resin is injected into the mold to form the substrate. This is the part that will support other layers of different plastics, and may even incorporate metal or electronics into its design. Once the substrate has solidified and cooled, it is transferred to a second injection molding machine, which fires a second shot of a different plastic over the substrate.
A key requirement for successful two-shot injection molding is a good understanding of the plastics chemistry involved. Different polymers bond differently, and a compatibility chart should be consulted to ensure that the desired results can be achieved. Additionally, careful attention should be given to the design of the injection molding machine to ensure that the pressure of the second shot will not deform or compress the first shot substrate.
There are several types of injection molding machines that can be used for two-shot injection molding, including a traditional stationary table and rotary platen systems. The rotary platen system is especially useful for large volume production runs, as it allows the two-shot process to be carried out with the same speed and pressure as other injection molding processes. It also reduces the amount of labor required to transfer the substrate between the two stages, and the number of steps in the overall injection molding process. This can lead to cost savings for the manufacturer, and increased efficiency and quality for the end customer. The rotary system can be set up with either a vertical or horizontal platen. The choice will depend on the type of mold being produced, as some materials are better suited to each configuration. In either case, the two-shot process can be a valuable addition to any company’s manufacturing capabilities.