Two shot molding is a variation of injection molding that allows for the use of multiple different materials within one product. This can provide manufacturers with many design benefits and eliminate the need for extra steps such as joining parts together with glue. In addition, it can reduce production costs and make products more durable. The process is relatively simple and involves injecting a first plastic resin into the mold, then inserting a second material that will bond with it. This can be used with a variety of materials such as thermoplastic elastomers (TPEs or TPUs) and rigid plastics like PP, PE or ABS.
A primary benefit of two shot molding is that it can significantly cut manufacturing time. Because the process can be done in a single cycle, it is much faster than using an injection mold that requires two separate cycles to complete each step. This can save on both labor and raw material costs. It also makes the process more cost-effective when producing high volumes of a particular part, because it can be run at an efficient rate.
The process can also be used to produce a wider range of products. It is great for creating hard and soft surfaces, as well as for adding color and texture to the final product. It is also ideal for making products that will be exposed to water or harsh chemicals. For example, it can be used to create plastic toys that feature both rigid base areas and softer rubber seals, or for making hard-wearing toothbrushes with a choice of colors and textures.
Another advantage of two-shot injection molding is that it can be used to create complex shapes. This is because the process allows for a greater degree of design freedom, allowing for features such as holes and undercuts to be molded into the finished product. Injection molding professionals must be aware of the fact that not all types of materials bond well with each other, and so must test the adhesion combinations to ensure a good result. If the results are not satisfactory, other methods of ensuring a strong bond can be used such as inserts or shoulders.
During the 2 shot molding process, the substrate is made from a plastic resin, and then a second layer of plastic or elastomer is injected to form the overmold. The choice of the type of plastic for the substrate is important, as it will determine what kind of overmold can be molded around it. The choice of the second material will depend on its thermal properties and whether it can melt at a lower temperature than the substrate. If the melting point of the second material is too low, then it will merely stick to the substrate rather than adhere properly to it.
The key to successfully implementing this type of molding is the choice of a highly capable and experienced injection molding manufacturer who will be able to ensure that all the requirements for the product are met. It is also essential that the process be carefully planned from the outset, in order to avoid unforeseen problems. This is especially true when using complex molds with a wide variety of cavities, or where there is a requirement for both rigid and flexible elements.