Two shot molding and over molding are two popular injection molding techniques. They both have advantages and disadvantages. Which is best for you will depend on your manufacturing needs.
What is Two Shot Molding
Two shot molding an injection molding process where two different materials are injected into the same mold. These materials may be the same base material but different colors, or completely different materials. The machine will inject the first material, then another nozzle will inject the second material. The materials bond together, and the entire process is completed in one cycle.
Advantages of Two Shot Molding
Two shot molding produces parts in one cycle, which can streamline the manufacturing process. The less times a part is handled, the less room there is for human error. It also improves quality by reducing steps and creating a secure bond between the different materials. This also decreases assembly time and lowers unit costs.
What is Insert Over Molding
Over molding is a way of adding another layer to an existing part. Over molding is often used to create special features, prototypes, sub parts, or to change the color or texture of a part. The original part is placed into the mold, then injection molding is used to create the over mold. The over mold bonds to the existing piece, also known as the substrate, making them one part.
Advantages of Over Molding
Over molding offers more flexibility. You can over mold over different materials, including metal and plastics. Nearly any plastic can be over molded onto a metal piece, but not all plastics are compatible. Over molding offers versatility and can create a stronger part.
Two Shot Over Molding
In some cases, these two processes essentially combine to create two shot over molding. With two shot over molding, the first part is injection molded, then another layer is injected molded over it. This usually occurs in the same cycle. This allows you to produce complex parts with high efficiency and quality.
Two Shot Injection Molding Advantages
Two shot over molding gives you the maximum flexibility in regard to design. You are limited to using injection molding materials, but if you are creating a part solely with injection molding that requires different layers, this is certainly the best process. You reduce the number of steps needed and the amount of handling of the part, which increases productivity and quality.
Two shot injection molding is an excellent manufacturing technique with many advantages over other processes.