Overmolding is a manufacturing process that combines multiple materials into a single part. It’s often used to add a soft, non-slip grip to metal products or create an easy-to-grip surface on plastic ones. It can also be a great way to reduce assembly time on the production line by eliminating the need for glues and fasteners. However, there are many things to consider before you use this method to make sure your final product will be a success.
The overmolding process starts with a thermoplastic injection of the base part or parts. Once that is molded, a second shot of another material is then injected in or around it (generally a rubber-like resin like TPE). As the overmolding process cools, the two materials bond together, creating a unified part with the desired texture and feel. The bond can be either mechanical or chemical depending on the overmolding design and materials chosen.
In order to ensure a good bond between the overmolded material and the substrate, it is important to follow some basic design principles. A uniform wall thickness is preferred to minimize cycle times and to achieve a consistent finish on the overmold. Proper draft angles are also essential to ensure that the overmolding material can be inserted into the mold properly. The transition between the wall thicknesses should be gradual to avoid gaps or air pockets that could weaken the overmolding.
There are a variety of different materials that can be used for overmolding, and the most compatible pairs of materials depend on both the type of overmolding you are using and the desired properties of your final product. For example, a rubber-like TPU material will form a strong chemical bond with ABS, polycarbonate, and PBT Valox (a type of polybutylene). Santoprene TPV is more restrictive, bonding with only some polypropylenes but not others. It is best to work with a professional overmolding service who has close relationships with material suppliers and can help you determine the most appropriate combinations of materials for your particular project.
Overmolding can provide many advantages to your finished product, including increased durability and improved ergonomics. It can also help to save on production costs by eliminating the need for additional steps in the production line, such as injection molding and assembly. It can even be a great solution for complex assembly designs that would otherwise require the assembling of several separate components.
In addition, overmolding can be an excellent choice for improving safety when using a product by adding a layer of soft, non-slip grip to hard metal tools or electronics. It can also improve the ergonomics of a product by allowing it to be held more comfortably, and it can even absorb shock or vibrations.