Overmolding is a manufacturing process that involves molding two distinct materials into one unified product. This specialized technique can be used to add flexibility to rigid parts and products or can serve to soften the texture of hard plastic or metal items. It is especially useful in creating durable, attractive, and ergonomically designed products that will appeal to consumers. It also eliminates the need for assembly, which saves time and money during production.
The overmolding process starts with the creation of a substrate. This can be made out of virtually any plastic material, and it must be capable of surviving the injection molding process. The second part of the overmolding process involves adding a rubber-like material to the base. This is generally accomplished by injecting a new shot of overmolding material in, on, or around the substrate. When the overmolding material is cooled, a chemical bond forms that creates a strong and secure connection between the two parts.
While the resulting overmolded product is very strong and sturdy, it is not without its limitations. In some cases, it may be necessary to use mechanical interlocks in addition to the chemical bonds formed by the overmolding process. The primary reason for this is that the ideal temperature range in which the overmold and substrate can bond together varies. If these temperatures are too extreme, the bond will weaken. In these instances, mechanical interlocks will help prevent the materials from separating and improving the longevity of the overmolded product.
Using elastomers like rubber or polyurethane over hard plastic or metal items is not only more pleasant for the user, but it is also a lot safer as well. The human hand is not suited to the rough textures of metal and hard plastic, which can cause pain or injuries if handled improperly. Overmolding can solve this problem by introducing a soft coating to the items, making them more comfortable and usable. Examples of this include using elastomers over metal tools, medical devices, or power cords.
Overmolding can also make cable assemblies more attractive, as the molded over portion of the product can be customized to match or complement the color or texture of the wires inside. This is particularly appealing to customers who prefer a cleaner, less industrial look for their electrical components. Moreover, the added flexibility can provide better protection from environmental factors such as humidity and water, which is important for many applications like waterproof cords for electronics.
Overmolding can be used in a wide variety of products, from toothbrushes to bathroom fixtures. The most common application is in the field of hardware tools, where overmolding allows manufacturers to produce a single product that will meet the requirements of a particular use case. These tools might be as simple as blades or pocket knives or as complex as pliers, wrenches, hammers, or tape measures. Overmolding is also often used in the creation of consumer electronics like mobile phones, tablets, and laptops.