Thursday, June 16, 2016

How The Process Of Overmolding Is Done

By Jerry Gray


There are many applications that require several materials to be combined together to make a single product. One of the processes through which several materials are combined to make a single item is referred to as overmolding. This process involves a substrate material over which overmold material or materials are applied to partially or fully cover it. Once the overmold material has been applied, it forms a single item with the substrate.

Substrates can take on a wide range of materials including metal, plastic, wood, glass, or ceramic. A substrate may also be a complete product in the form of electrical connectors, screws, threaded inserts, machined metal parts, or molded plastic parts. The substrate usually forms the first part of the final product, which is usually composed of chemically bonded and often mechanically interlocked materials.

The types of overmold materials are many and varied. However, in most cases, they are rubber and various forms of plastic. The process starts by making the plastic or rubber into small pellets and they adding suitable additives like fillers, colorants, and foaming agents. Compatibility issues in some overmold materials make it necessary to choose carefully. Metals always work perfectly with most overmold plastics.

Rubber and plastics have compatibility issues when the substrate is made of rubber or plastic of some form. As such, it is the responsibility of the manufacturer to provide a list of all the substrates that plastic or rubber they produce is compatible with and the extent to which this happens. Careful study and application of materials on the compatibility list is needed depending on how compatible the overmold is. The choice of an overmold material should ensure that the strongest chemical bond is achieved.

There are many applications for this activity in various industries and settings. Products of various types are made through the process. Screw drivers, laptops, handgrips, toothbrushes, casters, tools, and cans are examples of products made using the procedure. Various versions exist, including plastic over plastic, rubber over metal, rubber over plastic, and plastic over metal.

The process involves placing the substrate material or part of it into an injection molding tool. While inside the injection molding tool, the overmold materials shot around, onto, or into the substrate. Some time is allowed for the two to cure and solidify, forming a single joined product. To enhance the bond between the two materials, it is often advisable to ensure that there is some form of mechanical interlocking.

There are many different reasons why people engage in this process. The first reason is to enhance the aesthetics of a product. This process helps to break up color in a product by introducing another color. The final product can have multiple colors, which make it to look better. The second reason is for introducing soft or flexible areas in a rigid part. For instance, rubber parts may be introduced to a plastic or metal handle to make handling easier.

This process also helps to reduce or eliminate assembly line time. Instead of making separate parts and joining them later, one can just be overmolded onto the other and save time and resources. This activity also eliminates the need for using fasteners and adhesives on certain parts.




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