Double injection multi cavity mould overmolding for electrical tools

 
Double injection multi cavity mould overmolding for electrical tools
 
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Overmold tooling is classified as insert molding.

To help identify the difference in the two types of molding, think of injection molding as discrete components molded within a closed mold and insert molding as molding around an item inserted into the mold. During the insert molding process, the goal is to completely fill the mold cavity so that the cosmetic and functional requirements of the finished part are met, but at the same time not cause any uncontrolled molding material to exit the cavity and cause damage to the connector or cable inserted into the mold. It becomes a race to inject molding material into the cavity fast enough so it does not cool and cause restriction and then stop it before it flashes (escapes) at the connector or cable openings in the mold.

The key to overmold tooling is not just the mold tool that achieves the desired shape, but the integration of proper cable preparation and connector termination to provide a finished part that meets the quality and cost requirements. If the approach to the design is fragmented, in other words designed to satisfy the electrical requirements without regard for the mechanical requirements of the overmolding process, the finished part typically will be a problem.

Two basic types of injection molding machines are used in the overmolding industry : horizontal injection and vertical injection. Each machine type requires a different mold design and may affect the achieved output of the machine.

Overmold Tooling Design

The most common problems in overmolded cable assemblies center around overmolding approaches that limit the molding and assembly process parameters such that producing an acceptable range of parts is difficult. This is where the approach to overmold tooling design comes together. It is important to integrate the cable assembly process, tooling design and injection molding process. Too often, these functions are segregated and the end result is parts that do not work. The design of overmold tooling that facilitates interchangeable sections, and therefore modular molds, is often a great help in faster response to molding issues and lower tooling costs overall.

The familiar cry of "the molds don't work" often is the result of incomplete design of the overmold tooling relative to the cable assembly process, and utilizing a customer design that combines components, materials and processes that are inherently incompatible. Just as successful cable assemblies begin with good crimps, successful overmolded parts start with good mechanical stability between the components being molded. Once there is mechanical stability, the opportunity to focus on achieving optimum output from the design can be developed. Here, the combination of cavity design and part loading helps to determine the right configuration. Develop a multifaceted design team with a working knowledge of cable assembly and termination, overmold tooling design and injection molding processes. Approach the tooling equation from a less is better approach, and look at the total cost, including tooling, projected over the life of the part.