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Overmolding is to mold a rubber piece onto another piece of hard plastic. It combines plastics with materials like rubber to form a completed part with a two-step process.

Overmolding can be used to enhance many features of product designs, including:

  • Safety
    1. Improved grip in dry and wet environments
    2. Vibration damping
  • Ergonomics
    1. Increase in comfort level.
  • Product functionality
    1. Water-resistant seal
    2. Sound absorption
    3. Electrical insulation

Your Best Overmolding Manufacturer in China


Overmolding is a process of adding an additional layer of material over an already existing piece or part.

It uses a pre-formed plastic part placed into a mold and then injects the second material into the mold to cover the second material all or part of the first part.

  • Tooling costs lower than with multi-shot processing
  • Conventional single-shot IM machines can be used

Overmolding in Five-Star is regularly used to manufacture parts, sub-sections of parts, and for prototype development.

It can be added to change the surface of a piece or product by adding texture, color, and incorporating necessary functionality components.

Overmolding can enhance design flexibility and multi-material components. Besides, it can reduce secondary operations, assembly and labor costs.

Compare with other injection molds, overmolding can improve part strength and structure, can save money and time by not having to schedule additional outside production.

What’s more, overmolding doesn’t require additional adhesive.


Overmolding could also be categorized into 3 types: insert molding, double shot molding, co-injection molding.

Insert molding is the most commonly used and economical way to mold soft elastomers to rigid plastics.

The hard segment has been separated into tools in advance, and then eject the soft materials in.

Double shot molding is also called 2K injection molding, it requires two injection molding machines.

The hard segment is injected first and then led by the elastomeric mold to the injection molding machine, finished the process of the hard segment into the elastomer injection, which can achieve a stable mechanical bond.

Last but not least, co-injection molding is to eject the hard substrate and the elastomer into the same mold, but it’s rather expensive and hard to control.

Contact our Five-Star Tooling professional team to learn more about your overmolding project, or other die-casting, precision components project.

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