Over Moulding

What is Over Moulding?

Over Moulding is the process of adding an additional layer of material over an already existing piece or part. For example the steel shaft of a screwdriver is overmoulded with plastic to form the handle. The base component is placed in the injection mould tool and hot molten plastic fills the area around the inserted part, the result is an assembled product.


Plastic overmoulding offers numerous advantages, including:

  • Reduced secondary operation, assembly and labor costs (Moulded as one assembly)
  • Eliminates bonding step in the manufacturing process (Improved component reliability)
  • Plastic overmoulded components ensure proper alignment, prevents loosening and the plastic resin can provide improved resistance to vibration and shock
  • Improved part strength and structure
  • Enhanced design flexibility and multi-material components (Custom plastic overmoulding allows for production of parts moulded of multiple thermoplastic materials)


Custom overmoulded plastics provide competitive advantages in a wide range of applications, including:

  • Medical devices and instruments
  • Parts with soft grip handles
  • Knobs for appliances, controls and assemblies
  • Encapsulated electronic devices and electrical components
  • Window reveal moldings

Proper mold design and construction and material selection are important in custom plastic overmoulding to maintain part tolerances and tooling reliability. In addition, PMI often employs robotic automation in the plastic overmoulding process for fast and precise placement of inserts.

With our many years of custom plastic overmoulding experience, in-house engineering, mold design and building, and focus on innovative solutions, PMI has partnered with many customers to produce overmoulded plastic parts and components that reduce labor and assembly costs, while improving the quality, reliability and integrity of the end product.

Whether re-engineering existing products or developing new products, carefully engineered custom overmoulded plastic parts and components can eliminate the need for a variety of secondary operations such as sonic welding, bonding, gasketing and assembly, saving time and money.