Over-Molding, Insert-Molding, Structural Foam and Gas Assist.

Distinguised solutions in plastic engineering.


Over-molding continues to be an attractive option because of the functional flexibility it affords product designer and engineers. Using two separate plastic injection molds on the plastic injection molding press, two materials are bonded together during the plastic over-molding process to form plastic parts and components with unique visual or ergonomic appeal, such as handles or knobs. Custom plastic overmolding is also used to strengthen, protect and improve a part or end product, while reducing cost, labor and materials.

Plastic overmolding offers numerous advantages, including:

  • Reduced secondary operation, assembly and labor costs (molded as one assembly)
  • Eliminates bonding step in the manufacturing process (improved component reliability)
  • Plastic overmolded components ensure proper alignment and prevents loosening
  • Plastic resin can provide improved resistance to vibration and shock
  • Improved part strength and structure
  • Enhanced design flexibility and multi-material components

  • More often than not, the applications we see require a soft (elastomeric) skin bonded to a rigid substrate in products requiring a soft feel, vibration dampening or product protection. Over-molding has been widely used in higher volume applications where the cost of the specialized tooling, automation and molding equipment can be easily amortized.

    In addition to overmolding, we also offer insert-molding, structural foam and gas assist. Gas assist injection molding is the most effective method of applying pressure to an injection molded part, where the nominal wall cannot be maintained. It is also ideal for thick walled designs such as handles, as this process allows for pressure to be maintained during the cooling cycle. Gas assist injection molding is a low pressure process that utilizes Nitrogen, which reduces the clamp tonnage required for molding.

    Structural foam molding (SFM) is similar to traditional injection molding whereas heated thermoplastics are injected into precision-made tools. The key difference between structural foam molding and injection molding is SFM is capable of producing much larger sized parts with lower molding pressures.

    PTA Plastics stands out as a producer of over-molded and structural parts in eye-catching color and surface combinations. Finished products are seamless and inseparable with dynamic visual appeal. More importantly, they have the advantage of being produced fast, right and on time.