Overmolding

How Does Injection Overmolding Work? 

Injection overmolding is the technology of layering materials on a part to provide strength, longevity, or aesthetic benefit. Like complex plastic injection molding, injection overmolding is completely according to customer’s needs, as customized products are easy to manufacture and design at the mould tool design stage. It is very popular China precision machining technique because it is fast and cheap to mass produce the parts with high quality.

This injection mould tool leaves room to inject the second material. When the second material is injected into the mold, the two components are cured to create the final overmolded product. However, if an error occurs at any stage, the entire process has to be redone.

Injection overmolding is the technology of layering materials on a part to provide strength, longevity, or aesthetic benefit. Like plastic injection molding, injection overmolding is completely according to customer’s needs, as customized products are easy to manufacture and design at the mould tool design stage. It is very popular technique because it is fast and cheap to mass produce the parts with high quality.

What Are Benefits of Injection Overmoling Services?

Plastic injection overmolding helps reduce manufacturing time by molding its second part directly onto the original part, instead of having to manufacture two parts completely separately and then assemble them together. Other benefits of plastic injection overmolding are as following:

• Improved grip and ergonomics

  
  

• provides electrical insulation

  
  

• Forms a waterproof seal

  
  

• Sound absorption/vibration suppression

Overmolding Design Guidelines

Our basic guidelines to overmolding includes key design considerations that help improve part manufacturability, improve appearance, and reduce overall production time.

Maximum Dimensions

Overmolding Materials

Most Common Materials for Overmolding:

• ABS-Acrylonitrile Butadiene Styrene

• PE-Polyethylene

• PP-Polypropylene

• PC-Polycarbonate

• Other Common Supported Materials:

• Nylon (PA 6, PA66, PA 12)

• "Polycarbonate/Acrylonitrile Butadiene Styrene(PC/ABS)"

• Polyurethane (PU)

• Polymethyl Methacrylate (PMMA/Acrylic)

• High Density Polyethylene (HDPE)

• Low Density Polyethylene (LDPE)

• Polystyrene (PS)

• POM (Acetal/Delrin)

• Polyetherimide (PEI)

• Polysulfone (PSU)

• Thermoplastic Elastomer (TPE)

Using silicone as an overmolding material can limit the height, confining deeper areas to smaller profiles. Minimum part volume is 40.98 cubic mm. A machining tolerance of ±0.08 mm can be maintained by using a substrate mold. This includes a resin tolerance of 0.002mm/mm. For thermoplastic overmolding, the tolerance is the same as for the base mold, but if the overmolding is LSR, the tolerance is 0.025mm.

Injection Overmolding Material Compatibility And Mechanical Bonding

Chemical bonding between overmolded materials is possible, but material compatibility must be considered to achieve the required bond strength. If adhesion is important to your application, incorporating a suitable mechanical bond is highly recommended. Undercuts are a good example of mechanical bonds.