Insert molding and over-molding

Insert molding and over-molding are special production processes where plastic is injected over another material such as another plastic, metal or a printed circuit board. It makes the assembling process faster and more cost-effective than gluing, for instance. As a result it is widely used in plastic parts design. Next, this manufacturing process is also used to make water and air tight assemblies for electronics and electric cables.

Over-molding is categorized into 3 types: insert molding, double shot molding and co-injection molding.

Insert molding:

Insert molding is a process that requires an insert typically made of metal. Next, This insert has to be placed in the tool to let the plastic flow around it. Encapsulating the insert with plastic creates a single molded plastic piece that’s generally stronger than one created using secondary assembly.

Insert molding can be done through manual insert loading. In addition this is generally a more cost-effective way to manufacture low-volume applications or complex parts. However automated insert molding is a better choice for part consistency. It minimizes human error, improves efficiencies, and ensures optimal cycle times.

Other key cost and design benefits of insert molding include:

  • Elimination of secondary assembly operations such as snap fits, gluing, and the use of screws or fasteners.
  • Reduction in the number of required parts and streamlined logistics around part tracking, shipping and supplier consolidation.
  • Integration of design features not which are not possible by using a single material.

Insert molding is appropriate for a wide range of applications. Thus it is used forcouplings, knobs with threaded fasteners and filters. As well as complex electrical components and specific solutions Davantech developed for its customers.

Over-molding or Two-shot molding:

Overmolding is a process that results in a seamless combination of multiple materials into a single part or product. In addition it typically includes a rigid plastic base component overlaid with a soft thermoplastic elastomer. Usually this soft plastic is TPE or TPR. Overmolding adds value in several ways. In addition, it lowers production costs. As a result the advantages of using overmolding are numerous:

  • It results in a soft anti slip grip that prevents dropping and at the same time it functions as a shock barrier to maximize product life.
  • We create visually attractive surfaces and branded color schemes that increase shelf appeal. In this way a nicer design provides a competitive advantage.
  • Over-molding reduces the number of required manufacturing steps and associated costs.

Overmolding is extremely versatile. Common household items such as hand tools, toothbrushes and razors may have overmolded handles for better grip. In addition overmolding may also be used to bond gaskets or seals to a plastic cover. But also in the manufacturing of electric cables it is used to in-mold metal contacts and gromets.

Insert molding and overmolding are somewhat similar yet distinctly different forms of multi-material injection molding. IT is important to talk to experts like Davantech in advance. In this ways your product design will have the best outcome for manufacturing your product in a cost efficient way.

Co-injection molding:

In co-injection molding we inject the hard substrate and the elastomer into the same mold. Therefore compatibility between materials is essential and it must be carefully controlled.

Co-Injection is very expensive and difficult to control. It is used least comparing with the other 2 method. The hard and soft substrates are in a fully molten state. Therefore it provides the best bonding between soft and hard parts, the molded parts quality is also the best.

At Davantech we control this production technique very well. Here is what we can do for you:

  • We do injection of plastic around a metal contact to make connectors or terminal blocks.
  • Injection of soft plastic around an electric cable to make cable splits, connectors and grommets.
  • We inject plastic around printed circuit boards to make encapsulated or watertight electronics.
  • Overmolding of soft or hard plastic over metal parts to make a solid assembly between metal and plastic.

Overmolding of electrical cables and metal contacts (connectors).

During production of electrical cables and connectors we encapsulate the wires and soldered or shrinked metal contacts with plastic.

This plastic can be softer TPE or TPR. However we also inject PP and other hard plastics around connector pins as well.

We us our vertical injection machines of 20, 25 and 45 tons for this injection molding process.

overmolding of connectors, electric cables

testing of electrical cables

Testing of electrical cables

All electric cables are tested one by one before packaging. We strive to zero defects !


Over molding of printed circuits

Even printed circuit boards with electronic components will be over molded. This to ensure water tightness.

Overmolded PCB

overmolding of metal can be a good solution for mechanical engineering

Over molding of plastic on metal

Some metal and plastic parts require a solid assembling. Therefore it can be a benefit to for a plastic shape onto a metal part. Soft as well as hard plastic can be molded. This technique will ensure a tolerance free assembly where the 2 components cant move or rotate.