Overmolding

Pilot runs, low-volume production, bridge tooling

Overmolding is a process where a single part is created using two or more different materials in combination.

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Advantages of Overmolding

Strength

Rubber-like TPEs/TPVs on the exterior of plastic parts can help the piece resist water or absorb sound. The TPE/TPV layer can also serve as electrical insulation.

Durability

Overmolding can help keep dust and water out of plastic components, making them last longer.

Efficiency

Overmolding can help add a second layer that can make grips more comfortable on any parts that people hold or grasp.

Overmolding Materials

Available rubber-like plastic varieties:

  • TPE
  • TPV

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Available flexible plastic varieties:

  • Low-Density Polyethylene (LDPE)
  • PC-ABS
  • PET
  • Polyethylene
  • Polystyrene

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Available rigid plastic varieties:

  • ABS
  • Acetal POM [Delrin]
  • Acrylic (PMMA)
  • High-Density Polyethylene (HDPE)
  • Nylon 6
  • Nylon 6/6
  • PBT
  • PC-PBT (Xenoy)
  • PEEK
  • PEI [Ultem]
  • PLA
  • Polycarbonate
  • Polypropylene
  • PPE-PS
  • PPS
  • PSU
  • PVC

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Overmolding Finishes

SPI A-1

Grade #3, 6000 Grit Diamond Buff

SPI A-2

Grade #6 3000 Grit Diamond Buff

SPI A-3

Grade #15 1200 Grit Diamond Buff

SPI B-1

600 Grit Paper. Typical Application: Medium polish parts.

SPI B-2

400 Grit Paper. Typical Application: Medium polish parts.

SPI B-3

20 Grit Paper. Typical Application: Medium- Low polish parts.

SPI C-1

600 Stone. Typical Application: Low polish parts.

SPI C-2

400 Stone. Typical Application: Low polish parts.

SPI C-3

320 Stone. Typical Application: Low polish parts.

SPI D-1

Dry Blast Glass Bead. Typical Application: Satin Finish

SPI D-2

Dry Blast #240 Oxide. Typical Application: Dull Finish

SPI D-3

Dry Blast #24 Oxide. Typical Application: Dull Finish

As Machined

No secondary polishing or grinding. Part will show tooling marks.

Overview: What is Overmolding?

How Does Overmolding Work?

Simply put, overmolding lets you combine multiple materials into one part. One material, usually a thermoplastic elastomer (TPE/TPV), is molded onto a second material, which is often a rigid plastic. Think about your toothbrush handle where the single piece has both rigid and rubbery components. It’s a great way to make plastic parts perform and look better.

Overmolding Design Tips

  • Wall thicknesses between 0.060" to 0.120" (1.5 mm-3 mm) generally provide the best bonding.
  • Keeping radii between 0.020" or 0.5mm minimum in corners reduces localized stresses.
  • If the part requires the use of thick TPE sections, they should be cored out to minimize shrinkage problems, reduce the part weight and lower cycle time.
  • Avoid deep or un-ventable blind pockets or ribs in your design.
  • Use gradual transitions between wall thickness to reduce or avoid problems with flow (back fills, gas traps, etc.)
  • The TPE/TPV should be less thick than the substrate to prevent warpage, especially if the part is flat, long, or both.
  • Overmolding needs mechanical or chemical bonding to the substrate, so your material choices should enable this.

Industries that use Overmolding

Injection Molding is used in rapid prototyping and producing pilot and high-volume production parts in a wide range of industries. It is frequently used in industries such as medical, packaging, automotive, consumer electronics, building/construction, and robotics.

Automotive

Consumer Products

Medical Devices

Featured Overmolding Resources

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Machine Hours
13MM+
Parts Quoted
1MM+
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