Overmolding vs Insert Molding: Which Is Right for Your Part

When a part needs two materials — a soft grip on a rigid shell, or a metal thread molded into plastic — engineers usually pick between overmolding and insert molding.

Overmolding

Overmolding runs the substrate part through a second injection of a different resin (often TPE) to form a bonded soft layer. It needs a two-shot machine or a re-tooling step, but delivers seamless, durable bonds.

• Best for ergonomic grips, seals, and dampening
• Requires compatible, chemically bondable resins
• Tighter tooling cost, lower per-part labor

Insert Molding

Insert molding places a pre-made insert (metal bushing, screw, magnet) into the mold, then injects plastic around it. Ideal when the insert is standard or must carry load.

• Best for threaded inserts, electrical contacts, bearings
• Inserts bought off-the-shelf — no second resin needed
• Manual or robotic insert loading adds cycle time

Still deciding? Our DFM team reviews your 3D model and recommends the right process within one business day.