Overmolded Parts

Rigid + soft touch.
Two-shot molded.
Integrated function.

Overmolded injection molded parts combine two or more materials in a single molded part. Rigid PP with TPE soft-touch grip. PBT connector with silicone seal. PC housing with overmolded rubber feet. Integrated function reduces assembly cost and improves product quality.

Overmolded Parts Quote Rapid injection molding

2K / 3K molding Rigid + elastomer Integrated function No assembly

01 · Overmolding applications

Common overmolding applications.

Overmolding creates parts with integrated secondary material that would otherwise require separate assembly. Common combinations address grip, sealing, aesthetic, and function.

Soft-touch grips

PP/PC + TPE

Power tool grips, utensil handles, consumer product grips. Rigid structure + soft feel in single part.

Sealed connectors

PBT + silicone

Automotive electrical connectors with integrated silicone seals. Weatherproof without separate O-rings.

Integrated gaskets

Rigid + rubber

Parts with molded-in gaskets for valve bodies, housings, fluid handling.

Multi-color

Multiple rigid

Consumer products with multiple colors — buttons, switches, decorative features in single part.

Cable strain relief

PA + TPU/TPE

Cable entry points with integrated flexible strain relief. Common in consumer electronics.

Soft-touch bumpers

Rigid + rubber pads

Device corners with rubber bumpers for drop protection. No separate bumper assembly.

Overmolded inserts

Rigid + threaded insert

Molded threads too weak — overmold rigid material around brass threaded inserts for strong threads.

Encapsulation

Rigid protective

Electronic modules encapsulated in rigid plastic for shock/moisture protection.

02 · Overmold material combos

Common material pairings.

PP + TPE

Most common. Polypropylene rigid + thermoplastic elastomer grip — handles, toothbrushes, kitchenware

PC + TPU

Polycarbonate + TPU — premium consumer electronics with soft-touch features

ABS + TPE

Cost-effective consumer electronics with soft-touch panels, grips

PBT + silicone

PBT connector body + LSR silicone seal — automotive and industrial connectors

Nylon + TPE

Sporting goods, outdoor equipment — tough nylon + grip

PA + metal inserts

Overmolded brass threaded inserts, knife-edge contacts in electrical devices

PC + PC different colors

Multi-color premium consumer products — watch faces, premium controls

Rigid foam core

Rigid skin + foam core for weight reduction in bulky handles

Multi-region color

Two or three color pattern in single part — logo inlays, decorative features

FAQ

Overmolded Parts questions.

Two-shot (2K) injection molding: single mold with two cavities. Shot 1: first material injected and partially cooled. Mold rotates or moves, second cavity exposed. Shot 2: second material injected, bonding to first material. Cycle typical 40-90 seconds. Requires specialized 2K injection machine with two barrels and rotary table or moving insert. Tool cost: 1.5-2× single-material tool.

Second material must chemically or mechanically bond to first for durable overmolding. Compatible pairs (chemical bond): PP + TPE, PC + TPU, ABS + TPE, PBT + TPO. Incompatible pairs (mechanical bond only): PP + PC, ABS + nylon — these require undercuts or texture for mechanical retention. For unknown combinations, test bond strength in pilot — we can verify before production tooling.

Aluminum 2K tooling: $10,000-30,000. Steel 2K production tooling: $30,000-100,000. Premium over single-material tooling justified by eliminated assembly cost. For 50,000+ annual production of soft-touch consumer products, 2K molding typically cheaper total cost than separate molding + assembly.

Design considerations: (1) Thickness of overmold typically 1-3 mm. (2) Bond interface should have some texture or undercut for mechanical backup to chemical bond. (3) Flow paths for second material shouldn't fight against first material geometry. (4) Wall thickness ratio between materials should be balanced. (5) Parting lines coordinate between both shots. DFM review essential — we analyze overmold designs before tooling.

Insert molding: single-shot injection over pre-placed inserts (metal threaded inserts, electrical contacts, previously-molded first component). Simpler tooling than 2K molding. Used for: overmolding metal inserts, combining molded first component with overmold, small-volume applications where 2K tool cost not justified. We offer both approaches depending on application.

2K molding is production-intent process. Break-even vs separate molding + assembly: 5,000-20,000 units annually depending on part complexity. Below that volume: standard molding + manual assembly often cheaper. Above: 2K integration wins. For prototype validation of overmold concept, consider: urethane casting with two-shot silicone mold, or 3D printed multi-material (Polyjet) before committing to 2K tooling.