Overmolding Service

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A two-step injection molding technique to combine rigid plastics with soft, durable overlays. 天美影院’s precision mold manufacturing and high-quality overmolding production are highly recognized worldwide.

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What is Overmolding?

In product design, some of your products may have a soft material (such as TPE, silicone, or rubber) wrapped around a base material (hard plastic or metal). This is done to improve grip, prevent slipping, or enhance appearance. Such products are quite common, like tool handles, toothbrush grips, and phone cases. Their production usually requires a overmolding process.

Overmolding involves using two different plastic materials, injected separately in one injection molding machine. After the first molded in one set of molds, the product is taken out and placed into another set of molds for the second injection molding. Therefore, overmolding typically requires two sets of molds.

Powerful Overmolding Factory

No More Slippery Handles — Bond, Seal, Protect with Overmolding

天美影院 leads the injection molding industry with comprehensive capabilities. Overmolding stands as one of our proven specialties. We solve tough overmolding problems like:

Fixing Production Defects

Addressing Design Pitfalls

FirstMold’s expertise in overmolding helped us overcome key manufacturing challenges across multiple product lines. It reduces surgical grip delamination by 30% while surpassing FDA torque standards by 20% due to their TPU-PEEK overmolding technology significantly improved product durability. By implementing real-time pressure control, 天美影院 ensured 98.6% dimensional accuracy in 500k overmolded acoustic seals. This delivers unmatched precision. Meanwhile, their 1:1 pilot production for smartwatch components resulted in 99.3% tactile consistency. As a result, our products enhance the user experience. These advancements directly drove 19% growth for medical OEMs and cut electronics returns by 63%.

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Overmolding Applications and Case Studies

Injection Molding Factories use overmolding in a wide range of industries.?

?Industry	?Representative Products	?Key Advantages
?Medical Devices	Surgical instrument grips, Prosthetic components, Catheter connectors, Syringe plungers	Biocompatibility (ISO 10993), Chemical resistance, Enhanced sterilization compliance (FDA/CE)
?Automotive	Steering wheel grips, Airbag modules, Lightweight seat shells, Battery pack housings	40-50% weight reduction, Vibration damping (SAE J1475), Flame retardancy (UL94 V-0)
?Consumer Electronics	Phone cases, Earbud charging cases, Game controller grips, Smartwatch bands	Anti-slip & shock absorption, IP68 waterproofing, Seamless multi-color aesthetics
?Industrial & Tools	Power tool handles, Wrench anti-slip sleeves, Precision instrument housings	300% impact resistance improvement, MIL-STD-810G compliance, Ergonomic fatigue reduction

Case Studies:

Challenge

Frequent drops cause TWS earbud cases to crack. This leads to a 23% user complaint rate.

Solution

Hard PC inner shell and TPU shock-absorbing overmold

Surface Treatment

Skin-like matte texture, fingerprint-resistant finish

Results

A Top 3 global smartphone brand reduced after-sales repair costs by 41%

Watch a Video of Overmolding In Injection Molding Factory

Material combinations for overmolding technology

Overmolding technology is a paradigm of multi-material integrated manufacturing in industrial production, with diverse material pairing options. 天美影院 summarizes the material combination strategies for Overmolding as follows:

?Functional Synergy

i.e.: Combining polypropylene (PP) with SEBS elastomers leverages molecular chain entanglement to eliminate adhesives, while achieving gamma sterilization resistance (25kGy dose) for medical-grade handles

Performance Enhancement

i.e.: Nylon (PA66)-TPV elastomer composites exhibit exceptional resistance to oil/acid corrosion and ultra-low friction (μ=1.2). It’s ideal for high-voltage battery housings in electric vehicles.

Sustainable Innovation

i.e.: Bio-based TPE fused with PLA substrates delivers fully biodegradable solutions. By cutting carbon emissions by 50% means it meets EN 13432 industrial compostability requirements—revolutionizing eco-packaging systems.

Substrate	Overmold	Typical Applications	Certification Standards
PP	TPE/SEBS	Medical handles, tool grips	ISO 10993, FDA 21 CFR
ABS	TPU	Phone cases, smartwatch bands	IEC 60529, RoHS
PC	Liquid Silicone Rubber (LSR)	Automotive transparent buttons, baby pacifiers	IATF 16949, LFGB
Nylon (PA6/PA66)	TPV	Automotive battery housings, industrial gears	UL94 V-0, MIL-STD-810G
PBT	Glass-fiber reinforced TPE	Power tool handles, connectors	EN 61340, IEC 60695
PEEK	Fluorocarbon Rubber (FKM)	Aerospace sensors, medical implants	ISO 13485, AS9100
Metal Inserts	TPE/TPU	Power tool handles, medical devices	ISO 2768, ASTM D638
POM	Thermoplastic Elastomer (TPE)	Gear damping sleeves, precision instrument housings	DIN 54800
PPS	Silicone Rubber (VMQ)	High-temperature sensors, engine components	SAE J2460, AMS 3217
PLA	Bio-based TPE	Eco-friendly packaging, biodegradable products	EN 13432, ASTM D6400

Overmolding Vs. Insert Molding Vs. Two-color molding

Overmolding involves injecting one material onto an existing substrate (such as hard plastic or metal). This process is completed in separate steps to form a protective or functional layer. In insert molding, the inserts such as metal or electronic components are placed into the injection mold first. Then, plastic is injected to secure and integrate the inserts. In two-shot molding, a rotating mold is used to inject two different materials in the same cycle.

Dimension	Overmolding	Insert Molding	Two-Color Molding
Process Steps	Two-step injection: Hard core → Soft overmold	Pre-insert placement → Single-shot encapsulation	Dual-shot injection (rotating/sliding mold)
Material Combination	Soft-hard bonding (e.g., PP+TPE)	Plastic + metal/insert (e.g., PA66+copper)	Dual-color plastics (e.g., ABS+PC)
Equipment Requirements	Standard machine + compatible mold	Standard machine + robot/manual insert placement	Dedicated two-color machine + rotating mold (±0.02mm)
Material Interaction	Chemical bonding (thermodynamic compatibility)	Mechanical locking (no chemical bonding)	Physical layering (melting point synchronization)
Structural Difference	Layered encapsulation (functional integration)	Insert core (composite reinforcement)	Seamless layering (aesthetic fusion)
Mold Cost	$$	$	$$$
Production Cycle	30-60 sec (requires cooling between layers)	45-90 sec (manual insert placement)	20-40 sec (automated dual-shot)
Typical Products	Tool handles, medical instruments	Automotive connectors, medical electrodes	Dual-color taillights, translucent keyboard keys

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