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ISO 14001: 2015 Certified Processes
ISO 45001: 2018 Certified
ISO 13485: 2016 Medical Device
IATF16949:2016 Automotive
Plastic Injection Overmolding
What is Overmolding?
Overmolding is an advanced injection molding process that combines two or more materials into a single, integrated component. The process begins with the creation of a substrate (the base component) through standard injection molding. A second material is then molded over or around this substrate, creating a chemical or mechanical bond between the two materials.
This technique allows for the seamless integration of materials with different properties – such as rigid plastics with flexible elastomers – resulting in parts with enhanced functionality, improved ergonomics, and superior aesthetics. The overmolding process eliminates assembly steps, reduces production costs, and creates more durable products.
Overmolding vs. Insert Molding
Overmolding
Process: Injection of second material over first molded part
Materials: Typically plastic over plastic or TPE over plastic
Bonding: Chemical and/or mechanical bonding
Common Applications: Soft-touch grips, seals, multi-color components
Production Complexity: Higher (often requires two-shot molding)
Insert Molding
Process: Pre-made insert placed in mold before injection
Materials: Often plastic over metal, but can be other combinations
Bonding: Primarily mechanical bonding
Common Applications: Threaded inserts, electrical components, reinforced parts
Production Complexity: Lower (can be done in single shot)
Overmolding Materials
The compatibility between substrate and bonding materials determines bond strength, durability, and performance characteristics of the final part.
- ABS – Excellent impact resistance and dimensional stability
- Polycarbonate (PC) – High strength, heat resistance, and optical clarity
- Nylon (PA) – Superior strength and chemical resistance
- PBT – Excellent electrical insulation and heat resistance
- Polypropylene (PP) – Lightweight with good chemical resistance
- Metal Inserts – Brass, aluminum, steel for structural components
- TPE – Soft touch, good grip, wide durometer range
- TPU – Excellent abrasion resistance and elasticity
- TPV – Superior weather and chemical resistance
- LSR – High heat resistance, biocompatibility for medical applications
- Rigid Plastics – For multi-color or multi-property components
Material Compatibility Chart
The following chart indicates the bonding compatibility between common substrate and overmold materials.
C = Chemical bonding possible, M = Mechanical bonding recommended.
| Overmold Material | ABS | PC | Nylon (PA) | PBT | PP |
| TPU (Thermoplastic Polyurethane) | C | C | C | C | M |
| TPE (Thermoplastic Elastomer) | C | C | M | M | C |
| TPV (Thermoplastic Vulcanizate) | M | M | M | M | C |
| LSR (Liquid Silicone Rubber) | M | M | M | M | M |
| Rigid Plastics (PC, ABS, etc.) | M | M | M | M | M |
Overmolding Capabilities
| Technical Parameter | Capability |
| Maximum Part Size | 18″ x 24″ x 8″ (457mm x 610mm x 203mm) |
| Minimum Part Size | 0.5″ x 0.5″ x 0.1″ (12.7mm x 12.7mm x 2.5mm) |
| Shot Capacity | Up to 60 oz (1,770 g) |
| Wall Thickness | 0.020″ to 0.500″ (0.5mm to 12.7mm) |
| Dimensional Tolerances | ±0.003″ (±0.076mm) plus material shrinkage |
| Surface Finish | SPI A1-D3 finishes available |
| Minimum Draft Angle | 0.5° for textured surfaces, 0.25° for smooth surfaces |
| Production Volume | Prototypes to 100,000+ parts |
| Lead Time | As fast as 15 days for production parts |
| Quality Control | In-process inspection, first article inspection, CMM verification |
Overmolding Design Tips
- Wall Thickness – Maintain consistent wall thickness between 0.040″ to 0.120″ (1.0mm to 3.0mm) for optimal material flow and minimal warping.
- Bond Enhancement – Incorporate mechanical interlocks like undercuts, dovetails, or surface texturing to improve adhesion between materials.
- Material Selection – Choose compatible substrate and overmold materials that achieve the desired bond strength and performance characteristics.
- Draft Angles – Design with adequate draft angles (minimum 0.5° for textured surfaces) to facilitate part ejection from the mold.
- Gate Location – Consider gate placement to minimize visible gate marks and optimize material flow throughout the part.
- Radii and Corners – Use generous radii (minimum 0.020″ or 0.5mm) to reduce stress concentration and improve material flow.
- Overmold Thickness – Keep overmold thickness between 0.020″ to 0.100″ (0.5mm to 2.5mm) for optimal bonding and material performance.
Overmolding Finishes
Surface Textures
- High-gloss polish (SPI A-1, A-2, A-3)
- Semi-gloss finish (SPI B-1, B-2, B-3)
- Matte finish (SPI C-1, C-2, C-3)
- Textured grip patterns (SPI D-1, D-2, D-3)
Color Options
- Custom color matching (Pantone, RAL)
- Transparent and translucent options
- Multi-color combinations
- Special effects (metallic, pearlescent)
Specialized Finishes
- Soft-touch coatings
- Antimicrobial treatments
- Chemical-resistant finishes
- UV-resistant coatings
Competitive Benefits of Overmolding Application
Insert molding combines metal inserts with plastic in one efficient step, offering numerous benefits compared to traditional assembly methods.
Part Consolidation
Reduce assembly costs and improve reliability by combining multiple components into a single overmolded part. Eliminate fasteners, adhesives, and secondary operations while enhancing structural integrity.
Enhanced Ergonomics
Improve user comfort and control with soft-touch overmolded grips and interfaces. Custom textures and durometers can be tailored to specific applications, reducing user fatigue and improving safety.
Environmental Protection
Create waterproof, dustproof, and chemical-resistant seals through strategic overmolding. Protect sensitive components from harsh environments without additional gaskets or sealants.
Vibration Dampening
Reduce noise and vibration with strategically placed elastomeric overmolds. Improve equipment performance and longevity while enhancing user comfort and reducing fatigue.
Aesthetic Enhancement
Differentiate your products with multi-color, multi-texture overmolded components. Incorporate branding elements directly into the part while improving visual and tactile appeal.
Cost Reduction
Lower total production costs through elimination of assembly steps, reduced part count, and minimized inventory management. Streamline your supply chain while improving product quality and consistency.
Overmolding Process
Our overmolding process combines precision engineering with advanced manufacturing techniques to create seamless, multi-material components.
Depending on your project requirements, we utilize either two-shot molding or insert molding processes.
Discuss Your Technical Requirements
Our engineering team can help determine the optimal approach based on your specific requirements.
Two-Shot Overmolding Process
- Substrate Injection – The first material (substrate) is injected into the mold cavity
- Mold Rotation – The mold rotates to position the substrate for the second shot
- Overmold Injection – The second material is injected over the substrate
- Cooling – The complete part cools within the mold
- Ejection – The finished multi-material part is ejected from the mold
- Quality Inspection – Each part undergoes rigorous quality control
Insert Overmolding Process
- Substrate Production – Substrates are molded in a separate operation
- Substrate Placement – Pre-molded substrates are manually placed in the second mold
- Overmold Injection – The overmold material is injected around the substrate
- Cooling – The complete part cools within the mold
- Ejection – The finished multi-material part is ejected from the mold
- Quality Inspection – Each part undergoes rigorous quality control
Industries We Servce
Automotive
Medical Devices
Industrial
Overmolded Parts
Start Your Overmolding Project Today
Ready to enhance your product with custom overmolding?
Contact us today to discuss your project requirements and receive a competitive quote.
Related Resources
How Does Overmolding Work | Everything You Need to Know
Discover how overmolding works to create multi-material injection molded parts with enhanced functionality and design flexibility.
Overmolding vs Insert Molding: What’s the Difference?
Discover the key differences between overmolding vs insert molding—two essential injection molding techniques for manufacturing. Learn their unique features, applications, and benefits to optimize your production process.
What Is Overmolding in Injection Molding?
Learn about Overmolding in injection molding, its operations, design tips, and materials. Discover its benefits, challenges, and applications in various industries.