What is the difference between insert molding and overmolding?

Insert molding places a metal or other pre-manufactured component into the mold before plastic is injected around it. Overmolding adds a second material over an existing component or molded part to improve functionality, sealing, grip, or protection.

Which insert materials can be overmolded?

We can overmold a wide range of inserts, including stainless steel, brass, aluminum, copper, electronic components, connectors, cables, magnets, and selected engineering plastics. Each application is reviewed to ensure proper adhesion and manufacturability.

What materials are available for overmolding?

We process a broad range of engineering thermoplastics, including PC, PA, PBT, PEEK, PEI (Ultem), PPS, LCP, COC/COP, PP, ABS, and TPE. Material selection depends on your mechanical, thermal, chemical, and regulatory requirements.

Can you support both prototyping and production?

Yes. We support the entire development process—from DFM analysis and prototype tooling to low-volume pilot runs and full-scale production using hardened steel tools.

Can you help optimize my design for insert molding or overmolding?

Yes. Our engineering team reviews every project for manufacturability before tooling begins. We can recommend improvements to insert retention, material selection, gate location, wall thickness, draft angles, and overall part design to improve quality, reduce costs, and simplify production.

How do I start an insert molding or overmolding project?

Simply send us your 3D CAD files (STEP preferred), technical drawings, expected annual volumes, material requirements, and application details. Our engineering team will review your design and recommend the most suitable manufacturing approach.

Overmolding and Insert Molding

Precision overmolding and insert molding for complex, multi-material plastic components. From elastomer encapsulation and integrated inserts to custom tooling and serial production.

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Overmolding for Precision Components

Overmolding is a multi-step injection molding process where a secondary polymer or elastomer is molded over a pre-existing substrate or insert.

This approach combines mechanical strength and functionality into a single multi-material component, providing opportunities for sealing, protection, improved grip, and integrated functional features.

At Micromolds, our overmolding and insert molding capabilities are supported by in-house tooling and engineering expertise, allowing us to evaluate complex geometries, material combinations, and precision component requirements.

Not sure where to start?

Developing a component that combines multiple materials or incorporates electronic or metal inserts? Our engineers can review your design and help identify a suitable molding and tooling approach.

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Overmolding Types

Overmolding

Two molds are typically used in overmolding. One is for the primary part layer - the substrate part and the second is for the second part to overlay the substrate. Overmolding allows plastics of different colors or physical properties to fuse together.

For example, a clear acrylic lens can be overmolded into a PCB plastic housing. So overmoulding is very similar to 2-shot process but requires more manpower and two molds but cheaper with less production.

2K molding

Multi shot overmoulding is used when several resin components have to be meld together. In this way workpiece can be moulded multi colored and with required distinct physical properties, e. g. part can consist of polymer injected hard cover and elastomer injected soft cover sections. Component resins are strongly bonded chemically and thus final product is durable and wear resistant.

Main distinction between Overmolding and 2 shot molding is that 2K is performed with more expensive and complex machining and thus is usually more expensive and breaks even at larger production volumes.

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Insert Molding

Insert molding is the process when usually electronics' components e. g. cables or circuit boards are encapsulated. Low pressure moulding (LPM) is used in such cases. Wires or PCBs are covered by layers of polymers to protect them from mechanical fatigue or environmental effects respectively.

As the name of LPM itself suggests low pressure allows low-viscosity materials, e. g. hot melt polyamide materials, to easily flow in room-temperature molds with inserts in it. When solidified, insert together with overmolded material are ejected from the cavity manually or automatically and the process is finished.

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Tooling Optimized for Overmolding and Insert Molding

Overmolding requires precise insert positioning, controlled material interfaces, and repeatable alignment between molding steps.

Our in-house tooling is designed specifically for stable multi-material micro molding.

Dedicated tooling for accurate insert fixation
Mold concepts optimized for material interface control
Stable tooling for repeatable overmolding at micro scale

Tool design must also account for substrate retention, gate positioning, material flow, shrinkage, and the potential for flash or deformation around the insert.

Evaluating these requirements during the design stage helps identify potential risks before mold manufacturing begins.

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Material Compatibility and Bonding in Overmolding

Material selection is one of the most important decisions in overmolding. Two polymers that can be processed individually do not necessarily form a reliable bond when combined.

Depending on the materials and application, bonding may be achieved through chemical adhesion, mechanical interlocking, or both. Mechanical retention features can be particularly important when the selected materials do not provide sufficient chemical adhesion.

Engineers should also consider differences in shrinkage, processing temperatures, component stiffness, and the mechanical stresses expected during use. For sensitive inserts, molding conditions must be selected to minimize the risk of damage or deformation.

Early evaluation of these factors can help prevent delamination, poor sealing, insert displacement, and other manufacturing defects.

For additional information about polymer selection and material bonding, see our engineering materials guide.

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Overmolding Applications

Overmolding and insert molding combine multiple materials into one functional part, enabling integration of rigid and flexible materials, electrical interfaces, and sealing features.

Used across electronics, medical, and industrial applications where protection, sealing, and functional integration are required from prototyping to series production.

Common applications include:

Connectors and electrical contacts
Cable and wire assemblies
Sensor and PCB encapsulation
Sealing and strain relief components
Multi-material housings and grips

These processes are particularly valuable when component protection, reliable insert positioning, or the integration of multiple functions would otherwise require additional assembly operations.

For medical devices and electronics applications, material selection and manufacturing requirements must be evaluated against the component's intended operating conditions.

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Project Workflow

Share your CAD model and receive engineering feedback and a production quote.

Upload CAD for micro component manufacturability evaluation

1. Upload a CAD File

Upload your CAD model and project requirements.

Design for manufacturing analysis and quotation

2. DFM Review & Quote

Receive feedback and a production quote.

Micro tooling and injection molding production process

3. Tooling & Production

Tooling preparation and injection molding begin.

Delivery of precision micro molded components

4. Delivery

Parts are produced, inspected and delivered.

Have a Project That Requires Precision Manufacturing?

Share your project requirements and any available drawings or specifications. Our engineers can discuss suitable tooling and micro injection molding solutions.

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