Inert Molding and Overmolding

High-quality custom overmolding and insert molding services for on-demand production parts. Upload the part design to get an online quote.

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Zhongde Overmolding & Insert Molding Service

Zhongde, a reputable on-demand manufacturer in China, provides insert molding & over-molding services and produces unique multi-material parts. Both over-molding and insert molding injection processes by Zhongde involve putting two types of materials together to make one part, and the inserts can be threaded metal inserts. This ensures a seamless combination of multiple plastic parts to give a uniform and durable product.

Overmolding Process

The overmolding process involves molding one material (typically a soft or flexible material) over another material (usually a rigid substrate) to create a multi-layered part. The overmolded parts will provide additional functionality, improve grip, enhance aesthetics, or add insulation to the finished product.

overmolded part
insert molded part

Insert Molding Process

The insert molding process involves placing pre-formed components or inserts (such as metal parts, electronics, or other molded parts) into the mold cavity and then injecting molten material around them to create a single integrated part. The inserts are securely bonded to the molded material during the molding process. The metal insert molding eliminates post-molding assembly and separate parts installation.

Injection Molding Molds Making and Tooling Services

Zhongde is an on-demand manufacturer from mold designing and rapid prototyping to mass production. We offer custom mold-making, prototype tooling, and production tooling services. Our experienced team utilizes advanced CAD/CAM software and state-of-the-art equipment to injection mold design, mold making, and maintain molds with exceptional precision and durability for high-quality custom molded parts. Check our injection molding capabilities and tooling services below.

Item Details
Injection Molding Service Options Prototyping & on-demand manufacturing
Insert Molding Inserts are placed into the mold and molding occurs around them. This allows for inserts such as helicoids to be molded in your design.
Overmolding Premade parts are placed into the mold to mold over them. This allows for multi-material injection molding.
Mold Material Steel P20, H13, S136, 2316, 2344, 083, 718H, SKD618, etc.
Production Tooling Traditional molds, used for mass production.
Mold Type Family molds, Single cavity molds, multi-cavity molds, two plate molds and three plate molds.
Mold Storage Stored for 3 years in inactivity
Guaranteed Mold Life Unlimited
Mold Remachining We can re-machine the molds if there are any changes required, basis on mold structure.

Size of Over Molding and Insert Molding Parts

The below table shows the regular size of the custom insert molding parts and overmolded parts. If you need a larger size or other unique requirements about the size, Zhongde as a professional China precision injection molding manufacturer, can also help you achieve it at a competitive price.

Size Metric Inch
Length 2500 98.4
Width 2000 78.7
Height 1500 59

What Materials Are Used in Overmolding and Insert Molding?

At Zhongde, we not only offer a wide range of molding materials but also provide additives to meet special requirements. Our professional material expert can customize the most cost-effective materials to meet your specific needs. There is our injection molding materials and additives list for your reference.

The General materials listed below are for custom insert and overmolded plastic injection.

  • ABS
  • HDPE
  • PA6/6
  • PTFE
  • PP
  • PC
  • PE
  • PS
  • PA6
  • POM
  • PMMA
  • LDPE
  • PVC
  • PU

The general rubber overmolding and insert molding materials are listed below:

  • EPDM
  • PVC
  • TPU
  • Silicone
  • TPE
  • TPV

The preformed and inserts metal materials are listed as below: 

  • Aluminum
  • Carbon Steel
  • Brass
  • Stainless Steel
  • Copper

Injection Molding Surface Finishing

Injection molding surface finish is critical to a successful part design and it is used for aesthetic and functional reasons in injection molded parts for engineering products. The surface finish improves the look and the feel of a product as the perceived value and quality of the product increase with a suitable surface finish.

Different grades of surface finishing chart.

surface finish Glossy


A-grade finish is smooth and highly reflective, giving the product a shiny appearance. It’s often used for products where aesthetics are important.

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surface finish Semi-glossy


The B-grade finish is less reflective than glossy but still has a smooth and somewhat shiny appearance.

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surface finish Matte


C-grade finish is non-reflective and has a dull appearance. It’s often chosen for parts where glare or light reflection is undesirable.

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surface finish Textured


D-grade finishes are intentionally rough or patterned. They can provide a better grip or a unique appearance to the product.

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What Are the Difference Between Overmolding and Insert Modling?

Overmolding process and insert molding process are two specialized injection molding techniques used to combine multiple materials or components into a single molded part. Here’s a comparison and explanation of the two processes:


Purpose: The overmolding process primarily adds functionality, aesthetics, or comfort, while the insert molding process combines disparate components or inserts to create a single integrated part to eliminate post-molding assembly and separate parts installation.


Molding Cost: The overmolding process may require additional material and labor, making it potentially more expensive than the insert molding process, which involves integrating pre-formed components.


Molding Steps: Overmolding process is a two-step or double-injection molding technique. However, insert molding process is a single injection molding method.


Material Compatibility: The overmolding process often involves using different materials with compatible bonding properties. The insert molding process can accommodate a wide range of inserts, including metal, plastic, or electronic components.


Both overmolding process and insert molding process provide unique benefits depending on the application requirements, offering improved functionality, reduced assembly processes, enhanced aesthetics, and cost savings. The choice between the two techniques depends on the desired outcome, design considerations, and specific project needs.

overmolding process

Insert Molding and Overmolding Types

There are many kinds of overmolding and insert molding depending on the different materials, including plastic over plastic, plastic over metal, rubber over metal, and rubber over plastic. Dividing the materials of the mold, there are two kinds of overmolding – plastic overmolding and rubber overmolding.

The below Images show the different types.


Bonding The Resin to the Metal


Metal Insert into the Resin


Rubber Onto Plastic

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Related Products of Overmolding & Insert Molding

All You Need to Know About Overmlding

Overmoulding is a manufacturing process that involves molding a material over another material or substrate to create a single part. A toothbrush with a rubber grip is an example of an over-molded object.

Why Choose Zhongde for Custom Injection Molding Partner?

Zhongde has extensive experience, advanced equipment, and a commitment to quality. We offer competitive pricing, fast turnaround times, and excellent customer service. With a skilled team and state-of-the-art facilities, we ensure precise and reliable production. Whether you need rapid prototyping or high-volume on-demand manufacturing, Zhongde is your trusted partner for custom injection molding solutions.

FAQs of Insert Molding & Overmolding

View our FAQ center for more questions.

Factors such as material compatibility, design feasibility, and proper part alignment should be considered during the overmolding or insert molding process.

Overmolding and insert molding find applications in industries such as automotive, electronics, medical, consumer goods, and more, where product durability and functionality are crucial.

Yes, existing products can often be retrofitted with overmolding or insert molding to improve their performance, functionality, or aesthetics.

Consult with our experts who can assess your product requirements and guide you on the feasibility and benefits of utilizing overmolding or insert molding for your project.

Related Services of Zhongde On-demand Manufacturing

Selective Laser Sintering

CNC Milling

CNC Turning

Fused Deposition Modeling

Rubber Injection Molding

Plastic Injection Molding

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