Custom Overmolding and 2k Injection Molding Factory

ZetarMold Specializes in Custom Overmolding and Two-Shot Injection Molding Projects Since 2005

Converting Ideas Into Reality

With Zetar, you can have your project come true in a matter of days. With more than 20 English-speakers and 7 experienced engineers on hand to support the process from idea to reality – let us help turn your dream into a reality!

Ideas Reality

From Sketch To 3D Model

Ideas Reality

From Sketch To Final Product

How We Work

Get your Idea

Communicate your ideas with our sales and engineers and get sketches of your plans

3D Model Design

Product engineers make the 3D model design according to your idea


After confirmed the 3D modle, Some complex product will make prototype to verify the assembly and function

Mold Design

After verifying the prototype, our mold engineer will do DFM report, Mold Flow and the mold design


Some products require assembly and packaging services according to customer requirements

Post Processing

After mass production, Will do post-processing including logo printing, painting, plating, laser engraving, ultrasonic welding etc.

Product Produce

After injection mold making finished, we will send the test samples to customer for comfirmation, and then start the mass production

Injection Mold Making

After the 3D design of the mold confirmed, the injection mold maker will starts the injection mold making

Why Choose Zetar

Zetar has successfully met the standards for ISO 9001, ISO 13485, ISO 14001, and ISO 45001 certifications. We focus on plastic injection molding manufacturing since 2005. At Zetar, our experienced and educated team excels in research and development,  injection molding manufacturing, quality control, marketing, and customer service.


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Meeting Room

Injection Mold Work Shop

Injection Molding Work Shop

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Samples Room

Assembly Room


Zetar's Quality Certification

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ISO 9001

ISO 14001

ISO 45001

Plastic Injection Overmolding Manufacturing

Discover the Ideal Solutions for Your Plastic Injection Overolding Project: Achieve Excellence with Optimal Solutions

Resources for The Complete Guide to Overmolding

What is Overmolding?

Overmolding is an injection molding process where you mold one material over top of another material or substrate. The first material is usually made of a different material or has a different shape than the second material. Overmolding is used in many industries including medical devices, automotive, aerospace, and consumer products.

To overmold, you first mold or make the first part. Then you mold the second material over top of the first part. The second material can be a different plastic, rubber, or other material that gives the part special properties like flexibility, durability, or looks.

How Does Overmolding Work?

Overmolding is a tricky process that has a bunch of steps and needs you to plan and do it right. Here’s a quick look at how overmolding works:

1. Design and Prototype:

Designers create a 3D model of the main part and the other material. They make prototypes to test the design and make sure it meets the required specs.

2. Tooling:

Tooling is made for both the main part and the other material. Tooling includes molds, and other equipment needed for the molding process.

3. Main Part Production:

The main part is made using the main tooling. The main part is usually made of a hard material, like hard plastic (PP, ABS, PA, PC, etc).

4. Overmolding Process:

The other material is injected into the mold, which has the main part. The other material flows around the main part, making a strong bond. The other material is designed to fit the shape of the main part.

5. Cooling and Ejection:

The mold is cooled for the other material to solidify. Then the mold is ejected, and the overmolded part is removed.

6. Finishing:

We check the overmolded part to make sure it’s good to go. We trim off any extra plastic, clean it up, and get it ready for the next step.

Overmolding Material Bonding Chart

You can bond overmolded materials together, but you need to make sure the materials work together to get the bond strength you want. If you really need the bond, you should definitely add a mechanical bond. An undercut is a good example of a mechanical bond.

Substrate Material
Overmolding Material PP T30S ABS DG417 ABS/PC AC2300 PC Makrolon® 2405 PBT HR5330 PA J2700

M= Mechanical Bond Recommended

C= Chemical bond

What are the Benefits of Overmolding?

Overmolding is great because:

Better Chemical Resistance: Overmolding can be used to make the primary part more resistant to chemicals, so it doesn’t get all corroded and messed up.

Added Functionality: Overmolding can be used to add new features or functionality to the primary part, thereby increasing its utility and value.

Simplified Assembly: Overmolding can help you avoid assembly by combining multiple parts into one, which makes manufacturing easier.

Better Performance: Overmolding can be used to make the primary part better by adding new materials or properties that make it work better.

Make it Look Good: Overmolding can make the main part look better. It makes it look nice.

Lose Weight: Overmolding can help you lose weight. It makes your main part lighter, but still strong and tough. It makes it easier to carry and handle.

Better Thermal Resistance: Overmolding can be used to make the primary part more resistant to heat, so it won’t get too hot or cold.

Stronger and Tougher: Overmolding can make your part stronger and tougher, so it lasts longer and performs better.

Better Electrical Insulation: Overmolding can be used to improve the electrical insulation of the main part, which helps protect it from electrical shock and damage.

Better Looking: Overmolding can make the main part look better. It can be made to look more attractive.

What are the Applications of Overmolding?

Overmolding is a versatile manufacturing process that can be used to create complex parts with unique properties and functionality, making it applicable to a wide range of industries.

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Handware tools: Overmolding can be used to make hand tools like wrenches, pliers, and screwdrivers, knives, saw blades, and drill bits tougher and easier to hold.

Medical Devices: Overmolding is used in medical devices like syringes, needles, and implantable devices, where precision and accuracy are crucial.

Automotive: Overmolding is used in car stuff like dashboards, door handles, and trim components, where you need them to last and work good.

Industrial Equipment: Overmolding is used in industrial equipment like machines, pumps, and valves where you need them to be tough and work good.

Consumer Products: Overmolding is used in consumer products like toys, appliances, and electronics, where looks and how it works are important.

Overmolding Design Guide: Top 10 Tips For Overmolding

Overmolding design is hard. But you’ve got to make sure your parts are designed right for the overmolding process. Here are some design tips for overmolding.

① Don’t overmold the whole base substrate. Overmold it in sections.

② Don’t make edges that are too thin or that come to a point. When you inject the plastic, the flow slows and then cools. That makes the plastic stick to the part less.

③ Keep the overmolding thickness consistent: the overmolding should be between 1.5 and 3 millimeters (0.060 and 0.120 inches).

④ Try not to have sudden changes in thickness. If you need different thicknesses, try to make them as smooth as possible.

⑤ Lots of overmolding materials are stretchy, so you can put smooth bumps into the design.

⑥ Make sure the overmolding layer is thinner than the substrate underneath to help prevent warping.

⑦ To make sure the overmolding cavity bonds well, you need to account for substrate shrinkage.

⑧ Use a TPE or TPU that has a melt temperature lower than the substrate.

⑨ Design the overmold to sit just below the surface of the substrate.

⑩ If you want more holding power, design undercuts, keyways, and other mechanical features to lock the materials together.

What are the Common Problems and Solutions for Overmolding?

The most common problems you’ll run into with overmolding are: Adhesion problems, Incomplete filling of the substrate or overmolding, Flashing. Here’s what you can do to fix these problems.

Observation Potential Causes Corrective Actions
Flash (on the part’s edge or over the substrate) ① Mold doesn’t fit well
② Molding machine isn’t big enough
③ Shutoffs aren’t designed well
④ Substrate shrinks
① Check and Fit the Mold Again
② Increase or decrease injection and pack pressure
③ Re-cut the tool to get a complete shut-off
④ Check for substrate sinks and re-cut the tool
Short Shots ① Not enough material
② Not enough injection pressure
③ Not enough fill speed
④ Melt too cold
⑤ Poor venting
① Increase shot size
② Increase injection pressure
③ Increase injection speed
④ Increase melt temperature
⑤ Decrease the clamp tonnage and re-cut vents
Warped Parts ① Shrinkage after molding
② Substrate Wall thickness is too thin
③ Overmolding area is too large
① Make the cool time longer
② Add Substrate Wall thickness or make the ribs thicker
③ Make the overmolding area smaller
Overmold Breaks ① Substrate not supported properly
② Injection pressure and melt temperature too high
③ Gate in wrong place
① Fully support the substrate to resist hydraulic injection pressures and melting
② Lower injection pressure and melt temperature
③ Move the gate
Surface sink marks ① Non-uniform part release from tool surface due to material shrinkage
② Gate freezes too early
① Increase pack pressure/hold time and decrease material temperature
② Increase gate size
Bad sticking ① Material don’t match
② Gate freeze too soon
① Get the right kind of material
② Increase the temperature of the molten plastic and the temperature of the mold
Knit lines are bad ① Gas gets trapped between the plastic
② The plastic melts at a low temperature
① Make the air vents better
② Speed up the injection and increase the melt/mold temperature
Stick femal cavity ① Not enough draft angle
② Vacuum in the female cavity
③ Femal cavity too hot
④ Femal cavity too shiny
① Increase the draft angle
② Provide air assist release
③ Run the femal cavity cooler
④ Sandblast the cavity

2K Injection Molding Supplier

Custom 2K Injection Molding to Meet Your Manufacturing Needs

What is 2K Injection Molding?

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2K injection molding, also known as 2K molding, is a manufacturing process where you inject two different materials or colors of plastic into a mold to make one part with unique properties and looks.  This process is also known as “two-color injection molding” or “dual-color injection molding.”

In 2K injection molding, you usually inject the two materials at the same time, but separately, into the mold through two different gates. This is different from two-shot injection molding, where you inject the two materials one after the other.

How Does 2K Injection Molding Work?

2K injection molding is a process that involves injecting two different materials into the same mold through separate injections but within the same molding cycle. This results in a complex part that can have different colors, textures, or material properties, all in one piece without the need for post-molding assembly.

The whole process is highly automated and controlled, requiring less labor and minimizing the risk of human error, which is crucial for the high-volume production of complex parts.

1. 2K Injection Mold Design:

The mold is designed with two cavities, one for each material or color.

2. Material Selection:

The two materials or colors you choose should be based on what you want the final part to look like and what you want it to do. You can use different plastics, different colors, or even different materials that have different properties, like texture or transparency.

3. Material Preparation:

The two materials are prepared for injection by melting them in separate hoppers or barrels. The melting process involves heating the materials to a temperature above their melting point, typically between 150°C to 300°C (302°F to 572°F).

4. Injection:

The melted materials are injected into the mold through separate gates, one for each material.

5. Material Distribution:

The two materials are shot into the mold cavity. The first material fills the cavity to a certain depth or thickness. Then, the mold spins 180 degrees, the second material is shot into the mold, filling the rest of the cavity.

6. Cooling:

The mold is cooled to a temperature below the melting point of the materials, usually around 20°C to 50°C (68°F to 122°F). This lets the materials solidify and bond together.

7. Ejection:

The mold is opened and the part is ejected. The part is then removed from the mold and any excess material is trimmed away.

2K Injection Molding vs. Overmolding

2K injection molding and overmolding are two different manufacturing processes used to create complex plastic parts with multiple components. The choice between 2K injection molding and overmolding depends on the specific requirements of the part, including design complexity, material properties, and production volume.

Specific Requirements 2K Injection Molding Overmolding
Design Complexity ① Simple Geometries
② Limited design complexity
① Complex Geometries
② Complex Designs
Production Volume ① high-volume production
① Medium and lower-volume production
Injection Machine ① 2K injection molding machine
② Injection Machine Expensive
① Single nozzle injection molding machine
② Injection Machine Cheap
Injection Process ① Two materials are molded together
in the same process
① Two materials are molded separately

What are the Benefits of 2K Injection Molding?

2K injection molding offers a bunch of benefits, including:

Improved part quality: The two materials can be designed to provide improved part quality, such as increased strength, durability, or looks.

More design flexibility: 2K molding allows you to create complex geometries and shapes that would be hard to make with traditional injection molding.

Simplified assembly: 2K molding eliminates the need for separate parts to be assembled, which saves on labor costs and increases efficiency.

More functionality: The two materials can be designed to give specific functional benefits, like better thermal insulation or electrical conductivity.

Cool Looks: 2K molding lets you create crazy color schemes, patterns, and designs that you can’t get with regular injection molding.

Save money: By using a 2K mold, you can cut costs by not having to assemble separate parts and using less material.

More complex designs: 2K molding allows you to create parts with intricate designs and shapes that would be tough to make with traditional molding.

Better durability: The two materials can be made to be more durable and last longer.

What are the Applications of 2K Injection Molding?

2K injection molding has a wide range of applications across various industries like:

Automotive: Dashboard trim, door handles, and other interior components.

Medical: Syringes, test strips, and implantable devices.

Aerospace: Aircraft parts, satellite components, and other high-performance applications.

Consumer Products: Toys, games, toothbrush and household items.

Electronics: Enclosures, connectors, and other electronic components.

Industrial: Pumps, valves, and other industrial equipment components.

2K Injection Molding vs Overmolding: Which Is Better?

Here’s a price comparison of 2K Injection Molding and Overmolding for a specific project at quantities of 5,000,  10,000,  50,000, and 100,000 Pcs/Order.

Project Details:

① Product Mateiral: PP M800E and TPE 60A

② Product Weight: 58g and 18g

③ Mold Cavity: 1+1

2K Injection Molding Overmolding Which Is Better
Product Quantity/ PCS Mold Cost/ $ Part Price/ $ Total Price/ $ Average Part Cost/ $ Mold Cost / $ Part Price/ $ Total Price/ $ Average Part Cost/ $ 2K Injection Molding Vs. Overmolding
5000 18000 0.65 21250 4.25 12000 0.78 15900 3.18 Overmolding
10000 18000 0.63 24300 2.43 12000 0.76 19500 1.96 Overmolding
50000 18000 0.58 47000 0.94 12000 0.74 49000 0.98 2K Injection Molding
100000 18000 0.54 72000 0.72 12000 0.72 84000 0.84 2K Injection Molding

2K molding typically only makes sense for larger production runs, whereas overmolding is better for medium and low volume production runs.

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