Overmolding Services
Overmolding is the process which adding a second layer of plastic (usually is TPE) over a premolded plastic part (we referred to as the substrate) during injection.
Overmolding (two-shot molding) provides designers with great flexibility to create complex geometries, a variety of materials and colors, durable and ergonomic plastic products.
  • 3D modeling, design, modification
  • Detailed DFM analysis, mold design
  • Mold making and prototyping
  • ISO 9001:2015, IATF 16949:2015 certificated
  • 24/7 engineering support
  • Two color mold, overmolding tooling, multi-shot molding
  • Material selection assistance
How does Overmolding Work?
Overmolding is a process which using two separate mold and two material bond together form a full plastic parts during injection molding, the molding material can be the same or different.
1. Creating the Substrate
The first step is to create the substrate plastic part using injection molding. This substrate will be the innermost layer of the overmolded part.
2. Substrate Placement
Manual or servo robot loading the substrate or substrate component (insert + plastic substrate) is placed into the second mold cavity.
3. Create Overmold Layer
The molten plastic is injected into the second mold. The plastic will flow around the substrate or substrate components (substrate + metal insert), covering substrate components and fuse with the front half of the plastic and fill the entire mold cavity.
4. Cooling & Stripping
After the parts are cooled and cured, ejection, manual or robotic arm to remove the product, the whole remolding process is completed.
Benefits of Overmolding
Benefits of Overmolding Overmolding can quickly creating durable, reliable, vibration-resistant, A variety of materials are integrated and complex geometries plastic components. overmolding offers numerous advantages.
Increased Strength & Durability
Forming a tight combination through chemical and mechanical bonding not only improves grip, adds cushioning, insulation or sealing, but also improves product functionality, performance and durability.
Increasing Design Flexibility
This process allows designers to create parts with complex geometries and unique features through the use of different materials and colors.
Lower Cost
Overmolding combines multiple parts into a single part, eliminating complex assembly costs and minimizing the risk of assembly errors.
Improved Aesthetics
Overmolding can enhance the visual appeal of products and increase market competitiveness through a variety of materials, colors, textures and finishes.
Overmolding Materials
We offer a variety of materials for overmolding projects, depending on the geometry, complexity and requirements of your project. In overmolding, the two plastic materials that are molded can be the same or different. Most of them are soft plastics (TPE) wrapped in hard plastics, but hard plastics can also be wrapped in hard plastics, and soft plastics can be wrapped in soft plastics. We have successful experience making any two of these overmolding material options.
Rigid Plastics
  • Polypropylene (PP)
  • Polycarbonate (PC)
  • ABS
  • PMMA (Acrylic)
  • Nylon
  • PE
  • PBT
  • POM
  • SAN
  • PS
  • PC/ABS
  • PFA
  • PEEK
  • PPS
  • PEI
  • LCP
  • PPSU
  • PPA
  • PES
Flexible Plastics
  • TPE
  • TPU
  • Silicone Rubber
Overmolding Substrate Loading Operations
Generally, the overmolding process is the same as an injection molding process, except that the second molding molten plastic is molded over another component. The difference lies in operation. With overmolding, the substrate is loaded into the mold cavities on each cycle. In addition, how the substrate is loaded creates two different overmolding operations.
1. Manual loading
In common, manual loading overmoding need two separate mold, one mold making the substrate, the second mold is called over mold. After the substrate finish, The substrates are then hand loaded into another mold for the overmolding operation. The operator will also remove the finished part from the mold, inspection, and package the parts. Manual overmolding is the most common procedure for low to mid-volume overmolding.
Benefits of manual loading substrate
  • Operate Simple
  • Lower mold cost
Defect of manual loading substrate
  • High labor cost
  • Low yield, low quality
Manual loading of substrates is suitable for small to medium volume orders.
2. Double Injection Molding
Double injection is to inject two plastic materials on the same injection molding machine with two time injection molding, but the product is ejected in one time. It is usually completed by a set of molds and requires a special two color injection molding machine.
In two color mold injection, the mold is clamped, the first material is injected into the mold to form the substrate, then, the mold is opened, the substrate is left in the core side, then the mold is rotated by 180 degrees, the mold is closed again and the second plastic resin is injected into the mold cavity through the second barrel to form a two color plastic part, cooling, cure, eject, finish a injection cycle.
Benefits of double injection molding
  • High efficiency
  • High quality
  • lower price than tradition overmolding
Defect of double injection molding
  • High mold cost
  • High mold machining requirement
  • Need high quality molding equipment
If there is a high requirement for your overmolding plastic parts production capacity and quality, double injection molding is the ideal process.
Overmolding Design Tips/Considerations
In overmolding design, proper shut off design is critical to stop the second plastic material flow in precise geometry location and prevent undesirable random edge flash. here is some overmolding design tips or considerations.
Design tips/considerations
Maintain uniform thickness
The overmolding should maintain a constant thickness between 1 mm to 3mm. If really need sections of different thicknesses, avoid abrupt changes in thickness and smooth out surfaces as much as possible or add excess areas between different thicknesses
Material compatibility
Try to choose two materials with good adhesion and a gap in melting temperature to ensure strong and reliable bonding between layers without melting of the substrate plastic part.
Design for bonding
1) Chemical bonding: Chemical bonding uses the intermolecular attraction between materials. It is also the basic method of bonding between overmolding materials.
2) Mechanical bonding: Create appropriate structures such as undercuts, ribs, holes, and other interlocking structures on the substrate to facilitate mechanical bonding between the injection molded part (substrate) and the overmolded material.
Consider shrinkage
Consider the material shrinkage difference between the substrate molded part and the overmolding material to prevent warpage or dimensional inconsistency from causing flash or crushing the base part during overmolding.
Draft Angles
Adding draft angle helps plastic parts stripping smoothly from the mold, reducing the risk of product damage during ejection.
Avoid sharp corners
Rounded edges and corners can accelerate material flow and reduce local stress concentrations.
Overmolding gate loaction
Overmolding gate should be positioned away from critical features and edges of the substrate to avoid damaging the substrate by hot molten material during molding.
Strong Substrate
The strong substrate plastic parts can prevent shifted or deformed due to excessive pressure during injection molding. To accomplish this the tool needs to be designed with geometry that captures the insert. simple mean is the contour of the second mold must fully support the substrates.
Tight tolerance mold
Seams must be very tight between the overmold and substrate, otherwise, flash will easy to occuring
Avoid thin edges
Avoid edges that taper to a fine point. During ovemolding, slowing of the flow and subsequent cooling can have adverse effects on the adhesion between the substrate and overmolding.
The substrate should be firmly fixed
Account for shrinkage of the substrate. it must to be located successfully and held sufficiently to ensure proper fixation in the overmolding cavity. This is critical because failure can result in scrap parts or even mold damage that is often lengthy and expensive to repair.
Integrate venting into your design to allow air to escape during the injection process and avoid deep or airtight blind pockets.
Avoid warpage
To avoid warping, keep the overmolding layer wall thickness thinner than the substrate, especially if the part is flat, long, or both.
Gallery of Overmolding Parts
Dive into Attractive Plastics' extensive gallery that showcases some of our completed overmolding parts and take confidence that we can create your overmolding project according to your strict specifications.
Overmolding Material Selection Tips/Considerations
A variety of thermoplastic materials can be overmolding, from soft plastics (such as thermoplastic elastomers) to hard plastics (like Nylon, ABS, polycarbonate etc.). overmolding materials used can either be the same materials or different.
When selecting materials, the adhesion of the two materials is the most important basis for material selection. Overmolding, which uses intermolecular attraction to bond, is the most reliable molding process.
Hardness is the ability of a material to resist indentation. For handles that require shock resistance and wear resistance, TPE with adjustable hardness is the first choice.
Tensile Property
It is the ability to resist stretching under temperature and pressure. Some products have tensile resistance requirements, and the tensile ability of the product needs to be tested. Pay attention to this data when selecting materials.
Coefficient of Friction
When two surfaces are dragged parallel to each other, the resistance produced is called friction. The coefficient of friction (COF) represents the amount of force required to move one surface to another.
Wall Thickness
When designing parts, the thickness of the overmolding material should be taken into consideration, as it will affect the molding and shrinkage of the product.
Flexibility is measured by flexural modulus, with a higher flexural modulus generally meaning the material will feel stiffer and less yielding.
Reviews from Our Customers
A customer’s words have a more substantial persuasion than a company’s claims. We have served hundreds of satisfied customers and here are some reviews they give us.
They helped us create a durable overmolded grip for a power tool, and they went through extensive material testing to confirm that nylon would bond well with TPE while still meeting the soft touch and flexibility we needed, and nylon The rigidity of the material ensures long-lasting durability.
David Moon
Vice President
Their expertise in complex overmolding helped us integrate the metal mounting brackets within the device’s housing. Through advanced mold flow analysis and material selection, mold design, etc., they accurately and seamlessly integrate metal inserts into plastic while meeting tight tolerance requirements.
Carl Harris
Pruchasing Manager
After each order is completed, a detailed quality compliance report and material report will be provided. This is also a manifestation of their perfect management, and it also verifies their strength. Fair prices, standardized management, this is the ideal supplier for our overseas buyers.
Tony Jones
Regular communication will allow us to keep abreast of industry trends, and their continuous optimization of design and technology will also provide us with many references. This cooperation model of mutual benefit and trust will continue to improve the technical level of both parties.
Ben Holder
We were deeply impressed by the standardized, spacious and bright factory facilities and safety production rules and regulations. These strict management behaviors reflect their emphasis on occupational health and are also high-quality side verification. We will maintain long-term cooperation in the future.
Anne Zaremba
Our Overmolding Service for Various Industries
Our custom overmolding process is suitable for solve the various demands of industries, including the automotive, medical, electronic & electrical, consumer goods fields etc.
Optical Clear Products
Consumer Goods
Electronic & Electrical
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Overmolding FAQs

What is overmolding?

Overmolding is a process where two or more different materials are molded together to create a single product. It usually has a rigid plastic substrate covered with a flexible rubber-like thermoplastic elastomer (TPE) to provide a soft touch grip.

What information is required for quoting an overmolding project?

You need to provide 3D drawings, materials, colors, expected quantities, etc. Based on this information we will give you an accurate quote.

How long does it take to make an overmolding tooling?

Depending on the complexity and size of the part, we usually take 4 to 6 weeks to complete the overmolding project.

When should I use overmolding?

Overmolding involves injection molding of two or more materials, commonly used to make non-slip handles, or to wrap certain parts (such as magnets) for collision avoidance. If your plastic parts have two or more materials, then over molding process is the ideal solution for you.

Do you have overmolding magnets capabilities?

Yes, we provide the ability to create fully encapsulated magnets using overmolding process. we have more than 10 years of experience in insert molding magnets and overmolding magnets project.

Overmolding magnets refers to the process of encapsulating magnets with plastic through injection molding. In this process, a plastic material is injected into a mold cavity that contains the magnet, and the plastic then solidifies around the magnet, creating a secure and protective encapsulation.

There are many factors to consider magnets overmolding, first, magnet have two poles, magnetism must be considering, because of our mold is steel. second, is all the same poles at a place or different also need considering. third, magnetizing at injection molding before or after must be considering too.

Here is overmolding magnets steps:

  1. Injection molding creating the substrate( usually is TPE)
  2. Assemble the magnet and the substrate plastic parts to form the magnet and substrate components. This step needs to be completed manually.
  3. Manual or servo robot loading magnets and substrate component is placed into the other mold cavity.
  4. The second mold is closed, the molten plastic is formed around the magnet substrate componetns, the magnets are all encapsulated, cooled, and ejected to complete the entire process of magnets overmolding.
Overmolding Resources
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