Insert Molding

Insert molding is a technique in which plastic is molded and covered around a core that can be made up of plastic or metal or any other material. Both the layers are connected to each other to make them appear as a single unit.

The entire process will involve combining the metal and the outer plastic cover together to make it a single component. 

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Types of  Insert Molding Process

The process of overmolding and insert molding utilizes similar machinery and materials. Over molding requires more complicated machinery and a complex procedure. Insert molding provides numerous benefits over regular techniques

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Multi-Component Molding

It is a process that involves injecting multiple plastics and metals into a mold at the same time. These materials then combine to form a stiffer, stronger material. this process can be used to create products with intricate designs.  It is commonly used in the automotive industry to create parts that are both strong and lightweight.

Multi-shot Molding

It is a type of insert molding that involves the use of multiple materials to create a single product. In this process, the different materials are inserted into the mold one at a time. The operator then waits for each layer to harden before adding the next layer. This process is used to create products with multiple colors or textures.


Overmolding is a type of insert molding that involves using a preformed part and placing inserts on it. Instead of starting with a mold and molten material, it starts with a preformed part on which the insert is placed. From there, the injection molding layer of plastic is inserted and sealed in place.

Overview of Insert Molding Process

The insert is usually placed in a mold tool or cavity, and then the plastic material is melted and injected into the mold around the insert. The molten plastic then cools and solidifies, forming a finished product that has the insert securely embedded inside.

Mold Making

1. Mold Making

In the initial step, a customized mold is made, This mold could be loaded in insert later on. The mold is customized on the shape and design of the object we want on the product.

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2. Test Mold

The circuit testing could be done to let you know about the accuracy of the mold. Die-cutting and stamping can also be done. Micro soldering and even bonding with different bonding agents can also be used.

Mold Making Process

3. Molding Processing

3. Molding

All the components are separated by sprues and further examined, Sprues act as a reserve for the plastic while the molding process is in function.


4. Demould

The mould is opened before attaching the sprues, and the components are completely removed. The post-molding procedures involve different secondary operations.

How Does Insert Molding Work?

Insert Molding

Insert molding is a manufacturing process that involves combining metal or plastic parts with a molded plastic component to create a finished product.

Here is a step-by-step breakdown of how insert molding works:


The design of the part and the insert are created, and a mold is designed to produce the final product.

Insert placement:

The pre-made insert is placed into the mold cavity or tool.


The mold is closed and held in place by clamps.

Injection molding:

Molten plastic material is injected into the mold around the insert. The plastic material flows around the insert and fills the mold cavity, creating a secure bond between the insert and the plastic.

Cooling and solidification:

The plastic material is allowed to cool and solidify, forming a finished product with the insert securely embedded inside.


The finished product is removed from the mold.

The key to successful insert molding is creating a strong bond between the insert and the plastic material. This is achieved by carefully selecting the materials and process parameters, such as the temperature, pressure, and injection speed. In some cases, the insert may be coated or treated with an adhesive to improve adhesion to the plastic material.

Insert Molding Plastics

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ASB Materials


Acrylonitrile Butadiene Styrene resin is a milky white solid with a certain degree of toughness, with a density of about 1.04~1.06 g/cm3. It has strong corrosion resistance to acids, alkalis, and salts, and it can also tolerate organic solvents to a certain extent. ABS is a resin that has good mechanical toughness, wide temperature range, good dimensional stability, chemical resistance, electrical insulation properties and it’s easy to manufacture.

  • Common applications: Enclosures
Nylon 6 Materials

Nylon 6

Nylon 6, also known as PA6, polyamide 6, is a polymer compound. Except for its low melting point and wide process temperature range, its chemical and physical properties are very similar to nylon 66. Among all nylon grades, nylon 6 has the lowest modulus.

  • Common applications: Enclosures
Nylon 66

Nylon 66

Polyhexamethylene adipamide, commonly known as nylon-66, is a thermoplastic resin. The performance of nylon 6-6 is better than nylon 6, and the price is not as expensive as nylon 4-6. Its abrasion resistance is the best among all nylons, and its mechanical strength, hardness, and rigidity are very high. Can be used as engineering plastics and making synthetic fibers.

  • Common applications: Enclosures
Nylon 11 Materials

Nylon 11

The density of nylon PA11 is 1.04g/cm3, the melting point is 185℃, the water absorption is 0.1-0.4℅, and the tensile strength is 47-58MPa. It has the advantages of low water absorption, good oil resistance, low-temperature resistance, and easy processing. Widely used in our lives due to its good cost performance.

  • Common applications: Enclosures
PBT Materials


Polybutylene terephthalate (PBT), a milky white semi-crystalline thermoplastic polyester, is one of the five major engineering plastics. It has high heat resistance. Not resistant to strong acids and alkalis, resistant to organic solvents, flammable, and decomposes at high temperatures. It is widely used in the fields of automobiles, machinery, and equipment, precision instrument parts, etc.

  • Common applications: Enclosures
PC Materials


Polycarbonate is a high molecular weight polymer containing carbonate groups in the molecular chain. It is a tough thermoplastic resin with flame retardancy. Antioxidant. It has excellent impact strength, transparency, and optical properties, mechanical properties, and can be molded to tight tolerances. PC has a wide range of applications, and there are a variety of compounds to choose from.

  • Common applications: Enclosures
PE Materials


The full name is Polyethylene, which is the simplest polymer organic compound and the most widely used polymer material. According to the density, there are 2 types of PE: LDPE and HDPE. It has good inherent lubricity and is easy to process. It should be noted that it is very soft and cannot be used at a temperature much higher than 150.

  • Common applications: Enclosures
PEI Materials


Polyetherimide (PEI for short) is an amorphous high-temperature super engineering plastic, and its cost is relatively low compared with other high-temperature materials. It has the best high-temperature resistance and dimensional stability, as well as chemical resistance, flame retardancy, electrical properties, high strength, high rigidity, etc. The performance is similar to polycarbonate, but it can work at higher temperatures.

  • Common applications: Enclosures
PE Materials


Low-density polyethylene, also known as high-pressure polyethylene (LDPE), is milky white, odorless, odorless, non-toxic, and waxy particles with a matt surface. It has good electrical insulation, transparency, easy processing, and certain air permeability. And has strong extensibility and flexibility, making it have excellent impact strength. This is offset by the permanent deformation after the impact.

  • Common applications: Enclosures
HDPE Materials


High-density polyethylene (HDPE) is a white powder or granular product. Non-toxic and odorless, the use temperature can reach 100℃. It does not have the impact strength of LDPE, but it is more elastic. Surface hardness, tensile strength, rigidity, and other mechanical strength are higher than LDPE, close to PP, tougher than PP, but the surface finish is not as good as PP.

  • Common applications: Enclosures
PET Materials


Polyethylene terephthalate (PET), milky white or light yellow, is a highly crystalline polymer with a smooth and shiny surface. It is non-toxic, tasteless, and has good hygiene and safety, and can be directly used for food packaging. It has excellent physical and mechanical properties in a wide temperature range, and the long-term use temperature can reach 120°C. But it is difficult to mold to very close tolerances.

  • Common applications: Enclosures
PP Materials


Polypropylene is abbreviated as PP, which is a colorless, odorless, non-toxic, translucent solid substance. The density is about 0.89~0.91g/cm3, and the operating temperature range is -30~140℃. It is difficult to mold to very close tolerances. Widely used in the production of clothing, medical equipment, automobiles, bicycles, parts, pipelines, chemical containers, etc.

  • Common applications: Enclosures
PPA Materials


Polyphthalamide is a kind of synthetic resin with high hardness, high strength, good chemical resistance, and low cost. Due to the excellent physical, thermal, and electrical properties of PPA, especially the moderate cost, it has a wide range of applications. Although the use and introduction of PPA are relatively late, its good design data is still very useful.

  • Common applications: Enclosures
PPS Materials


Polyphenylene Sulfide is a new type of high-performance thermoplastic resin, which has the advantages of high mechanical strength, high-temperature resistance, chemical resistance, flame resistance, good thermal stability, and excellent electrical properties. It is widely used in the fields of electronics, automobiles, machinery, and chemicals.

  • Common applications: Enclosures
PP Materials


PMMA, also known as acrylic, is a tough, highly transparent material with excellent resistance to ultraviolet radiation and weather resistance. It can be colored, shaped, cut, drilled, and shaped. With its beautiful appearance, it has a wide range of applications in the construction industry.

  • Common applications: Enclosures


POM is a crystalline plastic, a density of 1.42g/cm3. It has good rigidity, it is an engineering plastic with excellent comprehensive properties. POM has exhaust problems at high temperatures and is brittle at low temperatures. Glass filled, add lubrication grade available, no flame retardant grade.

  • Common applications: Enclosures
PEEK Materials


Peek (polyetheretherketone) is a kind of special engineering plastic with high-temperature resistance, self-lubrication, easy processing, and high mechanical strength, and other excellent properties. It can be manufactured and processed into various mechanical parts, such as automobile gears, oil screens, gear shift start plates; Aircraft engine parts, automatic washing machine runner, medical equipment parts, etc.

  • Common applications: Enclosures
HIPS Materials


HIPS(High Impact Polystyrene) is a bright and pure amorphous plastic. It has the advantages of easy processing, rigidity, dimensional stability, and transparency, but its low impact strength limits its application. It has a lower modulus, better elongation, and is much more brittle than crystalline styrene.

  • Common applications: Enclosures
PSU Materials


PSU is a relatively low-cost high-temperature amorphous material. It is transparent and has good radiation stability and heat resistance. Can be used at temperatures up to 300 degrees Fahrenheit. Widely used in medical equipment, machinery industry, electronic appliances, and other fields.

  • Common applications: Enclosures
PU Materials


PU(Polyurethane) is an extremely elastic, wear-resistant, and tear-resistant elastic material that can be used in ether and ester-based formulations. These different formulations cover a very wide range of hardness and density.

  • Common applications: Enclosures
TPE Materials


TPE(Thermoplastic Elastomer), also known as artificial rubber or synthetic rubber. It is a kind of elastomer that has the elasticity of rubber at normal temperatures and can be plasticized and molded at high temperatures. It contains thermoplastic and elastomer properties, which makes the product very easy to use in the manufacture of various products. Standard thermoplastic processing equipment and techniques can be used for processing and molding, such as extrusion, injection, blow molding, etc.

  • Common applications: Enclosures
TPU Materials


Thermoplastic polyurethane (TPU) is an elastic material with good oil resistance, grease resistance, and wear resistance. It is also a mature environmental protection material. It is widely used in medical and health, electronic appliances, industry, and sports.

  • Common applications: Enclosures

Notes On Material Selection




Some materials stick together when they are overmolded, while others do not. Perfect combination is the ideal situation.


Since it is overmolded on plastic, the substrate must not deform under the heat and pressure of the molding process.

Tensile property

Most materials of overmolding will have several properties related to tensile strength, elongation, tensile modulus, and so on.

Compression Properties

It may be important for your overmoling project to know how much parts can be compressed without permanent damage.

Friction Coefficient

Friction is the force required to cross one surface over another, The surface texture of the mold is a factor too.


Hardness property is the ability of the material to resist indentation, hardness of different materials vary greatly.

Flexural properties

The bending resistance of a material is the bending modulus. This attribute is the second factor in the “feel” of materials.


From a design point of view, the thickness of the material will change the effectiveness of the material properties.

Applications of Insert Molding

The process of insert molding can be used in various sectors, and here we have listed some of the best applications of the process. 

Auto Parts

Insert molding process is common in the field of automotive interior decoration, especially in the instrument panel airbag area is widely used, and the injection molding process is applied in the instrument panel airbag area.

Military equipment

Military equipment uses reinforced materials to improve strength and resistance. There is a lot of military equipment made up of insert molding techniques that provide efficient stability to the material.

In-mold labeling

In-mold labeling uses printed film in which the molding is done. In this process, the outermost layer, which is made up of reinforced plastic and more such materials, is decorated to get the desired structure.

insert molding Electric components

Electric components

In the insert molding, the core metal or the core substance chosen should be according to what’s required in the electric device. Resistance plays a significant role in such electric devices

insert molding Electronic products​

Electronic products

Insert molding service is often used in electronic products, such as notebook, mobile phone, digital camera, TV, etc. The shells of these products are usually inserted metal parts by insert molding process.

insert molding parts

Encapsulated studs

Different encapsulated tubes are made by the insert molding process. Insert molding can quickly help out in this process. The outer layer of the tubes makes it look fancier, and this could be done quickly by Insert molding.

insert molding services

Knobs and controls

The knobs and controls that are put on different machines are made up of reinforced plastics and metals, The core of knobs is basically made up of solid metals partially covered or even sometimes completely covered with plastics.

insert molding Electric components​

Electric components

Numerous medical devices are also fabricated by the process of insert molding. The process makes up different tube valves and needles. Such as portable measuring instrument,Large inspection equipment

Advantages of Insert Molding Servcies

injection molding surface quality


When the mold design is inserted with the needed metal, it can quickly help in increasing the stability of the entire product.

reucing tooling cost


Plastic parts can make the overall product very light, and on the other hand, when the inner core metal is combined with the plastic cover, it increases the strength.

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Improvement with the size

One can make thinner and smaller products with the same strength and durability and can even get better performance by using insert molding.

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The molding production is much more cost-effective. the assembly cost is low, there is minimal labor cost related to the process.

injection molding surface quality


it is a one doesn’t require manual handling and the entire labor-related process. the efficiency of the process gets better.

reucing tooling cost

Variety of materials

You can use numerous materials and even plastic resins in the entire process of insert molding.

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Variety of designs

The insert molding technique is used to design different parts and models in numerous industries these days.

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Improves the reliability

The reliability of the products produced by the machine used in the process is more significant than all other molding techniques.

Plastic Insert Molding FAQs

A: Plastic Insert Molding is a process used to create components with plastic and metal parts combined. It involves the injection of molten plastic surrounding a pre-made metal insert. Once the plastic cools, it forms around the insert for a finished product that combines both materials’ benefits.

The primary difference between them is that, in overmolding, the plastic material is injected directly onto a molded part or assembly; in insert molding, the plastic is first injected into a cavity and then the finished piece is inserted into another injection-molded part.

A: The insert molding process begins with the creation of a metal insert. This can be done through machining, die casting, or other processes depending on the product’s specifications. The insert is then placed into the injection mold tool before it is closed and secured. Molten plastic is then injected into the mold around the metal part until it cools and solidifies. Once the plastic cools, it is removed from the mold and any necessary finishing is performed before it’s ready to use in product assemblies.

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