What Does Insert Molding Mean?

The process of insert molding includes putting an insert, usually made of metal or another material, inside molten plastic to make a single part that fits together perfectly. By combining the good qualities of different materials, this method is often used to make items work better and last longer.

A Brief History of Insert Molding and How It Has Grown

The injection molding method, which goes back to the late 1800s, is where insert molding got its start. The method changed over time as companies looked for ways to add extra parts straight to molded plastic parts, so they didn’t have to do as much secondary assembly. Over the years, improvements in materials, molding techniques, and technology have made insert molding much more accurate and efficient.

How and why it’s important in modern manufacturing

There are several important reasons why insert molding is important in current manufacturing:

  • Better Product Strength and Durability: Manufacturers can make parts that last longer and can handle more mechanical stress by putting strong pieces inside plastic parts.
  • More efficient assembly: insert molding gets rid of the need for assembly after casting, which cuts down on production time and labor costs.
  • create Flexibility: This process makes it possible to make complex geometries and combine multiple functions into a single part, which opens up more creative ways to create products.

Because of these advantages, insert molding is widely used in many fields, such as automobiles, medical devices, consumer electronics, aerospace, and more. It is a useful method in the manufacturing industry because it can make parts that are of high quality, reliable, and affordable.

How Insert Molding Works: The Basics

A Look at the Process

1.Getting the insert ready

The insert is made exactly according to the design instructions. It can be made of metal, plastic, clay, or another material.

Surface treatments or coatings can be put on the insert to make it stick to the plastic better or to give it certain functional qualities.

2.Putting the Mold’s Insert in Place

The ready insert is put into the mold cavity. Often, automated machinery is used to make sure the insert is set and lined up perfectly.

The mold is made to keep the insert firmly in place during the drilling process so that it doesn’t move or get out of place.

3.Putting the plastic in

The mold hole is filled with molten plastic, which surrounds and encloses the insert.

The injection factors, like temperature, pressure, and speed, are carefully managed to make sure that the plastic flows and bonds well with the insert.

4.Getting cooler and ejection

Once the plastic has filled the mold, it is left to cool and harden, which makes a strong connection between it and the insert.

As soon as the part is cool enough, it is ejected from the mold. Usually, automatic ejection systems are used to keep the part consistent and avoid damage.

Insert molding

Insert Types That Are Used

1.Metal Pieces

Steel, brass, and aluminum are metals that are often used.

Metal inserts make the end product stronger, more conductive, and less likely to wear down.

2.Plastic Pieces

Plastic inserts are used when characteristics like being light or not conducting electricity are needed.

A lot of the time, they are made from high-performance industrial plastics that can handle being molded.

3.Ceramic Parts

Ceramic plates are great at keeping heat and electricity from moving through them.

For tasks that need to be stable and resistant to heat, they are used.

4.Various Other Things

As inserts, other materials like glass, rubber, or composites can be used, too, based on the needs of the application.

Compared to the old way of doing injection molding

  • Injection molding as we know it

The part is usually made of plastic and is made from a single material in standard injection molding.

After the part has been molded, inserts or other parts are often added in extra operations. This can make the production process take longer and cost more.

  • Put in the molding

Insert molding uses more than one material and part in a single casting process, so there is no need for extra assembly.

This makes the production process run more smoothly, the quality of the parts is better, and costs may go down.

By knowing and following these basic rules, manufacturers can use insert molding to make innovative, high-quality products that last a long time in many different fields.

Things that are used for insert molding


1.Most Thermoplastics

Polyester (PP) is cheap, flexible, and doesn’t react with chemicals.

Acrylonitrile Butadiene Styrene (ABS): It is tough, doesn’t break easily, and can be machined well.

Polycarbonate (PC) is known for being clear and strong when hit hard.

Polyamide (Nylon): This material is valued for being strong, resistant to wear, and stable at high temperatures.

Polyethylene (PE) comes in two types: high-density (HDPE) and low-density (LDPE). Both are known for being flexible and resistant to chemicals.

2.Why thermoplastics are good

Reusability: It can be fired up and shaped again and again.

Variety: Comes in a lot of different sizes and forms to meet the needs of different projects.

o Because they are easier to work with, they usually need lower temperatures and faster cycle times than thermosets.

Using heat to set plastics

1.Most Thermosets

Epoxy is known for being very strong, chemically resistant, and good at sticking things together.

Phenolic: It is very resistant to heat, stays the same size, and is good at blocking electricity.

o Urea-Formaldehyde (UF): This is used in situations where the surface needs to be very hard and not scratch easily.

2.Why thermosetting plastics are good

Heat Resistance: It can handle higher temperatures without changing shape.

Durability: They usually have better chemical and mechanical qualities than thermoplastics.

Dimensional Stability: They don’t get soft when reheated; they keep their shape and structure.

What kinds of materials can be used for insert molding?

1.Properties of Matter

A high tensile and compressive strength is needed to make it through the casting process and the conditions of use.

o Enough toughness and flexibility to keep it from cracking or breaking while shaping and afterward.

2.Properties of Heat

The melting point should be right for the temperatures used in the casting process.

o Stable under thermal cycles to keep it from breaking down or changing shape.

3.Chemical Strength

o Resistance to chemicals and weather factors to make sure it lasts a long time and works well in a variety of situations.

4.Properties of Adhesion

Good adhesion between the insert material and the plastic to make sure the finished product has a strong bond and stays together.

How to Choose the Right Insert Materials

1.Ability to work with plastic

Make sure that the material used for the insert can handle the heat and chemicals that are used in the casting process.

To avoid stresses and deformation, you should think about the shrinkage rates and thermal expansion factors.

2.Needs for the Application

Find out the exact needs of the final use, like how much weight it can hold, how it will be exposed to the environment, and whether it needs to be electrically or thermally conductive.

o Choose materials that meet these needs while keeping cost and function in mind.

3.Ability to make

Check how easy it is to make and work with the insert material, such as when it comes to machining, finishing the surface, and moving it around during the casting process.

4.Thoughts on Costs

o Compare the cost of the materials to the improvements in performance to find a solution that is both cost-effective and high-quality.

Manufacturers can make insert-molded goods work better, last longer, and cost less by carefully choosing the right materials for both the inserts and the plastic around them.

Different ways to use insert molding

Injection mold China

Vertical Molding With Inserts

1.A Look at the Process

In vertical insert molding, the mold is placed vertically, and the injection unit is placed on top of the cast.

Inserts are put into the mold either by hand or automatically, and then the cast closes around them.

Plastic that is still melted is poured into the mold to cover the inserts.

As soon as the plastic cools and hardens, the mold opens up and the final part falls out.

2.The pros

o It’s easier to place plugs because gravity helps.

It works well for over mold and making small to medium-sized parts.

It works great for automated systems and production lines that never stop.

3.How to Apply

Connectors and parts for electricity.

o Medical tools.

o Electronics for consumers.

Molding with a horizontal insert

1.A Look at the Process

In horizontal insert molding, the mold is laid out flat on the work surface, and the injection unit is placed next to it.

The inserts are put into the mold either by hand or automatically.

When the mold is closed, plastic is pumped to cover the inserts.

When the part is cool and solid, the mold opens and the final part falls out.

2.The pros

It works well for bigger parts and more complicated shapes.

oCan be used with regular horizontal injection molding tools.

It makes it easy to connect to automated systems that place inserts.

3.How to Apply

o Auto parts and pieces.

A lot of big mechanical parts.

O Goods for consumers.

Many-Shot Molding

1.A Look at the Process

In multi-shot casting, different colors or materials are injected into the same mold more than once in the same cycle.

Before the first shot, inserts can be put into the mold. Subsequent shots will cover or encase the inserts.

The process can make things that are very complicated and have many layers or materials.

2.The pros

o Brings together the qualities of several different materials into one part.

o Makes the end product look better and work better.

o Cuts down on the need for extra building work.

3.How to Apply

parts made of more than one material.

o Grip and handle overmolded.

o Parts that are both pretty and useful.


1.A Look at the Process

Overmolding is a type of insert molding in which an extra layer of material is formed on top of a part that is already there (the substrate).

The base is put into the mold, and then the overmold material is pumped on top of or around it.

The process makes a strong connection between the base material and the overmold material.

2.The pros

o Adds usefulness, like better grip or better overall looks.

Extra safety or insulation is provided.

o Can be used to make things that do more than one thing.

3.How to Apply

o Handles and grips that feel good to the touch.

It has valves and seals.

o Cases for electronic devices.

Manufacturers can make a lot of different high-quality, long-lasting, and useful parts that meet specific application needs if they know how to use these different insert molding methods. Each method has its own benefits and can be used with different kinds of products and in different kinds of factories.

Pros of Using Insert Molding

Better product durability and strength

1.Integrity of Structure

The general strength and structural integrity of the plastic part are greatly improved by adding metal or other strong inserts.

This means better performance and longer life in tough situations.

2.Ability to Support Weight

Parts made of plastic that are molded in can withstand higher loads and stresses without breaking or deforming.

o Perfect for uses that need a lot of mechanical strength.

Better efficiency in assembly

1.Getting rid of some assembly steps

It is unnecessary to do extra assembly work after insert molding because it combines several parts into a single manufacturing process.

This cuts down on production time, worker costs, and the chance of mistakes happening during assembly.

2.Made manufacturing easier

By cutting down on the number of separate parts and assembly steps, the process makes the supply chain and production workflow easier.

o Makes production more efficient and gets new goods to market faster.

Lowering of the costs of making things

1.Savings on costs

Putting together several parts into one casting process cuts down on the need for extra parts and materials.

o Lowers the cost of production and labor by cutting down on assembly tasks.

2.Cost savings through economies of scale

It is possible to automate and scale up insert molding for high-volume production, which lowers the cost per unit even more.

Makes it more cost-effective to make a lot of things.

Flexibility in design

1.Patterns with Many Parts

It makes it possible to make complicated parts out of more than one material, which would be hard or impossible to do with traditional molding methods.

Allows for creative product designs that have multiple functions built in.

2.Inserts that can be changed

Inserts, like threaded inserts, conductive elements, or reinforcing structures, can be changed to fit the needs of a specific application.

allows for design and material choices that are more open.

Putting together several different parts

1.Integration of Functions

It combines different materials and parts into a single part that fits together well, making it more useful overall.

o Perfect for products that need to integrate electrical, thermal, or mechanical parts.

2.Less number of parts

Insert molding makes it easier to design products and lowers the chance that a part will break by reducing the number of separate parts.

Makes the final product more reliable and better at what it does.

Better performance

1.Properties of Heat and Electricity

Inserts made of metal or ceramic can improve the thermal and electrical properties of plastic parts.

Useful for situations where heat needs to be drained or electricity needs to flow.

2.Resistance in the Environment

Insert molding can make something more resistant to things like chemicals, water, and changes in temperature.

o Makes the product last longer and last longer in harsh conditions.

Better looks and comfort for users

1.Ends of Surfaces

The process makes it possible to have smooth, aesthetically pleasing surface finishes, even when inserts are used.

o Makes consumer products look better and make using them more enjoyable.

2.Ergonomic Plans

Overmolding can be used to give products soft-touch surfaces or ergonomic features that make them more comfortable and easy to use.

For consumer goods, medical devices, and hand tools, this is important.

By taking advantage of these benefits, insert molding gives companies a flexible and quick way to make high-quality, long-lasting, and inexpensive parts for a lot of different uses.

Problems with insert molding and its limits

Possible movement of the insert

1.Put in Displacement

The high pressure of the molten plastic can make the insert move or shift inside the mold during the injection process.

Misalignment can lead to broken parts that affect how well the final product works and how it looks.

2.Putting the Insert in Place

To keep the insert securely in place during molding, the mold needs to be carefully designed and may need extra supports or fixtures.

o Makes designing and setting up the mold more difficult.

China mold maker

Longer cycle times

1.Longer cycles of production

Putting inserts into the mold carefully and making sure they are lined up correctly can make cycle times longer than with standard injection molding.

Cycle times that are too long can make production less efficient and cost more.

2.Time to Cool

Inserts made of metal or other materials can slow down or speed up the cooling process of plastic, which could make it take longer to cool.

It can take even longer to make something when it needs to cool down for a long time.

Mold Design That Is Too Hard

1.Design of an Intricate Mold

Molds for insert molding are harder to make than molds for regular injection molding because they need to be able to fit inserts.

Molds need to be made so that they can hold inserts securely and let the plastic flow around them properly.

2.More expensive tools

Mold design is getting more complicated, and high-precision molds are needed. This can make the initial cost of tooling go up.

A bigger initial investment could be a problem for startups or small-scale production.

Problems with Material Compatibility

1.Mismatch in Thermal Expansion

Different rates of thermal expansion between the insert material and the plastic can make the interface stressed and even cause it to break.

These problems can be kept to a minimum by carefully choosing the materials and design.

2.Glue and Bonding

Getting the insert to stick well to the plastic can be hard, especially when using certain combinations of materials.

To get better bonding, the surface may need to be treated or coated, which makes the process more difficult and costs more.

Checking for quality and quality control

1.Problems with Inspection

Because insert-molded parts have inserts inside them that you might not be able to see, inspecting them can be harder.

Advanced inspection methods, like X-ray or ultrasonic testing, are needed to make sure that inserts are intact and in the right place.

2.Finding Cracks

Finding flaws caused by incorrect insert placement or bonding issues can be harder and might need special tools.

It can be harder to make sure that the quality of each production batch is the same.

Not much design freedom

1.Limitations on Design

Needing to make room for inserts in the mold can limit the design options, making it harder to change the shape and features of the part.

Design engineers have to carefully weigh the pros and cons of insert molding to find the best solution for each part.

2.Limitations on where to insert

The design of the mold and the injection process may make it hard to put inserts in certain places, which limits the ways that inserts can be integrated.

To place inserts in complicated ways, you may need to use advanced mold design and production methods.

By knowing about and working around these problems and restrictions, manufacturers can make the insert molding process work better, make better parts, and make production more cost-effective. To get around these problems and use the benefits of insert molding, you need to carefully plan, use advanced mold design, and carefully check the quality of your work.

How Insert Molding Is Used

The auto industry- and there are many aluminum casting parts are used for insert molding, you can go to die casting mold page to know more about die casting.

1.Parts for electrical systems

Plastic housings are often used to protect inserts like connectors, terminals, and sensors.

o Makes things last longer, keeps electricity from flowing, and is resistant to vibrations and environmental factors.

2.Parts of the interior

Metal or plastic inserts are molded on top of the panels, knobs, handles, and decorative trim.

Makes interior parts look better, last longer, and be more comfortable to use.

3.Parts that go under the hood

There are places in engine compartments for mounting brackets, fasteners, and sensor housings.

High temperatures, chemicals, and mechanical stresses don’t hurt it.

Medical Tools

1.Instruments for surgery

Antimicrobial materials are molded into the handles and grips to keep them clean.

makes it more comfortable to use and easier to clean.

2.Devices for delivering drugs

o Inserts for needles, syringe plungers, and drug tanks in insulin pumps and other devices.

Makes sure that the right dose is given and that the patient is safe.

3.Tests and Diagnostics

o Overmolded parts make diagnostic tool housing, grips, and buttons last longer.

o Is designed to be ergonomic and easy for healthcare professionals to use.

Electronics for consumers

1.Devices for Hands

Making housings, buttons, and grips for smartphones, remote controls, and game controllers.

Improves the comfort, durability, and looks of the product.

2.Technology You Can Wear

smartwatches and fitness trackers have places for connectors, sensors, and batteries.

Offers designs that are comfortable, light, and long-lasting.

3.Other parts of a computer

Making keyboards, mice, and other gaming accessories’ keys, grips, and housings out of molds.

Makes computer accessories easier to use, look better, and last longer.

The military and space

1.Electronics for aircraft

o Places for antenna housings, connectors, and switches in aircraft instrumentation panels.

o Allows for dependability, protection against electromagnetic fields, and resistance to harsh environmental conditions.

2.Tools for the military

Making housings, handles, and grips for guns, tactical gear, and communication devices out of molds.

Offers toughness, ergonomic design, and the ability to combine several functions into one.

Applications in Industry

1.The tools and equipment

Places for handles, grips, and control panels in machinery and tools for industry.

Makes the job easier, lasts longer, and keeps workers safer in harsh industrial settings.

2.Cases for electronics and electricity

o Electrical enclosures have places for mounting brackets, cable glands, and connectors.

Protects against moisture and dust, makes assembly safe, and makes maintenance easy.

Other Business Types

1.Manufacturer of Toys

Covering grips, buttons, and decorative parts in toys and game accessories with plastic.

Makes children’s products safer, last longer, and look better.

2.Cellular phones

There are inserts for connectors, strain reliefs, and housings in telecommunications gear.

Makes sure that the connection is stable, that it lasts, and that it can handle environmental factors.

Insert molding is very useful and is used in many different fields to make high-quality, long-lasting parts that work. It has benefits like better product performance, lower assembly costs, and more design flexibility, which makes it a popular way to make things for the majority of uses.

Things to Think About When Designing Insert Molding

Placement and alignment of inserts

1.Placement with precision

o Make sure the inserts are placed correctly in the mold so they don’t move or become misaligned during the molding process.

Use automated insertion systems or fixtures to make sure that the parts are always in the same place.

2.Find your way and orient yourself

o Place inserts in the mold so that the part works best and is easiest to put together.

o Think about how the part is oriented to get the best flow of molten plastic around the inserts and even distribution of the material.

Making molds and tools

1.Features for Holding In Inserts

Use undercuts, grooves, or ribs in the mold to keep the inserts in place securely while they are being injected.

Makes the insert more stable and stops it from moving.

2.Where the gate is

Place gate(s) in the mold to help the plastic spread out evenly around the inserts.

Cut down on flow lengths and make sure the mold cavity is fully filled.

3.Air flow

o Make sure the mold has enough vents to let air and gases escape during injection molding.

oKeeps the area around inserts from having holes, air pockets, or incomplete filling.

Compatibility of Materials and Bonding

1.Preparing the Surface

Use adhesion promoters, primers, or surface roughening on the insert surfaces to help them stick to the plastic better.

o Make the insert-plastic interface stick better and last longer.

2.Choice of Materials

o Choose insert materials that work with the plastic’s melting point, shrinkage rate, and mechanical properties.

o Think about thermal expansion coefficients to keep stresses and possible part distortion to a minimum.

Stresses from heat and force

1.Plan for controlling temperature

Take into account the inserts’ thermal conductivity and heat dissipation properties to keep them from getting too hot or warping during the molding process.

Ensure that the part cools evenly and that thermal differences are kept to a minimum.

2.Mechanical Distribution of Load

Spread the mechanical loads out evenly across the part to keep stress from building up around the inserts.

o Improve the strength of the structure by finding the best part geometry and wall thicknesses.

Testing and Making Prototypes

1.Validation of the prototype

o Make a prototype and test it to make sure the insert design, placement, and molding parameters are correct.

o Figure out possible problems early on in the development process and make the design work best for production.

2.Checking for Quality

To make sure consistency and dependability, strict quality control measures should be put in place. These should include measuring and testing the materials.

During production, keep an eye on where the inserts are placed, how well they stick, and how well the parts work.

Assembly and Work Done After Molding

1.Plan for Putting Together

Combining several parts into a single insert-molded part can make the assembly process easier.

Cut down on extra work to save time and money on assembly.

2.Easy access and good service

o Include features that make it easy to get to inserts or parts for repairs and maintenance.

Think about how the part needs to be taken apart and put back together without damaging it.

Engineers and designers can make the insert molding process work better by carefully thinking about these design aspects. This will help them make high-quality, useful parts that meet performance needs and cost-effectiveness goals. For insert molding to work in a variety of situations, the design, tooling, and manufacturing teams must be able to work together well.

In conclusion, insert molding is a flexible and effective way to make things. During the molding process, inserts made of metals, plastics, ceramics, or other materials are pressed into plastic parts. This method has many benefits across many industries, such as making products last longer, making assembly more efficient, and lowering the cost of making things. Insert molding makes it possible to make complex shapes, functional integration, and customization options that are hard to do with traditional molding methods because it uses multiple materials and parts in a single step.

But insert molding does have some problems, like making sure the inserts are placed correctly, dealing with thermal and mechanical stresses, and making sure the materials work together. To get the best quality and performance from the parts, these things need to be carefully thought through during design, mold preparation, and production. Insert molding is becoming more and more useful as materials science, mold technology, and quality control improve. This makes it a popular way to make high-performance parts for the medical, consumer electronics, aerospace, and industrial sectors.

New developments in insert molding are expected to make it even more useful, long-lasting, and efficient in a wider range of industries in the future. As companies keep improving their methods and using new technologies, insert molding is still one of the most important ways to meet the changing needs of the market for strong, useful, and inexpensive plastic parts.

SINCERE TECH is one of top 10 plastic injection molding companies and aluminum die casting manufacturers in China, if you are looking for any type of injection molding service, contact us.