November 15, 2025

Different Types of Injection Moulding Explained

Injection molding has become one of the most extensively used manufacturing processes across industries, including automotive, electronics, consumer goods, and packaging. It enables manufacturers to make complex and precise plastic parts in quantity efficiently and economically.

To really understand how this process works and how different types of injection molding influence production, it’s important to start with the basics.

What Is Injection Molding?

Injection molding is a process of manufacturing whereby molten material, often plastic, is injected into a mold cavity in the making of parts both small and large.

After cooling and solidification, the material takes the form of the mold to produce a finished product.

The injection molding process is ideal for mass production because it ensures consistent quality, tight tolerances, and minimal waste. The uses are endless-from everyday items like bottle caps or toys to complex automotive parts. Injection molding offers both precision and efficiency.

Leading global companies in this field, like Chem-Trend, develop and provide innovative solutions and release agents enabling higher efficiency of the injection molding process, such as improvements in part quality, surface finish, and mold longevity.

Understanding the Injection Moulding Process

Before looking at the different types of injection molding, it’s essential to understand how the basic injection molding process works.

Material Feeding

Plastic pellets, or other molding materials, are fed into the hopper of the machine.

Melting

The pellets are heated inside the barrel until they melt into a uniform molten state.

Injection

The liquid material is injected under high pressure into a correctly designed mold cavity.

Cooling

After injecting, the material cools down and solidifies, taking the exact form of the mold.

Ejection

Once solidified, the finished part is ejected from the mold, ready for trimming or post-processing.

Temperature, pressure, and cooling rate are some of the most influential factors upon which product quality and consistency depend in every stage of production.

Advanced mold release agents and purging compounds by Chem Trend maintain efficiency and minimize downtime between cycles for smooth operations.

Common Injection Moulding Materials

Material selection for injection molding will be critical in realizing the desired properties of the final product. Different applications need materials whose resistance, strength, and flexibility will vary.

Some of the most commonly used injection molding materials include:

PP (Polypropylene): Lightweight and tough, used in packaging and consumer goods.
Acrylonitrile Butadiene Styrene (ABS): With strength and resistance to impact, it is suitable for automobile and electronic parts.
Chemical resistance and flexibility are excellent. Applications include containers and tubing.
Polystyrene (PS): Rigid and transparent, commonly used in household products.
PA (Nylon): Tough; high mechanical strength; used in gears and other industrial parts.
Polycarbonate: The material is of high impact resistance and clarity, applied mainly in lenses and safety equipment.

Each material differs in the temperature at which it melts, cools, or exhibits flow characteristics-all affecting the injection molding process. Chem Trend supports manufacturers with tailored solutions to manage challenges such as material buildup, part sticking, or inconsistent ejection.

Different Types of Injection Moulding

Now that the basics are clear, let’s explore the various types of injection molding used in modern manufacturing. Each type offers unique advantages depending on the product requirements and material characteristics.

Thermoplastic Injection Moulding

This is the most common and widely used type of injection molding. It uses thermoplastic materials that can be melted, shaped, and cooled repeatedly without significant chemical change.

Chem Trend provides high-performance release agents specifically designed for thermoplastic molding, ensuring minimal residue and superior part release.

Thermoset Injection Moulding

Unlike thermoplastics, thermosetting plastics undergo a chemical change when heated, becoming permanently hard. Once set, they cannot be remelted or reshaped.

This method is often used to create heat-resistant and rigid parts for applications in electrical, automotive, and industrial sectors. Epoxy, phenolic, and melamine resins are common injection molding materials for thermoset molding.

Overmolding

Overmolding involves injecting one material over another, for example, a soft rubber-like layer over a rigid plastic substrate. This process enhances grip, comfort, or aesthetics.

It’s commonly used for tool handles, toothbrushes, or electronic devices where different materials are combined for functionality and design appeal.

Effective use of overmolding requires compatibility between the base and the overmolding materials.

Insert Moulding

In this method, preformed components (like metal parts, screws, or electrical contacts) are inserted into the mold before injecting the plastic. Once molded, these inserts become a permanent part of the finished product.

Insert molding is widely used in medical devices, automotive parts, and electronic assemblies. It enhances part strength and reduces assembly steps.

To ensure precise mold release and prevent component shifting, manufacturers often rely on Chem-Trend’s specialized release agents for consistent results.

Micro Injection Moulding

Micro injection molding is designed for producing extremely small and precise components, often weighing less than a gram. It’s popular in the medical, electronics, and micro-mechanical industries.

Due to the minute size of the parts, this process demands high precision and advanced machinery.

Gas-Assisted Injection Moulding

In this process, pressurized gas (usually nitrogen) is injected into the molten plastic after it fills the mold partially. The gas pushes the material to the edges, creating hollow sections and reducing part weight.

Gas-assisted molding reduces material usage and prevents defects like sink marks or warping. It’s perfect for large, lightweight components such as automotive panels or handles.

Co-Injection Moulding

Also known as sandwich molding, this process involves injecting two different materials simultaneously; one forms the outer skin, while the other creates the core.

Co-injection molding enhances part strength, aesthetics, and cost-efficiency by using high-quality outer materials and economical core materials.

Reaction Injection Moulding (RIM)

RIM uses liquid reactants (such as polyurethane) that chemically react inside the mold to form the final product. It’s used for large, lightweight, and durable components, such as automotive bumpers and enclosures.

The low-pressure process allows for greater design flexibility and lower tooling costs.

To wrap up

The world of injection molding is truly vast, and each method serves a distinct purpose for different design, functional, and production needs. From thermoplastic and thermoset moulding to the advanced methodologies of micro- and gas-assisted molding, selection of the appropriate method can significantly affect quality, cost, and efficiency.

Companies like Chem-Trend play a vital role in supporting manufacturers through every stage by offering premium release agents, purging compounds, and process aids that improve productivity, surface finish, and sustainability.

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