A Quick Guide To Plastic Injection Molding

A Quick Guide To Plastic Injection Molding

As one of the most common and essential methods for producing plastic parts, plastic injection moulding has been used for decades and is still one of the top choices for manufacturing plastic components. How does it work and what processes and phases are involved? What types of plastic are used for injection moulding, and what are the advantages and disadvantages of this method?

In this guide, we’ll walk you through a quick overview of plastic injection moulding so that you can get started with your projects.

What Is Injection Moulding?

Injection moulding is a manufacturing process in which liquid material is injected into a form (or mould), solidifying and taking on that object’s shape. It is used in many applications, including plastic and metal. The process starts with creating a model of the part to be used and then using that model to create a mould. The mould is filled with molten plastic, which is then injected and cooled down.

What Is Plastic Injection Moulding?

Plastic injection moulding is the process of creating plastic parts through the injection of injecting molten plastic into a heated mould. Once the plastic has cooled, it is ejected from the machine and processed further.

How Does A Plastic Injection Moulding Machine Work?

A plastic injection moulding machine consists of a hopper that fills the mould with molten plastic. The hopper is filled with pellets, granules, or chips of various shapes and sizes. As the machine heats up, it melts the plastic into a liquid state before injecting it into the heated mould cavity.

The molten plastic is injected into the mould cavity using an injection unit that forces it through a nozzle and onto the mould. The machine cools the plastic using forced air or water-cooling systems. After solidifying, the finished product is ejected from the machine. It can be used as a raw material for another process.

Plastic Injection Moulding Process & Phases

The plastic injection moulding process has four phases. In this section, we’ll tell you more about them:

1. Designing

It’s the first step in plastic injection moulding. The design process is done using CAD software and consists of creating a 3D model of the part to be produced. The manufacturer uses this model to make moulds for production runs.

2. Prototyping

Prototyping is the creation of a physical model with a similar identity to the final product but is usually made from cheaper materials. This allows manufacturers to test and refine their designs before going into production. Once the design is finalized and approved, it is used to make moulds for mass production.

3. Tooling

Tooling is the process of making moulds, dies, and other fixtures that are used in mass production. This is done using various materials depending on the type of part produced. In plastic injection moulding, a plastic or steel mould is used to make parts. In metal casting, sand is used as the material used in making parts.

4. Testing

Manufacturers will usually perform a variety of tests before mass production begins. These include:

  • Performance tests to make sure the product meets its specifications (such as strength, durability, and safety)
  • Durability testing to ensure that the product will last for an appropriate amount of time under regular use
  • Quality control inspections to ensure that every part meets quality standards

Types Of Plastics Used For Injection Moulding

There are several types of plastics used for injection moulding. The most common types of plastic used for injection moulding include:


Acrylonitrile butadiene styrene (ABS) is a rigid, durable plastic that’s easy to work with and impact-resistant. It’s used in products like car bumpers, computer cases, and toys. It’s one of the most commonly used plastics in injection moulding.


This type of plastic is very durable, making it ideal for usual product applications. It’s also commonly used for parts that need to be transparent or translucent, such as lenses or lights.


Nylon is a high-strength plastic also often used for injection moulding applications. It’s instrumental for parts that need to be lightweight, as it’s much lighter than other plastics.


Polypropylene is a widespread type of plastic that’s used in many applications. It’s often chosen for injection moulding because it has a high melt flow rate, which makes it easier to work with than other materials. It also has good wear and chemical resistance, making it ideal for products regularly handled or exposed to harsh conditions.


Polyethylene is a type of thermoplastic used in many different applications. It can be easily moulded into virtually any shape and doesn’t require moulds or tools to make parts. This makes it an ideal material for injection moulding, especially if you need to make large numbers of parts at once.

Advantages Of Plastic Injection Molding

If you’ve ever wondered if there are advantages to plastic injection moulding, we’re here to tell you there are. The following benefits highlight why you need plastic injection moulding:

Mass production

Plastic injection moulding is an efficient method for producing hundreds or thousands of parts in a matter of hours and requires minimal labour to operate. This makes it an ideal choice for large-scale manufacturing.

Less material wastage

Plastic injection moulding reduces the waste material produced under normal circumstances. But one of the most significant advantages of injection moulding is that we don’t have to worry about waste because the material can be re-purposed or recycled at the end of its life cycle.

Production of complex parts

Plastic injection moulding can produce complicated and detailed parts that would otherwise be difficult to manufacture by other means. It provides a high level of detail and precision, which is especially useful for producing medical devices or other products that require a great deal of accuracy.

High-quality products

Plastic injection moulding ensures products meet the highest standards that are durable, reliable, and easy to maintain. The end product can be modified to meet customers’ specifications so they get what they want.

Low production costs

The plastic injection moulding process requires less labour than other manufacturing methods. It can be used with other processes, such as CNC machining or die casting. This means complex parts can be manufactured without requiring additional costs for tooling.

Disadvantages Of Plastic Injection Moulding

While there are advantages of plastic injection moulding, there are disadvantages, too. The nature of the processes involved results in some disadvantages, including:

High initial costs

Plastic injection moulding is a process that requires significant upfront costs and does require a large number of raw materials. Smaller businesses or startups can find it hard to justify investing in plastic injection moulding when other processes, such as machining or die casting, are less expensive.

Long lead times

Plastic injection moulding takes a long time to complete and requires several steps before you receive your final product. The process is also very dependent on the size of the part being manufactured. It takes weeks or even months in some cases.

Unchangeable moulds

Once you’ve created your mould, there isn’t much you can do to change it or make slight alterations. If your product requires minor adjustments, you must create a new mould for each iteration.

Design and size limitations

Plastic injection moulding is dependent on the size of your product and its design. It’s not the best method for you if you want to make a small, complicated piece that requires many different parts to function correctly. It can be challenging to change any aspect of your product without completely starting from scratch when using injection moulding.


Plastic injection moulding is an essential moulding needed for your mass production. Although it has disadvantages, you can overcome them by finding a suitable injection moulding machine and having it adequately designed.

For a large-scale producer, it’s an essential piece of equipment. It allows for high production rates, which means you can make a lot of parts quickly and efficiently. The plastic injection moulding machines are also relatively simple to operate, so they don’t require much training or experience on your part. Want to learn how to begin? Check here for your next project.

23rd November 2022