Exploring the Different Types of Plastic Manufacturing Processes

From toys to medical equipment, plastic products are everywhere! But how exactly do these items get made? In this article, we'll be exploring the different types of plastic manufacturing processes and their applications. By the end, you'll better understand the technology behind the products you use daily.

Introduction to Plastic Manufacturing

Plastics are made from petroleum products, natural gas, and coal. The process of turning these fossil fuels into plastic is called polymerisation. In this process, long-chain molecules called polymers are created. They can be moulded, extruded, or drawn into different shapes and objects. They are used in various applications, including packaging, construction, automotive parts, etc. The application of plastics is truly endless.

Types of Plastic Manufacturing Processes

Plastic manufacturing processes can broadly be classified into two categories:

1. Thermosetting plastics
2. Thermoplastic plastics

Thermosetting plastics are materials that solidify when heated but cannot be melted and reformed. In contrast, thermoplastics can be melted and reformed repeatedly.

The most common type of plastic manufacturing process is injection moulding, which is used to produce a wide variety of products, including food containers, bottle caps, toys, and more. This procedure involves injecting molten plastic into a mould, which cools and solidifies to fit the cavity.

Another popular manufacturing process is extrusion, which creates long continuous shapes like pipes or tubing. In this process, plastic material is forced through a die (a metal plate with a hole) to create the desired shape.

Other less common plastic manufacturing processes include blow moulding (used to make hollow objects like bottles), rotational moulding (used to create hollow objects with complex shapes), and thermoforming (used to create thin sheets of plastic that can be moulded into various shapes).

Now let's explore each of these moulding procedures in more detail.

Injection Moulding

Injection moulding is a plastic manufacturing process that involves injecting molten material into a mould cavity. The material is then allowed to cool and solidify before removal from the mould. Injection moulding is widely used for producing parts and components of various sizes and shapes.

Production of complex parts with detailed designs is one of the main advantages of injection moulding. Injection moulding also has a high production rate and can be automated, which reduces labour costs. Additionally, injection moulded parts typically have a high degree of dimensional accuracy and consistency.

Disadvantages of injection moulding include its high initial investment cost and the need for specialised equipment and trained personnel. Injection moulded parts generally have a lower strength-to-weight ratio than other plastic manufacturing processes such as extrusion or thermoforming.

Extrusion Moulding

Extrusion moulding is a technique used in the production of plastics that involves pushing molten plastic through a die to produce a certain form. This process is commonly used to create long, straight objects such as pipes, tubing, and rod stock. Extrusion moulding is typically performed using a screw-type plunger that forces the molten plastic material through the die. The speed of the screw and the temperatures of the barrel and die are carefully controlled to ensure that the plastic material is properly melted and extruded. After the desired shape has been extruded, it is cooled using water or air before being cut to length. Extrusion moulding is a continuous process, meaning that once it has been set up, it can produce large quantities of identical parts quickly and efficiently.

Blow Moulding

Blow moulding is a plastic manufacturing process that involves inflating a molten plastic tube until it forms the desired shape. This process is often used to create hollow objects, such as bottles and containers.

There are two main types of blow moulding: Injection blow moulding and extrusion blow moulding.

• Injection blow moulding

The clamping and injection units are the two main components of injection moulding machines. Injection blow moulding, also known as IBM, is a type of injection moulding process that employs a metal shank or core rod. The process employs a parison as the foundation for the finished product. The IBM process begins with transferring the parison/core rod into the machine's blow moulding unit, then inflating and cooling the pre-formed part. After cooling, the core rod is rotated to the ejection position, the mould is opened, and the product is removed. Three core rods are used throughout the process to facilitate mould injection, blow moulding, and ejection of the formed part.

• Extrusion blow moulding

Extrusion blow moulding, or EBM, is similar to IBM in that the material is extruded or expelled into a hollow tube known as a parison rather than injected into a mould. While at the blow station, a mould closes around the parison to shape the part. Air is blown into the prison at the blow station, inflating it to the shape of the mould. After the plastic has cooled, the mould is opened, and the part is extruded. Any surplus material is removed from the finished product. Because of the EBM process, a high level of scrap is typically produced.

Rotational Moulding

Rotational moulding is a plastic manufacturing process typically used for creating large, hollow objects. It is often used for kayaks, playground equipment, and large storage tanks.

The rotational moulding process begins with a powder or liquid resin being placed into a mould. The mould is then rotated in an oven, causing the resin to melt and coat the inside of the mould. Once the resin has cooled and solidified, the mould is opened, and the finished product is removed.

Rotational moulding offers several advantages over other plastic manufacturing processes. It is a relatively low-cost manufacturing process.

Compression Moulding

Compression moulding is a plastic manufacturing process in which thermoplastic material is placed into a heated mould cavity and allowed to cool and solidify. The process is well-suited for the high-volume production of parts with complex shapes. Compression-moulded parts can be very strong and have a smooth surface finish.

Thermoforming

A plastic sheet is heated during the thermoforming process to become sufficiently soft and moulded into the required shape. The heated plastic sheet is placed over a mould and cools and hardens into the desired shape. Thermoforming is commonly used to create packaging, such as food containers or drink cups.

Learn about Manufacturing with Skill-Lync

By understanding the various characteristics of each method, you will be able to select the right process for your application and ensure that it meets all of your requirements. Skill-Lync's Manufacturing course provides students with an understanding of the different types of plastic manufacturing processes and the latest manufacturing technologies. Skill-Lync also offers PG on manufacturing design, CAD, and CAE softwares.