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A Simple Guide to Plastic Moulding. Is Rotational Moulding Right for You?

Martin December 12, 2020

With the introduction of technologies and the transfer of knowledge from generation to generation, the Moulding Industry has witnessed significant growth and developed on its own. What is Moulding?

The process in which any material or liquid that is melted, poured into a rigid frame called mould or matrix, and is cooled to form the desired shape, is called moulding. In the engineering world, this process gets usually done with plastic material. Thus, the entire technique is also known as custom plastic moulding.

What is Plastic Moulding?

Plastic moulding got founded in the late 19th century, and since then, it has expanded into many types. In traditional plastic moulding, liquid plastic is poured in a hollow mould and left to harden into a customized shape with the use of external factors such as heat and pressure. The products that we use in our daily routine like buckets, mugs, jars, toothbrushes, etc. are all made using the process of plastic moulding.

Modern technologies have enabled plastic moulding techniques to produce complex shapes and designs, thus, benefitting the automotive and material handling industries.

Types of Plastics used in the Moulding Industry

In the moulding industry, there are primarily two types of widely used plastics-

  • Thermosets

Once they get moulded into the desired shape, thermosets can never be re-melted and re-used, even when exposed to exceptionally high temperatures.

Examples of Thermosets include silicone, epoxy, phenolic, and polyurethane.

  • Thermoplastics

Unlike Thermosets, a Thermoplastic can get re-melted above a specific temperature and re-shaped multiple times accordingly. Thus, Thermoplastics are considered to be more versatile and widely preferred as compared to Thermosets.

Examples of Thermoplastics include polyester, acrylic, nylon, and Teflon.

Types of Plastic Moulding

  1. Injection Moulding

As the name suggests, during the process of Injection Moulding, molten plastic is injected at high pressure into a custom injection mould. The mould is cooled, and the customized shape with the desired design and size gets ejected out. These injection moulds get generally made from steel or aluminium.

Uses of Injection Moulding-

  • To develop everyday products like toothbrushes, mugs, plastic buckets, plastic bottle caps, etc.
  • Automotive Industry to develop auto dashboards/bumpers.
  • Medical Industry to develop surgical equipment.
  • Electrical Switches
  • Blow Moulding

Blow Moulding is preferred when the plastic has to have a uniform wall thickness since the end product comes out to be hollow and thin-walled.

During this technique, the machine heats the raw plastic. As soon as the plastic converts into liquid form, the air gets injected into it like a balloon. As the plastic expands, it presses against the mould walls and begins to take the customized shape. After the balloon fills the mould, it is cooled and hardened to maintain the shape. The entire process takes under two minutes to reach completion. Therefore, it can produce over 1400 pieces within 12 hours.

Uses of Blow Moulding-

  • Water Bottles
  • Water Tanks
  • Traffic Cones & Traffic Drums
  • Complex Automotive Fuel Tanks
  • Compression Moulding

In this technique, liquid plastic is poured into a heated mould and then compressed to form the desired end product. The final stages involve cooling the liquid plastic before trimming and removing from the mould. The exceptionally high temperature used in the process ensures maximized strength of the developed product.

Compression Moulding gets commonly used for Thermoset plastics.

Uses of Compression Moulding-

  • Strong & Durable Automotive Parts
  • Hoods & Fenders
  • Scoops & Spoilers
  • Extrusion Moulding

In Extrusion Moulding, a custom made “die” is used instead of a mould. The shape of this die determines the shape of the final product.

During this technique, the hot melted plastic gets pressed through a shaped hole, i.e., a die, which results in the formation of a long, continuous tube-like shape. The extrusion is cooled, and the end product gets ejected.

Uses of Extrusion Moulding-

  • PVC Pipes
  • Hoses & Drinking Straws
  • Curtain Tracks
  • Plastic Gutter
  • Rods & Fibre
  • Rotational Moulding

Rotational Moulding or Rotomoulding is preferred to develop large hollow products with evenly thick walls.

The technique begins by placing a powder or liquid resin into a mould. This mould is then rotated at high speed till the liquid resin covers the walls of the mould. When the mould gets rotated, a centrifugal force gets generated, which results in the formation of evenly thick-walled products. Finally, the mould is cooled down, and the desired shape gets taken out.

Uses of Rotational Moulding-

  • Large Tubs & Containers
  • Storage Tanks & Recycling Bins
  • Marine Buoys & Kayaks
  • Road Cones
  • Car Parts

Is Rotational Moulding Right for You?

There are several reasons why Rotational Moulding is preferred worldwide to create plastic products. Let’s take a look at the benefits of Rotomoulding and whether it suits your business logistics-

  • The moulds that get used in rotational moulding are highly complex to make a diverse range of customizable and changeable products.
  • In Rotational Moulding, the tooling costs are way lower as compared to injection and blow moulding, which results in lower start-up costs.
  • Rotational moulding is the first choice for small businesses in the plastic industry because very little material is wasted during the entire process, thus, making it economical. Moreover, all the excess material often gets re-used, making it environmentally friendly as well.
  • Rotomoulding creates a high strength and highly stable product as the corners of the end product are thicker.

In Conclusion, the most suitable way to decide whether or not rotational moulding will be the right choice for your business is to figure out your annual production volume. If your product is complex, and you require smaller runs per order, Rotomoulding can fulfill your needs. However, if you are not bothered about the tooling cost and are seeking larger runs per order, it is advised to prefer a different form of moulding technique.

There are several companies worldwide that offer plastic moulding services. However, if you are looking for custom plastic moulding in Melbourne or nearby areas, there is none better than Rudplas Rotomoulders.

Rudplas Rotomoulders is an Australian family-owned and operated business involved in the rotational moulding industry for over 25 years. Rudplas specializes in the manufacture of bulk materials handling products, such as industrial trolleys, laundry trolleys, water tanks, etc. All products get manufactured from top quality UV stabilized food-grade polyethylene, which makes their products lightweight, easy to clean, and impact and weather resistant.

You can visit them in Melbourne for custom plastic moulding, or browse their website and contact them further for their services.

About Author


Rudplas Rotomoulders is an Australian family owned and operated business that has been involved in the rotational moulding industry for over 30 years. Rudplas specialises in the manufacture of bulk materials handling products, which includes a large range of industrial trolleys and laundry trolleys. Rudplas also manufactures a selection of water tanks in popular sizes and colors as well as a variety of service station products. At Rudplas, we also have the ability to mould your unique customer based rotational moulded products. Rudplas’ line of products are manufactured from top quality UV stabilised food grade polyethylene. This makes our products light weight, easy to clean and impact and weather resistant. We pride ourselves on working with our customers and the flexibility to modifiy and customise trolleys to best suit individual needs puts the power of choice in the hands of the customer. All of our products are manufactured under ISO 9001:2008 conditions for quality assurance and are backed by our manufacturers warranty. View all posts by Martin →

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