Difference Between Vacuum Forming and Injection Moulding

6 Types of Plastic Moulding

There are many different types of plastic moulding available to you, each with their own unique techniques and capabilities and the plastic moulding process you require will depend on your specific product requirements.

What is Plastic Moulding?

Plastic moulding, by definition, is the process of manufacturing plastic parts by shaping liquid or pliable plastic material using a rigid frame commonly referred to as a mould or tool. Plastic moulds may be put to a number of uses, where the following is a list of the most popular and efficient plastic moulding techniques.

Some of the most popular types of plastic moulding consist of vacuum forming, injection moulding, rotational moulding, compression moulding, extrusion moulding and blow moulding. In this article, we will take you through each type of plastic moulding, their purposes and what makes them unique.

1. Vacuum Forming

Plastic vacuum forming is a plastic moulding process that pushes plastic over a mould before using a vacuum to form the product firmly over the mould to achieve greater detail. Vacuum formed products are very common, including products such as plastic utensils, gardening equipment, kitchen appliances and even your bath!

Vacuum forming is ideal for small to large production runs and has uses across the automotive and aerospace industry as well as many others.

Vacuum forming is a common type of plastic moulding, with advantages such as:

  • High detailed outcomes for products with a large size variation.
  • The process is is extremely fast.
  • Because they don’t require massive presses like they would for injection moulding, large items can be produced with lower equipment costs.

What is Vacuum Forming used for?

Vacuum forming is used by a significant number of businesses to create a variety of plastic based products. This type of plastic moulding is used to manufacture automotive products and industrial components, in addition to this, vacuum forming is also used to produce food packaging due to its compatibility with food-grade plastic. Other products created from vacuum forming consist of:

2. Injection Moulding

The injection moulding process typically uses a plunger to force molten plastic material into a mould in order to create specific components. Custom moulds are made so that the melted plastic can instantly injected into the plastic mould, which is followed by intense pressure to ensure the mould is full and a solid part is created. To keep the plastic’s shape, the mould is left to cool once filled, similarly to how you fill a tray of water to freeze into ice cubes.

This type of plastic moulding has a number of advantages to shout about:

  • Cost effective
  • Highly repeatable
  • Can create large numbers per hour
  • Large choice of plastics to use

What is Injection Moulding used for?

Injection moulding is best used for larger quantities of plastic parts per year – up to 30000 – such as bottle caps, storage containers, toys and other forms of plastic packaging. This is a typical method of plastic moulding for making large sums of plastic components, such those for surgical uses or even car parts.

A product’s production process can also be more flexible to accommodate the needs of engineers or designers. Since they must be built of steel or aluminium for higher strength and durability, the cost of the moulds might be high. Fortunately, like with other processes, as manufacturing volume rises, the price per unit falls quickly.

3. Rotational Moulding

Rotational moulding can also be labelled as roto-moulding. A liquid is placed into a chosen mould and then rotated at a rapid speed, which will then cover the whole surface of the mould evenly and thicken out the walls of the plastic mould. The product will become hollow, where the mould is left to cool down which should allow the liquid plastic to take form and will then be removed from the mould.

Like other methods, rotational moulding has its advantages:

  • Material efficient
  • Very little waste
  • Environmentally and economically friendly
  • Consistent thickness of the products walls
  • Low-cost method

What is Rotational Moulding used for?

This method is best used to create big and hollow parts for products such as car parts, bins, cones, storage tanks, play houses and kayaks to list a few. By using this method of plastic moulding, it allows extra customisations to be made, such as adding bends and signage to the products which can be placed into the mould to change the products end result.

4. Compression Moulding

During this process there is an upper and lower tool which comes together with the molten material in-between, where the excessively high temperatures will ensure a firm structure of the end product. Then a force is placed on both tools to compress the material into the shape of the tool. To finalise the process, the liquid plastic is removed from the mould after cooling to preserve its shape.

Advantages of the compression moulding process consist of:

  • Simple process
  • Good for producing high volume of items
  • Cost-effective
  • Allows for longer fibres to ensure the strength of the material

What is Compression Moulding used for?

When you need to create plastic replacement components for damaged metal pieces, this technique works well for mechanical parts and products of a similar nature. This is because the high-temperature process results in a very robust and long-lasting final product.

Despite the material being plastic, the metal pieces can still be replaced with it at a lower cost. This moulding technique’s cost-effectiveness is influenced by things like the complexity of the design, the number of crevices and the surface’s appearance.

This technology is perfect for large production because the cost per part is so low, making this method of plastic moulding very cost-efficient.

5. Extrusion Moulding

In this plastic moulding technique, the material is driven down a tube, called a barrel while under extreme heat. It is driven down the tube by a screw and at the end of the barrel it is driven through a die of the required shape to give you a finished length of part.  UPVC window frames are a prime example of what can be manufactured through this process.

Advantages of extrusion moulding include:

  • Low cost
  • Low machine down time
  • Environmentally and economically friendly
  • The capacity to accurately and continuously create lengthy tubular components.

What is Extrusion Moulding used for?

Your finished product will always be the same shape when applying this procedure along its whole length. These could be objects like PVC pipes or straws. These parts can be produced in very high volumes because the same shape may be produced indefinitely. The drawback of this approach is that it severely limits the kind of pieces you may create. In contrast, this method of moulding is less expensive because the machinery is relatively straightforward and capable of high production.

6. Blow Moulding

The parts manufactured with this method may resemble the finished look of a rotational moulded part. This is due to the molten plastic being blown into a closed cavity tool and then pressure applied for it to line the side walls of the tool. The machine heats up the plastic until it is liquidised and air is pumped into it, which is followed by the plastic being blown into a moulded shape. The mould containing the liquid plastic is left to cool and form its shape, meaning that this process can be extremely quick.

Blow moulding has many advantages to influence its use, such as:

  • Low costs
  • High productivity levels
  • Can produce various products
  • Can mould complex parts

What is Blow Moulding used for?

The majority of products including plastic bottles, drums, cases, and even gasoline tanks are made via blow moulding. With mould costs that fall between rotational moulding and injection moulding, this is a quick and affordable choice, which can also create multiple products at a single time, making the method extremely productive.

Get in Touch

In need of an efficient plastic moulding service? Our team can help in every step along the manufacturing process. Whether you’re looking for advice on the best method to use or for a tooling and moulding service, Ansini can do it. Contact us today to arrange a free consultation with us or call us on 01623 812333 or email info@ansini.co.uk.

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