Blow Moulding Plastic vs Injection Moulding | Moldwel | Injection Moulders

Moulding Plastic

There are several different manufacturing processes to choose from when you are creating a product that requires moulded plastic parts. Depending on what it is that you want to produce, the two most popular processes are plastic injection moulding and blow moulding plastic, they are both used to help to produce high quality, cost effective plastic parts.

We have put together a quick guide that looks at the differences between these two processes:

What is Plastic Injection Moulding?

This manufacturing process consists of injecting liquid polymers at high temperatures and pressure into a steel or aluminium mould. The moulds are then cooled to release the complete plastic parts. There are many unique advantages that plastic injection moulding offers, these include:

  • A efficient and precise manufacturing process for large volumes
  • There is flexibility with regards to the type of material or colour that is used
  • Low waste as plastic can be reheated and used again

Injection moulding is the perfect process for mass production and high-volume orders. Material flow is perfectly controlled thanks to the precise match between mould halves.

Plastic injection moulders will often perform checks that will them to assess the strength, colour, and if there are any common defects like flash or warping. Thanks to the precision of plastic injection mould this makes it more expensive than blow moulding. There are some limitations to injection moulding, these include:

  • High initial tooling cost
  • Part design reconstruction
  • Small runs can be costly

What is Blow Moulding?

Blow Moulding process follows the same basic steps that are found in glass blowing. Blow moulding is designed to produce high volume, one-piece objects that are hollow. For example, if you need to produce a large number of bottles, this is the process for you. This manufacturing process is able to create thin-walled containers that are uniformed.

There are many advantages to blow moulding plastic, they include:

  • Manufacturing and machinery costs are lower compared to plastic injection moulding
  • It is one-piece construction, meaning that there are no connected parts. This meaning it can achieve shapes that injection moulding may not be able to produce.

Blow moulding is done through a plastic tube that is heated and filled with air; it is essentially a balloon of hot plastic which is called a “parison”. Once the balloon is formed, a mould is then clamed around it. This is able to trap the plastic whilst air continues to fill the parison; the heated plastic then takes the shape of your part.

With this process there is more design freedom between the mould halves, this is due to the fact that the moulds form its own wall shape.

There are some limitations to blow moulding, they include:

  • Wall thinning, air leaks, flash and streaks are variables that must be monitored
  • It comes with limited uses
  • It requires process and material precision that can create waste

As mentioned above, blow moulding comes with limited uses as it is restricted to only producing hollow forms; these forms may be, bottles, plastic containers. Air pressure is essential with this process, for example, if the air pressure is too low/high you may experience difficulties with wall thickness.

Here at Moldwel, we operate a lean and flexible manufacturing process that uses the very latest advancements in technology. For more information on our plastic injection moulding process or to make an enquiry, contact us today.


If you enjoyed this article, you might like to read our previous article Plastic Injection Moulding – Benefits and Limitations.