If you’re looking for an injection moulded products manufacturer, it can be confusing knowing what you need to take into consideration to make sure you choose wisely. The internet is a great source of information to help you, but sometimes you get pulled from pillar to post, not knowing who is telling you the truth.

The truth is – the injection moulding process is complex

The injection moulding process is complex if you’re new to it. Making the right decision about who to choose as your trusted supplier and cutting through the noise on the internet about injection moulding can be a tough challenge. In this article we want to demystify the difference between the two different types of machine used in the injection moulding process and share with you the machine we use at Plastech and why.

Hot and cold runner moulds

While there are dozens of different machine brands and machine specifications, there are essentially two types of machine used for injection moulding and the difference comes down to the runners. They are hot and cold runner machines.

Cold runner moulds

Cold runner moulds usually consist of two or three plates that are held within the mould base. The molten thermoplastic is first injected into the mould from a nozzle via the sprue, which fills the network of runners that lead to the mould cavities.

In this system, the runners are unheated (as the name suggests) and act as a delivery system that distribute the molten plastic to the individual moulding cavities. The cold runner system subsequently cools the sprue, runner, and gate along with the moulded part.

Hot runner moulds

Hot runner moulds consist of two plates that are heated with a manifold system. The manifold helps maintain a consistent temperature by keeping the molten thermoplastic in the runners at the same temperature as the heating cylinder. The heated runners deliver the molten plastic to nozzles that fill the core mould to form the final part.

The hot runner process eliminates sprue runners entirely, so recycling and regrind (which can only be done with virgin plastics) do not impact cycle times. Not surprisingly, the primary difference between the two is that hot runners are heated while cold runners are not. While hot runners are not required for injection moulding processes, they can be useful to ensure a higher quality part.

At Plastech we choose quality every time

As quality is at the core of everything we do at Plastech, we choose to use hot runners in our injection moulding process. For more information about the injection moulding process or choosing the right supplier for your injection moulding project, get in touch.