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A short guide to injection moulding tooling

clock 6 minutes | 19 Jun 2020

Getting your tooling right means you’ll get more accurate parts

There are many key parts of injection moulding, but the mould tool is the essential element that ensures the final components produced are accurate and high-quality.

As the machine element that shapes and forms the final component, selecting the right mould tool design can have a significant impact on the quality and efficiency of component production.

Whether you’re creating a custom moulding for a new part, or selecting a standard tool provided by your manufacturer, it’s important to have some considerations in mind to ensure you’re making the best choice for your component.

The injection moulding tool is made up of a core and a cavity

What is an injection moulding tool?

An injection moulding tool is typically made up of two halves, the core and the cavity. The cavity is the hollow section of the mould that the molten thermoplastic is fed into and the core is the solid half that fills the cavity to form the final part.

The design of both the core and the cavity will change dependent on the final form and application of the component e.g. whether it’s a cap or a plug. Within one mould tool there can also be cores and cavities available for multiple parts, so more than one component can be created in a single injection moulding cycle.

How does the tool work within the injection moulding process?

Before the injection moulding process begins, the tool is hung in the injection moulding machine which will be relative to the size of the mould (the larger the mould tool, the larger the machine will need to be).

At the beginning of the process cycle, the mould tool closes and clamp pressure is applied. Getting this pressure right is important to make sure the tool isn’t damaged but also that the component is fully formed.

The molten thermoplastic is then injected into the tool before being held under pressure so the part becomes packed and formed within the mould. The tool is also left to cool for a certain period of time.

These hold pressures and cooling times are calculated based on the type of thermoplastic being used and the complexity of the mould tool to make sure the component forms fully and doesn’t have any faults.

Once these hold and cooling times have passed, the mould opens and the parts are ejected from the tool by plates or pins. The mould then recloses and the whole cycle starts again. Dependent on the complexity of the part and type of thermoplastic used, each cycle can take between several seconds and several minutes to complete.

The tool is an integral part of the injection moulding process

What should be considered when choosing a tool?

Whether you’re choosing a standard or custom part, you want it to be as consistent and high-quality as possible. This all starts with your manufacturer choosing the right tool. There are a few elements that need to be considered:

  • The application and environment of the final component. By considering how the final produced component will be used, for what purpose and in what type of environment, you can start to outline the final characteristics it needs to have. This will determine which thermoplastic and which mould tool are used.
  • Prototyping of the mould tool. Particularly if you’re having a custom part made, considering prototyping the part, or having test runs and asking for samples of the components will reassure you that the mould tool and thermoplastic choices are correct. Testing and prototyping will also ensure that the parameters of the process are correct so the final components are of a consistent high quality.
  • The volumes of parts that need to be produced. The cost of developing, building and maintaining a tool is quite high. Offsetting this by creating or selecting a tool that creates multiple components every cycle is one way of balancing this cost. Also considering how long and how often the component will need to be produced will help to guide the tooling specification, cavity selection, cycle time and final costs.
Adjusting the tool design means you can create a range of products.

Why selecting the right tool is important

The cost and time investment of getting an injection moulding tool right is quite high. However, it’s important to take the time and spend the money selecting the correct tool in order to:

  • Make the process efficient and cost-effective. Selecting the right mould tool, with the correct controls and parameters, will shorten cycle times and lead to production efficiencies. Controlling elements within the process such as the dimensions of the gate and runner that feed the plastic into the tool will make the process as efficient as possible.
  • To ensure your parts are of a consistent high quality. Given that your tool is properly maintained, designed and built and that the parameters of the injection moulding process are accurate, any tool should be able to produce parts for thousands of process cycles with very few faults. Making sure that the right grade of steel is selected and that the correct cooling channels are put within the mould will ensure the tool doesn’t wear or delay the moulding process. This means the parts will always be accurate and consistently high

Essentra Components and injection moulding tooling

To help our customers to get the most cost-effective, efficient injection moulding tool possible, we can support them in the design and selection of moulds, as well as provide advice on the type of thermoplastic to use based on the application of the final part.

There are many ways that our team help customers get the accurate, high-quality components they need:

  • Our materials experts provide a highly proactive, responsive and flexible approach that create accurate injection moulding solutions
  • Our technical team work with customers to develop product solutions that meet the final application
  • Our dedicated in-house design team support our customers during product development to better meet their requirements
  • Our additive manufacturing capabilities in 3D printing support product development and create an accurate final product design
A short guide to injection moulding thermoplastics