Mould Materials

Tool design for injection moulding requires the consideration of many key factors. In material selection it is critical to understand the surface finish and volume requirements of the moulded part.


An extremely broad material choice for IM tools is steel. The variety of grades available give flexibility to select an option more suited to machining (where specific profile details are complex), more suited for polishing (where the surface finish is critical) or more suited for longevity (where production volumes are likely to be very high).

As a general rule, the harder the steel grade the longer it takes to machine the cavity of tool, resulting in higher tooling costs but a higher quantity of components that can be produced without maintenance of the mould.

Where surface finish is more critical, high quality stainless or hardened steel produce the best finish and result in highly polished parts. Lower grades are suitable for spark eroding where a textured or matt finish is required.


Aluminium can be used as a more economical alternative, mainly due to it’s ease of machinability rather than the actual material cost. This ensures faster production of the tool in comparison to steel and often more flexibility in profile design.

Polished finishes can also be achieved quicker due to the softer nature of the material. Aluminium mould tools heat up quicker than steel making it more suitable for very low production runs.

Although aluminium tooling is generally seen as more suitable for lower production quantities, as a specialist “soft-plastic” moulder, PolyGlobal also uses it as a viable option for full production runs on materials such as TPU’s and TPE’s. Thousands of production parts are manufactured from aluminium tooling.

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