Tool Material Matters: Steel or Aluminium for Injection Moulding?

Oct 10, 2023

Plastic injection moulding is an intricate and versatile manufacturing process that has revolutionised the manufacturing of plastic parts for different industries like medical, automotive, aerospace, and many more. It involves injecting molten plastic into a detailed mould cavity which, when cools, can create a diverse range of products.

At the core of this manufacturing process lies the mould tools which are a fundamental part of the process. In this blog, we’ll delve further into mould tools and discuss the importance of the right material for injection moulding.

Importance of Choosing the Right Tool Material

The properties of the tool material can impact the quality of the final part and the efficiency of the production process. The tool material has a direct impact on the quality of the moulded parts as it determines the surface finish, dimensional accuracy, tool life, and the mould’s ability to replicate fine details.

The choice of tool material can also affect the efficiency of the production process as it impacts cycle times, maintenance requirements, cooling times, and the frequency of mould replacement.

Steel as a Tool Material

Steel has long been the preferred choice for injection moulding for many years due to its strength, durability, and versatility. Common types of steel that we use for mould tools include:

Hardened Inserts

Hardened inserts are precision components used in moulds and are made from high-quality tool steels. They play an important role in shaping the final product in plastic injection moulding. Different types of hardened inserts are chosen based on wear resistance, toughness, and temperature resistance. Here are the types we use:

  • 1.2344
  • 1.2083
  • 1.2767
  • 1.2363
  • 1.2369

Vanadis 4/ MV10 PM

Vanadis 4 or MV10 OM is a high-speed powder metallurgy tool steel renowned for its exceptional resistance. It has a combination of high hardness, chipping resistance, and machinability. These steels maintain their sharpness and precision over extended periods, resulting in improved production efficiency and tool longevity. Here are the types we use:

  • Plates
  • 1.2085
  • 1.2311
  • 1.1730

Hardened Plates

Hardened plates are flat components made from high-quality tool steel. They can withstand wear, pressure, and temperature variations. Here are the types we use:

  • 1.2083 this appears twice
  • 1.2343

Advantages of Steel as a Tool Material

High Durability

Steel is known for its robustness and longevity. It can withstand the harsh conditions of high-volume production without significant wear and tear. The durability of steel makes it an excellent choice for projects that need longer production runs, where the mould tool would be subjected to more stress.

Precision and Consistency

Steel is highly capable of maintaining tight tolerances and intricate details during longer production runs. This precision is important for industries that need strict adherence to dimensional accuracy and surface finish like medical and automotive parts.

Surface Finish

Steel moulds often ensure a superior surface finish on moulded parts. This is especially important for products with aesthetic requirements or components that need minimal post-processing.

Low Maintenance

Steel mould tools require less maintenance and fewer replacement costs compared to aluminium. This can result in lower downtime and reduced maintenance costs over the long term.

Disadvantages of Steel

Higher Initial Cost

One of the main disadvantages of steel mould tools is the higher upfront cost. The initial investment for steel moulds can be greater than aluminium, which may be an issue for some customers. Over recent years the cost differentiation between steel and aluminium has started to level out, largely due to the improvements in cutters and machine centres allowing highspeed hard machining.


Steel mould tools are much heavier than aluminium. This weight can be a challenge during handling, installation, and transportation and may need specialised lifting equipment.

Applications of Steel Moulds in Plastic Injection Moulding

Steel is the ideal choice for high-volume production runs where extended tool life and minimal downtime are critical. It can also withstand high temperatures making it suitable for materials that need higher processing temperatures, great for parts that need to be durable and precise. Here are some of the applications of steel mould tools.

Automotive Industry

Steel moulds are vital in the automotive industry where precision, durability, and material versatility are hugely important. They’re used for producing a wide range of components from intricate trim pieces to engine parts. Steel mould tools allow for tight tolerances and withstand high-temperature materials making them ideal for this industry.

Medical Devices

In the production of medical devices, precision and material compatibility are vital. Whether it’s syringe components, medical equipment housings, or implantable devices, the level of accuracy and durability that is needed can only be accomplished through steel mould tools.

Consumer Electrics

This industry relies on steel mould tools to create components with intricate details like smartphone casings and connectors. Steel can maintain consistency over long production runs making it ideal for batch production. Steel moulds ensure these parts meet the highest quality standards.

Aerospace Components

In the aerospace industry, safety and precision are non-negotiable. That’s why steel mould tools are used for creating various components, including those made from advanced composites and high-temperature materials.

Aluminium as a Tool Material

Due to its unique set of properties, Aluminium can help with low-volume production runs and due to the softness, it lends itself well to the requirements of development and pre-production tooling.

Advantages of Aluminium

Cost Effective

Aluminium moulds can be a more cost-effective option than steel. The overall return on investment of a mould largely depends on the mould usage, however, the initial investment in aluminium mould tools tends to be less.

Great for Low Volumes

Aluminium moulds can be used for low-volume batch production. This is because they offer better value due to their reliability in providing lower upfront costs. They can also produce reliable parts making them a good option.


Aluminium moulds are notably lighter, simplifying both handling and the installation processes. This characteristic may be beneficial in scenarios where frequent tool changes are required.

Disadvantages of Aluminium


The lightweight nature of aluminium comes at a trade-off in terms of durability. Aluminium moulds may not be suitable for applications involving high-temperature materials, materials with high wear or high production volumes, as they tend to require more frequent replacements.

Limited Surface Finish

While aluminium moulds can produce reasonable surface finishes, they may not achieve the same level of excellence as steel. For applications requiring pristine aesthetics, additional post-processing may be necessary.

Limited Material Compatibility

Aluminium might not be compatible with certain materials that need high-temperature resistance which limits its availability to be used in certain industries.

Applications of Aluminium Moulds in Plastic Injection Moulding

Aluminium can be cost-effective and lightweight which makes it ideal for short-run productions and prototyping. Here are some of the popular applications of aluminium moulds.

Rapid Tooling

Aluminium’s lightweight nature and great heat conduction properties make it a favoured choice for rapid tooling where quick tool changes and efficient cooling are important. Industries like the toy industry benefit from the agility provided by aluminium mould tools.

Materials with Low Processing Temperatures

Aluminium moulds are suitable for materials that do not require the high processing temperatures that steel can withstand. This includes various thermoplastics used in everyday consumer goods.

Steel vs. Aluminium: Who Wins?

At Pentagon Tooling, our preference is for steel tooling and is driven by a range of factors. Our standard practice involves using hardened tool steel inserts for moulding form precision, complemented by pre-toughened or mild steel plates forming the bolster. This preference is due to the huge advantages of steel tooling over aluminium counterparts. Our tool designer, Jake, explains:

‘Steel tooling is a long-term investment, the tooling will last for the lifetime of the product, aluminium is a disposable asset with a short life only suited to development and micro-batch production.’

When dealing with high-wear polymers or materials containing glass or filler content, aluminium tooling can quickly wear away small features and enlarge gates. In these cases, high-hardness steel tools become the preferred choice to maintain precision and durability. The suitability of aluminium tooling is also often limited to simple ejection mechanisms like pins and blades. For more complex ejection requirements involving cores with sleeve or stripper bush ejection, or profiled ejectors, steel tooling is the preferred option. The investment in these intricate ejection systems is justified by the extended lifespan and durability that steel tooling provides, making it the clear choice for lasting and high-performance moulds.

At Pentagon, we have a team of plastic injection moulding experts who can help you with your project no matter how large or small it is. With over 50 years of experience in the industry, we have the ideal experience, knowledge, and technology to ensure precise and quality parts for your industry. Get in touch with us now to see how we can help you.

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