What is Aliminium Gravity Die Casting?

Nov 15, 2023 | Know-How

The Challenge

Kingston University design student Benny approached Maybrey Precision Castings with an innovative aluminium door handle concept that formed part of his final-year project. Having already produced a 3D printed prototype complete with the appropriate draft angles for sand casting, the initial objective was to manufacture a sample casting to validate the design.

Following the successful sample, Benny wanted to progress to a production-ready solution. As a student working within a limited budget, commissioning a professionally manufactured pattern was not financially viable, so he made the decision to manufacture the pattern himself at the Kingston University workshop.

To achieve a fully functional casting, the door handle required a hollow section at one end to accommodate the fixing mechanism. This introduced an additional level of complexity, requiring not only a pattern but also a correctly designed core box and core print arrangement to produce and accurately locate the sand core within the mould.

Our Solution

Working closely with Benny throughout the project, our technical team provided guidance at every stage of the tooling design process. Through a series of video calls, we discussed the complete pattern design, including impression layout, moulding box size, pattern orientation and the overall setup required for successful production.

Particular attention was given to the design of the core box and core prints. We explained how the positive core print on the pattern and the corresponding negative feature within the core box would accurately locate the sand core during mould assembly, ensuring the finished casting incorporated the required hollow section.

Using this guidance, Benny produced the complete pattern and core box design in CAD before submitting it to Maybrey Precision Castings for technical review and approval. Once approved, the tooling was manufactured at the Kingston University workshop.

Collaboration and Delivery

With the tooling complete, Benny visited our foundry in Aylesford, where he experienced the complete sand-casting process first-hand. Working alongside our experienced foundry team, he was shown each stage of production, from mould preparation and pattern setup through to core placement, aluminium melt preparation and the pouring of the moulds.

This collaborative approach enabled Benny to see how design decisions made during the development phase directly influenced the manufacturing process, providing valuable practical experience that cannot be gained in a classroom environment alone.

The Result

The finished aluminium castings met the design requirements and demonstrated a successful transition from concept, through tooling design, to completed cast components.

Benny was delighted with the finished door handles, which were exhibited at Kingston University's end-of-year showcase. The quality of his project led to his selection to exhibit at the prestigious New Designers Show in London, where emerging designers from across the UK present their work to industry professionals.

This project demonstrates Maybrey Precision Castings' commitment to supporting innovation and developing the next generation of engineers and product designers. By sharing our technical expertise and working collaboratively throughout the design and manufacturing process, we helped transform a student's concept into a professionally manufactured product ready for national exhibition.

Whether restoring history, supporting innovation or creating something entirely new, Maybrey Precision Castings combines traditional foundry craftsmanship with modern engineering expertise to turn ambitious ideas into exceptional castings.

Gravity die casting is a permanent mould casting process: molten metal is poured into a precision-machined steel die, fills the cavity under gravity, solidifies, and is then extracted when the die is opened. The same die is used repeatedly, producing castings with consistent dimensions and a better surface finish than sand casting.

The word 'permanent' is the key difference from sand casting. In sand casting, the mould is destroyed to retrieve the casting. In gravity die casting, the mould stays, and its quality improves with use as the die surface conditions. This repeatability makes gravity die casting well suited to components that need to be produced in identical form across a production run.

How Gravity Die Casting Works

The process begins with die preparation: the steel tool is coated with a refractory wash to prevent the aluminium from bonding to the die surface, and heated to the working temperature for the alloy being cast. This temperature control is important: a die that is too cold produces poor fill and cold shuts; too hot, and the casting's mechanical properties suffer.

Molten aluminium is poured from a ladle into the die. Gravity draws it through the running system and into the cavity. Sand cores can be set into the die before pouring to create internal features, undercuts, or hollow sections that the die alone could not produce.

After solidification and a controlled cooling period, the die is opened, the casting extracted, and the running system removed. The casting then moves to inspection and, where required, post-process operations.

Advantages of Gravity Die Casting

  • Superior surface finish: the steel die produces a smoother surface than sand, reducing finishing time
  • Improved mechanical properties: faster solidification produces a finer grain structure and higher tensile strength
  • Dimensional consistency: permanent tooling delivers repeatable accuracy across a production run
  • Reduced porosity: lower gas content compared to sand, important for pressure-tight applications
  • Sand cores: complex internal geometry is achievable within a die casting, combining the benefits of both processes

Gravity Die vs Sand Casting: Choosing the Right Process

The choice between the two processes depends on the component, the volume, and the requirements. Gravity die casting offers better surface finish and mechanical properties, but the tooling cost is higher and the process is better suited to aluminium than to iron or copper-based alloys.

At Maybrey we offer both processes from the same facility, which means we can advise on the right approach for each application without any bias towards one process over another.

Gravity Die Casting at Maybrey

Our gravity die casting operation produces aluminium castings to 25 kg in a full range of alloys, from commercial grades through class one aerospace-specification aluminium. All dies are designed in-house by our engineering team. We cast the die blocks themselves in our iron sand foundry, giving us control over material quality and lead times from the start.

Many gravity die castings leave our facility fully machined and heat-treated, reducing your supply chain to a single point of contact. For aerospace and defence work, our die casting operation is certified to AS9100 Rev D, with unbroken aerospace approval since 1937.

Explore our Gravity Die Casting capability

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We can take your casting through to finished component: machined, coated, tested, and ready to fit.