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AM brings world-class process solutions for high pressure diecasting foundry

A ‘forward focus’ ethos has driven a UK high pressure diecasting foundry through a series of investments to fully embrace additive manufacturing, resulting in continued production of high quality and durable lightweight castings.

Based in mid-Wales, CastAlum has a reputation for pushing the boundaries. A greenfield development in 2000, serving just one customer, the diecaster now has a diverse, blue-chip, automotive customer base with 90 per cent of production destined for the export market. The company is now believed to be the first diecasting foundry in the UK to adopt additive manufacturing in its entirety in-house to produce its own conformally cooled die tooling. Working in partnership with Renishaw and Coventry University for the past couple of years, CastAlum has developed processes and methods to extend life and promote enhanced quality.

Utilising ten high pressure casting cells, ranging from 1100t to 2200t, and three squeeze casting cells, ranging from 1450t to 1800t, alongside 16 machining centres, supplying a range of products (in both HPDC and ‘squeeze cast’) CastAlum supplies castings in their raw state, fully machined, or assembled and tested as customer dictated. Components are used in vehicles produced by a number of prestigious marques, including: BMW, Ford, General Motors, Fiat, Renault, Porsche, Mercedes, Jaguar Landrover, AML. Investment in the latest technology is nothing new for the company, which has worked with customers to adapt and support ongoing moves towards new challenges such as electric vehicle (EV) and low carbon vehicle (LCV) technology.

By 2014, CastAlum was already an early adopter of AM technology, working closely with an Italian company developing conformal cooling techniques in tool steel, with promising early results. “With the good came the bad”, explains CastAlum AM engineer, Rhys Jones. “Despite the overall equipment efficiency, the variables in tool life and high part costs where simply unjustifiable in a competitive commercial business – something had to change.” The benefits that additive manufacturing could bring to HPDC were too great for CastAlum to simply ignore. Successfully securing a collaborative R&D award with InnovateUk in 2018 allowed the company to accelerate progress with the technology and iron out the issues previous identified.

Speaking about the move Paul Dodd, engineering director said: “Investment and understanding of additive material technology to aid with conformal cooling has allowed us to change what was viewed as feasible within the industry. We now have a wealth of experience and data to support the development of lightweight casting technology without sacrificing properties or durability.” CastAlum is now the first company based in Wales to independently run a powder bed SLM machine outside of a university, continuing to develop additive manufacturing for the foundry industry.

Rhys Jones explained: “The parts that we look to produce on the SLM printer aren’t the traditional 3D printed parts that we are familiar with, with lightweight lattice structures a thin walls, the parts that we need are large dense parts that are capable of withstanding the harsh environment of high pressure diecasting. With this came its own set of problems to overcome. The SLM or selective laser melting process broken down is welding, the machine lays down a thin layer of powder – in our case it’s 40 micron thick – the laser then super heats the powder fusing it to the layer below, layer by layer the part is formed. Unfortunately for us, with our large bulky parts, the more the laser has to melt the more ‘welding splatter’ and smoke is generated. Over time this makes the build chamber dirty and can potentially degrade the quality of the part as it builds up, this is where we need to work smarter to overcome this issue.”  

Process of making an AM part

The first step in making a tooling insert on the printer is to consider its geometry and determine if it can be built on an SLM printer. Tooling inserts naturally have draft angle for releasing the casting out of the die, this suits the printing process as it means that the geometry is self-supporting and can build without support. The next task is to lay out the cooling channel, and tie this in with the company’s process department and in-house toolroom, capture their feedback and model it in.  Jones enthuses: “All our 3D modelling is caried out in house, this enables us to be very flexible and dynamic when it come to design changes, allowing us to make small changes to optimise performance.

“Once we are all happy with the design, we can print it; we use Renishaw’s file prep software to lay out the build and set the build parameters. The printer runs largely independent for the entire build, only needing brief operator intervention to look after the powder. Our builds tend to run from around 80 hours to 120 hours depending on the part size.” Once the build has finished the powder is removed from the part, the part is then taken for final machining. The parts off the printer have a rough finish, unsuitable for the casting process, to overcome this, machining allowance is added, a 3 axis XYZ mill is used to fully finish the parts, which gives a much better surface finish and ensures the dimensional accuracy of the parts. Through the innovate project CastAlum has been working closely with Coventry University, which is developing methods of calculating the amount of cooling needed at each point of the casting, to allow much more efficient and uniform cooling of the mould.

Jones is thankful for the assistance of those in the supply chain: “We were very lucky to be a part of Renishaw’s solution centre up in Stone where we had access to the wealth of Renishaw’s AM knowledge. The solution centre allowed us to learn how to use the new technology in the safety net of their facility.” In the future CastAlum will be looking to capitalise on this new found technology, transferring the wealth of knowledge gained throughout this calibration into new projects.

Contact: Paul Dodd, CastAlum Ltd, Buttington Cross Enterprise Park, Welshpool, Powys SY21 8SL, Tel: +44 (0) 1938 557557, email: paul.dodd@castalum.com web: www.castalum.com