Rapid computer tomography can improve the quality in aluminium die-casting production

The trend in automotive manufacturing is for lighter and lighter-weight components. Less weight on the vehicle means less fuel consumption, lower operating costs and less environmental pollution. The challenge is to secure a high quality of the end product when the material usage is being reduced. This applies particularly to aluminium die-cast parts such as cylinder heads and brackets, which are exposed to continuous mechanical stress.

Rapid computer tomography can help to ensure quality. In cooperation with several research partners, employees of Pressmetall Hoym GmbH in Saxony-Anhalt are examining the use of computer tomography to improve the production process. They are convinced that this will produce competitive advantages in aluminium die-cast manufacturing over their international competitors.

More security, lower fuel consumption and better environmental compatibility: These are the three challenges for future road vehicles. For this reason, scientists in the automotive sector are always investigating new materials and working on optimising development and manufacturing processes.

This applies particularly to components which are produced using aluminium die-casting. “This is a process that has been used for many decades to quickly and economically produce light aluminium components consecutively,” says Professor Dr-Ing. Eberhard Ambos, a skilled casting engineer who worked at the Institute for Production Technology and Quality Assurance at the Otto-von-Guericke University in Magdeburg until just a few years ago.

With aluminium die-casting, liquid aluminium is pressed into a pre-warmed steel mould and compressed until it sets. The skill exists in optimising the dozens of process parameters, such as the temperature of the smelting, the filling speed and pressure so that a component is produced which has as few gas bubbles (pores) as possible.

Unfortunately, the pores cannot be completely prevented. However, in terms of components with a decreasing proportion of material, it is becoming ever more important to know where exactly the microscopic holes are in the component. “It is bad if they occur in load-bearing zones or on parts which carry oil or water,” says the Magdeburg-based casting expert and production engineer. This increases the risk of breakages and unwanted leaks.

To date, the factory in Hoym has managed to hold its own in the international competition to supply the best aluminium die-cast parts for the automobile industry. For the last two years, it has been part of the Pressmetall corporate group with its headquarters in Gunzenhausen near Nuremberg. At the two sites, about 850 employees currently generate a turnover of about 100 million Euro. “Our aim for the coming years is to increase turnover to over 150 million Euro,” says Günter Werner, managing director at Pressmetall in Hoym.

An important condition for this is to fulfil the increasing quality demands on aluminium die-cast parts to continue to satisfy their partners in the automobile industry. Pressmetall Hoym does not have its own research department, but it has a long-standing cooperation with scientists at the Otto-von-Guericke University in Magdeburg – in particular with Prof Eberhard Ambos. A focus with regards content: The assessment of the position, form and size of pores in die-cast parts and their optimisation.

“With the conventional, two-dimensional x-ray component investigation, it is not possible to define the precise location of pores,” says Professor Ambos. It would be just as futile to conclude the size and position of holes in other parts of the block from a single slice of Swiss cheese. Instead, what is required is a three-dimensional fluoroscopy, as it used in clinics and radiological practices for medical diagnosis of the human body.

“At the beginning, we really investigated aluminium cast parts in a medical CT scanner,” remembers Professor Ambos. But because this was not a long-term alternative – ultimately technical components can be analysed with much higher doses of radiation than human tissue making it a faster process – Professor Ambos and the employees of Pressmetall Hoym searched for other cooperation partners within the industry.

They found sympathetic ears in the form of GE product manager Dr Oliver Brunke in the Lower-Saxonian town of Wunstorf and Christoph Reinhart, the managing director of Volume Graphics in Heidelberg. They developed CAT scanners including evaluation software, which can investigate components three-dimensionally for microscopic pores within seconds. Within a day, about 400 aluminium cast parts could be investigated to determine their number, size, form and position.

“The aim was to gather information about as yet unexploited optimisation potentials in the manufacturing process,” says Pressmetall managing director Werner. As was found during the course of the investigations, there is no one single parameter in aluminium die-casting that has a decisive influence on the formation of pores. It is more of a combination of several factors, which require more data analyses by computer scientists to find. This is why continuing investigations to optimise the pore location and number are being prepared with the involvement of other experts and the support of the Ministry of Science and Economic Affairs and the Investitionsbank Sachsen-Anhalt. 

The aim is optimised and seamless aluminium component quality. For Pressmetall, this would be an important locational advantage, with which jobs in Germany could be secured in the long-term.

Author: Uwe Seidenfaden on behalf of Investment and Marketing Corporation Saxony-Anhalt
Caption: Inspection of a component that was created in aluminum die-casting process. The company Pressmetall Hoym GmbH (Saxony-Anhalt) provides various support elements for automobile manufacturers.

Photo: Pressmetall GmbH

Günther Werner
General Manager
pressmetall GDC Group GmbH
phone: +49 (0) 9831 / 5007-167

Prof. Dr.-Ing. habil. Eberhard Ambos
Tel.: +49 (0)39202/60112