R & D

Has mixed construction passed its zenith for the time being?

| Author / Editor: Norbert Wellmann / Frauke Finus

Robot-supported tool construction.
Robot-supported tool construction. (Bild: PTW/PTU TU Darmstadt)

No-one disputes the necessity of lightweight construction in transport, in aerospace, packaging and in the moving parts of machines, systems and installations. But, for the moment, has mixed construction with fibre-reinforced plastics passed its zenith?

The trend towards lightweight construction, as we have known it since the beginning of aircraft construction and especially in the last 30 years of automobile construction, continues unbroken. Yet at the moment, many manufacturers of products – the carmakers not the least among them – are asking how far mixed construction, and especially the use of relatively expensive long-fibre-reinforced plastics, can go. On the political front, a critical discussion over the fundamental risks of the environmental effects of plastics raises further questions. Will weight advantages be economically justified in future?

Weight, of course, only plays a role where irregular motion with acceleration and braking phases is involved. If electric motors are employed in automobiles of the future, part of the braking energy can be recuperated. In an aeroplane, this is naturally not so simple. If good traffic flow could be achieved by improving traffic regulation in cities, weight would play almost no further role in energy questions, as is the case with cross-country journeys.

Not only in car-making does lightweight construction play a role

Yet this is not all, for as long as highly agile cars are meant to be fun and as long as safety is the highest priority, weight will in fact play an important role.

No-one disputes the necessity of lightweight construction in transport, in aerospace, packaging and in the moving parts of machines, systems and installations. With the latter, the aim is to reduce not only cycle times, but also forces and moments. When it comes to handling, a role is played by workplace protection and load handling regulations. In the private household, whether in the kitchen or in other areas, lighter tools and aids are more pleasant and precise to use, and aesthetics and quality are very significant. In the near future, the sustainability and environmental friendliness of fibre-reinforced plastics will have to be discussed again. The possibility of sustainable recycling has hardly been developed yet, and it is clear that the sensitivity of the public and politicians will be greater.

There are currently over 150 industrial research projects at the EFB in which the burning questions and ideas of the immediate future are modelled. The firms relevant to technological progress in Germany are involved and are working intensively in the expert team. The projects look at the real and virtual worlds of industrial processing of sheet-metal and hybrid structures, including composites with plastic-based working materials and also tackle the topics of genes, tools and systems for separating, forming and joining.

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The focus in research is currently shifting

Some time ago, the main emphasis of the projects was on new working materials and hybrid constructional techniques in mixed materials. Answers were needed to the fundamental questions of understanding the processing, from separating technologies to forming, and from the manufacture of components to ways of joining them. Currently, the thematic emphases are shifting visibly. More importance is once again being attached to high-strength and hot-forming steels – with the exception naturally of aircraft construction – and an even better future is being predicted for them. The main aims here are broader applications for lightweight construction and, of course, the productivity of the manufacturing processes.

Current ideas for new projects lie in the most various categories, but with most of them touching several subject areas at once, so projects can be listed twice when one attempts to assign them to categories. On this basis, over 50 % of the projects are concerned with lightweight construction. Over half the projects look into further developments with steels, with increasing importance being given to press hardening. In most of the projects, presses, tools and joining systems play a major role. And in about 30 % of the projects virtual methods, material models and parameters are considered and developed.

Three lines of development and research

On the basis of the EFB roadmaps for current higher-level trend topics, each project can be linked to one of three directions of development:

  • Extension and integration of functions in sheet-metal processing (45 %);
  • digitisation, intelligent manufacturing processes, Industry 4.0 (37 %);
  • intensive hybrid lightweight construction (18 %).

Developments in the field of extended functions are associated with new, combined process steps, such as hybrid presses, the manufacture of hollow crankshafts using internal pressure forming, and special tool coatings for forming 7000-series aluminium sheets. There is continuing examination of pre-compression operations in press hardening during the internal high-pressure process, and hot forming is one of the applications in question for achieving a selected setting of the austenitic stability by regulating the temperature of the deep-drawing tool.

Topics such as reducing the edge damage during pre-punching, integrating the diffusion control of alloy components into processes to achieve higher performances from steels, the electrical contact characteristics of joints made by forming, the raising of the load-bearing qualities of joints subject to combined stresses, the assessment of high-speed shear cutting on presses, vario-thermal tools, the use of lasers in edge finishing, and the service lifetime of additively manufactured production equipment are intended to improve the functionality, usability and productivity of manufacturing processes.

Digitisation brings advances in processes

Through digitisation, completely new conditions and possibilities for processes arise. The number of projects examining this topical area and looking into intelligent production processes has increased rapidly in the last 24 months. Here the primary questions concern the characterisation and analysis of semi-finished products, installations, presses and operations. A further requirement is that, in the end, advance planning and the termination of efficiency must be possible. To what extent can models be used for intelligent prognoses, and how must the sensitivity be considered? One project looks into the basic development of start-to-finish digital models of the entire value creation chain, from the coil to blank outlining, from sheet-metal forming to joining technology.

How can the important process parameters be measured and re-worked? Are there relevant para­meters which are not traditionally used for control purposes? Efficient models and solutions for bringing together virtual planning and production must be developed, with a particular challenge being presented by trying-out and quality assurance. Attention is continuing to be paid to the thematic areas robot-supported tool construction, adaptronic moulds, robot-supported joining, augmented reality, and the blockchain in sheet-metal processing: the aim is processing and using data and information in a new way. The big question here is: Which data and quantities must be recorded and retained for the future? Basically all, or only those for which it is already clear today how they can be applied usefully, and for which there are already sensible algorithms?

In many industrial fields, and not only in automobile construction, the need is for sustainable working materials solutions allowing highly effective, efficient and economical processing. In intensive hybrid lightweight (mixed) construction, the emphasis is on joining different kinds of working materials and components, with the focus at the EFB being on joining metallic materials to plastic-based fibre-reinforced working materials.

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Intensive hybrid lightweight construction aiming at cost-effective joining

In the past, the entire bandwidth of work material characteristics was investigated. Today, the concentration is on the search for secure and cost-effective connecting of different working materials and join partners. For this, the focus is on the surfaces of the neighbouring working materials as well as on new joining procedures, with the aim of strengthening joining characteristics and avoiding corrosive procedures.

What is the right treatment of working materials in order to achieve a perfectly functional combination of working materials which can at the same time be manufactured efficiently? Once solutions are available which are clearly suitable for mass production, it can be predicted that these working material solutions will move into a significantly more competitive position in the market.

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* Dr. Eng. Norbert Wellmann is CEO of the EFB – the European Research Association for Sheet-Metal Processing in D-30559 Hannover, Tel. (00 49-5 11) 9 71 75-0, info@efb.de

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