ArcelorMittal and Nebrija University use 3D printing to build a motorbike chassis

Steel is an extraordinarily versatile material that offers many advantages; among them, its mechanical properties. However, its use in certain applications where weight may be a critical factor may initially place it at a disadvantage. Managing to make steel components lighter than those made of aluminium or titanium, while controlling their cost, is a challenge that, according to Sergio Corbera, head of the Motor Engineering Area at Nebrija University, “seems simple, but is enormously complex”.

This was the starting point of intense collaboration between ArcelorMittal’s Global R&D organisation, which brought to the project its technology in additive manufacturing and its expertise in design and simulation that guided the whole process up to the development of the final geometry, and Nebrija University, which contributed its developments in smart design technology, its expertise and experience in racing vehicles, all key aspects in the achievement of this milestone.

This close collaboration between the Company and the Materials and Advance Manufacturing research group (MOD3RN) at Nebrija University has led to the manufacture of a steel chassis that could revolutionise the motorbike world. “The simulations seem to indicate that we have achieved a well-balanced chassis, which a priori should give the motorbike a very good performance on the race track. We have applied a manufacturing technology (3D printing) which is new for this sector, using a material that a priori might seem to have been displaced by alternative materials in this industry, and with radically innovative geometrical shapes”, Corbera said.

• This chassis, made exclusively of steel, combines the mechanical properties of this material with the lightness characteristic normally associated with other materials such as aluminium or titanium. This milestone has been possible thanks to a completely hollow and innovative geometrical design.
• ArcelorMittal’s 3D technology and expertise, the work of its designers and the smart design algorithms of Nebrija University have made it possible to develop this ground-breaking component.

Generally speaking, the most widely-used material in the motorbike industry is aluminium, with steel in some exceptions. Characteristics such as lightness and certain properties which, after years of research, result in a good performance of the motorbike, have been a key factor in this material becoming a common denominator in any chassis. Managing to develop a steel chassis capable of equalling or even improving on the lightness provided by aluminium and that gives a riding experience and performance similar to those obtained with the latter material is one of the milestones achieved in this partnership between ArcelorMittal and Nebrija. 

Innovation, artificial intelligence and additive manufacturing

In its technological innovation centre in Asturias, ArcelorMittal is researching the application of state-of-the-art digital technologies, such as 3D-printing and artificial intelligence, to the steel industry, from production to application. Nebrija University integrates artificial intelligence and generative modelling techniques – smart design or generative design – to develop products that can contribute to creating new success stories within a research and innovation environment, applied in this case to the automotive racing sector. “This is how the initial relationship evolved and has now become a whole line of development with a high technological impact, of which this chassis is the first product to be presented”, commented Rafael Barea, head of the Materials and Advance Manufacturing research group at Nebrija Universi

In order to achieve a steel part that is lighter than one of aluminium or titanium through the use of 3D printing technology, researchers at Nebrija University designed highly innovative geometrical shapes that allowed the production of hollow parts. Corbera explained: “With our algorithms, we had more or less achieved the new shape. The possibility of generating hollow parts was the main unknown for 3D printing with metals. We are talking about wall thicknesses ranging from 0.8 to 1 millimetre in the chassis. This implied addressing several aspects within the 3D printing operation: stability of the part during the printing process, in view of the very fine thicknesses; controlling pores and mechanical properties with these thicknesses; and orientation of the geometrical shape to avoid internal supports. These unknowns were progressively overcome during the joint research project, thanks to certain properties provided by steel in the printing process and which allowed the production of hollow parts to become a reality”.

Achieving hollow parts is the cornerstone of this partnership, as it opens the way to developing very lightweight steel solutions, thanks to the very fine thicknesses obtained in the 3D printing process; to date, this is difficult to obtain with aluminium and titanium and could therefore have a negative impact on the structural strength of the part. Once the stability of the steel solution with these thicknesses had been confirmed and the mechanical characteristics had been determined, these boundary conditions were integrated in the smart design algorithms so that these were capable of automatically generating a range of innovative geometrical shapes that were stable in the printing process, and with a design that always ensured certain orientations to avoid the generation of internal supports. “Once all this had been achieved and validated, we were in a position to apply it to the chassis, and to practically any part”, Corbera noted.

Seamless, hollow and with fine wall thicknesses

The design of the chassis – seamless, hollow and with wall thicknesses of only 0.8 to 1 millimetre – is the result of geometric innovation and the expertise of the designers involved in the process. It is probably one of the few 3D-printed hollow parts that exist in such a size, for such a demanding application and with such a light weight. “Our steel chassis weighs approximately 3.8 kilograms. None of the aluminium chassis of top brands weigh less than 5 kilograms, while the weight of other steel chassis can go up to 6-7 kilograms. The difference may seem small, but reducing grams in this type of parts is very, very difficult; therefore, a reduction of several kilograms represents enormous progress”, said Paula Rodríguez, head of the project at ArcelorMittal Global R&D, who has led these developments at the Company. She added: “Moreover, the initial feeling and data – which we still have to confirm – is that its performance in service, on the race track as it were, will be unmatched”. Nicolás de Abajo, global head of R&D centres at ArcelorMittal, commented: “The joint work carried out between our researchers and the designers at Nebrija University has been extraordinary. An excellent example of what can be accomplished thanks to the huge growth of exponential technologies, a disruptive approach and a great effort”.

Noteworthy is that this project did not include the development of a steel alloy, with the excellent results being achieved using a standard, widely available, steel powder for additive manufacturing. So, beyond the results achieved in the chassis, the development of steel parts that can compete in weight with aluminium or titanium could lead to a major change in this industry, as additive manufacturing combined with the right steel grade may result in an even more cost-competitive solution. This project opens the door to certain components being made of steel, thus supporting the return of this material for many applications in this business sector within the racing motorbike field.