Student engineers have used additive manufacturing technology to manufacture steering knuckles in a championship winning Formula Student race car.
The steering knuckle, a key part of the car’s front axle, is a stub axle that connects the tie rod, suspension, brake and wheel. It transmits all the forces from the wheel to the vehicle chassis, so has to be strong and in the case of a race car it also needs to be light.
The use of additive manufacturing in the design and production process has resulted in the weight of the knuckle being reduced by 660g, a saving of 35% compared with the previous cast part. At the same time, the engineers succeeded in increasing its rigidity by 20%.
The knuckle forms part of the unsprung mass of the vehicle and less weight below the suspension improves shock absorption, enhancing handling and bringing down lap times. The designers from Rennteam Uni Stuttgart (www.rennteam-stuttgart.de) were tasked with finding the optimal balance between rigidity and weight. The team found a solution in the use of direct metal laser sintering (DMLS).
“We previously produced the part using an aluminium precision casting process, which led to limitations in freedom of design, notably that the part had to be solid throughout,” stated team member Yannick Löw.
“Investigation into new, innovative ways of manufacturing the steering stub axle led us towards additive manufacture and EOS, which agreed to support us.”
From the conceptual design phase for their Formula Student 2012 competition car the engineers used CAD software from Within Technologies Ltd, UK, a company whose programmers have written software specifically for the additive manufacturing process.
The programme allows 3D printing of optimised structures of variable density. The designers were able to match the steering knuckle’s structure accurately to the required physical properties, leaving it solid where strength was needed and introducing hollow parts where possible to lower the weight. The part was manufactured using aluminium AlSi10Mg powder at EOS’ headquarters in Krailling, near Munich.