Austrian motorcycle, bicycle and sports car manufacturer KTM is a major adopter of AM technologies. Today many of the company’s R&D activities with additive manufacturing take place through its KTM Technologies division, which in turn includes several different companies and AM service bureaus. KTM was among the first clients of HP’s 3D printing technology and has carried out some fascinating experimental development on the X-Bow sportscar. The latest case study is more closely related to the company’s core business: motorcycles. Specifically, on a brake lever for its top of the line Duke 1290. The lever was generatively redesigned for topology optimization, 3D printed by powder bed fusion in different materials and “hybridized” with continuous fiber reinforced plastics(CFRP) composites in a truly unique application case.
Before getting into this specific case study, a little background on KTM Technologies: the division – which focuses primarily on the use of composite technologies originated in 2007, when KTM Sportmotorcycle decided to realize the concept of a puristic CFRP sports car including a road license for small series production vehicles. A team of experienced lightweight and carbon composite engineers was taken on board in order to realize the venture. Due to strong market needs in the area of CFRP serial application, technological development was identified as the core competence and ideal basis of innovation, thus rebranding the company KTM-Technologies in 2009. Today the company operates from an ultra-modern location in Salzburg Anif (shared with Kiska, the affiliated design company). In 2012, the existing workshop was extended by adding a composite laboratory and a powerful in-house additive manufacturing systems.
KTM Technologies today works on the qualification and benchmarking of new processes, focusing on the evaluation of several different AM technologies including laser sintering, multijet fusion, stereolithography and thermoplastic filament extrusion. Within a closed process chain the teams study different carbon and glass fiber reinforced materials, editing product specific machine parameters and evaluating suitable post processing methods. The AM systems are distributed across a network of companies, which include the main KTM Group (DMLS, SLS, MJF and SLS systems), KTM Technologies (SLS and desktop FFF systems), Kiska (SLS, industrial and desktop SLA systems) and Pankl (several large DMLS and SLS systems).
Challenge: AM for end use composite parts
The merger between AM and advanced composite manufacturing led the KTM Technologies team to take on the challenge of developing of a functional/semi-structural polymer part with a complex three-dimensional surface, withstanding standard load cases. The identified solution was the hybridization of the 3D printed part using a load path oriented CFRP-tape to fulfill the loading case, by using the KTM-Technologies methodology to combine the materials.
This concept showcases the further potential for the hybridization of additively manufactured components in the development of lightweight parts. The specific example mimics the shape of a long-style brake lever used on KTM motorbikes. It represents a future use case of an AM-polymer core combined with CFRP on a three-dimensional complex surface. The freedom that AM provides to the geometry allowed the development of a load-path oriented hybrid part, reducing weight by up 40%, compared to an AlSi10Mg reference model for the criteria of ISO 8710 (also 3D printed).
“We began our study in phase 1 effectively began with a study of possible materials in light of the desired technical specifications,” says Maja Labentz, R&D Engineer, Technology and Development at KTM Technologies. “We then moved on to the design phase looking at topology optimization. Our goal was to obtain the maximum stiffness with 35% reduction in material use. This led to a first concept prototype and subsequent lattice structure characterization.”
“We proceeded to simulate the digital design model’s performance and then moved on to the next phase: technology and material selection.” Maja continues, going through the project’s presentation desk. “We then selected our partners and suppliers for the prototype part manufacturing. This information led us to produce two more prototype iterations.”
In the end, several different levers were 3D printed following a continuous evolutionary path which had to account for subsequent composite hybridization as well as aesthetic value and actual 3D printability in different materials. These included different combinations of PA powders mixed with mineral or metal powders.
The end result fulfilled all the initial requirements. The final brake lever increases the lightweight factor by 40%, fulfilling ISO 8710 requirements and reaching technology readiness level (TRL) 7 in just 21 weeks. This means that the process is beyond the technology demonstration phase and already viable for systems/system development. “We were able to characterize the lattice structure and identify a number of different polymer mixtures that were suitable for our hybridization process with the CFRP composite elements,” Maja concludes. “This led us to verify and complete development on the hybridization process itself, proving that the polymer parts could e as strong and durable as the metal parts, at a lower cost and weight.”