Collaboration Leads to Optimized 3D Printed Motorcycle Part Produced with Generative Design

On display at the recent Additive Manufacturing Users Group (AMUG) and RAPID + TCT conferences was a motorcycle. But it wasn’t just any ordinary motorcycle; it had been specially designed by a collaboration of ECOSSE Moto Works, a manufacturer of luxury, limited-production motorcycles; ParaMatters, a leader in autonomous topology optimization and generative lightweighting design; and Renishaw, leading manufacturer of advanced metal additive manufacturing systems. The goal of the project was to lightweight the upper mounting bracket of the motorcycle without hurting the structural performance.

The partners decided to go with additive manufacturing for the redesign, using Renishaw’s metal powder bed fusion technology.

“We wanted to achieve significant lightweighting,” Michael Bogomolny, PhD, Co-Founder and CTO of ParaMatters, told 3DPrint.com. “Generative design by ParaMatters, which the best in a class, generates very effective and high performance designs. These designs are usually very organic shapes and the only way to realize these designs is AM.”

The original mounting bracket was designed for subtractive manufacturing and made from aluminum. The mass of the original part was 823 grams. First, the team evaluated the loading scenario and validated the performance of the original design. Next, they had to detect and sketch the available design space where the new optimized bracket could be located, and the non-design features that should be preserved in the re-design process were identified.

An assembly of design and non-design parts was then exported into ParaMatters’ recently introduced CogniCAD software.

“CogniCAD is a software platform that generates designs for you, without a need to explicitly draw shapes,” Bogomolny explained. “User just needs to sketch available design domain (bounding box), apply load scenario and define what are structural performance goals – click the button and final design, satisfying pre-defined requirements ready for AM is automatically generated. Manual/human designs would take days/weeks and wouldn’t be as efficient as ParaMatters design which take tenths of minutes up to hours. You can see it as an autonomous vehicle, which drives you according to goals. CogniCAD is an autonomous mechanical design.”

Once imported into CogniCAD, the design workflow involved several steps:

1. Selection of material
2. Signing of design and non-design parts
3. Applying boundary conditions and load scenario
4. Defining design goals

Six static and vibration load scenarios were applied to the model, with the goal of minimizing bracket mass under constraints of fatigue and vibration frequency. The fatigue constraints were converted to stress constraints with a safety factor of at least 3.0 and targeted the first natural frequency, considering concentrated masses on the wings, to be larger than 91 Hz.

The final CogniCAD design was done in high resolution, which allows for highly detailed designs and a fast design process of about eight hours, resulting in a smooth and watertight mesh ready for 3D printing.

The mass of the optimized bracket was 530 grams, 35% lighter than the original bracket.

“At the beginning we targeted ~20% of weight reduction,” Bogomolny told us. “In fact after the first iteration we achieved ~50% reduction of weight. However, because customer hesitation, we decided to be a bit more conservative and tighten design constraints for higher safety factor, we ended with ~35% weight reduction. This indicates that many part in industry are over-designed and there is a lot of place for optimization by (software) like CogniCAD.”

The part was 3D printed on Renishaw’s AM400 machine and fitted to the motorcycle. It fit perfectly, so it was then post-processed and the final installation was made.

“Following to the successful pilot project between ParaMatters, Renishaw and ECOSSE, all parties have agreed to continue collaboration,” Bogomolny concluded. “We are going to explore how to lightweight more massive parts of motorcycle.”

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[Images: ParaMatters]