Honda, like other automakers, has is focused on reducing the weight of its vehicle components, from body frames and engines down to the bolts. To achieve a reductive design, the structure and materials used in every part must be scrutinized. The latest target for Honda R&D is the crankshaft.

Crankshafts need to satisfy multiple functional criteria. For example, its shape must be able to withstand combustion pressures, and the rotational balance must be maintained. These factors have dictated the crankshaft’s form to this day. Over the long history of engine development, the crankshaft design had become a foregone conclusion. Despite this, we set the challenging goal of designing a crankshaft to be 30% lighter than current models.

—Hirosumi Todaka, a mechanical and fluid machinery designer at Honda R&D’s advanced technology lab

Using generative design and additive manufacturing, Honda R&D created a crankshaft prototype weighing about half the amount of a traditional design.

While searching for design technology such as topology optimization, Honda R&D found that generative design (where multiple designs are generated and iterated upon) could greatly change conventional design norms.

Generative design had already helped the industry to redesign components such as seatbelt brackets, engine control units, and motorcycle frames; significant weight reduction resulted in each case.

Honda R&D began its project, in collaboration with Autodesk, focused on cultivating a flexible approach. Autodesk prepared a first-lot model that fulfilled Honda’s requirements for the part using Netfabb and Fusion 360.

We shared Honda’s expertise to provide data on weight and various operating constraints, then went over each point with the Autodesk team as the model took shape.

—Hirosumi Todaka

The data from the prototypes made Honda rethink its layout and strength criteria, resulting in a new set of boundary conditions for the parts. The team continued its work and designed a second-lot model.

Conventional topology optimization provides one solution and requires time-consuming manual corrections. Fusion 360’s generative design offered what Todaka says was “a configuration I had not even considered as a designer.” The new crankshaft design exceeded goals with a surprising 50% weight reduction, but doubts remained about whether the part’s rigidity and strength would hold up against typical crankshafts.

Team members mounted the prototype to an engine for performance testing and shared the resulting data with the Autodesk team, which is using Honda’s data to refine its generative-design processes.

Integrating manufacturing into the design process proved invaluable by providing models that can take into account design limitations, such as those introduced by using additive manufacturing, mold-based manufacturing, or 5-axis machining, Todaka said.

While some still hold reservations about this new shape, the attention it has brought to the technology has been worth the effort. While there is still much that can be done to lighten parts, we can now see a way forward to reach our goals. In the future, I expect that innovative products created using generative design will be the norm. I think it is up to us to research further applications for this technology as part of our work.

—Hirosumi Todaka