To fully reap the benefits of additive manufacturing technologies for part production, it is often necessary to go back to the drawing board to reengineer the part in question and optimize its structure for AM. Fortunately, with state-of-the-art software programs such as ParaMatters’ CogniCAD, redesigning a part for AM doesn’t necessarily entail going back to the literal drawing board.
As ParaMatters recently demonstrated through a collaboration with metal AM company Renishaw and motorcycle manufacturer ECOSSE Moto Works, Inc., it is possible to redesign a part for optimal performance while reducing material usage and weight using autonomous, generative design software such as CogniCAD.
The collaboration in question consisted of updating the design of an upper engine mounting bracket for an ECOSSE motorcycle using ParaMatters’ cognitive software platform and then 3D printing it using Renishaw’s metal powder bed fusion technology. The ultimate goal of the project was to lightweight the bracket part without compromising structural performance.
Thanks in large part to ParaMatters’ topology optimization software tools, the three companies were able to produce the upper engine mounting bracket that was not only 35% lighter than the original part but demonstrated better static and structural performance and similar vibration performance.
The 3D printed part, which was installed into an existing ECOSSE motorcycle, has now been in use for nearly three months and has shown positive results. This, explains ParaMatters’ founder Michael Bogomolny, is something worth emphasizing.
“You don’t see many applications today with topology optimization, generative design and 3D printing which are being used in real applications,” he says. “You see some impressive test cases but not often in a real vehicle. We are one of the first, if not the first, who really implemented it.”
In keeping DfAM in mind, the first step was to evaluate the original upper mounting bracket, its loading scenario and its performance. Once that was done, the team sketched the design space for the new bracket assembly and identified non-design features. This model was then uploaded into CogniCAD, a cloud-based generative design platform capable of autonomously generating AM-designs using topology optimization, computational geometry and high-performance computing.
Within CogniCAD, the engineers then specified a range of parameters, including print material, design and non-design parts, boundary conditions, load scenarios and overall design goals. In keeping with the original design, aluminum was chosen as the print material and six static and vibration load scenarios were applied to the 3D model.
“The objective was to minimize bracket mass under constraints of fatigue and vibration frequency,” states a press release. “The fatigue constraints were converted to stress constraints with safety factor of 3.0 at least and targeted first natural frequency, considering concentrated masses on the wings, to be larger than 91 Hz.”
Once these parameters were input into CogniCAD, the software began generating a high resolution model (with a discretization of approximately 10 million elements). After just eight hours, the model generation was complete, resulting in an optimized, watertight and fully 3D printable bracket design.
Of course, a few other design considerations had to be taken into account. For one, the engineering team had to ensure that the 3D printed part would fit into the existing motorcycle assembly, even after post-processing.
Bogolmony explains: “Because of the need for post-processing, we intentionally designed holes slightly smaller than they should be and in a diamond shape to eliminate the need for supports. After Renishaw printed the part, the holes were post-machined and the part was installed in the motorcycle and it fit very well.”
The bracket itself was 3D printed by Renishaw using their AM400 3D printer and AlSi10Mg material. With a layer thickness of 30 microns and no heat treatment, the part took under 30 hours to manufacture. Once the 3D printed upper engine mounting bracket was delivered, it was tested for fit before being media blasted, painted and installed.
In terms of optimization, the bracket was 35% lighter than the original part and had a maximum stress reduction of 20%. Bogolmony adds that the part could have been even lighter and stayed within initial stress constraints, but ECOSSE opted for tighter constraints.