German OEMs Flex 3D Manufacturing Muscle

Advances from BMW and Porsche push additive manufacturing further on the path to high-volume automotive applications.

Porsche’s 3D-printed housing for an EV motor/transmission passed all the company’s stress and quality measures. (Porsche)

A chief impediment for wider adoption of additive manufacturing long has been its potential for application in high-volume and high-throughput production. But continuing process and technique developments from automakers and suppliers are moving additive manufacturing, also known as 3D printing, closer to high-volume Valhalla, while also enabling production of increasingly complex and substantial components.

The case for this integrated traction motor/transmission was created by using additive laser fusion 3D printing. (Porsche)

BMW has sporadically fitted specialized 3D-printed parts — both metal and polymer — in series-production models for more than a decade. Recently it has used its Rolls-Royce brand as a platform for introducing 3D-printing innovations in a low-volume but high-expectation environment. And in mid-2020, BMW invested some 15 million euros to establish its Additive Manufacturing Campus near Munich to research and develop new 3D printing processes and other innovations that might accelerate the potential for 3D-printed components at large scale. The company said the facility symbolizes its confidence that 3D printing is poised to enable new manufacturing vistas.

BMW technician displays a 3D-printed bracket designed in the collaborative environment of the company’s Additive Manufacturing Campus in Germany. (BMW)
Rack of components 3D-printed in a selective laser melting process perfected at BMW’s Additive Manufacturing Campus near Munich. (BMW)
A variety of metal components manufactured by BMW with a selective laser melting 3D process. (BMW)

Parts currently produced at the new facility included polymer components made via selective layer sintering and multi-jet fusion. At the campus, engineers join with production and materials experts to evaluate “hundreds of components, focusing throughout on the economic benefits of the new technology, and on the weight and geometry advantages compared with conventionally manufactured parts.” BMW said components were selected for 3D printing based on metrics defined and translated into machine language: “This marked the start of a new AI system enabling the BMW Group to identify faster and earlier on which components could potentially be produced by 3D printing.”

Moreover, BMW is encouraged about 3D printing’s future because it can enable previously impractical, or even impossible, component designs. And creating components in a math-based environment dedicated to additive manufacturing end production can result in the most efficient use of materials, as well as help assure the maximum degree of weight optimization.

BMW claims to have produced more than 300,000 components via additive manufacturing in 2019. Milan Nedeljkovic, BMW AG board member for production said at the inauguration of the Additive Manufacturing Campus: “Additive manufacturing is already an integral part of our worldwide production system today and established in our digitalization strategy. In the future, new technologies of this kind will shorten production times even further and allow us to benefit even more fully from the potential of toolless manufacturing.”

The Additive Manufacturing Campus employs approximately 80 associates and operates about 50 processes for additive manufacture of both metal and plastic components. Another 50 systems are in operation at production sites around the world. Access to the latest technologies is gained through long-standing partnerships with leading manufacturers and universities, and by successfully scouting for industry newcomers, according to the company.

“Our goal is to industrialize 3D printing methods more and more for automotive production and to implement new automation concepts in the process chain,” said Daniel Schäfer, senior vice president for Production Integration and Pilot Plant for the BMW Group. “This will allow us to streamline component manufacturing for series production and speed up development. At the same time, we are collaborating with vehicle development, component production, purchasing and the supplier network, as well as various other areas of the company to systematically integrate the technology and utilize it effectively.”

BMW additive manufacturing line for non-metal components. (BMW)
Printing a component for BMW’s S 1000 RR superbike — on site at the track where the motorcycle is racing. (BMW)

The company said a chief purpose of the Additive Manufacturing Campus is to automate process chains that typically required a large degree of manual labor to make 3D printing more economical and viable for use on an industrial scale over the longer term. But it added that research projects also are a backbone of its efforts to expand additive manufacturing for automotive mass production and that it is collaborating with various research efforts to establish Germany as an additive-manufacturing pioneer.

Merging with the EV ecosystem

In late 2020, Porsche announced that it used additive manufacturing to produce its first complete housing for an electric vehicle (EV) traction motor/integral transmission drive unit. The case was 3D-printed via a laser-fusion process and met all of the company’s quality and stress metrics.

“This proves that additive manufacturing, with all its advantages, is also suitable for larger and highly-stressed components in electric sportscars,” said Falk Heilfort, project manager in the Powertrain Advance Development department at the Porsche Development Centre in Weissach, Germany. Porsche added that the 3D-printing process for the prototype part also allowed engineers to consolidate several development phases.

The 3D-printed drive-unit housing is approximately 10% lighter compared with a conventional cast-aluminum part. The process also enables the stiffness in highly stressed areas to be doubled. Multiple parts and their functions are consolidated, resulting in reduced assembly time and higher quality.

Porsche’s 3D-printed EV structure integrates the drive motor and a 2-speed transmission. It is designed for application on the front axle of a sportscar. A high-purity metal powder was employed for the laser metal fusion (LMF) process that uses a laser to heat and melt the metal to the specified part contours.

The weight of the housing parts was reduced by approximately 40% due to the integration of functions and optimization of part topology, Porsche claims, and helped deliver the overall weight savings of nearly 10%. But stiffness was simultaneously increased; although the housing has a continuous wall thickness of 1.5 mm (0.06 in.), the stiffness between the electric motor and gearbox was doubled due to the lattice structures the 3D-printed design included. Meanwhile, the honeycomb structure also reduces oscillations of the housing walls, improving the overall acoustics of the drive unit.

Integration of parts made the drive unit more compact, “significantly improved the drive package” and reduced the assembly by about 40 work steps – equivalent to reduction of production time of approximately 20 minutes. And overall performance and cooling is enhanced by integration of the gearbox heat exchanger and the resulting optimized heat transmission.