Under the Hood: BMW Talks In-House 3D Printing

The auto industry was one of the first to implement 3D printing technology when it was invented over 30 years ago, back when it was called “rapid prototyping.” The technology is now maturing to the point that it can be used to manufacture end parts, and the automotive sector is again quick to recognize the potential.

The Rolls-Royce Phantom includes 10,000 3D-printed parts. (Image courtesy of the BWM Group.)

Throughout this history, the BMW Group has been an early adopter of 3D printing systems, first leveraging early 3D printers for prototyping purposes and, more recently, for serial production. In fact, the Rolls-Royce Phantom features 10,000 additively manufactured parts, demonstrating BMW’s overall confidence in the technology and the ability to wield it.

Now that entirely new 3D printing processes are being invented, such as those from Carbon and HP, BMW has quickly seen the potential of these novel systems in an attempt to stay ahead of the cutting edge and ultimately produce better cars. The manufacturing conglomerate is an early customer of both Carbon’s ultrafast and layerless M1 3D printer as well as HP’s Multi Jet Fusion (MJF) process.

Jens Ertel, head of the BMW Group’s Additive Manufacturing Center. (Image courtesy of the BWM Group.)

To better understand how the BMW Group is using this technology in-house, ENGINEERING.com turned to Jens Ertel, head of the BMW Group’s Additive Manufacturing Center at the company’s Research and Innovation Center, who was able to provide an inside look at BMW’s experience with 3D printing.

3D Printing History at BMW

The BMW Group has been relying on 3D printing technology for over 25 years, initially using it to produce predevelopment models for vehicle validation and testing or for concept cars and show cars.

Tooling 3D printed with stereolithography at BMW. (Image courtesy of the BMW Group.)

Ertel elaborated on the transition from 3D printing as a prototyping process to an actual additive manufacturing technology: “Due to our product portfolio, it was obvious for us to use 3D printing or, better, additive manufacturing for more than just prototyping. Subsequently, we started doing our own research on the materials and technologies. Based on these activities, we are continuously screening possible parts and try to find projects where a positive business case is given and where additive manufacturing fits to the specifications. Due to improvements in machine technologies and materials, we had the chance to do those further steps.”

A selective laser melting 3D printer at BMW. (Image courtesy of the BMW Group.)

Metal 3D printing is a technology barely over a decade old, yet BMW began using it early on. “[I]n the area of metal 3D printing, the BMW Group has an expertise for more than 10 years as an early adopter in that field,” Ertel explained. “The major use is for test vehicles to be used for functional testing of metal components.” This experience was able to give the group an early leg up when it came to serial production.

The group was able to roll out its first series 3D-printed part in 2010. This 3D-printed water pump wheel is still manufactured for Deutsche Tourenwagen Masters (DTM) racecars today, with over 650 of these water pump wheels produced to date, according to Ertel. “As final metal product, BMW currently produces water pump wheels for DTM racecars using additive production methods. The high-precision component, which is subject to high stresses, consists of an aluminum alloy and has previously proven its worth in the tough environment of motorsports,” Ertel said. “Without exception, all pump gear works flawlessly.”

A 3D-printed water pump wheel for use in a DTM racecar. (Image courtesy of the BMW Group.)

A manufacturer like BMW hasn’t just begun using 3D printing for novelty’s sake, however. The technology is an ideal one for manufacturing geometrically complex parts that might be impossible with other processes or components for specialty vehicles that may not be produced at the same scale as more common cars.

Ertel used the DTM water pump wheel as an example. “Additive manufacturing as a production method has turned out to be the ideal procedure for the small batch,” he pointed out. “Firstly, it allows for the inclusion of design refinements in the six-bladed centrifugal pump wheel, whose implementation would require much greater effort with other production methods. With the new method, it was possible to achieve ideal aerodynamics of the component for the DTM race series. Secondly, no complex tools or molds are needed, which makes the demand-oriented production more cost effective.”

Ertel added, “On top of that, 3D printing ensures the dimensional accuracy of the water pump wheel over the entire production time. BMW applies the homologated high-precision part both in the DTM racecars and in the Z4 GT3 customer vehicles.”

The Rolls-Royce Phantom and Dawn

In 2012, the BMW Group began to use 3D printing to produce parts for the Rolls-Royce Phantom, before GE even began manufacturing its widely trumpeted fuel nozzle for the LEAP jet engine. According to Ertel, the parts included “[p]lastic holders for hazard-warning lights, center lock buttons, electronic parking brakes and sockets.”

3D-printed parts for the Rolls-Royce Phantom. (Image courtesy of the BMW Group.)

Since then, the company has begun 3D printing mounting brackets for fiber optic cables in the new Rolls-Royce Dawn and plans to “install several thousand of these clips throughout the model lifecycle.”

The interior of the Rolls-Royce Phantom, with 10,000 3D-printed parts. (Image courtesy of the BMW Group.)

The reasoning behind 3D printing the clips is the intricacy of their design. While they might be produced with conventional processes, BMW deemed that production times could be greatly reduced with 3D printing, while still achieving the necessary standards. “These filigree parts are very complex, and the material fully meets the specifications—so we could switch the manufacturing technique to additive manufacturing,” Ertel said.

Future 3D Printing Technologies

Just as the BMW Group was quick to employ metal 3D printing processes, the group is one of the first customers for both Carbon and HP, which BMW believes may be essential to the use of 3D printing for the production of end parts. Ertel suggested that the reason for this is the high speed and low cost of these new processes.

Carbon’s continuous liquid interface production (CLIP) technique is capable of 3D printing parts in mere minutes. CLIP 3D printing sees a digital light processing projector cast UV light through an oxygen-permeable optical window onto a vat of proprietary photosensitive resin.

This optical window enables the system to cure the photopolymers much more quickly and makes it possible to print isotropic parts, in which the physical properties are the same across the X-, Y- and Z-axes, unlike other 3D printing technologies. A secondary curing process further allows these parts to become even more durable. Altogether, objects printed with CLIP are closer to injection-molded parts than those made with other 3D printing processes.

MINI nameplate 3D-printed with CLIP. (Image courtesy of the BMW Group.)

BMW has already begun using CLIP to 3D print personalized side indicators for BMW’s ride-sharing initiative called “DriveNow.” For the project, BMW invited German customers to vote on names for the 100 MINIs in the DriveNow fleet. The winning names were then 3D printed with CLIP and applied to the exterior of the vehicles.

Nameplates 3D-printed with CLIP technology. (Image courtesy of the BMW Group.)

In contrast to CLIP, HP’s MJF relies on a combination of binder jetting and infrared fusion to produce objects. A printhead deposits 30 million drops of fusing and detailing inks per second onto a bed of powder before a set of infrared lamps passes over and binds the fusing agents together, resulting in increased speeds. BMW plans to first use the technology for prototyping before moving to end production.

Ertel said that both CLIP and MJF, “planar” processes, as he refers to them, will speed up production times without raising costs. “The new planar 3D printing technologies will enable much faster production times and more economical production in the future, compared to conventional point-to-point 3D printing methods. Beamers or infrared sources are used to expose the full surface or bigger areas, rather than point-to-point, high-priced light sources such as CO₂ or UV lasers,” Ertel explained.

He added, “Today, planar technologies seem to be central to the use of additive processes in series production. The most recent example can be found in the preliminary trials of the HP MJF technology. The process will initially be used in prototyping, but we plan to extend it into series production over the long term.”

CLIP and MJF are only the most recent examples of BMW’s adoption of 3D printing technology. Based on the company’s track record, it’s clear that BMW will continue to utilize whatever may be the most cutting-edge manufacturing process at the time. Ertel concluded, “Additive technologies will be one of the main production methods of the future for the BMW Group—with promising potential. The integration of additively manufactured components into Rolls-Royce series production is another important milestone for us on the road to using this method on a large scale. By utilizing new technologies, we will be able to shorten production times further in the future and increasingly exploit the potential of tool-less manufacturing methods. On the way to a wide application in series manufacturing, there will be further milestones that have to be made to prove the technological and economical maturity of this relatively young technology. But from what we know now, it seems promising enough for us to take this journey.”