The Ultimate Printing Machine - How BMW is applying 3D printing to commercial vehicles

Head of Content, Daniel O'Connor reports on a visit to BMW's Additive Manufacturing Center in Munich.

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WINNER of the TCT Automotive Award 2018. Submit your design-to-manufacturing innovation for this year’s TCT Awards here.

The opening keynote of the 2014 edition of TCT Show by Dr. Hans Langer, CEO of EOS, detailed how, as a start-up in the late 80s, the Munich-based company went, without a machine, looking for a customer.

Using his years as a laser production professional, Langer managed to get through the doors at the BMW Group, where a team had analysed every detail of the 3D printers in the market and were becoming increasingly frustrated with the machinery’s constraints. Within a year of that meeting, EOS had built their first stereolithography machine to the exacting specifications of the BMW Group.

The BMW Group has always been and still is, at the vanguard of 3D printing technology. Look at the recent investments in Desktop Metal and Carbon as well as its crucial role in the HP Beta Test program. It has been pushing the envelope of what is possible ever since those days in the 80s of prototyping with frustrating SLA machines.

Dr.-Ing. Dominik Rietzel and Dr.-Ing. Maximilian Meixlsperger head up BMW Group’s Additive Manufacturing Center for non-metal and metals respectively. Together with their teams, they have overseen something of a revolution within BMW Group that has not only advanced prototyping beyond fit and form but delivered on 3D printing’s promise to become a technology capable of both mass consumer customisation and the series production of parts. 

Paramount Prototyping

Prototyping is, like every other business in the world, still the core application for additive manufacturing technology within the BMW Group. You’d be forgiven for assuming that with 30 years of use, the BMW Group would claim to have perfected the process, but during a tour of the Additive Manufacturing Center (AMC) in Munich, Dominik was keen to demonstrate how this implementation is still, very much, an ongoing journey. 

A project Dominik is particularly proud of involves a dashboard that he saved from recycling to put on display inside the AMC. This SLS printed dashboard appears, at first sight, to be like any other, but to the touch, the white powdery part is both spongy and stiff in the appropriate places.

The dashboard’s feel is down to a PhD work on TPUs conducted at the AMC; the research led to the development of a printing technique that replicated the feel of foams used within BMW Group series production.

“In prototyping, it is essential to have the real properties of the actual product,” stated Dominik. “For example, if you have an undercut that needs to be fixed to the dashboard, it might work with a stiff prototype, but when it comes to serial production one, maybe it might not work.”

Today, every single dashboard prototyped within BMW Group uses that method developed by their research.

Prototyping, spare parts, jigs and fixtures, tooling, even augmented orthotic thumbs for assembly line workers - whereas many companies are just gearing up for these applications, they have been standard processes for BMW Group for many years. What isn’t standard practice is two projects coming out of AMC in the past year.

For years we’ve heard talk of additive manufacturing for series production, the truth is that relatively few companies have implemented a process with qualification and repeatability often the rate-limiters. Rather than wait around for the OEMs to bring the technology up-to-scratch or some organisation to create documentation on best-practice for qualification, the AMC went and did it themselves, uniquely in both polymer and metal 3D printing. 

A Mini revolution

The first project to hit the press was ‘MINI Yours Customised’, which sees the MINI brand make a play for the ever-expanding car personalisation market.

Car personalisation is big business; during 2017, in the UK alone, the Driver and Vehicle Licensing Agency sold a record 374,968 personalised registration plates amassing £110m. New marketing campaigns from the Nissan Micra and Citroen C3 focus on a wide array of colours and styling. Those campaigns are proving to be a hit with Nissan saying that 18% of customers are choosing to personalise their vehicle.

Neither of those examples is true mass customisation; registration plates have strict criteria to match, and there’s a finite number of possibilities; and with the exterior styling, the Nissan Micra has only 100 combinations to choose from. No, for true mass customisation there’s only one tech you can turn to, 3D printing and BMW Group has done just that.

Using the MINI Yours Customised configurator, a customer can select a colour, change the pattern, add their name and add an icon to door sills, a door projector, a cockpit fascia or/and the side scuttles. The latter two are both 3D printed en-masse by Dominik and his team at the AMC using a host of 3D printing platforms including Carbon’s CLIP, HP’s Multi-Jet Fusion (MJF) and EOS’s SLS technology.

“We took the momentum to approve different technologies and different materials,” explains Dominik. “If we go through this routine of qualification once on a powder based technology and a resin-based technology then we learn so much for the next project.”

By setting up MINI Yours Customised, many different disciplines, like IT, sales, materials research and design needed to work closely with the AMC in a start-up manner to create this unique offering.

Once the design is complete and the customer places an order, the job appears in the same customer ordering system as an internal prototype part ordered for a car five years away from production with AMC acting like an in-house service bureau.

“If you work at the BMW Group you can upload a part directly from CATIA into our system and say I want to have a prototype in a specific AM technology with this specific material,” reveals Dominik. “You see an online pricing system, and you place the order. We developed this software platform years ago and are still improving it.”

Manufacturing an individually tailored part like the cockpit fascia for a premium brand like MINI isn’t as easy as when, others print o a personalised phone case. The cockpit fascia has to be configured to the tightest of tolerances - so accurate that the customer can easily snap-fit and remove if needed. The part has to stand up to the rigours of constant sunlight, plummeting and skyrocketing temperatures, drink spills, grubby hands, finger drumming and most-importantly crash impacts. Therefore, the team developed an own “Digital Craftsmanship” process that includes printing of the parts, surface finish and manual painting according to premium automotive standards.

Unlike the exterior side scuttles, an interior part like the cockpit fascia has to withstand a full impact crash and not shatter. If it were to break the shrapnel could cause injury. The testing to get the parts to a point whereby BMW Group were happy for the components to be placed inside a car has taken a considerable amount of time. Because of the safety requirements the cockpit fascia is currently only printed using  polyamide 11 on SLS systems, whereas the side scuttles can be manufactured on EOS, HP or Carbon machinery.

“We start, we learn and we improve,” says Dominik. “In the area set up for [Carbon’s] CLIP technology we’re testing with robots for automation; opening the machine, getting the build job out, placing the tray, getting the parts out of it, putting them into the oven all automatically. We are still in a test mode, but as soon as I have this cell working, we can create all the documentation around it and then we scale it up. I will know how many robots I need for how many printers, how many part washers, what kind of ovens. We benchmark all the products in the process chain; we benchmark ovens, we benchmark the robots, we benchmark the grippers. We are not only working on 3D printing.”

One of the first MINI Yours Customised cars to be seen in the wild was designed as a gift for the royal wedding of Harry and Meghan. The MINI Hatch model had Harry and Meghan side scuttles as well as a 3D printed fascia and was auctioned for the official Royal Wedding charity, Children’s HIV Association.

The care and attention given to the Royal Wedding car comes as standard for every part that leaves the AMC. The life of every component can be readable using a camera monitoring system; the printed part contains a host of information including a machine code, a materials code and a customised part ID. Each part is inspected at every step of the process documenting the quality and appearance. In doing so, the team has also worked out a comprehensive blacklist of text that inhibits consumers from using offensive language or infringing copyrights.

If any part does not meet the BMW Group’s exacting standards, the AMC starts the process again. The traceability even helps in the long run: “Let’s say there’s been a crash, and a side scuttle was damaged,” considers Dominik. “I can go back to the system and see the part ordered ten years later and reprint that exact same part for the customer.”

A new Series

Since the dawn of metal 3D printing at the turn of the millennium, OEMs have been shouting from the rooftops about the potential of series production. However, relatively few projects have seen the light of day with GE’s LEAP fuel nozzle proving pretty much the only visible project in the world.

There’s no denying the LEAP fuel nozzle’s ingenuity and worth - it proved the catalyst for GE’s billion-dollar metal 3D printing acquisitions - but we learned about that five years ago. We need another example of metal 3D printing’s capacity else the cries of one-trick pony may start ringing in the ears of machine buyers.

Step forward Dipl.-Ing. Maximilian Meixlsperger, who heads up metal additive manufacturing at BMW Group. Max and his team are here to silence those naysayers with the first cost-effective series production of a metal additively manufactured component in the commercial automotive industry. This is not an impeller for a one-of-a-kind racecar or a reverse-engineered handle for a classic car; two of these components are on every model of the BMW i8 Roadster.

The part in question is a topologically and production process optimised fixture for the folding mechanism of the BMW i8 Roadster’s soft top; folding mechanisms are traditionally quite cumbersome and add significant weight to cars all while taking up valuable boot space.

Optimise the AMC did, not only did they make a 10 times stiffer part than the plastic injection moulded counterpart, they made the metal part 44% lighter at the same time as developing some novel printing techniques and build orientations to ramp up cost efficiency.

“Normally underneath a part like this you’d have support, but we optimised it to a point where we no longer needed support structures,” states Max. "The part has two little feet that are the only connection to the base plate. Using this method we were also able to stack them into each other and take the build from 51 to 238 parts per platform.” Realising all this they made the part cost efficient up to 60,000 components against metal die casting.

The fixture is currently manufactured in the AMC using one qualified SLM Solutions machine, printing round the clock in AlSi10Mg. Max’s team is now working on qualifying a second and third SLM Solutions machine, one installed at the AMC and the other in the BMW Group plant in Landshut.

“We took about half a year exploring the qualified machine,” said Max. “Understanding, optimizing and technically safeguarding the way that we produce today. We did a lot of reproducibility testing; doing the same test over and over, taking parts out, testing them and in the end, we showed that this is now a reproducible production process.”

The BMW i8 Roadster and the MINI Yours Customised projects have proved, without question the viability of 3D printing technology in the automotive industry. With a move to a new €10 million Additive Manufacturing Campus pencilled in for early 2019, Dr. Jens Ertel, Head of the BMW Group’s Additive Manufacturing Center and the future campus director, adds: “Our new facility will be a major milestone in additive manufacturing at the BMW Group. The team there will evaluate new and existing technologies in both plastics and metals printing and develop them to series maturity. Our goal is to provide the optimum technology and process chain, be it for individual components, small production runs or even large-scale manufacturing.”

Both the Mini Yours Customised and the i8 Roadster bracket have made the shortlist for the 2018 TCT Awards. To attend the awards ceremony on 26th September, get your tickets here.

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