BMW introduced the four-cylinder B47 turbodiesel around four years ago as a modular drive system. It was then revised from the ground up in 2017, when all models became biturbo diesel units. While in the past only the most powerful version was fitted with two turbochargers, all versions of the unit now come with a two-stage BorgWarner turbocharging system. However, the focus was not on increasing performance here, but rather on optimizing consumption and emissions, while at the same time improving response and dynamic driving performance.
Largest project yet for BMW
The turbochargers of the new drive have been produced at BorgWarner in Kirchheimbolanden since September 2017. Assembly started with around 1,000 units per week, but this figure is set to be gradually ramped up the high series production requirements. “The is the largest industrialization project that we have ever handled for BMW,” stresses Markus Kreibiehl, who is responsible for the industrialization as Director Manufacturing Engineering together with his team. The assembly strategy being pursued by the experts is referred to as Smart Automation at BorgWarner. Kreibiehl explains: “We decided to go with automation, yet were also keen to strike the ideal balance between manual and automated processes. Our objective was not automation at any price, but rather optimization of availability and profitability.” Thomas Fitting, Head of Assembly Planning, adds: "We want to achieve a high OEE (overall equipment efficiency) of more than 80 percent.”
To facilitate a high degree of automation, the assembly specialists cooperated closely with BMW. Design for Assembly and Design for Automation were therefore already incorporated in a very early project phase. "We designed boreholes and recesses in line with the Design for Value principles, so that the bolted connections of the individual components could be automated," comments Fitting, explaining the procedure. The reward for the intensive development work? Time and cost savings during assembly – and the BorgWarner 2017 Innovation Award for the intelligent industrialization concept. The high pressure stage of the new R2S® system is the first BorgWarner turbocharger in the world ever to be assembled in a fully automated process.
Thomas Fitting (Head of Construction Planning) explains smart automation:
intelligent segregation of duties between manual and automated assembly
Thanks to its modular structure, the B47 assembly line offers a high degree of flexibility.
Design for Value: The special design of the impeller casing
is what makes automated assembly possible.
Automatically height-adjustable workplaces and newly designed light screens increase ergonomic standards at the assembly modules.
Assembly process in line with one-piece flow
“In terms of the conceptual design of the assembly process, we work to the onepiece flow principle,” explains Kreibiehl. “Assembly of the turbos is performed in a step-by-step process without any large buffer and with even balancing of the individual stations.” The objective of this concept is to detect and then eliminate disturbance variables or errors as quickly as possible. This improves both the transparency and quality of the assembly line. “Decoupling (supermarket) only takes place between core assembly and the final assembly line,” adds Dr. Jan-Niko Kranz, Assembly Planning Team Leader. “We achieve extremely high stability within the individual lines. However, we introduced decoupling between them so that any interferences from the core assembly process would not be transferred to the flow housing assembly line.”
Assembly modules increase flexibility
From a technical perspective, the assembly system has a fully modular structure. The number of standardized assembly modules has already been on the rise at BorgWarner for several years from project to project. “This increases the flexibility of our location,” comments Fitting, explaining the reasons. “If we need to make changes to the turbo or implement additional functions, we can quickly adapt individual modules or integrate new ones into the line.” The modules can also continue to be used with slight adjustments after production is phased out as a way of industrializing new products quickly. “By adding this flexibility to our assembly equipment, we are making targeted improvements to our competitiveness,” comments Kreibiehl, who goes on to add “With the increasingly modular assembly operations, we are also boosting our space productivity and therefore improving our profitability.”
The technological highlights of the B47 assembly system include an innovative end-of-line testing station. Using a turntable, this system employs various processes to test every single turbocharger automatically without any reclamping operations. Following a leak check, a dynamic cold testing process is performed with air. The temperatures, pressures, airborne sound, structure-borne sound, flow rates, and speeds are recorded and compared against target curves. “We have now been doing tests of this kind for seven years,” comments Kreibiehl. “We were among the very first manufacturers to subject every single turbo to cold testing in the series production process.”
Initial steps toward Industry 4.0
The first automated communication processes in the sense of Industry 4.0 represent another special feature of the new assembly system. “In cartridge assembly, the necessary air mass flow rate of every single cartridge is automatically measured and saved to a database,” comments Kranz. “The final assembly line automatically reads this measured value and uses it to adjust the travel of the electric actuator independently.” The basis for communication processes of this kind is exchange of data matrix codes between the individual assembly modules, which BorgWarner has already been using for quite some time.
The experts in Kibo are also proud of the new assembly system’s compliance with strict ergonomic standards. Since employees of different heights work at the workplaces on a rotating basis, the location collaborated with the manufacturer of the assembly modules to develop a flexible workplace design solution. When employees log in to the system with their card at the start of the shift, the respective workplace is then adjusted fully automatically to the optimum working height. “This is a real innovation for an automatic line and one which generally amazes anyone visiting our facility,” comments Kreibiehl. “We hope that this will offer us a gentler and therefore healthier way of working in the long term.” Further detailed solutions, such as optimization of light screens, are a component of the high ergonomic standard.
How did the series production start-up go on the new line? Kreibiehl: “We are really satisfied so far. We only had 13 to 14 months available from being awarded the contract to final acceptance by the customer." In this time period, the experts managed to successfully industrialize the line, implement design changes, and perform the validations. Thanks to the modular concept of the system, it was possible to integrate an additional bolted connection at a later date prior to the start of series production.
Fit for the future
“High flexibility, high availability, high productivity, yet also high ergonomics and high quality – these are the particular strengths with which our new assembly system can impress BMW,” comments Kreibiehl, summarizing the benefits of intelligent automation at BorgWarner. Fitting then adds: “The concept that we applied here will help us react more quickly to changes in future, as we can switch over the lines quickly for new projects.” The Kirchheimbolanden location therefore considers itself well prepared for future challenges – particularly with regard to the Kibo 2020 strategy. This states that production of small series will be transferred to other facilities by 2020 and the location will be switched over for large-scale series production and production of innovative products like the eBooster®.
From left: Dr. Jan-Niko Kranz (Team Supervisor for Construction Planning), Markus Kreibiehl (Director of Manufacturing Engineering), and Pascal Brehm (Director of Operations) in front of the new B47 assembly line.
The Kirchheimbolanden location was presented with the BorgWarner Innovation Award 2017 for the industrialization concept of the R2S® turbocharging system.
Fotos: © BorgWarner