By Katrin Pudenz
Audi is planning to replace the assembly line with the new modular assembly concept. Professor Dr. Hubert Waltl, Board of Management for Production at Audi explains: "Our aim is to react to the changing demands of our customers as quickly as possible. They expect a seamless integration of their car into the digital environment, sustainable drives, and new solutions for urban mobility - all included in a customized product tailored to their specific needs. Ultimately, these demands also set the pace in production, which is why are developing alternatives to the traditional assembly line. After all, there is a far more intelligent approach than just working at the pace of the machines." The new, small, separate workstations included in this concept allow highly flexible workflows - both in terms of time and space. This principle was developed by the Audi start-up company arculus. Fabian Rusitschka is the company's CEO and one of three Managing Directors. Rusitschka studied mechanical engineering and is a former Audi employee. He worked in the technology development department of Audi production until March 2016, before venturing into self-employment. "Originally, we were looking for a supplier for our project who would be tasked with developing the systems and their central control at the same time," Rusitschka reports. "But we couldn't find anyone who was able to do this. So we did it ourselves and founded arculus - the first spin-off from Audi in this field."
First complete assembly line production in automotive history
But why is the assembly line now considered to be old-fashioned? Its history dates back to the Venetian Arsenal of the late 15th century. Later, Henry Ford took inspiration from the "disassembly" lines in Cincinnati's slaughterhouses. Back then, elevated conveyor belts were used to transport slaughtered pigs from one worker to the next. Henry Ford took the idea and built a permanent assembly line, known as the first moving assembly line. This made it possible for Ford to increase production eight-fold, while reducing the price for his Tin Lizzy T-model and increase workers' wages. Based on this success, Ford built a new plant on the River Rouge in Detroit and launched the first complete assembly line production in automotive history on January 14, 1914. Since then, this principle has formed the backbone of all large-scale series production lines.
At Audi's plant in Ingolstadt, the assembly lines are running for the models A3, A4, A5 and Q2 - finishing one car every 88 seconds. Together, the three lines produce a car about every 30 seconds. Despite the high numbers of cars produced and the well established routines, Audi is convinced that the assembly line has had its day. "The assembly line is used as a synonym for efficient production," says Fabian Rusitschka. "It was the ideal solution for many decades."
New assembly approach due to the growing model diversity
According to the company's production specialists, "it is becoming ever more complicated to master the complexity in rigid sequential processes and to integrate more and more new working routines as the model diversity grows. The fixed tempo leads to inactivity on many sections of the line - for example for the installation of optional extras such as auxiliary heating systems, which only a small proportion of the cars are fitted with." The experts also cite the large range of different versions on the assembly line, for example the assembly of the A3 Sportback E-tron in Ingolstadt. The plug in hybrid model, which accounts for only a relatively small percentage of the overall Audi A3 production, passes through seven separate workstations, where it receives a large proportion of its electrical equipment. While this is going on, its sister models with conventional drive move along the conveyor belt suspended below the ceiling; they are not worked on during this time, so the time until completion becomes longer for all the cars on the line.
The concept of modular assembly
To master this problem, the production experts at Audi developed the concept of modular assembly. The idea behind it is production without assembly lines, broken down into individual work stages. The new assembly stations are occupied by one or two workers. The specialists emphasize that modular production essentially eliminates rigid cycle times. The duration of the work steps is determined by what they entail, lasting between one and four minutes. Work is performed steadily at a continuous pace because the workers no longer have to adapt their activities to the speed of the assembly line. They no longer have to move with the car on the conveyor and do not need to walk back to their starting position.
According to Audi, the A3/Q2 line currently includes about 160 work steps. "In modular assembly, we turn this into approximately 200 spatially separated stations with one or two employees per station. The processes are quite different at each station, lasting between 60 and 240 seconds. And they are flexible," says Rusitschka.
Audi expects productivity increase
The transport of the car bodies and components between the stations in modular assembly is taken over by driverless transport systems. Audi is currently developing new systems of this kind that can navigate themselves and thus move with great flexibility. Their movement is exact to the nearest centimeter and is controlled by radio; a central computer guides them as required. This makes the central computer a sort of mastermind for the new assembly principle. After all, it knows the status of production down to the smallest detail. "It knows the assembly status of each car and which stations need which parts when and how they receive them," Rusitschka explains. When the central computer recognizes a jam at a station a driverless vehicle is heading for, it can often redirect it to another vacant station.
"The principle of modular assembly is characterized by a high spatiotemporal dynamic and the routes are subject to constant change," explains Fabian Rusitschka. "Much like a chess player, our controller has to anticipate multiple steps in advance."
The central computer monitors and manages all activities in the assembly hall so that they run smoothly and very efficiently. Small driverless vehicles supply the stations just in time with the components they need - from screws to sliding roofs.
Reacting quickly and effectively to new trends
When considering the entire system including logistics, Audi expects modular assembly to result in a productivity increase of about 20 percent plus x. The size of that "x" will increase along with the growth in version diversity.
This means that Audi can react quickly and efficiently to new trends and demands in the market, as well as to changing statutory requirements. Today, model changes lead to a standstill of the entire line. In the future, it will be possible to renew the affected stations while the others continue with normal operations.
The implementation of modular assembly in series production is not far away. Audi will first apply the new principle for test purposes in the production of engines at the plant in Győr, Hungary. Implementation with two other projects is also planned.
VDMA expert Sascha Schmel says:
"Further automation and improved flexibility is the motto of the day in production logistics. Sooner or later, automation will turn into autonomization. But this is a challenge the intralogistics sector will gladly take on. The association supports this trend on several levels, including through dialog platforms with customer sectors and its own assessments of the future."