Assembly islands instead of assembly lines

For more than 100 years, production in the automobile industry has followed the pace of the assembly line. Audi is now working on a vision for the era after the assembly line and is developing a completely new principle: modular assembly. With this new method, the company intends to cope better, more flexibly and more efficiently with growing complexity and the increasing numbers of model versions.

On January 14, 1914, Henry Ford started the first full assembly‑line production in the automobile industry in his newly built “River Rouge” factory in Dearborn, USA. Since then, this principle has formed the backbone of large‑series production. In 1925, it was adopted for the production of motorcycles by DKW, one of the predecessor brands of today’s AUDI AG. At Audi’s plant in Ingolstadt, the assembly lines are running for the models Audi A3, A4, A5 and Q2. On each of the three assembly lines, a car is produced every 88 seconds, so together, the three lines produce a car about every 30 seconds – the Ingolstadt plant is the second‑largest car factory in Europe.

Despite the high numbers of cars produced and the well‑established routines, Audi is convinced that the assembly line has had its day. Because as model diversity grows, the more complicated it becomes to master the complexity in a rigid sequential process and to integrate more and more new working routines. 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. These losses accumulate with an increasingly heterogeneous model mix on the line.

It becomes even more difficult when sharply differing versions are on the same line. One example is the assembly of the Audi 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.

Audi’s answer to this challenge is a completely new concept: modular assembly. The idea behind it is production without assembly lines, broken down into the individual work stages. The new assembly stations are occupied by one or two workers. Unlike today, they work steadily at a continuous pace, because they no longer have to adapt their activities to the speed of the line. And they do not have to move with the car on a conveyor; they can work in one place.

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 (see separate chapter). Their movement is exact to the nearest centimeter and is controlled by radio; a central computer guides them as required.

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. The so‑called supermarkets, which are today used to commission the parts and in some cases are located in logistics centers outside the plants, are no longer necessary in this form; they are either abolished or transferred into the assembly halls.

Unlike on the assembly line, the routines in modular assembly are highly flexible with regard to time and space. For example, the installation of door seals with a coupe takes half as long as with a four-door sedan. 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. Because for the car, it is irrelevant whether its trunk cladding is installed before or after its door seals.

The integration of an e-tron derivative or other variant is also no longer a problem with modular assembly. 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.

When considering the entire system including logistics, Audi expects modular assembly to result in a productivity advantage of about 20 percent plus x. The size of that “x” will increase along with the growth in version diversity. Intelligent driverless transport systems, which have long offered potential also for other companies, will become less expensive as they are produced in larger numbers, offering further potential to reduce costs.

For the development of modular assembly, a startup company by the name of “arculus” was established in a disused factory building near the Ingolstadt plant in spring 2016; Audi holds a stake in arculus. The decision to outsource the implementation of modular assembly to a startup has proven to be absolutely right: Within a few months, the small, highly motivated team built its first working demonstrator. In doing so, it resolved all the fundamental questions itself; there was no supplier on the market that could have mastered the equipment and its central guidance at the same time.

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.