The Value of the Assembly Line in Automobile Manufacture

The Value of the Assembly Line in Automobile Manufacture

In 1913, an innovation in automobile manufacture was born when Ford Motors experimented with winches and ropes to pull the chassis down a line while the assemblers stood in one place with their parts piles. The old process where workers moved in teams down the line, receiving their car parts from "parts runners" at each chassis as they arrived, was replaced by the automated assembly line, thus radically reducing by about 70 percent the original 17-hour labor input in the traditional moving team system. Since then, cars began to be produced with increasing flexibility and economy.

The State-of-the-Art BMW Plant in Leipzig

The newly-opened manufacturing plant of BMW in Leipzig, Germany boasts of a high-tech assembly line that transports the chassis from one production station to another with the speed and ease that carries with it the promise of producing the planned capacity of 650 BMW vehicles per day by 2007. Located in three buildings arranged in a circle around the open-structure central building, the assembly line production is clearly visible to all employees. This pioneering architecture not only aims to promote transparency and communication among employees, but also reflects a plant-within-a-plant principle in which the operations are divided into three smaller operating units with focused objectives, namely, (1) the construction of the main framework, (2) the paint job, and (3) the assembly of other remaining car parts.

As far as operations are concerned, the site of the youngest BMW plant offers several advantages: accessibility (geographical center of Germany) from the BMW Group's existing supplier network; abundance in potential employees (the region has almost 20 percent unemployment rate); a relatively cooperative workers' union (the IG Metall Union agreed to a number of BMW's demands such as flexibility in hours in running the machines); and subsidization by the local government of as much as 30.1 percent (about $500 million) of the total investment costs (over $1.59 billion) following the full construction of the plant.

The Assembly Line and Rate of Production

The automotive assembly line in the BMW Plant just recently began producing the X5 SAV and Z4 Roadster. While there are slight differences between the procedures of creating the two variants, specifically with regard to the smaller segments or sub-units of the operation, the core operation flows for both cars are essentially the same. The assembly line of the two variants efficiently follow the same sequence: first, the vehicles are brought to the body shop where the small car parts are welded into the underbody by robots and assemblers; next, the cars are brought to the paint shop where several coatings of environment-friendly paint and sealant are sprayed onto the car body; and finally, the remaining parts are assembled into the vehicles in the assembly halls. Each stage is further divided into different mini-segments; for example, the paint job stage is made up of several coating sessions, oven drying sessions and quality inspection sessions.

But more importantly, the both cars' operations are significantly made easier and faster by the state-of-the-art assembly line production system, escalating the rate of production. Unlike in the past decades when "parts runners" would swarm the manufacturing plant handing various parts to the assemblers who go down from one chassis to another, the assembly line makes it possible for the assemblers and robots to stay put as the conveyor belt transports the cars from one station to the next in a more precise and fluid manner. The technology also allows assemblers to work on the cars from a more convenient chest-high height, unlike before. For example, the conveyor in the tilt station rotates the vehicle about 90 degrees from horizontal, so it is ergonomically easier for the assembler to install the fuel and brake system components. Furthermore, at the Leipzig plant, supply routes surround the central building, so that parts delivered by truck do not have to be taken more than seven meters to their installation points.

Indeed, the company's efficient assembly line production system conforms with the manufacturing principle of simplifying operations into standardized flows to achieve optimum results. It has gone a long way from Ford's archetype assembly line of "winches and ropes." Yet, notwithstanding the various advantages that car manufacture has enjoyed on account of the assembly line, there is one fundamental disadvantage that merits reference. Ironically, its most significant advantage - that the assembly line moves automatically - can also be considered its liability, at least from the point of view of the assemblers. That's because as the assembly line moves along they may have to walk backwards and contort their bodies in order to get particular components installed. One consequence of this balancing act is that the assemblers might lose concentration on the task at hand, leading to quality issues. Fortunately for the BMW plant, such so-called bugs have been worked out and eliminated to guarantee excellent quality. There are also enough inspection stages spread throughout the entire course of production to undo any mistakes as early as possible. Thus, this minor glitch is almost negligible in view of the enormous impact of the automated assembly line on the rate of production and product quality. That is, besides a big surge in output figures, the unprecedented speed at which the automobiles were made also inevitably reduces opportunities for committing errors.

Process Selection and Capacity Planning

A vital issue during product design is the performance of the manufacturing system. After all, product design, which requires a specific set of manufacturing operations, has a huge impact on the manufacturing system performance. One example that can be cited is the length of a new vehicle's chassis, which is a critical design variable that must be determined early on in the vehicle development process, so as to avoid expensive (and quite unnecessary) modifications to the robotic assembly line that will construct the vehicle. Meanwhile, automobile makers use the "continuous process" type of operations, in which the manufacturing system is capable of producing a few standardized designs in very high volumes.

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