本帖最后由 ayong 于 2010-9-13 20:43 编辑
The Manufacturing
Process
Components
1 The automobile assembly plant represents only the final phase in the process of manufacturing an automobile, for it is here that the components supplied by more than 4,000 outside suppliers, including company-owned parts suppliers, are brought together for assembly, usually by truck or railroad. Those parts that will be used in the chassis are delivered to one area, while those that will comprise the body are unloaded at another.
Chassis
2 The typical car or truck is constructed from the ground up (and out). The frame forms the base on which the body rests and from which all subsequent assembly components follow. The frame is placed on the assembly line and clamped to the conveyer to prevent shifting as it moves down the line. From here the automobile frame moves to component assembly areas where complete front and rear suspensions, gas tanks, rear axles and drive shafts, gear boxes, steering box components, wheel drums, and braking systems are sequentially installed.
Workers install engines on Model Ts at a Ford Motor Company plant. The photo is from about 1917.
The automobile, for decades the quintessential American industrial product, did not have its origins in the United States. In 1860, Etienne Lenoir, a Belgian mechanic, introduced an internal combustion engine that proved useful as a source of stationary power. In 1878, Nicholas Otto, a German manufacturer, developed his four-stroke "explosion" engine. By 1885, one of his engineers, Gottlieb Daimler, was building the first of four experimental vehicles powered by a modified Otto internal combustion engine. Also in 1885, another German manufacturer, Carl Benz, introduced a three-wheeled, self-propelled vehicle. In 1887, the Benz became the first automobile offered for sale to the public. By 1895, automotive technology was dominated by the French, led by Emile Lavassor. Lavassor developed the basic mechanical arrangement of the car, placing the engine in the front of the chassis, with the crankshaft perpendicular to the axles.
In 1896, the Duryea Motor Wagon became the first production motor vehicle in the United States. In that same year, Henry Ford demonstrated his first experimental vehicle, the Quadricycle. By 1908, when the Ford Motor Company introduced the Model T, the United States had dozens of automobile manufacturers. The Model T quickly became the standard by which other cars were measured; ten years later, half of all cars on the road were Model Ts. It had a simple four-cylinder, twenty-horsepower engine and a planetary transmission giving two gears forward and one backward. It was sturdy, had high road clearance to negotiate the rutted roads of the day, and was easy to operate and maintain.
William S. Pretzer
3 An off-line operation at this stage of production mates the vehicle's engine with its transmission. Workers use robotic arms to install these heavy components inside the engine compartment of the frame. After the engine and transmission are installed, a
On automobile assembly lines, much of the work is now done by robots rather than humans. In the first stages of automobile manufacture, robots weld the floor pan pieces together and assist workers in placing components such as the suspension onto the chassis.
worker attaches the radiator, and another bolts it into place. Because of the nature of these heavy component parts, articulating robots perform all of the lift and carry operations while assemblers using pneumatic wrenches bolt component pieces in place. Careful ergonomic studies of every assembly task have provided assembly workers with the safest and most efficient tools available.
Body
4 Generally, the floor pan is the largest body component to which a multitude of panels and braces will subsequently be either welded or bolted. As it moves down the assembly line, held in place by clamping fixtures, the shell of the vehicle is built. First, the left and right quarter panels are robotically disengaged from pre-staged shipping containers and placed onto the floor pan, where they are stabilized with positioning fixtures and welded.
5 The front and rear door pillars, roof, and body side panels are assembled in the same fashion. The shell of the automobile assembled in this section of the process lends itself to the use of robots because articulating arms can easily introduce various component braces and panels to the floor pan and perform a high number of weld operations in a time frame and with a degree of accuracy no human workers could ever approach. Robots can pick and load 200-pound (90.8 kilograms) roof panels and place them precisely in the proper weld position with tolerance variations held to within .001 of an inch. Moreover, robots can also tolerate the
The body is built up on a separate assembly line from the chassis. Robots once again perform most of the welding on the various panels, but human workers are necessary to bolt the parts together. During welding, component pieces are held securely in a jig while welding operations are performed. Once the body shell is complete, it is attached to an overhead conveyor for the painting process. The multi-step painting process entails inspection, cleaning, undercoat (electrostatically applied) dipping, drying, topcoat spraying, and baking.
smoke, weld flashes, and gases created during this phase of production.
6 As the body moves from the isolated weld area of the assembly line, subsequent body components including fully assembled doors, deck lids, hood panel, fenders, trunk lid, and bumper reinforcements are installed. Although robots help workers place these components onto the body shell, the workers provide the proper fit for most of the bolt-on functional parts using pneumatically assisted tools.
Paint
7 Prior to painting, the body must pass through a rigorous inspection process, the body in white operation. The shell of the vehicle passes through a brightly lit white room where it is fully wiped down by visual inspectors using cloths soaked in hi-light oil. Under the lights, this oil allows inspectors to see any defects in the sheet metal body panels. Dings, dents, and any other defects are repaired right on the line by skilled body repairmen. After the shell has been fully inspected and repaired, the assembly conveyor carries it through a cleaning station where it is immersed and cleaned of all residual oil, dirt, and contaminants.
8 As the shell exits the cleaning station it goes through a drying booth and then through an undercoat dip—an electrostatically charged bath of undercoat paint (called the E-coat) that covers every nook and cranny of the body shell, both inside and out, with primer. This coat acts as a substrate surface to which the top coat of colored paint adheres.
9 After the E-coat bath, the shell is again dried in a booth as it proceeds on to the final paint operation. In most automobile assembly plants today, vehicle bodies are spray-painted by robots that have been programmed to apply the exact amounts of paint to just the right areas for just the right length of time. Considerable research and programming has gone into the dynamics of robotic painting in order to ensure the fine "wet" finishes we have come to expect. Our robotic painters have come a long way since Ford's first Model Ts, which were painted by hand with a brush.
10 Once the shell has been fully covered 1 V with a base coat of color paint and a clear top coat, the conveyor transfers the bodies through baking ovens where the paint is cured at temperatures exceeding 275 degrees Fahrenheit (135 degrees Celsius).
The body and chassis assemblies are mated near the end of the production process. Robotic arms lift the body shell onto the chassis frame, where human workers then bolt the two together. After final components are installed, the vehicle is driven off the assembly line to a quality checkpoint.
After the shell leaves the paint area it is ready for interior assembly.
|