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AUTOMOBILE ASSEMBLY LINE
By:
Zainab Telya
AUTOTRONICS
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What is an Assembly Line?
An assembly line can be defined as amanufacturing process in which raw materials or
parts are added to a product in a sequential
manner to create a finished product.
An Assembly Line consists of workers and
machines organized into a continuous flow of raw
materials.
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Automobile Assembly Line
Automobile Assembly lines are designed for thesequential organization of workers, tools or
machines, and parts. The motion of workers is
minimized to the extent possible. All parts or
assemblies are handled either by conveyors ormotorized vehicles such as fork lifts, or gravity, with
no manual trucking. Heavy lifting is done by
machines such as overhead cranes or fork lifts.
Each worker typically performs one simpleoperation.
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History of the Car Assembly LineIn 1908, Henry Ford began production of the T-Model automobile. Its creation inaugurated what
we know today as the mass production assembly
line. This revolutionary idea was based on the
concept of simply assembling interchangeable
component parts. Prior to this time, coaches and
buggies had been hand-built in small numbers byspecialized craftspeople who rarely duplicated
any particular unit. Ford's innovative design
reduced the number of parts needed as well as
the number of skilled fitters who had always
formed the bulk of the assembly operation.Ford's first venture into automobile assembly with the Model A involved setting
up assembly stands on which the whole vehicle was built, usually by a single
assembler who fit an entire section of the car together in one place. This person
performed the same activity over and over at his stationary assembly stand. To
provide for more efficiency, Ford had parts delivered as needed to each work
station. In this way each assembly fitter took about 8.5 hours to complete his
assembly task. By the time the Model T was being developed Ford had decided
to use multiple assembly stands with assemblers moving from stand to stand,each performing a specific function. This process reduced the assembly time for
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Principles of an Assembly Line
According to Henry Ford; The principles of assembly are
as follows:
1. Place the tools and the men in the sequence of the
operation so that each component part shall travel theleast possible distance while in the process of finishing.
2. Use work slides or some other form of carrier so that
when a workman completes his operation, he drops the
part always in the same placewhich place must
always be the most convenient place to his handand
if possible have gravity carry the part to the next
workman for his operation.
3. Use sliding assembling lines by which the parts to be
assembled are delivered at convenient distances.
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The manufacturing process of a car
(Assembly Line) consists of thefollowing steps:
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Components
Nowadays, most of the car parts aremanufactured away from the assembly plant and
are transported to the plant by the means of
railroads or by trucks.
These parts are either manufactured by the same
company or are provided by outside suppliers.
More than 4000 parts are all brought together at
the plant for assembly.
Parts used in the chassis are delivered to one
area whereas the parts used in the body are
unloaded at another.
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Chassis Assembly A typical car is constructed from
ground up (and out).
The frames 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 framemoves to component assembly areas
where complete front and rear
suspensions, gas tanks, rear axles
and drive shafts, gear boxes, steering
box components, wheel drums, andbraking systems are sequentially
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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 worker
attaches the radiator, and other bolts it into place. Because of thenature 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.
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Body Assembly
The body is built up on a separate assembly line from the chassis.
Robots 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.
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.
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The front and rear door pillars, roof, and body side panels areassembled in the same fashion. The shell of the automobileassembled in this section of the process lends itself to the use of
robots because articulating arms can easily introduce variouscomponent braces and panels to the floor pan and perform a highnumber of weld operations in a time frame and with a degree ofaccuracy no human workers could ever approach. Robots can pickand load 200-pound (90.8 kilograms) roof panels and place themprecisely in the proper weld position with tolerance variations held
to within .001 of an inch. Moreover, robots can also tolerate thesmoke, weld flashes, and gases created during this phase ofproduction.
As the body moves from the isolated weld area of the assemblyline, subsequent body components including fully assembleddoors, deck lids, hood panel, fenders, trunk lid, and bumper
reinforcements are installed. Although robots help workers placethese components onto the body shell, the workers provide theproper fit for most of the bolt-on functional parts usingpneumatically assisted tools.
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Painting
Prior to painting, the body must pass through a
rigorous inspection process, the body in
whiteoperation. 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 sheetmetal 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. As the shell exits the cleaning station it goes through a drying booth and then
through an undercoat dipan electro statically 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.
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After the E-coat bath, the shellis again dried in a booth as it
proceeds on to the final paintoperation. In most automobileassembly plants today, vehiclebodies are spray-painted byrobots that have beenprogrammed to apply the exactamounts of paint to just theright areas for just the rightlength of time. Considerableresearch and programminghas gone into the dynamics ofrobotic painting in order toensure the fine "wet" finishes
we have come to expect.
Once the shell has been fully covered 1 Vwith a base coat of color
paint and a clear top coat, the conveyor transfers the bodiesthrough baking ovens where the paint is cured at temperaturesexceeding 275 degrees Fahrenheit (135 degrees Celsius).
After the shell leaves the paint area it is ready for interior assembly.
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Interior Assembly The painted shell proceeds through the interior assembly
area where workers assemble all of the instrumentationand wiring systems, dash panels, interior lights, seats,door and trim panels, headliners, radios, speakers, allglass except the automobile windshield, steering column
and wheel, body weather strips, vinyl tops, brake and gaspedals, carpeting, and front and rear bumper fascias.
Next, robots equipped with suction cups remove thewindshield from a shipping container, apply a bead ofurethane sealer to the perimeter of the glass, and then
place it into the body windshield frame. Robots also pickseats and trim panels and transport them to the vehicle forthe ease and efficiency of the assembly operator. Afterpassing through this section the shell is given a water testto ensure the proper fit of door panels, glass, andweatherstripping.
It is now ready to mate with the chassis.
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Mating The chassis assembly conveyor and the body shell conveyor
meet at this stage of production. As the chassis passes the body
conveyor the shell is robotically lifted from its conveyor fixtures
and placed onto the car frame. Assembly workers, some at
ground level and some in work pits beneath the conveyor, bolt
the car body to the frame. Once the mating takes place theautomobile proceeds down the line to receive final trim
components, battery, tires, anti-freeze, and gasoline.
The vehicle can now be started. From here it is driven to a
checkpoint off the line, where its engine is audited, its lights and
horn checked, its tires balanced, and its charging systemexamined. Any defects discovered at this stage require that the
car be taken to a central repair area, usually located near the
end of the line. A crew of skilled trouble-shooters at this stage
analyze and repair all problems. When the vehicle passes final
audit it is given a price label and driven to a staging lot where it
will await shipment to its destination.
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THANK YOU