KESEIMBANGAN LINI PRODUKSI
(PRODUCTION LINE BALANCING)
(Bagian 1)
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Assembly Systems and
Line Balancing
 Assembly involves the joining together of two or more
separate parts to form a new entity, called a
subassembly, an assembly or some similar name.
 Three major categories of processes used to
accomplish the assembly of the components:
1. Mechanical fastening
2. Joining methods
3. Adhesive bounding
1. Mechanical fastening: A mechanical action to hold
the components together.Includes:
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 Threaded fasteners: Screw, nuts, bolts, etc. Very
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common in industry. Allow to be taken apart if
necessary.
Rivets, crimping, and other methods: he fastener or
one of the components is mechanically deformed.
Press fits: The two parts are joined together by
pressing one into the other. Once fitted, the parts are
not easily separated.
Snap fits: One or both of the parts elastically deform
when pressed together. Commercial hardware such
as retainers, C-rings, and snap rings may be used.
Sewing and stitching: Used to assemble soft, thin
materials such as fabrics, cloth, leather, etc.
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2. Joining methods: Includes welding, brazing, and
soldering. Molten metal is used to join two or more
components together.
Common feature of welding techniques is that fusing
and melting occur in the metal parts being joined.
In brazing and soldering, only the filler metal becomes
molten for joining. The metal components do not melt.
Not as strong as welding.
3. Adhesive bonding: Involves the use of an adhesive
material to join components. Two types of adhesives:
thermoplastic and thermosetting. Thermosetting
adhesives are more complicated to apply, but are
stronger and capable of withstanding in high
temperature.
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Assembly Systems
The methods used to accomplish assembly processes:
1. Manual single-station assembly: Generally used
on a product that is complex and produced in small
quantities. One or more workers are required
depending on the size of the product. Ex: machine
tools, industrial equipment, aircraft, ships, etc.
2. Manual assembly line: Consist of multiple
workstations. One or more workers perform a
portion of the total assembly work on the product.
3. Automated assembly system: Uses automated
methods at the workstations rather than human
beings.
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Manual Assembly Lines
 Used in high-production situations where the work can be
divided into small tasks (work elements) and the tasks
assigned to the workstations on the line.
 By giving each worker a limited set of tasks repeatedly, the
worker becomes a specialist in those tasks and perform
more quickly.
Transfer of Work Between Workstations
1. Nonmechanical Lines: Parts are passed from station to
station by hand. Problems are:
 Starving at stations
 Blocking of stations
As a result, cycle times vary. Buffer stocks are used to
overcome.
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2. Moving Conveyor Lines: Use a moving conveyor
(ex. A moving belt, conveyor, etc.) to move the
subassemblies between workstations. The system
can be continuous, intermittent (synchronous), or
asynchronous.
Problems of continuously moving conveyor:
 Starving
 Producing incomplete items
In the moving conveyor line, production rate may be
controlled by means of feed rate.
f p = feed rate
Vc = conveyor speed (feet per minute or meters per
second)
Vc
S p = spacing between parts
fp 
Sp
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Raw workparts are launched onto the line at regular
intervals.
The operator has a certain time period during which
he/she must begin work before the part flows past the
station. This time period is called the tolerance time.
Tt = tolerance time
L
Tt  s
Ls = length of the station
Vc
Model Variations
It is highly desirable to assign appropriate amount of work
to the stations to equalize the process or assembly times
at the workstations.
This brings the line balancing problem and the three
different types of lines.
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1. Single Model Line: Specialized line dedicated to
the production of a single product.
2. Batch-model Line: Used for the production of two
or more models with similar sequence of
processing or assembly operations.
3. Mixed-model Line: Several models are intermixed
on the line and are processed simultaneously.
These cases may be applied to both manual flow lines
and automated flow lines.
Type 2 and 3 are easier to apply to manual flow-lines.
The problem of line balancing becomes more
complicated when going from type 1 to type 3.
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The Line Balancing Problem
It is to arrange the individual processing and assembly tasks
at the workstations so that the total time required at each
station is approximately the same.
Very difficult to achieve perfect balance in most practical
situations.
If workstation times are unequal, the slowest station
determines the overall production rate of the line.
TERMINOLOGY
Minimum Rational Work Element. The smallest practical
indivisible tasks into which the job can be divided.
Tt = Time required to carry out this rational work element.
Considered to be constant. In fact it varies in a manual
station.
Assumed that they are additive. In fact it changes when two
are combined at one station
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Assembly Line Balancing
The General Procedure
1. Determine cycle time by taking the demand
(or production rate) per day
and dividing
it into the productive time available per day
2. Calculate the theoretical minimum number of
work stations by dividing total task time by
cycle time
3. Perform the line balance and assign specific
assembly tasks to each work station
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Product-Oriented Floor Plan
Work
1
Station
Work Station
3
4
Work
Station
5
2
Belt Conveyor
Office
Note: 5 tasks or operations; 3 work stations
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Total Work Content. (Twc ) Sum of the time of all the
work elements to be done on the line.
ne
Twc   Tej
j 1
ne = Number of work elements that make up the total work
or job.
Workstation Process Time. ( Tsi ) The sum of the times of
the work elements
done
at the station.
n
n
 Tsi
i 1
  Tej
e
j 1
n= number of stations
Cycle Time. ( Tc ) Ideal or theoretical cycle time of the
flow line. The time interval between parts coming off
the line.
E
Tc 
Rp
Tc  max Tsi
Tc  Tej
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Precedence Constraints. (Technological sequencing requirements)
The precedence requirements that restrict the sequence in which the
job can be accomplished. There are also other constraints which
concern the restrictions on the arrangement of the stations.
Position constraint. When the product is too large for one worker
to perform work on both sides, operators are located on both sides
of the flow line.
Zoning constraint. May be either positive or negative. According to
positive zoning constraint, certain work elements should be placed
near each other. A negative zoning constraint indicates that work
elements should not be located in close proximity since they might
interfere with one another.
Precedence Diagram. Graphical representation of the sequence of
work elements. Nodes may be used to symbolize the work
elements, and arrows connecting the nodes for the order.
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Balance Delay. (balancing loss) (d) Measure of the
line inefficiency.
d
nTc  Twc
nTc
The balance delay d will be zero for any values n and
Tc that satisfies the relationship nTc  Twc
Minimum number of workstations required to
optimize the balance delay for a specified Tc may
be found by
minimum n is the smallest integer 
Twc
Tc
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Referensi
 IE462 Introduction to Manufacturing Systems
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