assembly line balancing

ASSEMBLY LINE
BALANCING
MODUL 7
What is Line Balancing ??

Assigning each task to a work within an
assembly line in order to meet the required
production rate and to achieve a minimum
amount of idle time.

Line balancing is the procedure in which
tasks along the assembly line are assigned
to work station so each line has
approximately same amount of work.
Terms Defined

Delay/idle time of a workstation: the
difference between the cycle time (CT) and
the station time (ST).

Cycle time (CT): the time between the
completion of 2 successive assemblies,
assumed constant for all assemblies for a
given conveyor speed.
Terms Defined (Cont.)

Line efficiency (LE): the ratio of total station time to the cycle
time multiplied by the number of workstations

Balance Delay


Balance Delay

Work element: a part of the total work content in an assembly
process.
Terms Defined (Cont.)

Smoothness index (SI): an index to indicate
the relative smoothness of a given
assembly line balance. A smoothness index
of zero indicates a perfect balance

Workstation (WS): a location on the
assembly line where a work element or
elements are performed on the product.
Precedence Constraint

Precedence Constraint is a restriction on
the order of execution of work elements.

There are two conditions taht usually
appear in assembling process:
1. There is no dependency of the components
in the works
2. If a component has been selected to be
assembled, then the sequence begins to
assemble other components.
Precedence diagram

Precedence diagram: a diagram that describes the
ordering in which work elements should be

performed. It shows that some jobs cannot be
performed unless their predecessors are
completed. The layout of workstations along the
assembly line depends on the precedence diagram

Presedence diagram symbols:

Symbol element

Relationship between symbols
Precedence Diagram
Zoning Constraint

Allocation of work elements at the work
station is also limited by zoning constraints
that preclude or require grouping of certain
elements of the work on a particular
station.
Line Balancing Methods

Helgeson dan Birnie / Ranked Positional Weight
(RPW)

Kilbridge and Wester Heuristic (Region Approach)

Largest Candidate Rule
Helgeson dan Birnie / Ranked
Positional Weight (RPW)
Step 1- Calculate the weight of the position of each work
elements.

Step 2- Sort the elements according to the weight of the
position of the largest to the smallest.
Step 3 -Calculate the cycle time.

4. Place the working element with the greatest weight on
all the workstations do not violate precedence relationships
and time station does not exceed the cycle time.

5. Repeat step 4 until all the elements are placed.

6. After forming a work station consisting of its elements,
then specify the value of efficient, balance delay, and its
smoothest index.
Kilbridge and Wester Heuristic
(Region Approach)

Create precedence diagram of the problems faced. Separate work elements in
the diagram in columns from right to left.

2. Determine the cycle time (TC) of primes total time working elements, and
specify the number of work stations.

3. Place the work elements to work stations such that the total time working
element does not exceed the cycle time. Remove elements of work that has
been placed on the list of work elements.

4. When an element of work placement resulted in a total time of work elements
exceeds the cycle time working elements are placed in the next work station.

5. Repeat steps 3 and 4 until all work elements are placed.


6. Determine the value of efficient, balance delay, and smoothness index
Largest Candidate Rule

The basic principle is to combine the processes of sorting
operation on the basis of the largest processing time to the
smallest elements of the operating time

Steps:
1. Starting from the top, select the element to be assigned to the
first station, which meets the requirements of precedence and does
not cause the total amount exceeds Tek on stretcher station Ts.
2. If there are no other elements that can be assigned without
exceeding Ts, then move on to the next station.
3. Repeat steps 1 and 2 for the other stations until the completion
of all elements assigned.
4. Determine the value of efficient, balance delay, its smoothness
index.