Line Balancing is concerned with production
line may be Assembly/ Fabrication.
It is related with mass manufacturing system
which are based upon line/Product layout
concept (PLO).
Line Balancing is a complex phenomenon
which is associated with assembly
/fabrication line, design on the basis of
product layout or line layout.
Line Balancing process is nothing but a
rationalization process or normalisation
process which is mainly concerned with
unequal production rate at various
successive work station along a production
line (assembly/fabrication).
So the line balancing deal with differential
production rates and hence unequal
operating time at sucessive work station
incase of unbalance production line.
The main aim of line balancing is to attain
(achieve) nearly equal or uniform operating
rate amongst various successive work
station and hence to balance them in term of
operating time.
To minimize facility idealness and hence
waiting factors owing to non-available of
physical facility.
To ensure desired overall production rate.
Unequal production rate and time.
Machine failure.
Due to failure of material handling system.
Human factor (efficiency).
Human
Erractic supply of Material (Not smooth &
not timely)
Due to high logistic down time.
It provide a step by step to solve a Line Balancing
problem. Main Steps are :-
1. List down all the operations to be performed in a
particular sequence.
2. To combine a few operations if possible and then
balance them in term of operating time/ rates.
3. To get a feedback information from the operator
working on production line regarding operating time if
needed.
4. Improve all the operation where modification are
possible.
5. To provide extra machines/ extra material as and when
needed.
There are four steps in solving line balancing described by G.
Andrew (2006).
Main Steps are :-
1. Drawing Precedence Diagram: Precedence diagram needs to
be drawn to demonstrate a relationship between
workstations. Certain process begins when previous
process was done.
2. Determining Cycle Time: Cycle time is longest time allowed
at each station. This can be expressed by this formula:
This means the products needs to leave the workstations
before it reaches its cycle time.
3. Assigning tasks to workstation: The tasks distributions
should be taken after completing a time cycle. It’s good to
allocate tasks to workstation in the order of longest task times.
4. Calculating an Efficiency Line: This is done to find
effectiveness of the line. The formula is given by:
Tasks- Elements of work. Grasp pencil, position pencil on paper
to write, and write the number 4 is an example of a task.
Task precedence- The sequence or order in which tasks must
be performed. Precedence for each task is known from a listing
of the tasks that must immediately precede it.
Task times- The amount of time required for a well-trained
worker or unattended machine to perform a task. Task times
are usually expressed in minutes.
Cycle time- The time in minutes between products coming off
the end of a production line.
Cycle Time = Productive Time per hour / Demand per hour
Productive time per hour- The number of minutes in each hour
that a workstation is working on the average. A workstation
may not be working because of such things as lunch, personal
time, breakdowns, start-ups, and shutdowns.
Work station- Physical location where a particular set of tasks
is performed. Workstations are usually of two types: a manned
workstation containing one worker who operates machines
and/or tools, and an unmanned workstation containing
unattended machines like robots.
Work center- A physical location where two or more identical
workstations are located. If more than one workstation is
required to provide enough production capacity, they are
combined to form a work center.
Number of workstations working- The amount of work to be
done at a work center expressed in number of workstations.
Twenty-eight hours of work at a work center during an 8-hour
shift would be equivalent to 28/8, or 3.5, workstations working.
Minimum number of workstations- The least number of
workstations that can provide the required production,
calculated by:
Minimum Number of Work stations
= Sum of all task times / Cycle Time
= (Sum of all task times X Demand per hour ) /
Productive time per hour
Actual number of workstations- The total number of
workstations required on the entire production line, calculated
as the next higher integer value of the number of workstations
working.
Utilization- The percentage of time that a production line is
working. This is usually calculated by:
Utilization
= (Minimum number of workstations / Actual number
of work stations )
In practical situations perfect line balancing (100%)
is hardly achieved, some times 100% line balancing
is not even desirable in case of mass manufacturing
system (MMS) there might be some delays and
failures so we have to provide some time relief
(lead/lag) for these unavoidable factors such as delay
in supply of raw material, failure of material handling
system, failure of machine tools and some time
failure of power system.
The principle of work division when applied to mass
manufacturing system (assembly/Fabrication line)
acquires the form of a production line.
In such cases A/F the total quantum (work) is divided
into various individual tasks and then assign to
sucessive work station which are arranged
sequentially into a production line.
As the product moves down the line. Each operator
acts to it his share of work. This process of
apportioning (equal distribution) the
assembly/fabrication work among the line workers is
known as assembly/fabrication line balancing.
In industries which are going in for mass manufacturing based
upon line layout concept, we generally encounters (face) with
two types of line balancing problems which are as:-
1 Assembly Line Balancing
2 Fabrication Line Balancing
Assembly Line Balancing:- It is a practically problem which is
mainly concerned with assembly work in case of unbalanced
production line. The term assembly line has gain acertain
popular interpretation as it is generally used with reference to
automotive automobile industry. But here in our discussion it is
used to indicate a production line which is comprising of purely
assembly operation to be performed at sucessive work station.
The assembly operation under consideration must involve the
arrival of individual component parts at a particular work place
and departure of these parts which are assembled together in
form of subassembly or final assembly.
Fabrication Line Balancing:- On the other hand fabrication line
balancing is primary concerned with fabrication work in case of
unbalanced production line therefore main distinction between
these two can be made on the basis of type of operation ( work
element) which are taking place across the production line to
be balanced. Fabrication line mainly comprises of such
operations that change the physical and some times the
chemical property of the product involve. Such fabrication
operation are mainly machining, welding, forming , heat
treatment process etc.
So fabrication line balancing is nothing but simply the process
of normalasing the differential ( unequal) production rate
among the sucessive work stations of a fabrication line.
1. It is by varying machine speed (Operating Rates-r)
2. By employing extra machine on those work station having
low production rate.
3. By employing extra materials (Where production rate are high)
4. By adjusting human factors which is most flexible element
of a production system and hence man’s time can be
adjusted easily amongst sucessive work station across a
production line.
5. By improving operations at some work stations.
6. By improving the machine utilization factor for some work
station in a production line.
7. By improving the existing layout design with the help of
visual aids.
8. By having efficient and effective material handling system in
order to minimize time delays and hence unproductive time.
9. By improving (using) tools, jig, fixture.
