LINE BALANCINGPresented By:Ashita NegiDeepti VermaNancy NegiRohan BharajUchit Arora

Line Balancing Line balancing is the procedure in which tasks along task the assembly line are

assigned to work station so each has approximately same amount of work. A workstation within an assembly line in order to meet the required production

rate and to achieve a minimum amount of idle time.

BALANCED LINE Promotes one piece flow Avoids excessive work load in some

stages (overburden) Minimizes wastes (over-processing,

inventory, waiting, rework, transportation, motion)

Reduces variation Increased Efficiency Minimizes Idle time

UNBALANCED LINE High work load in some stages

(Overburden) Maximizes wastes (over-processing,

inventory, waiting, rework, transportation, motion)

High variation in output Restrict one piece flow Maximizes Idle time Poor efficiency

Important Terminologies TASK PRECEDENCE: The sequence in which tasks are performed. CYCLE TIME: The time expressed in minutes between two simultaneous products

coming off the end of a production line. PRODUCTIVE TIME PER HOUR: The average number of minutes a workstation is

working in an hour. WORKSTATION: A physical area where a worker with tools/ one or more machines,

or an unattended machines like a robot performs a particular set of task in a production line.

WORK CENTER: A small group of identical workstations, where each workstation performs the same set of task.

NUMBER OF WORKSTATIONS WORKING: The amount of work done at a work centre expressed in number of workstations.

MINIMUM NUMBER OF WORKSTATIONS: The least number of workstation that provides the required production.

ACTUAL NUMBER OF WORKSTATIONS: This is the total number of workstations required on the entire production line. It is calculated as the next higher integer of the number of workstations working.

UTILIZATION: The percentage of time a production line is working.

Example of Assembly-Line Balancing

Problem: An Assembly consists of the following elements as given in table below.

The production rate required is one assembly every 15 minute. Determine the minimum no of workstations required so as to minimize the Balance- Delay. Find Balance Delay Station-wise.

STEP 1. List the sequential relationships among tasks and then draw a precedence diagram

Task

A B C D E F G H I J K L

Immediate Predecessor

Nil A B B B B C,D G E I,F H,J K

Task Time 12 6 6 2 2 12 7 5 1 4 6 7

,

.

7 min.

12 min.

12 min

F

6 min

C

6 min

B

2 min

D

P LQ P LQ

P LQ

P LQ

*

(

P LQ

-

/

$

+ 6 min

Incremental Utilisation (IU) Heuristic

A heuristic method is a procedure that can find a good feasible solution for a given class of problems, but which is not necessarily an optimal solution.

❖ It add tasks to a workstation in a precedence task order.❖ To each task added to the station, operators are added when necessary, and the

station utilization is calculated by equation.❖ Tasks are added at the used station until its utilization is 100%, or until a

reduction occurs, considering the new task and another operator when necessary. ❖ Then, a new station is considered, and the procedure is repeated on the next

workstation for the remaining tasks.

The incremental utilization heuristic is appropriate when one or more task times is equal to or greater than the cycle time. An important advantage of this heuristic is that it is capable of solving line-balancing problems regardless of the length of task times relative to the cycle time.

ExampleThe back room operations of a fast food restaurant have these tasks:

If 100 burgers per hour must be prepared by the crew and 50 minutes per hour must be prepared by the crew and 50 minutes per hour are productive:

a.Draw a diagram of the precedence relationships.b. Compute the cycle time per burger in minutes.c. Compute the minimum number of workstations required.d. How would you combine tasks into workstations to minimize idle time?

Use the incremental utilization heuristic. Evaluate your proposal.

Solutiona) Compute the cycle time per burger:

Cycle time = Productive time/ hourDemand/ hour

= 50 minutes/hour100 burgers/ hour

= 0.50 minute/burger

b) Compute the minimum number of workstations:

Minimum no. = Sum of task times x Demand/hourof workstations Productive time/hour

= 5.07 minutes/burger x 100 burgers/hour 50 minutes/hour

= 0.14 workstations

c) Precedence Diagram

d) Evaluation of the proposal:

Utilization= Minimum number of workstationsActual number of workstations

= 10.14 43 = 0.2358 or 23.58 %

Longest-Task-Time Heuristic

STEP 2. . Calculate the required workstation cycle time

CYCLE TIME = (PRODUCTION TIME PER DAY) /(OUTPUT PER DAY) = 15 minutes

STEP 3. Calculate the theoretical minimum number of workstations.

NUMBER OF WORK STATIONS = ( SUM OF TOTAL TASK TIMES) / (CYCLE TIME)

= 70 min’s / 15 min’s

= 4.67 ≈ 5 (rounded)

STEP 4. Choose a primary rule that will determine how tasks are to be assigned to workstations

For this example, our primary rule is to prioritize tasks based on the largest number of following tasks.

If there is a tie, our secondary rule is to prioritize tasks in the order of the longest task time.

In general, select rules that prioritize tasks according to the largest number of followers or based on length of time.

STEP 5. Beginning with the first workstation, assign each task, one at a time, until the sum of the task times is equal to the workstation cycle time or until no other tasks can be assigned due to sequence or time restrictions.

Task

Number of Following Tasks

A 11

B 10

C or D or E 4

I,F or G 3

H or J 2

K 1

L 0

Stations Task Task Time(in minutes)

Number ofFollowing Tasks

RemainingUnassignedTime(Balance-Delay)

FeasibleRemainingTasks

Task withMostFollowers

Task withLongestOperatingTime

Station 1 A 12 11 3 IDLE NoneStation 2 B

CD

662

1044

93

1 IDLE

C,D,ED,E

None

C,D,ED,E

CD ,E

Station 3 EFI

2121

433

131

0 IDLE

F,I, GI

None

F,I,G F

Station 4 GH

75

32

83 IDLE

H, JNone

H, J H

Station 5 JK

46

21

115 IDLE

KNone

   

Station 6 L 7 0 8 IDLE None    

STEP 7. Evaluate the efficiency of the line balance.EFFICIENCY = (SUM OF ALL TASK TIMES)/(ACTUAL NO OF WORKSTATIONS)X(CYCLE TIME) = (70) / (6) X (15) = 0.778 OR 77. 78 %

Cars for the masses

Cost $850

Built new plant at Highland Park, Michigan

Ford consulted Frederick Taylor, Creator of Scientific Management

Installation of Gravity Slides

December 1, 1913, the first large scale assembly line was officially launched

Assembly Line- The Ford Way

Cars 84 Steps in the assembly line

Interchangeable parts

Less waste and higher quality product

Production time dropped from over 12 hours to just 93 mins

Produced 3,08,612 cars in 1914

Cost of Model T dropped to $260 in 1924

Work time was reduced from 9 to 8 hours and wages doubled to $5 a day

Assembly Line- The Ford Way

Apparel Industry

With proper implementation of line balancing it was seen that the efficiency was further increased.

Benefits of Assembly Line Balancing

•Technical Benefits•Economic Benefits

Limitation of Line Balancing

Production lines were designed so that conveyor belts paced the speed of the employees work. This arrangement wasn't appreciated by the employees.

Inevitable changes lead to production lines being out of balance.

Rebalancing causes disruptions to production 

THANK YOU!