1. Line Balancing Problem
3.4 mins B
2.2 mins E
2.7 mins A C
4.1mins D
1.7mins F
3.3 mins G
2.6 mins

2. Questions? 1. What is the bottleneck?
2. What is maximum production per hour? 60/4.1=14.63 units
3. What is efficiency and balance delay?
4. How to minimize work stations?
5. How should they be grouped?
6. New efficiency?
4.1 minutes

3. Calculate efficiency A. 73.2% B. 56.7% C. 69.7% D. 79.6% E. 81.2%
3.4 mins B
2.2 mins E
2.7 mins A C
4.1mins D
1.7mins F
3.3 mins G
2.6 mins

4. ( )
4.1x7 20
28.7
69.7%
1-69.7%=30.3% Balance Delay

5. Number of Work Stations
(bottleneck) 20
4.1
= 4.88 work stations

6. Line Balancing Solution
4 Stations
20/24=83.3%
Line Balancing Solution
(5.6)
Max prod./hour
60/6
10 units/hour
3.4
Station 3 B
Station 1 E
2.7
2.2 A C
4.1
(6.0)
Station 2
Station 4
(5.8) D
1.7 F
3.3 G
2.6
All under 6 minutes?

7. Line Balancing Problem
5 Stations
Line Balancing Problem
3.4 mins
20/5.6x5 = 20/28 = 71.4%
5.6 B
2.2 mins E
2.7 mins A C
4.1mins
Max Prod./hour
60/5.6
10.7 units/hour D
1.7mins F
3.3 mins G
2.6 mins
5.0

8. Scheduling High-Volume- Low-Variety Operations
The mass consumption patterns of modern industrialized nations depend on assembly line technology.
The classic example is Henry Ford’s auto chassis line.
Before the “moving assembly line” was introduced in 1913, each chassis was assembled by one worker and required 12.5 hours.
Once the new technology was installed, this time was reduced to 93 minutes.
Favorable Conditions
Volume adequate for reasonable equipment utilization.
Reasonably stable product demand.
Product standardization
Part interchange-ability.
Continuous supply of material
Not all of the above must be met in every case.
Assembly Line Balancing (Henry C. Co)

9. Concepts (1/2) Minimum rational work element
Smallest feasible division of work.
Flow time = time to complete all stations
Cycle time
Maximum time spent at any one workstation.
Largest workstation time.
How often a product is completed.
Inverse of the desired hourly output rate = the amount of time available at each work station to complete all assigned work.
Assembly Line Balancing (Henry C. Co)

10. Concepts (2/2)
Total work content: Sum of the task times for all the assembly tasks for the product.
Precedence diagram: network showing order of tasks and restrictions on their performance
Measure of efficiency
Assembly Line Balancing (Henry C. Co)

11. The Problem
Assign tasks to work stations observing balancing restrictions so as to minimize balance delay while keeping station work content for every station cycle time.
Restrictions:
Technological: precedence requirement.
Position restrictions.
Assembly Line Balancing (Henry C. Co)

12. Finding a Solution
Heuristic procedures generally allow for a broader problem definition, but do not guarantee optimal solution.
Optimizing procedures generally have used more narrowly defined problems, but guarantee optimal solution.
Examples of optimizing procedures
Dynamic programming
0-1 Integer programming
Branch and bound techniques.
Trend in research has been toward optimizing procedures due to availability of large-scale computers.
Assembly Line Balancing (Henry C. Co)

13. A Simple Algorithm
Identify tasks whose predecessors have been assigned to a workstation (available tasks).
Determine from available tasks, those that fit, i.e., those whose tasks times time remaining to be filled at this work station.
Choose a task that fits by some decision rule
task with largest time
task with most successors
task with greatest sum of task times of its predecessors.
Continue steps 1 to 3 until no task fits, then go on to next workstation.
Continue steps 1 to 4 until all tasks are assigned.
Assembly Line Balancing (Henry C. Co)

14. Illustrative Example 1/3
You’ve just been assigned the job a setting up an electric fan assembly line with the following tasks:
Assembly Line Balancing (Henry C. Co)

15. Illustrative Example 2/3
Assembly Line Balancing (Henry C. Co)

16. Illustrative Example 3/3
Assembly Line Balancing (Henry C. Co)

17. Complications Behavioral options Time to move an item between stations
Job enlargement and rotation.
Wages related to task.
Distribution of slack time.
Inventory buffers.
Involving work group in decisions.
Arranging stations to facilitate interaction.
Personnel selection.
Time to move an item between stations
Machine-dominated work stations.
Task times which exceed the cycle time.
Stochastic task times.
Mixed model assembly lines.
Assembly Line Balancing (Henry C. Co)

18. What is the minimum # of work stations?
Round down.
40 secs
59 secs
34 secs
84 secs 3 2 4 5 6
56 secs
45 secs

19. = 318
318/84 = 3.78 or 3 work stations
What is the efficiency with 6 operators?
318/6 x 84=
318/504 =
63%

20. 99 secs
3 Stations ?
40 secs
118 secs
59 secs
34 secs
84 secs
318/3x118
318/354 = 89.8%
56 secs
45 secs
101 secs

21. 99 secs
4 Stations?
40 secs
84 secs
79 secs
59 secs
34 secs
84 secs
56 secs
318/4 x 99 =
318/396 = 80.3%
45 secs
56 secs