Operations and Supply Chain Management The Core

MANUFACTURING PROCESSES chapter 6 189
Configuration 3 splits the tasks across three workstations as shown:
CONFIGURATION 3
TASKS
ASSIGNED
STATION WORK
CONTENT (MINUTES)
Station 1 A, B 25
Station 2 C, D 20
Station 3 E 15
CYCLE TIME
(MINUTES)
CAPACITY
(UNITS PER HOUR)
EFFICIENCY
(PERCENT)
25 2.4 80.00
With this configuration it is not possible to perfectly balance the work in each station. Station 1
has the most work and is the bottleneck. This assembly line can produce only one unit every 25
seconds or 2.4 (2.4 = 60/25) units per hour. The efficiency of this line is 80 percent [0.8 = 60/
(3 × 25)].
Configuration 4 splits the tasks across four workstations as shown:
CONFIGURATION 4
TASKS
ASSIGNED
STATION WORK
CONTENT (MINUTES)
Station 1 A 10
Station 2 B, C 20
Station 3 D 15
Station 4 E 15
CYCLE TIME
(MINUTES)
CAPACITY
(UNITS PER HOUR)
EFFICIENCY
(PERCENT)
20 3 75.00
With this configuration, station 2 is the bottleneck and the fastest sustainable cycle time of the
assembly line is 20 minutes per unit. Producing a unit every 20 minutes would allow the assembly
line to produce three (3 = 60/20) units per hour when operating at a steady rate. The efficiency
of this line is 75 percent [0.75 = 60/(4 × 20)].
As the capacity of the line increases by splitting tasks into more stations, the efficiency is
reduced. A key to understanding this analysis is the idea of the process bottleneck. The bottleneck
is the station that has the most work content in the assembly line. When operating at a
steady rate, the assembly line cannot operate faster than the slowest workstation, so this station
limits capacity. The difference between the cycle time of the assembly line and the work content
in each station is idle time. In configuration 3 there would be 10 minutes of idle time in station
1, 5 minutes in station 3, and 5 minutes in station 4 for a total of 20 minutes of idle time for
each unit produced. The efficiency equation captures this idle time; for the 60 minutes of actual
work content to make a unit, 80 minutes is used (20 minutes of this time is the idle time).
DISCUSSION QUESTIONS
LO6–1
LO6–2
LO6–3
1. What is meant by a process? Describe its important features.
2. What is a customer order decoupling point? Why is it important?
3. What’s the relationship between the design of a manufacturing process and the
firm’s strategic competitive dimensions (Chapter 2)?
4. What is meant by manufacturing process flow?
5. Why is it that reducing the number of moves, delays, and storages in a
manufacturing process is a good thing? Can they be completely eliminated?
6. What does the product–process matrix tell us? How should the kitchen of a
Chinese restaurant be structured?
7. It has been noted that during World War II Germany made a critical mistake by
having its formidable Tiger tanks produced by locomotive manufacturers, while the
less formidable U.S. Sherman tank was produced by American car manufacturers.
Use the product–process matrix to explain that mistake and its likely result.