Operations management by stevenson 9th student slides supplement 7

Supplement 7Learning Curves... Supplement 7: Learning Objectives• You should be able to: – Explain the concept of a learning curve – Make time estimates based on learning curves – List a

Supplement 7

Learning Curves

Supplement 7: Learning Objectives

• You should be able to:

– Explain the concept of a learning curve

– Make time estimates based on learning curves

– List and briefly describe some of the main applications

of learning curves

– Outline some of the cautions and criticisms of learning

curves

– Estimate learning rates from data on job times

Learning Curves

• Learning curve

– The time required to perform a task decreases with

increasing repetitions

– The degree of improvement is a function of the task

being done

• Short, routine tasks will show modest improvement

relatively quickly

• Longer, more complex tasks will show improvement

over a longer interval

Learning

The Learning Effect

• The learning effect is attributed to a variety of factors:

– Worker learning

– Preproduction factors

• Tooling and equipment selection

• Product design

• Methods analysis

• Effort expended prior to the start of work

– Changes made after production has begun

• Changes in work methods

• Changes in tooling and equipment – Managerial factors

• Improvements in planning, scheduling, motivation, and control

Interesting Characteristics of Learning

• The learning effect is predictable

– The learning percentage is constant

• Every doubling of repetitions results in a

constant percentage decrease in the time per

repetition

– Typical decreases range from 10 to 20 percent

Learning Curves: On a Log-Log Graph

Learning Illustrated

• Each time cumulative output doubles, the time per unit for that

amount should be approximately equal to the previous time

multiplied by the learning percentage.

• If the first unit of a process took 100 hours and the learning rate is

90%:

Unit Unit Time (hours)

2 90(100) = 90

4 90(90) = 81

8 90(81) = 72.9

16 90(72.9) = 65.61

Unit Times: Formula Approach

percentage rate

learning

2 ln

ln

unit first

for Time

unit

th for

Time

where

1 1













r

r b

T

n T

n T

T

n

b n

Example: Formula Approach

• If the learning rate is 90, and the first unit took

100 hours to complete, how long would it take to complete the 25th unit?

hours 3068

61

25 100

25

100

15200

2 ln

90 ln 25













T

Unit Times: Learning Factor Approach

• The learning factor approach uses a table that

shows two things for selected learning

percentages:

– Unit value for the number of repetitions (unit number)

– Cumulative value, which enables us to compute the

total time required to complete a given number of units.

factor

Unit time

1 

 T

Tn

Learning Factor Table

Learning Curve Applications

• Useful application areas:

– Manpower planning and scheduling

– Negotiated purchasing

– Pricing new products

– Budgeting, purchasing, and inventory planning

– Capacity planning

Operations Strategy

• Learning curves have strategic implications for:

– Market entry when trying to rapidly gain market share

• As volume increases, operations is able to move quickly down the learning curve

– Reduced cost  improved competitive advantage

– Useful for capacity planning

• Can lead to more realistic time estimates, thus leading

to more accurate capacity needs assessment