OPSM 301 Operations Management

Class 21:

Quality

Koç University

Zeynep Aksinzaksin@ku.edu.tr

Variability = Actual - Expected

Customer Needs - Product Design

Product Design - Process Capability

Process Capability - Process Performance

Process Performance - Product Performance

Product Performance - Customer Perception

Ways in Which Quality Can Improve Profitability

Sales Gains– Improved response– Higher prices– Improved reputation

Reduced Costs– Increased productivity– Lower rework and

scrap costs– Lower warranty costs

Increased Profits

Improved Quality

Quality Costs

Cost of Control (Quality, Conformance)– Prevention costs: reducing the potential for

defects– Appraisal costs: evaluating products

Cost of Failure of Control (Unquality, non-conformance)– Internal failure costs:of producing defective

parts or service– External failure costs: occur after delivery

Early Defect Detection Saves

Prevention Saves Even More!

Stage: At Source Next Process End of Line Final Inspection End User

Cost:

Impact: • Little • Minor • Rework • Much rework • Warranty delay • Reschedule • Delivery delay • Complaints

• Inspect more • Reputation• Market share

International Quality Standards

ISO 9000 series Common quality standards for products sold

in Europe (even if made in U.S.)

2000 update places greater emphasis on leadership and customer satisfaction

ISO 14000 series Environmental management

Auditing

Performance evaluation

Labeling

Life cycle assessment

TQM: Continuous Process Improvement

Measurement– External and Internal

Analysis– Analyze Variation

Control– Adjust Process

Improvement– Reduce Variation

Innovation– Redesign Product/Process

D

AC

P

D

AC

P

Control

Improve

Innovate

Improve

Analytical Tools for Continuous Improvement

Process Analysis Pareto Charts Histograms Scatter Diagrams Fish-Bone Charts Control Charts

Seven Tools for TQM

Check Sheet

Type of Defect Number of Defective Flow Units

Cost

Response Time

Customization

Service Quality

Garage Quality

Pareto Analysis

The purpose of Pareto Analysis is to identify and highlight major symptoms of major quality problems

It is based on the premise that usually a small number of faults cause the majority of malfunctions (to separate the vital few and trivial many)

Developing Pareto Analysis

Define classification of defects to be monitored

Define the period of time over which the assessment will be made

Total the frequency of occurrence of each class of defects over the period

Plot the histogram and cumulative distribution of the classes in descending order of the frequency occurrence

Identify the classes that constitute the majority of

defect occurrences

Pareto Analysis

Frequency Percentage

-100%

-0%

-50%

A B C D E F

Pareto Law (80/20 Rule):

“80 percent of the problems are due to 20 percent of the causes”

Fish-Bone Diagram

Also known as cause-and-effect diagram, or Ishikawa diagram

Pareto analysis is used to identify key problems or symptoms,

Fish-Bone diagram is used to sort causes of the problems

Brain storming sessions of groups of workers needed

It is a very valuable educational tool

Used to find problem sources/solutions Other names

– Fish-bone diagram, Ishikawa diagram

Steps– Identify problem to correct– Draw main causes for problem as ‘bones’– Ask ‘What could have caused problems in

these areas?’ Repeat for each sub-area.

Fish-Bone Diagram

Cause-and-Effect Diagrams

MaterialMaterial(ball)(ball)

MethodMethod(shooting process)(shooting process)

MachineMachine(hoop &(hoop &

backboard)backboard)

ManpowerManpower(shooter)(shooter)

Missed Missed free-throwsfree-throws

Rim alignmentRim alignment

Rim sizeRim size

Backboard Backboard stabilitystability

Rim heightRim height

Follow-throughFollow-through

Hand positionHand position

Aiming pointAiming point

Bend kneesBend knees

BalanceBalance

Size of ballSize of ball

LopsidednessLopsidedness

Grain/Feel Grain/Feel (grip)(grip)

Air pressureAir pressure

TrainingTraining

ConditioningConditioning MotivationMotivation

ConcentrationConcentration

ConsistencyConsistency

Weight data for 20 days-Table 1

Time 1 2 3 4 5 6 7 8 9 10

9:00 81 82 80 74 75 81 83 86 88 82

11:00 73 87 83 81 86 86 82 83 79 84

13:00 85 88 76 91 82 83 76 82 86 89

15:00 90 78 84 75 84 88 77 79 84 84

17:00 80 84 82 83 75 81 78 85 85 80

Time 11 12 13 14 15 16 17 18 19 20

9:00 86 86 88 72 84 76 74 85 82 89

11:00 84 83 79 86 85 82 86 85 84 80

13:00 81 78 83 80 81 83 83 82 83 90

15:00 81 80 83 79 88 84 89 77 92 83

17:00 87 83 82 87 81 79 83 77 84 77

Histogram

0

2

4

6

8

10

12

14

72 74 76 78 8 0 82 84 86 88 9 0 92

Weight (kg)

Fre

qu

ency

Announcement

Last 2 assignments announced on web page

Based on the Toyota case See Web page to download a copy First one due in one week