Chapter 3

Designing Quality into Products and Services

Dr. Ayham Jaaron

Objectives

use the Management Tools to organize and communicate information.

discuss Quality Function Deployment (QFD) and its role in product and service design.

discuss Design for Six Sigma (DSS). discuss Taguchi robustness concepts. calculate reliability for a system. discuss ways in which system reliability can be improved. use the risk assessment tools of Fault Tree Analysis (FTA)

and Failure Mode and Effects Analysis (FMEA).

Designing Quality into Products and Services

Must be designed to satisfy and delight the customer

Design begins with input from the customer

Two approaches: Seven management tools Quality function deployment

Reliability

The Seven Management Tools

• Affinity Diagram• Tree Diagram• Process Decision Program Chart (PDPC)• Matrix Diagram• Interrelationship Digraph• Prioritization Matrix• Activity Network Diagram

Affinity Diagram

Similar to a cause and effect diagram

Organizes ideas and facts into categories

Ideas with affinities for each other are placed in the same category

Affinity Diagram

Affinity Diagram for Roger’s Take-Out Pizza

Product Service Cost Features

Extra Value 30 Min. Max. Wait Lower Price More Topping Variety

Delivered Hot Friendly Drivers No Delivery Charge More Crust Variety

Courteous Order Takers Coupons with Order

Affinity Diagrams help to organize ideas and facts whichhave an affinity for each other into categories. In this example,Lower Price and No Delivery Charge have an affinity andare placed into the Cost category.

Tree Diagram

Partial Tree Diagram for Roger’s Take-Out Pizza

Category Objective Strategy

Extra MeatExtra Value

More Cheese

Product Fresh Vegetables

Heated Compartmentsin Delivery Vans

Delivered HotInsulated Boxes

Optimum Routing30 Min. Max. Wait

Batch Delivery Employee Training

Service Friendly Drivers Driver Rotation

Employee TrainingCourteous Order Takers

Secret Shoppers

Tree Diagrams facilitate planning actions shown on theaffinity diagram.

Process Decision Program Chart (PDPC)

A framework for developing contingency plans

Starts with a tree diagramNegative outcomes are considered

for each branchContingency plans are listed

Process Decision Program Chart

Partial Process Decision Program Chart for Roger’s Take-Out Pizza

Possible ContingencyCategory Objective Strategy Outcomes Plan

30 Min. Max. Wait Computer-Based Continued Training

Employee Training High TurnoverService Friendly Drivers

Driver Rotation Longevity Raises

Courteous Order Takers

Job Enrichment

Matrix Diagram

Graphically depicts relationships between concepts

Shows relationship between desired objectives and possible actions

Strength of relationship is indicated by shading

Matrix Diagram Partial Matrix Program Chart for Roger’s Take-Out Pizza

Improved Improved Improved Improved Action Employee Kitchen Delivery Controls

Objective Training Process Process

30 Min. Max. Wait

Friendly Drivers

Courteous Order Takers

KEY: Strong relationship

Moderate relationship

Weak relationship

Interrelationship Digraph

Depicts causal relationships among the categories in the affinity diagram

Arrows indicate which factors are drivers of other categories

Interrelationship Digraph

Interrelationship Digraph for Roger’s Take-Out Pizza

Service

Product Cost

Features

Prioritization Matrix

Allows the comparison of quantitative and qualitative data in the same analysis

Dimensions are the categories for the affinity diagram

Dimension must be assigned a weightEach company is rated for the dimension

on a scale of 1-10 with 10 being best

Prioritization Matrix

Prioritization Matrix for Roger’s Take-Out Pizza

Category Weight Roger’s

Raw Score

Roger’s

Wtd. Score

X-O’s

Raw Score

X-O’s

Wtd. Score

Difference

Wtd. Score

Product 0.30 7 2.10 8 2.40 +0.30

Service 0.25 6 1.50 7 1.75 +0.25

Cost 0.25 8 2.00 6 1.50 -0.50

Features 0.20 9 1.80 7 1.40 -0.40

TOTAL 1.00 7.40 7.05

Activity Network Diagram

Also known as PERT and CPM Program Evaluation & Review Technique

(PERT) Critical Path Method (CPM)

A project planning and control tool

Activity Network Diagram

Activity Network for Evaluation of Heated Compartments in Delivery VansRoger’s Take-Out Pizza

3 Prepare Order Heaters Install in Prototype Train Design 2 3 Evaluate Prototype Drivers1 2 5 6 7

4 2 4

Order Hi-Capacity 1 1 Install inBattery & Alternator Prototype

4

Quality Function Deployment (QFD)

Developed in Japan by Professor Yoji Akao

Quality is defined by the customerCustomer’s definition of quality is

considered in the product/service design process and production process

Quality Function Deployment (QFD)

West Wing-customer requirementsSecond Floor-translates customer

requirements into design requirementsMain Floor- correlation of design

requirements with customer requirements

Attic-interrelationship of the design requirements (what are the tradeoffs)

Quality Function Deployment (QFD)

Basement-contains target values or specifications for the design requirements

East Wing-comparison of the product or service under design with leading competitors

Applying QFD House of QualityExample….climbing suit

QFD Example

In the following example, the customer requirement ofvalue is operationalized for a pizza in terms of meat, cheese,vegetables, and price. As the quantities of meat and cheeseincrease, customer value strongly increases. As the quantity of vegetables increases, customer value increases.As price increases, customer value decreases.

The House of Quality

Value

Taste

Delivered Hot

1 2 3 4 5

Design Requirements

CustomerRequirements

TargetValues

R = Roger’s PizzaX = Competitor X-OA = Competitor Ace

(5 is best)

Correlations++ Strong Positive+ Positive0 Negative00 Strong Negative

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QFD-Four-phased Approach

Uses a series of stages to translate customer requirements into:

Parts characteristics Key process operations Production equipment settings

QFD-Four-phased Approach

Figure 3.9. Four-Phase QFD Model

Design for Six Sigma (DFSS)

Developed at General Electric in 1997An extension of the standard Six Sigma

MethodologyProactive SIX SIGMA goal is 3.4 defects per million

opportunity (DPMO)No standard approach5-interconnected phases

Define, measure, analyze, design, & verify

Taguchi Robustness Concept

Advocated designing robustness into products and systems

Robustness: the condition of product/process design that remains relatively stable

Three steps System design Parameter design Tolerance design

Results in more reliable products than can be produced economically.

Reliability

Key part of design processDefinition: The probability the product or

service will perform without failure for a specified period of time.

3 dimensions of reliability Probability

Will perform on a given trial (successful trials)Will last for a given length of time

Definition of failure Prescribed operating conditions

Reliability Life Characteristic Concepts

Failure rate is the number of failures per unit of time

Graphically depicted failure is usually the bathtub curve Early stage failure

Occurs early in the product/services lifeThese are usually the result of design,

manufacturing or use error.

Reliability Life Characteristic Concepts

Expected Normal Life A pattern of constant and relatively low failure

rates Usually result of design limitations, changes in

the environment and damage from day-to-day use or maintenance

End-of-Life Failure Product exceeds the intended life expectancy Usually results from daily wear and stress

Bathtub curve

Mean Time Between Failures

The average time between failuresCan be modeled by a negative

exponential distributionExponential distribution can determine:

Probability of failure before a certain time Probability of a product lasting at least

until a certain time

Mean Time Between Failures

To determine the probability that failure will not occur before a certain time:

P(no failure before T) = e -T/MTBF

Where:e = natural logarithm, 2.7183….  

T = time in service before failure  MTBF = mean time between failures  

Risk Assessment Tools and Risk Prevention

Failure Mode and Effects Analysis Used to examine a product at the

system or subsystem levels Can be expanded to include:

SafetyEffect on downtimeAccessRepair planningDesign changes

FMEA Worksheet

Risk Assessment Tools and Risk Prevention

Faulty Tree Analysis A tool used to identify possible causes

for potential operating hazards or undesired events.

Can you suggest some examples?

Error Proofing

Japanese call it poka-yokeCan be incorporated into services

(e.g. failure to proceed in filling partial applications).

Class work (7 minutes)

In groups of 5 students, can you think of other three poke-yoke measures that can be used in products/services?

Share these with your colleagues.

Examples:

File cabinets.Electric socketsCars electronic door lock; won’t

operate if door is open.Anti-Braking System.Lawn mowers.Washing machine won’t work if door is

open to prevent injury.

Summary

Quality has to be incorporated into the design

First step is to focus on the customerSeven Management Tools and

Quality Deployment Function are tools to help incorporate customer input into the design process

Summary

Design for Six Sigma builds on traditional Six Sigma methodology

Robustness and reliability are related concepts

Reliability can be improved by: Increasing reliability of individual

components Building redundancy into the system

Summary

Tools can address potential failure modes for products and services Failure Mode and Effects Analysis Faulty Tree Analysis