Chapter 5, Part 1 The TQM Philosophy. What is Quality? What do we mean by quality? Newer, more...

Chapter 5, Part 1

The TQM Philosophy

What is Quality?

What do we mean by quality?

Newer, more widely accepted definition of quality is the ability of a product or service to consistently meet or exceed the customer’s expectations.

This definition of quality is “customer driven.”

What is Quality?

Customer driven quality starts with having the customer determine the characteristics of a product or service that are important to them.

What are important characteristics of a

Cake?

What is Quality?

Technical support?

TV set?

Laptop?

What is Quality? These characteristics are called quality

characteristics.

To insure that they are set at the right levels, we need to quantify them.

We quantify them by having the customer impose acceptable numerical ranges or limits on their values:

What is Quality?

How sweet should a cake be?

It should have between ¼ and ¾ cup of sugar.

How moist can it be?

Moisture content can be between 13 and 15 grams.

The diameter of a steering wheel can be between 1.5 and 2.5 inches.

The weight of a laptop should be between 3.5 and 4.5 lbs.

What is Quality?

The limits on the product’s quality characteristics are called the product’s specification limits, or “specs.”

Some quality authorities define quality as producing units of a product that fall anywhere within the product’s spec limits. These units are called conforming (to specs) or

non-defective units.

Units that fall outside the specs limits are called nonconforming or defective units.

What is Quality?

Thus, according to these authorities, quality is the ability of a product to meet the spec limits.

Other authorities disagree and have a different definition of quality.

Later.

Evolution of Defect Prevention

Mass or 100%Inspection

Prevent defectsbefore production

Proactive-Fix the process

Proactive-Design quality into

product

StatisticalProcesscontrol

Reactive-Fix the Product

Prevent defects from being shipped

Prevent defectsfrom being produced

Design of Experiments

Evolution of Quality Organizations

Quality Dept.

Action Plan for TQM

Quality at the

Source

TQM

No ownershipof quality outside

Quality Dept.

Quality is responsibly of the Quality Dept.

Quality is everyone’sresponsibility

Six SigmaMotorola,TI, GE

Philosophy of making each

worker responsible forhis or her own work.

Quality at the

Source

Features of TQM – Table 5-3

Customer focus Quality is customer driven

Continuous improvement Philosophy of never-ending improvement

Employee empowerment Empower employees to find and solve quality problems

Use of quality tools Basic 7 – more later

Product design Design products to meet customer expectations

Process management Fix the process, not the product

Managing supplier quality Work with suppliers to insure that they processes are capable of shipping parts that meet your requirements.

Features of TQM – Table 5-3

Old vs. New Views on Quality

Old New

Quality costs too much Quality pays in form of lower cost:

Higher quality Fewer defective units

Less rework Less Scrap Lower cost

Higher profit


Old New

Quality slows down production and therefore decreases productivity

Higher quality, Fewer defective units, Don’t have to use same inputs twice to make a good unit of product Greater productivity

Higher quality increasesproductivity


Old New

Quality is achieved through mass inspection (100% inspection)

Short term contracts with suppliers

Buy materials/parts from lowest bidder

Quality is achievedby preventing defects, not

detecting them. “Can’tinspect quality into a product.”

Develop LT partnerships

Buy based on quality, Not price


Old New

Have lots of inventory “Just in Case”

Have lots of suppliers for each part– insurance policy

Quality is production's or the quality department’s responsibility

Minimize inventory-Just-in-Time (JIT)

Quality is everyone’s Responsibility - TQM

Have one LT partnersupplier for each part


Old New

Quality is achieved by operating within specs --conformance to specs (Zero Defects (ZD) policy of Phil Crosby)

Quality is achieved by operating on target--Taguchi. ZD is “goal post” thinking.

Specification Limits

Products can have Upper and lower spec limits Lower only – more later! Upper only– more later!

LSL = Lower Specification Limit USL = Upper Specification Limit

QC=Tread depth, inches

Goodunits

Defectiveunits

Defectiveunits

USL=.45LSL=.35

Zero Defects – Goal Post Thinking

Taguchi – Operate on Target

• Being on target is more important than being within the spec limits.

• Target value is the value of the quality characteristic, X, of a product or service that maximizes customer satisfaction.

• Any deviation from the target value imposes an economic loss on the customer, even if all product is within spec!

Taguchi – Operate on Target

Losses increase with increasing deviations from target.

Thus, Taguchi’s definition of quality is defined in terms of the losses imposed on the customer.

The smaller the loss, the greater the quality. Zero losses occur when product or service is

provided ???

LSLLSL USLUSL

Amount of Toner

Target

Output That Is Always On Target

X

Variability = 0Loss = 0

Units produced

LSLLSL USLUSL

Amount of TonerTarget

Process That is Consistently On Target

LSLLSL USLUSL

Amount of Toner

Target

Process That is Haphazardly On Target

LSLLSL USLUSL

Amount of TonerTarget

Process That is Consistently Off Target

Target vs. Variability

Variability On Target Off-Target

High

Low

Haphazardly on target

Consistently on target

Consistently off target

Haphazardly offtarget

Robust quality .

Question

Is it better to have a process haphazardly on target, or a process that if consistently off target?

Before you answer, look at figure on next slide.

Who Would You Prefer to Go Hunting With?

Jane Sam

Target

$

0LSL USL

constant a where,)( 2 kTxkL

X

Loss Function – Process on Target

Target

$

0LSL USL

2)( TxkL

X


k =2k =8

X = quality characteristic

T = Target value

a = customer’s tolerance = half width of spec limits

a = (USL – LSL)/2

LSL = lower specification limit = T - a

USL = upper specification limit = T + a

R = cost of repairing a unit that is at specification limits(given)

How Do We Compute k?

T=target

$

0 X

R

T - a

Loss

T + a


What is the loss when x = T + a?

How Do We Compute k?

aTx

TxkL

2)(

2)( TaTkR

2akR 2a

Rk

Affect of k on the Loss Function

As R, cost of repair, increases, it becomes more costly to repair units prior to shipping. This will increase k. Increases in k increase the losses due to

deviations from target.

Affect of k on the Loss Function

As a increases, k decreases, and so do the losses at all values of X. An increase in a means that the customer’s

tolerances are wider, meaning that the acceptable range of product performance has increased.

The wider the range of acceptable performance, the lower the losses due to deviations from target.

Given

T =10,

a = 3,

R = $20,

what is the loss function?

Example

2.2

3

20$2

2

a

Rk

2102.2 xLoss

Solution

T=10

$

0 X

R= 20

7 13

Graphical Display of Solution

2102.2 xLoss

Computing the Losses

x

0 $220

5 $55

10 0

15 $55

20 $220

2102.2 xLoss

Target0

Goodunits

Defectiveunits

Defectiveunits

USLLSL

Find the Loss Function for the Zero Defects Model

Solution

limits spec theoutside is X if Constant,

spec within is X if ,0

Loss

Loss

Target= Mean

Expected Loss-Process on Target

$

0X

Process Distribution

Loss

Expected Loss – Process on Target

kLossE )(

E(Loss) = Sum of ($Loss x Probability of Loss)

σ2 = Variance of X


1. If the variance = 10.2, the repair cost = $32, and a = 4, what is the expected loss?

k = R/a2 = 32/42 = 2

E(Loss) = kσ 2 =2(10.2) = 20.4

2. Explain meaning.

The company can expect to impose on the customera loss of $20.40 per unit shipped.

Target= Mean

$

0


Process on Target, Little Variation,Small Expected Loss

Target= Mean

$

0


Process on Target, High Variation,High Expected Loss

Taguchi’s Quality Characteristics

Bigger is better Target value =?

Smaller is better Target value=?

Nominal is best (NIB) Target=(LSL+USL)/2

$0

$200

$400

$600

1 2 3 4

X

Loss

$0

$200

$400

$600

1 2 3 4

X

Loss

$0

$200

$400

$600

1 2 3 4 5

X

Loss

Provide an Example of Each

Bigger-is-better

Smaller-is-better

Nominal-is-best

Repair or Ship?

It may be more better for a company to ship some off target units without repairing them to target, depending on how far off target they are.

For other off target units, it may be better to repair them prior to shipping.

T=target

$

0

Ship as is

R

T - a

L

T + a

RepairRepair

Taguchi’s “Repair or Ship” Rule

T=target

$

0

Ship as is

R

T - a

Loss

T + a

RepairRepair


Fraction defective

Fraction defective


Explain the logic supporting the decision to ship units “as is.”

Explain the logic supporting the decision to repair units prior to shipping.


What does rule assume?

If a company is using Taguchi’s rule, when can it stop doing ?????

Chapter 5, Part 1 The TQM Philosophy. What is Quality? What do we mean by quality? Newer, more...

Documents

Transcript of Chapter 5, Part 1 The TQM Philosophy. What is Quality? What do we mean by quality? Newer, more...