chapter 5 – part 3

Chapter 5 – Part 3

The TQM Philosophy

Mini Case: Quality Improvement

LSLLSL USLUSL

X = Amount of Toner Toner

Operation: Adding Toner to CartridgeCurrent Process

Target

Mean

20% Defective

Target Toner

What’s wrong with this operation?

How should it be corrected?

Why is this fix feasible?


LSLLSL USLUSL

Amount of Toner

New Process – Mean Shifted to left and centered on target

Target



Benefits?

Next step?

Amount of Toner

Suppose the current process looked like this. Will adjusting the mean to the target improve the process?


LSLLSL USLUSL

Target

20% Defective

Mean

Amount of Toner

Mean adjusted to target


10% Defective

LSLLSL USLUSL

Mean =Target

10% Defective

Seven Tools of Quality Control

Cause-and-Effect Diagrams Flowcharts Checklists Control Charts Scatter Diagrams Pareto Analysis Histograms

Cause-and-Effect Diagram(Fishbone Diagram)

Machines

Cause

Effect-problem

MaterialsMethods

Manpower

Environment

Cause

Cause

CauseCause

CauseCause

Cause

CauseCause

Cause

Cause

4M + E

Flowcharts

Checklist

Simple data check-off sheet designed to identify type of quality problems at each work station; per shift, per machine, per operator

Control Charts (Chapter 6)

Control charts are tools for predicting the future performance of a process.

If we can predicting performance, we can take corrective action before too many nonconforming units are produced.


Suppose we construct a control chart for the thickness of the gold plating of an electrical connector.

We take samples of connectors over time and compute the mean of each sample.

After several time period, we use the sample means to estimate the mean thickness.


We then construct two control limits:

an upper control limit (UCL) and a lower control limit (LCL)

• We do this by adding subtracting 3 standard deviations to the estimated mean:

LCL = Estimated Mean – 3(Standard Deviation)

UCL =Estimated Mean + 3(Standard Deviation)

We plot the estimated mean and the control limits on the control chart.

The result is called a control chart for the process mean.


Time

mean

Mea

n th

ickn

ess


If the sample means fall randomly within the control limits, the process mean is in control.

“In control” means that the process mean is stable and hence predictable.

If at least one sample mean fall outside of the control limits, we say the process mean is “out of control.”

In this case, the process mean is unstable and not predictable.

The goal is to find out why and remove the causes of instability from the process.

Speed vs. Yield

0

5

10

15

20

25

30

0 10 20 30 40

Speed

Yie

ld

Scatter DiagramsA graph that shows how two variables are related to one another

Optimal Speed

Pareto Diagram

Pareto Principle:

80% of the problems may be

attributed to 20% of the

causes.

Pareto Principle:

80% of the problems may be

attributed to 20% of the

causes.

Missing

Per

cen

t of

def

ects

Bubbles CracksUneven

Runs

80%

Histogram for Diameter

0

5

10

15

20

25

30

35

40

45

<=0.077 .077-.277

.277-.477

.477-.677

.677-.877

.877-1.077

1.077-1.277

1.277-1.477

1.477-1.677

1.677-1.877

1.877-2.077

>2.077

Diameter

USLLSL

Histograms

Reliability

Reliability is the probability that the product, service or part will function as expected.

Reliability is a probability function dependent on sub-parts or components.

Reliability

Reliability of a system is the product of component reliabilities:

RS = (R1) (R2) (R3) . . . (Rn)

RS = reliability of the product or system

R1 = reliability of the first component

R2 = reliability of the second component. ..

Rn = reliability of the nth component

Example 1: Components in Series

A radio has three transistors. All transistors must work in order for the radio

to work properly. Probability that the first transistor will work =.80 Probability that the first transistor will work =.90 Probability that the first transistor will work =.85

What is the reliability of the radio?

Solution

RS = (R1) (R2) (R3)

RS = (.80) (.90) (.85) =.51

R1 = .80 R3 = .85R2 = .90

Example 2: Backup Components

Backup component takes over when a component fails.

Suppose only one transistor is needed for the radio to work.

In case the one transistor fails, a backup transistor has been installed.

Probability that the original transistor will work =.92

Probability that the backup transistor will work =.87


The backup transistor is in parallel to the original transistor.

RBU = .87

R1 = .92


Parallel components allow system to operate if one or the other fails

Increase reliability by placing components in parallel For system with one component and a BU

component:

RS = R1 + [(RBU) x (1 - R1)]

1 - R1 = Probability of needing BU component

= Probability that 1st component fails

Solution

RS = R1 + [(RBU) x (1 - R1)]

RS = .92 + [(.87) x (1 - .92)]

= .92 + [(.87) x (.08)]

= .9896

RBU = .87

R1 = .92

R1 = .80

RBU = .75

R2 = .88

Example 3: Series with Backup Components

Example 3: Series with Backup Components

• BU is in parallel to first component.• Convert to system in series.• To this by first finding reliability (probability) of

components.

A = Probability that first component or its BU works

B = Probability that second component works = R2

RS = A x B

Solution

A = R1 + [(RBU) x (1 - R1)]

= .80 + [(.75) x (1 - .80)]

= .95

B = R2 =.88

RS = A x B = .95 x .88 = .836

.95 .88

Part 1 Part 2

Reliability Over Time - Bathtub Curve

t0 Time

Fai

lure

Rat

e

Maturity

Constant Failure

Infant Mortality

t2t1

Quality Awards and Standards

Malcolm Baldrige National Quality

Award (MBNQA)

The Deming Prize

ISO 9000 Certification

MBNQA- What Is It? Award named after the former Secretary of

Commerce – Regan Administration Intended to reward and stimulate quality

initiatives Given to no more that two companies in each

of three categories; manufacturing, service, and small business

Past winners: Motorola Corp., Xerox, FedEx, 3M, IBM, Ritz-

Carlton

Baldrige Criteria

Leadership (125 points)

Strategic Planning (85 points)

Customer and Market Focus (85 points)

Information and Analysis (85 points)

Human Resource Focus (85 points)

Process Management (85 points)

Business Results (450 points)

The Deming Prize

Given by the Union of Japanese Scientists and

Engineers since 1951

Named after W. Edwards Deming who worked to

improve Japanese quality after WW II

Not open to foreign companies until 1984

Florida P & L was first US company winner

Based on how well a company applies Deming’s 14

points

ISO 9000

Set of international standards on quality

management and quality assurance, critical to

international business Data based approach to decision making Supplier relationships Continuous improvement Customer focus Leadership Employee training Process (operations) management

chapter 5 – part 3

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