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Contents Basics of Quality by Design

Quality Quality Loss Function

Quality and Process Capability Process capability

Basics of Quality by Design Introduction

A large amount engineering manufacture products in conducting in experiments

Quality by design is one of such engineering methodology

Customer’s perception of quality

( Sony television case in Japan and USA )

Basics of Quality by Design

Colour density distribution of Sony America and Japan

(April, 1979)

Basics of Quality by Design

Basics of Quality by Design Taguchi’s definition of quality

“ the quality of a products is the ( minimum ) loss imparted by the product to society from the time the products is shipped “

What is loss – and who pays for it Loss as additional manufacturing cost Loss be paid by society

Basics of Quality by Design Interpretation of loss

Quality loss function (QLF) is quantitative evaluation of quality loss due to functional variation

m = targety = hasil pengukuranΔo = toleransiAo = jumlah kerugian

Basics of Quality by Design

Basics of Quality by Design Interpretation of loss

A quality characteristics is the object of interest of a product or process

Three types quality characteristics• Nominal the best ( NTB )• Smaller the better ( STB )• Larger the better ( LTB )

QLF - Nominal the best ( NTB )( One piece )

• A measurable characteristics with a specific user-defined target value. ( Sony TV : 115 ± 20 volts )

• QLF for NTB

QLF - Nominal the best ( NTB )

QLF - Nominal the best ( NTB )( Many pieces )

QLF – Smaller the better ( STB )( One piece )

QLF - Smaller the better ( STB )( One piece )

Example

QLF - Smaller the better ( STB )( One piece )

QLF - Smaller the better ( STB )( Many pieces )

QLF – Larger the better ( LTB )( One piece )

QLF – Larger the better ( LTB )( One piece )

Example

QLF – Larger the better ( LTB )( Many pieces )

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i iyn

xkyL1

2

11)(

QLF – Asymmetric

Quality and Process Capability Capability process

Quality and Process Capability Capability process

Quality and Process Capability Spec limit : fixed engineering limit for the product

dimmensions Cp index

Cpk index Cpk is an important measure Cpk as a measure of quality

Quality and Process Capability

Quality and Process Capability

Quality and Process Capability Cpk as a measure of quality

The convesional methodsLoss-by-defect = numbers of defect x cost of product

= proportion out of spec x total numbe x cost of product

The quality loss function methods

Loss-by-dispersion = x numbers of product 2220 )( my

A

Quality and Process Capability Cpk as a measure of qualityExample ( Sample 100.000 unit )

Quality and Process Capability Cpk as a measure of quality

Quality and Process Capability Cpk as a measure of quality

Quality and Process Capability Cpk as a measure of quality

Case Study ( Tugas – 2 )A spring is used in the operation of a camera shutter. The manufacturing process

suffers from a degree of variability, in terms of the spring constant (measured in

oz/in), which significantly effects the accuracy of the shutter times. The functional

limits for this spring constant are m±0.3oz/in (m=0.5oz/in), and the average cost for

repairing or replacing a camera with a defective spring is $20.

What is the loss function? Hence, what is the loss associated with producing a spring

of constant 0.25oz/in versus the loss associated with one at 0.435oz/in.

Next Week The Design Process

Principle of robust design in the production process

Robust design process Parameter design