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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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