Ch5 Methods and Philosophy of Statistical Process Control

Ch5 Methods and Philosophy of
Statistical Process Control
Chapter 5
Learning Objectives
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Introduction to Statistical Quality Control, 6th Edition by Douglas C. Montgomery.Chapter 5
Copyright (c) 2009 John Wiley & Sons, Inc.
การควบคุมคุณภาพในการผลิต
ี ฏิบตั ิ เพือสนองตอบความ
 การควบคุมคุณภาพในการผลิต เป็ นกิจกรรมและกลวิธป
ต้ องการด้ านคุณภาพ โดยมีกจิ กรรม 4 กิจกรรมดังต่อไปนี
- การทวนสอบ คือ เมือปัญหาเกิดขึน สามารถย้ อนกลับไปหาสาเหตุของปัญหาได้
- การตรวจสอบ ขันตอนของการตรวจสสอบทางควบคุม ประกอบด้ วย
1) ตรวจสอบและควบคุมวัตถุดบิ
2) ตรวจสอบชินส่วน และควบคุมกรรมวิธกี ารผลิต
3) ตรวจสอบผลิตภัณฑ์สาํ เร็จรูป
- การวัด
- การทดสอบ
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Chapter 5
ขันตอนควบคุมคุณภาพ
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Chapter 5
ความหมายของ Precision และ Accurate
Accurate
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Precision
Accurate & Precision
Chapter 5
ระบบกระบวนการผลิตผ่านแผนภูมคิ วบคุม
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Chapter 5
Basic SPC Tools
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Introduction to Statistical Quality Control, 6th Edition by Douglas C. Montgomery.Chapter 5
Copyright (c) 2009 John Wiley & Sons, Inc.
5.2 Chance and Assignable Causes of Variation
• A process is operating with only chance causes of variation
present is said to be in statistical control.
• A process that is operating in the presence of assignable causes
is said to be out of control.
3 sources of
variability
• Improperly
adjusted /
controlled
machines
• Operator
errors
• Defective
raw materials
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Chapter 5
5.3 Statistical Basis of the Control Chart
 A control chart contains
 A center line
 An upper control limit
 A lower control limit
 Process is in control
 No action is necessary
 Process is out of control
 Investigation / action are
required to find / eliminate
assignable causes
 Close connection between
control charts and
hypothesis testing
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Introduction to Statistical Quality Control, 6th Edition by Douglas C. Montgomery.Chapter 5
Copyright (c) 2009 John Wiley & Sons, Inc.
Purpose of Control Charts
 Quickly detect process shifts -> Identify assignable causes
-> Take corrective actions (before many nonconforming
units are manufactured)
-> Reduce process variability -> Improve process quality
-> Maximize product quality -> Satisfy customers
-> Gain market share
 That is, a control chart is an efficient on-line process-
monitoring technique.
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Chapter 5
Additional Purposes of Control Charts
 Control charts may also be used to estimate the
parameters of a production process and consequently
determine process capability.
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Chapter 5
Photolithography Example
 Important quality characteristic in hard bake is resist flow width
 Process is monitored by average flow width
 Sample size of 5 wafers
 Process mean is 1.5 microns
 Process standard deviation is 0.15 microns
 Note that all plotted points fall inside the control limits
 Process is considered to be in statistical control
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Introduction to Statistical Quality Control, 6th Edition by Douglas C. Montgomery.Chapter 5
Copyright (c) 2009 John Wiley & Sons, Inc.
13
Introduction to Statistical Quality Control, 6th Edition by Douglas C. Montgomery.Chapter 5
Copyright (c) 2009 John Wiley & Sons, Inc.
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Introduction to Statistical Quality Control, 6th Edition by Douglas C. Montgomery.
Copyright (c) 2009 John Wiley & Sons, Inc.
Chapter 5
Shewhart Control Chart Model
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Introduction to Statistical Quality Control, 6th Edition by Douglas C. Montgomery.
Copyright (c) 2009 John Wiley & Sons, Inc.
Chapter 5
Use of control chart to improve the process
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Introduction to Statistical Quality Control, 6th Edition by Douglas C. Montgomery.
Copyright (c) 2009 John Wiley & Sons, Inc.
Chapter 5
Sample;
Out of Control
Action Plan
(OCAP)
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Introduction to Statistical Quality Control, 6th Edition by Douglas C. Montgomery.
Copyright (c) 2009 John Wiley & Sons, Inc.
Chapter 5
Reasons for Popularity
of Control Charts
1.
2.
3.
4.
5.
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Control charts are a proven technique for improving
productivity.
Control charts are effective in defect prevention.
Control charts prevent unnecessary process adjustment.
Control charts provide diagnostic information.
Control charts provide information about process
capability.
Introduction to Statistical Quality Control, 6th Edition by Douglas C. Montgomery.
Copyright (c) 2009 John Wiley & Sons, Inc.
Chapter 5
5.3.2 Choice of Control Limit
 3-Sigma Control Limits
 Probability of type I error is
0.0027
 Probability Limits
 Type I error probability is chosen
directly
 For example, 0.001 gives 3.09sigma control limits
 Warning Limits
 Typically selected as 2-sigma
limits
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Introduction to Statistical Quality Control, 6th Edition by Douglas C. Montgomery.
Copyright (c) 2009 John Wiley & Sons, Inc.
Chapter 5
5.3.5 Analysis of Patterns on Control Charts
•
•
•
•
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Pattern is very nonrandom in appearance
19 of 25 points plot below the center line, while only 6 plot above
From 4th point, 5 points in a row increase in magnitude, a run up
There is also an unusually long run down beginning with 18th
point
Introduction to Statistical Quality Control, 6th Edition by Douglas C. Montgomery.
Copyright (c) 2009 John Wiley & Sons, Inc.
Chapter 5
The Cyclic Pattern
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Chapter 5
Pattern Recognition
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Chapter 5
5.3.6 Discussion of the Sensitizing Rules
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Introduction to Statistical Quality Control, 6th Edition by Douglas C. Montgomery.
Copyright (c) 2009 John Wiley & Sons, Inc.
Chapter 5
4.3.7 Phase I and Phase II of Control Chart Application
 Phase I is a retrospective analysis of process data to
construct trial control limits
 Charts are effective at detecting large, sustained shifts in process
parameters, outliers, measurement errors, data entry errors, etc.
 Facilitates identification and removal of assignable causes
 In phase II, the control chart is used to monitor the process
 Process is assumed to be reasonably stable
 Emphasis is on process monitoring, not on bringing an unruly
process into control
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Introduction to Statistical Quality Control, 6th Edition by Douglas C. Montgomery.
Copyright (c) 2009 John Wiley & Sons, Inc.
Chapter 5
5.4 THE REST OF THE “MAGNIFICENT SEVEN”
1.
2.
3.
4.
5.
6.
7.
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Histogram or stem-and-leaf plot
Check sheet
Pareto chart
Cause-and-effect diagram
Defect concentration diagram
Scatter diagram
Control chart
Introduction to Statistical Quality Control, 6th Edition by Douglas C. Montgomery.
Copyright (c) 2009 John Wiley & Sons, Inc.
Chapter 5
Check Sheet
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Chapter 5
Pareto Chart
80:20 Rule
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Introduction to Statistical Quality Control, 6th Edition by Douglas C. Montgomery.
Copyright (c) 2009 John Wiley & Sons, Inc.
Chapter 5
28
Introduction to Statistical Quality Control, 6th Edition by Douglas C. Montgomery.
Copyright (c) 2009 John Wiley & Sons, Inc.
Chapter 5
Cause-and-Effect Diagram
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Introduction to Statistical Quality Control, 6th Edition by Douglas C. Montgomery.
Copyright (c) 2009 John Wiley & Sons, Inc.
Chapter 5
Defect Concentration Diagram
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Introduction to Statistical Quality Control, 6th Edition by Douglas C. Montgomery.
Copyright (c) 2009 John Wiley & Sons, Inc.
Chapter 5
Scatter Diagram
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Introduction to Statistical Quality Control, 6th Edition by Douglas C. Montgomery.
Copyright (c) 2009 John Wiley & Sons, Inc.
Chapter 5
ต้นทุนในการพัฒนาด้านคุณภาพ
 Prevention Costs ต้ นทุนทีใช้ ในการป้ องกัน ไม่ให้ สน
ิ ค้ าด้ อยคุณภาพ เช่น การ
ฝึ กอบรมพนักงาน
Training (ISO 9000)
2. Maintenance เช่น TPM (Total Preventive Maintenance), BD
(Break down Maintenance) และ CD (Corrective Maintenance)
1.
 Failure costs ต้ นทุนของเสีย, สินค้ าทีมีการแตกหัก จากการขนย้ าย จากการ
จัดเก็บ Failure costs แบ่งเป็ น 2 อย่าง คือ internal และ external
 Appraisal costs ต้ นทุนในการประเมินคุณภาพ การตรวจสอบ (Inspection)
เช่น การวัด, การชังนําหนัก การทดสอบ(Testing) เป็ นการหาสมรรถนะ เมือเทียบ
กับค่ามาตรฐาน มี 2 อย่าง คือ
1.
2.
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Destructive testing ทดสอบแบบทําลาย เช่น การทดสอบแรงดึงของเหล็ก
Non-Destructive testing การทดสอบแบบไม่ทาํ ลาย รวมถึงค่าแรงงานต่างๆ
Chapter 5
แสดงจุดคุ้มทุนของต้นทุนทางด้านคุณภาพ
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Chapter 5
แผนภาพทังหมดรวมเรียกว่า Quality Cost Model
Prevention Cost 40%
Traditional Cost
มองเห็นและรายงานได
Appraisal Cost 10%
Failure Cost 50%: Internal & External
Failure Cost: Difficult to Report
Hidden Cost
ไมสามารถมองเห็นได
Lost Opportunities
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Chapter 5