1970到1980年代間，因日本產品品質的提升，使得它在國際市場深受消費者的喜愛，而美國產品在各地市場的佔有率則節節敗退。摩托羅拉(Motorola)是許多與日本廠商品質競爭失利的公司之一，為了挽回市場佔有率，遂提出六標準差的品質改善策略。在六標準差改善活動中，衡量步驟是一個非常重要的程序，其中標準差個數是常被用於衡量目前品質水準的一個工具。但在產業間，製程能力指標是另一個常被使用來衡量製造業製程水準的工具。企業內部的標準差改善專案是使用標準差個數來衡量品質水準，但企業間使用的品質溝通語言卻是製程能力指標；如果企業內部沒有將標準差個數轉換成製程能力指標值，則可能會造成與其他企業在品質上認知的差異，因此本文在第二章將針對標準差個數與製程能力指標值之間關係進行深入的研究。
    除此之外，製程能力指標也可以直接被使用於六標準差改善活動的衡量步驟中，用以衡量目前的製程水準，然而，因許多產品都同時擁有多個品質特性，顧客所願意接受的產品為每一個品質特性的製程能力都需符合規格。而單一的製程能力指標是無法同時衡量這種情況的，因此本文在第三章引用Chen et al.(2001)所發展的MPCAC模式來衡量多個品質特性的情況，並把MPCAC模式導入六標準差的衡量步驟中，建構六標準差下的MPCAC模式；進一步，引入Chou et al. (1990)的方法建構抽檢方式下的MPCAC模式，最後將上述所建構的MPCAC模式運用在棘輪式梅花扳手的製程改善。
    第四章則是延續第三章的概念，以製程能力指標Cpk為基礎，發展一套產品的製程能力評估模式PCAC，此模式可衡量一個產品同時擁有多個品質特性的情況，且可以快速的判斷出製程能力不足的原因是精度的問題還是準度的問題；進一步，把PCAC模式導入六標準差的衡量步驟中，建構六標準差下的PCAC模式，並實際的應用於縫紉機產業的六標準差改善專案。最後引入Chou et al. (1990)的方法建構抽檢方式下的PCAC模式，並把抽檢方式下的PCAC模式應用於長臂六角扳手的六標準差改善活動。

In 1970-1980’s, because of the promotion of Japanese product quality, makes it be popular to consumers in the international market; however, the marketing share of American products is decreasing in the worldwide. Motorola is many one of with Japanese manufacturer quality competition unfavorable situation companies, in order to retrieve the marketing share, it is proposed Six Sigma quality improvement strategies. In Six Sigma improvement, the measuring step is an extremely important procedure, in which number of Sigma is often a tool used in measuring the present quality level. But in the industry, Process Capability Index is another tool used to measuring process capability. The Six Sigma improving project of the enterprise uses number of Sigma integer to measure quality level, but the usage communicative language in the enterprise is the Process Capability Index. If the inner enterprise has not transformed number of Sigma into Process Capability Index value, then there will create the cognitive discrepancy in other enterprises on the quality. Therefore, this essay carries on a thorough research aiming at the relation between the number of Sigma and Process Capability Index in second chapter.
  In addition, the Process Capability Index can be also used directly in measuring step of Six Sigma improvement to measure the current process capability; however, many products all simultaneously have many quality characteristics, the product which the customer is willing to accept needs all process capabilities of each characteristic satisfy preset specifications. The single Process Capability Index can't measure this kind of condition in the meantime; therefore, this essay in the third chapter. According to Chen et al.(2001) to develop MPCAC Model to measure the condition of several quality characteristics. MPCAC Model constructing out of Six Sigma is inducted into the measuring step of Six Sigma; further, MPCAC Model is led to Chou et al. (1990) under the construction sampling model. Finally, above MPCAC Mode will apply the improving process of Profile of Offset Ratchet Wrenches.
  Chapter 4 continues the concept of third chapter, with the basis of Process Capability Index Cpk, developing the PCAC model to evaluate process capability. PCAC mode can measure a product to have the condition of several quality characteristics in the meantime, and can judge the shortage of process capability for the reason of the precision or accuracy. PCAC Model constructing out of Six Sigma is inducted into the measuring step of Six Sigma; further, PCAC Model applying to sewing machine industry in Six Sigma improvement case is led to Chou et al. (1990) under the construction sampling model. Finally, PCAC Mode will apply the improving process of Profile of T-Handled Hex Key Driver.

目  次

目錄……………………………………………………………………………………ii
圖目錄…………………………………………………………………………………iv
表目錄…………………………………………………………………………………vi
通用符號一覽表……………………………………………………………………viii
基本假設 ……………………………………………………………………………viii
目  錄

圖目錄…………………………………………………………………………………iv
表目錄…………………………………………………………………………………vi
通用符號一覽表……………………………………………………………………viii
基本假設 ……………………………………………………………………………viii

第1章   	緒論……………………………………………………………………	1
1.1	研究動機與目的………………………………………………………	1
1.2	相關文獻探討…………………………………………………………	3
1.2.1	六標準差………………………………………………………………	3
1.2.2	製程能力指標…………………………………………………………	6
1.3	本文結構………………………………………………………………	9
第2章	六標準差與製程能力指標之間的關係………………………………	12
2.1	前言……………………………………………………………………	12
2.2	常用的製程能力指標 ………………………………………………	14
2.3	製程未偏移下製程能力指標與六標準差之間的關係 ………… 	17
2.4	製程偏移1.5σ下製程能力指標與六標準差之間的關係………	23
2.5	小結……………………………………………………………………	26
第3章	六標準差下的MPCAC模式………………………………………	28
3.1	前言……………………………………………………………………	28
3.2	MPCAC基本模式……………………………………………………	31
3.3	抽檢方式下的MPCAC模式………………………………………	34
3.4	六標準差下的MPCAC模式………………………………………	37
3.5	實例……………………………………………………………………	41
3.6	小結……………………………………………………………………	44
第4章	六標準差下的PCAC模式…………………………………………	45
4.1	前言……………………………………………………………………	45
4.2	PCAC模式……………………………………………………………	46
4.3	六標準差下的PCAC模式 …………………………………………	47
4.4	運用PCAC模式於縫衣機產業的六標準差改善專案…………	53
4.5	抽檢方式下的PCAC模式…………………………………………	56
4.6	將抽檢方式下的PCAC模式運用於六角扳手的品質改善……	58
4.7	小結……………………………………………………………………	60
第5章	結論與後續研究 ……………………………………………………	62
5.1	主要研究成果………………………………………………………	62
5.2	未來研究方向 ………………………………………………………	63
參考文獻 …………………………………………………………………………  65
圖  目  錄

圖號                                                             頁次
圖 1.1   	本研究結構流程圖……………………………………………………	11
圖 2.1	當品質水準達6σ下，雙邊規格的製程分配圖…………………………	19
圖 2.2	當品質水準達6σ (USL-μ= 6σ)下，望小品質特性的製程分配圖……	22
圖 2.3	當品質水準達6σ (μ- LSL= 6σ)下，望大品質特性的製程分配圖……	22
圖 3.1	MPCAC分析圖……………………………………………………………	34
圖 3.2	抽檢方式下的MPCAC分析圖…………………………………………	37
圖 3.3	六標準差下的MPCAC分析圖…………………………………………	40
圖 3.4	棘輪式梅花扳手機械圖…………………………………………………	41
圖 3.5	棘輪式梅花扳手的MPCAC分析圖………………………………………	43
圖 4.1	PCAC分析圖………………………………………………………………	47
圖 4.2	製程右偏移的1.5σ圖……………………………………………………	48
圖 4.3	製程左偏移的1.5σ圖……………………………………………………	49
圖 4.4	三到六標準差之PCAC分析圖…………………………………………	52
圖 4.5	上軸軸承實際圖…………………………………………………………	53
圖 4.6	上軸軸承的PCAC分析圖………………………………………………	55
圖 4.7	抽檢方式下的PCAC分析圖……………………………………………	58
圖 4.8	長臂六角扳手圖…………………………………………………………	59
圖 4.9	長臂六角扳手的抽檢方式下之PCAC分析圖…………………………	60

表  目  錄

表號                                                             頁次
表 2.1   	∣μ－T∣=0時，三、四、五與六標準差水準的Cp、Cpk、Cpm、Cpmk及Spk對應值………………………………………………………	20
表 2.2	製程未偏移時，三、四、五與六標準差水準的Cpl、和Cpu對應值……………………………………………………………………23
表	2.3	∣μ－T∣=1.5σ時，三、四、五、六標準差水準下的Cp、Cpk、Cpm、Cpmk、Spk之對應值……………………………………………………25
表	2.4	在製程平均數μ偏移1.5σ時，三、四、五、六標準差水準下的Cpl和Cpu之對應值……………………………26
表	3.1	品質特性為1~10個時，CT與各品質特性良率下界的對應值………	32
表	3.1	品質特性為1~10個時，CT與各品質特性良率下界的對應值(續)…	32
表	3.2	品質水準為六標準差時，品質特性個數為3、4、5、6、7的C0值，及抽取的樣本數為100、200、300與400且信賴度為0.95時MV值………………………………………………38
表	3.3	棘輪式梅花扳手6個品質特性的製程能力指標值……………………	43
表	4.1	製程達三、四、五與六標準差水準下的Cpk與yield%的對應值……	50
表 4.2	品質水準分別在三、四、五與六標準差下，品質特性個數為t個時	
	的每一個品質特性最小應達到的製程能力指標……………………	51
表 4.3	上軸軸承各品質特性的製程精確度指標P與製程準確度指標A…55
表 4.4	為信賴度95%下，品質水準分別在三、四、五與六標準差，品質特性個數t，抽檢的樣本數n個時的製程能力指標最小值(Cr)………57
表 4.5	長臂六角扳手各品質特性的精確度指標 與準確度度指標 ………59

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