單邊規格產品族製程能力指標

Abstract

摘要 製程能力指標是評估產品製程品質與績效的方便且好用的工具，但目前大部分指標皆用於評估單一產品項的製程能力，而在實際的產業裡，每一種產品通常會有數種不同的型號，型號不同其規格也有所不同，在此統稱這些不同型號的產品為產品族。評估整廠產品族的製程能力是績效管理中制定品質目標的重要效標，同時也是產品安全規範的認證中所要求的重點。而在過去產業界是以最大產量的產品項之製程能力指標值來代表整廠製程能力指標值，這在多量少樣的生產模式下是可以被接受的。但若是在少量多樣的生產模式下則會缺乏代表性及客觀性，另外若以單一產品項作製程能力評估，只能看到各產品項製程能力指標值而缺乏具代表性的整廠製程能力指標值，因此造成業務顧客間或是工程製造部門間的溝通不便。而目前產品及製程設計是以模組化及群組化來實施，但若以單一產品項來評量其製程能力，則會使得整個製造系統缺乏相容性及整合性。因此為了簡化評量方法提昇管理的便利有效性及製造系統的相容整合性，應發展一套客觀的評估方法來評估整體產品族之製程能力。 本論文針對單邊規格產品族在全檢及抽檢的模式下，各提出一套製程能力的評估方法及改善程序。在研究流程方面首先定義研究動機、目的及架構並針對製程能力指標的沿革做回顧及分類。接下來探討單邊規格製程能力指標值與良率之關係並以良率的基礎，定義出一個可以反應整體良率的產品族製程能力指標。然後探討在全檢及抽檢模式下，以現有的製程能力指標為基礎，提出一套評估單邊規格產品族製程能力的方法與程序，同時針對望小型產品族的電容器損失角及汽車出廠廢氣檢驗作為全檢及抽檢模式下的實例探討。最後運用顏色管理及統計檢定的客觀方法，分別建立評核表以排定改善的優先順序，進而以重點管理模式來提昇整體產品族的製程能力。

Abstract Process capability indices are widely used as a flexible tool to evaluate the quality and performance of a process. However, most of the existing indices were applied only to a single item or product. This is usually not the case in manufacturing industry where products of different models and specifications were produced as a product family. Therefore, accreditation by the product safe regulations requires an agent to conduct a global evaluation on the process capability over the entire product family from a plant. In the past, the capability index of the process associated with the item of the largest amount was used as the process capability index for the whole plant. This is acceptable under the condition of large quantity and few varieties. However, this scheme may not be good in being representative and objective for cases associated with small quantity and large varieties. Furthermore, the capability index for a single product can only reflect the quality of a process and cannot be a representative to the capability of the whole plant. This will also result in mal-communication among customers and manufacturing departments. It is also noted that modularization is getting used in process design. Therefore using the capability index of a single process to evaluating the whole manufacturing system will be lack of compatibility and integrity. Thus new and objective methods should be developed to evaluate the capability of a whole process family. In this paper, a new method and an improved procedure will be proposed to evaluate process families of the one-sided specification type in the complete-inspection and the random-inspection modes. The motivation, the objective, and literature review of this research will first be introduced. The relationship between the one-sided capability indices and the yields will be discussed. A new index and evaluation procedure, which can reflect the global yield of a product family, will then be defined. Examples in capacitor loss corner and exhaust exam in car industry will be then discussed. Finally the Color Management method and statistical technology will be adopted to establish the exam table so that the priority for improvement can be determined and the capability of the whole process family can be enhanced