Cpk與Ppk製程指標應用於生產品質之研究-以某汽車零件廠為例

在台灣汽車零件(After Market,AM)製造產業中，客戶對於品質要求也越來越嚴格，如何有效地以最短時間、正確、快速、低成本地在電著塗裝(Electrophoretic deposition,ED)生產線上提供最穩定品質，也是目前汽車零件製造產業核心競爭能力之一。汽車零件製造業中不僅需要在產品的價格上有所競爭力，也要需滿足顧客的需求並生產各種高品質商品，導致生產過程必須趨向更嚴謹更準確的高品質要求，然而在台灣汽車零件製造產業中，客戶對於品質要求也越來越嚴格，如何有效地以最短時間、正確、快速、低成本地在電著塗裝生產線上提供最穩定品質，也是目前汽車零件製造產業核心競爭能力之一。且少量多樣的產品與複合材質都是目前的生產模式也是未來的趨勢，為了正確地估計與準確地推論製程能力指標Cpk與Ppk，許多文獻分別以各種方法或各種觀點來進行研究與分析，並提出使用Cpk與Ppk來管制先前品質，以避免初期品質落差造成市場抽驗或檢驗不合格或造成顧客風險大增。對業者而言，在Cpk與Ppk計算數據下可以提供最低之製程能力的重要資訊，對於品質工程師在監控製程與評估製程之績效，可提供製程或產品之品質保證，以提高顧客滿意度之服務水準。本研究目的以國內某汽車零件業工廠，在塗裝電著製程階段使用Cpk與Ppk製程能力指標與製程能力分析做塗裝電著製程階段管制，透過此方法來提升塗裝電著底漆品質，增加產業競爭力。

關鍵字

Cpk ； Ppk ；製程能力；電著塗裝；汽車零件

並列摘要

In the automotive aftermarket (After Market,AM) industry in Taiwan, customers are getting more and more demanding on their quality requirements. How the electrophoretic-deposition (Electrophoretic deposition,ED) production line can provide the most stable quality at the shortest time and in an accurate, fast and low-cost manner is also one of the core competitive factors in the current automotive AM industry. In the automotive AM industry, the product must not only be competitive in price, but must also must satisfy the customer’s needs for high quality. This requires more strict and accurate quality standards in the production process. However, in the automotive AM industry in Taiwan, customers are getting more particular about quality requirements. How the ED production line can provide the most stable quality in the most efficient, accurate, fast and low-cost manner is also one of the core advantages of the current automotive AM industry. The production of diversified products in small quantities and the use of composite materials are the current production modes and also constitute a future trend. To correctly estimate and accurately evaluate the process capability indices Cpk and Ppk, researches and analyses have been made with various methods or in various viewpoints in many literatures. These indices Cpk and Ppk are utilized to control first-stage quality to avoid preliminary quality differences, resulting in unsatisfactory random market inspection or examination results or in giving a significant risk to customers. For manufacturers, Cpk and Ppk calculation data can provide important information on the minimum process capability. For quality engineers involved in the monitoring process and in estimating the process performance, these data can provide quality assurance on the process or product so that a satisfactory customer service level can be upgraded. This study is intended to take the example a local factory of the automotive AM industry that uses the process capacity indices Cpk and Ppk in the electrophoretic-deposition process and uses process capability analysis for the control of the ED process. By using this method, this factory upgrades its ED primer quality, thus increasing its competitiveness in the industry.