ProcessCapability过程能力

1、2003-11-15.1Process Capability 过程能力2003-11-15.2Contents目录Introduction引言Process Variation过程变差Types of Capability Studies能力研究类型Procedure for Assessing Capability 能力评估方法Form 表格:qua-301,305Procedure 程序-qua-301,305,3072003-11-15.3Introduction 引言Quality is designed into a product through the Advanced Prod

2、uct Quality Planning (APQP) process产品质量通过“产品质量先期策划”(APQP)来保证nAPQP assures that customer requirements are not lost in product and process design nAPQP确保在产品设计和工艺设计中考虑客户的要求nAPQP aims at minimizing variation through better design and through process controlsnAPQP的目标是通过更好的设计和过程控制，使变差最小化2003-11-15.4Introd

3、uction引言Process Capability Studies are integral to APQP. Their purpose is to 过程能力分析应成为APQP的一个组成部分。研究的目的是：nquantify process variation量化过程变差nanalyze the variation with respect to the customer specification依据客户提出的技术规范要求，对变差进行分析nassist mfg. and eng. in reducing variation帮助工程和制造减少变差nmeasure improvement a

4、nd long-term capability of the process衡量改进工艺过程的情况和长期过程能力2003-11-15.5Process Variation过程变差due to common causes由普通原因引起的变差due to special causes由特殊原因引起的变差2003-11-15.6Sources of Variation in Manufacturing Processes制造过程变差来源measurement检测input material输入材料fabricate/assemble制造/装配output product输出产品feedback反馈m

5、an人员machine设备method方法material材料environment环境2003-11-15.7Process Variation过程变差Capability studies focus on the output product, for which the distribution has three main properties:能力研究着眼于输出产品，其分布有三种主要属性。centering对中variation变差USL上公差限LSL下公差限shape形状2003-11-15.8Process Variation过程变差Control Charts are an e

6、ssential tool in any capability study在任何能力研究中，控制图都是必不可少的工具ncapability indices and measures can be misleading if the process is out of control如果过程失去控制，能力指数和措施会被误导nan out of control process is in need of immediate corrective action对于失去控制的过程，需要立即采取改进措施2003-11-15.9Types of Capability Studies能力研究的类型short

7、-term短期能力研究long-term长期能力研究2003-11-15.10Traditional Metrics Are We Capable?“ Im running to the high side of spec - just in case”“ The part is in spec, so get off my back!”2003-11-15.11Definitions: Cp in real life Consider the task of parking a car in your garage. If the garage door opening is larger

8、than the width of the car, it is possible to park the car inside.2003-11-15.12Short-term capability study: Cmk, Ppk短期能力研究：Cmk, Ppkinput aterial输入材料fabricate/assemble制造装配output product输出产品feedback反馈variation seen in output product comes primarily from fabricate/assemble从输出产品中所看到的变差主要来自制造/装配过程2003-11-

9、15.13A short-term capability study is too short in duration to be influenced by changing input material or process feedback. Therefore a short-term study only sees the sources of variation (man, machine, methods) that influence the fabricate/assemble block. 短期能力研究的时间很短，不会受到输入材料或过程反馈的影响。因此，这种分析只考虑影响制

10、造/装配过程的变差(人员、设备、方法)。Note注意2003-11-15.14+A short-term engineering study done on a A short-term engineering study done on a specific piece of equipment or tool prior to specific piece of equipment or tool prior to production release is called an initial production release is called an initial machine

11、capability study (for equipment machine capability study (for equipment validation).validation).在生产线开通之前，对单个设备或工具进行的短期在生产线开通之前，对单个设备或工具进行的短期工程研工程研 究，称为初始机器能力研究究，称为初始机器能力研究( (用于设备验证用于设备验证) )。+A short-term manufacturing study done to A short-term manufacturing study done to assess the readiness of the

12、 process for assess the readiness of the process for production of a specific part or family of production of a specific part or family of parts is called a preliminary process parts is called a preliminary process capability study (for production approval).capability study (for production approval)

13、.评价某一特定零件或一组零件生产过程准备情况的评价某一特定零件或一组零件生产过程准备情况的短期短期 制造研究，称为初始过程能力研究制造研究，称为初始过程能力研究( (用于生产件用于生产件批准批准) )。NoteNote注意注意2003-11-15.15Long-term capability study: Cpk长期能力研究：CPKinput material输入材料fabricate/assemble制造装配output product输出产品feedback反馈variation seen in output product comes from all sources从输出产品中所看到的

14、变差是由各种原因造成的。2003-11-15.16Definitions: Cpk In Real LifeSometimes, the car COULD make it, but alignment prevents it.2003-11-15.17Note注意A long-term capability study is long enough in duration to be influenced by changing input material and process feedback. Therefore a long-term study sees all or nearl

15、y all sources of variation in all blocks, depending on the length of the study. 长期能力研究的时间很长，改变输入材料或过程反馈会使其受 到影响。因此，这种研究能够反映出生产环节中的所有变差源 。2003-11-15.18+A long-term study done on a specific piece of equipment or tool for a specified length A long-term study done on a specific piece of equipment or too

16、l for a specified length of time is called an ongoing capability study.of time is called an ongoing capability study.在一段特定时间内，对单个设备或工装进行的长期研究，称为在一段特定时间内，对单个设备或工装进行的长期研究，称为现行能力研究。现行能力研究。+A long-term study done to monitor a process in manufacturing a specific part is A long-term study done to monitor

17、a process in manufacturing a specific part is called statistical process control (SPC).called statistical process control (SPC).为监测某一特定零件的生产过程进行的长期研究，称为统计过为监测某一特定零件的生产过程进行的长期研究，称为统计过程控制程控制(SPC)(SPC)。NoteNote注意注意2003-11-15.19Relationship of Capability Studies能力研究的关系We normally do a short-term study (

18、initial capability study? first to understand the process variation, not just to achieve a specific index value.我们通常先进行短期研究(“初始能力研究”)，以了解过程变差，而不仅仅为了得到一个具体的指数值。If the short-term study indicates an unacceptable process, corrective action must be taken, and then a long-term study is conducted.如果短期研究表明过

19、程是不可接受的，则必须采取改进措施， 然后再进行长期研究。2003-11-15.20Cpk and ppmCpk和PpmAssuming a Centered Normal Distribution假设是对中的正态分布Cpkppm defective0.67 45,6001.00 2,6001.33 671.67 0.672.00 1.67, and the control charts indicate a stable process如果Ppk1.67，且控制图表明过程是稳定的，the process is acceptable则此过程是可以接受的develop a plan for mo

20、nitoring process capability at regular intervals 应制订一项定期监测过程能力的计划nthis should be in the Control Plan该项计划应纳入控制计划中2003-11-15.38Procedure Procedure (for short-term studies)(for short-term studies)研究方法研究方法 ( (用于短期研究用于短期研究) )4(a single point beyond control limits with no other signs of instability and no

21、 (a single point beyond control limits with no other signs of instability and no discernible special causes is considered a stable process)discernible special causes is considered a stable process)( (若只有一个点超出控制限，而没有其它不稳定的迹象，若只有一个点超出控制限，而没有其它不稳定的迹象， 也没有可识别的特殊原因，则可认为这是一个稳定的过程也没有可识别的特殊原因，则可认为这是一个稳定的过程)

22、 )2003-11-15.39Procedure研究方法If Ppk 1.67, and the control charts indicate an unstable process 如果Ppk1.67，且控制图表明过程不稳定。 if there are points beyond the control limits, or trends, runs, cycles do appear on the control charts and/or an assignable cause can be determined in the process, take corrective acti

23、on on the process and repeat the short term study如果有多个点超出控制范围，或者在控制图上表现出明显的链 ，趋势和周期性，而且/或者可以确定造成变差的原因，则应采取改进措施，并重复进行短期能力研究。2003-11-15.40Procedure研究方法If 1.33 Ppk 1.67, and the control charts indicate a stable process, 如果1.33 Ppk 1.33 is achieved, and document corrective action in the control plan则此过程

24、在一定的条件下是可以接受的；在Cpk值( 长期能力)大于1.33之前，必须特别注意关键特性，并将改进措施纳入控制计划中。nexamples of special attention include inspection, pre-control, SPC, error-proofing, etc.所谓“特别注意”，举例来说是指检查、预控制、统 计过程控制、预防差错 ，等等。2003-11-15.41Procedure研究方法If 1.33 Ppk 1.67, but the control charts indicate an unstable process，如果1.33 Ppk 1.67,但过程控制图表明过程不稳定，ntake corrective action on the process and repeat the short term study应采取措施，提高过程稳定性，并重复进行短期研究。2003-11-15.42Procedure研究方法If Ppk 1.33, 如果Ppk 1.33 is achieved; get customer approval (if required) to continue with production; document corrective action in the control plan