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1、MPT Confidential,Page 1,Capability Analysis过程能力分析,MPT Confidential,Page 2,测量阶段流程图,流程图(Process mapping),C “ 6Sigma”水平; Introduction to Z-score Z-值介绍 Process Capability for Non-Normal Data非正态分布的过程能力 Cycle-Time (Exponential Distribution)循环时间(指数分布) Reject Rate (Binomial Distribution)不合格(剔除)率(二项式分布) Defe
2、ct Rate (Poisson Distribution)缺陷率(泊松分布),MPT Confidential,Page 4,Process Control vs Process Capability过程控制和过程能力,1. Process Control过程控制 Means the process is operating in statistical control, i.e. common causes are the only source of variation. 意味是过程在稳定状态下生产,也就是说, 一般原因(偶然原因)是变异的唯一原因 Refers to “voice of
3、 the process”, i.e. one only needs data from the process to determine if a process is in control. 起源于”过程的声音”,也就是说,唯一来源于过程的数据来判定过程是否受控. Track performance of the process to verify if it forms a stable distribution over time, typically with a control chart with control limits computed from the process
4、data only. 随着时间过去,反馈过程的表现来验证它是否来自于一个稳定的分布,一般地,利用从过程数据计算控制界限的控制图来完成. Just because a process is in control does not necessarily mean it is a good process. 仅仅因为过程受控并不一定说它是个好过程.,MPT Confidential,Page 5,2. Process Capability过程能力 The “goodness” of a process is measured by process capability 过程的 “好坏”是过程能力测
5、量的 Compares “voice of the process” with “voice of the customer”, which is given in terms of specs. or requirements 比较 “过程声音”和 “客户声音”,哪一个是根据规格或需要给出的? Measures how well a stable distribution (process in control) matches up with customers specs. 测量一个稳定的分布(过程受控)符合客户规格的程度.,Process Control vs Process Capa
6、bility过程控制和过程能力,首先判定过程稳定,确定数据分布是正态的, 再计算过程能力和西格码质量水平.,MPT Confidential,Page 6,What is Capability 过程能力是.,When process is under control, capability is decided by customer demand and process performance(Product or service quality shifting degree). The more the process meets the customer need, the bette
7、r the capability will be. 过程在受控状态下时,客户要求与过程表现(产品品质或服务的品质变动程度)的比值, 如果过程表现越能满足客户要求,则过程能力越充分,反之则不足.,MPT Confidential,Page 7,Process Capability过程能力,Process Capability studies can过程能力研究可以: indicate the consistency of the process output 显示过程输出的稳定性 indicate the degree to which the output meets specificatio
8、ns 表明输出满足规格的程度 be used for comparison with another process or competitor 可以与另一过程或竟争对手相比较,MPT Confidential,Page 8,Process Variation过程变异,Process Variation is the inevitable differences among individual measurements or units produced by a process. 过程变异是不可避免的差别在单个测量或过程生产单位之间. Sources of Variation变异的来源:
9、within unit 产品内 (positional variation) 位置的变异 between units 单位之间 (unit-unit variation) 产品-产品的变异 between lots 产品批之间 (lot-lot variation) 批批的变异 between lines 生产线之间(line-line variation) 线-线之间的变异 across time 不同时间 (time-time variation) 时间-时间的变异 measurement error 测量误差(repeatability =1, ),Exponential (x; ),P
10、rocess Capability for Cycle Time周期时间的过程能力,MPT Confidential,Page 69,Example 4,A customer service manager wants to determine the process capability for his department. A primary performance index is the time taken to close a customer complaint. The goal for this index is to close a complaint within on
11、e calendar week. Performance over the last 400 complaints was reviewed.,一位客户服务经理想确定他的部门过程能力,主要评价指标为处理客户投诉的时间周期,目标为在一周内处理完一单客户投诉,过去的400%次投诉作为测量数据. 数据在此期01-03 Days,MPT Confidential,Page 70,Example 4,Stat Quality Tools Capability Analysis (Weibull),MPT Confidential,Page 71,Example 4,MPT Confidential,Pa
12、ge 72,Example 4A,Stat Quality Tools Capability Sixpack (Weibull),MPT Confidential,Page 73,Example 4A,MPT Confidential,Page 74,Alternatives for Non-Normal Data非正态数据解释,When all other methods fail, it may be necessary to fall back on a simple assessment of the total amount out of specifications. Simply
13、 count the number of defective units and divide by the total to compute the fraction defective. Another standard metric for this is the DPPM. 当所有方法失败,它需要返回到一个评估超出控制界限数量的简单方法,简单地查一下不合格品和全部产品的数量,然后计算不合格率, 另一个标准刻度也是DPPM If a Capability Index must be reported, the DPPM can be converted back into a Z val
14、ue, and then either Ppk = Z/3 or Cpk = Z/3 depending upon whether the data is long term or short term. 如果要得到过程能力指数,DPPM可以转化为Z-值,然后根据此数据是长期或短期得PPK=Z/3 或Cpk = Z/3,MPT Confidential,Page 75,Process Capability for Reject Rate不合格率的过程能力,For a Normal Distribution, the proportion of parts produced beyond a s
15、pecification limit is 对于一个正态分布,在控制界限下的比例部分.,Reject Rate,MPT Confidential,Page 76,Thus, for every reject rate there is an accompanying Z-Score, 这样一来,对于每一个不合格率都有一个对应的Z-值 Where这里 Recall that原先 Hence因此,Process Capability for Reject Rate不合格率的过程能力,MPT Confidential,Page 77,Estimation of Ppk for Reject Rate
16、 不合格率Ppk的计算: Determine the long-term reject rate (p) 计算长期不合格率(p) Determine the inverse cumulative probability for p, using Calc Probability Distribution Normal 计算相反的累计概率p, 点击 Calc Probability Distribution Normal Z-Score is the magnitude of the returned value Z-值是反推值的多少. Ppk is one-third of the Z-Score Ppk 是 Z-值的三分之一.,Process Capability for Reject Rate不合格率的过程能力,MPT Confidential,Page 78,Example of Process Capability Study for Reject Rate不合格率过程能力的例子,A sales manager plans t
