CPK 制程能力分析

1、2020/7/10,Silitek Electronics (GZ) VQM Department,1,Cpk,制程能力分析,2020/7/10,Silitek Electronics (GZ) VQM Department,2,常态分配,2020/7/10,Silitek Electronics (GZ) VQM Department,3,Percentages Of The Normal Distribution,2020/7/10,Silitek Electronics (GZ) VQM Department,4,管制图与常态分配,+k,图2,X值在+k与-k之間之或然率(Probabi

2、lity)或称机率如右图.以图中斜线部分表示,其公式为:,群 体 平均值= 标准差= ,抽取一个,x,图1, -k,2020/7/10,Silitek Electronics (GZ) VQM Department,5,群体(制程)与样本间之关系,分配之期望值,分配之标准差,设 为样本平均,为群体平均,S=S为样本标准差,为群体标准差,在统计学上,注:如 可视为无限群体用上式,为有限群体之修正系数,设系有限数群体而 則 分配之标准差,2,1,4,3,2020/7/10,Silitek Electronics (GZ) VQM Department,6,群体(制程)与样本间之关系,样本平均值之分

3、配,群体平均值之分配,2020/7/10,Silitek Electronics (GZ) VQM Department,7,Cpk Vs Defective Yield,我們常用产品品质特性的常态分配与規格相比较,以決定产品的不良率.如右图所示产品品质特性的常态分配.,规格上限:USL (Upper Specification Limit) 规格下限:LSL (Lower Specification Limit) 落在规格上,下限外的斜线面积即为产品的不良率.,Standard Deviation from mean,2020/7/10,Silitek Electronics (GZ) VQ

4、M Department,8,目前在品管里常注重制程的分散宽度,故有定义制程能力为下式者:,群体标准差每不易直接求得一般以样本资料推定之,其推定方法有下列三式,:,(1)直接由样本特性值計算时,(2)由次数分配表計算时,(2) 管制图計算时,一般均采用公式(3),制程能力的数量表示法,1.分散宽度以 表示之.,制程能力= (或 ),d2,Cpk 計算時用此公式(1),2020/7/10,Silitek Electronics (GZ) VQM Department,9,两种错误之经济平衡点,Break even point, BEP,通常,在管制图使中会有两种错(ERROR). 第一种即是单制

5、程仍属管制状态,但卻因随机性原因点落于管制界限外时,为了寻找不存在之问题而导致成本增加. 第二种即是当制程已失去管制,但数据点由于随即问题仍落于管制界限內,因而误判制程处于管制状态,因而造成更大之损失.,2020/7/10,Silitek Electronics (GZ) VQM Department,10,The Accuracy of an instrument can be improved by recalibrating to reduce its error, but recalibrating generally does not improve the instruments

6、Precision.(Repeatability also sometimes known as “Precision”),Accuracy =0.3cm,方法一:,查标准常态分配表(拉普拉斯表)得Z=-1.33時,对应值为0.0918,长度超过16.1cm的支数: 6000*0.0918=550.8四舍五入得551支,方法二:,下述步骤与上同,故略,2020/7/10,Silitek Electronics (GZ) VQM Department,19,Ca,Cp不良时的一般处理方法,1.Ca不良时的一般处理方法,制造单位为主, 技术单位为副, 品管单位为辅.,2.Cp不良时的一般处理方法,

7、技术单位为主, 制造单位为副, 品管单位我辅.,2020/7/10,Silitek Electronics (GZ) VQM Department,20,制程能力指数CpK 综合Ca与Cp两值之指数,(1)CpK值之计算式有两种,B. 单边规格时:,(2)等級判定 CpK值愈大,品质愈佳.依CpK值 大小分为五級,等级,A,1.33 CpK1.67,B,C,D,CpK值,1.00 CpK1.33,0.67 CpK1.00,CpK0.67,A+,1.67 CpK,A. 双边规格时:,2020/7/10,Silitek Electronics (GZ) VQM Department,21,CpK之

8、处置原则,2020/7/10,Silitek Electronics (GZ) VQM Department,22,制程能力与规格之关系,或6代表制程在正常状态下变化之范围,称为自然公差(Natural tolerance)规格上下限之差為Su-SL,则 或6与Su-SL有下列三种关系(情況)如图示:,1. 6 Su-SL,2020/7/10,Silitek Electronics (GZ) VQM Department,23,2. 6 Su-SL,2020/7/10,Silitek Electronics (GZ) VQM Department,24,3. 6 Su-SL,2020/7/10

9、,Silitek Electronics (GZ) VQM Department,25,Evaluation form,2020/7/10,Silitek Electronics (GZ) VQM Department,26,2020/7/10,Silitek Electronics (GZ) VQM Department,27,Cpk为什么要大于或等与1.33 ?,1.Cp=0.67时,稳态控制下不合格品率为4.6%;,2.Cp=1.00时,稳态控制下不合格品率为0.27%;,3.Cp=1.33时, 稳态控制下不合格品率为0.0063%=63PPM,在图例上表示为中心沒有偏移 (实际中心值与

10、规格中心重合),DPPM,2020/7/10,Silitek Electronics (GZ) VQM Department,28,DR=DRL+DRR DR(Defect Rate):總不良 DRL (Defect Rate Left) :左不良 DRR (Defect Rate Right) :右不良,2020/7/10,Silitek Electronics (GZ) VQM Department,29,Table 1 Quality levels and Corresponding Number of Defects,2020/7/10,Silitek Electronics (GZ)

11、 VQM Department,30,Table2.The Number of Defective(Parts per Million)for Specified Off-Centering of the Process and Quality Levels,2020/7/10,Silitek Electronics (GZ) VQM Department,31,中心偏离时dppm的计算,off-center(),2020/7/10,Silitek Electronics (GZ) VQM Department,32,面積,z,常态曲线下之面积,e=2.718.,0,Z=(x- )/,投影片

12、16,2020/7/10,Silitek Electronics (GZ) VQM Department,33,2020/7/10,Silitek Electronics (GZ) VQM Department,34,2020/7/10,Silitek Electronics (GZ) VQM Department,35,2020/7/10,Silitek Electronics (GZ) VQM Department,36,制程能力研究之应用,1.对设计单位提供基本资料; 2.分派工作到机器上; 3.用來验收全新或翻新调整过的设备; 4.选用合格的作业员; 5.设定生产线的机器; 6.根据规

13、格公差设定设备的管制界限; 7.当制程能力超越公差时,決定最经济的作业水准; 8.找出最好的作业方法.,2020/7/10,Silitek Electronics (GZ) VQM Department,37,2020/7/10,Silitek Electronics (GZ) VQM Department,38,Item,No.,Quality,Level,Specification,Format,LSL,USL,DRL,(Dppm),DRR,(Dppm),DR,(Dppm),1,1 Sigma,1 Sigma,42.804,42.753,42.855,158655.26,158655.26

14、,317310.52,2,1.5 Sigma,1.5 Sigma,42.804,42.727,42.880,66807.23,66807.23,133614.46,3,2 Sigma,2 Sigma,42.804,42.702,42.906,22750.06,22750.06,45500.12,4,2.5 Sigma,2.5 Sigma,42.804,42.676,42.931,6209.68,6209.68,12419.36,5,3 Sigma,3 Sigma,42.804,42.650,42.957,1349.97,1349.97,2699.93,6,3.5 Sigma,3.5 Sigma

15、,42.804,42.625,42.982,232.67,232.67,465.35,7,4 Sigma,4 Sigma,42.804,42.599,43.008,31.69,31.69,63.37,8,4.5 Sigma,4.5Sigma,42.804,42.574,43.033,3.40,3.40,6.80,9,5 Sigma,5 Sigma,42.804,42.548,43.059,0.287105,0.287105,0.57,10,5.5 Sigma,5.5 Sigma,42.804,42.523,43.084,0.019036,0.019036,0.04,11,6 Sigma,6 S

16、igma,42.804,42.497,43.110,0.00099,0.00099,0.00,Prepared by :VQM /Xu Gang,Approved by: Howard Lin,B.Quality Level (For your reference and choosing),2020/7/10,Silitek Electronics (GZ) VQM Department,39,Times,Quality,Level,Nominal,T/2(),Spec,LSL,Spec,USL,Tolerance,Off-Center,(Sigma),1,4,42.804,0.204,42

17、.599,43.008,0.408,0.00,2,4,42.780,0.204,42.576,42.984,0.408,0.46,3,4.46,42.780,0.228,42.552,43.008,0.455,0.46,Ca,Cp,CpK,Grade,DRL,(Dppm),DRR,(Dppm),DR,(Dppm),0.00,1.33,1.33,A,31.69,31.69,63.37,0.12,1.33,1.18,B,4.05,202.05,206.10,0.10,1.49,1.33,A,0.43,32.03,32.46,Prepared by :VQM /Xu Gang,Approved by: Howard Lin,Verification,It