【正文】 was added to the process in shifts 4 and 7 and that in shift 12 a new operator started. 168。 Since each of the out of control points have assignable causes, we eliminate them from the data. 168。 The new control chart is then:69 168。 Now it appears that shift 15 is outofcontrol. 168。 Further checking shows that the temperature was set too high during this shift. 168。 Therefore, we want to eliminate this point so that in subsequent tests we can identify when this occurs. 168。 If we eliminate this point the new control chart is:Identifying Special Causes70 Final p Chartn UCL = + 3 x = n LCL = 3 x = = (negative control limits should be set to 0) n Now they should use this chart for all subsequent sampling until the process changes71 Determining if Your Process is “Out of Control”決定你的製程是否在穩(wěn)定狀態(tài)決定你的製程是否在穩(wěn)定狀態(tài)168。 Establish regions A, B, and C as one, two, and three s 168。 One or more points fall outside the control limits. 168。 2 out of 3 consecutive points fall in the same region A 168。 4 out of 5 consecutive points fall in the same region A or B 168。 6 consecutive points increasing or decreasing 168。 9 consecutive points on the same side of the average. 168。 14 consecutive points alternating up and down 168。 15 consecutive points within region C.ABCABCUsing an np Chart建立不良數(shù)管制圖建立不良數(shù)管制圖 n Np charts for number of nonconforming units. 以不合格品之數(shù)統(tǒng)計以不合格品之數(shù)統(tǒng)計 n Converted from basic pchart 由由 p管制圖演變而來管制圖演變而來 n Multiply p by sample size (n). 不良率乘以樣本大小不良率乘以樣本大小 n Formulas:Setting up a c chart建立缺點數(shù)管制圖建立缺點數(shù)管制圖Take about 2025 samples from the process. Each sample contains 1 unit. n For each unit count the number of occurrences for the observation of interest. n Calculate the average number of occurrences per unit. This is CBAR. n Calculate the upper lower control limit for the CBAR chart using the following formulas: Using an u Chart建立單位缺點數(shù)管制圖建立單位缺點數(shù)管制圖 n A u chart is used when the unit size inspected for defects is not constant. In these cases the unit is often referred to as an area of opportunity (ni). n The average occurrence per area of opportunity (. the center line) is calculated as: n The same 25% variation rule discussed for pcharts applies here as well. Control limits are calculated as:75 Figure76 425 GramsMean 平均值 Process Distribution 製程分配 Distribution of sample means 樣本平均值分配 Sample Means and theProcess Distribution樣本平均值與製程分配樣本平均值與製程分配77 Process Capability製程能力製程能力 181。 , Nominal value 800 1000 1200 HoursUpper specification Lower specificationProcess distribution(a) Process is capable78 Process Capability製程能力製程能力 Lower specificationMeanUpper specification Two sigma181。, Nominal value79 Process Capability製程能力製程能力 Lower specificationMeanUpper specification Four sigmaTwo sigma181。 , Nominal value80 Process Capability製程能力製程能力 Lower specificationMeanUpper specification Six sigmaFour sigmaTwo sigma181。 , Nominal value81 Process Capability製程能力製程能力168。Capable 168。Very capable 168。Not capableLSL USLSpec Process variation82 Process Capability Cpk製程能力指數(shù)製程能力指數(shù)Assumes that the process is: ?under control ?normally distributed ?假設(shè)製程為穩(wěn)定且為常態(tài)分配nCpk =min(Cpu , Cpl) nCpu=(USL181。)/3 nCpl =(181。LSL)/3Precision精密度Capability準確度83 Meanings of Cpk Measures Cpk 量測之意義量測之意義Cpk = negative numberCpk = zeroCpk = between 0 and 1Cpk = 1Cpk 184 Statistical Process Control – Identify and Reduce Process Variability統(tǒng)計製程管制統(tǒng)計製程管制 確認並降低製程變異確認並降低製程變異Lower specification limitUpper specification limit(a) Acceptance sampling(b) Statistical process control(c) cpk 185 Quality Control Approaches品質(zhì)管制方法品質(zhì)管制方法n Statistical process control (SPC)統(tǒng)計製程管制統(tǒng)計製程管制 n Monitors production process to prevent poor quality 監(jiān)控產(chǎn)品製程以預(yù)防不良品質(zhì)監(jiān)控產(chǎn)品製程以預(yù)防不良品質(zhì) n Acceptance sampling允收抽樣允收抽樣 n Inspects random sample of product or materials to determine if a lot is acceptable隨機抽樣檢驗產(chǎn)品或物料以決定此批是否隨機抽樣檢驗產(chǎn)品或物料以決定此批是否允收允收86 Sampling vs. Screening抽樣與篩選抽樣與篩選n Sampling抽樣抽樣 n When you inspect a subset of the population n 群體批中檢查小批群體批中檢查小批 n Screening n When you inspect the whole population n 群體批中檢查全數(shù)群體批中檢查全數(shù) n The costs consideration n 成本的考量成本的考量 ,經(jīng)濟的原則經(jīng)濟的原則Acceptance Sampling允收抽樣允收抽樣n Accept/reject entire lot based on sample results 整個允收整個允收 /拒收是樣品結(jié)果為基礎(chǔ)拒收是樣品結(jié)果為基礎(chǔ) n Not consistent with TQM of Zero Defects 與與 TQM的零缺點不同的零缺點不同 n Measures quality in percent defective 以缺點百分率測量品質(zhì)以缺點百分率測量品質(zhì)Sampling Plan抽樣計劃抽樣計劃n Guidelines for accepting lot允收批之指導(dǎo)作允收批之指導(dǎo)作業(yè)業(yè) n Single sampling plan單一抽樣計劃單一抽樣計劃n N = lot size批量批量 n n = sample size (random)樣本大小樣本大小n c = acceptance number允收數(shù)允收數(shù)n d = number of defective items in sample樣本不良項目之樣本不良項目之數(shù)目數(shù)目n If d = c, accept lot。 else reject 若若 d = c, 允收此批允收此批 ,其他則批退其他則批退 Producer’s Consumer’s Risk生產(chǎn)者與消費者冒險率生產(chǎn)者與消費者冒險率n TYPE I ERROR = P(reject good lot) n a or producer’s risk, too nervous n 5% is mon n 第一種錯誤第一種錯誤 =將好批判成壞批的機率將好批判成壞批的機率 ,緊張忙亂緊張忙亂的錯誤的錯誤n TYPE II ERROR = P(accept bad lot)n b or consumer’s risk, absent minded n 10% is typical value n 第二種錯誤第二種錯誤 =將壞批判成好批的機率將壞批判成好批的機率 ,心不在焉心不在焉的錯誤的錯誤 Quality Definitions品質(zhì)的定義品質(zhì)的定義n Acceptance quality level (AQL) 允收水準允收水準 n Acceptable fraction defective in a lot 允許一批中不良的比例允許一批中不良的比例 n Lot tolerance percent defective (LTPD) 拒收拒收水準水準 ,批容許不良率批容許不良率n Maximum fraction defective accepted in a lot 允允許一批中最大不良的比例許一批中最大不良的比例 Operating Characteristic (OC) Curve作業(yè)特性曲線作業(yè)特性曲線 n Shows probability of lot acceptance 顯顯示批允收的機率示批允收的機率n Based on是基於是基於 : n sampling plan抽樣計劃抽樣計劃 n quality level of lot批品質(zhì)的等級批品質(zhì)的等級 n Indicates discriminating power of plan 顯示不同計劃的差異性顯示不同計劃的差異性92 Operating Characteristic Curve OC