From data-set in column A the CP is 1.17, Cpk 1.03 and statistical is 0.11% out of tolerance, this is visible in the rows: Cp, Cpk and % out of tol of the result array. The values are calculated with the tolerance borders in Max Tol. and Min Tol Cpk level meanings. There are certain process capability levels that have certain meanings for your process. These are therefore common targets for process improvement and KPIs for your business: A process capability of at least 1.33 means that the process is 'capable' and will meet the customer's specification limits. It relates to a. Two tables below provide both short-term and long-term conversions of Sigma Level (Z-Score), CPK or PPK, and Defect Rate respectively. Notice the difference between short-term and long-term is an industry standard 1.5 shift of the Sigma Level . A Cpk of less than 1.0 means that the process is not capable of meeting its requirements. So, if a Cpk is between 1.33 and 1, the 'justification' is that the process barely meets requirements. Less than that means the process doesn't meet Compare Cpk with a benchmark that represents the minimum value that is acceptable for your process. Many industries use a benchmark value of 1.33. If Cpk is lower than your benchmark, consider ways to improve your process, such as reducing its variation or shifting its location. Compare Cp and Cpk
Cr = 1/Cp Cp = 1.33 ~ Cr = 0.75 (data fits 75% of tolerance) Cpm Formula The Cpm is an uncommonly used Capability Index that can be used when you have a target value Cpk > 1.33 : Good performance of the process Cpk > 3 : Loose specification of limits The difference between the process capability index is that unlike Cp, Cpk takes into account the possibility that the process mean may be shifted from the mean of the design limit range From the Cpk value, one can derive that Machine 1 is better than 2. Since Cpk uses specification limits and parts variation (sigma), we can also arrive at the yield processed and losses from the machine. Cpk = or >1.33 indicates that the process is capable and meets specification limits Process capability index (Cpk) is a statistical tool, to measure the ability of a process to produce output within customer's specification limits. Cpk = or >1.33 indicates that the process is capable and meets specification limits. One may also ask, what is the PPM for 1.33 CPK
Note that Cp = Cpk = 1.33. The sigma level is now 4 - the specification limits are now four standard deviations away from the average. The out of specification has decreased from 2700 to about 63 ppm. The standard deviation in the third curve has decreased further - to 0.6 1.33 1.25 New process 1.50 1.45 Safety or critical parameter for existing process 1.50 1.45 Safety or critical parameter for new process 1.67 (in terms of DPMO/PPM) 0.33 1 0.3085375387 30.85% 691462 0.67 2 0.6914624613 69.15% 308538 1.00 3 0.9331927987 93.32% 66807 1.33 4 0.9937903347 99.38% 6209 1.67 5 0.999767370 . For the process data in this histogram, Cpk is 1.09. Because Cpk less than 1.33, the potential capability of the process does not meet customer requirements. The process is running too close to the lower specification limit. Because the process is not centered, Cpk does not equal Cp (2.76) The higher the Cpk, the better is the capability of the process to meet its requirements. In the industry, a Cpk of less than 1.66 needs a closer look. A Cpk that's less than 1.33 needs some action to make it higher, and a Cpk of less than 1.0 means that the process is not capable of meeting its requirements When Cpk is negative it means that a process will produce output that is outside the customer specification limits. When the mean of the process is outside the customer specification limits the value of Cpk will be Negative; We generally want a C pk of at least 1.33 [4 sigma] or higher to satisfy most customers
Hallo, You know when we set at target cp and cpk are same. cp = T/6s for 1.33 it will be 8/6 means Tis equivalent to 8s hence half of tolerance or target is equale to 4s Cpk= USL-Target/3s means 4s/3s=1.33 I hope it clarify how cpk 1,33 is equivalent to 4s Regards P K Josh Assumptions No analysis would be complete without properly noting the assumptions made. In the above table, we have assumed that the standard sigma shift of 1.5 is appropriate (the calculator allows you to specify another value), the data is normally distributed, and the process is stable Cpk 0.59 Z.Bench 1.37 Z.LSL 1.97 Z.USL 1.55 Ppk 0.52 Cpm * Overall Capability Potential (Within) Capability PPM < LSL 0.00 PPM > USL 50000.00 PPM Total 50000.00 Observed Performance PPM < LSL 12648.50 PPM > USL 39415.05 PPM Total 52063.54 Exp. Within Performance PPM < LSL 24471.99 PPM > USL 60915.50 PPM Total 85387.49 Exp. Overall Performance. You know, things like Cpk, Ppk, sigma level, ppm out of spec and so on. Very pretty charts. Looks like your supplier is really performing for you. You note one capability chart that has a Ppk = 1.14 and a Cpk = 2.07. Why are those different? Well, it doesn't matter. The Cpk is above 1.33, which is what you asked the supplier for
Using this table, we can see that a Cpk (or Ppk) of 1.33 equates to a +/-4 sigma process which yield approximately 63 defects per million parts produced. To approximate the PPM for your specific Cpk level, you can shift over to Microsoft Excel In general, the higher the Cpk, the better. A Cpk value less than 1.0 is considered poor and the process is not capable. A value between 1.0 and 1.33 is considered barely capable, and a value greater than 1.33 is considered capable. But, you should aim for a Cpk value of 2.00 or higher where possible. cpk ppm calculator › Verified 6 days ag Case 2: Cpk = 1 to 1.33 (A Barely Capable Process) This process will produce greater than 64 ppm but less than 2700 non-conforming ppm. This process has a spread just about equal to specification width
• If Cpk = 1.0, the process is barely capable • Suggest Cpk be greater than 1.33 • Suggest calculating the lower CI for Cpk 11 Q10: Variability Reduction. Details: 1.33 ≤ Ppk ≤ 1.67 The process may not meet customer requirements. After part approval, begin production with additional attention to the characteristic until an ongoing Cpk ≥ 1.33 is achieved. Ppk < 1.33 The process is substandard for meeting customer ppm vs cpk › Verified 4 days ag
1.33 ≤ Ppk ≤ 1.67 The process may not meet customer requirements. After part approval, begin production with additional attention to the characteristic until an ongoing Cpk ≥ 1.33 is achieved. Ppk < 1.33 The process is substandard for meeting customer requirements. Process improvements must be given hig 4. Most practitioners consider a Capable process to be one that has a Cpk of 1.33 or better, and a process operating between 1.0 and 1.33 is marginal. Many companies now suggest that even higher levels of Cpk be maintained by their suppliers Many practitioners use a Cpk of 1.33 as the gold standard, so we'll treat that as the gold standard here, too. Suppose we collect some data and run a capability analysis using Minitab Statistical Software. The results reveal a Cpk of 0.35 with a corresponding DPMO (defects per million opportunities) of more than 140,000. Not good >1.33 or >1.67 are typical acceptability levels for Cp. A high value for Cp and low value for Cpk means the process is precise (narrow distribution) but work needs to be done to get the mean centered around the midpoint of the specification limits The magnitude of Cpk relative to Cp is a measure of how off center the process is and the potential improvement possible by centering the process. Cpm/Ppm Estimates the capability of a process, and is dependent on the deviation of the process mean from the target
Process Capability Index (Cpk): It shows how closely a process is able to produce the output to its overall specifications. More Value of Cpk means more process capable. Cpk value <1 means bell curve will out of USL/LSL; Common Cpk vale=1,1.33,1.67 & 2; The Cpk value of a startup manufacturing organization is supposed to be 1.33 Process capability analysis with normally distributed values. Calculation of CPK, CP and PPM. Calculation and chart creation with Microsoft Excel DPPM stands for Defect Parts Per Million in six sigma metric conversion. DPPM conversion is most commonly used in manufacturing sector. DPPM is often used when assessing the defect rate of a continuous material. The following table will convert Defects Parts Per Million to a short term or long term process sigma level Cpk - Cpk ppm (Cpk) ppm (Cpk-) 1.52 2.0 0 4 1.26 1.67 0 166 0.98 1.33 66 3,240 0.72 1.0 2,670 31,960 0.45 0.67 44,432 178,342 0.17 0.33 322,174 601,232 The Impact of Single-Sided Cpk Confidence Interval on Ppm Estimates The numbers with single-sided Cpk a little better than with double-sided but the overal Cpk is the centering capability index. It measures how well the data is centered between the spec limits. Use Cp Cpk when you have a sample, not the population, and are testing the potential capability of a process to meet customer needs. Important Quote: Cp and Cpk use Sigma estimator. Cp, Cpk Formula & Calculations: (Cpk > 1.33 is desirable
This goal can be expressed in terms of process sigma level or in terms of Cpk/Ppk. Typically, it is considered that Cpk and Ppk should be greater than 1.33 (sigma level 4) in order to declare a process to be good or capable. Examples of process capability and process performance analysis QTrendControl demo applicatio Der cpk Wert ist somit eine gute Messgrösse, um die Auswirkungen von verschiedenen Einflussfaktoren zu analysieren, ist das Ishikawa oder Ursache - Wirkungs - Diagramm. Zusammenhang Cpk und Ausschuss in % und ppm. Die Fähigkeitsindizes cp und cpk dienen der Prozesslenkung
CPK 1.33 = 63 NON-CONFORMING PARTS OUT OF 10,000 CPK 1.67 = 1 NON-CONFORMING PART OUT OF 1,000,000 CPK 2.00 = 16 NON-CONFORMING PARTS OUT OF 1,000,000 As you can gather from the table, the more the CPK value increases, the less scrap you can produce Note: C pk values of 1.33 or greater are considered to be industry benchmarks. This means that the process is contained within four standard deviations of the process specifications. Case 2: C pk = 1 to 1.33 ( A Barely Capable Process ) This process will produce greater than 64 ppm but less than 2700 non-conforming ppm ppb to ppm conversion How to convert ppb to ppm. ppm and ppb are defined as: 1ppm = 1/10 6 = 10-6. 1ppb = 1/10 9 = 10-9. So. 1ppm = 1000ppb. The number of parts-per million x ppm is equal to the number of parts-per billion x ppb divided by 1000:. x ppm = x ppb / 1000. Example: 7000ppb is equal to 7ppm Sigma Cpk Ppm Conversion Chart. See also . For example, if the Cpk for each characteristic is 1.33, then the probabilities that2 days ago . Link profile: Free Six Sigma DPMO/PPM, Sigma, Yield, and Cpk Look Up Table16 Apr 2006 . Free desktop six sigma, DPMO/PPM, Yield, Cpk calculator and converter The Cpk formula, applies an estimate of sigma, which details the potential of a process to meet specifications. The Cpk formula, includes reference to the process mean. Where Cpk = 1, then 99.73% of all data points will reside within the specification limits, i.e. 99.73% of outputs from a process will be within specification. The meaning of Cpk =1
Example 1 - Similar Cpk and Ppk. As the graph on the left side shows, there is not a lot of shift and drift between subgroups compared to the variation within the subgroups themselves. Therefore, the within and overall standard deviations are similar, which means Cpk and Ppk are similar, too (at 1.13 and 1.07, respectively) View Test Prep - 058_Cpk to PPM-DPMO Conversion Chart from SIX SIGMA green belt at Villanova University. Cpk to DPMO Conversion Chart The following table gives a comparison of various Cpk levels and 0.70 1.20 17,864 0.77 1.27 10,724 0.80 1.30 8,198 0.83 1.33 6,210 0.90 1.40 3,467 0.97 1.47 1,866 1.00 1.50 1,350 1.13 1.63 337 1.17 1.67 233 1. CPK 0 > 1 > 1.33 > 2.0 % N. C. 50 % < 0.27 % < 0.006 % APPROX 0 PPM 500 K < 2700 < 60 < 2 BILLION. Title: PowerPoint Presentation Author: Business Admin Created Date Biggest a problem is coming from a misconceptions about ppm mean when customers request zero ppm and pro ess capability CpK = 1.33. This request from a customer clearly shows that the customer hasn't understood and understands his processes. This article shows the cohesion of ppm and process capability with an understanding of how the ppm value.
as defined by CpK Quality, the PDT or the supplier's internal requirements. Critical/safety and significant characteristics shall have a minimum 1.67 Ppk at PPAP, and 1.33 Cpk in production, unless otherwise waived by CpK Quality. If there is any variation in these values, or the required capability cannot be met, contact CpK Qualit PPM-Observed (from receiving inspection) and PPM-Calculated (from the Normal Distribution). Table 2 PPM and Cpk fraction non-conforming (f.n.c.) Cpk PPM.333 317,400.667 45,500 1.0 2,700 1.33 63 1.50 7 1.67 0.6 2.00 2.0 PPB *Note: This comparison of Cpk and PPM does not include the 1.5σ shift included in the Motorola Six Sigma program.
The Bar Is Raised Back in the days of TQM, (Total Quality Management) it was generally accepted that a team should strive to get a process to a level where Ppk is 1.33 or greater. A Ppk of 1.33 means that there are four sigma between You've reached the end of your free preview. Want to read the whole page In the above process Cp=1.33 and Cpk=1.11 and Capability Ratio Cr=0.75 Since Cp is 1.33 and Cr = 0.75, The process is capable with strict monitoring. Cpk(Lower) is 1.55, the process center slightly shifts to the lower side which has to shifted to center as nearly as possible for having better Cpk near 1.33 Process Capability Analysis for Normal Distributions CP and PPM interpretation Process Spread LSL USL Specifications Case 2: 1 < CP < 1.33 A barely capable process This process will produce greater than 64 PPM but less than 2700 non-conforming PPM. This process has a spread just about equal to speci cation width. It should be note So Cpk is \$$0.67\$$, indicating that a small percentage of the process output is defective (about \$$2.3\%\$$). Without reducing variability, the Cpk could be improved to a maximum \$$1.33\$$, the Cp value, by centering the process Feature 1: Cpk must be more than 1 Feature 2: Cpk must be more than 1 Feature 3: Cpk must be more than 1,33 Yield needs to be more than 85%. How could be the required Cpk values recalculated into Yield? If with such Cpk values is possible to achieve for example Yield of 85 percent
Cp > 1.33 the process is capable Cp = 1.00 to 1.33 the process is marginally capable Cp < 1.00 the process is incapable. This set of definitions is arbitrary. When the process creates item measurements with a normal distribution, and the Cp = 1, we will expect a defect rate of 2,700 ppm* Cp, Cpk u & Cpk L Determine upper and lower spec limits Calculate the mean Determine or estimate the standard deviation Calculate Cp Calculate Cpk u & Cpk L Cpk should be at least 1.0 or better yet, 1.33 An acceptable Cpk value is dependent upon: How critical the measured process is to downstream processe Cpk requires the assumption that the measurements are normally distributed. The formula for the calculation of Cpk is . Cpk = min(USL - μ, μ - LSL) / (3σ) where USL and LSL are the upper and lower specification limits, respectively. A process with a Cpk of 2.0 is considered excellent, while one with a Cpk of 1.33 is considered adequate Cp of 1.33 equals to Sigma Level of 4. So, if a process had 10,000 PPM defects to the left of LSL and 20,000 PPM defects to the right of USL, then Cpk will look at both of them and then compute the process capability number related to 20,000. As pointed out earlier, Sigma Level (Bench) looks at defects on both sides and adds them up..
When the Cpk calculation is a high number (general industry guideline is 1.66 or higher), then it is a good indication the process is statistically in control. If the Cpk and Ppk calculations are very close or equal, then there is an even better indication that the process is statically in control A Ppk value of 1.67 gives you a Z of 5 for your long term capability The 1.33 Cpk yields a short term Z of 4. Since a 1.33 Cpk value is the standard in many industries I assume that the customer preceives the 1.67 Ppk to be a tighter requirement
.0, the process is capable. The goal is to reduce variation so that all of the points fit within the specification limits. - Capability Indices Cp / Cpk Sigma 1.0 3 1.33 4 1.67 5 2.0 6 A company targeting five-sigma level will aim for Cpk = 1.6 Understanding how Cp & Cpk are used to ensure quality Page 3 of 4 146-008 TABLE 1 (Expected defects listed for six processes with Cp values ranging from 1.00 to 2.00) Distribution Cp Centered Cpk Expected Defects ±4.5 sigma 1.50 YES 1.50 3.4 ppm ±6.0 sigma 2.00 NO 1.50 3.4 ppm ±6.0 sigma 2.00 YES 2.00 0.002 ppm
First, it s GREAT that your defect rate of 282 is very close to your Boss goal of 50 ppm. Second, your Cpk and your ppm numbers don t tie out with our expectations. You say Cpk for: * mounter is 1.0 and your mounting is 83ppm . * printing is 1.33 and your printing is 49ppm Cpk Vs. ppm - Relating Process Capability to Defect Rate. Eesemi.com Thus, every Cpk value corresponds to a percent defective rate, which may be expressed in parts per million, or ppm. Table 1 shows some Cpk values and their equivalent ppm rates. In the semiconductor industry, the Cpk goal for a process is normally set at 1.67, although a Cpk of 1.33 is still considered acceptable Cpk gives the best scenario for the existing process and helps to estimate the future performance of the process. In simple words, Cpk is a tool which is used to estimate the producer capability to produce a product for the customer specification. The formula to calculate Cpk is given by: Cpk = Min [(USL- Mean)/3 σ, (Mean-LSL)/3σ] Where .33 with a centered distribution and specification limit of ±4σ. The six sigma goal of Cp = 2 results in a defect rate of 3.4 PPM based on a specification limit of ±6 cr and an average shift of ±1.5σ
Cpk = D / 3s A fail-safe production with a theoretical overshooting of the tolerance by no more than 64 ppm (or 32 ppm for one side respectively) can only be guaranteed for Cpk >= 1,33. Search for CPK is also known as the Process Capability Index. This online Cp and Cpk calculator helps you to improve your process and to increase the output of the process within specification limits. The difference between Cp and Cpk is an indicator of how far the average of the process is from the target specification PPL 1.33 PPU 1.64 Ppk Cp 1.33 Cpm 1.35 1.72 CPL 1.54 CPU 1.89 Cpk 1.54 O bserv ed Performance PPM < LSL 0.00 PPM > USL 0.00 PPM Total 0.00 Exp. Within Performance PPM < LSL 1.95 PPM > USL 0.01 PPM Total 1.95 Exp. O v erall Performance PPM < LSL 33.28 PPM > USL 0.46 PPM Total 33.74 Within Overall PROCESS CAPABI LI TY OF STEP ES-1 VARI ABLE A1.
Cpk & Ppk Calculator Macro1 Macro2 Macro3 Macro4 Macro5 Data 1 Data 2 Data 3 Data 4 Data 5 Min. Max. Aver. Range USL LSL Ppk Std. Dev. Data 6 Pp Input Range Cell Links Statistics Calculations C4(d) Yield Count Below LSL Count Above USL Sum Protection Email for questions and bugs Cp Cpk Sigma (Short-Term) Data2 Sub1 Sigma (Short-Term) Data1. C pk. σ(sigma). Area under the Probability Density . Process Yield. Process Fallout in defective parts per million produced (ppm).33: 1.6826: 68.27%: 317311.67: 2.954 Cp = 1 (2700 ppm failures in total) Process not capable when Cp is < 1.33. Process is capable when Cp is. 2.5 > Cp >1.33. Cpk is used to. accommodate the 'shift' or 'drift' in the process by using the mean value rather than the target value. Cpk = | mu - Ln | /3s.d.. relationships among the following: Cpk, How Many Sigma Capability, Parts Per Million according to traditional statistical tables Parts Per Million taking into account the 6-Sigma Philosophy of an unfavorable shift in the mean of 1.5 Sigma Cpk, PPM, and Six Sigma Cpk (Defined as distance from process mean to the nearest spec, divided by 3.
2700 ppm Li Xm=10 Ls Xm+3s 63 ppm Cp=Cpk=1 Cp=Cpk=1.33 Xm-3s Xm-3 s 2700 ppm Tpre = 0,2 63 ppm Tnat Tpre = 0,2 Loss Function (system response to the variability of the characteristic under exam, in terms of loss of functionality) Upper tolerance limit Process variabilit Process Capability shift over time 1. Process Capability Julian Kalac, P.Eng Lean Six Sigma Master Black Belt 2. 2 Normal Distribution -6s -5s -4s -3s -2s -1s 0 1s 2s 3s 4s 5s 6s One Standard Deviation (s) This is a Normal distribution where: Mean = 0 Standard Deviation = .33 Gray Zone PPM > USL 0.00 PPM Total 0.00 O bserved Performance PPM < LSL 15.47 PPM > USL 2.33 PPM Total 17.80 Exp. Wit hin Performance PPM < LSL 2782.66 PPM > USL 1155.08 PPM Total 3937.74 Exp. O vera l Performance W ith n O v era
For very dilute solutions, weight/weight (w/w) and weight/volume (w/v) concentrations are sometimes expressed in parts per million. parts per million is abbreviated as ppm 1 ppm is one part by weight, or volume, of solute in 1 million parts by weight, or volume, of solution. In weight/volume (w/v) terms, 1 ppm = 1g m-3 = 1 mg L-1 = 1 μg mL- Conversions from Cpk to ppm and sigma assume that all defectives are occurring at one tail of the distribution with an average sigma shift of 1.5 sigma. (industry standard). Cpk MUST be seen as part of a package of information Synonymous with PPM. Defects : It is the failure of the process as per specification. It can be in a form of wrong information, wrong opening of call , no closing . Etc . Denoted by d. Unit (U) So, our Cpk would be the smaller one and that is 1.33. Hence, Process Sigma = 3 * 1.33 = 4 An article by K. Walters (Improving the Reflow Process with SPC) recommends a minimum Cpk value of 1.33 (600 ppm) for SMT. The report does state that three manufacturers achieved sub-200ppm. When comparing manufacturers' performance, it is important to ensure that apples are compared to apples
Cpk 0.35 Observed Performance PPM < LSL 110000.00 PPM > USL 180000.00 PPM Total 290000.00 Exp. Within Performance PPM < LSL 91186.50 PPM > USL 144933.01 PPM Total 236119.51 Exp. Overall Performance PPM < LSL 117604.95 PPM > USL 173049.32 PPM Total 290654.27 Within Overall Process Capability of Supp2. 29 Sa m p l e M e a cpk值0.67，1.0，1.33，1.67分别对应的是六西格玛水平的2，3，4，5水平等级，在西格玛不平中，1、2、3、4、5分别代表能力过小，不足，尚可、充足、过剩。同时与ppm也有相对应的数据。 8 Cr = 1/Cp Cp = 1.33 ~ Cr = 0.75 (data fits 75% of tolerance) Cpk vsPpk - Cp vs Pp Use Cp, Cpk when you have a sample and are testing the potential capability of a process to meet customer needs. Cp Cpk use sigma estimator. Use Pp, Ppk when you have the total population and are testing the performance of a process to meet customer needs MINITAB CPK圖形操作 C apability O verall C apability Pp 1.42 PPL 1.33 PPU 1.52 Ppk 1.33 C pm C p * 1.42 C PL 1.33 C PU 1.52 C pk 1.33 O bserved Perform ance PPM < LSL 0.00 PPM > U SL 0.00 PPM Total 0.00 Exp. W ithin Perform ance PPM < LSL 32.83 PPM > U SL 2.69 PPM Total 35.52 Exp. O verall Perform ance PPM < LSL 32.30 PPM > U SL 2.63. Therefore, if our Cpk is 1.25, the confidence interval predicts an actual Cpk of (0.75 to 1.75). Taking the curve out to 2000 samples, the Cpk estimate is +/- 0.1 and for 10,000 Cpk is +/- 0.04. Simply put: sample size matters. In addition, with increasing number of data points, Cpk approaches Ppk. So what exactly are Cpk and Ppk anyway
The cpk value is therefore a good measure to analyze the effects of different influencing factors, is the Ishikawa or cause - effect - diagram. Cpk and scrap correlation in % and ppm. The capability indices cp and cpk are used for process control. They enable statistical process control through the combination of mean value and standard. A Cpk below 1.66 should trigger an alarm to begin investigating but still allow production to run and when it falls below 1.33 production should be stopped and the problem corrected to ensure the process doesn't fall below 1.0 where you would be guaranteed to have failures Cpk 0.27 0.33 0.50 0.67 0.83 1.00 1.17 1.33 1.50 1.67 1.83 2.00 ** All values above are estimation based on standard normal distribution ** For bilateral tolerances, ppm computed based on Cpk / Ppk tends to overestimate defectives ** PPM may or may not = DPMO What is a good CPK? The higher the Cpk, the better is the capability of the process to meet its requirements. In the industry, a Cpk of less than 1.66 needs a closer look. A Cpk that's less than 1.33 needs some action to make it higher, and a Cpk of less than 1.0 means that the process is not capable of meeting its requirements
má Cpk= 1,04 a odhadované PPM 3.229, přiemž první proces má Cpk= 2,07 (2) a odhadované PPM procesů jenom 0,05 (3). U prvního procesu je předpoklad, že pří vyrobení 1 milionu kusů by se neměl žádný výrobek nacházet mimo limit (PPM 0,05 znamená, že při výrobě 100 milionů kusů, bude 5 NOK). U druhého proces It is important to note how the estimated non-compliance rate of 26.852% reported in Figure 3 is similar to the PPM total rate of 268525.98 reported in Figure 1. Figure 3: 30,000-foot-level Chart of Data from Table 1 3 . Summary: Process Capability Index Cp, Cpk, Pp, Ppk Issues and Resolutio Parts Per Million Parts (defective) per million (parts produced) Attention getter. Why use PPM or DPM? Cp = 1.33. 50%. Since the Cpk statistic explicitly includes the mean of the process, centering is being accounted for, as well as variability
Cpk = A divided by B A = Distance from process mean to closest spec limit B = 3 Standard Deviations (also called 3 Sigma) A bigger Cpk is better because fewer units will be beyond spec. (A bigger A and a smaller B are better.) Specification Limit Specification Limit Cpk = A divided by PPM or DPMO. They are directly linked to the values of Cp and Cpk. By convention, it will be calculated with our Cpk. The formula is as follows: PPM or DPMO = (1-Z Cpk) * 1 000 000. However, Cp can be used, but it will be less restrictive than Cpk since it assumes that the distribution is centered As I see it, in today's qualty levels achived (typically measured in hundreds of PPM or less and Cpk>1.33), acceptance sampling plans are just useless. A sampling plan with an AQL of, lets say 500 PPM (or AQL=0.05) is impracticable most of the times, because I need to inspect about 2000 parts to get, on average, one defective, and with such a.
PPM (Parts per million) is a measurement used by many customers to measure quality performance. Definition: One PPM means one (defect or event) in a million or 1/1,000,000 In the past a good supplier would have a defect rate of less than 1%, (10,000 PPM) Cpk Sigma Level Calculated Number of Out-of-Spec Products 1.00 3 2700 ppm 1.33 4 63 ppm 1.67 5 0.57 ppm 2.00 6 2 ppb Figure 1 Relation of Process Capability (Cpk) with a Theoretical Amount of Out-of-Specification Produc Six Sigma or 6 Sigma, Lean Flow or Lean Sigma Implementation Services for 6sigma DMAIC, sixsigma DFSS and Lea cpk : how good we are cpk = closest spec to x - x 3 sigma capability indices x 99.994 % 99.73 % 95.44 % 68.26 % capability - 4 v - 3 v - 2 v - 1 v + 1 v +2 v + 3 v + 4 v + / - 1 sigma + / - 2 sigma + / - 3 sigma + / - 4 sigma cp index is the maximum value of cpk probability of non - conformance cpk 0 > 1 > 1.33 > 2.