1. 8-1 Is Process Capable ? The Quality Improvement Model Use SPC to Maintain Current Process Collect & Interpret Data Select Measures Define Process Is Process Capable ? Improve Process Capability Is Process Stable ? Investigate & Fix Special Causes No Yes No Yes Is Process Capable? Purpose:Determine the adequacy of the process with respect to customer /management needs.

2. 8-2 Is Process Capable ? Capable Process A stable process that meets customer requirements. 8222424610121416182026283032 Run Order UCL CL LCL Control Chart Lower SpecUpper Spec Target Histogram Capability assessments for unstable processes, may not be indicative of how the process is actually performing.

3. 8-3 Is Process Capable ? Assessing Process Capability l Counting Measures  The average percent defectives.  The average number of defects. l Instrument Measures  Comparing both the center of the process and the process variation

4. 8-4 Is Process Capable ? Capability Assessment for Counting Measures “Order Entry Process” Is this process adequate as is? Should it be improved? Week 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Total # Errors 15 22 18 10 13 9 27 12 24 22 8 26 16 20 10 16 9 15 20 320 0 5 10 15 20 25 30 35 5101520 Avg=16.0 LCL=4.0 UCL=28.0 Week Number of Errors Control Chart

5. 8-5 Is Process Capable ? Capability Assessment for Instrument Measures 8222424610121416182026283032 Run Order UCL CL LCL Control Chart Lower SpecUpper Spec Target Histogram Is this process adequate as is? Should it be improved?

6. 8-6 Is Process Capable ? Measures of Process Capability C p = Specification Range True Process Range = USL - LSL 6c6c C pk = Distance from process average to closest specification limit 1 2 True Process Range = min (USL -x,x - LSL) 3c3c Problem: We are assuming the process has a target that is in the center of the specification range, and that the process is in fact centered on that target. Note: a negative result is possible if the process average is outside specifications Benefits: Optimal values are attained by running exactly between specs. Can (must) be used for 1-sided specifications C p < 1.0  Process is not capable of meeting specs C p = 1.0  Process is marginally capable C p > 1.0  Process is capable of meeting specs C pk < 1.0  Process is not capable of meeting specs C pk = 1.0  Process is marginally capable C pk > 1.0  Process is capable of meeting specs Warning: Capability assessments for unstable processes, may not be indicative of how the process is actually performing.

7. 8-7 Is Process Capable ? How much material is out of spec?  In the short term?  In the long term? USL LSL Process Capability

8. 8-8 Is Process Capable ? Process Capability Ratios Voice of The Customer Voice of The Process USL LSL

9. 8-9 Is Process Capable ? Process Capability - The Strategy Centering –The Process Is On Target Spread – Reduce The Variation LSL USL Defects

10. 8-10 Is Process Capable ? 2 Key Metrics for Measuring Capability CMin( X-LSL 3 USL-X 3 pk ,) Process Capability Ratios

11. 8-11 Is Process Capable ? Process Capability Ratios - Concept Total Tolerance C Process Spread p 

12. 8-12 Is Process Capable ? LSL USL u = 30 Inches = 1 27 Inches 33 Inches Cp = __________ Sigma Level = __________ Process Capability – Example 1

13. 8-13 Is Process Capable ? Cp = __________ LSL USL u = 30 Inches = 1 29 Inches 31 Inches Sigma Level = __________ Process Capability – Example 2

14. 8-14 Is Process Capable ? Cp = __________ LSL USL u = 30 Inches =.333 28 Inches 32 Inches Sigma Level = __________ Process Capability – Example 3

15. 8-15 Is Process Capable ? Cp = __________ LSL USL 28 Inches 32 Inches u = 33 Inches =.333 Sigma Level = __________ Process Capability – Example 4

16. 8-16 Is Process Capable ? Process Capability Ratios CMin( X-LSL 3 USL-X 3 pk ,) C X-LSL 3 pL  USL-X 3 C pU  A metric to take into account process shift

17. 8-17 Is Process Capable ? CpU = ___________CpL = ___________ Cpk = ____________ LSL USL 28 Inches 32 Inches u = 33 Inches =.333 Process Capability – Example 5 Recall Cp=2.0

18. 8-18 Is Process Capable ? A Short-term Capability study covers a relatively short period of time (days, weeks) generally consisting of 30 to 50 data points. The actual number depends on the subject under study. Is The Process In Control ? Is It Producing Defects ? C P & C PK Measure Short-term Capability

19. 8-19 Is Process Capable ? A long-term capability study covers a relatively long period of time (weeks, months) generally consisting of 100-200 data points. Again, the actual amount depends on the subject under study. Is The Process In Control ? Is It Producing Defects ? Long Term Performance Short term Capability

20. 8-20 Is Process Capable ? A Further Look at Capability Compare the estimates of the process deviations from the short-term and long-term data What is the difference between the short-term and the long-term data? What implication does this have in doing capability studies? What is the difference between the short-term and the long-term data? What implication does this have in doing capability studies? Descriptive Statistics Variable N Mean StdDev short term 30 30.6 2.23 long term 180 33.8 4.44

21. 8-21 Is Process Capable ? The Dynamic Process LSL Short-Term Capability Long-Term Capability Over time, a process tends to shift by approximately 1.5  Short-Term Capability USL

22. 8-22 Is Process Capable ? Measures of Process Performance P p = Specification Range True Process Range = USL - LSL 6s6s P pk = Distance from process average to closest specification limit 1 2 True Process Range = min (USL -x,x - LSL) 3s3s Problem: We are assuming the process has a target that is in the center of the specification range, and that the process is in fact centered on that target. Note: a negative result is possible if the process average is outside specifications Benefits: Optimal values are attained by running exactly between specs. Can (must) be used for 1-sided specifications P p < 1.0  Process Performance is not meeting specs P p = 1.0  Process Performance is marginally meeting specs P p > 1.0  Process Performance is meeting specs P pk < 1.0  Process Performance is not meeting specs P pk = 1.0  Process Performance is marginally meeting specs P pk > 1.0  Process Performance is meeting specs

23. 8-23 Is Process Capable ? Performance vs. Capability These data show that the process, if well controlled can perform much better than it currently is Days Sales Outstanding for 55 Days DSO

24. 8-24 Is Process Capable ? Capability vs. Performance Days Sales Outstanding for 55 Days DSO Process Performance: Total Variation including shifts and drifts (Pp & Ppk) Capability: Only random or short term variability (Cp & Cpk)

25. 8-25 Is Process Capable ? Process Performance Ratios The P-family of indices are computationally the same as the C-family of ‘capability’ indices, but use the observed long-term standard deviation. PMin( X-LSL 3 USL-X 3 pk ,)

26. 8-26 Is Process Capable ? How Does Process Capability Relate to Six Sigma? A goal of Six Sigma is to have: C p = 2.0 C pk = 1.5 Cpk is 1.5 to allow for a 1.5 sigma shift from target. If the six-sigma goal is achieved, the 1.5 drift can occur with a low risk of producing material out of specification. Example: The target viscosity for a plastic is 0.76.  c from the process is 0.01. The lower and upper spec from the process are 0.70 and 0.82, respectively. 0.700.710.720.730.740.750.760.770.780.790.800.810.82 LSL USL T T-1.5  c T+1.5  c

27. 8-27 Is Process Capable ? Six Sigma Goals (Defect Level) The Quality goal of six sigma corresponds to 3.4ppm defect level. For attributes data, the ppm level is calculated by: For variables data, the ppm level is calculated using the normal table.

28. 8-28 Is Process Capable ? Minitab: Process Capability Analysis Is it Normal ? How does the process variation compare to the spec limits ? Is it in control ?

29. 8-29 Is Process Capable ? WARNING!!! Statistical Assumptions Made In Capability Studies Data Comes From a Stable Process 1. Data Comes From a Stable Process  If not, work towards getting the process in control  Don’t despair, you can still make some assumptions about your process in the mean time Data are Normally Distributed 2. Data are Normally Distributed  If not, transform it (ask the instructor ) If Items #1 and #2 aren’t met, results will be misleading

30. 8-30 Is Process Capable ? We will find Process Capability under: l Minitab has many tools that will help you in this area. We will find Process Capability under: Stat>Quality Tools> Capability Sixpack> Normal Open Line1.MTW in the Mintab Datasets Folder and go to the Capability Sixpack Minitab: Process Capability Analysis

31. 8-31 Is Process Capable ? Minitab: Process Capability Analysis Enter the information shown below and select OK

32. 8-32 Is Process Capable ? Minitab: Process Capability Analysis Your output should look like this:

33. 8-33 Is Process Capable ? Example - Capability Study Results l Notice that both C p / C pk and P p / P pk values are given l The data shows that the Capability of the process (C pk ) is 1.32 and the Entitlement (C p ) is 1.35  This shows that the process is on target. Why? l The data also shows the Performance of the process (Ppk) is reasonably capable with a value of 1.26  This indicates the process is in control. Why? l But how good should a process get… Next Slide?

34. 8-34 Is Process Capable ? Process Performance and Capability PpkCp l The Ppk can closely approach the Cp when  The Customer specifications truly reflect customer requirements  The process in under statistical control  The data approximate the normal distribution  The process average is very close to target. Cp l The Cp is like a benchmark or entitlement  Sigma capability is driven primarily by random error (Common Cause Sources of Variation) PpkCpk of 1.5 l We would like Ppk to be very close to a Cpk of 1.5  This would be a process that is performing at a Six-Sigma level

35. 8-35 Is Process Capable ? Test Method Capability Variation Types Variation can be broken down into two types, process and test. These two types are listed and described below: Variation TypeComponent(s) ProcessThe variation due to the: process itself raw materials Sampling ? TestAll other types of variation, including: Sampling ? Sample preparation Between analysts Within analysts Test Equipment Environment Any other variation not part of the process NOTE: Test variation may not be just variation due only to test, it encompasses all sources other than process.

36. 8-36 Is Process Capable ? Total Variability Components Where: (Assumes process is stable) (For Unstable Processes) Can be estimated three ways: 1)Standard Reference Material – Repeated Sampling 2)Half-Blind Technique 3)Gauge R&R (Estimated by subtracting test from total variability)

37. 8-37 Is Process Capable ? Repeated Sampling (SRM) Technique Advantages Long-term estimate of test variability Easy to administrate Can be used to assess accuracy (known value) Can be used to test experimental bias (known value) Can be used as a SPC monitor Disadvantages Only one level of the process is studied People get used to what value "should be"

38. 8-38 Is Process Capable ? Half-Blind Technique Advantage Long-term estimate of test variability Multiple levels of the process are represented by using different samples Disadvantage Hard to administrate Cannot be used to test accuracy

39. 8-39 Is Process Capable ? Gauge R&R Technique Advantages Quick initial estimate of test variability Can be used to assess accuracy (known value) Can be used to test experimental bias (known value) Analyst portion can be estimated Multiple process levels studied Disadvantages Hard to administrate Short-term estimate of test variability Detailed experimental plan needed. Analysis more difficult

40. 8-40 Is Process Capable ? Measures of Test Method Capability Percent of variation due to test method Six Sigma uses the following measures: Percent Gauge R&R Eastman has traditionally used: Precision to Tolerance Ratio

41. 8-41 Is Process Capable ? How Good is Good? … The Debate is On Six Sigma uses the following measures: Eastman has traditionally used: Percent Test Variability: Goal is 20 to 30% Percent Gauge R&R: Less Than 30% P/T Rate: Best Case 10%, Acceptable 30% Problem: 30% Gauge R&R translates to 9% Percent Test Variability (Unrealistic for a lot of tests in Chemical Industry) Note: Initial analysis is showing that processes can be monitored with SPC techniques even when the percent test variability is as high as 50%!

42. 8-42 Is Process Capable ? Resources Allocation?

43. 8-43 Is Process Capable ? Review Indices to measure processes capability  Cp – Goal is 2, Short Term Sigma used in Estimate  Cpk – Goal is 1.5, Short Term Sigma used in Estimate  Pp – Approach Cp, Long Term Sigma used in Estimate  Ppk – Approach Cpk, Long Term Sigma used in Estimate  Note: All of the above are equal for stable processes on target Indices to measure test method capability  Percent Test Variation – Goal is 20 to 30%  Percent Gauge R&R – Less than 30% (Percent Test < 9%)  50% may be more reasonable  P/T Ratio – Best Case 10%, Acceptable at 30%

44. 8-44 Is Process Capable ? Exercise 1.)Your Catapult Team should complete page 11 of the “Catapult Process” handout. Limit yourselves to 30 minutes for this exercise.