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1、,Understand the difference between Inspection and Variation Reduction (SPC and Process Capability) Review New Process Capability 10-Steps and Scorecard What help do you need from Dell? Questions and Answers,Objectives,Process Capability Summit,Kirk Chi Dell Inc. WWP BPI Business Champion Dell Black
2、Belt ASQ Certified Six Sigma Black Belt ASQ Certified Quality Engineer 7/05/04,Traditional Economic Model of Quality of Conformance,Total cost,Cost due to nonconformance,Cost of quality assurance,“optimal level” of quality,100%,Quality improvement based on Inspection,Modern Economic Model of Quality
3、 of Conformance,Total cost,Cost due to nonconformance,Cost of quality assurance,100%,Quality improvement based on Variation Reduction (SPC/Process Capability),Non-Value Added operations result in: Higher procurement cost of products Higher probability of defects,Improve the Process To Reduce Non-Val
4、ue-Added Operations,Dell,VLRR/PID/CND,Hidden Costs,What is the difference between quality control based on Inspection and Variation Reduction? Inspection refers to the manufacturing operations based on Attribute Data (Pass/Fail). Current manufacturing operations are focused mainly on Pass/Fail inspe
5、ctions. Much of variable data is measured, but the data is converted to attribute data for Pass/Fail inspection.,If you inspect 100%, will your customer experience no failure? If you inspect 100%, and inspect again 100%, and inspect again 100%, will your customer experience no failure? Can you and D
6、ell achieve the reduction of FIR (and VFIR) based on inspection quality control?,We will work together to understand the following points: Even if you inspect 100%, your customer will still experience failures Inspection does not detect the process and product mean shift 100% Inspection does not red
7、uce the variation in your process (and product),Traditional Inspection View,Lower Spec,Upper Spec,no loss,nominal,tolerance,Traditional view: There is no failure as long as a parameter is within specification,New View (Taguchi Loss Function),nominal,tolerance,Failure rate, $,Lower Spec,Upper Spec,no
8、 loss,New View: Products still fail in time even if a parameter is within spec. The probability of failure increases as the parameter shifts away from the mean,nominal,tolerance,Failure rate, $,Lower Spec,Upper Spec,no loss,Where do we want to go?,Critical Process Parameters ( x ),Product Attribute
9、( y(x) ),Metric (Y),VLRR,Sigma Level (Drive for 5),PA PB,1 2 3,Yield,Cpk,Metric,What Measured,Metric (Y),Sigma Level (Drive for 5),VIFIR + 90 D VFIR,Key Message: Only the reduction of process and product parameter variations will lead to the reduction of VFIR,High Cost of Quality,Lowest Cost of Qual
10、ity,Approach to Process Capability,Identifying Cause and Effect,What is Process Capability?,Process Capability is the “Voice of Process” to the “Voice of Customer”. Process Capability study provides valuable insight on how well an existing process is performing with regards to customer requirements
11、(specifications) what needs to be done to improve performance Capability studies enable manufacturers to improve productivity, reduce costs, and enhance their strategic advantage over competitors.,Process Stability Before Capability,Control of a process must be achieved first, before any attempt is
12、made to measure capability or estimate the percentage of nonconforming product. When a process is stable, it is repeatable, well-defined, and predictable.,You can predict the outcome only if the process is stable,time,PREDICTABLE,?,UNPREDECTIBLE,Process Stability:Statistical Process Control,Statisti
13、cal Process Control (SPC),A process output is considered stable when it consists of only common-cause variation.,Sources of Variation in Production Processes,Materials,Tools,Operators,Methods,Measurement Instruments,Human Inspection Performance,Environment,Machines,INPUTS,PROCESS,OUTPUTS,Common Caus
14、es,Special Causes,Two Fundamental Management Mistakes,Treating as a special cause any fault, complaint, mistake, breakdown, accident or shortage when it actually is due to common causes Attributing to common causes any fault, complaint, mistake, breakdown, accident or shortage when it actually is du
15、e to a special cause,Control Chart,Focuses attention on detecting and monitoring process variation over time Distinguishes special from common causes of variation Serves as a tool for on-going control Provides a common language for discussion process performance,* * * * *,* *,Commonly Used Control C
16、harts,Variables data x-bar and R-charts x-bar and s-charts Charts for individuals (x-charts) Attribute data For “defectives” (p-chart, np-chart) For “defects” (c-chart, u-chart),Statistical Process Control (SPC),A methodology for monitoring a process to identify special causes of variation and signa
17、l the need to take corrective action when appropriate,Shift in Process Average,Identifying Potential Shifts,Cycles,Trend,Quantitative Comparison ofTraditional Inspection vs. Control Chart,Review of Variable-Data Control Charts,+3,-3,+1,+2,-1,-2, +/- 1 = 68% +/- 2 = 95% +/- 3 = 99.73%,Individual meas
18、urement distribution,SPC Control Limits,x-bar,x-bar+3X-bar,x-bar = /,UCL (Upper Control Limit) = X(double bar) + 3X-bar LCL (Lower Control Limit) = X(double bar) - 3X-bar,Sample mean distribution,Distribution of X vs. Distribution of Sample Means (X-bar),+3,-3,x-bar,x-bar+3X-bar,x-bar = /,Individual
19、 measurement distribution,Sample mean distribution,There is no relationship. Spec limits are determined by engineering based on customer requirements Control limits are determined by the common-cause variation in the process Spec limits are typically wider than control limits,Spec Limit vs. Control
20、Limit,+3,-3,Control Chart: Example: Control chart is monitored by UCL and LCL. (Note: USL and UCL do not have any relation.),USL,LSL,x-bar,x-bar+3X-bar,UCL,LCL,*If =2 for Inspection of individual parts, of subgroup size of 4 samples = 1.,Why Control Charts Are Better Than Inspection?,+3,-3,Inspectio
21、n: Example: One part is checked each hour. One part is checked every 20. Part passes the inspection if the part measurement is within spec.,USL,LSL,*Assumption: spec limit lis +/-3 sigma.,+3,-3,What happens to Inspection if process mean shifts 3 sigma?,USL,LSL,Anything above USL are rejected.,50%,Be
22、cause half of the pieces are still within spec, there is 50% chance of selecting such a part and mistakenly deciding to continue running this modified process.,What happens to Control Chart if process mean shifts 3sigma?,x-bar,UCL,LCL,*If =2 for Inspection of individual parts, of subgroup size of 4
23、samples = 1.,99.865%,Only 0.135% of the subgroup averages would fall within the control limits. Conversely, 99.865% will be above UCL. There is almost 100% chance this shift in the process mean will be detected.,+3 shift,Power of X-bar Chart to Detect Process Changes,Producers Risk (Alpha error): Re
24、jecting a good part Alpha error measure the probability of rejecting good parts in the factory. Consumers Risk (Beta error): Shipping bad partsBeta error measures the probability of shipping bad parts to customers,(1-),Probability of detecting a process shift is higher with larger n, i.e. Beta error
25、 (consumers risk) decreases as n increases.,Process Capability,Process Capability is defined as the ability of a process to satisfy customer expectations. Because the specification limits are assumed to reflect customer desires, capability measures are said to relate the “Voice of the Process” to th
26、e “Voice of the Customer”,Process Capability,Process Capability Index,Cp =,USL - LSL 6s,Cpl, Cpu ,USL - m 3s,Cpl =,m - LSL 3s,Cpk = min,Cpu =,Process Capability,Process Capability Index, Cp Cp 1.33, Capable Cp = 1.00 1.33, Capable with tight control Cp 1.00, Incapable,Process Variation,Specification
27、s,Process Capability,Cp = 1 and Cpk = 1,LSL Target USL,LSL Target USL,Cp = 2 and Cpk = 1,LSL Target USL,Cp = 2 and Cpk = 0,New Process Capability 10-Steps,1. Characterize the entire manufacturing process. Process Map the entire manufacturing operations from the beginning to the end. Later when the c
28、ritical parameters are identified, locate which processes are aligned with the critical parameters.,Initiate an attribute control chart (P-chart) on Rolling-Through-Put Yield. If a supplier is sensitive to sharing the yield data, use the coded data. The goal is to monitor the stability of RTY. The g
29、oal of control chart is to identify any special-causes. Identify the root causes and take corrective actions immediately for any out-of-control points. Does the supplier have the documented process on P-chart, business owner, and action steps for correcting out-of-control points? After CPKs of criti
30、cal characteristics are improved, check if there is any impact to RTY.,3. Identify the critical parameters. This is the most important step. Critical parameters can be identified in many different ways. Critical parameters should be tied to customer experience. Critical parameters can be both Proces
31、s and Product characteristics. One way to identify the critical parameters is to analyze the nonconforming defectives (fall outs) from supplier manufacturing line, customer manufacturing line, and customer fields. Pareto, FMEA and Cause-and-Effect diagram are common tools to use for the analysis.,3.
32、 Identify the critical parameters (continued) Another way of identifying critical parameters is to get Engineering (Design and New Product Introduction) engaged to identify key critical Product characteristics that impact customer experience. Identifying both Process and Product critical parameters
33、is desirable. Identifying the critical parameters from both defective analysis and engineering involvement is desirable.,Review the specifications of the critical characteristics. Specifications should be defined based on customer requirements. Does the supplier have the process to define specs base
34、d on engineering and tolerance analyses? Or does the supplier define some specs arbitrarily? Does the supplier have the process to tighten up specs or do they maintain the same spec always? The value of process capability will be dependent on the specifications. Quite often, very unreasonably high C
35、PKs are reported because of very wide spec ranges. If the spec is too wide, products may pass through suppliers manufacturing process, but products will not conform to customers expectations. Define the required CPKs for the critical characteristics.,5. Conduct Measurement System Analysis. The goal
36、of running Gage R builds support for solutions Focuses the team on causes, not symptoms,Effect,Cause,FMEA What is it?,Failure mode effects analysis (FMEA): A technique to identify, define, and eliminate known and/or potential failures, problems, errors, and so on from the system, design, process, an
37、d/or service before they reach the customer Provide documentation for safety and liability issues Fulfill customer and legal requirements Identify, prioritize, and reduce potential failure modes Manage and quantify risk Rank order potential design and process deficiencies Establish priorities for co
38、ntainment, corrective, and preventive actions Improve the reliability and safety of products and services System / Design FMEA Focus on a product prior to release Decrease design deficiencies and increase design robustness Process / Service FMEA Focus on a series of steps (production or administrati
39、ve) Increase process robustness and identify high risk failure steps and points of control Tool for prioritization, prevention, and correction,Define Failure Modes,A description of the manner in which a failure occurs A functional requirement expressed negatively Absence of function: “Does not ” Doe
40、s not resolve customer complaint Does not paint fenders Function done poorly, inadequately, or incompletely Should be expressed directionally or in actionable terms Incomplete assembly Excessive chrome,Missing Wrong invoice Damaged Hot surface Bent pin Undersize Cracked bezel Melted plastic Shorted
41、circuit Wrong capacitor Warped board Open circuit Surface finish Discolored Corroded Loud fan,Tight insertion Creased Scratch Wrong driver Out of position Loose Dent Low voltage Ejection partial High resistance Frayed cable Brittle Omitted Tight fit Missing pixel Misaligned,Identify Effects,Identify
42、 the effect of the failure mode on the following: Next operation Downstream users Ultimate customer or consumer Regulatory agencies,Identify Causes,Identify the causes of the failure mode Use Cause and Effect Analysis: the 4MEP model Be sure the causes address the failure mode Stay on-level: avoid i
43、nappropriate deep dives,Define Current Controls,Avoid wishful thinking, especially with regard to current controls Controls exist to detect causes Audits and inspections are not effective control methods Inspections are, at best, a method of detection not control,Statistical process control chart Sa
44、mpling Audits and Logs Inspections Run and trend charts Pre-control charts Capability studies Military standards Operating procedures Checklists Setup checks,Send aheads Laboratory tests Pilot runs Simulation Testing equipment Prototype testing Verification testing Tolerance studies On-line reliabil
45、ity testing Documentation Formulas Prints and specifications,Measure: Severity Scale,Directly related to failure mode and effects Ratings of “10 and 9” are reserved for hazardous situations and are obviously addressed immediately (special cause),Measure: Occurrence and Detection Scales,Directly rela
46、ted to cause Over the design life of the product before any additional process controls are applied,Directly related to controls Assume a failure has occurred to determine the detection rating The scale is reversed,Measure: Assign Ratings and Calculate Risk,Severity is related to failure mode and ef
47、fects Severity can be assign a rating based on either the failure mode, the worst effect, or each effect separately Just make sure to stay consistent throughout the entire FMEA analysis,Measures of Risk,Approaches to Prioritize Risk Address severity ratings of 9 or 10 immediately Focus on highest RP
48、N first Use Pareto method Can be applied to both S*O and RPN Use risk thresholds RPNs greater than 50 Define categories of action: critical / high / minor,Manufacturing Process Capability,NPI Product Capability,Manufacturing Process,Identify Product Critical Parameters during Design and Qualification phases. Implement SPC and assess Cp + Cpk in NPI phase. Use the info to make Mass Product Decision.,Identify Process Critical Parameters that are associated with supplier yield failures, Dell line failures, and Dell field failures during mass production.,Implement SPC and Capability Analy