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Statistical Process Control Concepts

Statistical Process Control Concepts

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Statistical Process Control Concepts

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  1. Statistical Process Control Concepts Hampton Roads Section, ASQ June 15, 2011 Scott Rutherford Master Black Belt, Norfolk Naval Shipyard

  2. Learning Objectives • Understand the three general areas of SPC • Understand the proper use of SPC in your Quality program • Understand SPC’s pitfalls and success factors

  3. History • 1920’s: “Created” by Walter Shewhart for Bell Labs • WWII: W. Edwards Deming applies concepts to munitions manufacturing • After WWII: Deming teaches SPC to Japanese to help build back their industrial base • 1988: SPC applied to software industry becomes CMMI (Causal Maturity Model Integration)

  4. Shewhart’s original concept • Physical process data is usually NOT normally distributed • Processes either display: • Controlled variation that is natural to the process • Uncontrolled variation that is generated from outside the “process causal system” (assignable cause) • Attacking process variation produces a product that consistently conforms to specifications

  5. Three Elements of SPC • Understanding the Process • Understanding the Causes of Variation • Eliminating the sources of Assignable (Special) Cause variation

  6. Techniques for Understanding the Process • Process Mapping • Determine Measure of Quality • From customer’s perspective • Usually an output measure • Determine Measure of Quality Predictor • What In-process Measure is the most reliable predictor of the Quality Measure? • Measure the Predictor • Control Charts / Run Charts

  7. Understanding Causes of Variation • Root Cause Analysis - Reactive • Causal Mapping – 5 Whys • Switch Theory • Human Factors Analysis and Classification System (HFACS) – Swiss Cheese Analysis • Kepner series (Tregoe, Fourie) • Fishbone • Others (Ford Global 8D, DuPont, etc.) • Failure Modes & Effects Analysis (FMEA) - Proactive

  8. Eliminating Special Cause Variation • Identification • Control Chart monitoring • Control Chart Analysis (“rules”) • Response • Immediate Action (Control or Reaction Plan) – Getting back to the norm • Short-term actions – Preventing reoccurrence • Long-term actions – Eliminating cause

  9. Preventing Reoccurrence • Immediate Knowledge capture • Start of Work / Shift briefings • Verbal / “Pen & Ink” Procedure changes • Training • Periodic self-assessments • Proper monitoring of the process

  10. Eliminating Reoccurrence • Lean Tools • 5S • Standard Work codification • Mistake-proofing • FMEA Analysis • Process Knowledge Use • R&D • Next generation design • Behavioral / Cultural Change

  11. Why SPC Initiatives often Fail • “It’s All about the charts” • “More important to train” • “Don’t have time to figure out the source, get back to work!” • “The control plan should have caught that!” • “Sort out the bad to get enough good product to sell” • “We have the time to do it over, but not enough time to do it right the first time”

  12. SPC succeeds when: • Supervisors empowering front line workers in monitoring control charts and executing control plans • There is a dedicated workforce to spend the time to analyze sources of variation • Eliminating variation is a strategic initiative

  13. What other comments or questions do you have? scott.rutherford@navy.mil srlean6@gmail.com