Six Sigma Quality: Analysis and Improvement Techniques

Analyze and Improve/Implement Phase: Tools and Methods

  • Design of Experiments (DOE): A statistical method to estimate effects of independent variables (KPIVs) on dependent variables (KPOVs).
  • Key Tools:
    • Analysis of Single Factor Multi-Level Experiments
    • Completely Randomized Design
    • Multiple Comparison Tests
    • Factorial Design
    • Root Cause Analysis
    • Taguchi Method and Orthogonal Designs
    • A3 Problem Solving
    • Lean Six Sigma Tools
    • Value Stream Mapping
    • Theory of Constraints
    • Poka Yoke

DOE and Factorial Designs

  • Purpose: To shift process averages to desired locations and reduce variability by optimizing input parameters.
  • Application: Effective in Six Sigma projects aimed at optimizing input parameters.
  • Limitations: Not ideal for Lean projects focused on waste elimination.

Improve Phase Process Flow

  • Cost-Benefit Analysis: Evaluate solutions based on expected costs and benefits.
  • Selecting Solutions: Use DOE and response surface optimization to identify the best approach.
  • Assessing Risks: Utilize FMEA to identify risks linked to solutions and plan preventive actions.
  • Piloting: Test solutions on a small scale to evaluate effectiveness.
  • Implementation: Full-scale plan development for change management.

DOE Techniques

  • Example:
    • A $2^4$ factorial experiment has:
    • Total of 16 trials (4 factors with 2 levels each).
    • A $2^{(4-1)}$ fractional factorial experiment:
    • Only utilizes 8 out of 16 combinations for initial screenings.

DOE Terminology

  • Factor: Independent variable (KPIV)
  • Level: Specific value within a factor (e.g., low/high)
  • Response: Dependent variable (KPOV)
  • Main Effects Plot: Visualization of main effects for analysis
  • Confounding: Occurs when two factors are interrelated, complicating effect measurement.
  • Blocks and Replicates: Enhance experiment precision and analyze variation respectively.

General Steps for DOE

  1. Define Objective
  2. Select Response (KPOVs)
  3. Select Factors (KPIVs)
  4. Establish Factor Levels
  5. Choose Experimental Design
  6. Execute Experiment & Collect Data
  7. Analyze Data & Draw Conclusions
  8. Perform Confirmation Run

A3 Problem Solving

  • Purpose: A structured visual tool for problem solving, summarizing conditions and actions.
  • Steps:
    1. Problem Identification
    2. Current Condition Analysis
    3. Goal Setting
    4. Root Cause Identification
    5. Developing Countermeasures
    6. Implement Solutions
    7. Verify Results
    8. Standardize & Share Success

Lean Six Sigma Process Flow

  • Define: Team ground rules, VOC analysis, KPOVs, and CTQs.
  • Measure: Current process mapping, data collection, graphing.
  • Analyze: Verify KPIVs and link them to KPOVs.
  • Improve/Implement: Develop solutions, future state mapping, pilot studies.
  • Control: Process control plans, recognition, full implementation.

Control Phase Steps

  1. Establish a control plan for monitoring processes.
  2. Reward and recognize team contributions.
  3. Finalize the cost-benefit analysis.
  4. Full implementation through a comprehensive checklist.
  5. Continuous monitoring and improvement strategies.