Statistical process control (SPC): Quality Tools

When to Use Statistical Techniques

Statistical techniques are (to be identified during APQP) used when necessary. Instances in which statistical techniques can be used are:
  1. New or existing product as per customer requirement
  2. The customer complains about the product and demands statistical verification, provided the complaint is properly acknowledged by the appropriate parties.
  3. Regular monitoring and control of processes.

Control charts for variables

The appropriate types of statistical techniques should be used and can be one or more of the following :
  1. Average and Range Charts
  2. Process Capability Chart

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Production Part Approval Process (PPAP)

List of PPAP 18 Documents | PPAP Documents Requirements

  1. Design Records
  2. Authorized Engineering Change Documents
  3. Customer Engineering Approval
  4. Design Failure Modes and Effects Analysis (DFMEA)
  5. Process Flow Diagram
  6. Process Failure Modes and Effects Analysis (PFMEA)
  7. Control Plan
  8. Measurement Systems Analysis (MSA)
  9. Dimensional Results
  10. Records of Material / Performance Test Results
  11. Initial Process Studies
  12. Qualified Laboratory Documentation
  13. Appearance Approval Report (AAR)
  14. Sample Production Parts
  15. Master Sample
  16. Checking Aids
  17. Customer-Specific Requirements
  18. Part Submission Warrant (PSW)

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APQP 23 Elements

List of APQP 23 Elements:

  1. Customer order
  2. Customer specifications
  3. Ability Appearance
  4. Design FMEA
  5. Design Review
  6. Design Verification plan
  7. Quality Planning
  8. Inspection Method, Inspection Equipment & Tools
  9. Inspection Plan / Control plan for Prototype item
  10. Prototype item's production & inspection
  11. Design - Drawing & Specifications
  12. Confirmation of manufacturing feasibility
  13. Process flow chart & Mass Production Layout
  14. Process FMEA
  15. Inspection Equipment Capability
  16. Pre-production / Pre-release control plan
  17. Process Instructions
  18. Logistics Concept includes Packaging materials
  19. Production First Trial Run
  20. Mass Production Inspection Plan / Control plan
  21. Initial Process Capability Study
  22. Technical tests on Production Items
  23. Initial Sampling Inspection

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Advanced Product Quality Planning (APQP)

What is APQP?

Advanced product quality planning (APQP) is consistent methodology proposed to accompanies the development of product to ensure that a product satisfies the customer's requirements on time.

Advanced product quality planning (APQP) Phases:

  1. Plan and define Program
  2. Product Design and Development
  3. Process Design and Development
  4. Product and Process Validation
  5. Feedback, corrective action and Continual improvement

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Failure Mode and Effects Analysis (FMEA)

What is Failure mode and effects analysis (FMEA)?

Failure mode and effects analysis(FMEA): A process which use a multidisciplinary approach to recognize and evaluate the potential failure of a product/process and the effects of that failure. This process will be followed by the identification of preventive action that could eliminate or reduce the chance of the potential failure occurring.

Type of FMEA

  1. Design FMEA
  2. Process FMEA or Product FMEA
  3. System FMEA
  4. Service FMEA
  5. Software FMEA.

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Measurement System Analysis (MSA)

What is Measurement system analysis (MSA)?

Measurement system analysis(MSA): A process where statistical studies are being conducted to analyse the variation present in the results of each type of measuring and testing equipment system.

Five characterized / Statistical properties in Measurement System Analysis:

  1. Bias
  2. Linearity
  3. Stability
  4. Repeatability
  5. Reproducibility

Measurement System Adequacy

A. Measurement System Analysis Checklist
B. Intial Study of MSA: Test-retest study
C. The Gage Repeatability and Reproducibility study

3 Steps of Gage Repeatability and Reproducibility study

First Step : Collection of Date
Second Step: Performing Calculation
Third Step : Analyzing Results

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7 Quality tools (seven basic tools of quality): Quality Management tools


  1. Cause and effect diagram
  2. Check sheet
  3. Control Charts
  4. Histogram
  5. Pareto Chart
  6. Scatter Diagram / Scatter chart
  7. Flow Charts
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How to reduce manufacturing cost? - Useful 13 ideas

13 Useful Ideas for Manufacturing Cost Reduction

  1. Manufacturing Design or Optimization
  2. Raw material Cost
  3. Labor Cost
  4. Manufacturing Overhead Cost
  5. Investment in manufacturing (Installation & maintaining machinery)
  6. Reduce Rework
  7. Waste Reduction
  8. Quality cost management
  9. Arrange Quantity center
  10. Analysis production data & processes
  11. Maximum Utilize resources
  12. Reduce internal transportation
  13. Miscellaneous
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Quality Costs: Costs of Quality or Total Quality costs

Quality Costs - Elements

  1. Appraisal Costs - Cost of Quality
  2. Preventive Costs - Cost of Quality
  3. Internal Failure Costs - Cost of Loss Control
  4. External Failure Costs - Cost of Loss Control

Quality Costs Formula:

1) Total Quality Cost = Cost of Poor Quality + Cost of Quality or Cost of Loss of Control + Cost of Control
2) Cost of Poor Quality = Internal Failure Costs (IFC) + External Failure Costs (EFC)
3)Cost of Quality = Appraisal Costs (AC) + Prevention Costs (PC)

Best Quote:
Cost Information does not solve any quality problems, nor it suggest specific solutions, problems are solved by tracking the cause of quality deficiency.

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Process Capability: Process capability Study, index and Analysis

What is process capability?

Process capability Measure of how capable the process is to meet customer requirements; compares process limits to tolerance limits. It can be appearances at short term and long term performance of a process with regard to customer satisfactions. It is looks long term performance level of the progression after it had been conveyed under statistical control....

What is process capability study?

Process capability study is a systematic procedure that uses graphic techniques to detect and reduce the unnatural causes of variation until an accurate of statistical control is reached. Once study is completed, you will identify the natural variability of the process. The study provides a model to realize how the process is operating relative to the specification....
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