6. MODULES FOR STATISTICAL PROCESS CAPABILITY, STATISTICAL PROCESS CONTROL AND CONTROL CHART IN GENERAL

Process capability refers to the capability of a process to consistently make a product that meets a customer specified specification tolerance. Capability indices are used to predict the performance of a process by comparing the width of process variation to the width of the specified tolerance. It is used extensively in many industries and only has meaning if the process being studied is stable (in statistical control). Capability indices allow calculations for both short term (Cp and Cpk) and/or long-term (Pp and Ppk) performance for a process whose output is measured using variable data at a specific opportunity for a defect.

Control Chart principles

  • Introduction
  • Composition of control chart
  • Western Electric Rules (WECO)
  • Types of control chart:
  1. Attribute control chart:
  • p-chart
  • np-chart
  • c-chart
  • u-chart
  1. Variable control chart
  • X and S control chart
  • Standard error based X chart
  • Mean range based X control chart
  • R-chart
  • Moving range
  1. Statistical Process Capability study
  • Introduction
  • Why / When to use process capability study?
  • Meaning of within variation Vs Overall variation
  • Graphical representation of process variation
  • Process capability Matrix
  • Capability Matrix: Pp, Ppk, Cp, Cpk, Cm, Cmk, Cg, Cgk.
  • One sided capability Matrix
  • Acceptance criteria for capability Matrix
  • Steps to follow when conducting process capability study
  • Capability study analyze with Minitab software explanations
  • Assessment of capability study after conducting the test rule– Using Minitab software.
  1. Statistical Process Control – SPC in general.
  • Meaning of SPC philosophy, application of SPC principles and its originator.
  • Control chart – meaning focus on variation
  • How do control chart help to avoid defects?
  • Brief history of control chart
  • Cause of variation: a. common cause of variation                                                                                     b. special cause of variation
  • Statistical Process Control – SPC – test rules, graphical representation.
  • Steps in constructing an Average and Range chart (X bar and R)
  1. Select the process characteristics
  2. Establish the sampling plan and rational subgroup size
  3. Gather data/ enter into Minitab software
  4. Establish the overall mean and control limit
  • Calculation of control limits of each of control chart
  • Types of control chart
  1. Attribute and variable control chart in general
  2. Mean range base X control chart
  • Other control chart that might be applicable in practical sense:
  1. Standard error based X chart
  2. R-chart
  3. Moving range e.t.c.

Modules for statistical process capability study,SPC and control chart