1. CHAPTER 6 Control Charts for Variables
Quality Control
Source: Besterfield, Dale H., Quality Control.

2. Introduction Variation
Axioms or truisms of manufacturing
no two objects are ever made exactly alike
variation
law of nature
height of human beings
weight of fiber-tipped pens
shape of snowflakes
precision instruments will show differences
measure variation versus control variation

3. Introduction Variation
Categories of variation in production
within-piece variation
piece-to-piece variation
time-to-time variation
Sources of variation
equipment
material
environment
operator

4. Introduction Variation
Chance causes of variation
inevitable
numerous reasons
relatively small importance
difficult to detect or identify
Assignable causes of variation
large in magnitude
readily identified

5. Introduction The Control Chart Method
analysis and presentation of quality
indicate when variations are greater than “chance”
visualizing “central tendency”
visualizing “dispersion”
graphical record of the quality
one chart per characteristic
process stability

6. Introduction The Control Chart Method

7. Introduction The Control Chart Method

8. Introduction The Control Chart Method

9. Introduction Objectives of Variable Control Charts
quality improvement
determine process capability
quality decisions
product specifications
production process
recently produced items

10. Control Chart Techniques Introduction
Control charts for the average (“X bar”) and the range (R)
1. Select the quality characteristic
2. Choose the rational subgroup
subgroup size equal to 1 rational ?
subgroup size for destructive testing ?
3. Collect the data
4. Determine the trial central line and control limits
5. Establish the revised central line and control limits
6. Achieve the objective

11. Control Chart Techniques Collect the Data

12. Control Chart Techniques Determine the Trial Central Line and Control Limits
Theoretical formulas
Formulas used in practice based on factors obtained from tables

13. Control Chart Techniques Determine the Trial Central Line and Control Limits

14. Control Chart Techniques Determine the Trial Central Line and Control Limits

15. SME
Introduction to Lean Tooling 18 min