CONTROL CHARTS 1. These charts are used for process control. Statistical device used for control of repetitive process. 2. Developed by Dr. W.A. Shewart. Variability does exist in all repetitive processes. Variation due to chance causes. Variation due to assignable causes. Variation in any manufactured product is INEVITABLE

Statistical Tools:- Frequency distribution Control chart Acceptance sampling Analysis of data   Benefits:- Efficiency Reduction of Scrap Easy detection of fault Quality improvement Adherence to specification Increase output

Chance cause – Inevitable. Difficult to trace Chance cause – Inevitable. Difficult to trace. Due to inherent characteristic of process or machine. Assignable cause – Can be traced & detected. Due to Difference among workers. Differences among machines. Differences in each of these over time. Differences in their relationships

CONTROL CHARTS X & R charts (measurement of quality characteristic) p chart (chart for fraction defectives or rejected) c chart (chart for no. of defects/units) or non-conformities Construction of chart :- Choice of variable (likely to reduce cost) Basis of subgroup Size of subgroup Size of subgroup (4 or 5) Frequency of sampling Control limits (+ 3 σ) 

X BAR & R CHARTS

PROCESS CAPABILITY

PROCESS CONTROL VS SPECS

ATTRIBUTE CONTROL CHART

P CHART

C CHART

CONTROL CHART PATTERN