Control limits ensure stability and consistency in global organizations' improvement efforts, embodying enduring statistical principles for process excellence.
Types of Control Limits
Upper Control Limit
UCL sets max variation; exceeding it signals out-of-control data.
Lower Control Limit
LCL sets min variation; data below it signal process issues.
Importance of Control Limits
Early Detection of Variations
Special Cause Variation
Unpredictable variations from expected process require immediate corrective action.
Common Cause Variation
Common cause variations are natural, expected, within control limits in processes.
Control Limits vs Specification Limits
Category: Purpose and Focus
Control Limits:
Specification Limits:
Monitor process stability, distinguish variations.
Define acceptable product characteristics.
Category: Variability & Calculation Method
Control Limits:
Calculated from process data, maintain stability.
Specification Limits:
Determined by customer needs, design specifications.
Control Limits:
Specification Limits:
Integral part of control charts, monitor process performance.
Incorporated into quality specifications, ensure acceptability.