Meaning
Statistical ratios provide a numerical representation of how a manufacturing process performs relative to its defined tolerance limits. The capability index acts as a dimensionless number that compares the width of the specification to the natural spread of the process. It assumes the process is under statistical control and follows a normal distribution.
Performance Ratio
High values indicate that the process variation is much smaller than the allowable tolerance range. When a capability index exceeds 1.33, the production line typically produces fewer than sixty-four defects per million opportunities. This level of precision is necessary for high density connectors where mechanical fit is tight.
Specification Limit
Engineers set boundaries based on the thermal and electrical requirements of the assembly.
Deviation Analysis
Calculations for this metric include both the spread of the data and the proximity of the mean to the nearest specification limit. A low capability index suggests that the process is either too variable or is centered too close to a boundary. Adjusting the machinery or changing the raw material source can shift the distribution back toward the center of the specification range.
This analysis helps identify whether a failure is due to a sudden shift in the process mean or a gradual increase in random noise.
