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Repeatibility, Accuracy, Resolution
The meanings of Repeatibily, Accuracy, and Resolution are important to understand from a machine alignment and calibration standpoint.
This is because specifications for CNC Machines use this terminology so if we perform those tasks we must know what they mean in order to meet those specifications.
Repeatibility is the is difference among a group of measurements taken on the same position.
Assume that cluster of repeatibility dots on the below target are Marksmen shots at the target.
The tightness of the pattern of the shots on the target is the measure of repeatibility.
Accuracy is how closely the average of the measurements come to the target dimension.
In the target example, this would be how close the average of the pattern of shots come to the bullseye.
This is different than repeatibility which is concerned with how close the measurenents come to each other.
Resolution is the smallest increment of scale.
In the target example, resolution is the distance between the rings of the target.
CNC Machines commonly have a 0.0001" or 0.001mm resolution for linear axes and 0.001 degrees for rotary axes.
Typical dial indicators have resolutions of 0.001", 0.0005", 0.0001", 0.001mm or less.
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