Meaning
Dimensional deviations measure the difference between the actual location of a physical feature and its theoretically exact position defined in a design drawing. Calculating true position offset involves taking the square root of the sum of the squares of the X and Y errors. This metric provides a single value that represents the total displacement from the target.
It is the standard method for assessing the quality of hole drilling and component placement in precision manufacturing.
Tolerance Zones
Circular boundaries on a drawing specify the maximum allowable true position offset for a feature. If the center of a drilled hole falls outside this circle, the part is rejected or sent for rework. This method is more accurate than simple plus or minus tolerances because it accounts for the radial nature of the error.
Measurement Technique
Coordinate measuring machines use a probe to identify the physical center of a feature. The software then compares this data to the master CAD model to determine the true position offset. Rapid inspections on the production line use high resolution cameras to perform the same check.
Mechanical Fit
Correct alignment ensures that pins and connectors from different parts will mate without interference. A high true position offset in one component can prevent the final assembly of a multi board system. Controlling this variance is essential for interchangeable parts.
