The causes of localization error are datum misalignment error and datum displacement error.
Localization error is associated with the actual measured element to its ideal element with a determined position of the amount of change. Positioning error value is expressed in terms of the width or diameter of the positioning minimum inclusive area. Positioning minimum inclusive area is the same shape as the tolerance zone, according to the position of the ideal element to be measured, inclusive of the actual element to be measured and has the minimum width or diameter of the area. The causes of positioning error are datum non-coincidence error and datum displacement error.
The so-called positioning error, is due to the workpiece in the fixture (or machine tool) positioning is not allowed to cause the processing error. Because of a batch of workpieces, the tool is adjusted position is not moving, that is, the position of the machined surface relative to the positioning reference is unchanged, so the positioning error is the process reference in the processing of the maximum change in the direction of the size of the amount.
Basic information on positioning error
Positioning error is the maximum change in the direction of the process datum of a batch of workpieces in the direction of machining process dimensions, the size of which is an important basis for judging the reasonableness of the fixture positioning program. Positioning error refers to the maximum possible displacement of the process datum in the direction of the process size when the workpiece is positioned in the adjustment method of machining, the calculation method of positioning error can be divided into two according to the principle of one is based on the definition of the positioning error calculation.
In the PTP mode, positioning error is defined as the difference between the control object starting from a certain position A point, after sufficient time to reach the target position B point and the theoretical position, called E after repeated multiple runs E value of the frequency of the roughly normal distribution, there are also the mean value of E e, the standard deviation σ to indicate the positioning error or calibrated with e ± 3 σ, respectively.
Refer to Baidu Encyclopedia-Positioning Error for more details