Probes for CNC machine tools, as every measurement device, have accuracy limited by\nrandom errors and by systematic errors. Random errors of these probes are described by a parameter\ncalled unidirectional repeatability. Manufacturers of probes for CNC machine tools usually specify\nonly this parameter, while parameters describing systematic errors of the probes, such as pre-travel\nvariation or triggering radius variation, are used rarely. Systematic errors of the probes, linked to the\ndifferences in pre-travel values for different measurement directions, can be corrected or compensated,\nbut it is not a widely used procedure. In this paper, the share of systematic errors and random errors\nin total error of exemplary probes are determined. In the case of simple, kinematic probes, systematic\nerrors are much greater than random errors, so compensation would significantly reduce the probing\nerror. Moreover, it shows that in the case of kinematic probes commonly specified unidirectional\nrepeatability is significantly better than 2D performance. However, in the case of more precise\nstrain-gauge probe systematic errors are of the same order as random errors, which means that errors\ncorrection or compensation, in this case, would not yield any significant benefits.
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