Quantifying machine error motions

Several efforts to measure and correct for machine positioning errors derive from error compensation of coordinate measuring machines. The kinematic errors arise because of errors in the creation or assembly of machine components. The errors imparted by the machine to the workpiece depend on the relative motions of those machine components. The errors are measured by master part tracing in which the cutting tool is replaced by a gage, and the workpiece is replaced by a master part, which has substantially tighter tolerances than the machine is capable of producing. The gage is then moved along the surfaces of the master part, following the toolpaths as if the part is being machined. Any deviation in the '0' reading of the gage indicates an error the machine motion would produce. Another class of errors is rotational and the last category of error terms is relative squareness of the axes. Each error term is not a number, but rather a function of the position of the moving axis.