Meaning
Difference between the actual location of a tool tip and the position commanded by the numerical controller. Every mechanical system possesses some level of machine tool positioning error due to manufacturing tolerances and component wear.
Mechanical Deviation
Inaccuracies in the ball screw pitch or the guide way straightness contribute to the total displacement. As the machine tool positioning error increases, the finished parts may deviate from the nominal dimensions specified in the design. Regular calibration identifies these errors so that they can be corrected through compensation tables in the controller.
Feedrate Impact
Moving the axes at higher speeds often increases the magnitude of the displacement. Dynamic forces during rapid acceleration can exacerbate the machine tool positioning error by inducing vibration or structural deflection. Balancing throughput with precision requires a detailed understanding of how speed affects the location of the tool, especially when the mass of the moving carriage is high enough to strain the drive motor.
Geometric Variance
Errors often change depending on where the tool is located within the working volume. Mapping the machine tool positioning error across the entire envelope ensures that large parts are as accurate as small ones. This mapping is essential for maintaining consistent quality in multi-axis machining operations where the tool path is complex.
