Positioning accuracy

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The positioning accuracy describes a property of moving mechanical systems, mainly in machine tools and positioning systems . It is a measure of how precisely a desired position can be approached or reached, and thus for the manufacturing accuracy that can be achieved with the machine.

A method for checking the positioning accuracy or for assessing the controller settings of a CNC machine tool is the circularity test .

The position uncertainty is a parameter for the positioning accuracy . This indicates how large the deviation of the actual position from the target position is in the direction of movement. The total permissible deviation of a movement axis is known as the position tolerance.

To determine the position uncertainty target positions are each of positive ( ) and negative ( started up) direction, and so the actual positions and measured.

The positional uncertainty of a movement axis is made up of three parts:


  • the systematic deviation at location x i from the target value:

  • the reversal range at location x i , which indicates the difference in position by approaching from positive and negative directions: