This post will introduce you some knowledge of cnc router control system, it is SIEMENS 808D Control System.

Plane selection: G17 to G19

Functionality

To assign, for example, tool radius and tool length compensations, a plane with two axes is selected from the three axes X, Y and Z. In this plane, you can activate a tool radius compensation.

For drill and cutter, the length compensation (length1) is assigned to the axis standing vertically on the selected plane. It is also possible to use a 3-dimensional length compensation for special cases.

Another influence of plane selection is described with the appropriate functions (e.g. Section “Support for the contour definition programming”).

The individual planes are also used to define the direction of rotation of the circle for the circular interpolation CW or CCW. In the plane in which the circle is traversed, the abscissa and the ordinate are designed and thus also the direction of rotation of the circle. Circles can also be traversed in a plane other than that of the currently active.
The following plane and axis assignments are possible:

Programming example
N10 G17 T… D… M… ; X/Y plane selected
N20 … X… Y… Z… ; tool length compensation (length1) in Z axis