Units and Active Plane Selection Group

Units Group, G70, G71

Normally NC programs can be written in either inch units or mm units. It is necessary to specify the units with a G code. G70 stands for programming in inch units while G71 stands for programming in mm units. A given program should be written only in either inch or mm units. Hence only one of the two codes should be present in one program. Sometimes in Fanuc controls normally G20 and G21 are used for the units in place of G70 and G71.

Active Plane Selection Group, G17, G18, G19

Some G-codes in the NC control are expected to work only in a plane rather than in the 3D space. This set of codes is used for selecting the active plane.

Figure 6: Plane Selection for Vertical Axis Milling Machines

G17     XY Plane selection

G18     XZ Plane selection

G19     YZ Plane selection