Inch/Metric Input Designation (G20, G21) - Siemens Sinumerik 802D sl Programming Manual

Movement Control Commands
3.2 Determining the coordinate value input modes
3.2.3

Inch/metric input designation (G20, G21)

It is possible to select the dimension unit for the input data between "mm" and
"inches". For this selection, the following G codes are used.
Table 3-5
G20 (G70, G code syst. C)
G21 (G71, G code syst. C)
Command format
G20 (G70) and G21 (G71) should be specified at the beginning of a program in a
block without other commands. When the G code which selects the input dimen-
sion unit is executed, the following values are processed in the selected dimension
unit: subsequent programs, offset amount, a part of parameters, a part of manual
operation, and display.
Supplements to the dimension unit designation commands
A parameter is used to select "inch/mm". Therefore, the state when the power is
turned ON is determined by the setting for this parameter.
If the dimension unit system should be switched over during the execution of a pro-
gram, the tool position offset and nose R offset function must be canceled before
the switching over of the dimension unit system.
After switching over the dimension unit system between G20 and G21, the follo-
wing processing must be accomplished.
S Set the coordinate system before specifying axis move commands.
S If position data are displayed in a workpiece coordinate system, or when an
external position data display unit is used, reset the present position data to "0".
The tool offset amounts stored in memory are treated in a different manner bet-
ween the G20 and G21 modes.
Table 3-6
Stored offset amount
150000
3-70
Dimension unit selection G codes
G code
Input in "inch" system
Input in "mm" system
Tool offset amounts in G20 (G70) and G21 (G71) modes
(inch system) mode
1.5000 inch
SINUMERIK 802D sl/840D sl840D/840Di sl/840Di/810D ISO Turning - - 04.07 Edition
Function
06
06
in the G20 (G70)
15.000 mm
© SIEMENS AG 2007 All rights reserved
04.07
Group
in the G21 (G70)
(mm system) mode