
B–61404E/08
13. FUNCTIONS TO SIMPLIFY
PROGRAMMING
PROGRAMMING
135
The travel distance along the drilling axis varies for G90 and G91 as
follows:
R
Z
G90 (Absolute Command)
R
Z
G91 (Incremental Command)
Point R
Point Z
Point R
Point Z
G73, G74, G76, and G81 to G89 are modal G codes and remain in effect
until canceled. When in effect, the current state is the drilling mode.
Once drilling data is specified in the drilling mode, the data is retained
until modified or canceled.
Specify all necessary drilling data at the beginning of canned cycles; when
canned cycles are being performed, specify data modifications only.
When the tool reaches the bottom of a hole, the tool may be returned to
point R or to the initial level. These operations are specified with G98 and
G99. The following illustrates how the tool moves when G98 or G99 is
specified. Generally, G99 is used for the first drilling operation and G98
is used for the last drilling operation.
The initial level does not change even when drilling is performed in the
G99 mode.
G98(Return to initial level ) G99(Return to point R level)
Initial level
Point R level
D Travel distance along the
drilling axis G90/G91
D Drilling mode
D Return point level
G98/G99