
B-63322EN/03 NC FUNCTIONS 13.FUNCTIONS TO SIMPLIFY PROGRAMMING
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- Travel distance along the drilling axis G90/G91
The travel distance along the drilling axis varies for G90 and G91 as
follows :
Z=0
R
Z
Point R
Point Z
G90 (Absolute Command)
R
Z
G91 (Incremental Command)
Point R
Point Z
- Drilling mode
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.
- Return point level G98/G99
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.