Siemens SIMATIC S5 Manual page 57

Machining Programs and their Structure
If the tool length offsets implemented by a machining program during its execution are not reset
with G40 ("clear tool length offset"), they are retained on completion of the machining program.
The offset implemented in the machining program can then only be cleared using modeBA16
("tool length offset off"). However, a basic tool length offset activatedbyBA15 ("tool length off-
set") is also deleted. If a new tool offset is activated by BA15 when a machining program is
completed, the cumulative tool length offset achieved during the machining program is no longer
effective,
Tool change
BA 15; 10Omm, forwards
Machining program start
Machining program end
Tool change
BA 15; 200mm, forwards
* In the machine data record: tool length offset =lOmm
Fig. 2/1 9 Tool length offset
A statement containing G40 switches off all the active, positive or negative tool length offsets in
this machining program. This also applies to subroutines. The G-function G40 does not affect the
tool length offset set with mode BA15 ("tool length offset on").
G43: positive tool length offset on
A statement containing G43 causes a tool length offset in a forwards direction by the length
specified in the machine data (=> Section 4.3.8 "Tool Length Offset"). This occurs each time
the function is executed.
2 - 4 0
Tool length
offset
BA 15/16
1 OOmm
-1 Omm
-20mm
Total
o
1 OOmm
90mm *
o
I