Siemens SIMATIC S5 Manual page 58

A statement containing G44 causes a tool length offset in a reverse direction by the length
specified in the machine data (=> Section 4.3.8 "Tool Length Offset"). This occurs each time
the function is executed.
Example
The tip of a tool with a basic length of 40 mm must approach coordinate O. During each
machining operation, the tool is reduced in length by 5 mm, The tip of the tool is at posi-
tion -65 mm before the first machining operation. The home position of the tool holder is -
105 mm.
The following must be programmed:
in the machine data: tool length offset = +5mm
in the machining program: N1 OXOFI 000
N15G44X-65F2000
This means that the tip of the tool is at the same position following each machining operation
In this example, the tool holder does not return to the home position when it is retracted.
If the tool holder must always return to the basic position when it is retracted (e.g. owing to inter-
locks), you should set the reference point at this position, In a reference point approach, or with
G74 in an automatic program, the tool holder always returns to the same position both with or
without offsets. However, the corrected value (coordinate of the tip of the tool) is displayed as
the actua~ value.
The machining program is then as follows:
N1 OXOF1 000
N15G74
N20G44
Machining Programs and their Structure
2-41