Siemens SINUMERIK 840D sl Programming Manual page 303

Selecting the approach and retraction direction
Use the tool radius compensation (G140, basic setting) to determine the approach and
retraction direction with positive tool radius:
• G41 active → approach from left
• G42 active → approach from right
G141, G142 and G143 provide further approach options.
The G codes are only significant when the approach contour is a quadrant or a semicircle.
Motion steps between start point and end point (G340 and G341).
The approach characteristic from P
In cases which include the position of the active plane G17 to G19 (circular plane, helical axis,
infeed motion perpendicular to the active plane), any active rotating FRAME is taken into
account.
Length of the approach straight line or radius for approach circles (DISR) (see figure
"Selecting approach/retraction contour")
• Approach/retract with straight lines
DISR specifies the distance of the cutter edge from the starting point of the contour, i.e.
the length of the straight line when TRC is active is the sum of the tool radius and the
programmed value of DISR. The tool radius is only taken into account if it is positive.
The resultant line length must be positive, i.e. negative values for DISR are allowed
provided that the absolute value of DISR is less than the tool radius.
• Approach/retract with circles
DISR specifies the radius of the tool center point path. If TRC is activated, a circle is
produced with a radius that results in the tool center point path with the programmed
radius.
Fundamentals
Programming Manual, 09/2011, 6FC5398-1BP40-2BA0
10.4 Smooth approach and retraction
to P is shown in the figure below:
0 4
Tool radius compensation
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