Siemens SINUMERIK 840D sl Function Manual page 1849

Modal G code for defining the approach and retraction contour
This G code is only relevant if the approach contour is a quadrant or semicircle. The
approach and retraction direction can be determined as follows:
• G140:
• G141:
• G142:
• G143:
Basic logic functions: Tool Offset (W1)
Function Manual, 11/2006, 6FC5397-0BP10-2BA0
Defining the approach and retraction direction using active tool radius compensation.
((G140 is the initial setting.)
With positive tool radius:
– G41 active → approach from left
– G42 active → approach from right
If no tool radius compensation is active (G40), the response is identical to G143. In
this case, an alarm is not output. If the radius of the active tool is 0, the approach and
retraction side is determined as if the tool radius were positive.
Approach contour from left, or retract to the left.
Approach contour from right, or retract to the right.
Automatic determination of the approach direction, i.e., the contour is approached from
the side where the start point is located, relative to the tangent at the start point of the
following block (P ).
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Note
The tangent at the end point of the preceding block is used accordingly on retraction. If
the end point is not programmed explicitly on retraction, i.e., if it is to be determined
implicitly, G143 is not permitted on retraction, since there is a mutual dependency
between the approach side and the position of the end point. If G143 is programmed in
this case, an alarm is output. The same applies if, when G140 is active, an automatic
switchover to G143 takes place as a result of an inactive tool radius compensation.
Detailed Description
2.4 Tool radius compensation 2D (TRC)
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