Length of the approach straight line or radius for approach circles (DISR)
● 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 when it is positive.
The resulting straight 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.
Distance of point P2 from the machining plane (DISCL)
If the position of point P
2
is to be specified by an absolute reference on the axis perpendicular
to the circle plane, the value must be programmed in the form DISCL=AC(...).
The following applies for DISCL=0:
● With G340: The whole of the approach motion now only consists of two blocks (P
1
, P
2
and P
3
are combined). The approach contour is formed by P
1
to P
4
.
● With G341: The whole approach contour consists of three blocks (P
2
and P
3
are combined).
If P
0
and P
4
are on the same plane, only two blocks result (infeed movement from P
1
to P
3
is
omitted).
● The point defined by DISCL is monitored to ensure that it is located between P
1
and P
3
, i.e.
the sign must be identical for the component perpendicular to the machining plane in all
motions that possess such a component.
● On detection of a reversal of direction, a tolerance defined by the machine data MD20204
$MC_SAR_CLEARANCE_TOLERANCE is permitted.
Distance of point P1 (retraction plane) from the machining plane (DISRP)
If the position of point P
1
is to be specified by an absolute reference on the axis perpendicular
to the machining plane, the value must be programmed in the form DISRP=AC(...).
If this parameter is not programmed, point P
1
has the same distance to the machining plane as
point P
0
, i.e. the approach straight line P
0
→ P
1
is parallel to the machining plane.
The system checks that the point defined by DISRP lies between P
0
and P
2
, i.e. in all
movements that have a component perpendicular to the machining plane (e.g. infeed
movements, approach movements from P
3
to P
4
), this component must have the same leading
sign. It is not permitted to change direction. An alarm is output if this condition is violated.
On detection of a reversal of direction, a tolerance defined by the machine data MD20204
$MC_SAR_CLEARANCE_TOLERANCE is permitted. However, if P
1
is outside the range
defined by P
0
and P
2
, but the deviation is less than or equal to this tolerance, it is assumed that
P
1
is in the plane defined by P
0
or P
2
.
Programming of the end point
The end point is generally programmed with X... Y... Z...
The programming of the contour end point when approaching differs greatly from that for
retraction. Both cases are therefore treated separately here.
Fundamentals
2.10 Tool radius compensation
NC programming
Programming Manual, 12/2019, 6FC5398-2EP40-0BA0 277
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