Siemens SINUMERIK 840D Programming Manual page 270

Turning Cycles
4
4.10 Extended stock removal cycle - CYCLE950 (SW 5.3 and later)
_TOL1 (blank tolerance)
Since a blank does not always correspond exactly to the
blank definition when it is cast or forged for example, it
makes sense not to travel to the blank contour with G0
for roughing and for the infeed but to activate G1 shortly
beforehand to compensate for any tolerances.
Parameter _TOL1 defines the distance from the blank
at which G1 becomes active.
Traversing is started with G1 at this incremental amount
before the blank. If the parameter is not programmed, it
has the value 1 mm.
Further notes
Contour definition
Unlike CYCLE95, one block that contains a link to
the current plane is sufficient for contour
programming.
For further details of contour definition, see
CYCLE95.
Blank contour definition
A blank contour must either be a closed contour
(starting point=end point) which encompasses the
finished-part contour either partially or fully, or a
contour section between the starting and end points
of the finished-part contour. The programmed
direction is irrelevant.
4-270
Blank definition
X
with closed contour
X
Blank contour as contour section between
starting and end point of fin. part contour
Blank and fin.
part end point
Blank and fin. part starting point
SINUMERIK 840D/840Di/810D/FM-NC Programming Guide, Cycles (PGZ) - 04.00 Edition
03.96
04.00
4
Finished part contour
Blank contour
Starting point
=blank end point
Finished part contour
Blank contour
 Siemens AG 2000 All rights reserved.
Z
Z