Siemens SINUMERIK 840D Programming Manual page 246

Turning Cycles 03.96
08.97
4 4
4.7 Thread cutting – CYCLE97
Connection between SPL, FPL, APP and ROP
(starting point, end point, arc-in section and arc-
out section)
The programmed starting point (SPL) and end point
(FPL) are the basis of the thread. However, the
starting point used in the cycle is the starting point
brought forward by the arc-in section APP and, in the
same way, the end point is the programmed end
point brought back by the arc-out section ROP. The
starting point defined by the cycle always lies
1 mm outside the programmed thread diameter in
the facing axis. This retraction plane is automatically
generated by the control.
Connection between TDEP, FAL, NRC and NID
(thread depth, final machining allowance,
number of cuts)
The programmed final machining allowance has an
effect parallel to the axis and is subtracted from the
preset thread depth TDEP and the remainder is
divided into roughing cuts.
The cycle automatically calculates the individual
actual infeed depths depending on the parameter
VARI.
The thread depth to be machined is divided into
infeeds with the same cross-section of cut so that
the cutting pressure remains constant for all rough
cuts. Infeed is then performed with differing values
for the infeed depth.
In a second method, the total thread depth is divided
into constant infeed depths. The cross-section of cut
gets larger from cut to cut. However, if the values for
the thread depth are small, this method can create
better cutting conditions.
The final machining allowance FAL is removed in
one cut after roughing. After this, the noncuts
programmed under parameter NID are executed.
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SINUMERIK 840D/840Di/810D/FM-NC Programming Guide, Cycles (PGZ) - 04.00 Edition