Thread With Constant Lead - Siemens SINUMERIK 880 Programming Manual

01.93
Depending on machine data, the feedrate override
switch, "Feed hold" pushbutton, spindle speed override
switch and single block function may be ineffective with
With thread cutting blocks (G33/G34/G35), the feedrate is not determined by the programmed
linear feedrate but calculated from the specified thread lead and the spindle speed. This
feedrate determines the path speed for the thread cutting block:
v = n · H
This path speed must not exceed the maximum speed of the axis (machine data). In addition,
the maximum path speed is limited by the scanning time.
If the maximum path speed is exceeded, the alarm "Programmed S value too high" is
triggered.
The feedrate programmed under F is retained however and is reactivated if G01, for example,
is programmed again.
The lead of the taper on which the thread is cut can be modified in steps. When cutting
longitudinal threads this ensures a gentle runout of the thread.
Note:
If, in the case of tapping blocks (G33/G34/G35) on milling machines, the opposite travel
direction is programmed after the first thread cutting block but the direction of rotation of the
spindle is not reversed, the previous travel direction is nevertheless maintained. However, the
programmed travel direction is output to the PLC.
If, as a result, the direction-evaluating limit switch monitoring reponds, the axis will be stopped
(setpoint speed = 0) because the programmed and the actual travel direction do not agree.
4.3.2

Thread with constant lead

It is an integral part of spindle package E40 to E45.
The feedrate F is not programmed here since the feedrate is linked directly to the spindle
speed via a pulse encoder.
© Siemens AG 1991 All Rights Reserved
SINUMERIK 880, (PG)
thread cutting.
v = path speed
n = speed of spindle or rotary axis
H = thread lead
The "Thread constant feed" function
is an Option.
6ZB5 410-0HD02
4 Programming of Motion Blocks
4.3.1 Thread cutting G33/G34/G35/G37
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