Siemens SINUMERIK 840D sl Function Manual page 1314

V1: Feedrates
17.2 Path feedrate F
Example
S
G96
● Where r = 0.2 m → n = 183.12 rpm
● Where r = 0.1 m → n = 366.24 rpm
⇒ The smaller the workpiece diameter, the higher the speed.
For G96, G961 or G962, a geometry axis must be defined as the transverse axis.
The transverse axis, whose position affects the speed of the mater spindle, is defined using
channel-specific machine data:
MD20100 $MC_DIAMETER_AX_DEF (geometry axis with transverse axis function)
The function G96, G961 or G962 requires that the machine zero and the workpiece zero of
the transverse axis are in the turning center of the spindle.
Constant speed (G97, G971)
G97, G971 deactivates the "Constant cutting rate function" (G96, G961) and saves the last
calculated spindle speed. With G97, the feedrate is interpreted as a revolutional feedrate (as
with G95). When programming G971, linear feedrate is selected (as with G94). The feedrate
F is interpreted in mm/min or inch/min.
When G97, G971 is active, an S value can be reprogrammed to define a new spindle speed.
This will not modify the cutting rate programmed in G96, G961.
G97, G971 can be used to avoid speed variations in motions along the transverse axis without
machining (e.g. cutting tool).
Note
G96, G961 is only active during workpiece machining (G1, G2, G3, spline interpolation, etc.,
where feedrate F is active).
The response of the spindle speed for active G96, G961 and G0 blocks can be defined in the
channel-specific machine data:
MD20750 ALLOW_G0_IN_G96 (G0 logic for G96, G961)
When constant cutting rate G96, G961 is selected, no gear stage change can take place.
The spindle speed override switch acts on the spindle speed calculated.
A DRF offset in the transverse axis does not affect the spindle speed setpoint calculation.
At the start of machining (after G0) and after NC stop, G60, G09, ... the path start waits for
"nAct= nSet".
The interface signals "nAct = nSet" and "Set speed limited" are not modified by internal speed
settings.
When the speed falls below the minimum speed or if the signal "Axis/spindle stationary" is
recognized, "nAct =nSet" is reset.
A path operation which has started (G64, rounding), is not interrupted.
1314
= 230 m/min
Function Manual, 01/2015, 6FC5397-0BP40-5BA2
Basic Functions