Siemens SINUMERIK 840D sl Programming Manual page 625

Difference in speed M3 S... or M4 S...
A difference in speed results from signed superimposition of two sources of speed and is
programmed again for the following spindle e.g. where Sn=... or Mn=3, Mn=4 in speed
control mode during an active synchronized spindle coupling. During the process, this speed
component is derived from the main spindle using the coupling factor and the following
spindle added to this with the correct prefix.
Note
When the direction of rotation is M3 or M4, the speed S... also has to be reprogrammed
because otherwise an alarm is triggered to report missing programming.
For more information on difference in speed, see
References: /FB2/ Function Manual, Extension Functions; Synchronized Spindle (S3).
Difference in speed for COUPONC
Transfer of a movement for difference in speed
When a synchronous spindle coupling is activated with COUPONC a currently active speed is
overlaid on the following spindle (M3 S... or M4 S...).
Note
Enabling overlaying
A spindle speed overlaid by means of COUPONC (M3 S... or M4 S...) needs to be enabled
before it will take effect.
Dynamic restriction of the leading spindle
The dynamic responses of the leading spindle have to be restricted to such an extent that
when overlaying is applied to the following spindle, its dynamics limit values are not
exceeded.
Job Planning
Programming Manual, 06/2009, 6FC5398-2BP20-0BA0
Axis couplings
9.5 Synchronous spindle
625