Siemens SINUMERIK 840D sl Function Manual page 454

Mode Groups, Channels, Axis Replacement (K5)
6.3 Channels
Response
A) Starting with the motion block before the WAITMC() call, the wait marks of the other
channels to be synchronized are checked. If these have all been supplied, then the channels
continue to operate without deceleration in continuous-path mode. No wait. The path velocity
remains unchanged.
B) If at least one wait mark from one of the channels to be synchronized is missing, then the
axes start to decelerate from path velocity down to exact stop velocity. A check is now
performed in every interpolation cycle to see whether the missing wait marks of the channels
to be coordinated have arrived in the meantime. If this is the case, the axis is accelerated up
to path velocity again and machining continued.
C) If the marks to be supplied by the channels to be synchronized have not arrived by the
time exact stop velocity is reached, the machining operation is halted until the missing marks
appear. When the last required mark appears, the axes are accelerated from standstill up to
path velocity.
The following table shows the sequences of events for cases A) - C):
Deceleration response to conditional wait with WAITMC()
With WAITMC
A) Wait marks of all channels
have already arrived
B) All wait marks arrived during
deceleration from path velocity
down to exact stop velocity
C) The last wait mark does not
arrive until exact stop velocity
has been reached.
Extended behavior and block change when WAITMC occurs
WAITMC and SETM (in Synact) can be synchronized.
Note
When G64 is active, a WAITMC(1,2,3) block does not generate a separate block, but is
appended to the preceding block. A drop in velocity must be prevented when continuous-
path mode is active. A WAITMC is therefore fulfilled if the preceding block is halted, e.g. by a
read-in disable.
With block change condition IPOBRKA, when the wait flag is received, the next block is
loaded instantaneously and the axes started, provided none of the other block end
conditions prevent the block change. Braking only occurs if the flag is not yet reached, or
another block end condition prevents the block change.
454
Response
Continued operation with no
deceleration
Deceleration ceases
immediately when last
expected wait mark appears.
The axes are accelerated back
up to path velocity.
Brake down to exact stop
velocity. When the last
required mark appears, the
axes are accelerated from
exact stop velocity up to path
velocity.
Function Manual, 01/2008, 6FC5397-1BP10-3BA0
Velocity curve
Extended Functions