Lenze PLC Designer PLC Designer (R3-1) - Manual (Page 580)

L-force | PLC Designer
General Editors
578 DMS 4.1 EN 03/2011 TD29
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2. The second CAM may be started relative, if its slave position assigned to the start
equals 0. However, the previous CAM has to be run in non-periodic mode.
Otherwise, if the first CAM was periodic, having processed its first cycle the
assignment of the slave position is not unique anymore:
The box at the right side displays the transmission from CAM1 to CAM2 in detail. The
blue lines indicate evaluations of the CAM function at master position x1 and x2. Let
us consider the periodic case at first:
MasterAbsolute := TRUE;
SlaveAbsolute := FALSE;
CAM(x1, CAM1, PERIODIC:=TRUE); This call evaluates the CAM at master position x1, which
is smaller than the end position of the range of CAM1.
So, CAM1 is evaluated in the usual way resulting in Point
1 for the slave position.
CAM(x2, CAM1, PERIODIC:=TRUE); When the module is called for the next time, the master
position x2 has exceeded the end position of CAM1
(indicated by the green dashed line and equal to the
abscissa of point 3p). Therefore, the EndOfProfile Flag is
raised. As CAM1 is started in periodic mode, it will be
restarted at end of range of CAM1what will return point
2p as result of the call.
CAM(EXECUTE:=FALSE); Switch to the new CAM.
CAM(x2, CAM2, PERIODIC:=TRUE); Second evaluation at master position x2. This time the
new cam CAM2 gets evaluated. As CAM2 is started in
relative mode the actual position of the slave (2p) is
added as offset to the CAM2 mapping. So, the start point
of its graph is shifted to point 3p. Its evaluation at
master position x2 results in point 4p, thus in an
undesirable jump.