Chapter 9
231
Logic programming – Function blocks
In order to fulfill the safety standards it may be necessary to use tested switches for
the cam input signals, each with different test sources. To use different test sources
for the cam signals, the Overrun cam, Upstroke cam and Dynamic cam need to be
connected to different WS0-XTDI or WS0-XTIO modules.
One WS0-XTDI has two test sources only, even if it has eight test output terminals.
Overrun monitoring
The Eccentric press contact function block monitors the overrunning of the press. If
the Overrun cam is left although the press is supposed to have stopped, then the
function block detects an Overrun error.
The Drive released input signal must then accord to Figure 216 and the following rule.
At the Drive released input there has to be either a Low to High transition while the
Top output is High or the Drive released input has to be High at the end of the
Overrun cam (High-Low transition). If none of these two conditions is fulfilled, the
Enable output becomes Low and the Overrun error output becomes High.
The Drive released input must be connected to the signal that controls the physical
output of the press drive, so that the function block can determine whether the press is
currently supposed to be running or has been stopped. Typically this is the Enable
output of a subsequent Press setup or Press single stroke function block.
Do not connect any physical input signals to the Drive released input. Connect the
signal that controls the physical output for the press drive using a jump address or a
CPU marker.
If a jump address is used, make sure that this signal is a loop-back. This is
indicated by a clock icon on the destination tag of the jump address. To this
purpose, connect the outputs of this function block to the following function blocks
before you connect the jump address to the Drive released input. This applies
especially if all connections to the following function blocks are also realized using
jump addresses.
If a CPU marker is used, then a Routing function block must be used to split the
signal to the physical output for the press drive and to the CPU marker output.
Note
Figure 216:
Overrun monitoring with the
Eccentric press contact
function block
Note
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