Chapter 9
250
Logic programming – Function blocks
9.12.4 N-break (press with N-PSDI mode)
Function block diagram
General description
The N-break function block is used for press applications with Presence-Sensing
Device Initiation (PSDI) mode.
Conform to the safety regulations for PSDI mode!
The requirements for PSDI mode are specified in local, regional, national and
international standards. Always implement PSDI applications in conformity with these
standards and regulations as well as in conformity with your risk analysis and
avoidance strategy.
If more than one mode is set up in which the ESPE (e.g. safety light curtain) is not
used, the ESPE has to be deactivated in this mode so that it is clear that the ESPE is
currently not active in protective operation.
If more than one ESPE (e.g. safety light curtain) is used in an application that uses the
N-PSDI functions, only one of the ESPEs may be used to fulfill the requirements for N-
PSDI mode.
In conformity with EN 692 and EN 693 for press applications the number of breaks is
limited to 1 or 2. Other applications depend on the applicable standards.
Prevent access to hazardous movements!
Press systems with a configuration that would allow a person to enter, to cross
through and to leave the protective field of an ESPE are not permitted for PSDI mode.
This function block defines a specific sequence of events that trigger a press cycle.
“Breaks” are defined as the transition from High to Low to High of the PSDI input
signal. In PSDI mode of a press an indirect manual triggering of a press cycle is
carried out based on a predefined number of “breaks” in the ESPE. If the ESPE (e.g.
safety light curtain) detects that the operating movements of the operator related to the
insertion or removal of parts have ended and that the operator has withdrawn all body
parts from the protective field of the ESPE, the press may trigger automatically.
The N-break function block can be used in connection with the Universal press contact
or Press single stroke function blocks and an input for a safety light curtain. The
Enable signal of this function block controls, for example, the Start/Release input of a
Press single stroke function block.
The N-break function block checks whether the start sequence is valid and when the
break counter or the function block have to be reset.
Figure 234:
Function block diagram for
the N-break function block
ATTENTION
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