Rockwell Automation 440F MatGuard, 440F-C4000 Mat Controllers - Manual (Page 20)

The overall stopping time T is made up of two parts: T = t1 + t2
t1 is the maximum time between actuation of the sensing function and the output signal
switching devices being in the OFF state.
For the mat system, t1 = 35mS.
t2 is the response time of the machine i.e. the time required to stop the machine or remove the
risks after receiving the output from the mat system.
The response time of the machine used in the calculation needs to be the worst case time. Some
machines have inconsistent response times which are dependent upon mode of operation, nature of the
workpiece and point in the operating cycle at which stopping is initiated. An allowance should be made
for wear in brakes etc if this can affect the response time. An allowance for further delays in the machine
control system may be required in some circumstances.
CALCULATION EXAMPLE
In this example the mat system is being used with a machine whose worst case response time has been
measured as 0.485 seconds.
Using the formula,
T = t1 + t2
= 35mS + 485mS
= 520mS = 0.520S
S = (1600 x 0.520) + 1200mm
= 832 + 1200mm = 2032mm
Sensor mats will be required from 2032mm right up to the edge of the machine baseplate.
5.4.2 FOR USE AS A PRESENCE SENSING SYSTEM WITHIN A PERIMETER GUARDED AREA
If the area around the hazard is totally enclosed within a guarded perimeter, the requirements of prEN
999 may not apply. In these applications the mat system detects the presence of an operator to prevent
the perimeter guarding system being reset and the machine re-started while the operator is inside the
enclosure.
Fig. 13 NOTE: Fixed guarding should meet the requirements of EN 953, EN 294 & EN 811.
A suitable perimeter guarding system would be a fixed guard with an access door fitted with an interlock
switch with conditional guard unlocking (see EN 1088). A trip device such as a safety light curtain may
also be suitable for some applications. It is important to note that the positioning of the light curtain must
be calculated according to EN 999.
When using the mat system for these applications the entire enclosed floor area accessible to the
operator should be covered by sensor mats.
HAZARD
PRESSURE
SENSITIVE MATS
FIXED GUARDING
INTERLOCKED DOOR
(WITH LOCKING)
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