Rockwell Automation 445L GuardShield Micro 400 Safety Light Curtain User Manual - Manual (Page 11)

R
GuardShield™ Micro 400 Safety Light Curtain User Manual
9
Original instructions
various studies and although these studies indicate speeds
of 63 inches/second to over 100 inches/second, they are not
conclusive determinations. The employer should consider
all factors, including the physical ability of the operator,
when determining the value of K to be used.”
Ts Stop time of the machine tool measured at the final control
element.
Tcs Response time of the control system.
Note: T
s
and T
cs
are usually measured by a stop time measuring
device.
Tr Response time of the presence sensing device (safety light
curtain) and its interface (MSR4x and MSR45E). This value is
generally stated by the device manufacturer or it can be
measured by the user.
Tbm Additional time allowed for the brake monitor to
compensate for variations in normal stopping time.
Dpf Depth penetration factor. It is an added distance to allow for
how far into the protective field an object, such as a finger
or hand, can travel before being detected. D
pf
is related to
the safety light curtain’s object sensitivity. Object sensitivity
is the smallest diameter object which will always be
detected anywhere in the sensing field.
Example:
In opto-electronic safeguarding, such as with a perpendicular
safety light curtain applications with object sensitivity (effective
resolution) less than 2.5 inches, the D
pf
can be approximated
based on the following formula:
D
pf
(inches) = 3.4 × (Object Sensitivity – 0.276),
but not less than 0.
European Safety Distance Formula
A safety distance must be maintained between the light curtain
and the point of danger. This safety distance ensures that the
point of danger can only be reached after the dangerous state of
the machine has been completely removed.
The safety distance as defined in EN ISO 13855 and EN ISO 13857
depends on:
• Stopping/run-down time of the machine or system. (The
stopping/run-down time is shown in the machine
documentation or must be determined by taking a
measurement.)
• Response time of the protective device, e.g. GuardShield Micro
400 (for “Response Time” see page 7).
• Reach or approach speed.
• Resolution of the light curtain and/or beam separation.
Figure 4: Safety distance from the point of danger
How to Calculate the Safety Distance S
According to EN ISO 13855 and EN ISO 13857:
-> First, calculate S using the following formula:
S = 2000 × T + 8 × (d – 14) [mm]
Where…
T = stopping/run-down time of the machine
+ response time of the protective device [s]
d = resolution of the light curtain [mm]
S = safety distance [mm]
The reach/approach speed is already included in the
formula.
-> If the result S is <= 500 mm (19.6 in.), then use the determined
value as the safety distance.
-> If the result S is > 500 mm (19.6 in.), then recalculate S as
follows:
S = 1600 × T + 8 × (d – 14) [mm]
Example:
Stopping/run-down time of the machine = 290 ms
Response time = 30 ms
Resolution of the light curtain = 14 mm (0.55 in.)
T = 290 ms + 30 ms = 320 ms = 0.32 s
S = 2000 Ч 0.32 + 8 Ч (14 – 14) = 640 mm (25.1 in.)
S > 500 mm (19.6 in.) therefore:
S = 1600 Ч 0.32 + 8 Ч (14 – 14) = 512 mm (20.1 in.)
Minimum Distance from Reflecting Surfaces
The infrared light from the transmitter may be reflected off of
shiny surfaces and be received by the system’s receiver. If this
condition occurs, it can result in an object not being detected
when it enters the GuardShield Micro 400 sensing field.
All reflecting surfaces and objects (e.g. material bins) must
therefore be located at a minimum distance a from the protective
field of the system. The minimum distance a depends on the
distance D between transmitter and receiver.
Safety distance S (D
s
)
Protective field height
Point
Distance to avoid standing behind
of
danger
the safety curtain 75mm