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ANSI Standard B11.19-2003
Formula for calculatlng safety
distance of llgbt curtains from
hazardous point of operation.
The effective sensing field of the device shall be located
at a distance from the nearest recognized hazards such
that the operator or others cannot reach the hazard with a
hand or other body i::art before cessation of motion during
the hazardous portion of the machine cycle.
The point at which a device responds to an intrusion may
vary. The devices should be located or adjusted such that
the device always responds to the intrusion at or prior to
the safety dist ance. Care should be exercised when
installing the device to ensure that it does not detect false
signals from other devices in the area.
Usually the electro-optical presence-sensing device is used
in a manner that provides a protected zone in front of the
primary work area with auxiliary devices or guards used
to protect secondary access areas. In some cases,
however, mirrors may be used in conjunction with the
device to provide 2-, 3-, or 4-sided protection.
The machine stop time should be measured with the
machine running at its fastest speed with its heaviest die
or tooling and the stop time being measured at the 90
position in the downstroke.
Figure 2: Minimum Object Sensitivity and D(pf)
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0
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e
Minimum
l!I (,
Object
Sensitivity,
o,
25
(1,
s
A
13 (0.
5
I
.....r
0
0
0 0
25
(
,0)
( 0) {3 0)
Regulations & Guidelines for Safe Operation
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50
102
12
152
<•
0) (5.0 (6 0)
=
Dpf
3.4 (S-7) mm
=
(Dpf
3.4 (S-0.275) in)
The following formula should be used when calculating
the safety distance:
Os = K x (Ts
=
Os
Minimum safety distance between the
device and the nearest point of operation
hazard (in inches).
=
K
Hand speed constant. This value has been
determined by various studies and, although
these studies indicate speeds of 63 in/sec to
over 100 in/sec, they are not conclusive
determinations.
determine this value by considering all factors,
including physical ability of the operator
=
Ts
Stop time of the machine tool measured by a
stop time measurement device.
=
Tc
Response time of the control system (usually
is taken care of by the measurement device).
=
Tr
Response time of the presence-sending
device and it's interface, if any, as stated by
the manufac turer or measured by the
employer.
=
Additional time allowed for the brake monitor
Tbm
to compensate for variations in normal
°
stopping time.
=
D(pf)
Depth Penetration Factor. Added distance as
indicated by Figure 2. The minimum object
sensitivity is stated by the manufacturer. If a
Floating Blank is used, use the Op' numbers
found on Tables 2 and 3.
_,v
Penetration factor, Dpt, for presence-sensing
devices used in a vertical application with object
-
-
sensitivity less than 64 mm (2.5 inch es)
-
,-
1-
Dpf, the distance added to the safety distance due to
,_.
the penetration factor compensates for varying object
sensitivities of electro-optical presence-sensing
devices.
When blanking features are used and when the
blanked area is not completely filled by the workpiece
1 8
.0)
or part, or by mechanical guarding, the minimum
object sensitivity can be calculated as:
Object sensitivity
minimum object sensitivity without blanking.
Once this value is found, then determine Op'.
If the entre blanked area is filled with mechanical
guarding or other fixed material or guards, use the
device's object sensitivity to determine Op'.
Appendix A:
SLTSeries
Tc
Tr
Tbm)
D(pf)
+
+
+
+
The em ployer shoul d
=
size of the blanked area plus
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