ATI Industrial Automation
1031 Goodworth Dr.
Apex, NC 27539 USA
PH: +1 919-772-0115
FX: +1 919-772-8259
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Collision Sensor Application Worksheet
(MS Excel)
How to Select a Protector Model
For a successful application, the Protector chosen should be sized appropriately.
To choose a model, consider the loads produced due to the static weight of the tooling,
the inertial loads imposed by robot motion and the loads produced by the end-effector
when performing its intended tasks. Once these loads are calculated and a specific
model is chosen, the nominal pressure setting for the break-away point can be determined.
The required air pressure setting must be readily available with ample adjustability.
For example, a calculated pressure setting of 50 psi should have an adjustable range
of 25-75 psi.
The selection process is as follows:
1. Calculate Applied Loads:
Figure 1 can be used to convert the forces acting on the end-effector tooling into
the resulting moment, torque, and axial loads applied to the Protector. Use the
diagram shown in Figure 1 and the formulas below to calculate the worst case applied
loads for your application. All three load cases—Axial, Torque, and Moment—should
be assessed for their Static, Dynamic, and Working force components.
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Note: Not all of the component forces (Static, Dynamic, and Working) are present
during all phases of the robot program. As a result, the worst case conditions for
Axial, Torque, and Moment loads may occur at different times in the program.
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Formulas:
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Axial Load (F) |
= |
F2
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Torque (T)
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= |
F3*D3
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Moment (M) |
= |
√( (F1*D1)2 + (F2*D2)2
)
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(F1, F2, & F3 consist of the sum of their respective Static, Dynamic, and Working
force components; and should always be positive for purposes of calculating break-away
pressure settings.)
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a. Static Force: The load applied by tooling weight while the robot
arm is idle. This includes the weight of all parts attached to the Protector, acting
at the assembly’s center of gravity along the direction of gravity.
b. Dynamic Force: The inertial force imposed at the center of gravity
of the tooling due to acceleration of the robot arm. This force acts in the direction
opposite of motion. Dynamic forces are additive to static forces and must be carefully
considered to ensure proper sizing of the protector.
c. Working Force: Forces are generated at the tooltip under normal
working conditions. If these forces and their location are known, they can be converted
into loads on the Protector using the same technique.
2. Choose a Protector model:
Once the approximate loads are known from step one, pick a model that has a nominal
moment and torque rating above the calculated loads under both dynamic and working
conditions.
3. Obtain required pressure setting:
For a given model with known loads, the pressure setting required can be
approximated from the following formula:
P = PM + PT + PF
Where PM, PT, and PF are
the pressure components related to the moment, torque, and force load components
expected at the break-away. PM, PT, and PF are calculated using the formulas in
the following tables, where M, T, and F are the expected loads at the set pressure break-away.
Table 1: Protector Pressure Setting Calculations
(English Units: lb-in, psi, lb) |
| Model | Moment | Torque | Axial |
| SR-61 | (M x 0.376) - 3.3 | (T x 0.444) - 6.3 | F x 0.462 |
| SR-81 | (M x 0.172) - 0.2 | (T x 0.168) - 0.8 | F x 0.233 |
| SR-82 | (M x 0.172) - 0.2 | (T x 0.168) - 0.8 | F x 0.233 |
| SR-101 | (M x 0.085) | (T x 0.081) - 2.8 | F x 0.147 |
| SR-131 | (M x 0.030) | (T x 0.033) - 1.7 | F x 0.085 |
| SR-176 | (M x 0.013) | (T x 0.012) - 2.4 | F x 0.045 |
| SR-221 | (M x 0.0052) | (T x 0.0065) + 7.3 | F x 0.029 |
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Table 2: Protector Pressure Setting Calculations
(Metric Units: N-m, Bar, N) |
| Model | Moment | Torque | Axial |
| SR-61 | (M x 0.2294) - 0.2 | (T x 0.2708) - 0.4 | F x 0.00719 |
| SR-81 | (M x 0.1052) | (T x 0.1027) - 0.1 | F x 0.00361 |
| SR-82 | (M x 0.1052) | (T x 0.1027) - 0.1 | F x 0.00361 |
| SR-101 | (M x 0.0517) | (T x 0.0495) - 0.2 | F x 0.00228 |
| SR-131 | (M x 0.0183) | (T x 0.0199) - 0.1 | F x 0.00132 |
| SR-176 | (M x 0.0077) | (T x 0.0075) - 0.2 | F x 0.00070 |
| SR-221 | (M x 0.0032) | (T x 0.0040) + 0.5 | F x 0.00045 |
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Example: For an SR-81 with a moment of 100 lb-in, torque of 50 lb-in and an axial
load of 20 lbs, and an acceleration of 2 G’s, the pressure setting is calculated
as follows:
P = ((100*0.172) - 0.2) + ((50*0.168) - 0.8) + (20*0.233) + ((100*2*0.172) - 0.2)
= 17 + 7.6 + 4.66 + 34.2
= 63.46
A nominal air pressure setting of 63 psi is required.
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