Ergonomics - Atlas Copco
Ergonomics - Atlas Copco
Ergonomics - Atlas Copco
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EXTERNAL LOAD<br />
For evaluation purposes, it is assumed that<br />
the tool is being used for line assembly in<br />
the motor vehicle industry at a work-<br />
station where the tool is used on horizontal<br />
surfaces. The height is adjusted to allow a<br />
comfortable posture for counteracting the<br />
horizontal pull force from the torque re-<br />
action. The tool is used on a 50 Nm soft<br />
joint. It is operated with two hands. The tool<br />
is suspended in a balancer. The balancer is<br />
assumed to be correctly adjusted, therefore<br />
the pulldown force can be discounted.<br />
It is assumed that both male and female<br />
operators use the workstation. Therefore<br />
two evaluations of external load have been<br />
Male operators<br />
made, one for male operators and one for<br />
female operators. Two-handed operation<br />
means there will be no palmar flexion<br />
torque. Since the tool is suspended in a bal-<br />
ancer, supination and radial flexion torque<br />
can be discounted.<br />
Real loads can be calculated as follows:<br />
Trigger force is measured to 3 N. The<br />
trigger can be operated using one or two<br />
fingers.<br />
On soft joints the installed torque will<br />
give a reaction force (pull back) on the<br />
operator equal to the installed torque<br />
divided by the distance from the spindle<br />
to the center of the handle. In this case:<br />
50/0.370 = 135 N.<br />
Force/Torque MVC Safety factors Reduced Real load Real / Score<br />
N/Nm Speed Frequency Duration MVC N/Nm Reduced<br />
Trigger 80 N a1=0.8 a2=0.6 a3=0.8 31 N 3 N 0.1 1<br />
Pull back 400 N 154 N 135 N 0.9 14<br />
Female operators<br />
Table 4.18 Evaluation of external load for the Electric Angle Nutrunner Tensor ST61-50-10.<br />
Evaluations are given for both male and female operators.<br />
Total score: 15<br />
Force/Torque MVC Safety factors Reduced Real load Real / Score<br />
N/Nm Speed Frequency Duration MVC N/Nm Reduced<br />
Trigger 50 N a1=0.8 a2=0.6 a3=0.8 19 N 3 N 0.2 2<br />
Pull back 300 N 115 N 135 N 1.2 33<br />
Total score: 35<br />
167