Atlas Copco PowerMACS 4000, User Manual

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Tightening
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Dynamic mode: TTrig is dynamically calculated as percentage of the current max torque
that has been reached so far during the step. The user specifies the percentage to use. The
check is started as soon as the torque passes the threshold torque level.
Fixed Mode: TTrig is a fixed torque level specified by the user. In this mode the Threshold
torque is not needed.
To prevent false detections of stick slip the counter of the drops below TTrig is reset if a too
long angle has been run since the last drop. The counter is reset if the angle since the latest
drop is larger than the angle between the first and latest drop, i.e. if
a
– a
i
> a
i
– a
1;
a = current angle, a
1
= angle at first drop, a
i
= angle at last drop
Note 1: Since this is a check the step will continue to run to the final target even after a
stick-slip has been detected.
Note 2: Since the sample frequency of the torque transducer normally is 1 kHz the check
can have problems to detect a stick slip with a frequency higher than 500 Hz.