Deprag AST40-1 Operating Instruction Booklet page 120

Shut-off criteria:
The screwdriving process is ended once the
• Preset Shut-off torque value is achieved (variable based upon the addition of the
friction value and the fixed diferential torque value)
• A calculated Friction value is achieved
• the maximum screwdriving time (time monitoring) is exceeded
Analysis:
OK evaluation:
The screwdriving Sequence is considered OK (fault free), if the screwdriver
shut-off occurs via the differential torque value and the result is within the preset
limits.
Not OK analysis:
The screwdriving sequence is evaluated as Not OK (faulty) if the differential
torque value is outside the preset limits.
The screwdriving sequence is evaluated as Not OK (faulty), if the friction torque
in the monitored angle window is outside the preset limits
The screwdriving level is also evaluated as Not OK when the screwdriving time
limit is exceeded.
Parameter:
The following parameters are used in the Differential strategy:
• Maximum time
Maximum time until the screwdriving sequence step is aborted
• Differential Torque (fixed value)
Input of the differential end torque
The actual target torque results from the sum of the torque of the friction sequence
step and the differential torque value.
• Minimum differential torque
Lower limit of the differential end torque. The actual torque lower limit results from the
sum of the torque of the friction sequence step and the lower limit of the differential
moment
• Maximum differential torque
Upper limit of the differential end torque. The actual torque upper limit results from
the sum of the torque of the friction sequence step and the upper limit of the
differential torque.
• Screwdriver RPM 1
Input of the rotation speed that should be used for the screw run-down sequence
step.
• Threshold torque value switching to RPM 2
Input of the torque value at which the second rotation speed occurs. The actual
threshold torque for the rotation speed decrease results from the sum of the torque of
the friction sequence and the differential torque.
• Screwdriver RPM 2
Input of the rotation speed that should be used for the screw head seating sequence.
• Torque hold time
A holding time can be defined to keep tension applied to the screw joint for a preset
time to allow for material elasticity.
• End value creation: Differential torque / total torque
Selectively the end torque can be displayed as difference between the total torque
and the torque of the previous level or as total torque in the end values.
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