3 608 870 A47
Tightening Technology |
Bosch Rexroth AG 259
Nexo cordless Wi-Fi nutrunner
| 3 608 870 A47/2019-10
10.2
Torque-controlled tightening process
Torque is the most easily accessible measured variable in tightening technology, which is why this tight-
ening process is easy to handle. Here, the torque is controlled and the angle of turn monitored.
The torque-controlled tightening process offers the following advantages:
•
easily accessible measurement variable (= torque)
•
use of standard bolts
•
re-usability of bolts (bolts are only deformed in the elastic range)
The torque is directly measured at the bolt while the tightening process is in progress and recorded by
the measurement transducer on the tightening spindle.
Function
Fig. 10–1:
T = f (A), torque-controlled, angle of turn-monitored tightening process
The torque increases from positioning of the bolt head, exceeds the torque threshold Ts starting angle
counting, and reaches the target parameter TP, after which the tightening process is ended. The torque
threshold TT should be at the beginning of the linear increase of the tightening graph (as the joining pro-
cesses of the tightening parts are almost complete here).
Angle of turn monitoring (A–, A+)
1)
is used for error recognition. The advantages of angle of turn monitor-
ing include recognition of:
•
Lot jumps in bolts and components
•
Over-twisting of threads via a measurable angle of turn increase
•
Incompletely cut threads
(1)
Angle safety limit
1) The limit values (A–, A+) should be defined by statistical evaluation ((
50 tightening operations). Too
small tolerance limits result in a high number of NOK tightening cases; too large tolerance limits impair
fault recognition.
[Nm]
W–
W+
Mz
Mo
Mu
Ms
0
(1)
[ ]
o
T+
T
P
T–
T
S
A–
A+
