Rexroth Tightening System 350 System Documentation - Rhino ...

238/316 Bosch Rexroth AG | Tightening Technology 9 Tightening Processes9.3 Tightening processesThe torque increases from positioning of the screw head until it reaches the torque threshold Ts (torquecontrolled).Ts should be at the beginning of the linear increase of the tightening graph (as the joiningprocesses of the tightening parts are almost complete here). From the torque threshold Ts, rotation continuesat a defined angle of turn (tightening angle) until the target parameter AP is reached.Torque monitoring (T–, T+) 1) is used for error recognition. Their advantages include recognition of:– Lot jumps in bolts and components– Defective bolts and componentsIn this process, the bolt is stretched beyond its yield point until it plastically deforms. Reusability of thebolt is limited due to lasting cross-section constriction. This is why special bolts with sufficient deformationcharacteristics (e.g. stretch-shank bolts) should be used in this process.9.3.4 Yield point-controlled tightening processesThis process uses the gradient calculation in the measurement transducer. The bolt is tightened until itsyield point (elastic limit) is reached, i.e. in contrast to the angle of turn tightening process, it is only tighteneduntil it reaches its limit for plastic deformation.The yield point-controlled tightening process offers the following advantages:– Use of standard bolts– Reusability of bolts– Yield point-controlled tightening processes, i.e. the tightening factor 2) ís almost 1– Minimum influence of frictionThe angle of turn recording and determination of the gradient (see page 206) is implemented in the measurementtransducer.An example parameterization can be found on page 239.Function[Nm]T+ M+Yp SGT– M–GG max[ ]Ts MsG maxYp SG G max /2 /20A– W– A+ W+oFigure 9–45:T = f (A), yield point-controlled tightening process1) Limit value definition (T–, T+) should be done via a statistical evaluation (≥ 50 tightenings). Too-smalltolerance limits result in a high number of NOK tightening cases; too-large tolerance limits impair faultrecognition.2) Tightening factor = F Tmax /F Tmin = dispersion of the mounting clamp force (clamp force).System 350 | 3 608 878 040/05.2008