Construction of high strength bolts, the use of fixed torque (adjustable) electric wrench construction
One of the most important points in the calibration of electric fixed torque wrenches is to strictly simulate the actual working conditions, from bolts and wrenches to temperature and humidity to specific steps. General calibration of 5 bolts to take the average value for saving bolts, you can calibrate the beginning of the end of the wrench wrench, wrench, pay attention to calibration, the end of the wrench, the bolt should also simulate the actual situation, first hit the first, then re labeled.
There are many kinds of fixed torque electric wrench, but the inertia has an influence on the final screw value. This is just like the distance of the automobile brake on the braking accuracy. Ordinary electric fixed torque wrench adopts series motor, which has the advantages of low price, easy start and soft characteristic. But it has high speed, big inertia, and adopts current control. The control accuracy is easily affected by the initial value. Digital torque wrench with torque sensor can be a little better. The best is to use AC servo motor with torque sensor fixed torque electric wrench, motor brake, less affected by the initial screw, but the price is expensive.
The reason why by the initial tightening, mainly to allow the stack of stickers, reduce a node plate bolt because of tightening sequence caused by axial force influence each other, generally think that the stack close under the initial tightening as small as possible, because the initial tightening is too large, especially over 70%, does affect the precision of the final twist. The high strength bolt construction initial tightening torque is probably the final twist of the 15%~20% provisions of our country is 50%, mainly because of the installation of steel structure in the process, some members of the cantilever state, the node board also force tighteningtightening 50% can ensure the installation progress, save the United States bolt (need to use technology bolt), and can guarantee the accuracy of the final twist.
Do not know your specific situation, do not know whether to answer the right?. If there are any problems, please provide specific bolt specifications, wrench specifications, initial torque and final torque.
