The rated fixed bolt tightening device is placed on a car assembly line. The assembly process stipulates that the coupling torque is (55 ± 5) Nm, and the torque control accuracy of the device is ± 3%. The calibration and evaluation of the device is used. The “dynamic process method†carried out on site uses a special bracket to connect the high-precision torque sensor directly between the power head and the thread pair. During operation, the output torque value Mw of the tightening gun and the torque used as the measurement standard can be read simultaneously. The sensor's reading value is Ms. As one of the important contents of the acceptance of new equipment, accuracy and machine capability tests must be carried out. After the bolt tightening equipment is in a stable state, the assembly is continuously simulated 50 times to obtain two sets of measured torque values: Mwi and Msi, two torque values. The difference, the magnitude of which reflects the accuracy of the device being inspected. According to the accuracy index ±3%, the upper and lower extreme values ​​of the controlled torque can be obtained: ±3%×55=±1.65(Nm) and the values ​​are compared, all within the range of ±1.65, so it can be confirmed that this fixed The accuracy of the bolt tightening equipment is acceptable. The standard measurement 38≥1.67 and Cmk≥1.67, so the evaluation of the bolt tightening equipment of the inspected indicates that the machine capacity not only meets the requirements, but also more than enough. It can be seen that the machine capability mainly depends on the workpiece manufacturing tolerance T and the standard deviation of the measured results of the sample. S. It is the ratio between them that determines the capacity of the equipment to be assessed. At the ordinates of 50Nm and 60Nm, two parallel (thick) lines are drawn, and the spacing is determined as the assembly torque tolerance of the workpiece. T. By comparing the T with the above ±3S spacing, it can be visually seen that the equipment The size of the machine's capabilities. There is no doubt that the machine capacity of the bolt tightening device is quite large, which is the original intention of drawing such a graph.
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