In most of the grid accessories industrial equipment processing factory, for the unique position of the assembly, the screw, is a strict operation guide specific guidance, how much torque release often establish standards. After tighten the screw, in order to avoid loose, should be attached to release a pre-tightening force, thus will clean up loose after half a circle pre-tightening force, rack accessories after tighten the screw in the ductile deformation, especially in is in the condition of high temperature and vibration load, as long-term continuous work pressure can cause stress and screw into plastic deformation, its compressive strength will reduce and even invalid.

1. Torque control

Definition: when the tightening torque exceeds the operating torque of a certain setting, the tightening control measures will be terminated immediately.

Advantages: the automatic control system is simple and immediate, easy to check the quality of tightening with torque or high-precision torque wrench.

Disadvantages: low manipulation accuracy (preload deviation ± 25% or so), can not flexibly use the development potential of raw materials.

2. Torque-angle control method

Define: first screw the anchor bolt to a small torque, and then start from the point, screw a required corner control measures.

Advantages: The accuracy of radial preload of anchor bolts of grid accessories is high (± 15%), which can receive a large radial preload, and the standard value can be centralized around the mean value.

Disadvantages: the automatic control system is more complicated, to accurately measure the torque and Angle of the two main parameters; Moreover, it is not easy for the quality inspection unit to find a proper way to check the tightening results.

3. Scope control method

Definition: a way to stop tightening the anchor bolts of grid accessories after tightening to a certain extent.

Advantages: very high tightening accuracy, pretightening force deviation can be controlled within ± 8%; But the key to its accuracy lies in the tensile strength of anchor bolt itself.

Disadvantages: It is necessary to dynamically and continuously calculate and distinguish the slope of torque and Angle curve in the whole tightening process of grid accessories, and the practicality and operation rate of automatic control system are often highly regulated.