The tightening process control strategy refers to the process control strategy method used to connect fasteners and workpieces together using tools. At present, the most mainstream strategies in the market are torque control and angle monitoring control. In addition, there are also simple torque methods, angle control and torque monitoring methods, yield point method, fitting point (also known as differential torque) method, etc. Today, let's discuss several main tightening process control strategies for your reference.

1. Torque method control strategy control

Content: this process control strategy only controls the output torque and does not control any other parameters.

Application scenario: currently, most industries, especially the automotive industry, are very rare.

Advantages: the cost of purchasing tightening tools is low.

Disadvantages: for example, it is difficult to detect or eliminate common failure phenomena such as floating nails and crooked nails.

2. Torque control and angle monitoring strategy control

Content: this process control strategy monitors the changes in angle while controlling the torque output size.

Application scenario: currently, this strategy is most commonly applied in most industries, especially in the automotive industry.

Advantages: the cost of purchasing tightening tools is relatively low. This process control strategy can achieve the majority of error prevention functions in most cases, such as floating nails, sliding teeth, broken nails, etc.

Disadvantages: in some scenarios where the friction coefficient of threads varies greatly, such as when the threaded hole is used to connect the workpiece or when the surface roughness of the workpiece changes, it exhibits significant fluctuations in the pre tightening force (also known as clamping force or axial force).

3. Angle control and torque monitoring strategy control

Content: this process control strategy can also be referred to as torque and angle control strategy. It refers to the control strategy of causing the connector to rotate and fix the angle after tightening to a certain torque. On the basis of implementing these, ultimately monitor the overall torque output changes.

Application scenario: currently, this tightening strategy is mainly used on high-strength bolts with large specifications of M6 and above. For example, the connection positions of the cylinder head, crankshaft pulley, main bearing cover, etc. on the entire vehicle. This tightening strategy usually occurs in the plastic range, where the bolt has already undergone plastic deformation.

Advantages: the output pre tightening force fluctuates less, with good consistency in pre tightening force, and is less affected by changes in threaded hole friction coefficient and surface roughness.

Disadvantages: the procurement cost of tools is relatively high, and currently most domestic tightening tools do not have this strategy function. When the surface friction coefficient or roughness changes too much, the output torque changes significantly. Due to plastic deformation, bolts are generally not recommended for reuse.

4. Yield point control strategy control

Content: this control strategy is to rotate the tightening tool in the specified direction. After reaching a certain threshold (starting) torque, the yield point is detected and calculated. After fixing the angle at each interval, the obtained torque value is compared with the fixed percentage of the previously saved maximum torque value. Once these two values are equal, the program screw determines that the yield point has been reached and the tool stops running.

Application scenario: currently, this tightening strategy is mainly used on some high-strength bolts.

Advantages: the output pre tightening force fluctuates less, with good consistency in pre tightening force, and is less affected by changes in threaded hole friction coefficient and surface roughness.

Disadvantages: the procurement cost of tools is relatively high. Due to the influence of various coupling factors on the frequency setting of angle monitoring, for example, when the angle value is set too low below the highest resolution frequency of the system, the tool will alarm and stop working, resulting in a higher frequency of false alarms.