The design and process requirements of bolt tightening torque, bolt tightening method, common tightening tools, tightening torque detection, etc. are introduced. Bolting is the basic method of assembly in the mechanical manufacturing industry. It is widely used in industrial manufacturing and is one of the most important connection methods in the engine. The quality of the bolt connection is directly related to the power and safety of the engine and the sealing of each joint. Sex. In order to make the bolt connection more reliable, more accurate and most effective, the torque is controlled. 1. Bolt torque design and process requirements 1.1 Common standard bolts use torque requirements: Table 1 1.2 Common pipe thread screw tightening torque requirements: Table 2 1.3 Common standard bolt tolerance level requirements: The capital letter on the left corresponds to the torque value in the upper left corner of the installation indicator point and represents the nominal torque value of the bolt. The lowercase letter on the right represents the tolerance level of the bolt torque: table 3 2. Common tightening methods and tightening torque control of bolts There are many ways to tighten the bolts. Commonly used are the torque method (T), the torque-angle method (TA) and the yield point control method (Y1/Y2), and the bolt extension method. 3. Selection of tightening tools during assembly In order to ensure zero error tightening, the tightening tool that meets the design torque requirements can be selected according to the structural characteristics and assembly process of the product. According to the operation mode, it can be divided into two types: hand-held and fixed. 3.1 Hand-held screwdriver Hand-held screwdrivers mainly contain certain types of mechanical torque control. In the simplest case, the tightening torque is limited by motor power and impact force. Developed to the highest stage, the clutch with torque control can be configured to achieve ±3% accuracy (based on standard deviation). 3.2 fixed screwdriver Whether it is a high-precision fixed-torque clutch type pneumatic screw or an electric servo screw, it can be designed as a fixed type. If it is necessary to collect measurement data, it can be realized by matching the torque or angle measurement sensor. The fixed rotation mode of the pneumatic screw cutter is mechanical, and the design of the measurement process is a monitoring form rather than a control method. With an electric servo-controlled screwdriver, the measuring device directly controls the process and the process is directed to the setpoint based on the measured actual value. With it, the measurement accuracy goes directly into the feedback loop and then synchronizes to the assembly result, which can achieve an accuracy of less than ±1% (based on standard deviation). High precision requires a particularly high speed. Achieving high-precision tightening results usually requires a particularly low tightening speed. 3.3 Vector Control Type Electric Torque Tool The whole set of electric fixed torque wrench: one electric fixed torque wrench + one DL control box + 1 connecting cable + 1 operation switch monitor + auxiliary clamp when tightening (including workpiece seating sensor and signal output device) + random Special rings and special sleeves. Tool accuracy: ± 5%. The tool has anti-leakage alarm and prompt function. When the number of bolts and torque are all qualified, tighten the auxiliary clamp before releasing. If the task is in progress, if the clamp is released, the alarm will be alarmed and the wrench will be locked. The tightening process provides torque control, angle monitoring, and down-rotation angle monitoring. The tightening process is completed in one step, and the rotation speed can be arbitrarily edited according to actual needs. With batch counting function, it can be linked with the fixture to avoid bolt leakage. Has the wrong thread detection function. With a hit detection function. The tightening torque is displayed in real time. With tool self-diagnosis, fault prompts and repair tips. If there is unacceptable torque, you can lock the tool and wait for manual processing to avoid the non-conforming product entering the next station. Perfect tightening information feedback, the control box shows the tightening torque value, the tool has the tightening qualified (green light) and the unqualified indicator light (yellow light, red light), and can also be displayed by the light on the status monitor. 3.4 Sensor type fixed tightening shaft The fixed sensor electric servo CNC tightening shaft enables free programming of the screw tightening assembly process. Within the range of performance parameters of the screw, the torque, speed, waiting time and direction of rotation can be freely set and adjusted according to different tightening process requirements, achieving precise screw fastening. The high-precision and comprehensive monitoring function of the fixed electric CNC screw cutter ensures the reliability of the tightening process to the utmost extent. The use of brushless motor drive technology significantly reduces operating costs, resulting in a long life cycle of the screw cutter. At the same time ensuring robust power performance and torque peak output, it is the ideal choice for CNC tightening assembly process. The built-in torque and angle sensor allows precise control of the CNC screw in each tightening process and records all important tightening process parameters in real time. Based on servo control technology, the electric CNC screw cutter ensures that the torque accuracy of millions of tightening assemblies is controlled within ±±1% of the standard deviation. 4. Four detection methods commonly used for static torque Torque (torque method, T) Torque+Angle (torque angle method, TA) Yield (yield point method, Y1/Y2) Elongation (bolt elongation method) 5, the attenuation of torque The essence of the threaded connection is that the connecting members are held together by the clamping force, so the essence of "attenuation" is the reduction of the clamping force after tightening. We can divide the reduction of clamping force into two parts, slack and loose. (figure 1) figure 1 relaxation: Slack means that as time increases, the clamping force of the bolts used to join the parts is reduced relative to the tightening force, but the bolts or nuts do not rotate. Loose: Looseness refers to the reduction of the clamping force, which causes the bolt or nut to rotate in the loose direction and further causes the clamping force to decrease. In this case, the bolt or nut may be completely loosened, which must be avoided in the connection involving personal safety. The occurrence of a phenomenon. Embed: High stress causes plastic deformation of the contact surface, which in turn leads to attenuation of the clamping force. figure 2 Multi-bolt connection: image 3 Figure 4 Possible reasons for U-bolt torque attenuation: (1) The leaf spring and the leaf spring base are both curved, and there is a slight gap after tightening. Treatment method: The contact part between the leaf spring and the leaf spring bracket is designed to be straight. (2) The deformation and friction of the leaf spring, resulting in: 1) reduction of internal elastic potential energy; 2) The friction between the spring pieces is gradually reduced. Treatment method: Pre-press the leaf spring. 6, the conclusion As threaded joint quality requirements continue to increase, it is critical to properly select and use tightening tools. The effective control of the bolt torque directly relates to the reliability, safety and sealing of the product (the parts used for thread sealing), and the quality of the product can be better ensured only if all the indicators can be guaranteed. Figure 5 Perforated Metal Sheet,Stainless Steel Metal Filter,Perforated Metal Filter Xinlong Wire Mesh Manufacture Co., Ltd. , http://www.hebwiremesh.com
