What is 1
The paper feeding mechanism of the sheet-fed offset printing press is one of the key components of the whole machine. Whether considering the printing speed or the registration accuracy, its performance will determine the level of the product. Because a sheet-fed offset press needs to feed discontinuous sheets of paper into the printing unit, the paper feeding system mostly uses a reciprocating mechanism. With the increasing speed, the increasing accuracy of registration accuracy and the continuous reduction of noise limit, the design and manufacture of paper feeding system is becoming more and more difficult, and the degree of attention is getting higher and higher. At present, domestic offset printing presses are no match for imported ones, and they are largely lost to the paper feed system. For imported machines, for example, start-up, the general speed is 15,000 prints / h, and the noise does not exceed 85 decibels, giving people the feeling of lightness, no impact, stable machine, low vibration, and long cam roller life. The speed of the domestic machine is difficult to break through the speed of 10,000 prints per hour. When the speed reached about 10,000 prints at the time, the heavy contact sound of the paper feeding system parts made the palm of the hand sweat, and the speed of the full sheet machine was of course lower.
2 why
How does the noise of the feed system of the sheet-fed offset printing machine arise? This starts from the principle of the machine structure. The feed system of the sheet-fed offset printing machine, regardless of whether it is domestic or imported, generally adopts the centering hem plus front pass roller mode. After the paper passes the side rule and the front rule position at the iron table, the paper transfer arm will hold the paper. At this time, the front roller rotates clockwise, the active cam gradually moves to a small diameter, and the swing rod and connecting rod swing cam Under the action of the large spring thrust, it is ensured that the rolling ball always adheres to the active cam, and at the same time, the high point of the opening and closing tooth protrusion on the swing cam pushes the gripper to close, and the paper is gripped and conveyed to the paper transfer roller. Practice has proved that no matter how high the speed of the machine is, as long as all the rollers are not separated from the cam surface and do not fly over, there will be no impact phenomenon and no over-limit noise, so the problem of eliminating noise in the paper feed section is to make every effort to make the roller stick Tightly convex contour surface. [next]
3 What to do
The measures to ensure that the roller is close to the surface of the convex contour line are as follows: ①Increase the force of the main push spring. Because as long as the force of the main push spring is not enough to overcome the rolling ball climbing resistance when the ball is closed, it is not enough to overcome the mass of the swing rod and the connecting rod itself, and it is not enough to overcome the force generated by the system motion acceleration and the friction torque of the moving parts such as the swing cam. The ball will break away from the convex contour. ②Adjust and change the swing lever. Adjust the lever ratio of the swing cam to make the lever group of the entire system be in the state of labor-saving lever, that is, lengthen the swing arm length and shorten the center distance of the swing cam pin hole, so that the connecting rod stroke lengthens under the condition that the active cam guarantees the same rotation angle When the rotation angle of the swinging cam is increased, and the opening and closing tooth angle is unchanged, the lifting angle of the opening and closing tooth cam is increased, and the cam is gentler, that is, the pressure angle is reduced. ③All swing rods, connecting rods and swing cams are made of lightweight materials and lightweight structures to reduce the inertia during high-speed operation and reduce their positive pressure on the supporting shaft. ④The support of each swinging part and rotating part adopts rolling bearing support, which can greatly reduce the running friction resistance and reduce the power consumption of the main thrust spring. ⑤ The cam curve is optimized, and a continuous function is used in the lift section, so that the acceleration and the amount of acceleration change are both small and continuous, and the impact of the motion characteristics is minimized. ⑥ Reduce the opening angle of the swing arm opening and closing, as long as the opening angle meets the need for gripping paper, the smaller the opening width of the gripper, the better. If the opening angle is small, the opening and closing tooth cam lift is small, and the cam is gentler.
4 effect
The CS102 high-speed pair developed by Jiangsu Chang? N Group is a high-tech new product that is going to the world. After a lot of repeated calculations, simulation demonstrations, and practical demonstrations in the design of the paper feed system, the cam curve is finally optimized. The change of acceleration is also continuous. The connecting rod swinging cam adopts light aluminum alloy, and the opening cam cuts the mesh structure to reduce the overall quality. At present, the quality of this part is only 3/5 of the same type of machine, and the connecting rod swinging rod size series is optimized. Adjustment, the transmission angle is increased, the power-increasing ratio is increased, and the bearing motion pair adopts rolling support. After taking these measures, the machine's running speed, running accuracy and running stability have made a qualitative leap. When the printing speed reaches 15,000 prints / h, the noise does not exceed 85 decibels, which is no different from foreign imported machines, even better than some imported machines. The sound is round, and it is a model that can really compete with foreign machines in quality.
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