Improvement of Roller Bearing of Offset Press

The performance of the offset printing press plays a decisive role in the printing industry. The core component of the offset printing press is the printing cylinder. In the era of medium and low speed printing, the two bearings of the printing roller adopt sliding bearings because of the large aspect ratio of the sliding bearing support, low secondary contact, shock absorption, smooth transmission, favorable for eliminating printing ink bars, water bars, and long bearing contact lines. The rigidity of the drum can be improved, and when the drum is pressed and printed, the deflection is reduced and the printing pressure is ensured along the axial direction of the drum. Moreover, the sliding bearing has good craftsmanship, is easy to manufacture, and is easy to maintain and maintain. Therefore, under the low printing speed, it satisfies the needs of the printing process and is widely used.

After the 1980s, various countries began to improve offset presses. To improve its performance and increase its production efficiency, it first sought a breakthrough in improving the printing speed. Sliding bearings have a large friction coefficient, a large contact surface of the journal, a small gap between the friction pairs, poor lubrication and heat dissipation, and a high speed, it is easy to produce the shaft holding phenomenon. If the gap between the friction pairs is increased, the rigidity of the mechanism is reduced. The transmission accuracy is reduced, the ink sticks are easily produced during printing, and the sliding bearings become the bottleneck to increase the speed of the offset press. At this time, people begin to turn their attention to the problems of solving problems. Due to the improvement of the mechanical design and manufacturing process level, it also creates conditions for the sliding and rolling of the bearing of the offset press roller bearing. First, the rolling bearing used for the roller bearing has a small ratio of length to diameter, and the low side contact is changed to the high side contact. The drum body is rigid after being pressed by the printing pressure. Inadequate problems are solved.

In the past, people did not dare to lightly use rolling bearings. One of their main concerns was that the rollers were deformed under large printing pressure because the deflection curve of the rollers was drape-like, the middle deflection was the largest, and the middle of the cylinder was reduced relative to the printing pressure. Necessary printing pressure, network or text is more imaginary, and the printed products do not meet the standard requirements. With the help of computer finite element analysis and calculation software, it is very convenient and very accurate to optimize the design of the drum structure, optimize the design of the drum cavity structure, reasonably distribute the number of ribs, the number of plates, shape and cross-sectional dimensions, so that the overall stiffness of the drum is improved, ensuring The deflection after compression is within the allowable range. Followed by the improvement of the manufacturing process of the drum, the quality of the drum's material, hardness in the smelting, casting, heat treatment and other processes in the process to ensure the quality. Each roller of the printing press cannot only consider the static accuracy and rigidity, but also consider the dynamic precision and the accuracy after fatigue creep. The drum dynamic accuracy is not only taken from the mass distribution of the structure, but also related to the chemical composition of the metal structure of the roller metal, etc. Accuracy is related to stiffness. When measuring the radial runout and other geometrical accuracy, the roller is tested under almost static conditions. In fact, when the drum rotates at high speed, the runout error is different due to the difference in mass distribution and the difference in the metallographic structure of the material. Once again, bearing manufacturing, selection, assembly, and testing methods are complete to meet the design requirements. In particular, high-precision bearings, no matter whether they are imported or domestically made, do not contain any technical obstacles. In addition, the manufacturing precision of related parts that are influential has been improved, and supporting preparations for rolling bearings are well prepared. For example, if the accuracy of the gear on the roller is improved, the movement accuracy of the first tolerance group and the smoothness of the transmission of the second tolerance group have all reached level 4 and the same level as the aerospace gears. The holes of the machine frame and the end face are machined by high-precision CNC boring and milling machines. The gold cut is completed in a single fixture. The dimensional accuracy, shape error, and roughness meet the requirements of the over-positioning structure of the frame-type rack. After their quality is improved, the stability and reliability in the operation of the machine are greatly improved, and the vibration source is reduced. Demand for shock absorbers in the drum system decreased. Foreign advanced developed countries have achieved a great deal of successful experience, and more and more examples are used to learn from domestic machines. Heidelberg, Mitsubishi, Komori, and KBA have all generally used rolling bearing support, so domestic offset press rollers have been changed from sliding to rolling. The melons are ripe and ripe.

The roller bearing of the offset printing press is replaced by rolling, and the technical problem to be solved is firstly the selection of the bearing structure. At present, different manufacturers have different emphasis on the selection of the bearing structure. The understanding is not the same. The manufacturer represented by Heidelberg uses the bearing structure For the needle roller bearing, the bearing clearance is measured by measuring the size of the needle roller during assembly, and the group assembly is guaranteed; the manufacturer represented by Roland uses multiple rows of short-cylinder solid roller bearings together with the thrust bearing to compose the radial direction. The axial force adjusts the structure of control separately. The bearing working clearance is guaranteed by the bearing manufacturer with high precision; the manufacturer represented by Mitsubishi selects the tapered roller bearing. The axial force and radial force of the roller are also controlled by the bearing. Withstanding bearing, the structure is relatively simple, the bearing working clearance is ensured by the assembly adjustment, and the assembly technology requirements are relatively high. There are also domestic manufacturers choose the United States patented technology, large preload, micro-interference hollow cylindrical roller bearings.

Practice has proved that the above-mentioned several types of rolling bearing structures can meet the needs of offset presses, but they have their own characteristics, that is, theoretically, whichever way is suitable for the offset roller support, the specific choice of which way is to look at offset press manufacturing enterprises. Design ability, technology level, look at the level of understanding of technical personnel on the characteristics of various types of bearings, look at the status of enterprise equipment, to be able to make the perfect combination of objective conditions and subjective understanding, use of rolling bearings to focus on the control of the clearance.

Offset roller bearings are replaced by rolling, and the technical problems to be solved include bearing pre-tightening to adjust clearance and adjusting clearance between bearing pairs to improve system rigidity. The determination of the clearance after preloading during installation plays a decisive role in the final printing quality of the machine and the service life of the machine. In order to increase the rigidity of the bearing and reduce the noise during the operation of the rolling bearing, its working clearance should take a negative value.

Theoretical and practical experience shows that when the working clearance is at -10μm, the fatigue life of the bearing is the longest, the negative value of the working clearance increases, and the fatigue life decreases significantly. If the bearing temperature rises sharply, the effective clearance increases the negative value of the working clearance. Large, the installation should set aside a certain margin.