How to improve the precision of printing equipment frame structure

The overall structure of the printing press is based on two wall plates as the supporting base components. A large number of rollers, shafts, rollers and other components are installed between the two wall plates so that the continuously traveling substrates can be arranged among the arranged shafts, rollers, and rollers. Other functional agencies pass through. In the course of printing materials, such as tension control, paper feeding, deviation adjustment, water supply, ink supply, printing (overprinting), cutting, feeding, paper transfer, numbering, drying, cooling, glazing and various guarantees The printing process automatically completes the organization. Among them, the outside of a wallboard is equipped with various transmission parts to drive the rollers, shafts and rollers inside the wallboard to rotate, axially or intermittently, so as to achieve various printing functions. On the outside of the other wallboard, various operating mechanisms are installed to control the quality of printing and ensure the smooth printing. Therefore, under the premise of ensuring the processing quality of the wallboard, the quality of its assembly will directly affect the quality and accuracy of the entire machine. As the main basic part of the printing press, it also affects the quality and longevity of various functional parts during the entire printing process. Paying attention to the research of basic components is an important means to improve the intrinsic quality of the printing press. This article is prepared to start from the existing assembly positioning process method, through the calculation of positioning error, analysis of the causes of the positioning error of the main basic parts, and thus put forward several options for the new assembly positioning method to improve the assembly positioning accuracy and further improve the printing the quality of. At the same time, it also provides assembly methods and means for printing companies to provide large and medium-sized printing presses.

I. Calculation of Concentricity Errors Generated by Traditional Process Methods

The positioning method of the coaxial accuracy of the traditional basic parts mostly adopts the mandrel positioning method. Theoretically speaking, this method can be used to design the datum, the assembly datum, and the positioning datum. The datum can improve assembly accuracy. However, due to the presence of shape, position and size errors in the positioning holes of the wall plate, the positioning part of the mandrel also gives a given tolerance value. Therefore, when two wall plates are positioned using the mandrel, the existence of the gap will cause the mandrel to rotate flexibly. Concentricity error. Obviously, with the widening of the distance between the two wallboards, the coaxiality error value and the wallboard spacing are proportional to the size of the fit gap. The error of coaxiality caused by the presence of gaps in large-span printing machine wallboard can not be ignored. Although the relative positions of the rollers, shafts, and rollers can be determined from the common axis after the assembly of the rollers, shafts, and rollers, it seems that the impact is not significant. However, many transmission, control, and automatic control parts are in poor working conditions. More important is poor accuracy.

To establish the relationship between gaps, wall spacing and concentricity errors, first propose the following constraints:

1. The lower plane of the wall plate is the support reference, and is also the guiding reference during processing. Therefore, it can be considered that all co-located holes on the two wall plates are the same as the supporting reference height dimension. When assembling, the horizontal position of the two wall plates is determined by the positioning core. Axis positioning determination;

2. It can be imagined from an intuitive point of view that the position that produces the maximum concentricity error is: one end of the hole is in contact with the positioning mandrel to the diagonal, and the other is in contact with the mandrel in the inner side of the hole. Theoretically, this When rotating the mandrel should also be flexible; or vertical processing in the worktable on the co-working (also can be divided into processing), so that the two walls of the hole axis in the same direction, but the angle of the plane of the wall plate is different, which reflects The consistent accuracy of the pull shaft (pull beam) parts;

4. Generally speaking, the two wallboards have the same hole diameter. In order to make the deduced relationship have universal significance, the two corresponding holes are not equal.

Second, coaxial error analysis

The concentricity errors produced by the positioning assembly of the three basic components of the printing press in accordance with the current assembly process can be accounted for using the three relationships previously deduced. (1) The formula is a general calculation formula of the coaxiality error, but it does not include the error caused by the consistency of the pull shaft and the pull beam. (4) is a simplified calculation formula of the coaxiality error, that is, the variables in the equation are inconsistent with the reality of the printing press. (6) The formula is a comprehensive calculation formula of the coaxiality error, that is, the formula that considers both the factors of the gap and the consistency error of the pull shaft and the pull beam.

The same kind of situation can be applied to the analysis of the coaxiality error:

1. Consider only the concentricity error caused by the influence of gaps and positioning mandrels;

2. Take into account the concentricity errors resulting from gaps and consistency;

3. Use the maximum value method to find the maximum concentricity error;

4. According to the method of total quality management, consider the normal distribution of errors generated by processing and assembly, and obtain a reasonable concentricity error.

When the wall plate is positioned with the positioning mandrel, the operator has to rotate the mandrel to make it flexible. When the two wall plate shaft holes are processed to prevent measurement errors, the operator often controls the aperture at the lower limit, and the diameter of the positioning mandrel is controlled at the upper limit. The actual coaxiality error is smaller than the above calculation. According to the principle of total quality management, the maximum concentricity error calculated as above is only 3 parts per million (the standard deviation is controlled within 6σ). The process capability index of this positioning method is relatively high, because there are fewer factors that affect the positioning accuracy. If the process capability index cp=1.33, the previous two calculation results can be used to calculate the actual achieved coaxiality accuracy.

Due to the existence of the gap between the wall plate hole and the positioning mandrel, there is a dimensional uniformity error of the tension shaft and the tension beam. This assembly positioning method generates a large coaxial error. From the calculation results and relational derivation process, the following conclusions can be drawn.

1. The main cause of coaxiality error is the gap between the wall plate hole and the positioning mandrel. With the wear of the positioning mandrel, the coaxiality error will continue to increase.

2. The consistency of the pull shaft and the pull beam also affects the accuracy of the coaxiality, but it is a minor factor. In the actual processing, the measuring method for measuring the consistency accuracy of the card gauge is not desirable. Experiments show that the measurement accuracy of the tube is only about 0.4 mm due to the deflection of the tube, which will increase the influence on the coaxiality. If each piece of double-sided milling is used, the accuracy is improved by 60%, and the consistency accuracy can be controlled within 0.04mm. At this time, the card board only plays the role of controlling the uniformity of the size of each batch of parts. Therefore, this paper no longer studies the problem of further improving the consistency accuracy.

3. It can be seen from the relational equation that there is a direct relationship between the coaxiality error and the wall plate spacing l and the wall thickness b. When the wallboard spacing is small or the thickness of the wallboard is very large, the accuracy of the coaxiality can be ensured according to the formula of the previous formula or the current core axis positioning method can be adopted. The wall plate made of steel plate material has a large error due to its small thickness.