Analysis of the reasons for the overall displaceme

2022-10-23
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Analysis of the reasons for the overall positioning of carton printing

the printing quality of carton printing machine is generally understood as two aspects. On the one hand, it is the clarity of printing, including the consistency of color depth, no adhesion of patterns, no ghosting, and no bottom leakage. On the other hand, the overprint accuracy of multicolor printing should generally be within ± 1mm, and a good printer can reach ± 0.5mm or even ± 0.3 mm. In fact, there is also a very important printing quality index of the printing machine - the overall positioning of printing, that is, several colors are accurately colored, but they are inconsistent with the spacing of the reference edge of the paperboard, and the error is large. Because this quality index of general cartons is not strict, it is easy to be ignored. If the overall deviation exceeds 3mm or 5mm, the problem is more serious

regardless of chain feeding or automatic feeding (push back or leading edge feeding), the reference edge of the overall printing travel is perpendicular to the cardboard conveying direction, because the other direction (cardboard conveying direction) is not easy to produce the overall travel (unless the cardboard runs sideways). This paper will analyze the reasons for the overall positioning of the automatic paper feeding printing machine with the push back mode

automatic paper feeding printing machine cardboard conveying is to push the bottom piece of neatly stacked cardboard forward between the upper and lower conveying rollers, and then forward from the upper and lower conveying rollers to the printing department. Repeat this to complete the automatic paper feeding. Analyzing the transportation process of paperboard can help us find the reason for the overall displacement of printing

first of all, during the paper pushing process, there should be no large accumulated gap in the transmission chain of the pushing board. The automatic paper feeding printing machine pushes the paperboard in a reciprocating linear motion. Most manufacturers use crank (slider) guide mechanism plus rocker slider mechanism. In order to make the mechanism light and wear small, the slider of the crank slider guide mechanism is a bearing with the joint efforts of everyone. Due to the large gap between the bearing and the two sliding plates, the uncertainty of the paperboard pushing movement is caused, resulting in the paper feeding error and the overall displacement of the printing. Therefore, how to ensure that the bearing rolls between the two sliding plates of the guide rod without large clearance between the bearing and the two sliding blocks is the key. If the double bearing structure is adopted, it will be deleted from S. no matter whether the bearing moves down or up along the sliding plate, it can ensure that the bearing can make pure rolling without clearance between the two sliding plates, so that the mechanism is light, with small wear and clearance elimination

the connection between the guide rod and rocker and the shaft is easy to loosen due to the alternating load, which is also the cause of the paper pushing error caused by the gap. Other mechanisms in the paperboard pushing drive chain are driven by gears, which can improve the machining accuracy of gears (such as gear grinding and honing), improve the center distance accuracy of each pair of gears (such as machining wallboards with machining centers), reduce the cumulative clearance of transmission, improve the accuracy of paperboard pushing, and thus reduce the overall displacement of paperboard printing

second, the moment when the pushing board pushes the board into the upper and lower paper feed rollers is actually an instantaneous acceleration process of the board speed from the linear speed of the pushing board to the linear speed of the upper and lower paper feed rollers. The instantaneous linear speed of pushing the paperboard must be less than the linear speed of the upper and lower paper feeding rollers (otherwise, the paperboard will be pushed and bent). Data will be provided to predict how small the results of these innovations are. The ratio and matching relationship of the two speeds are very important. It directly affects whether the paperboard slips at the moment of speed-up and whether the paper feeding is accurate, thus affecting the overall position of printing. This is precisely what printing machine manufacturers do not notice

when the speed of the host machine is constant, the linear speed of the upper and lower paper feeding rollers is a constant value, while the linear speed of the cardboard pusher is a variable, from zero at the rear limit position to zero at the front limit position, from zero at the front limit position to zero at the reverse maximum position, forming a cycle. The linear velocity formula of the pushboard can be deduced by analytical method

V=nπcos( α-α 2)cos α 2cos α 1 ①

in the formula: V is the linear speed at the end of the guide rod (that is, the linear speed of pushing the paperboard)

n is the rotation speed of the crank ob of the plastic granulator, which is also quite serious to the environment, and it is a known quantity

from the formula ①, it can be seen that V is a variable, which varies with the position of point C( α 2) different. The different speeds of pushing the paperboard at different positions can be obtained through calculation. According to the proportional relationship between the linear speed of the paperboard pushing and the linear speed of the paper feeding roller, determine the linear speed at which the paperboard is pushed into the upper and lower paper feeding rollers, and then determine the best position of the paperboard pushing at this time

of course, there are other factors that affect the overall positioning of paperboard printing, such as the curvature of the paperboard, the surface roughness of the paperboard, the moisture content of the paperboard, and whether the gap between the upper and lower paper feeding rollers is appropriate

source: China design and printing

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