Adjustment VIII of the hottest paper feeding devic

Adjustment of paper feeding device (VIII)

analysis and elimination of three paper feeding faults

stable paper feeding machine and accurate paper feeding are important conditions to ensure the quality of printed matter. Due to the frequent changes of the substrate, the structure and action of the paper feeding part are more complex, and the causes of many faults are not easy to make correct judgments immediately, which often makes it difficult for the operator to deal with. Paper feeding faults usually include: empty sheet, double sheet, multiple sheet feeding skew, paper feeding fast and slow, etc. Except for the paper, most of the faults are related to the adjustment of the separation mechanism of the paper

1. Faults such as empty sheet

are the most common faults that operators are most likely to find. The causes of the faults:

(1) the paper is uneven, making the front and back of the paper stack too low

(2) the paper delivery suction nozzle is too low

(3) the paper separation suction nozzle is too high

(4) adhesion on the back of the printed color

(5) the automatic lifting of the paper stack is faulty

(6) the paper retaining brush or paper pressing steel sheet is too low or extends too much into the paper stack

(7) the blowing and suction air volume is too small

through the analysis of the causes of the empty sheet fault, it can be seen that the height adjustment of each suction nozzle and the air volume are the key. In addition, the stacking operation level is also very important. At the same time, the flatness of the paper stack should be adjusted through a wooden wedge

[expert tips]

on the one hand, the wooden wedge is used to adjust the flatness of the paper stack, and on the other hand, it can be used to adjust the height of the paper stack and control the rise of the paper stack, so the operator must use the wooden wedge well

2, double or multiple sheet

this fault is a fault that makes the operator feel "afraid" during the paper feeding process. Because it is not only harmful, but also extremely destructive to the machine. Thousands of "stuck car" accidents are basically caused by two or more paper feeding sheets. The reasons for this failure are:

(1) the edge of the paper is tilted up and down, the cutting size of the paper is different, and the pile of paper is uneven

(2) paper has static electricity

(3) the rise of paper pile is too large or unstable

(4) the components of the separation mechanism are improperly adjusted, mainly including: the paper retaining brush is too high; The paper blocking brush is too low or the extension is too small; Insufficient paper separation and blowing; The height distance of the paper separating blowing nozzle is incorrect or the rubber band is improperly selected; The paper pressing blowing nozzle (called the paper pressing foot if the paper pressing has no air blowing) presses too little paper

from the above fault causes and adjusting parts, the substrate is the main contradiction. The adjustment method of the separation mechanism varies with the substrate. If the paper has strong static electricity, no matter how to adjust the parts of the separation mechanism, it is useless. Only hang the paper to wet it or increase the air humidity. Generally speaking, when printing thin paper, there is a high probability of double or multiple sheets

print thinner paper, especially paper below 60g/㎡. Due to its poor strength and light weight, the edge of the paper is fluffy and wavy when the paper blowing nozzle blows the edge of the paper. When the paper separating suction nozzle sucks up the first sheet of paper, it is difficult to restore the fluffy paper edge to a straight free state. When pressing the foot, it is easy to insert under the second or more sheets of paper, resulting in double or more sheets

in view of the above situation, make the following adjustments to the relevant machines of the separation mechanism:

(1) appropriately reduce the air volume of the loose paper blowing nozzle to ensure that the loose paper blowing nozzle only blows the top several sheets of paper stably at a time

(2) the distance between the paper separating suction nozzle and the paper surface is not appropriate, otherwise when it moves downward to suck the paper, the air between the upper and lower papers will be squeezed out, and the two papers will be sucked together

(3) the presser foot should be pressed more without touching the edge of the paper. If it is a presser foot with air blowing, the amount of air blowing can be increased appropriately

(4) for tablet pressing, press down and extend the brush inward as far as possible without affecting the paper separation suction nozzle. Be sure to adjust the double controller to avoid the "dead car" accident

[expert tips]

when printing coated paper and offset paper, the adjustment method of paper feeding is different. The surface smoothness of coated paper is different from that of offset paper. The surface of the coated paper is smooth, and the friction between the loose paper blowing nozzle and the paper surface is small. During printing, the paper can be blown up (for CD102 machine, the side air blowing can be blown up, and the air blowing of the presser foot and the front air blowing can be increased), the distance between the paper delivery suction nozzle and the paper can be reduced, and even the paper delivery suction nozzle can keep in contact with the paper all the time, and there will be no skew or double sheet phenomenon. The surface of offset paper is rough. If the distance between the paper delivery suction nozzle and the paper is too small, it will produce large friction and produce skew cobalt. At present, the consumption of cobalt in the lithium battery field has accounted for 60% of the sheets. Even for how to select the equipment, please consult the technical personnel of star to affect the following paper and produce double sheets. Therefore, it is necessary to increase the distance between the paper delivery suction nozzle and the paper before suction, and the suction volume is required to be large and uniform

[case]

due to the loss of the current production factor cost of the double sheet detector of sz206 paper conveyor in a factory, the whiteboard entered the rubber pressing roller, causing the "stuffy" fault. The operator took many measures, but failed to make the machine rotate. Finally, use the injection needle to inject water to expand and soften the paper fibers, and then use the hacksaw blade to pull out the whiteboard

3. Paper feeding skew f

the parts on the paper feeder basically follow the principle of symmetry. For example, the brush, tablet pressing, pressing block, blowing nozzle, suction nozzle, paper receiving wheel, etc. are all distributed in pairs, and the front, rear, left and right positions are symmetrical, with the same contact pressure. Obviously, the blowing and suction air volume should also be uniform and symmetrical, which requires that the paper surface is flat, the front mouth and side edges are flush, and there is no resistance between the papers. However, in actual production, this ideal state is often difficult to achieve. First, due to the electrostatic attraction between the papers, the ink adhesion, and the uneven local resistance formed by the camber of the paper surface, the transmission of the paper is prone to skew. Second, the left and right sides of the front mouth of the paper are bent differently. Third, the left and right of the front paper retaining teeth are not in a straight line. Fourth, there are many parts of the separation mechanism, and the action is complex, so it is inevitable to shake and unstable in the process of paper separation and delivery. Fifth, there is deviation on both sides of the paper delivery wheel adjustment. These factors can easily cause paper skew and are difficult to overcome. Therefore, some machines, such as CD102 machine, do not have an adjusting knob above the separation mechanism, which can correct the paper skew

[case]

a factory has an imported split multicolor offset press. When printing with a positive or large offset, the paper feeding is normal. However, the paper feeding is skewed every time the four split movable parts are replaced

[case analysis]

this situation often occurs in many printing plants, which is caused by the small number of paper openings and the poor adjustment of the paper feeding mechanism. The key is the uneven distribution of the force on the paper by the paper delivery wheel (two) and the control wheel of the double sheet detector

4. Paper feeding is fast and slow or jitters

the causes of such failures are in addition to the broken pin connecting the paper conveyor and the host, the wear of gears or other parts, and the static electricity of the paper. Improper adjustment of the paper transfer wheel is also the main factor causing the paper feeding to be fast and slow. The correct falling time of the paper transfer wheel is that the front mouth of the paper sent out by the paper transfer suction nozzle crosses the contact point between the paper transfer roller and the paper transfer wheel by 5mm. At this time, the paper transfer suction nozzle is ready to put paper, The paper delivery wheel should press the paper in time, and the handover should be completed in a short time, but it should not be out of control. If the falling of the paper delivery wheel presses the paper too early, and the paper delivery suction nozzle is not loosened, forming a "paper grab", when the paper delivery suction nozzle loosens the paper, it will cause instability or shaking of the paper. On the contrary, if the falling time of the paper delivery wheel is too late, the paper is not controlled in time when the paper delivery suction nozzle releases the paper, and there will be an obvious pause in the transportation of the paper

there must be appropriate contact pressure between the paper transfer wheel and the paper transfer shaft. If the pressure is too small and the friction is not enough, the paper between the paper transfer wheel and the paper transfer shaft will slide relatively, especially when the paper has static electricity or the paper transfer suction nozzle has excess suction, the paper feeding speed will change significantly. The so-called residual suction phenomenon is that the paper separation suction nozzle still sucks the paper when the paper delivery suction nozzle increases the paper forward. The paper delivery suction nozzle sucks the paper on the way back and pulls it back.

[case]

during the printing production process of a factory, the paper feeding speed sometimes changes, mainly because the first few sheets of paper fall slowly when the paper feeder is turned on and the air pump is turned on, while the last sheet of paper falls quickly after the air pump is turned off

[case analysis]:

this phenomenon is obviously the influence of air suction. When there is air suction, the speed under the paper is slow, and when there is no air suction, the speed under the paper is fast, indicating that there is residual suction at the paper delivery suction nozzle after the air pump is started, and after the air pump is turned off, there is no air suction, and there is no residual suction

treatment method: clean the air circuit