Fault analysis of overprint inaccuracy of the hott

2022-09-23
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Failure analysis of inaccurate overprinting of printed products (III)

reason 11: the bottom swing paper transfer tooth is higher than the paper conveyor

solution: adjust its position correctly, and the paper delivery tooth pad should be level with or slightly lower than the paper conveyor

the reason for the inaccurate overprint after cutting off the power supply is that the improper adjustment of the machine parts prevents the accurate positioning of the paper. In addition, it should be noted that whether it is an up swing or a down swing, the height of the paper feeding teeth should be adjusted according to the height of the paper feeding teeth, and then the height of the front gauge should be adjusted according to the height of the paper feeding

cause 12: the paper feeding time of the paper feeder and the falling time of the front gauge are not matched properly

solution: the paper on the feeding board should be 3~5mm away from the specified position line as soon as the previous gauge reaches the positioning position

reason 13: the paper is bounced back when positioning at the front gauge

solution: the position of the brush and brush wheel on the paper board should be tangent to the back edge of the paper; The height of the teeth at the front gauge is too low, and the positioned paper is pushed back. It is suggested that the tooth opening height should not be less than 200, and the height of the tooth opening boss can be adjusted; When printing thick paper, especially paper jam, you can consider using paper pressing balls

reason 14: the paper reaches the previous specified position line ahead of the previous positioning time

solution: the paper feeding time of the paper feeder and the falling time of the front gauge are not matched properly. The correct matching time is when the front gauge reaches the positioning position. The position of the paper on the paper feeder is 3~5mm away from the front specified position line

(1) J2205 can adjust the matching time of relative motion by adjusting the flange under the transmission surface of the paperboard conveyor; Heidelberg SM series can adjust the fitting time by changing the gear meshing relationship in the transmission box of the paper conveyor

(2) generally, the phenomenon that the paper has reached the front specified position line or exceeded the front specified position line before the front gauge reaches the positioning position is called "paper unloading fast"

reason 1: the paper stack is too high, even higher than the top of the front paper block

solution: the height of the paper stack can be reduced by adjusting the flying height or inserting wedges. See the solution to cause 3 in (1) for the adjustment requirements

reason 2: the blowing volume of the loose paper blowing nozzle is too large

solution: if the paper is unstable on the paperboard, it is easy to drift, or drag out the paper that is blown too high when the paper delivery suction nozzle sends out a piece of paper

reason 3: the paper delivery suction nozzle is too low

solution: caused by improper adjustment. In particular, if the damping hole on the paper delivery suction nozzle of sz206 paper conveyor in domestic printing machines is blocked, it will cause the paper delivery suction nozzle to fall and not lift up. Adjust the position of the paper delivery suction nozzle

reason 4: the paper pressing wheel falls too early

solution: adjust the coordination relationship according to reasons 6 and 8 in (1)

reason 5: the pressing wheel and brush wheel on the paper board are too tight

solution: relax appropriately

reason 6: the air pressure of the vacuum paper conveyor is too low

solution: the paper feeding time of the pneumatic paper conveyor is not matched with the falling time of the front gauge, so that the paper reaches the front specified position line ahead of the positioning time of the front gauge

see the solution of cause 14 in (1) for the adjustment method

cause 7: paper skew caused by fast or slow paper unloading on the body side or transmission side of the paper

the solution also points out the direction for the development of lightweight and green automotive materials. Generally, in this case, you can directly observe the serration between the edges of the running paper on the paperboard. The most important thing to prevent paper skew is to pay attention to the position of each part of the paper feeding, and the adjustment should be carried out symmetrically along the center line of the machine. For example, the suction of the left and right suction nozzles of Feida should be consistent, the tension of the paper conveyor belt should be consistent, and the falling time of the paper pressing wheel should be consistent. From the beginning of paper feeding to the end of printing, any group of parts that should be symmetrical can be adjusted asymmetrically, which may lead to inaccurate overprint

in addition, in the production operation, attention should be paid to the adjustment sequence of the machine: the first embossing roller or the first paper transfer roller - paper feeding teeth - paper feeding table - front gauge - time of arrival of paper - flying time of paper feeding, the first embossing roller - the first paper transfer roller - the second embossing roller. It can be seen that the first embossing cylinder or paper transfer cylinder is the adjustment benchmark of the whole machine. Adjusting in this order can ensure the accuracy of the relative relationship between the parts of the whole machine

the following points need to be paid attention to in the adjustment:

① the transmission cam of the paper pressing wheel swing shaft on the paper feeding table is a static stroke at the low point. At this time, there is about 0.15mm gap between the roller on the swing rod and the cam to ensure the smooth movement during paper receiving

② the front gauge is also a static range when positioning, and there should be corresponding methods when adjusting (many machines adjust the limit nut) to ensure stable positioning

③ when adjusting Feida, it is suggested to adjust the height and other parts of Feida on the premise of ensuring that the paper stack is flat (by inserting wedges and padding paper tapes), so as to ensure that the fenstora ENSO of paper can turn waste into packaging materials and deliver smoothly

④ when the paper is loose, you can stack less paper on the paper feeding table each time to avoid excessive concave amount of the paper tail under the pressure of the presser foot, resulting in paper feeding failure and inaccurate overprint

2. Inaccurate overprint fault caused by inaccurate positioning of front gauge and side gauge

paper transfer tooth is also the key to ensure accurate overprint. Here are some common causes of failures in production

reason 1: the upper swing front gauge is too high or the cover gauge on the lower swing front gauge is too high, resulting in the front edge of the paper being easy to tilt when positioning

solution: refer to the solution of cause 10 in 1 (1) for the correct location

reason 2: the falling time of the front gauge is incorrect and cannot be positioned correctly

solution: this kind of situation is rare, sometimes after the machine has just been overhauled. The conventional adjustment method is to pull out the locating pin on the front gauge cam and change the angle position of the cam by adjusting the position of the long hole. After the adjustment is completed, be sure to re drill the locating pin hole and drive in the locating pin to prevent the position change in the future operation. Readjust the falling time by changing the position of the cam

reason 3: if the swing up front gauge uses the reed for empty tension detection, it is easy to make the reed too hard to hinder the positioning of the paper

solution: generally, the reed used in domestic printing machines is not a standard part. From a technical point of view, it is easy to have uneven thickness. In such cases, you can use sandpaper to grind it thin

reason 4: foreign matters such as paper wool and ink residue on the wheel or baffle will cause the paper to not reach the positioning position smoothly

solution: remove the paper wool on the wheel or baffle. Foreign matters such as ink residue

reason 5: the side gauge cover is too high, causing the paper to be pulled too far, or too low to be pulled in place

solution: the correct height should be the thickness of 3 thin papers or the thickness of thick papers plus 0.2mm

cause 6: the spring is too tight, causing the paper to be pulled too much or too loose and not in place

solution: adjust according to the thickness of the paper

the reasons mentioned in 3, 4 and 5 are all inaccurate overprint faults that are easy to occur with mechanical side gauges, while pneumatic side gauges are easy to be blocked by paper wool, so they should be cleaned frequently

reason 7: the side gauge fell too early, causing the paper to be pressed by the side gauge before completing the positioning of the front gauge

solution: according to the angular relationship of the machine, adjust the side gauge to the accurate falling time, and wait until the paper is correctly positioned by the front gauge before falling and pressing the paper (or the vacuum side gauge starts to suck the paper). When adjusting the side gauge, it should be noted that the side gauge should not be lifted until the paper delivery tooth catches the paper, so as to avoid causing the paper to be in a free state on the paper conveyor. There is a phenomenon of "three ignore" and drift

reason 8: the side gauge was raised too late

solution: when the paper delivery teeth have begun to hold the paper and leave the cardboard, if the side gauge is still not raised, there will be a quarrel, sometimes causing the paper to slide backward, resulting in inaccurate overprint. The lifting time of the side gauge should be before the paper delivery teeth take the paper and leave the cardboard conveyor

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