Elimination of offset paper torn paper
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Offset printing machines, whether it is a sheetfed offset press or a two-color, four-color offset press, will have different degrees of wear after running for several years, especially for several open cam cams, pads and teeth. Parts such as the seat and the receiving paper are easily worn, and the precision thereof is lowered, so that the paper transfer during the printing process cannot be performed normally. The manifestation of the failure is torn at the edge of the paper, so that the second color can not be carried out normally, and the torn edge of the paper also affects the neatness of the paper, causing the loss of the printed product in serious cases. In the actual work, when the paper is torn at the time of receiving the paper, it is necessary to comprehensively analyze the paper, treat it differently, and correct the fault.
1. Reasons for the phenomenon of tearing paper at the front of the paper
1.1 The impression roller has a long connection time with the delivery tray. Properly shorten the delivery time of the two sets of cavities.
1.2 The impression cylinder is different for opening and closing the teeth. Adjust the impression cylinder to open and close.
1.3 The impression cylinder and the delivery tray are not at the tangent point or are offset from the tangent point. Adjust to the tangent point location.
1.4 The delivery of the teeth is not the same. Adjust the makeup paper row to open and close.
1.5 The edge of the receiving tooth is too close to the edge of the impression cylinder or collide with the edge of the impression cylinder. Adjust the distance between the edge of the receiving tooth and the edge of the impression cylinder, generally about 1mm.
1.6 The impression cylinder opening cam or the delivery tooth is worn out, which causes the opening of the opening to be small and touches the paper. Replace the impression cylinder or the delivery dog with the open cam.
1.7 tooth squeegee paper hits the paper bar or other obstacles during the transport to tear the paper edge. Check the above points.
1.8 In addition to the adjustment error of the offset printing machine and the improper transfer of the paper, which causes the tearing of the delivery opening, the quality of the paper itself is also prone to the phenomenon of tearing the paper by the mouth. If the paper is poor in flexibility, the paper storage time is too long, the sunlight is shining, the paper library environment is dry, etc., the paper becomes yellow and brittle. Such paper printing on the paper will also cause the paper to tear the paper.
2. Reasons for the phenomenon of tearing of the paper mouth during the normal printing process and the elimination
In the normal printing process, if there is a phenomenon that the paper is torn at the mouth of the paper, first look for the cause of the problem and carefully check the tearing of the paper. Generally speaking, the tearing of the mouth is nothing more than three phenomena: First, the mouth of the paper is continuously torn and the position is unchanged. Second, not every sheet of paper is torn apart, but a few sheets of unbroken paper are spaced in the middle, and it is regular. Third, the break of the paper's mouth is large and small, and it breaks when it is good, and there is no regularity.
Now analyze the causes and troubleshooting methods of the above three types of faults as follows:
2.1. During the offset printing process, the paper flaps are regularly torn, and the number of sheets in the middle interval is just the number of the paper feed trays.
This situation is generally caused by improper adjustment of the delivery tray.
Solution: Open the offset press and carefully observe whether the tension of each tooth of the receiving row is the same, then adjust it, then drive the paper to see if there is any tearing.
2.2. The edge of the paper is continuously torn and the position remains the same.
If this happens, we have to find the cause on the transfer paper and the big tooth of the roller. First, the slow car carefully observes the process of handing over the paper and the large teeth of the roller to see if the paper edge is torn due to the slow toothing time or insufficient opening of the tooth.
Solution: Check if the teeth of the transfer paper are worn out. If it is worn, it needs to be repaired or replaced with new ones, and carefully adjusted. The requirement is that when the paper is handed to the large cylinder of the impression cylinder, the paper is delivered. The distance between the paper and the large teeth should not be more than 3mm.
Secondly, since the large tooth base of the drum is rounded by the top wire, the opening of the large tooth of the drum is insufficient. When the paper is transferred to the large tooth of the drum, the paper edge hits the drum and tears.
Solution: If only one or a few of the sockets are broken by the top of the top wire, repair welding can be performed on the machine. If the top is bad, remove the new one.
Thirdly, the connection between the toothed shaft of the roller tooth and the pulley frame is loose, which causes the tooth of the large tooth of the drum to be slow or the opening of the tooth is insufficient to tear the paper edge.
Solution: First check if the pin at the joint is loose or cut. If it is only loose, it can be re-pinned. If it is cut, you need to re-fit the new pin.
Fourthly, the distance between the tooth pad of the transfer paper and the edge of the impression cylinder is improperly adjusted. The distance is too close, so that the transfer paper pad is opposite to the edge of the impression cylinder, causing the paper edge to tear, and the distance is too far to make the impression cylinder crepe paper. When the paper edge is torn.
Solution: Carefully adjust the distance between the transfer pad and the edge of the impression cylinder. Generally, the distance between the two is adjusted to 0.5 mm. Card paper should be printed 2 to 3 times the thickness of the paper.
Fifthly, the open teeth of the delivery tooth are worn, and the opening time of the delivery tooth is slowed down, and the paper is torn due to the too small opening distance.
Solution: Remove the open bumps and repair or replace them with new ones.
3. The paper is not regularly broken at the edge of the paper, and the width is narrow when it is broken.
This phenomenon is generally caused by improper adjustment of the paper feeder or the front gauge. The reason should be found on the paper feeder. 1 Carefully observe whether the tape tension of the paper feeder is consistent; 2When the offset printing machine starts driving, see if the paper feeding belt pulley can rotate flexibly; 3 The offset printing machine slows to see if the paper reaches the pre-regulation time is appropriate, general requirements When the current gauge reaches the paper-receiving position, the distance between the paper edge and the front gauge is 8-10mm. If it is not suitable, it needs to be adjusted. 4 Check whether the height of the front gauge meets the requirements. The general requirement is that when the current gauge reaches the paper-receiving position, it can just put three sheets of paper to be printed, and a slight resistance is appropriate when pulling.
In summary, in the case of troubleshooting the tearing of the paper, it is necessary to pay attention to the transfer paper, the large tooth of the drum, the tooth pad of the delivery paper, and the transfer between the teeth and the teeth must be reasonable, and must follow the mobility relationship table on the machine manual. In the request data to adjust, the height of the teeth of a row of teeth must be adjusted consistently. The opening and closing time of each tooth must be the same as the opening and closing of the opened teeth. The bite force of each tooth was tested by a paper strip to balance its bite force.