During the operation of the offset press, failure of its positioning components can cause various problems in the printing of the product, and the most direct result is that overprinting of the printed product is not allowed. The fault location performance of the positioning component is quite numerous, mainly in the following aspects.
1 Improper paper feed time
Improper paper feeding time refers to problems such as early arrival or late arrival of paper, incorrect positioning time, and insufficient positioning time. This situation is actually caused by the non-synchronization of the feeder with the host. But sometimes the machine adjusts to synchronize the paper feed time change phenomenon, it is necessary to check whether the machine itself is faulty, such as Feida's bearing is damaged, the cardan shaft pin is broken, because these parts are relatively easy Worn. Solution: Check the time before the front edge of the paper reaches the front gauge. Generally, when the current gauge reaches the delivery board, the edge of the paper bite should be 4mm to 6mm away from the specified front surface. Keep this distance in order to stabilize the front gauge; check the input. Whether the tape is tight or not, if it does not feel right, adjust the tightness according to the situation; check whether the feeder pin and the cardan shaft connection pin are damaged, and replace it in time if it is damaged; check if there is a selection object on the paper supply board to block the paper. Conveyor, especially the interface part of the feeder belt.
2 Horizontal overprinting is not allowed
Positioning components sometimes produce lateral misregistration. If the paper stop tongue is adjusted too high, the pull tab pulls the paper easily to curl, causing the paper to pass over. The other side of the specified plane is due to the non-parallel side of the paper is also the reason for the lateral overprint is not allowed. Treatment method: The height of the paper stop tongue is adjusted to 3 to 4 times the thickness of the printed paper, and the predetermined plane is adjusted to be parallel to the paper. In addition, pull gauge springs with different hardness should be selected according to the different thickness of the paper.
3 Irregular overprinting is not allowed at both ends
Unlawful overprint on both ends means that on the same printed sheet, the operation surface and the transmission surface are not overprinted at the same time, but the error at both ends is not the same as the standard line. There are mainly the following reasons for this situation.
1) Insufficient transfer time between paper handing tooth and impression cylinder
The long time between the delivery of the paper teeth and the transfer of impression teeth on the impression cylinder will tear the bite. If it is too short, overprinting will occur. The faster the machine speed, the more serious the situation will be. When the paper is handed over, due to insufficient transfer time, the impression cylinder hasn't completely closed the bite, and the delivery tooth has released the paper. In particular, some of the machine's paper feed teeth are closed by springs, rather than by the high point of the cam to close the teeth, it is more prone to such failures. Solution: As long as you don't tear the paper, adjust the opening time of the paper-feeding teeth and adjust the open-cam. In addition, the impression roller compression spring can tighten some.
2) The former defined plane is not parallel to the impression cylinder bus
In order to make the position of the picture and text conform to the requirements during the school edition, it can be achieved by moving the pull plate, but it cannot be moved too much, and the former rule should be restored after completing the work. If the two formerly defined planes are not on the same straight line and the difference is too large, then the front edge of the paper may be in contact with the front defined plane only at two points. The impact of the paper is concentrated on two points so that the force per unit area is too large, causing curling of the paper edge, resulting in irregular overprinting. In addition, the two sides of the paper should be at right angles. If the positioning is not a right angle, it is difficult to achieve a stable positioning requirement. Solution: Before the restoration, the specified plane is parallel to the impression roller busbar and re-aligned.
3) Insufficient time for paper feeding
When the paper-feeding tooth removes the positioned paper from the paper-feeding plate, it is in a stationary state and is transferred. Since the paper teeth are moved from motion to complete standstill, ensuring that the paper is picked up at the same position requires a certain amount of stabilization time. If this time is not enough or not enough, there will be an error in the position where the paper feeds the paper again, resulting in a misprint. Solution: Adjust the adjustment screw on the "positioning backing" so that the roller has a gap of 0.03mm on the smallest face of the cam. When correcting, both sides of the "backing" should be calibrated at the same time. The method is to put a 0.03mm feeler stopper. Between the roller and the cam, then tighten the screw while holding the roller against the cam and adjusting the "back-up" screw to the desired position. Repeatedly adjust until the correct position.
4 Bilateral symmetry and overprint are not allowed
The bilaterally unacceptable overprinting refers to the fact that the two sides of the operating surface and the transmission surface are not overprinted at the same time. Overprinting of the reticle is basically the same as that of the standard line in the direction of bite or dragging. The reasons for this phenomenon are various. If it is a second mobile phone, it may be caused by the wear of the hand roller surface or the damage of the bearing, and the wearing of the swinging tooth cam or the swinging hand wearing the horizontal axis slightly. If it is a new machine, it is generally not good to adjust the tension springs of the oscillating teeth row. Of course, it may not be the problem of positioning components. Solution: After the above problem occurs, first check the oscillating tooth row tension spring, tighten it or replace it with a new one. If this does not solve the problem, check the degree of wear of the swing handle pin and check the gap or ellipticity between the pin and bushing. If excessive wear is found, replace or repair it immediately. If it is a second mobile phone, the swinging tooth cam and the hand-held roller may also be worn. If this is the reason, it should be replaced in the case of an accessory. In the absence of an accessory, it is better to use the oilstone to dress the worn non-smooth part. Sleek. Incorrect timing of the front regulation will also result in overprinting at both ends at the same time. This requires loosening the fastening screw of the control cam and changing the relative position of the cam to achieve the correct time requirement.
5 Unilateral overprinting is not allowed
Sometimes overprinting occurs only on one side of the paper while the other side registers. There are two main situations: one end of the pull gauge is overprinted and the other end is not overprinted.
1) It is not allowed to register one end of the tab
Most of the general failures occur in the pull gauge itself. The analysis is as follows. When the normally conveyed paper has not reached the front gauge, the pull-up roller has fallen and pressed the paper, causing the pull-tab end of the paper to come out of position. Processing method: Adjust the side gauge cam so that the paper reaches the front gauge and after a certain settling time, the side gauge will drop the platen. The lifting time should be when the paper handing teeth grip the paper, ready to leave the front gauge. You can also adjust the speed of the paper to make it a little faster.
When the transfer paper bite into the paper and start to transfer forward, the side platen roller has not yet fully lifted, it also presses the edge of the paper, blocking the advancement of the paper, resulting in misalignment of the pull gauge end. Treatment method: There are two situations. One is that the pressure of the pull-tab is down, but the lifting time is too late, that is, the working time of the pull gauge is too long. This requires fine adjustment of the control cam. In the operation, it is necessary to jog the car, try not to counter the car, the cam can only move slightly, and the position must be determined according to the actual situation. The other is that the pull gauge roller is too slow to fall, and it is also slow to lift. This is because the working hours are wrong. Adjust the pull rules to make it fall faster.
The single front gauge is incorrect. The position of the front stop paper tongue should be a gap of 3 times the thickness of the paper. Too low or too high the height of the paper tongue can prevent the paper from entering the front gauge. Treatment method: Adjust the height of the front gauge according to the thickness of the paper.
2) No overprinting at one end of the gauge
This indicates that the paper is still unstable after entering the sidebar. Lateral positioning of the side gauges also requires that the positioned paper no longer be moved. Therefore, the paper on one end of the paper without a side-effect has a great effect on the paper brush roller or the paper feed roller. The reasons for the above situation are as follows: 1 The paper is sometimes not in place. It is necessary to check the speed of paper feeding and whether there are objects on the paper feeding board that prevent the paper from running; 2 The paper is ejected; 3 When the side guide pulls the paper, the other end is not Quasi-precisely, if the formerly defined plane is not parallel to the drum busbar, when the side gauge pulls the paper, the other end of the paper will be disengaged from the front gauge. Treatment method: Check the reason why the paper is not in place. Make corresponding treatment according to different situations. If the paper rebounds, increase the brush or slightly advance the platen roller on the conveyor belt. If it is specified before the plane is not parallel, according to the size of the paper at both ends of the paper bite, adjust the front rule before printing.
There are some other faults in the positioning components, such as paper feed skew, front tongue too low, insufficient delivery force, side-look up too slow, etc. The method is also varied, but all need us Understand the basics of offset press components, carefully find the root of the problem, and patiently adjust the repair or replacement parts.
Offset performance of the positioning part of offset press and its solution
May 07 07:07:23, 2024
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