The positioning mechanism on the offset press is the main mechanism for controlling the positioning of the paper. It occupies a very important position in the entire machine and is known as the throat of the offset press. The structure, performance of the components, and the quality of the regulation are not only decisive for the quality of the product, but also have a close relationship with the production efficiency. Many offset press manufacturers are striving to shorten the preparation time and improve the efficiency of the tuning machine. Therefore, the rules of offset presses are constantly improving and developing. Although the models vary, their structure is much the same, and there are many common exceptions in the use of adjustments and guarantees of accuracy. The non-litigation is what kind of rules are used, and adjustment work is mainly carried out around its accuracy so that it can achieve the purpose of accurate overprinting. The following takes the positioning rules of the J2180 Offset Press as an example to discuss several aspects that are easily overlooked during adjustment.
First, the side of the rules of the pull paper time in the printing process, to ensure that the vertical and horizontal overprint of the printed sheet is accurate, side gauge paper roller pull paper time can not be ignored. Because the machine uses a roller continuous side gauge, the machine will complete a pull paper positioning job once a week.
Its completion of a printing drawing time is:
t=a/v
The time for lifting the side profile is: t'=(ZD-a)/v
In the formula: t-pulling time a- arc length when the paper-drawing cam contacts at the end D-pulling cam diameter V-rotating speed It can be seen from the above company that when a is large, t and t' are small. In other words, during the process of the machine running for a week, if the side profile pulls the paper for a long time, the lifting time will be short. If the time for lifting the side gage is fixed, the time for pulling down the paper will be early, which is bound to result in The positioning time of the paper at the front gauge is reduced. As the paper feeder cannot guarantee the absolute accuracy of the paper transport and the positioning time at the front gauge is short, the paper conveyance will advance or lag slightly, which will affect the stability of the front defined position and make the paper not yet stable at the front gauge. , Lateral regulations have dropped down paper, papermaking before the regulations are not accurate, but also affect the accuracy of the side regulations. If the drawing time is too long, after the paper is pulled into place, the pickup roller continues to pick up the paper, which also easily reduces the paper stress and curls the edge of the paper slightly. This causes overprinting failure (thinking is more obvious when the paper is thin); If the paper time is too short, paper that is farther away from the side gauge will not be pulled in place, which will also affect overprinting.
II. Lifting time of the side gauge paper rollers In the printing process, the side gauges and front gauges are always complementary and cooperate with each other to complete the overprinting process. If one party does not pull the rules, it will affect the other party. When the printing paper is conveyed to the front gauge through the paper conveying board, the paper is positioned by the front regulation plate, then the paper is pulled down by the side profile, and then the paper is sent to the impression cylinder for printing by the transfer paper. If the side pressure roller is lifted too early at this time, because the pull time is relatively constant, that is, the time of falling down the paper is also too early, it is easy to cause the paper to be positioned at the front gauge and is not yet stable. The wheel has already been pressed down and the paper is pressed. After the paper is pulled up, the paper is pulled up too early. As a result, the gripper has not completely closed the gummed paper. The side gauge is lifted. The paper is not controlled at this time and the paper runs out of control. , resulting in inaccurate overprinting. If the platen roller is lifted too late, after the gripper is closed, the paper may not be pulled into place or the gripper is already holding the paper. When the paper is ready to be sent to the platen roller, the side profile has not been lifted yet. This affects overprinting. When the platen roller is lifted and the gripper is closed, the paper passes through the front gauge and the side set position, enters the instant that the gripper teeth are closed, the side gauge platen roller is also lifted, and the paper will not be transferred due to the two parts. Out of control, the overlay error is small. However, this handover is not ideal. It can only ensure that the overprinting is accurate at low speeds. Once the high speed sleeve printing gripper and pick-up roller are connected, the time is very short. When the gripper closes, the pressure roller lifts up and the transfer time is very high. Short-term, coupled with the vibration of the machine at high speed, and the role of various forces, are likely to affect its transfer, this time the paper will appear intermittent out of control. Normally, when the adjustment is done, the side-look up time should be slightly later than the gripper time 0.5-1.5°. At this time, the paper will not be out of control due to the premature lift of the side gauges, nor will it be pulled up too late. Paper phenomenon.
Third, the side pressure platen roller pressure J2180 offset printing machine uses roller continuous side gauge, its working principle is equipped with 45 spiral cylindrical fan gear and end face cylindrical cam on the side gauge drive shaft, respectively, to control the uniform rotation of pick roller The regular up-and-down swinging of the paper roller and the regulation plate makes the paper-pulley roller cooperate with the paper-pushing roller to pull the paper to the regular position. Because the pickup roller is rotating at a constant speed, misalignment will not result in overprinting. However, the pickup roller rotates at a constant speed so that the paper-drawing speed is a constant speed, and the random-machine rotation speed is determined. In general, we only noticed that the side platen roller lift time and pull time, easy to ignore the side gauge roller pressure. Some people think that as long as the timing of the lateral regulation, the former regulation and the delivery tooth is correct, overprinting accuracy can be guaranteed, while the pressure of the side regulation pressure roller is lighter or heavier, which has no effect on the accuracy of overprinting. In fact, this is incomplete. The difficulty in adjusting the accuracy of the overprint is that some of the seemingly insignificant parts, which actually play a vital role, are most easily overlooked. For example, the pressure of the side gauge roller will directly affect the accuracy of the transverse overprint. After the paper is conveyed to the front paper stopper by the paper feed plate, the side paper rollers will drop the paper. If the pressure of the pressure roller is too heavy at this time, the paper pulling force may be greater than the bending strength of the paper after the paper is pulled into position, so that the paper is arched at the side shutter, causing the paper to pull over; if the pressure of the roller is over Light, that is, the pick-up force is slightly smaller than the quality of the printed paper. Although the paper is pulled to the backboard, due to insufficient power, the paper cannot fully abut against the side retainer, resulting in inaccurate pull and inaccuracy of the side register printing. Degree; When the pick-up force is equal to the average quality of the printed paper, due to the paper's own factors, and a variety of paper quality, humidity and other indicators are not exactly the same, at this time is also easy to cause horizontal overlay error. We believe that the pressure of the side gauge roller should be determined based on the size, thickness, temperature, and printing speed of the printed paper. It should be slightly larger than the average quality of the printed paper and less than the bending strength of the printed paper.
Fourth, the front gauge baffle plate and side gauge baffle plate position of the printing product is mainly determined by the position of the front and rear baffle plate in the machine to determine the position, only the front and rear side baffle plate baffle completely When the edge of the printed paper is flush, that is, when it is in line contact with the edge of the paper, it can be ensured that the rules of the paper will not cause the paper to be unstable at the positions of the rules due to the influence of the self-knowledge factors, resulting in the overlay accuracy error. It involves the verticality of the two adjacent edges of the paper and the positioning of the two baffles. In general, the front curve plate alignment line should be perpendicular to the side plate baffle alignment line. In this way, when the paper is transported to the front gauge and the side gauge, the two-phase bird edge and the regular positioning baffle are in line contact. In order to be accurate and stable, the accuracy of overprinting can be guaranteed. If the front gauge is not perpendicular to the side fence, the edge of the paper positioning will be skewed with the two guides, so that the edge of the paper will not be in full contact with the fence, so the contact area is small (point contact), positioning Instability, causing paper positioning instability. Special circumstances (such as the use of paper adjacent to the two sides of the mouth itself is not vertical), then should be based on the paper edge of the adjacent angle to adjust the rules of the two baffles, so that the edge of the baffle and paper edge parallel to ensure positioning stability.
The above analysis of the influence of the most easily overlooked aspects on the accuracy of overprinting when adjusting the positioning rules of offset presses is also a rough experience in our many years of work, and is willing to cause colleagues to pay enough attention to adjusting the positioning rules of offset presses. In order to better improve the tuning efficiency and print quality.
Excerpted from "Printing Equipment and Equipment"
First, the side of the rules of the pull paper time in the printing process, to ensure that the vertical and horizontal overprint of the printed sheet is accurate, side gauge paper roller pull paper time can not be ignored. Because the machine uses a roller continuous side gauge, the machine will complete a pull paper positioning job once a week.
Its completion of a printing drawing time is:
t=a/v
The time for lifting the side profile is: t'=(ZD-a)/v
In the formula: t-pulling time a- arc length when the paper-drawing cam contacts at the end D-pulling cam diameter V-rotating speed It can be seen from the above company that when a is large, t and t' are small. In other words, during the process of the machine running for a week, if the side profile pulls the paper for a long time, the lifting time will be short. If the time for lifting the side gage is fixed, the time for pulling down the paper will be early, which is bound to result in The positioning time of the paper at the front gauge is reduced. As the paper feeder cannot guarantee the absolute accuracy of the paper transport and the positioning time at the front gauge is short, the paper conveyance will advance or lag slightly, which will affect the stability of the front defined position and make the paper not yet stable at the front gauge. , Lateral regulations have dropped down paper, papermaking before the regulations are not accurate, but also affect the accuracy of the side regulations. If the drawing time is too long, after the paper is pulled into place, the pickup roller continues to pick up the paper, which also easily reduces the paper stress and curls the edge of the paper slightly. This causes overprinting failure (thinking is more obvious when the paper is thin); If the paper time is too short, paper that is farther away from the side gauge will not be pulled in place, which will also affect overprinting.
II. Lifting time of the side gauge paper rollers In the printing process, the side gauges and front gauges are always complementary and cooperate with each other to complete the overprinting process. If one party does not pull the rules, it will affect the other party. When the printing paper is conveyed to the front gauge through the paper conveying board, the paper is positioned by the front regulation plate, then the paper is pulled down by the side profile, and then the paper is sent to the impression cylinder for printing by the transfer paper. If the side pressure roller is lifted too early at this time, because the pull time is relatively constant, that is, the time of falling down the paper is also too early, it is easy to cause the paper to be positioned at the front gauge and is not yet stable. The wheel has already been pressed down and the paper is pressed. After the paper is pulled up, the paper is pulled up too early. As a result, the gripper has not completely closed the gummed paper. The side gauge is lifted. The paper is not controlled at this time and the paper runs out of control. , resulting in inaccurate overprinting. If the platen roller is lifted too late, after the gripper is closed, the paper may not be pulled into place or the gripper is already holding the paper. When the paper is ready to be sent to the platen roller, the side profile has not been lifted yet. This affects overprinting. When the platen roller is lifted and the gripper is closed, the paper passes through the front gauge and the side set position, enters the instant that the gripper teeth are closed, the side gauge platen roller is also lifted, and the paper will not be transferred due to the two parts. Out of control, the overlay error is small. However, this handover is not ideal. It can only ensure that the overprinting is accurate at low speeds. Once the high speed sleeve printing gripper and pick-up roller are connected, the time is very short. When the gripper closes, the pressure roller lifts up and the transfer time is very high. Short-term, coupled with the vibration of the machine at high speed, and the role of various forces, are likely to affect its transfer, this time the paper will appear intermittent out of control. Normally, when the adjustment is done, the side-look up time should be slightly later than the gripper time 0.5-1.5°. At this time, the paper will not be out of control due to the premature lift of the side gauges, nor will it be pulled up too late. Paper phenomenon.
Third, the side pressure platen roller pressure J2180 offset printing machine uses roller continuous side gauge, its working principle is equipped with 45 spiral cylindrical fan gear and end face cylindrical cam on the side gauge drive shaft, respectively, to control the uniform rotation of pick roller The regular up-and-down swinging of the paper roller and the regulation plate makes the paper-pulley roller cooperate with the paper-pushing roller to pull the paper to the regular position. Because the pickup roller is rotating at a constant speed, misalignment will not result in overprinting. However, the pickup roller rotates at a constant speed so that the paper-drawing speed is a constant speed, and the random-machine rotation speed is determined. In general, we only noticed that the side platen roller lift time and pull time, easy to ignore the side gauge roller pressure. Some people think that as long as the timing of the lateral regulation, the former regulation and the delivery tooth is correct, overprinting accuracy can be guaranteed, while the pressure of the side regulation pressure roller is lighter or heavier, which has no effect on the accuracy of overprinting. In fact, this is incomplete. The difficulty in adjusting the accuracy of the overprint is that some of the seemingly insignificant parts, which actually play a vital role, are most easily overlooked. For example, the pressure of the side gauge roller will directly affect the accuracy of the transverse overprint. After the paper is conveyed to the front paper stopper by the paper feed plate, the side paper rollers will drop the paper. If the pressure of the pressure roller is too heavy at this time, the paper pulling force may be greater than the bending strength of the paper after the paper is pulled into position, so that the paper is arched at the side shutter, causing the paper to pull over; if the pressure of the roller is over Light, that is, the pick-up force is slightly smaller than the quality of the printed paper. Although the paper is pulled to the backboard, due to insufficient power, the paper cannot fully abut against the side retainer, resulting in inaccurate pull and inaccuracy of the side register printing. Degree; When the pick-up force is equal to the average quality of the printed paper, due to the paper's own factors, and a variety of paper quality, humidity and other indicators are not exactly the same, at this time is also easy to cause horizontal overlay error. We believe that the pressure of the side gauge roller should be determined based on the size, thickness, temperature, and printing speed of the printed paper. It should be slightly larger than the average quality of the printed paper and less than the bending strength of the printed paper.
Fourth, the front gauge baffle plate and side gauge baffle plate position of the printing product is mainly determined by the position of the front and rear baffle plate in the machine to determine the position, only the front and rear side baffle plate baffle completely When the edge of the printed paper is flush, that is, when it is in line contact with the edge of the paper, it can be ensured that the rules of the paper will not cause the paper to be unstable at the positions of the rules due to the influence of the self-knowledge factors, resulting in the overlay accuracy error. It involves the verticality of the two adjacent edges of the paper and the positioning of the two baffles. In general, the front curve plate alignment line should be perpendicular to the side plate baffle alignment line. In this way, when the paper is transported to the front gauge and the side gauge, the two-phase bird edge and the regular positioning baffle are in line contact. In order to be accurate and stable, the accuracy of overprinting can be guaranteed. If the front gauge is not perpendicular to the side fence, the edge of the paper positioning will be skewed with the two guides, so that the edge of the paper will not be in full contact with the fence, so the contact area is small (point contact), positioning Instability, causing paper positioning instability. Special circumstances (such as the use of paper adjacent to the two sides of the mouth itself is not vertical), then should be based on the paper edge of the adjacent angle to adjust the rules of the two baffles, so that the edge of the baffle and paper edge parallel to ensure positioning stability.
The above analysis of the influence of the most easily overlooked aspects on the accuracy of overprinting when adjusting the positioning rules of offset presses is also a rough experience in our many years of work, and is willing to cause colleagues to pay enough attention to adjusting the positioning rules of offset presses. In order to better improve the tuning efficiency and print quality.
Excerpted from "Printing Equipment and Equipment"
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