In the process of printing newsprint with a high-speed web machine, due to the strong hygroscopicity of newsprint paper and the relatively low mechanical strength, paper breakages often occur. Some are unavoidable, while others can be avoided or they can be reduced. Based on many years of work experience, the author summarizes and analyzes the breakdown of newsprint paper breaks in high-speed web presses, points out the corresponding causes and countermeasures, and provides some references for peers and colleagues.

In the printing of high-speed rotation newsprint, newsprint breaks can generally be divided into interruptions in the printing path and web breaks, among which breaks account for the vast majority.

Print stop paper

Cause Analysis

1. Bad adhesion at the paper roll connector

In the manufacturing process, webs often have joints in the middle of a roll of paper. According to the requirements for web joints, the joints must be connected positively and securely. The width of the joints should not exceed 20 m and must not be adhered to another layer. However, according to the situation in the printing process to interrupt the paper, the breakage of the joints has also occurred from time to time.

2. Deep impact on both sides of the roll

This can cause the paper to be impacted to break and the front and back pages to be twisted together. When the paper roll is printed here, either the edge of the paper is broken or broken, or the front and back pages are twisted together, causing the crack to gradually increase and break.

3. Large holes and tears in the middle of the paper roll

This can cause the paper to not pass through the web break detection device, causing a web break.

4. Large wrinkles in the middle of the roll

These wrinkles are suddenly straightened during the printing process, causing sudden changes in the tension before and after the wrinkles. If the wrinkle is exceeded, the web breaks.

5. During the printing process, water and ink are large

This can cause the paper to absorb too much water, reduce the mechanical strength, and can not withstand the normal printing pressure and tension, resulting in breaks.

Suggest plans

There are some paper breaks in the printing process that we cannot solve. For example, paper jams, paper breaks, broken papers, large wrinkles, etc. may cause breaks in the paper. We can only choose products with better quality on paper procurement.

1. For paper rolls with connectors

Color chalk can be marked in advance at the paper roll joint. When the paper roll is printed on the label, the printing speed is properly reduced, and the success rate of the paper is higher at a lower speed.

2. For a paper roll with a bruise

In general, the sponge is used to moisten the wounded area and marked with colored chalk. Like a joint roll, when the roll is printed on the label, the printing speed is appropriately reduced, and the success rate of low-speed paper is guaranteed. Even if the paper breaks, low-speed printing will cause less damage to the machine than high-speed printing.

If the paper is staggered at the impact area, the twisted and staggered area is generally cut with a knife to prevent tearing of the paper when the roll is released to the position, resulting in a paper break.

3. For the printing process, water, ink

During the printing process, it should be carefully sampled to control the balance of ink and water, prevent the paper from being too wet or piled with ink and cause paper breakage.

Broken paper

Cause Analysis

In the process of printing newsprint on high-speed web machines, paper breaks are mainly caused by mechanical problems, paper problems, and human factors.

1. Paper break caused by mechanical problems

(1) SS light is off, see Figure 1. The GS side of the drive belt is used to detect the black strip on the pre-tensioned roll to determine the position of the roll. The electric eye is prone to malfunction. The electric eye lamp may be broken or may be blocked. As a result, the SS lamp will not be lit. As a result, although the paper take-up diameter is also satisfactory after the paper roll is synchronised, the paper cannot be determined due to the inability to determine the paper receiving position. Broken paper.

(2) The knife does not move or the movement is not in place. When the brush is pressed under the position of the receiving paper, the cutter succeeds, but the cutter does not move, causing the original printed tape to be not cut after the paper is fed. When the paper roll runs, both the old and new papers are cut off simultaneously. Broken paper; after the paper was cut, the knife did not reach the position and only one side of the old paper roll was cut. The paper tape was torn during the operation, resulting in a paper break.

(3) The drive belt pops up after receiving the paper. After the brush breaks the paper and presses the knife, the new paper roll should be controlled by the drive belt for a period of time during the time it takes the paper position to the normal print position. However, sometimes the drive belt springs up after the cutter breaks the paper, causing new The paper roll loses tension during the web position to the normal printing position, resulting in a web break.

(4) Drive belt power is not enough. When the drive belt drives the pre-acceleration of the paper roll, the speed and the printing speed of the pre-acceleration paper roll cannot be synchronized due to power problems or belt slip. When the sensor detects that the diameter of the printing paper roll has been reduced to a preset value, the speed of the pre-accelerated paper roll does not reach the printing speed. As a result, the paper roll being printed runs through the paper, resulting in a web break.

2. Paper break caused by paper problem

(1) The paper roll is not round. If the outer circle of the paper roll is not round or the paper core is not round, the paper roll or the paper core will make a sharp jump during the printing process, resulting in the break of the paper when the paper is fed.

(2) The paper roll is large. When the radius of the paper roll is very large, but it can just fit on the paper frame, when the paper is completed, the paper roll may encounter a fixed piece of the fixed drive belt during the movement, resulting in a paper break.

3. Paper break caused by human causes

(1) Flying paper. Newspaper rotary presses use high-speed automatic take-up. In order to ensure the successful completion of the receipt of paper, the team members must prepare for the printed web (see Figure 2). If during the preparation process, the triangle is not pulled tightly, the triangles are loose on one side or the triangles are under the two blue strips and the knife is cut too far in the middle. When the drive belt pre-drives the paper roll, the paper catches the triangle. It caused a paper break.

(2) The black strip is not in place. When the position of the black strip is deviated from the GS side electro-optic detection position of the drive belt, or when the black strip is left behind, the black strip cannot be scanned by the GS side of the drive belt, causing the SS indicator to fail to shine. As a result, the paper roll is synchronized. The splicing diameter also meets the requirements, but it cannot be determined that the splicing position results in running paper and paper breaks occur.

(3) The triangle did not cut. As shown in Figure 2, when preparing for the team members, two blue pieces of paper should be cut with a knife at the triangular tip of the two blue plastic strips, leaving only the strip of paper glued by the white strip to connect the entire triangle. If the team member forgets to cut two pieces of paper during preparation, the two pieces of paper stick together but tear the triangular connection on the pre-acceleration paper roll, resulting in a web break.

(4) No tear tape. Before picking up the paper, the protective layer of the blue tape on the triangle should be torn off, so that the blue tape can be attached to the running tape when the paper is brought up to complete the high-speed take-up. If the protective layer of blue tape on the triangle is not torn off, the two tapes will not stick together during the process of paper-making. The pre-accelerated paper roll will not be released, but the cutter will cut off the paper roll that is printing and cause the paper to break. paper.

(5) The edges of the paper are damaged. The edges of the paper roll were damaged, and the team members did not find out when doing the preparatory work. The broken paper on the edge of the paper cannot withstand the normal tension, resulting in a paper break.

(6) The paper tray is not in place. The paper tray is not adjusted properly, and is not within the receiving position. When the paper roll is moved to the receiving position, the paper tray does not move, causing the paper roll that is being printed to run out and the paper breaks.

Suggest plans

1. Paper break caused by mechanical problems

If a paper break caused by a mechanical problem occurs, we should immediately check if we can solve it. Take the SS lamp off fault as an example. After discovering, stop first, check whether there are black plastic strips, black strips are not in place, and the driving belt GS side electric eyes are not blocked, etc. If the above is not a problem , we must immediately notify the mechanics team to follow up and solve them. The vast majority of mechanical failures cannot be solved by oneself. In the high-speed printing process, after the fault appeared, the operator sometimes did not reflect it and the machine stopped. Therefore, always concentrate on energy. Occasionally, there are some problems we can temporarily handle manually to ensure smooth printing. If the drive belt breaks immediately after the paper is picked up, we will use a piece of rag to push the paper roll in the opposite direction to prevent the paper roll from overrunning until the tension belt tensions the paper.

2. Paper break caused by paper problem

In the paper break caused by a paper problem, the machine speed is generally reduced when the paper is fed and the low speed paper is received because the outer circle of the paper roll is not round or the paper core is not round, causing the paper roll or the paper core to sever. The rate is higher. When the roll or paper core is severely out of round, the web break is often difficult to solve. When the radius of the paper roll is extremely large, only the diameter of the paper is picked up, but this is also a waste of paper.

3. Paper break caused by human causes

The paper break caused by human factors is the best solution, as long as the team members are full of energy and feel good during work hours. They are careful during the preparation work. The team members supervise and remind each other and this kind of failure can be completely avoided. .

Department of Printing and Packaging, Wuhan University Xu Hongping Shenzhen Special Zone Newspaper Printing Factory Mao Jianguo

Source: China Printing Materials Business