Solution for pulling in printing
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In printing, the embossed printed sheet is adhered to the surface of the blanket by the ink on the blanket cylinder, and on the other hand, the edge of the paper is bitten by the impression cylinder, with the impression cylinder Rotate to force the paper to separate from the blanket cylinder. The force that the paper adhered to the surface of the blanket cylinder is perpendicular to the surface of the paper, and the force that pulls the paper off the surface of the blanket is called the peeling tension. If the peeling tension makes the surface strength of the substrate unbearable, the fiber and filler on the surface of the paper. Or the paint will be pulled down by the ink on the blanket, and accumulated on the surface of the blanket and the printing plate, so that the ink cannot be uniformly and uniformly adsorbed onto the paper, causing damage to the dots and loss of small dots; when printing the image, the image is leveled. Lost, the imprint is illusory. The accumulation of paper scraps on the printing plate and the blanket will also damage the blanket when it is severe, and the paper scraps stuck on the printing plate will be transferred to the water bucket, which reduces the effect of the wetting fluid.
When the phenomenon of pulling hair occurs, the number of times of cleaning the blanket must be increased, which increases the labor intensity of the printing worker and affects the production efficiency. At the same time, due to excessive shutdown, the ink supply amount is uneven, and the printed ink color is printed. Before and after, it is very easy to be inconsistent. In serious cases, there will be waste products, resulting in unnecessary waste.
There are many factors that cause the paper to be pulled. There are two main factors, one is the surface strength of the paper, and the other is the peeling tension during printing. The size of the peeling tension depends on the viscosity of the ink, the printing speed, and the like.
Different papers, raw materials and papermaking processes are also different, the surface strength varies greatly, and the paper with poor surface strength is prone to hair pulling. When multi-color offset printing, the post-printing color is wetted by the dampening liquid in the blank part. After printing on the paper, after the paper is wetted, the surface strength is reduced and the pulling phenomenon is aggravated.
The solution to the brushing is:
First, according to the characteristics of printing equipment and printed products, paper with appropriate surface strength is selected during printing.
The second is to reduce the viscosity and viscosity of the ink by adding varnish or de-adhesive to the ink, which is the most common method for printing paper with poor surface strength. The pulling phenomenon will increase with the viscosity of the ink, and the viscosity of the ink is most affected by the temperature. Therefore, the printing workshop should be kept at the same temperature as possible, so that the printing workshop has an ideal production environment, and the ink is added to the ink. When it comes to ink or de-adhesive, it should be suitable. Otherwise, it will cause a series of problems such as increased emulsion emulsification, increased dot gain and extended drying time.
Third, when printing paper with poor surface strength, the printing speed should be controlled. The higher the printing speed, the greater the peeling tension when the paper and the blanket are peeled off, the easier it is to pull the hair, the bonding strength of the fiber and the filler on the surface of the paper is large and small, uneven, and the bonding strength of some particles and fibers is small, so When the printing speed is not very large, the pulling phenomenon will occur, but it is not serious. The bonding strength of most particles or fibers is equivalent. Only when the printing speed is higher than a certain critical point, the peeling tension reaches a certain level, and a relatively serious pulling phenomenon occurs. Moreover, as the speed increases, the pulling phenomenon will continue to increase, so when printing paper with poor surface strength, the printing speed should be controlled to print at a slower speed.
The fourth is to replace the blanket, or use talc powder mixed with sulfur powder to wipe the blanket, reduce the viscosity of the blanket. The phenomenon of pulling during printing is sometimes caused by the sticky of the blanket, so after each printing task is completed, the plate should be unloaded in time and the blanket cleaned. In addition, when conditions and time permit, when printing paper with poor surface strength, it can be printed with a monochrome machine, which can reduce the pulling phenomenon and will not affect normal production.