Cause analysis of the deformation of the most popu

Analysis on the causes of deformation of iron printing dots

the so-called dot deformation refers to the increase or decrease of dots. In serious cases, circular dots will become square dots or irregular dots. Point deformation will distort the image and text at a light level, or distort the image and text at a heavy level, causing the product to be scrapped as the standard to judge the accuracy of the spring testing machine. The improper application of printing may constitute the error of the experiment. There are several reasons for the deformation of iron dots

1. deformation of starting point of sliding friction

compression deformation of elastomer and the resulting sliding friction will cause point deformation when reflected on iron printing products. When the pressure is appropriate, the friction is small, and the quality of point replication is high: when the relative sliding friction is too large, the point will increase or decrease directionally. The disadvantage mainly occurs in iron printing equipment with poor precision of parts. When using this kind of equipment, soft liner materials can be appropriately selected in order to make up for the lack of accuracy of the equipment. But at the same time, it causes the compression deformation of elastomers such as the lining of the printing plate cylinder and blanket, as well as the corresponding sliding friction phenomenon. Solution: improve the accuracy of the equipment

2. The change of ink volume leads to the deformation of the starting point

the ink volume transmitted by the ink conveying system is too much, which makes the surface of the printing plate cross the ink layer, and the ink diffusion in the rolling causes the increase and deformation of the dot print. Solution: first of all, we should have a detailed understanding of the distribution of pictures and texts in the printing sheet, and know the amount of ink in each part. During operation, the ink volume shall be appropriately enlarged for the area with large field or dot area, and the minimum ink volume or no ink volume shall be given for the area with small dot area or no graphics and text. This work must be controlled from the ink supply part, that is, adjust the gap between the ink bucket roller and the ink knife, appropriately enlarge the gap in the area with large ink volume, and appropriately narrow the gap in the area with small ink volume, so as to avoid excessive ink volume in the ink transfer system

3. improper pressure leads to the deformation of the starting point

the printing iron is the same as other lithographic offset printing. It is carried out under appropriate pressure conditions, that is, the minimum pressure is used to make the impression of the printed matter neither "empty" nor "spread". The pressure of iron printing must be adjusted according to the characteristics of different products. Process requirements, quality and other objective factors to determine the adjustment range. The printing iron pressure is usually controlled at 0.1 5mm. The following factors should be considered in pressure regulation

(1) contact pressure between water roller, ink roller and printing plate

(2) friction between printing plate

(3) density value of graphics and text, degree of deformation of points

(4) meshing and operation of drum gear

(5) transfer of imprinted ink

(6) service life of rubber blanket

(7) friction between sheet and drum

(8) displacement of liner is a key to make pressure adjustment well.The condition is that the linear speed of the three rollers is consistent. It is generally believed that the same linear speed can be achieved by the same radius of the three rollers, but the problem is that the quality of the three rollers is inconsistent, and the compression deformation causes the rubber blanket and liner to extend to a certain extent, the printing plate and liner also extend to a certain extent, while the embossing roller does not extend. In order to avoid the phenomenon that the linear speed of the rubber drum, the linear speed of the printing plate drum and the linear speed of the embossing drum are not satisfied, the ideal value of the radius of the embossing drum, the radius of the printing plate drum and the radius of the rubber drum are designed through careful calculation to guide the manufacturing of iron printing equipment. The compression amplitude between the iron printing rollers is large, the speed difference in the contact area is large, and excessive sliding friction will lengthen and deform the points, so the pressure adjustment of the three rollers is the key to the quality of the print

during pressure commissioning, pay attention to the pressure between the ink roller and the plate cylinder. Excessive pressure between the inking roller and the plate cylinder will increase the compression deformation of the elastic roller, and the sliding friction in the contact arc is large, resulting in unclear points, virtual or increased. In general, use a 0.2mm feeler gauge to detect the pressure between the ink roller and the plate cylinder, and it is better to feel the tightness of the handle. If the pressure is too high, the compression deformation of the inking roller itself is bound to increase, and the friction in the contact arc between the two is large. The hardness of inking roller is better from HS30 to HS40. The lower the hardness is, the more severe the elastic deformation is. Therefore, it is very critical to maintain the appropriate hardness of rubber roller

4. The starting point of the rubber blanket problem is deformation

the rubber blanket for iron printing must be elastic and have strong tensile strength, so that your work can return to normal. Small elongation and appropriate hardness, good flatness, lipophilicity, wear resistance, acid and solvent resistance, etc. The rubber blanket is generally composed of oil-resistant adhesive layer on the surface, cotton frame layer and elastic adhesive layer to ensure that the rubber blanket has sufficient radial tension resistance and minimum elongation. If the radial tension resistance is insufficient, it is easy to tear or cause large deformation when the rubber blanket is tightened and rolled, and it cannot be reset at the moment of rolling

the maintenance of rubber blanket is very important. When scrubbing the new rubber blanket, first use kerosene, sprinkle some talc powder, and wipe it repeatedly with a soft and clean wiping cloth, with average force vertically and horizontally, so as to show the natural color of the rubber and the inherent micropores. Then thoroughly wash the talc powder with gasoline before it can be put into use. Clean it with gasoline after printing. After disassembling the blanket, it usually needs to be tightened twice: the first is the tension of the blanket; Tighten it. Run it at a constant speed for 10 minutes after startup, and then tighten it for the second time. The purpose is to prevent the rubber blanket from loosening due to no tension during iron printing production. However, the tightness of the blanket varies with the size of each person's arm strength, as well as the tightness. It's no good that the rubber cloth is too loose, but too tight will also bring printing disadvantages, resulting in the rubber cloth surface due to large tension, friction concentrated on the surface, and the due elasticity will be weakened. Even if the printing iron pressure is normal, there will be a surface velocity difference, and the cabinet should be slightly deformed

reprinted from: keyin

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