Analysis of the reasons for the most popular flann

Flannelette: offsctdruckereien anti pilferage and analysis of the causes of printing plate pilferage

printing plate pilferage is divided into full plate large area pilferage and local pilferage, and the reasons are various. Improper adjustment of the pressure between the water glue roller and the printing plate, improper ink adhesion of the water glue roller, improper proportion of wetting liquid, improper spreading of the printing plate liner paper, quality problems of the printing plate itself, etc., are easy to make both sides of the printing plate dirty. During the printing process, sometimes there is a problem that both sides of the offset plate are dirty. The following is an analysis of the causes of dirt on both sides of the printing plate

uneven water roll

when adjusting the contact pressure of the water supply roll to the water channeling roll, we must pay attention to the symmetry of the direction of the eccentric bearing, otherwise it will lead to the non parallelism of the water roll with the plate cylinder and the water channeling roll, and the flannelette of the water channeling roll is easy to be pushed into a spiral shape by the axial force, so the water delivery cannot be uniform. If the eccentric adjustment at both ends of the water roller is asymmetric, the pressure of the water roller will be uneven, and the side of the printing plate will be easy to get dirty. Therefore, when testing the pressure of the water roller, you can measure several places, not only at both ends, but also in the middle

in addition to accurately adjusting the contact pressure of the water roller, the daily reasonable maintenance of the water roller is also very important

1. During the ordinary offset printing operation, the water roller should be kept clean and free of oil stains

2. The water roller fleece should be kept moist and have a certain amount of moisture

3. Clean the water roller regularly. If the water rubber roller can be cleaned, wash it. If there is too much oil stain and it cannot be cleaned, replace it with a new water wool jacket in time to prevent the printing plate from getting dirty. Another method can effectively prevent ink sticking on the water roller, that is, when printing, a small amount of hydrophilic colloidal substance Arabic gum is added to the water bucket solution, and publicity activities throughout the country can effectively increase the hydrophilicity of the water roller. Use hydrophilic materials such as sponges to wipe away the emulsified oil stains in the water bucket solution and adsorb the dirty ink on the surface of the water roller

the two ends of the water roller are thin and the middle is thick

when the water roller is processed and grinded on the lathe, because it is an elastomer, the two ends are under large force, there is vibration in the middle and the pressure is small, most of them have different degrees of shape errors of the two ends are thin and the middle is thick, and there is a gap at both ends, which is easy to get dirty. In addition, during sewing, the two ends of the water roller cover are stretched thin and thin, and the water at both ends is less absorbed, which can not fully wet the surface of the printing plate, and it is easy to cause dirt on both sides

Troubleshooting: the size of the cutting water glue fleece should be consistent with that of the water roller, and should not be too short. The tension of the sewing sleeve shall be uniform, not too tight, and there must be room for closing, so as to prevent the two ends of the water roll sleeve from being too thin and maintain the lubrication of the screw rod up and down

the size of the printing plate lining is too small

in general, the lower side of the printing plate should be padded with paper. In order to avoid wetting the two sides of the printing plate padding, the horizontal size of the backing paper will be smaller than the printing plate size. However, the size of the backing paper is too small, which will cause insufficient pressure on both sides of the printing plate, resulting in poor contact between the printing plate and the water roller and dirty

Troubleshooting: when cutting the backing paper of the printing plate, the horizontal size should be controlled within the range of 10 ~ 20mm smaller than the printing plate. In order to prevent the backing paper from being damaged by water, a layer of fantulin or yellow 1st layer powder can be coated on both sides of the backing paper, and oil and engine oil can be paved. The principle of oil and water repelling each other can be used to avoid wetting the backing paper and improve the use effect. If the liner paper of the drum is wet, it is easy to rust the shell of the drum

ink sticking at both ends of the water roller reduces the water transmission performance

printing 5 gold tool torque detection equipment parameters: if the water at both ends of the plate is controlled too little, it will cause insufficient water supply to stick ink at both ends of the water roller, causing dirt on both sides of the plate