Causes and solutions for ghosting
We are a big printing company in Shenzhen China . We offer all book publications, hardcover book printing, papercover book printing, hardcover notebook, sprial book printing, saddle stiching book printing, booklet printing,packaging box, calendars, all kinds of PVC, product brochures, notes, Children's book, stickers, all kinds of special paper color printing products, game cardand so on.
For more information please visit
http://www.joyful-printing.com. ENG only
http://www.joyful-printing.net
http://www.joyful-printing.org
email: info@joyful-printing.net
Ghosting is a common printing failure. Although the vision can not directly observe the silhouette, it increases the area of the dot, the sharp angle of the edge becomes worse, affects the tone and color reproduction of the image, and reduces the sharpness of the image. Affected product quality. There are many specific reasons for ghosting, including mechanical, technical and paper. There are three types of ghosting, namely horizontal ghosting, vertical ghosting, and AB ghosting.
Lateral ghosting means that shallow shadows appear on the left and right sides of the dots or lines, and their positions are relatively fixed, and the ghosts are light and heavy.
1. A ghost caused by axial displacement of the two rollers during operation. The thrust bearing of the offset printing machine cylinder is a component for preventing the axial movement of the roller. If the thrust bearing is worn or loose, there is a gap. Under the action of the axial thrust of the helical gear, the roller is strung to generate a lateral ghosting, multicolor The axial fine adjustment mechanism of the machine is loose, and the bearing wears, which causes the printing plate to produce axial relative displacement of the plate cylinder and the blanket cylinder under normal working conditions, thereby causing lateral ghosting. Usually pay attention to the maintenance of the machine, and find that the bearing with serious wear can be replaced in time to avoid.
2. A ghost caused by axial paper feed error. Generally, the paper is inaccurate due to the axial sway of the gripper shaft, and a ghost image is generated. The solution is to adjust the gap between the two tight ends of the roller gripper shaft and the end face of the sleeve.
3. The ghost image caused by the ruffled paper, the paper with the ruffled edge is pressed by the first color printing pressure and gradually closes inward due to the paper edge pressure, and the first color is imprinted. When entering the second color, the paper that was originally squeezed by the first color is released again. This kind of closing and releasing is random, resulting in the previous residue and the current imprint of the blanket on the next unit. Can not completely overlap, resulting in a ghost.
Most of this ghosting occurs at the two corners of the first color trailing edge, and there is no middle. The solution is to dry the paper to make the paper flatter and then print.
Longitudinal ghosting means that shallow shadows appear in the axial direction of the dots or lines, and their positions are fixed. The ghosts are light and heavy, divided into partial and whole layouts.
1. The blanket cannot be completely reset after each transfer, resulting in ghosting. If the pressure between the rollers is too large or the radius of the roller is improperly arranged, the amount of displacement of the blanket under the action of the friction of the embossed surface is large, and cannot be completely reset after each transfer, resulting in ghosting. The solution is to properly adjust the lining data of the plate cylinder and the blanket cylinder so that they meet the requirements of synchronous rolling; under the premise of ensuring ink transfer, reduce the printing pressure.
2. The ghost is caused by the tightness of the blanket. The blanket is not stretched tightly, the displacement during the rolling process is large, and it cannot be reset by the tightening force. The blanket is not tightly stretched. There are two situations: one is that the overall tension is not tight, causing a large ghost image; Second, the blanket is not suitable for cutting the skew or the iron splint, which causes the local tension to be tight and causes partial ghosting. This kind of ghosting is mostly caused by the tipping part. Generally, the ghost image is only generated in the first few dozens. The solution is: if the overall tension of the blanket is not tight, re-tighten it; if the part is not stretched tightly, check if the blanket is cut or not properly installed, find out the cause and correct it.
3. The plate is not stretched or the plate is cracked, resulting in a ghost image caused by the misalignment of the plate during operation. The solution is to tighten the plate; if the plate is cracked, it needs to be changed.
AB ghosting refers to the ghosting of the double-dip offset press in continuous operation. The reason for this ghosting machine itself is also the reason for the process operation. The reason for the machine is mainly that the double-diameter roller has two sets of teeth that are not accurate enough. The problem of process operation is mainly that the long-term use of the dental pad is worn and the precision is lowered. Usually pay more attention to the maintenance of the machine, so that the machine is in good operating condition, the situation of ghosting will be controlled, and the quality of the printed product will be improved.