Reasons and solutions for printing ghosting

Printing ghosting is one of the common printing failures. 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. Seriously affected the printing quality. There are many specific reasons for the ghosting, including printing machinery, printing process and paper. Generally, the types of ghosting are divided into three categories, namely, horizontal ghosting, vertical ghosting, and irregular ghosting. I will give a brief introduction to the causes and solutions of these three types of printing ghosting.

First, the horizontal ghost of the printing ghost

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. I think horizontal ghosting is generally caused by three reasons:

Ghosting caused by axial displacement of the two rollers during operation

Blanket drum thrust bearings to prevent axial movement of the cylinder member, if the thrust bearing wear or loose, there is a gap, the axial thrust action in the helical gear drum ghost occurs while transverse string action, 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. Solution: Pay attention to the maintenance of the printing machine, and find that the bearing with serious wear can be replaced in time to avoid it.

Ghosting caused by axial paper feed error

Such failures are generally caused by misalignment of the paper caused by the axial movement of the gripper shaft, resulting in ghosting. Solution: Adjust the gap between the two tight ends of the roller gripper shaft and the end face of the bushing.

Ghosting caused by ruffled paper

The paper with ruffled edge is squeezed by the first color printing pressure and gradually closes inward due to the printing pressure of the first color. After the first color is pressed and then enters the second color, it is originally squeezed by the first color. The paper that is pressed and closed is released again. This kind of closing and releasing is random, so that the previous residue remaining on the next unit blanket and the current imprint cannot overlap completely, resulting in ghosting. Most of this ghosting occurs at the two corners of the first color trailing edge, but there is no solution in the middle. The solution is to dry the paper to make the paper flatter before printing.

Second, the vertical ghost of the printing ghost

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. This World Seal believes that vertical ghosting is generally caused by three reasons:

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 frictional force of the embossed surface is large, and cannot be completely reset after each transfer, resulting in ghosting. Solution: Reasonably 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.

a ghost that is not stretched tightly

The blanket is not stretched tightly, the displacement during the rolling process is large, and it cannot be reset by the tension. The blanket is not tightly stretched. There are two situations: one is that the overall tension is not tight, causing a large area of ​​heavy shadow; 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. Solution: 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.

The plate is not taut or the plate is cracked, causing a ghosting of the plate during misalignment during operation.

Solution: Tighten the plate; if the plate is cracked, you need to change the plate.

Third, the irregular image of the printing ghost

Irregular ghosting refers to the ghosting of the double-dip offset press in the continuous operation (neither horizontal ghosting nor vertical ghosting). Irregular ghosting has the cause of the printing press itself, as well as the reasons for the printing process operation. The reason for the machine is mainly that the double-diameter roller has two sets of teeth that are not accurate enough. Printing process operation problems, mainly because the long-term use of the tooth pad is worn, the accuracy is reduced. Usually pay more attention to the maintenance of the machine, so that the machine is in good operating state, the ghosting situation will be controlled, the quality of the printed product will be improved.

Printing ghosting is often a demon that the printing masters can't drive away, but as long as you learn more about printing technology and constantly sum up experience, you will stay away from the devil and restore the true image!

Pet Snack

Pet Snack,Satisfy Desires Dog Can,Oem Dog Snacks,Delicious Pet Snack

DongGuan Lucky Pet Products Co., Ltd. , https://www.dgpetproducts.com