Is There Ink Bars And Ghosting In Flexographic Printing? The Method Is Here!

Flexographic printing is a direct printing method in which the printing plate has elastic and raised images. The printing plate is fixed to the plate roller using double-sided tape, and the printing plate is supplied with ink by a carved metal or ceramic mesh roller. There are various types of printing equipment that can be used for flexographic printing production, such as the most common unit type flexographic printing machine, which has many design routes, such as upper paper feeding and lower paper feeding; There are also many types of ink that can be used for flexographic printing production, such as water-based ink, UV ink, etc; There are countless products that can be produced through flexographic printing. In such a complex and ever-changing environment, it is inevitable to encounter various problems in the production process of flexographic printing. Today, let's talk about the common ink bar and ghosting problems and their solutions in flexographic printing production.
01
Printing ink bar
Printing ink bars, commonly seen are stripes perpendicular to the printing direction and equidistant from the gear pitch size. The main causes of ink bars are gear and mechanical vibration, such as whether the mechanical accuracy is high or low, whether the gear design is reasonable, and whether the gear assembly is appropriate, all of which can lead to the generation of ink bars. During the printing process, if there is an ink bar issue, the following methods can be attempted:
corrected gear
If the gears move back and forth during the transmission process, it will cause ink bars in the printed material and wear out the printing plate. Since the helix angle is determined by the main transmission gear, this parameter of the plate roller gear must be the same as it. However, the methods used by various manufacturers to eliminate the influence of axial force are different. The general approach is to chamfer the top angle of the gear by 45 ° and remove the sharp edge. However, the method used by a well-known manufacturer is to polish diagonally from the tooth root to the tooth top on both sides of the gear, with a polishing height ranging from one-third to one-half of the tooth height; Empty the gap of axial force to avoid gear vibration caused by axial force generated during gear operation.
Offset the printing plates for layout
The purpose of staggered typesetting is to reduce the jumping of the plate roller caused by plate typesetting. Practice has proven that relying solely on the pressure strips on both sides is difficult to support the bouncing of the plate rollers caused by unreasonable layout. We found that in severe cases, the jumping of the plate roller can cause vibration of the mesh roller, which in turn can lead to abnormal wear of the scraper, especially when printing long sheets at high speeds.
Use softer double-sided tape as a cushion for cushioning
 

Using softer double-sided tape as a cushion is a very practical solution, but when using this method, it is necessary to consider the pinhole problem caused by using medium density double-sided tape or low-density double-sided tape during on-site printing.
02
Printing ghosting
The characteristic of printing ghosting is the occurrence of local ink color fading at fixed positions when printing units of each repeated circumference. Ghosts are not caused by color matching, and ghosting can also occur during monochrome printing. Ghosts often occur in the live version, and since it is difficult to explain the reasons for their formation, their foreign counterparts call it Ghosting, while their domestic counterparts call it Ghosting. In short, the cause of ghosting is actually the marks left by the printing plate on the mesh roller.
The commonly used methods to solve the ghosting problem are as follows:
The repeated circumference of the printing plate is greater than or equal to the circumference of the mesh roller. It is obvious that when the diameter of the mesh roller is small, that is, when the mesh roller rotates faster and the frequency of ink replenishment is higher, ghosting will not occur. Therefore, targeted selection of product circumference based on the mesh roller circumference of the flexographic printer must be taken into account when finalizing the design.
The color blocks on the pattern of the laminated product should be placed in the gaps of the repeated pattern according to the difference between the circumference of the mesh roller and the circumference of the plate roller, and should not overlap with the original color blocks. Due to the fact that most of our products use imposition printing, only a few can truly achieve a repeat circumference of unit product equal to or greater than the circumference of the mesh roller. Therefore, in the case where the repeated circumference of a large number of products is less than the circumference of the mesh roller, we must check whether there is a large color block pattern at this position according to the difference between the circumference of the mesh roller and the circumference of the plate roller. If this happens to be a gap, the product will not have ghosting. If there is a large color block pattern here, the probability of ghosting is very high.
Use a slow drying agent. When encountering unavoidable design issues, using a slow drying agent would be a practical solution. The main purpose of adding a slow drying agent is to improve the leveling of the ink on the web roller, so that the ink dries as slowly as possible on the web roller. When using UV ink equipment for printing, the probability of ghosting is relatively low. This is because if the UV curing device is not turned on, the drying of UV ink will be slow. However, both water-based ink and alcohol solvent ink can add slow drying agents, which are helpful for dealing with ghosting.
Ghosts often appear during the on-site printing process, which is related to the fact that many operators like to increase pressure during on-site printing. Therefore, another way to solve ghosting is to reduce ink pressure. Sometimes ghosting is detected when the printing speed is slow, and by increasing the printing speed, the ghosting will gradually disappear, which is actually due to the reduction of pressure.