How to achieve automatic registration of the colorless printing or on-line bump of the reel?

In the packaging printing industry, especially in the cigarette package printing industry, web gravure printing machines are known for their high production efficiency, printing ink color and stable quality, so they are regarded as the first choice for high-volume printing. However, in actual production, due to the particularity of cigarette package printing, it is not only necessary to print varnish or colorless anti-counterfeiting ink, but also to achieve on-line bump, as shown in Figure 1.

Figure 1 Structure of the web gravure printing machine

The printing registration of the web gravure printing machine is realized by the overprinting cursor, while the varnish or colorless anti-counterfeiting ink is colorless, and the on-line concave color group also has no printing color, which leads to the overprinting cursor printed on the printed matter. It is also colorless and cannot be accurately identified, so that it is impossible to accurately achieve double-eye overprinting. Although the light color and colorless color groups can be overprinted with a single electric eye, the printing registration problem still exists due to certain defects in the single electric eye overprinting.

In order to solve the above problems, the author implemented the corresponding transformation, and finally realized the automatic and accurate registration of the colorless printing or the on-line concave and convex of the web gravure printing machine. Below, the author will introduce this transformation process, hoping to help everyone.

01 single electric eye overprint defect

The light color and colorless color group adopts single electric eye overprinting, mainly because the overprinting cursor printed by the natural color group is too light or colorless and cannot be recognized by the electric eye, so the signal generated by the single color electric eye scanning reference color cursor can only be used, and the same device encoder The generated signals are compared to register, thereby enabling the overprinting of the circumferential direction of the light color and the colorless version of the single electric eye.

However, there are two problems in single-eye overprinting: one is that it can only perform circumferential automatic overprinting, and the horizontal overprinting relies entirely on manual, resulting in unstable overprinting, coupled with fast production speed, and horizontal running is completely dependent on manual to achieve overprinting. There are more wastes; secondly, the overprinting of the single electric eye in the circumferential direction is actually unstable, mainly because one signal per week, the signal will be inconsistent due to paper shrinkage, which will not only lead to unstable printing of the natural color group, but also lead to color Group overprinting produces fluctuations. Therefore, it is necessary to realize double-electron automatic overprinting for light and colorless groups.

02 transformation process

Since the overprinting cursor of the D and E color group printing in Figure 1 is colorless, can you install a cursor disk on one end of the printing plate and make a cursor for overprinting on the cursor disk, so as to realize automatic overprinting of the double electric eye? It is for sure. Because this simply shifts the position of the overprint cursor, that is, from the surface of the paper to the surface of the cursor disk, the principle does not change. In order to facilitate the recognition of the electric eye, we design the cursor on the cursor disk as black, and the electric eye grabs one of the cursors and the overprinting cursor for comparison, and achieves accurate overprinting with the automatic overprinting system of the web gravure printing machine. The structure diagram and physical map of the cursor disc are shown in Figures 2 and 3, respectively.

Figure 2 Cursor disk structure

Figure 3 cursor disk physical map