Interpretation of printing and coating process（5）

Printing and coating equipment is divided into coating machine and printing and coating linkage. The glazing machine is generally a stand-alone operation, the processing speed is slow, the quality stability is slightly worse, and the calendering treatment is often required. At present, large-scale offset printing manufacturers at home and abroad mostly use online printing to improve the speed and quality of coating. It can be said that online printing is the development trend of coating machinery.

The printing and glazing linkage is used for glazing and coating by a printing unit, and its basic form is to glazing and coating by the last printing unit of a sheet-fed offset press. There are generally two forms of glazing and coating using a printing unit: one is glazing and coating with a dampening device, and the other is glazing and coating with an inking device.

It is the simplest and most economical option to use the existing printing unit on the sheet-fed lithographic printing machine for coating. The production area is small and the additional equipment investment can be saved. However, the glazing coating effect is not very good, and it is only suitable for coating simple and less demanding products.

The independent coating unit on the printing machine is used for online coating, which has high production efficiency and stable coating quality. It can use resin plates or traditional blankets for glazing. Like the printing device, all are monitored and controlled by the printing press control center, such as the lateral and circumferential register adjustments and diagonals of the photosensitive resin plate. Register adjustment, etc.

The on-line glazing device can apply thick and uniform glazing to the entire surface or partial graphics of the substrate. The glazing can use either a blanket or a flexographic plate for fine local glazing. It can be water-based glazing or UV glazing.

When choosing an online coating system, the advantages of anilox roller coating are obvious, but the investment is relatively large. Anilox roller glazing can accurately control the thickness of the glazing coating, does not depend on the printing speed, and is rarely affected by the fluctuation of the glazing oil viscosity. The most representative is the use of a closed ink knife system glazing device, which consists of a ceramic anilox roller, a closed doctor blade and a flexible resin coated plate roller. This in-line coating has fast speed and high efficiency. The anilox rollers can be quickly replaced. Different anilox rollers can be selected to complete the coating accurately as required. It can not only obtain a full coating layer, but also perform precise partial coating.

Coating has become an important means of post-press processing. With the continuous maturity of coating technology and the directional pollution-free, consistent operation, and diversified development direction of coating finished products, it is used in the processing of foreign trade export product packaging. China will also achieve great results, and glazing technology will be the most promising packaging printing surface processing technology.