Ⅰ. The characteristics of metal printing process
1. The printing material is a variety of metal sheets with large differences in performance from paper
The metal printing process should take the basic characteristics of the metal printing material as the most important research object of the printing process, such as the selection of metal printing equipment, the matching of various printing auxiliary materials, the processing of pre-printing graphic information, plate making and other technological processes sheet metal requirements for them.
At present, the commonly used metal sheets can be divided into three types: hard, neutral and soft according to their hardness (for example, chrome-plated steel sheets are hard, ordinary sheets are neutral, and aluminum and aluminum alloy sheets are soft).
Therefore, in the process of metal printing, the adjustment of the cylinder pressure and the selection of the lining material should be carried out according to the hardness of the substrate. Generally speaking, it is better to use soft lining for hard metal plates, while neutral lining is suitable for neutral and soft metal plates.
2. Coating plays a pivotal role in the quality of metal prints
Metal prints generally have to be processed through various post-processes before they can be made into various metal packaging containers. Metal printing plays a key role in the beautification and decoration of metal packaging containers.
In order to make the pictures and texts printed on metal plates bright and dazzling after being made into packaging containers, the special effect of coatings is inseparable.
The role of the coating is in two aspects: one is to increase the adhesion between the metal and the ink layer; the other is to protect the ink layer well, and at the same time increase the brightness of the pattern, and does not change color during the production process, no paint peeling.
3. Use special inks with special properties
From the requirements of the ink drying method in the printing process, the biggest difference between the surface of the metal plate and the paper is that the surface of the metal plate is smooth and has no absorption capacity, while the paper is porous and the ink can penetrate. Therefore, the drying of metal printing ink mainly includes two methods: oxidation conjunctival drying and volatilization drying.
At the same time, because metal plate printing is generally made into metal packaging container packaging products, especially packaging food (such as food cans, beverages, etc.). Therefore, according to different internal products, metal printing inks are generally required to be resistant to high temperature, retort, paint, fade, non-toxic, friction-resistant, water-resistant, and grease-resistant.
4. The metal printing operation is different from the offset printing operation of ordinary paper
The feeding table should be carefully considered when the printing machine is manufactured, and the best blowing force and suction force of the blowing nozzle should be considered for metal plates of different thicknesses, different qualities and materials, and the blowing nozzle and nozzle should be adjusted at any time during the printing process. The air volume of the suction nozzle to achieve the best feeding state.
At the same time, a horseshoe-shaped magnet is added at the feeding place to overcome the adsorption force between the metal printing plates, and combined with the blowing force of the blowing nozzle, the metal plates are smoothly and continuously conveyed.
When adjusting the pressure of the cylinder, in addition to the thickness of the metal plate, the transfer status of the dots should also be considered (the pressure is too small, the dots of the printed matter are vacant, the pressure is too large, the dots are seriously deformed, and the pictures and texts are distorted)
In the whole metal printing process, the finished product should always be placed in the center. Metal printing products are generally intermediate products. The final purpose of metal printing is to obtain finished packaging containers that meet the requirements, and the printing effect is finally displayed on the finished product.
Therefore, every link in the printing process should be centered on the finished product.