Section 2 Metal Printing - 3

(II) Printing 1. The color separation plate making process for color separation plate printing is basically the same as general printing. For the characteristics of metal printing, there are also special requirements.
(1) Chain-shaped or circular dot screens are chain-shaped dots. In the midtones, dots and dots are in contact with each other. They are diamond-shaped dots connected in a single direction or with circular dots. Therefore, the sudden change in the midtones is more common than usual. The square points have been eased, and this dot shape is beneficial for tin foil printing tone reproduction.
The length of the edge of a circular dot is smaller than the edge of a square dot of the same proportion, so its enlargement value is also small. However, the circular dot has a tendency to jump sharply from around 70%, and the dark tone level is easy to paste. Therefore, considering the tone of the manuscript, circular dots for metal printing are also feasible.
(2) Use coarse meshes as much as possible. Because the thicker the number of shielded mesh lines is, the total number of Internet access points is reduced, the shorter the total edge length is, the smaller the amount of printed dot enlargement under the same conditions, and the current state of tone transmission based on tin printing. , Choose coarse net to be better than fine net, especially for biscuits, candy packaging, etc. to use 48 lines/cm.
(3) The use of the standard three-primary process to reproduce the standard three-primary process used in printing to replace the multi-color version of the dedicated color and auxiliary color is an ideal replication process. Because multi-color printing increases the number of overprints, it is prone to overprinting, frictional damage, etc., and consumes hours of work, raw materials, increased costs, long product production cycle, colors are not bright, and there are many defective products.
(4) Application of the white plate First, the tin plate is printed in white before it can be printed with a fine pattern. The general printing iron is a full version of white, but there are gold printing, pay attention to the following golden pad can not be white, otherwise not achieve the metal eye-catching effect. In the case of a white version, it is necessary to consider the combination of the white version and the gold version, and press each other to prevent the iron edges from being exposed during the printing process.
(5) Considering the processing and forming of tinplate after printing. The following two points should also be taken into consideration when making plates: Fully grasp the technical requirements of various types of manuscripts, and rationally arrange the layout according to the requirements for punching.
1 to fully grasp the technical requirements of various types of manuscripts. Except for some label products, most tinplate printing processes include can making, box making, etc. Before copying, it is necessary to clarify the technical requirements for can making. Divided from the product's tank type, there are square tanks, round tanks and shaped tanks. The process of splicing cans can be divided into tanks, tin cans, high frequency resistance welding cans, and hot melt adhesive cans. The canning process can be divided into three pieces of cans and two pieces of cans. In addition, there are some special finished products, such as a stationery case with a chain and various types of bottle caps.
Not only must the end of the tank consider its shape, but also the size of the mouth. The size of the mouthpiece directly affects the splicing effect of the graphic and text, and severely causes the loss of the original style and picture of the graphic text. From the point of view of the plate making, the drafting should be carried out in strict accordance with the requirements of the size of the stipulated process or other splicing methods. Understanding the canning process of different products is a basic requirement for plate-making personnel. The mouth is divided into double end and single end. Usually the double end of the mouth is left 10mm to the right 2.5mm, and the single end to the left is 5mm to the right 2.5mm. As shown in Figure 3-8.
For teapots and other three-piece cans, it is necessary to consider the perfectness of the joints of the can body, but also to take into account the harmonization of the tint and can body tone, as for solder cans, high-frequency resistance solder cans are required to stay in the seams Appropriate clearance for easy welding. Generally, the clearance is between 5-10mm, that is, no paint or printing surface is allowed in this range, otherwise the welding effect will be affected.
2 Reasonably arrange the layout according to the stamping requirements. Tinplate prints also meet the requirement of punching, so the positions of various products are reasonably and economically arranged on iron sheets of certain specifications (generally 508mm x 712mm, and some special specifications such as 712mm x 1024mm, etc.). It is an important job for copying staff. For manual platemaking, it is to make a good grid. It must be carefully designed when properly arranged. In the layout, various factors should be taken into account, such as different canning requirements, different punching characteristics, printing process requirements, raw material specifications, etc., must be comprehensively and carefully scrutinized and refined.
In the typesetting, first, understand the size of the tin print; secondly, in order to make canned products, arrange as many individual product images as possible; and thirdly, consider the technical requirements during printing. The position and orientation of the pattern are as far as possible to meet the requirements of the printing operation. The four corners of the plates are indispensable.
For the arrangement of various product patterns, the principle of saving materials should be adopted, and at the same time, it should be suitable for the production characteristics of can making workshops. Pile blanking, cold cream box lid and bottom, tea pot lid, powder box lid punching blanking products, according to different punching methods, Ho Ho can be divided into two categories: The first category is automatic blanking or digital programs Automatic punching, the other is manual punching. In typesetting, different types of patterns should be used for different types of layout according to the different requirements of punching. In general, when you typeset blanked products, you should be full version of cable. However, hand-punched products cannot be fully printed, but must be easily cut and hand-punched. Usually two flowers or three twisted flowers are mostly. As shown in Figure 3-9.
Whether it is a hand-punched product or a blanking or digitally programmed automatic punching product, the spacing of the arranged products must have a certain degree of regularity. In this way, the figure of the can is not skewed. For hand-punched products, there is a gap between the first and last pictures of the final product. There is no such requirement for blanking or automatic programming of digital programs. The basic principle of blanking press punching is stamping the stamping of the iron sheet prints in accordance with the requirements of two strokes of vertical and horizontal strokes. After punching one line of products, the second line is immediately punched. The line conversion process is automatic. Until the entire print has been fully stamped. Then manually reject the waste. Manually punch the second print. This cycle. The basic principle of the automatic control of the digital program is similar to that of blanking machine punching. Of course, if the input program is complicated, its working principle is correspondingly complicated, and the high difficulty movement that the automatic blanking rack cannot accomplish is completed.
2. Printing plate printing plate printing is the use of PS version, the plate making process is basically the same as offset printing plate. If dry offset printing is used, photosensitive resin relief printing can be used for printing.
3. Printing ink Since the substrate is a non-absorbent metal surface or coating surface, it must be machined after printing. Therefore, the metal printing ink should have special properties compared to the ordinary lithographic offset ink.
(1) Composition of Metal Printing Lithographic Offset Printing Ink and Raw Material Metal Printing Lithographic offset printing ink generally consists of the following components, as shown in Table 3-8. Table 3-9 lists the main raw materials.
Table 3-8 Example Composition of Metal Printing Offset Offset Inks

Table 3-9 Raw Materials for Metal Printing Offset Offset Printing Inks
additive
The pigment should have heat resistance and solvent resistance, and the linking material should have good heat resistance, light resistance, steam resistance, and processing performance. As a raw material for food printing inks, hygiene and safety should also be taken into account. Printing inks must comply with the provisions of the Food Sanitation Law.
(2) Properties of Metal Printing Lithographic Offset Printing In general, metal lithographic offset printing inks should have the following properties:
1 ink fluidity. Because the surface of the substrate cannot be penetrated, the phenomenon of dot enlargement is apt to occur. For this reason, large drying equipment such as a drying oven is generally used at the printing site. The dry box in the workshop will cause the temperature of the printing environment to rise. If there is no ink temperature adjustment system that changes with the temperature, the fluidity of the ink will increase, and the reasonable physical state will be lost. This is the main cause of the ink emulsification and thickening of the graphic and text. one of the reasons. Therefore, compared with paper printing inks, metal printing offset inks should use high viscosity inks;
2 wetting water adaptability. The metal surface is a non-absorbent surface, and there is too much wetting water on the plate surface. In addition, as the temperature of the plate increases during the printing process, the viscosity of the ink will decrease and the ink will be emulsified. Therefore, the water film thickness on the plate surface should be controlled. To achieve the balance of water and ink on the layout in order to ensure the suitability of moistening water;
3 ink drying and heat resistance. Metal plate printing generally uses a large drying oven for heating and drying. If the ink on the surface of the substrate is not solidified and the molding process or heat pasteurization process is performed after printing, adhesion can only be performed by drying the early background color. Therefore, an ink film having sufficient hardness and good processability is required. Therefore, when used in a drying oven for heating, an appropriate ink layer should be hardened, and discoloration or discoloration should be avoided. This requires that both the binder and the pigment be guaranteed.
4 solvent resistance and wet wet coating properties. In metal printing, in order to improve the adaptability of the post-processing and processing, and to make the printing surface have a certain degree of gloss, it is necessary to perform the coating coating before the ink is not completely dried at the final step of printing, that is, to wet the wet coating surface. In the heating and drying process, the normal state during painting is maintained, and at the same time, care must be taken not to generate wrinkles and cracks. For this purpose, pigments that are insoluble in solvents should be selected, and