The development of metal containers has not been plain sailing. During the period of the sixth five-year plan, the development was just starting slowly. During the seventh five-year plan, the market supply and demand relations were relatively normal and showed a great trend of development. "August 5" period is the heyday of metal container printing: "September 5" is a stable period; The tenth five-year plan is a crucial period of development. "11 · 5" is the quality competition period of metal printing, which is a special period of winning the market by quality. Therefore, based on the printing principle and the printing technology as the research object, the key to obtain high quality metal printing products is the process quality control in the printing process. Tinplate printing since color separation, plate burning, proofing, printing to printing and paper products printing process has many similarities, but Indian, after all, is a special kind of technological process of each procedure, design if seem similar but different here is simple to operate about tinplate printing process design process and control points.
1, color separation
Printing equipment at home and abroad is given priority to with monochrome printing presses and two-color printing presses, due to limited by printing equipment and printing materials and the effect of customer special packaging requirements, using the traditional way of color separation into printing color effect may differ with customer provided by the original very much, also left behind potential dangers for the subsequent printing production. In order to avoid multi-color printing overprinter is not allowed, scratch phenomenon, color difference is obvious color is not bright, defective, etc. In addition to many back to the dot and thick network line, so that the total network points to reduce the print dot expansion is smaller. So color separation is the key to printing metal products.
Printing iron proofing is not only the inspection of color separation film but also the pre-quality analysis and control of printing iron products. It USES the traditional offset printing printing method. In the process of proofing the separation of color samples as a reference for the control of the printing process, so that the printing quality and stability of the color can truly reproduce the customer confirmed samples. At the same time, because the printing iron is rarely the final product of the components, and often is a variety of containers, covers and miscellaneous products and other processing process components proofing and testing the coating processing performance and matching. Therefore, in this process we need to process into finished products, put into the content, that is, molding test, such as food pot to the tank sealing, shelf life, freshness test.
3. Confirm the drawing
Printing iron drawings to determine the tinplate positioning rules product arrangement and product coating used by the roller three turbulence. One of the tin positioning rules refers to the bite, lean on the direction and size they are the basis of printing and printing; The arrangement of products is printing according to the different nature of the different arrangement of products, in the determination of the arrangement of the process need to consider the printing iron can accept the minimum size and maximum size at the same time to make the arrangement of the most economical; Is rubber roller coating coated tools for should be coated within product coating method has full version tubu, vertical blank coating, cross blank coating product is less, and outside coating product coating method are three empty for food we usually use horizontal coating spray cans with vertical blank coating, miscellaneous cans and cover product usually use full version tubu, glazing coating has a vertical blank coating and full version of the coating and two kinds of coating method.
4, plate burning
For pot, cover type printing, the production of lithography will most of the same picture according to the determination of the product drawings into groups to make Yin diagram or Yang diagram, using the sun machine for exposure plate making. In this way, dozens of identical images can be printed on one sheet at the same time using PS plates in the production process, and other printing and plate-making methods such as exposure time, development, fixing, developing and so on.
5, determine the substrate material
As a result of different product use and molding equipment for tinplate thickness, tin layer, hardness and annealing mode have different process requirements so we according to the nature of the products to the above factors to determine the turbulent it should meet the printing requirements and to meet the requirements of canning, punching box, and determine the final printing surface.
Printing iron is not the ultimate goal, but the beautification means of metal packaging, the purpose is to make all kinds of metal containers, such as tin cans, various types of bottle caps, toys and so on. To make printed on the metal plate on the picture and text bright and dazzling, inseparable from the special role of paint, it increases the tinplate and ink film layer between the adhesion force, on the ink film layer has a good protection effect at the same time increased the brightness of the pattern so that the product has metal color and in the final molding process does not change color, paint. For food can coating it can prevent the contents of chemical and biological pollution, reduce the possibility of leaking cans, preserve the original flavor and color of food, extend the storage time of the contents, make the contents easy to pour out of the container. In addition, it also has some special visual effects such as gold cotin, explosion polish, wrinkle oil, bead polish, matte oil and so on.
Iron printing coating is mainly composed of film-forming materials, pigments, driers, auxiliaries, solvents, etc., from the coating mode and function can be divided into internal coating, external coating and varnish 3 kinds of coatings usually according to the properties of products and drawings to determine the use of coating and coating mode. As a result of tinplate coating a certain film thick coating to go into the oven for baking, and baking temperature is very important.
Dryer tunnel usually consists of three parts, namely preheating area, heating area and cooling area. In the preheating zone at room temperature printing parts gradually rise to the required heating temperature, from the perspective of technology, the smaller the area, the shorter the better. Heating area is the main area of thousand dry, the requirement of uniform temperature distribution: cooling area requires rapid cooling. And what we set in the process is zone 1 and zone 2 temperature. The first zone is the heating zone, in which the iron sheet temperature rises from room temperature to the required temperature. All solvent volatilization processes on the tomb are carried out in this zone. The second area is the baking area, whose main function is to maintain the set temperature reached in the first area, which is also known as the PMT baking temperature in the paint and oil specified in the product specification of the PMT supplier. We do not regularly on the oven temperature of the oven to correct, so that the baking temperature in line with the process requirements, at the same time baking time is also very important, we use paint before broadcast to determine the PMT and time, and time mainly by limiting the speed to achieve. If the time is too short coating powder power is not good, soft; Too long will become brittle when cracking can also cause yellowing.
As a result of printing ink is directly printed in no absorption capacity of smooth metal surface so printing ink drying mainly depends on the ink's own oxidation conjunctival reaction and ink solvent volatilization. It should have good adhesion, processing resistance to cooking and sterilization, high temperature baking resistance, resistance to water and other properties, but also have offset printing ink printing suitability, such as liquidity, fineness, etc.
(2) color series
Most of the monochrome or two-color printing machine, in the printing color sequence usually follow the following principles: first printing dot coverage area is small, after printing dot coverage area is large; Ink transparency of the dark first printing, transparency good after printing; First printing flat screen after printing solid color: warm tone after printing magenta yellow, to cool tone after printing cyan.
The adjustment of the printing press
Tinplate specifications, thickness changes often according to the situation of the press rules, single and double sheet detector printing pressure, suction nozzle, etc., while the blanket is often replaced.