Corrugated boxes are a kind of ordinary paper packaging products that are inseparable from our life and production. The printing quality of corrugated boxes is not only related to the appearance quality of the corrugated boxes, but also affects the sales prospects of the packaged products and the image of the product manufacturer. Therefore, it is particularly important to analyze the problems of how to improve the surface printing effect of corrugated boxes, how to choose a suitable printing process, and to further reduce the cost of carton processing. Here we will discuss these aspects.
1. The processing technology of corrugated board is mainly divided into two categories
1. Production process of automatic corrugated board production line. The production process of corrugated board is widely used. It has the advantages of large production batch, large carton forming volume, and good corrugated quality. The corrugated cardboard produced by this process is usually made into cartons through processes such as water-based printing, slotting, gluing, and forming. The cartons produced by this process are mainly used as transport packaging.
2. Semi-automatic corrugated cardboard production line production process The corrugated cardboard production process is to print the face paper first, and then laminate with the corrugated core paper and cardboard. The corrugated cardboard produced by this process is conventionally formed into boxes by die-cutting, indentation, and nailing. The carton produced by this process has good molding quality and good surface treatment effect. The cartons produced by this process can be used as sales packaging.
2. Conventional carton printing methods Conventional carton printing methods mainly include flexo printing, offset printing and screen printing.
1. Flexographic printing corrugated boxes The conventional flexographic printing corrugated box process is to print directly on the corrugated cardboard, using water-based ink, so some people call this process watermark. Direct flexographic printing has the following characteristics:
(1) Large format. The maximum width of wide-format flexographic printing presses can reach 2.5m~2.8m.
(2) The price is low. The flexographic plate has high printing durability and can be reused; the price of ink is also low.
(3) It can be linked to production, such as printing, grooving, creasing, ordering (gluing) boxes, bundling, etc., can be completed in one machine.
(4) The strength of the carton is reduced relatively less. Since flexo printing is light pressure printing, it has little effect on the strength of corrugated cardboard.
(5) The printing accuracy is not high. The conventional offset printing and screen line number is 175 lines/inch, while the flexographic carton conventional screen line number is 35 lines/inch to 65 lines/inch, which is a low-precision printing method and is most suitable for printing text line drafts. Although the quality of four-color image printing has improved in recent years, there are still limitations.
(6) Plate making is easy and difficult, text line draft making is easy, and four-color image making is more difficult.
(7) The stability of printing quality is not good, which is mainly reflected in the difficulty of controlling the darkness of printing ink. The direct flexographic printing process is suitable for the first type of carton production process, and is currently widely used in my country’s carton factories.
2. Offset printing corrugated paper box Conventional offset printing corrugated paper box uses indirect printing method, that is, the carton face paper is printed first, and then the printed face paper is mounted on the corrugated cardboard.
Because the resolution of the PS plate is relatively high, it can print very fine printing patterns. At present, most of the high-end corrugated boxes used for sales and packaging in my country are offset printing products. Offset printing corrugated boxes have the following characteristics:
(1) It is not suitable for the cardboard linkage production line, but only suitable for the single-face corrugating machine, and the production efficiency is low.
(2) The format is limited, generally smaller than the flexographic carton format.
(3) The printed products are very fine, and the number of screen lines can reach 150 lines/inch to 200 lines/inch.
(4) It is easy to make a plate, and it is a regular plate making for the PS plate.
(5) Surface finishing, such as laminating, glazing, etc. can be carried out.
(6) The printing cost is high.
(7) The printing quality is relatively stable.
3. Screen printed corrugated boxes
The screen printing process of corrugated boxes uses direct printing. Since the ink drop rate of the screen plate is proportional to the hole distance of the screen, the resolution of screen printing is not high, and the image accuracy is low. The conventional screen line number is 60 lines/inch to 80 lines/inch. Screen printing corrugated boxes have the following characteristics:
(1) It is not suitable for linkage production line, and the production efficiency is low.
(2) The printing format can be large or small.
(3) Printing can be completed before mounting and boxing, or after mounting and boxing.
(4) Suitable for printing non-fine products. The ink color of screen printing is thick, so its color saturation is high, and the visual effect is strong, especially for spot color printing, the effect is better.
(5) The plate making is easy and the plate making cost is low.
(6) The printing cost is low.
(7) The printing quality is relatively stable.
Third, the new printing method
1. When the plastic gravure composite carton process adopts a single-sided corrugated production line, if the surface paper needs to be covered with a bright film after the printing is completed, and the production batch is large, you can not print on the surface paper, but use the gravure method on the plastic film Finish the gravure printing and add the white background, and then compound the printed plastic film and the facial paper first, and then complete the box making according to the conventional carton forming process. The characteristics of this process are:
(1) The production cost of the carton is low.
When the production batch is large, this process can greatly reduce the printing cost of facial paper and the material cost of facial paper. Because facial paper does not require printing, non-coated white paper can be used, which greatly reduces the cost of facial paper.
(2) Exquisite printing. Because plastic gravure is used, the printing effect is comparable to the offset printing effect. Special attention should be paid to the use of this process. When making plates and printing, the dimensional changes and deformation of the plastic film must be fully considered; otherwise, the carton paper will not be aligned with the lower cardboard.
2. The art paper gravure composite carton process can be used when the production batch is relatively large, no film is required, and the printing effect is required to be good, and the cost is low. The process is to print thinner coated paper with a paper gravure printing machine, and then compound the beautifully printed coated paper with ordinary slag board paper or box board paper to form the carton surface paper as a whole, and then carry out the mounting and normal carton forming Processing. The characteristics of this process are:
(1) The production cost of the carton is low. The main reason for the cost reduction is to change the whiteboard paper to low-weight coated paper combined with cheap cardboard paper, which reduces the material cost.
(2) Exquisite printing. The printing effect of gravure on paper is very exquisite.
(3) Gravure printing is more complicated and costly, so it is not suitable for printing carton products with frequent revisions.
(4) The printing factory must carefully explore the operation and control methods of the process of face paper compounding and box making, continue to accumulate, and implement rationally, otherwise it will easily lead to an increase in the rejection rate.
3. Direct offset printing process for corrugated boxes The direct offset printing process for corrugated boxes is relatively mature in foreign countries. It is to print corrugated cardboard directly on a special offset press. Suitable for processing thin corrugated boxes.
This process can not only ensure the good formability of the carton, but also complete the exquisite facial paper printing, but the printing machine used is relatively expensive, and it is not suitable for the demand standard of our country at present, and is not suitable for the carton industry to adopt in the near future. , But in the next few years, this process may become the new development direction of my country’s high-end carton printing.
4. Flexo pre-printing and gravure pre-printing corrugated carton process
This year, the development has been relatively fast. Both of these processes first print the face paper in the form of roll paper, and then complete the production of corrugated cardboard on the automatic corrugated cardboard production line. The printing quality and molding quality of the carton are relatively high, but the investment is relatively large, and it is not suitable for small batch production.
In the domestic carton industry, the three conventional corrugated box printing methods are relatively common, and they have become the mainstream method of corrugated box printing. However, the new type of printing box-making method has not been fully grasped due to the hot spots of equipment, materials, technology, operation, etc., and the investment is relatively large, and the difficulty of promotion is still relatively large. However, in order to improve the grade, reduce the total cost of the carton, obtain the maximum profit, and increase the competitive advantage in the market, the carton enterprise adopts a new type of printing carton technology is imperative.
From the perspective of the overall development of the carton printing process, the plate-making and printing technology of the flexo direct printing corrugated carton process needs to be improved as a whole, plastic gravure, carton gravure, and web offset printing processes need to be promoted and improved, direct offset printing and pre-printing The production process of corrugated boxes should also arouse our attention.