How to make carton box Ⅶ : Carton printing process category
The product packaged in the carton, only need to open the case, just see the appearance of the carton, you know what is inside, is a very important part of the carton production, the embodiment of this link is printing.
Carton printing uses the following three common processes: offset printing, pre-printing, and flexo printing after corrugated board. There is also a digital print that is gradually accepted by the market.
The following explains the difference between these several printing methods.
We all know that water and oil can’t be mixed. (I don’t know if modern technology has done it?), offset printing uses this principle. The graphic part and the blank part of the printing plate are basically on the same plane, and the ink-containing (ink eating) ability is not good.
The most troublesome thing is that when doing large-area field dyeing printing, it is often necessary to do two-page superimposed printing, otherwise there will be insufficient color saturation for the printing required. But the small characters and the dot parts will be printed very beautifully.
When printing, the water is first applied, and the graphic part of the printing plate is ink-repellent, and the blank portion is hydrophilic and oil-repellent, forming a relatively stable unit. The graphics on the plate are first transferred to the blanket cylinder and then transferred to the paper, which is an indirect printing method.
This kind of printing method has a long route from the ink to the paper because of the structure. The most difficult to control is the ink balance, that is, it is difficult to print the thickest ink with a minimum amount of water (dampening solution). of.
Usually, it is printed on a single sheet of paper. After printing, it is transferred to the corrugated board, and then the carton forming work is carried out. For small batches of cartons, the time is too long, the process is too much, and the relative efficiency is low.
There are two ways, gravure pre-printing and flexographic pre-printing.
a. Gravure pre-printing: usually round paper round printing.
The printing plate is a chrome-plated roller, which is etched by photography, and now basically uses an electro-engraving process to make the graphic department lower than the surface of the roller (the image portion is lower than the blank portion).
During printing, the plate cylinder rotates in the ink tank, and the ink on the surface of the drum is scraped off by an elastic steel scraper (thickness 0.15 mm, knife edge grinding treatment), and the concave image is applied by an impression cylinder (rubber roller). Transfer of text to paper Above.
The ink used is usually solvent or UV type. It is characterized by high efficiency and long service life of the printing plate. Field dyeing printing is the strength of this method, the ink layer is thick, but the printing layering is better than the strong dot-grading than the offset printing but better than the flexographic printing.
b. Flexographic preprint: belongs to the category of letterpress printing, the graphic part is higher than the blank part, like a seal. The reason why it is called a flexographic plate is that the photosensitive resin plate has very good elasticity.
The thicker the plate, the lower the hardness, so the pressure control needs to be done very well. Preprinted plates are typically 1.14 mm to 1.7 mm thick and have a Shore hardness of 55-70.
Because of the high hardness, the cable can also be made very high, generally using 133 lines, and even more than 175 lines of printing, very delicate. From the visual point of view, there is not much difference from the offset printing, and the ink layer printed in fact is not much thicker than the offset printing, but it is much higher than the offset printing.
After the pre-printing (including glazing), it is directly applied to the corrugated board production line as a facial paper, and bonded to the corrugated board to become cardboard.
Because the tile wire has many high-temperature processing links, the temperature resistance of the ink and the varnish is also high, and at least it can withstand a high temperature of 170 degrees.
Then, it is cut into a single corrugated cardboard on the rear end of the tile wire, and finally formed into a molding process.
This type of printing is very large for some batches, and the printed patterns are very beautiful. Very beautiful cartons, such as beer and beverage products, are very suitable.
3. Water-based ink flexo printing
This is also the most widely used carton processing technology, which can realize the process of wire forming, slotting, round die cutting, flat die cutting, sticky box nailing, packing and so on.
The printing plate uses a photosensitive resin plate, the difference is that it is printed directly on the corrugated board, so the requirements for paper feeding and pressure control are higher.
Because the corrugated cardboard type can not be flattened, the plate material is required to be not too hard. Generally, the Shore hardness is 30-35 and the thickness is 3.94 mm. Used in conjunction with high resilience printing pads. Because the plate is relatively thick, the plate will have a large deformation in the actual printing, which has an impact on the printing quality. At present, there is a trend toward the development of thin plates (3.18mm and 2.84mm).
Because these years I mainly do this kind of printing equipment, this is my specialty, the plate used in this printing method and its related requirements, the follow-up will be specifically explained.
We have all used inkjet printers. This type of printing can be simply an enlarged version of an inkjet printer. The difference is that one is on paper and the other is to print pattern text on cardboard. In addition, because the ink is more expensive, the cost is higher, but there is no need to make a printing plate.