Eight factors affect the quality of plastic gravure printing

In plastic intaglio printing, there are many factors that affect product quality. Based on years of practical experience, I have summarized the eight major elements of controlling plastic intaglio printing, and compiled them to make it easier for everyone to remember.

1. Before explicitly printing on the surface and printing on the inside, first determine whether the printing method is surface printing or in-line printing. Then determine the type of film and distinguish the corona treatment surface; determine the type of the printing plate (inverse or genuine); Different types of thinners are used for inks.

2. To determine the appropriate temperature and humidity printing shop temperature is too high, excessive humidity can easily lead to prints appear to stick back, fade, color transfer, adhesion, poor solidity and other phenomena, in severe cases, will make the ink decomposition, printing does not color. If the workshop is too dry, in the case of high printing speed, static electricity will be generated and the ink will move on the film. In the case of slow printing speed, the printed matter will be dull, and the phenomenon of dry printing, pasting, etc. will occur. General printing shop temperature control in 18 ~ 25 °C, relative humidity control in 55% ~ 75% is appropriate.

3. The balance of plate cylinder positioning In general, the balance of the plate cylinder depends on the printing machine and the plate-making roller, but it is also affected by the installation. When installing, be sure to determine the position of each color plate cylinder and install it firmly. The position of the plate cylinder depends on the plate line on the plate cylinder and the length of the plate cylinder. For keyless plate cylinders, the screws must be tightened.

4. The pressure of the roller should be suitable
Embossing roller is uneven, there will be missing printing, uneven printing and other phenomena; the pressure of the roller is too large, the printing pattern will appear ghosting, unclear, dull and other phenomena; the pressure of the roller is too small, there will be shallow net Some are not colored and the text is not clear. Therefore, a high-quality rubber roller should be selected, and the pressure of the rubber roller should be adjusted during printing.

5. Squeegee angle adjustment
The angle between the doctor blade and the plate cylinder is generally controlled at 45-65°, and can be further adjusted according to the depth of the cell site and the printing speed. Adjustment should pay attention to the distance between the blade and the embossing roller to match the printing speed. At the same time, give the blade a proper pressure. The size of the squeegee pressure can be adjusted according to the depth of the printing plate, the superimposition order, and the like.

6. Good work viscosity adjustment
Adjust the working viscosity of the ink, on the one hand to take into account the printing speed, printing speed, should choose fast-drying thinner; printing speed is slow, you should choose slow-drying thinner. On the other hand, the volatile diluent should be added in time during the printing process, and it is best to add the ink to the ink fountain to ensure the consistency of the print.

7. Tension control must be strict
In order to facilitate printing and improve the printing speed, the magnetic powder tension control system has been installed on the gravure printing machine to control the tension automatically. Some high-grade gravure printers also installed computer tracking and automatic control systems in various color groups. For a printer without a computer color registration system, the tension in each color group must be manually adjusted. When adjusting, consider the printing speed and the tension.

8. Drying system to support
The drying system affects the speed of the gravure press. From single ovens to double ovens and multi-function ovens, bake tunnels, regardless of the drying system, the main role is the same, one is to increase the speed of the printing press, the other is to improve the adhesion of the ink on the film surface, so that the diluent in the ink Dry to prevent false drying, causing back odor or odor after bag making. Therefore, the drying system should work well with the printing press speed, and then adjust the oven temperature and air volume according to the size of the pattern area on the print.

In short, to print a good product, every aspect cannot be ignored.

Plastic gravure printing port
The seals printed on the table confirmed that wet and dry quality is very important.

The balance of the roller balance is carefully searched and the angle of the scraper is mastered.

Ink viscosity at any time, the pressure of the rubber roller should be kept firmly

The printing speed oven cooperates well, neglecting the tension color running.

Prevent offset gold (silver) ink discoloration
The printed gold (silver) products have the advantages of delicate imprinting, good metal texture, strong hiding power, high floating force, strong metallic luster, and low cost. However, during the printing process, the color of gold (silver) ink often fails to change color. The following analyzes the causes of the discoloration of gold (silver) ink and suggests preventive measures.

(1) pH of paper
In the pulping and papermaking process, if the pulp contains organic acids or there is residual chlorine when bleached, the paper will become acidic; and the addition of alkaline fillers and pigments will make the paper alkaline. If the paper is acidic, it will inhibit the imprinted oxide film on the surface of the paper, which will slow the drying speed; if the paper is too alkaline, alkaline substances will be continuously transferred to the water bucket during the printing process. Neutralization of the solution affects the pH of the fountain solution, resulting in discoloration and deterioration of the remaining ink, and emulsification of the ink, resulting in turbidity. Therefore, the paper has a pH of 7 and is neutral, which can effectively prevent discoloration of the gold (silver) ink.

(2) pH value and ink balance of fountain solution
In the offset printing process, the acidic substances in the dampening solution can play a role in cleaning the plate, but if the acidity is too strong, the gold (silver) ink may be discolored, causing it to lose its metallic luster, and it is also easy to cause the printing plate to print and the printing is not easy to dry. The quality of the backside of the printed product is not good enough, and the acidity is too weak. The printed version of the screen can easily become dirty and pasteboard. Therefore, the general fountain solution pH is controlled at 5 ~ 6 is appropriate.

The ink balance is the use of as little moisture as possible without the printing plate being dirty or paste-free. The emulsification amount of the ink is controlled within a range of less than 25%. Because the water supply is too large, gold (silver) ink is easily emulsified, resulting in ink (silver) ink, the ink is too light, the ink layer is dull, the color is not bright and other ills; and the water supply is too small, it is easy to make the layout Dirty, greasy, and graded paste problems. Therefore, it is critical to control the ink balance.

(3) Printing speed
If the printing speed is too fast, strong friction between the ink rollers will easily occur, and the heat generated will discolor the gold (silver) ink. The printing speed of general offset gold (silver) ink is controlled at 5000 pieces/hour.

(4) Oxidation of Copper Gold Powder and Aluminum Silver Paste
Copper powder and aluminum silver paste are easily oxidized and discolored. Therefore, unused copper powder and aluminum silver paste must be kept from the air tightly closed, and the storage time should not be too long. In addition, the gold oil used in the deployment of gold (silver) ink must be a fast-drying, fast-setting, high-viscosity resin oil with low oxidation and neutrality. In order to avoid oxidative discoloration of gold (silver) ink for a long period of time, it is best to use it immediately.