How to achieve perfect printing

1. Pay attention to the sample sheets

(1) Sampling inspection in printing. Shortly after entering the formal printing, there will be some changes in the amount of ink supply and water supply determined at the time of printing. Frequent sampling inspection and readjustment should be made. When the printing speed remains unchanged, ink supply and water supply are in a stable state, the sampling inspection shall be carried out at the ratio of 500 to 1000 sheets per printing.

(2) Insert warning note. In formal printing, as a sign, a long warning note should be inserted to facilitate the inspection in the later process.

2. Pay attention to the change of water supply

(1) Attention should be paid to the change of water supply in the initial stage of formal printing. There will be some changes in the amount of water used in trial printing and after entering the formal printing. We must pay attention to the duplication of sample sheets and water carriers, and adjust the amount of water supplied to the printing plate at the same time.

(2) Pay attention to the change of water supply in the process of formal printing. It is necessary to pay close attention to the influence of the heating of the main body of the machine and the ventilation condition in the workshop on the water supply. Alcohol wetting plate should pay attention to the cooling device of the wetting system, control the temperature of the wetting liquid well, and the printing plate will be dirty if the water supply is too little. Excessive water supply will cause ink emulsification, which will bring a series of problems. For example, the gloss of printing products, paper flexibility and improper overprinting, delaying the drying of ink and so on.

3. Pay attention to the change of ink

(1) Pay attention to the ink in the ink bucket. Ink from the bucket roll and the bucket scraper gap between the ink, is the weight of the ink and is naturally squeezed out. Therefore, the amount of ink in ink bucket directly affects the output of ink. Therefore, attention should be paid to keeping a certain amount of ink in the ink bucket. In addition, printing ink has thixotropic properties. If placed in ink bucket for a long time, the fluidity will gradually deteriorate. Therefore, it is necessary to mix in ink bucket with ink knife or install ink mixer.

(2) Prevent ink from drying on the machine. When the machine is shut down for a long time, such as eating and resting, the ink on the roller and the ink surface in the ink bucket will dry. Drying inhibitors can be sprayed at places where drying needs to be prevented.

(3) Pay attention to the uniformity of ink, the density of printed matter changes depending on the amount of water, room temperature and machine speed. It should be checked regularly in comparison with the standard sample sheet. Attention should be paid to preventing the uneven ink color.

(4) Maintaining the pH value of the wetting solution and adding auxiliary agent in the ink will easily affect the pH value of the wetting solution. If the pH value increases, it will easily cause the printing plate to become dirty, so special attention should be paid to it.

4. Pay attention to dirty rubbing on the back

The dirty back is due to the slow drying of ink, thick ink layer and high smoothness of paper, which makes the ink on the surface of the sheet stick to the back of the previous sheet.

5. Pay attention to duplication failure

The so-called duplication is to use a plate to print the image offset, in the printing can see double, triple images. There are many reasons for duplication, such as paper, teeth, drum, rubber cloth, printing speed, ink viscosity and other factors are very complex. The following methods can be used to check the causes and deal with them.

(1) Printing twice, observe the overprint accuracy, check and adjust the side gauge drawing force, feed, press wheel and press parts.

(2) Check the tension of rubber cloth, new rubber cloth is easy to relax, pay attention to tightening step by step, but not too tight.

(3) Check drum liner and printing pressure.

(4) Check the paper suitability. Paper with poor adaptability, especially the paper with wavy mouth, is prone to duplication, so it should be checked.

(5) Reduce the viscosity of ink. Ink viscosity is high, paper can't peel off rubber cloth smoothly, so that the paper's tip part is unstable, resulting in ghosting. The viscosity of the ink can be reduced appropriately.

(6) Adjustment of teeth gripping. Poor regulation and improper maintenance of teeth are one of the major causes of duplication. Therefore, the regulation and maintenance of teeth should be done regularly to keep them in good working condition.

6. Pay attention to checking overprints

Continuously take out 20 to 30 pieces of prints, after finishing, twist the edge of the paper a little, check whether the front and side gauges are positioned accurately (two overprints can be checked).

7. Pay attention to other work

(1) Ink supplementation, stirring and wetting fluid supplementation.

(2) Dirty removal. It is necessary to get rid of dirt because of the adsorbing of ink residue, paper powder, paper wool and other stolen goods on the printing plate or rubber cloth and reflected on the paper. Dirty removal operations should generally be stopped. Unless there is a device to remove dirt in operation. It is absolutely forbidden to use hands to remove dirt directly during operation.

(3) Cleaning rubber cloth, erasing and gluing operations. When ink, paper powder and powder spraying are accumulated on rubber cloth and affect the transfer of ink, it is necessary to stop the machine to clean rubber cloth, and pay attention to safety in operation. Safety should also be paid attention to in erasing and gluing operations.

(4) Pay attention to abnormal phenomena of printing press. Pay attention to the sound, heat, vibration, odor and so on when the machine is running. Check the ammeter frequently and pay attention to the abnormal situation of the printing press.

8. Attention should be paid to the confirmation of printing numbers

At the end of printing, it should be confirmed whether the printing number is in accordance with the production and construction orders. If there is a shortage to be reprinted, the production management personnel shall be notified and the reprinting shall be arranged in time.