The 29 common knowledge of printing technology you should know is as follows:
1. What is the meaning of quality? What is the meaning of print quality?
Quality, also known as quality, reflects the sum of the features or characteristics of a product or service that meet the ability to meet an explicit or implicit need.
Print quality refers to the quality of printing technology in the process of copying printed matter, including absolute quality and average quality.
2. What are the main requirements for the quality of color prints?
The overprint is accurate, the ink color is uniform and bright, the layer is rich, the dots are smooth and full, the field is plain, the text is clear, there is no broken pen, no obvious streaks, no greasy rancidity, no paper hair, no ink skin, etc. Restored to the authenticity of the original.
3. What is the difference between offset printing and other printing?
â‘ Using the basic principle of incompatibility of oil and water to complete printing:
â‘¡The blank part and the graphic part are basically on the same printing plate surface, and selectively absorb water and ink;
â‘¢The imprint is transferred through the intermediate (rubber roller):
â‘£The tone is presented by the dot size.
4. What is the process principle of offset printing?
Offset printing uses the basic principle that water and oil are incompatible to achieve the printing effect. When printing, add water first, so that the blank part of the layout absorbs water, while the image part repels water. When inking, the blank part repels ink while the image part absorbs ink.
5. What is the ph value in the wetting fluid?
The ph value represents the content value (concentration) of the acid and alkali contained in the wetting liquid, and the negative logarithmic value of the hydrogen ion concentration indicates the acidity and alkalinity of the solution. ph = 7 is neutral solution, ph> 7 is alkaline solution, ph <7 is acid solution.
6. What should be the pH range of the wetting fluid in production?
For the pH value of the ps version of the wetting fluid, it is generally appropriate to control it between 5 and 6.
7. Improper control of pH in the wetting fluid, how does it affect product quality?
Strong acidity: It is easy to cause the printing plate pattern and dot to become smaller, reducing the printing plate durability, the ink is easy to emulsify, resulting in quality defects such as not easy to dry the print, and sticky dirt on the back of the product.
Weak acidity: the printing plate dots are easy to paste, merge, and get dirty, causing paste plates and dirty.
8. What are the characteristics of alcohol wetting?
â‘ Good wetting performance, good spreading performance on the layout;
â‘¡Because alcohol has a certain volatility, after the water on the layout is transferred to the blanket, the water has a certain degree of volatility, so the paper's water absorption will be reduced;
â‘¢ When the alcohol volatilizes, it can take away a lot of heat, so that the temperature of the plate surface is reduced, and the flow performance of the ink is guaranteed.
9. What is the role of wetting fluid in production?
â‘ Make the blank part not dirty and greasy (not fat-sensitive);
â‘¡The hydrophilic property is maintained by the hydrophilic colloid and organic acid;
â‘¢With the surface active substance and surfactant, the blank part of the layout needs less water, so that the blank part can be protected, which is conducive to the balance of water and ink;
â‘£The pH value of the wetting solution is stabilized by the buffer solution (same ion effect).
10. When printing, what is the effect of the moisture content of the layout and product quality?
In the printing operation, the water content of the printing plate is difficult to control; when the water content is too large, the product ink color is too light, the ink color is matt, the color color is not bright, the plate is easy to pattern, the ink is easy to emulsify, and the paper will be stretched and deformed, causing overprint It is not allowed to wait for quality defects; while the moisture is too small, it is easy to make the layout dirty or greasy, and the dots appear to be connected and pasted and other quality defects.
11. What is the meaning of "water-ink balance" required in daily production?
Water-ink balance means that under certain conditions, the supply of dampening fluid is adjusted so that the amount of ink emulsification is controlled to a minimum, and the minimum amount of water is used to compete with the amount of ink that the plate image should have.
12. How to achieve ink-ink balance in work?
â‘ The printing plate should have good hydrophilicity and lipophilicity, and have a good stable foundation and adsorption force.
â‘¡ There must be a good thickness uniform sand hole mesh, a plate with good water storage function, and strong mechanical wear resistance.
â‘¢The workshop has a good production environment, and the temperature and humidity of the workshop are relatively stable.
â‘£ The machine is running evenly and normally, and can not be fast or slow.
⑤ Have good paper and ink.
â‘¥ The thickness of the ink layer in the graphic part of the printing plate is 2 ~ 3um, and the thickness of the water film in the blank part is 0.5-1um. The amount of wetting fluid in the ink is 15% ~ 26%, the maximum is not more than 30%.
13. What is regulation?
The lines prefabricated in various shapes for plate making, printing, cutting and binding are called gauge lines, also called specification lines.
14. What are the commonly used rules?
Generally, there are corner lines, trailing lines for proofing specifications, cross lines for overprinting, folding and cutting lines for binding, burrs and net cutting lines for cutting, etc.
15. What are the main factors that cause overprinting?
There are four main factors that cause overprinting:
â‘ Improper process operation causes inaccurate overprinting (generally refers to improper handover time and position during machine debugging);
â‘¡The overprint is not accurate due to the wear of mechanical equipment (general wear parts such as bearings, gears, bushings and other related parts, etc.):
â‘¢Material reasons (related to the texture of the paper and silk locks);
â‘£ Imposition is not allowed (the patch of the film before printing is not correct);
⑤ Plate deformation (due to excessive pulling force during plate installation, the plate is deformed);
â‘¥ Other aspects, such as sudden weather changes, the temperature and humidity of the production environment change significantly, causing serious deformation of the paper, causing overprinting.
16. What is the difference between four-color machine overprinting and single and two-color machine printing overprinting?
The single-color and double-color machine overprint is not correct because the back and front colors have circumferential and axial overprint; the improper overprint of the four-color machine means that the four colors are printed at one time and the overprint is accurate, but the front and back printed sheets are The line positions are not in the same position, and the specifications of the printed sheets are not uniform (circumferential and axial), that is, the size of the white border at the bite of the graphic or the side rule is different, and it is generally not easy to find.
17. As far as j2108 or j2205 offset presses are concerned, how many handovers are there from the paper feed frame to the front gauge and then to the finishing table?
â‘ Handover when the paper arrives at the pre-regulation;
â‘¡Handover of front and side regulations;
â‘¢Handover of side gauge and paper feeding teeth;
â‘£Handover of paper feeding and embossed teeth;
⑤ The hand-over between embossed teeth and paper-cut teeth.
18. What are the common forms of prepositioning?
There are two types of pre-positioning for upward swing and pre-positioning for downward swing.
19. There are several forms of common paper delivery devices?
There are two forms of upper swing paper delivery device and lower swing paper delivery device.
20. What are the positioning characteristics before the upper swing?
The swing-up front gauge block only enters the continuation positioning position after all the drag of the previous sheet leaves the paper feeder, and the working positioning of the next sheet depends on the diameter of the roller and the size of the paper.
twenty one. What are the positioning characteristics before the down swing?
The front gauge does not need to wait for the edge of the previous sheet to leave the paperboard to enter the positioning position, so that the next sheet can be positioned for work. Therefore, under the same conditions, the positioning time is long before the down swing type is adopted, and the positioning stability is good.
twenty two. What are the characteristics of the upper swing paper delivery device?
â‘ The trajectory of movement is similar to the closed curve of a drop of water, and is completed by an eccentric device;
â‘¡ When returning the paper delivery device, it can avoid the surface of the roller.
twenty three. What are the characteristics of the lower swing paper delivery device?
â‘ Swing at the center, the movement path is in the form of a circular arc:
â‘¡ There is one more paper receiving roller than the upper swing type paper transfer, adopting an eccentric structure to avoid the paper transfer device from colliding with the roller when returning.
twenty four. What are the movement characteristics of paper-hands in daily work?
â‘ Paper delivery teeth are in a static or relatively static state when receiving paper at the front rule;
â‘¡The speed of paper delivery is steady acceleration (range from zero to one linear speed on the surface of the drum);
â‘¢Paper delivery row and roller are at the same cutting point for paper handover, and the movement direction of the two is opposite, but the surface speed is equal, that is, the handover is completed in a relatively static state.
25. What are the movement characteristics of the high-speed paper separation mechanism?
â‘ The structure of one eccentric two cams is adopted to reduce the force on the separation shaft and the stability is good;
â‘¡Adopt pneumatic control structure, use internal air pressure and change song to control the falling and lifting of the suction nozzle, so that the suction paper movement is correct;
â‘¢The guide slot structure is used to complete the movement of the paper feeding nozzle, which can control the paper skew;
â‘£Adopt rotary gas distribution valve, valve core and valve seat with high precision, at the same time adopt lap structure, which is convenient for disassembly and assembly of valve core shaft and paper separation shaft.
26. What are the requirements for the simultaneous transfer of paper transfer teeth and embossed teeth?
â‘ The time to complete the teeth transfer must be guaranteed:
â‘¡ The edge of the paper is not broken when the teeth are handed over;
⑨ The effect of handing over teeth should ensure that the overprint is accurate.
27. What is printing pressure?
The positive pressure when transferring the ink on the printing plate to the substrate is called printing pressure.
28. What are the different forms of printing pressure?
â‘ surface pressure representation; â‘¡ line pressure representation; â‘¢ compression amount representation; â‘£ contact area width representation.
29. What is the ideal pressure?
The pressure that uses the minimum amount of force to obtain the dot size that meets the requirements of the original is the ideal pressure.
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