Standardized operation of printing production process

In today's increasingly fierce competition in the Chinese printing market, the competition of enterprises has been introduced from simple equipment, improving the company's production capacity, and developed to the use of advanced technology and management methods to enhance the comprehensive competitiveness of printing companies through comprehensive training of personnel. To improve the staff's theory and operation skills, everyone has reached consensus.

The quality control of printing has gone through three stages of development. First, the quality of human experience determines quality. The quality of printing is determined mainly by visual inspection and subjective experience. The stability of printing quality is poor and the volatility is great. Second, color control: utilization density, dot gain rate The quality control of ash balance is the post-event control of sub-processes. It is closed quality control and has become increasingly unsuited to the modern, open, digital, and full-flow working environment. The third is color management: using colorimetry, ICC theory, open, coherent, automated, digital pre-administration of the entire printing process, fundamentally solve the complex and variegated problems of color.

To achieve the color management of the entire printing company, we must first achieve the standardization of the entire printing production process; and standardization and dataization are complementary.

First, the standardization of the output section of the phototypewriter

Before the CTP process has been widely used, most of the domestic laser photodiodes still output color separation films instead of printing plates. In this process, the hardware devices involved are the imagesetter and the punching machine. The standardized control of the two is complementary and should be considered as a whole.

1. Color quality requirements

(1) The fog of the substrate is as small as possible. General imported films, such as Agfa, Kodak, Fujifilm, Konica, etc., can guarantee the gray of the substrate under normal exposure and development conditions. Haze.
(2) The density in the field (without film-based fog) is as large as possible when the 50% dot is restored to a good level. No lower than a certain value for commercial printing. The fact that the density of the field is too low will cause visible light in the graphic section of the positive-printing PS plate, resulting in a significant decrease in the printing plate's resistance to printing forces.
(3) The value of the transmission density at the center of the transparent screen shall not be higher than the density value of the transparent film (film base plus fog). 50 times more magnifying glass can be used to observe the transparent area within the grid, there can be no edge blur, noise phenomenon.
(4) In the case of a stable environment, the difference between the lengths of the diagonal lines of a set of color separation films shall not exceed 0.02%. In general, the registration accuracy can reach 0.05mm for imported inner drum and outer drum photosetters.
(5) The layout is clean and free of smears, no trachoma, and there are no obvious cracks in the dots or text.

2. Photographic process control

(1) Environmental Control. The temperature and humidity of the photo ventilator room should be strictly controlled to avoid affecting the registration accuracy of the color separation film due to temperature and humidity changes. Too low or too high temperature may affect the normal operation of the image and mechanical parts of the imagesetter. If the humidity is too low, static electricity is easily generated, which may not only damage the circuit, cause interference, but also cause electrostatic exposure of the film. Temperature and relative humidity should be controlled within a certain range.
(2) The dustproof and cleanliness of the machine room is also very important. Dust will accumulate on the optical path of the image-setter, affect the intensity of exposure, produce stray light, and affect the clarity of the image. In particular, the inner drum type and winch type photosetters which are widely used nowadays generally employ air bearing rotary motors, and the dust is too large to greatly reduce its service life.
(3) The electricity environment is also a factor that cannot be ignored. A good grounding can avoid the accumulation of static electricity and reduce the interference, otherwise it will easily cause the electrostatic exposure of the film and even burn out the circuit board when the voltage of zero or zero ground voltage is unstable. Therefore, it should ensure stable power supply and good grounding. In general, it is best to use a regulated power supply or UPS with sufficient power. It is best to make a ground wire for the illumination room alone. The remote resistance should not exceed 4Ω, and the zero-ground voltage should not exceed 5V. In fact, many photo-composing machine manufacturers have very strict requirements on the power environment so as to minimize the impact of surges and surges in the power grid.

3. Job records

In the form of work slips, it is transmitted between processes, and detailed records of all technical parameters, necessary environmental parameters, handling personnel, customer requirements and other information in the process are used to facilitate the cooperation of the previous and following processes, and can also be used as a survey when quality problems occur. in accordance with. When making a record sheet, it should be set according to the type of the existing output equipment, business job, and its own process. Commonly used record items are: film brand, batch, file size, page number, whether or not to make up the word, color separation film on-site density Dmax.

4. Linearization of film

Linearization is a very important job in the photocopying process. Its purpose is to ensure that the separation film can achieve the necessary on-site density, and that different percentages of dots can be accurately recorded on the film. Controlling the linearization of the color separation film requires that the imagesetter and the punching machine cooperate in controlling. First, control the concentration, temperature, automatic replenishment amount, and time of developer and fixer of the punching machine so that these factors are as stable as possible. Afterwards, the appropriate exposure intensity was determined according to the self-check sample of the imagesetter to achieve a certain reduction of the field density and 50% dot. Finally, the linearization of the percentage segments of each dot is accomplished by RIP at this exposure intensity. In the daily work, the density and linearity of the film should be checked frequently. Once it is found beyond the normal range, the parameters should be adjusted in time to redo the linearization.

In addition, the punching equipment must be cleaned regularly.

Second, the standardization of CTP plate making

With the advancement of technology, the CTP direct plate making process has been gradually applied in the domestic commercial printing market. Compared with the traditional printing process, CTP's direct plate making process has unique advantages. The traditional printing process goes from the electronic file to the printing plate through the photo output and the plate making. In the process link, there are many human factors in the two process links. The quality of the printing plate is directly related to the operator's level and equipment. The CTP direct plate making process, in terms of its own production process, directly outputs the electronic file to the plate. At the same time, the influence of human factors is relatively small and it is easier to ensure the quality requirements of the printing plate.

The traditional printing technology has a long history. Each process link is relatively mature and well-known and recognized by all. The CTP direct plate making process is a new technology compared to the traditional printing process. The characteristics of the plate material are for the user. Is not very familiar with, its printability and the traditional plate after all, there are differences, so the current process in the country relative to the printing industry is not very mature, the new technology is not yet in place. Some manufacturers lack understanding of this, as long as the prepress and printing equipment can achieve the same purpose of printing quality and stability or color reproduction, so some companies did not achieve the desired purpose (improvement and stability) after the introduction of CTP direct plate making process Printing quality); some manufacturers after the introduction of the printed matter quality is not even as good as the quality of traditional prints, but also because of the CTP plate and the traditional printing plate printability have a greater difference but do not want to use, appear after the purchase of CTP unused situation.

Therefore, it is necessary to improve and standardize the use of the CTP direct plate making process in each printing company. The environmental conditions and equipment conditions of printing companies are different, the quality requirements and the number of equipment are not the same, and the entire color printing process is standardized and improved according to the company's environment, equipment and conditions.

CTP direct plate making process realizes the digitized work flow. The digitization of the process requires the standardization and dataization of the process. This is also the reason why the CTP direct plate making process can be relatively stable compared to the traditional printing process plate making quality. Therefore, the CTP direct plate making apparatus The specification of use is indispensable. The specification of the CTP direct plate making equipment includes the determination of the output parameters, the correct proportioning of the stencil, the value setting of the replenishing liquid, the replacement cycle of the liquid, and the standard cleaning procedure of the processor. and many more.

1. Specific operation overview

(1) According to the situation of the printing equipment, a test file is designed to conduct the corresponding printing process test, and relevant data is extracted; the process parameters of the CTP plate making are tested and adjusted, and the outlets of the CTP output process are correspondingly standardized and modified so that The CTP output meets the requirements of our factory's printing process.
(2) Perfecting the CTP printing process, after correspondingly regulating the CTP output process, performing corresponding tests on the modified media, extracting relevant data, and applying it to the printing process; correspondingly, the network point of the CTP process is restored. The specification limits the enlargement of dots and printing density, and controls the printing process so that the quality of the printed matter of the CTP process is relatively stable and superior to that of the traditional plate making process.
(3) Debug printing factory digital proofing system, make the proofing effect approach the printing effect of CTP.
(4) Operators have relevant skills:

1CTP plate-making personnel should master how to control plate quality and quality inspection according to the printing process requirements of the factory;
2 The printing staff establish perceptual cognition of printing quality control and understand the control of printing data;
3 The printers have mastered how to control the various printing jobs according to the requirements of the factory so that the quality of the printing job can meet the requirements;
4 to master the use of the plate density meter and the correct debugging method of the CTP plate Calibration;
5 master the correct debugging method of printing Calibration;
6 Master the correct proportion of the liquid version, the value of the refill solution, and the replacement period of the liquid;
7 Master the standard cleaning procedure of the plate processor;
8 Master the standardized and data-based workflow that guarantees the quality of printing plates.

Third, the standardization of printing

Printing is the last important part of the entire process and must be strictly controlled according to the specifications to ensure the final product quality.

1. Print shop work environment

Temperature: 18°C～28°C (upper and lower limits correspond to summer and winter respectively), and the temperature difference within the range of the whole printing press is less than 2°C (this item is also effective for humidity); changes in temperature will affect the accuracy of registration.
Humidity: 40% to 80%, changes in humidity will cause the tape to break;
Look at the light color temperature of the sample stage: D65;

The printed version or the CTP version of the solarization system is inspected for layout, number of sets, and version, and is mainly compared with the sample and sample proofs;

Check the ink and fountain solution while loading the plate. If it is the first edition of the day, the skin must be scooped and beaten; if it is not for the continuous supply of ink, the ink must be filled in the ink tank; the use of the fountain solution should usually be determined based on the actual process conditions. Matching, etc., each shift special person to check its concentration, strictly controlled within the standard of measurement.

2. The basis of registration in printing

Register line: error is less than 0.01mm;
Color image: no moire.

3. The basis of printing in printing

Gray balance, the degree of color cast of the color image (compared with the proofs), black ink is too heavy or too thin.

4. Four-color printing density data

The pressure between the blanket cylinder, plate cylinder, ink roller, water roller, etc. should be checked monthly and adjusted as necessary to conform to the factory set range. The blanket is a fragile item and requires replacement after a certain number of impressions. The smoothness of the surface of the blanket should always be checked during work.

One of the basic preconditions for quality control in the printing process is the stability of the printing. Track the fluctuations in the printing density and dot gain of four-color inks in a batch of jobs or in live jobs for consecutive days. Stable within a reasonable range of data. As long as we can control the printing density and dot gain of four-color inks, we can think that the stability of printing links has been controlled.

There are many factors that affect the stability of printing. The printing environment is an important factor. The range of temperature and humidity changes in the workshop is one of them. Excessive range of change has a great influence on the stability of the printing, such as the swelling of the paper, the viscosity and thixotropy of the ink, etc. Both affect the transfer characteristics of the ink.

The factors that we can control related to the printing press are the ink and fountain solution. The fountain solution mainly refers to the concentration ratio and stability of the drug, and the uniformity and controllability of the ink along the ink roller is very important. .
The corresponding detection equipment can be used to control the ink balance of the printing press, so that the density of various colors and dot gain can be stabilized in a proper range. Based on this, the corresponding data can be measured and used for scanner calibration or digital proofing. After digital proofing is adjusted, it is possible to pursue samples in the printing sector.

Reprinted from: Ke Yin Network