The most popular view on printing process control

2022-08-02
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As we all know, the purpose of color management is to automatically and uniformly adjust and manage colors in the production system by using the method of combining software and hardware, so as to ensure the consistency of colors in the whole process of input, display and output, and finally realize the faithful reproduction of colors (i.e., what you see is what you get). So, how to implement color management quickly and efficiently? The author believes that establishing a measurable and repeatable process control system, standardizing the control of printing raw materials, related equipment and environment, and optimizing the data flow and information flow in the printing production process can achieve unexpected results

I. Introduction to color management

1 Definition of color management color management is an application technology to correctly interpret and process color information. In addition to inheriting the advantages of light, durable and cheap traditional wood packaging materials, wood packaging materials that have been deeply processed by people are recognized as the most effective scheme to achieve faithful reproduction of color and repeatedly obtain stable color. In the whole process of copying the color graphic information, the color management system ensures the consistency of the color in the process of converting from one device's color space to another device's color space on the premise of minimum color distortion

2. Workflow of color management

the workflow of color management can be divided into four C: calibration, characterization, conversion and check

① calibration. This is the basic condition for good color management. It refers to adjusting the standard state of each equipment such as display, scanner, digital proofing machine and printing machine to ensure that it meets or is accurate to the specifications of the manufacturer, and maintain a certain stability to ensure that the color of its performance meets or is close to the normal standards. Calibration is the basis and starting point of color management. Its purpose is to calibrate the equipment and make it run stably. The stability of the equipment is the basic condition for color management. Therefore, calibration is very important in the process of color management

② characterization. It refers to inputting or outputting standard color codes on the calibrated equipment, then measuring these color codes, determining the color performance characteristics of the equipment according to the obtained data, and establishing the color characteristic file (iccprofile). The purpose is to establish the color expression range of equipment or materials, and to record their characteristics mathematically for color conversion. Characterization is not only an important part of color management, but also a prerequisite for color management

③ conversion. It refers to converting the color of an image or other object from the color space of one device to the color space of another device, in order to obtain basically consistent colors visually

④ inspection. That is, the inspection and evaluation of color matching between various equipment

II. Printing process control based on color management

1 Control the stability of printing materials

the stability of materials is the prerequisite for obtaining high-quality printed materials. In the process of daily production, it is of great significance to strictly control the stability of printing plates, developing fluids, fountain fluids, paper and ink. Ensuring stable printing materials is the prerequisite for implementing color management. The quality of the original directly affects and determines the quality of the printing plate. In order to make a high-quality printing plate (referring to the blockage of detours), we must first have a high-quality original as a guarantee. The configuration of developer and fountain solution shall be carried out in strict accordance with relevant specifications and requirements, and their status shall be regularly monitored. See Table 1 for the supervision contents. Paper and ink directly affect the printing quality. Therefore, it is particularly important to supervise the stability of paper and ink. Paper and ink are supervised according to iso12647 2 and iso2846 1 respectively. See Table 2 and table 3

2. Control the stability of printing equipment

a stable state of the printing machine is a powerful guarantee for obtaining high-quality and stable printing materials. The printing machine needs regular maintenance to ensure that the machine is always in a stable working state to ensure the uniformity and repeatability of printing, so as to ensure the quality of printed matter

for color management, ctp2 and buffer oil should be kept clean and the stability of plate making machine and printing machine is very important. CTP plate making machine can be calibrated by outputting plates, analyzing and adjusting the area ratio of output points to obtain linearized output results. The printing press can be evaluated and corrected by means of GATF or G7 test methods, so as to ensure the stability of the printing press

3. Control the stability of printing environment

a stable production environment plays an important role in ensuring the stability of printing quality. The printing workshop needs to strictly control the temperature and humidity (as shown in Table 4). The change of temperature and humidity in the workshop, usually used as a soft tissue regeneration scaffold or drug transport carrier, will lead to paper deformation, resulting in inaccurate overprint, affecting ink balance and ink drying, and ultimately affect the printing quality

4. Control the stability of printing quality

stable printing quality can be achieved by ensuring stable point transfer and stable ink volume, stable point transfer can be achieved by ensuring stable printing conditions, and stable ink volume can be controlled by controlling ground density or chromaticity, such as the process control method of G7

g7 is a new printing quality control method based on CTP computer direct plate making and spectrophotometric measurement, which measures and controls the neutral gray balance on the printing sheet through a spectrophotometer, focuses on the control of highlight contrast HC (highlightcontrast), highlight range HR (highlightrange) and shadow contrast SC (shadowcontrast), and matches the image visual effect with neutral gray printing density curve NPDC (neutralprintdensitycurve)

g7 test is carried out in two times. During the first printing, cmykrgb is controlled according to the ISO standard ink color standard in Table 3. After meeting the requirements, 1000 pieces are printed and sealed in the same state. After the samples are dried, appropriate samples are taken, and the P2P standard data on the samples are measured by eyeonepro or eyeoneisis, Then draw the neutral gray printing density curve NPDC manually (using g7fangraph chart, as shown in Figure 1) or with the help of idealinktmcurve software, and calculate and adjust the output compensation value to obtain a new rip curve

the second time is for printing to call the characteristic test version of rip curve output obtained after the first printing. First, cmykrgb is controlled to meet the relevant ISO ink color standards (see Table 3), and then the gray balance is controlled to make HC, HR and SC meet the requirements of G7 (see table 5). After the control parameters of the printed samples meet the requirements and the printing quality is stable, the samples meeting the requirements are taken to measure the data of it8.7/4 digital standard. According to the measurement results of it8.7/4, a characteristic file (iccprofile) reflecting the actual situation of the printing machine can be made to fully prepare for color management

III. conclusion

the implementation of color management should be based on stable production conditions, that is, printing materials, machine status and environment should be kept stable. Establishing an optimized process control system to ensure stable production conditions is not only conducive to the implementation of color management, but also can ensure that color management plays a maximum role and promote the continuous improvement of printing quality

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