Testing technology for printing quality of the hot

Detection technology of color box printing quality

at present, the detection technology of color box printing quality mainly includes density mode and chromaticity mode. Among them, density mode is a process control mode, which controls the key links of the printing production process according to the ink layer thickness. Chromaticity mode is a high-precision system control mode, which controls the color according to the visual measurement of chromaticity or spectroscopic spectrum, but it needs to comprehensively consider the printing materials, application environment and test purpose. In terms of implementation mode, it can adopt either the offline mode of manual sampling or the mode of automatic detection

1. Detection and control of printing quality of special materials

in color box packaging, the application and innovation of special materials and new materials is a trend, such as the development of cigarette packs from paper soft packs and cardboard hard packs to aluminum foil gold and silver cardboard hard packs. These composite or coating materials with high gloss surface have metallic luster and refractive surface. After printing exquisite patterns of various colors, they give people a feeling of high-end elegance, which can greatly enhance the value-added space of products, and are widely used in high-end color boxes

this kind of material with high gloss surface has strong metallic luster due to its flat surface coating. When irradiated by incident light, there will be strong specular reflection. Therefore, the color appearance of the object surface will change with the change of observation angle, resulting in the color in the printing production process is not easy to control, so that the printing factory is faced with the quality control problem of ensuring the consistency of ink color of the same batch of prints, and even different batches of prints, and its special inspection technical requirements

the color box printed with special materials has many spot colors and anti-counterfeiting processes in addition to four-color printing color pictures. Its detection contents include density, dot enlargement, registration and gloss. Due to the restriction of the surface gloss of special materials, in the density and point measurement, it is necessary to use the test instrument that uses d/0 to measure the optical geometric conditions. It is best to use the spectral spectrometer that divides the visible light 400 ~ 700nm band into 31 measurement intervals according to the spectral principle, measures the color spectral reflectance of the object, and then obtains the color CIELAB value and color difference, such as x-rite2 Prepare SP series of samples and measuring instruments. Thus, the accuracy and reliability of the measurement data of high gloss surface materials are guaranteed. Measuring instruments applied to the geometric condition of 0/45 of ordinary materials, such as x-rite900 series, cannot achieve consistent and accurate results

2. Detection and control of spot color printing quality

in the printing of color box packaging products, because spot color printing has a large area of field color blocks, the color is dazzling, and the shelf display effect is good; The color difference caused by dot overprint and dot deformation is reduced, and the color is stable and easy to identify. Therefore, a large number of spot color printing is its basic feature. At present, the measurement and control means of spot color in domestic color box printing enterprises are relatively backward, and most of them are still in the stage of allocating spot color ink based on the experience of workers. There are some shortcomings of spot color ink, such as inaccurate allocation cycle stress type (see Figure 2) [cycle stress type], long allocation time, and great subjective factors. Therefore, using color matching system is the best solution to the problem, and it is also the mainstream technology and development direction of international color box quality control and detection

spot color inking system is a system composed of computer, color matching software, spectrophotometer, analytical balance, ink homogenizer, ink spreading instrument and printing suitability instrument. The spot color ink matching system can store the parameters of the printing materials, inks and their color matching data of the color box printing enterprise in the system database through tests and experiments. The color matching software can carry out spectrophotometer measurement according to the spot color samples provided by the customer, automatically carry out color matching analysis and color matching operations with the computer, control the color matching conditions according to the CIELAB value, density value and △ e of the customer samples and color matching samples, and provide printing control parameters, Thus, the digitization of spot color ink matching can be realized. For example, the Swiss GretagMacbeth ink formulation system, which includes hardware spectrophotometer spectroeye and inkformula, can not only measure the printing point and density value, but also measure hue, saturation and brightness; Inkformula requires only a few concentration ladders to establish an accurate database. Color matching data can be used for offset printing, flexo printing, gravure printing and silk printing. It can provide the ranking of various ink formulas, which is almost a bad way for all the paper industry, such as the similarity of color phase, the value of same color spectrum, the unit price of spot color ink, the amount of ink, the thickness of ink layer, etc. Thus, the application of digital fundamentally breaks through the constraints of empirical color matching, and meets the development requirements of color box printing industry with higher quality, shorter cycle and lower cost

3. Color box printing quality detection and control technology

with the development of digital image acquisition technology and processing technology, the printing quality detection and control technology, which uses closed-circuit control system to detect and adjust the whole image of the print in real time, is constantly popularized and optimized. International mainstream printer manufacturers have taken the image detection system as the standard configuration, such as Roland pecom, Heidelberg cpc32, Bobst in Switzerland, proimage in the United States, DAC and tokimec in Japan

printing quality detection and control is mainly supplied to automotive and electronic market systems. High definition, high-resolution high-speed camera lens is used to capture images, and standard sample data is used as the standard to compare the differences and differences between the captured detection images and standard samples in real time (such as stains, ink spots, color differences and other errors generated in the printing process). Defects with the size of 0.10mm can be accurately found, even if such defects are only one gray level different from the standard image. This system can completely eliminate human errors, achieve high-speed, high-precision, 100% real-time detection of color box prints, and establish a unified and quantifiable inspection standard

in a word, the digitalization of the detection and control of color box printing quality is a new direction representing the future of color box printing production, and a technical guarantee for the integrated production of design, printing and post press processing. At present, although there are still some deficiencies or technical bottlenecks in the digitization of color box printing quality detection and control in China, the main difficulties are being eliminated and a bright future has been seen. Mastering the digital technology of quality control, establishing its own innovative process and realizing fine operation will become the key to the income distribution of the huge color box printing market, and also the fundamental problem of the sustainable development of color box printing enterprises