Brief analysis of quality inspection technology of

2022-09-21
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Brief analysis of color printing quality inspection technology

release date: Source: China paper industry

in today's era, color printing has gradually become the mainstream printing technology in the current industry and is an indispensable part of ensuring the printing industry. Today, China's paper industry will start with color printing and tell you in detail about the quality inspection technology of printed products, which is located in Linyi City, Shandong Province

1 traditional nondestructive testing technology for printed matter

traditional nondestructive testing technology for printed matter includes subjective estimation method, relative density measurement method and saturation measurement method

subjective estimation method refers to comparing printed matter with standard printed matter immediately or relying on high-power magnifying glass to carry out human factors, and subjectively evaluate the quality of printed matter. Although this method is simple and convenient, it will be harmed by the working experience, psychological state, physiology and other factors of the actual operating staff, and its accuracy and reliability are weak

relative density measurement method and saturation measurement method rely on instruments and equipment to accurately measure the relative density and saturation of printed matter, and use relevant basic theories to analyze and solve the clearing and cleaning: data information, so as to comment on the quality of printed matter. These two methods can provide theoretical significance for objective evaluation of print quality, and get rid of the shortcomings of subjective estimation, such as asymmetry. Shanghai printing has been widely used in the packaging and printing industry. However, the commonly used instruments and equipment for relative density method and saturation method inspection only carry out inspection in areas up and down 10mm2, so it is necessary to add measurement and control technology, and it is impossible to get the specified information content from the packaging and printing interface in detail and immediately. Moreover, relevant studies have shown that the basic theories based on relative density method and saturation method have certain inaccuracies and limitations

the traditional nondestructive testing technology for printed matter also has a mutual disadvantage: they are all sampling inspection after packaging and printing. Once there is a quality problem of packaging and printing products, it is usually hundreds of pieces, and even will be covered with tofu skin. It can not deal with the deficiencies in the whole process of packaging and printing in time, which will lead to the extravagant waste of printing consumables and comprehensive working hours, and increase the product cost of the company

due to many deficiencies of traditional nondestructive testing technology, online printed matter nondestructive testing technology is emerging at the right time

2 technical nature of print monitoring

1) technical advantages of print monitoring

print monitoring is a suitable automatic inspection method for high-speed packaging and printing, which is closely combined with the technical nature of image processing and the basic principles of packaging and printing. Its advantages are embodied in the following two levels:

first, the monitoring is more accurate, and it can detect extremely minor defects. For example, we focus on the essence of the inspection of a printed matter. Only when the adjacent color of the printed matter is obvious, people's eyes can detect defects above 0.2mm, and the inspection quality can't be kept stable. In the same color tone, Shanghai printing factory, especially in the light color printing materials, can't detect the defects by human eyes. Monitoring can easily detect 0 Millimeter size, and only one gray level difference is needed

second, monitoring improves productivity. The quality evaluation of the monitoring system software is independent of the subjective discrimination of the operator who makes a left turn into jing10 road and drives 20 meters along jing10 road. The adjustment in the whole process of operation is faster and easier. Even one process completes the adjustment, and the inspection speed is further improved. In addition, in case of quality defects, the operator can immediately deal with the problems in the work according to the immediate report on the spot, so as to reduce the unqualified rate. The management personnel can also track the processing process according to the data analysis report of the inspection results, so as to improve the management efficiency

2) basic principle of print monitoring technology

basic principle of monitoring system software: the system software takes a camera lens according to CCD, collects flawless prints as standard images, then collects the images to be inspected in the packaging and printing production line, and transmits each frame of the images to be inspected to the spot to carry out data analysis with the standard images, so as to find the images with quality problems, Then the quality problem of the printed matter matched with the frame image is found; Finally, the relative packaging and printing components are automatically adjusted to complete the online manipulation of the quality of printed articles. When implementing the measures, the printed matter monitoring is generally divided into two steps: the first is to prepare in advance for inspection, that is, according to the image collection of qualified products, get the standard printed matter image, also known as the template, followed by the specific inspection. The image of the printed matter to be inspected will be compared with the standard template, Then, according to the comparison results, it is clear whether the defect exists and the defect part, and record the defect information content

the defect key of the printed matter includes appearance defect and tone defect. The defect key refers to the defect, dirty things, stains, knife threads, etc. it is mainly shown in the image. For the difference between the gray level of the defect part of the defect image and the standard image, compare the gray level of the defect image with the standard image, Distinguish whether the error has already exceeded the preset threshold range, and you can distinguish whether the image has appearance defects. Color 3 - the elastic recovery depth after removing the main experimental force F1; The key disadvantage is that there are errors in the color tone between the print to be inspected and the standard print. The saturation value ciel*a*b* of the print image can be obtained by using the color space transformation solid model, and the color deviation of the print can be evaluated by color deviation

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