Fully automatic print quality inspection system that is online detection system

The automatic print quality inspection system is a vision-based online inspection system. It scans the print image on-line via the camera and sends it to the memory for processing by the image processing software. The result is compared with the standard data to find the difference between the two and analyze it. Caused by the error, and then re-design parameters to better improve the quality of printing. The emergence of this technology has greatly reduced the human intervention in the quality control of the printed matter, and can greatly increase the production efficiency of the printing machinery, thereby reducing the requirements for the skills of the operators, and providing a feasible solution for realizing the automation and intelligence of printing machinery. The implementation plan has broad development and application prospects. The following describes the online print quality inspection in detail.

First, the basic principle

On-line print quality line detection technology uses CCD (Charge Coupled Device) devices to continuously take pictures of printed products on a print production line. Each captured image is transmitted to on-site computers, and image processing software is used to image information. Analyze and process, find the image with quality problem, give the quality problem of the print product corresponding to the image, and then feedback the information to the operator through the transmission line or directly feedback to the printer for adjustment.

First of all, in the preparatory stage of quality inspection of printed products, a certain number of qualified products are sampled to obtain standard images (typically more than 60 samples) and then made into templates. The sampling process should pay attention to the scanning resolution, the spatial resolution of the image, the correction of the spatial coordinates of the image, the hue of the color image, the speed of the CCD, the illumination conditions, and the mechanical vibration, etc., on the sampled image.

Followed by the actual detection, the CCD camera on the production line is used to continuously photograph the prints, and then the resulting image is converted into digital information and transmitted to the central processor of the printing press. The obtained print image information is compared with the obtained template, according to The result of template matching determines whether there is feedback information to the CPU or printer operator of the printing press. If a failure occurs, the matching failure information is fed back to the printer for adjustment or the printing operator handles it.

Second, on-line printing quality inspection technology manifestations

On-line printed product inspection system can be divided into on-line inspection system and off-line inspection system according to the carrier it installs. According to the application form, it can be divided into sampling inspection system and "100%" detection system.

1. Differences between on-line detection systems and off-line detection systems

The on-line inspection system is installed on printing equipment such as offset printing presses, gravure printing machines, flexographic printing presses, and code printing machines to detect the print quality in real time and can be used for sheet-fed and web-printed materials. Off-line inspection system is usually installed on the inspection product or rewinding machine, which can realize the position recording and marking function of the online detection system. At the same time, the inspection product also has a sub-warehouse function, and the good and bad products are automatically assigned to different according to the detection result. In the warehouse. The visual inspection part of the on-line inspection system and off-line inspection system is basically the same in function, and the main difference lies in the processing method of defective products. When a defect is found, the online inspection system usually records the location of the defect (length: web, number of sheets: single sheet), or uses a printer, labeler, marking machine to mark the edge of the paper, number Check the record error number or the number of adjacent sheets.

2. Differences between the sampling inspection system and the "100%" inspection system

The technology used by the sampling inspection system is similar to the 100% drum observation system. The sampling inspection system adds extra software to the drum observation system, which fixes a video camera on a beam with an engine and is equipped with a flash device that works intermittently. The 100% roller observation system employs a completely different approach. Permanently install several line scan cameras across the entire length of the drum. This means that 100% print inspection is not meant as a control system. Can detect defects within a specified area. In brief, it means that the printed paper roll is continuously detected with a specific sensitivity to the entire width.

Third, the main function of online print inspection system

1, automatically detect the quality of the production process

2. Correct mistakes before they occur

3, to ensure that the wrong prints are not issued to customers (quality assurance)

Whether it is installed on printing equipment, composite equipment, or subsequent processing equipment, automatic inspection equipment can help printers reduce time and save costs while improving the quality of printed products, avoiding customer complaints and rejecting the possibility of receiving goods.

The current automated inspection equipment supports all printing technologies, substrates, and workflows. The inspection system can be equipped with an array camera (such as AVT's Jupitor system), a 100% LCCD camera (such as AVT's Apollo quality inspection equipment), or a composite camera of both (such as AVT's Argus). Meet different customers' different needs and work processes. In the printing process, automatic inspection equipment can help printers to reduce waste by 50%, and the printing press can be printed at a speed of at least 30%, resulting in considerable economic value.

Fourth, online print inspection system performance indicators

The printing product monitoring system adopts advanced image vision detection technology to collect the surface image of the printed matter through the camera, and transmits the image data to the image processing system through a dedicated image acquisition card. The image processing system performs preprocessing, color segmentation, and matching on each image. Positioning and other operations are compared with standard template images. If inconsistent areas are found and the set tolerances are exceeded, waste product alarm information and reject control signals are output. In most cases, missed prints, missing prints, flying inks, stencils, blemishes, blemishes, flying insects, inks that are too light, inks that are too dark, characters that are partially or completely missed, overprinting, wrinkling, Mechanical defects such as mechanical damage, knife wire, and stripe; for color print detection systems, color distortion (color aberration), color unevenness, etc. can also be detected.

V. Application in the printing and packaging industry

The application of visual quality inspection in the printing and packaging industry can be prepress, during printing and after printing, but most of the current applications focus on post-print quality inspection. There are tens of thousands of printing companies in China. There are few real test systems. In addition to special industries such as banknote printing and ticketing, they are mainly used for packaging, label printing, commercial printing, and final reprint inspection.

1, bill printing

Bills have become an indispensable part of life. Their print quality requirements are getting higher and higher. Not only is the picture quality required to be accurate, but also variable information such as numbers, Chinese and English characters, bar codes, and patterns contained in labels and notes is extremely important. Therefore, it must be monitored in real time during the printing process. At present, China's bill printing industry is in hot water, and the introduction of automatic testing equipment has further enhanced the market's competitive advantage.

2, cigarette package printing

Different from other product packaging, tobacco packaging has its own characteristics. The technology and process required for cigarette pack printing are second only to the printing of banknotes and securities, and it is currently one of the most demanding packaging products. At present, domestic cigarette pack printing plants are paying more and more attention to automatic quality inspection. Companies considering the introduction of automatic monitoring systems are also increasing. This will greatly help the stability and improvement of the printing quality of enterprises.

3, label printing

At present, the level of quality monitoring and inspection in China's label companies is uneven, and there is a clear gap between high-end companies and small and medium-sized enterprises. With the rise of domestic raw material prices, severe economic situation, labor and operating costs are too high, printing companies Faced with increasingly severe situations, some companies have realized the importance of controlling costs and improving quality, and have turned to automated printing inspection systems. In the near future, automated printing inspection systems will dominate the development of the label printing industry.