Automatic quality inspection in cigarette pack printing

In the world of cigarette pack printing, China's cigarette pack printing is first-class from design to quality. Regardless of whether the cigarette pack is suspected of over-packaging, the exquisite design, complex craftsmanship, and strict quality requirements have brought great challenges to the production of the printing house. As the materials used are becoming more and more high-end, the proportion of materials in the entire printing cost is also increasing. Reducing the generation of waste products and improving the quality control ability have become an important issue for cigarette packet printing factories.

From the external environment, due to the surplus of production capacity, the current market competition for cigarette packet printing is becoming increasingly fierce. Tobacco companies are increasingly restricting the delivery cycle, while at the same time, the pursuit of quality is getting higher and higher. Not only do they require high quality, but also expectable quality. While pursuing quality, they also care more about the quality control methods of printing plants. These continuously increasing requirements for quality control make the quality management cost of printing plants higher and higher, which weakens the profitability of printing plants.

Faced with these challenges faced by cigarette pack printing factories, AVT, headquartered in Israel, has successfully developed a complete set of automatic printing inspection solutions, which have been successfully implemented by more than 900 customers worldwide. The automatic printing inspection solution can help the printing plant meet the strict quality control requirements of its customers, effectively reduce costs and scrap rates, improve customer satisfaction, and prevent returns caused by quality factors. Many cigarette pack printing plants in North America, Europe and Asia have AVT systems in operation. Automatic detection can be used to print a variety of cigarette packs, such as hard shell cigarette packs, paper soft packs, and even filter prints.

Process control and quality assurance in printing

Tobacco companies have high requirements for quality. Once quality problems occur, a large number of returns will be caused. In order to reduce the risk, most printing plants have adopted the method of manual inspection of cigarette packets. However, manual full inspection has its limitations, and it does not mean that people will have visual fatigue problems. It is only a very short time to detect various problems that may occur in printing. This is already a very difficult task . Therefore, to truly guarantee quality and achieve zero defects, it is essential to adopt automatic inspection of print quality.

100% print quality guarantee is not the whole goal of automatic print quality detection. Even if all the printing defects have been detected, but at this time the waste has been generated and waste has been caused, which has not really played a role in reducing the cost and improving the efficiency of the printing house. Therefore, the important goal of automatic printing detection is to reduce or avoid the generation of waste products and reduce the rate of waste products. Of course, 100% of the generated waste products can be detected.

In the printing of cigarette packets, what are the main problems? Figure 1 is a statistical analysis of the problems often encountered in printing and their proportion. Through the analysis of these problems, you can find the problems in printing, such as color difference, registration, knife line and bar code, etc., accounting for more than 92% of printing. These problems are gradual, cumulative, and enlarged. We refer to these gradual cumulative problems as process problems in printing. Those random problems in printing, such as dirty dots and flying ink, are called random problems. Once process problems begin to occur, if measures are not taken in time, especially in high-speed printing systems such as gravure printing, it will quickly accumulate until a large amount of waste is produced. However, if the human eye can distinguish these problems, through the monitoring, analysis, and judgment of the automatic printing equipment, the alarm is given in time, and the operator takes measures in time, then the process problem may be completely eliminated before it becomes waste. For random problems in printing, there is no need to take measures, but there must be means to detect them to avoid outflow of waste products.

To solve the process control problem, the key is to be aware of the problem before the human eye can distinguish it. From a technical point of view, this goal can be achieved. To be able to detect very slight gradual changes in the printing process, it is required that the accuracy and sensitivity of the CCD device that records these changes be very high. The AVT system is implemented using three sets of array CCDs. It scans the entire printing width step by step through the rapid movement of the camera. Through the previous analysis of printing problems, once those process problems appear, they will not disappear automatically. Even if they are scanned step by step, they will never let go of the accumulated process problems. However, for the random problems, the current visible range of the array CCD is limited. If the entire printing width cannot be monitored 100%, it may be overlooked.

To avoid letting go of any defect that has been generated, and to ensure that 100% of the printing defects are detected, a linear CCD camera is used. The accuracy and sensitivity of the linear CCD is not as high as the array CCD, but it scans the entire printing width in real time through the linear scanning method, and will never let go of any waste products that have been generated.

For such high-quality printing as cigarette pack printing, a system combining printing process control and quality assurance is the best solution.

Integrated solution for process control and quality assurance

In response to the special needs of the cigarette packet printing industry, AVT has developed a product that combines process control and quality assurance-PrintVision Argus. After applying Argus, it can significantly reduce printing waste, avoid outflow of waste, and improve customer satisfaction. At the same time, thanks to better monitoring methods, the startup speed of the printing press can also be significantly increased, and the efficiency of the equipment is greatly improved.

Argus uses two cameras, each using an array CCD and a linear CCD. The array CCD camera can monitor various progressive printing process problems, such as color difference, registration, knife line, etc. at the first time. When a defect is detected, the system will automatically trigger the alarm system. At the same time, the detected defect will be framed on the screen with different color boxes, and can be easily compared with the standard image stored in the system setting. Each color represents a different type of defect. In this way, even if the operator is at a slightly longer distance, he can easily identify the type of defect and take timely measures.

Array CCD cameras are very sensitive to changes in contrast and require very high energy sources. This feature of it allows the array CCD to distinguish very small image changes. At the same time, the array CCD camera is also equipped with a very high-precision optical lens and an excellent zoom system, which can locally magnify the image and facilitate judgment, so it is the best technology for process control.

Another group of cameras using linear CCDs keep track of all the defects that have occurred in real time, whether they are cumulative process problems or randomly generated problems. Once the system detects defects, the system will mark these defects for subsequent processes Remove them to ensure that defective products do not flow into the hands of customers. Argus will also store all the detected defects in the system's built-in SQL database, and can generate quality reports for each job and each paper roll to facilitate internal quality management and communication with customers.

While not changing the hardware configuration, it is also possible to focus on some special applications by selecting different software modules.

Barcode Confirmation-Identify the barcode on the machine and classify the barcode quality according to international standards.

Precise color control One-to-one color change during the printing process is accurately controlled by â–³ E port â–³ L * a * b *

Reflective modules-support for highly reflective materials.

The selection of these special modules expands the application area and scope of application of the system.

At present, domestic cigarette pack printing plants are paying more and more attention to automatic quality detection, and the number of companies considering introducing automatic monitoring systems is also increasing. This will greatly help the stability and improvement of printing quality. When customers buy these systems, they must choose the quality testing program that suits them according to their own equipment and process flow, and take the right medicine.

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