In the past few years, the detection system has developed rapidly in the processing industry. Today, 100% automatic fault detection technology has been implemented. Today, you can hear the word "fault detection" in almost all industries. Used in the printing and packaging industry, it can help us find all the defects on printed products and can be applied to different printing methods.
In terms of printing quality inspection, countries such as Europe, America and Japan have made great progress. As early as the 1970s, there have been vendors actively working with image processing systems to digitize visual information, achieve "seeing" and "cognition" of print quality through computers, and conduct high-speed, high-precision printing on printed materials. 100% real-time detection completely eliminates human error and establishes a uniform and quantifiable detection standard. At present, BOBST (Switzerland), PROIMAGE (USA), DAC (Japan), and TOKIMEC (Japan) can provide full automatic print quality inspection equipment.
Type
At present, there are two basic types of detection systems for automatic printing fault detection technology, namely 100% sampling type and 100% full type.
A 100% sampling system refers to a site that is repeatedly selected for printing within a period of time. The site is monitored 100%. The repeat time can range from a few seconds to several minutes. The 100% comprehensive system monitors 100% of each part of the product processed on the press. The two systems use diametrically opposed two camera technologies: progressive scanning (using a linear CCD camera) and block-by-block scanning (using a general CCD camera). The 100% comprehensive inspection system based on block-by-block scanning is relatively technically updated, and the application on some packages is better than the progressive scanning technology.
The 100% sampling system will detect only the faults that the camera sees at a particular moment in time at a particular print location. To be precise, the 100% sampling type detection system does not have the function of finding a fault on the entire printed product. Their advantage is the ability to accurately monitor certain specific characteristics of the process quality, such as color, overprinting, streaks, and repetitive failures. 100% comprehensive inspection technology can help you find the defects on the entire print, but the investment of this kind of system is more than 3 times of the usual type. The customer must prove that there is real need, and the investment can have real return. The printing manufacturer must do some investigation work before actually purchasing the inspection system. It is necessary to investigate the types of printing waste that are currently facing and the reasons for the formation. According to different reasons, a suitable inspection system can be selected and the remedy can cure the chronic disease.
2. Working principle
The automatic printing fault detection system is a new kind of auxiliary equipment. This kind of equipment is designed to actively look for possible problems on the printed pages during the printing process. The automatic printing fault detection system can help the operator to monitor the quality of the product in the printing process in all directions and ensure that every product printed is a qualified product. Most of the detection systems it employs use high-resolution, high-speed camera lenses to capture standard images and set a certain standard on the basis. Then, the images to be detected are taken and the two are compared. The CCD linear sensor converts the change in the light quantity of each pixel into an electronic signal. After the comparison, if the detected image is different from the standard image, the system considers the detected image to be a defective product, as shown in the following figure. The various errors that occur in the printing process are only different from the standard image and the detected image for the computer. Faults such as smudges and ink dot chromatic aberration are included.
Among them, the technology used by the 100% sampling system is similar to the roller observation system. In fact, this type of inspection system only adds extra software to the drum observation system. A video camera is fixed on a beam with an engine and equipped with a flash device. In a series of printing processes, the system can constantly scan and move from one marked place to another mark each time the flash takes pictures. During this time, the marker for each position was scanned, but only a small number of markers were captured by the camera after flashing. Each marked print image is compared with the main image in memory. Any difference can be displayed on the screen to report to the operator and issue a warning. The system is very good for the observation of the drum image, because after all, the operator can see the image in a small area every time. However, for the automatic quality inspection system, it seems that it is sometimes possible to pick out the problems in the printing, and sometimes it cannot. In other words, this system works intermittently.
A 100% comprehensive system uses a completely different approach. It still requires a beam with an engine and permanently installs several cameras throughout the length of the drum. These cameras are usually of the line scan type. This means that instead of using a flash to take a snapshot of the print, the camera uses a continuous illumination system to sample samples one row at a time in the length direction of the drum. When the roller rolls and the printing is completed, the system samples the next line of samples. The retrieved sample information is continuously compared with the main image stored in the memory. The main image is composed of print information having the same length as the print product and the same width as the drum length. Once the detection system detects something wrong, then they not only match in the length direction of the drum, but also in sync with the speed of the printing press, it can always detect the quality of the pixel in the corresponding position.
In addition, the fault information detected by the automatic printing fault detection system can be used not only as a warning and an alarm, but also as a fault report and data collection. The information is usually collected into a database and entered into the existing PC network through the interface, so that the data can be analyzed from the printer. The screen can show where the speed and the fault occur in the transverse direction of the drum, as well as the type of catch failure. Scroll bars can help operators see early data and previous data. At the end of printing, the print report will be automatically produced.
3 detection accuracy
The earliest technique used for the quality inspection of printed matter was to compare the gray scale of the standard image with the detected image. Now the more advanced one is based on the comparison of RGB three primary colors. Where is the difference between automatic machine detection and human eye detection? Taking human eyes as an example, when we look at a certain printed matter intently, if the contrasting color of the printed matter is relatively strong, the smallest flaw that can be discovered by the human eye is a defect whose contrasting color is not less than 0.3 mm, but depends on the person’s It is difficult to maintain consistent, stable visual effects. In another case, if defects are found in prints of the same color, especially in a light color system, the defects that the human eye can detect need at least 20 gray levels. Automated machines can easily find defects of 0.1mm size, even if the defect is only one gray level difference from the standard image.
However, in terms of practical use, even the same panchromatic contrast system has different ability to discriminate color differences. Some systems can find contours and defects with large variations in color, while others can identify very small defects. For white cardboard and some simple style prints, such as the Japanese KENT cigarette label, the United States Marlboro cigarette label, simple detection may be sufficient, and most of the domestic print, especially various labels, has many characteristics, With too many flash elements, such as gold, silver cardboard, hot stamping, embossing, or polishing prints, this requires that the quality inspection equipment must have sufficient ability to find the smallest grayscale differences, perhaps 5 shades of gray. The difference in level may be a stricter one gray level difference. This point is crucial to the domestic label market.
Accurate comparison between the standard image and the printed image being examined is a key problem for the detection equipment. Usually, the detection equipment collects the image through the lens. In the middle part of the scope, the image is very clear, but the image of the edge may be false. Shadow, and the detection result of the phantom part directly affects the accuracy of the entire test. From this point of view, if it is only the comparison of the entire area, it is not suitable for some fine prints. If the obtained image can be subdivided again, for example, the image is divided into 1024dpi×4096dpi or 2048dpi×4096dpi, the detection accuracy will be greatly improved, and at the same time, because the phantom of the edge portion is avoided, the detection result is more stable.
4. Detection parameters
After setting the quality inspection parameters, will the use of high-speed, automated quality inspection equipment lead to excessive scrap rates? The increase in scrap rates will undoubtedly lead to lower profits. But in fact all quality standards are relative, such as the generally unacceptable minor defects, if it is in certain areas (gluing, subsistence) is acceptable. In the case of manual detection, a properly relaxed, flexible standard can be automatically formed. How can rational and data-based detection be completed? It is reasonable for the printer and the end user to reach an agreement and adopt a sub-regional and hierarchical quality inspection standard for the printed matter. This is only a rigid rule, but must be a quantifiable standard that can be manipulated and accepted by all parties. And these standards must be all kinds of data set by the user, such as the area to be detected, the detection level of each area, and the testing standards to be performed at each detection level. For example, we first partition the printed products tested, such as dividing the printed matter into the most rigorous testing areas - the most important parts of the print (trademarks, products), the strict inspection area - important parts (products), general inspection areas - backgrounds, neglected areas - Concealed parts (on the rubber wing, life part). Then, set each detection level. This point is very critical, it will directly relate to the ability to find faults, but also directly related to the number of reject rate, so customers will certainly require an acceptable and reasonable range of tolerances, including the setting of acceptable, fault-size Range tolerance, acceptable, fault gray tolerances.
5. Benefits
1 continuous, proactive observation - 100% of the drum, 100% of the time.
2 Ensure that consistent quality is observed, not related to the operator's experience or changing classes.
3 Improve productivity by optimizing press speed and quality levels.
4 Provide early warning of impending failures.
5 Faults are displayed in color on the screen to quickly identify the nature and source of the fault.
6 When printing expensive materials, maximize its print throughput and reduce overprint.
7 Reducing the waste of expensive printing materials, minimizing its usage, lowering costs, and improving customer retention.
8 Improve the company's image and make it competitive.
9 can be used in accordance with the requirements of the ISO9000 standard.
10 It is easy to produce short-term products with higher efficiency.
Helps maximize the use of existing equipment.
Today, full-automatic printing failure detection is a technology that is relatively unsatisfactory, but with the further development of cameras and computer systems, the networking of work processes, and the integration of data management functions, this technology will surely be acquired. With new development, printing quality and efficiency will surely be greatly improved.
In terms of printing quality inspection, countries such as Europe, America and Japan have made great progress. As early as the 1970s, there have been vendors actively working with image processing systems to digitize visual information, achieve "seeing" and "cognition" of print quality through computers, and conduct high-speed, high-precision printing on printed materials. 100% real-time detection completely eliminates human error and establishes a uniform and quantifiable detection standard. At present, BOBST (Switzerland), PROIMAGE (USA), DAC (Japan), and TOKIMEC (Japan) can provide full automatic print quality inspection equipment.
Type
At present, there are two basic types of detection systems for automatic printing fault detection technology, namely 100% sampling type and 100% full type.
A 100% sampling system refers to a site that is repeatedly selected for printing within a period of time. The site is monitored 100%. The repeat time can range from a few seconds to several minutes. The 100% comprehensive system monitors 100% of each part of the product processed on the press. The two systems use diametrically opposed two camera technologies: progressive scanning (using a linear CCD camera) and block-by-block scanning (using a general CCD camera). The 100% comprehensive inspection system based on block-by-block scanning is relatively technically updated, and the application on some packages is better than the progressive scanning technology.
The 100% sampling system will detect only the faults that the camera sees at a particular moment in time at a particular print location. To be precise, the 100% sampling type detection system does not have the function of finding a fault on the entire printed product. Their advantage is the ability to accurately monitor certain specific characteristics of the process quality, such as color, overprinting, streaks, and repetitive failures. 100% comprehensive inspection technology can help you find the defects on the entire print, but the investment of this kind of system is more than 3 times of the usual type. The customer must prove that there is real need, and the investment can have real return. The printing manufacturer must do some investigation work before actually purchasing the inspection system. It is necessary to investigate the types of printing waste that are currently facing and the reasons for the formation. According to different reasons, a suitable inspection system can be selected and the remedy can cure the chronic disease.
2. Working principle
The automatic printing fault detection system is a new kind of auxiliary equipment. This kind of equipment is designed to actively look for possible problems on the printed pages during the printing process. The automatic printing fault detection system can help the operator to monitor the quality of the product in the printing process in all directions and ensure that every product printed is a qualified product. Most of the detection systems it employs use high-resolution, high-speed camera lenses to capture standard images and set a certain standard on the basis. Then, the images to be detected are taken and the two are compared. The CCD linear sensor converts the change in the light quantity of each pixel into an electronic signal. After the comparison, if the detected image is different from the standard image, the system considers the detected image to be a defective product, as shown in the following figure. The various errors that occur in the printing process are only different from the standard image and the detected image for the computer. Faults such as smudges and ink dot chromatic aberration are included.
Among them, the technology used by the 100% sampling system is similar to the roller observation system. In fact, this type of inspection system only adds extra software to the drum observation system. A video camera is fixed on a beam with an engine and equipped with a flash device. In a series of printing processes, the system can constantly scan and move from one marked place to another mark each time the flash takes pictures. During this time, the marker for each position was scanned, but only a small number of markers were captured by the camera after flashing. Each marked print image is compared with the main image in memory. Any difference can be displayed on the screen to report to the operator and issue a warning. The system is very good for the observation of the drum image, because after all, the operator can see the image in a small area every time. However, for the automatic quality inspection system, it seems that it is sometimes possible to pick out the problems in the printing, and sometimes it cannot. In other words, this system works intermittently.
A 100% comprehensive system uses a completely different approach. It still requires a beam with an engine and permanently installs several cameras throughout the length of the drum. These cameras are usually of the line scan type. This means that instead of using a flash to take a snapshot of the print, the camera uses a continuous illumination system to sample samples one row at a time in the length direction of the drum. When the roller rolls and the printing is completed, the system samples the next line of samples. The retrieved sample information is continuously compared with the main image stored in the memory. The main image is composed of print information having the same length as the print product and the same width as the drum length. Once the detection system detects something wrong, then they not only match in the length direction of the drum, but also in sync with the speed of the printing press, it can always detect the quality of the pixel in the corresponding position.
In addition, the fault information detected by the automatic printing fault detection system can be used not only as a warning and an alarm, but also as a fault report and data collection. The information is usually collected into a database and entered into the existing PC network through the interface, so that the data can be analyzed from the printer. The screen can show where the speed and the fault occur in the transverse direction of the drum, as well as the type of catch failure. Scroll bars can help operators see early data and previous data. At the end of printing, the print report will be automatically produced.
3 detection accuracy
The earliest technique used for the quality inspection of printed matter was to compare the gray scale of the standard image with the detected image. Now the more advanced one is based on the comparison of RGB three primary colors. Where is the difference between automatic machine detection and human eye detection? Taking human eyes as an example, when we look at a certain printed matter intently, if the contrasting color of the printed matter is relatively strong, the smallest flaw that can be discovered by the human eye is a defect whose contrasting color is not less than 0.3 mm, but depends on the person’s It is difficult to maintain consistent, stable visual effects. In another case, if defects are found in prints of the same color, especially in a light color system, the defects that the human eye can detect need at least 20 gray levels. Automated machines can easily find defects of 0.1mm size, even if the defect is only one gray level difference from the standard image.
However, in terms of practical use, even the same panchromatic contrast system has different ability to discriminate color differences. Some systems can find contours and defects with large variations in color, while others can identify very small defects. For white cardboard and some simple style prints, such as the Japanese KENT cigarette label, the United States Marlboro cigarette label, simple detection may be sufficient, and most of the domestic print, especially various labels, has many characteristics, With too many flash elements, such as gold, silver cardboard, hot stamping, embossing, or polishing prints, this requires that the quality inspection equipment must have sufficient ability to find the smallest grayscale differences, perhaps 5 shades of gray. The difference in level may be a stricter one gray level difference. This point is crucial to the domestic label market.
Accurate comparison between the standard image and the printed image being examined is a key problem for the detection equipment. Usually, the detection equipment collects the image through the lens. In the middle part of the scope, the image is very clear, but the image of the edge may be false. Shadow, and the detection result of the phantom part directly affects the accuracy of the entire test. From this point of view, if it is only the comparison of the entire area, it is not suitable for some fine prints. If the obtained image can be subdivided again, for example, the image is divided into 1024dpi×4096dpi or 2048dpi×4096dpi, the detection accuracy will be greatly improved, and at the same time, because the phantom of the edge portion is avoided, the detection result is more stable.
4. Detection parameters
After setting the quality inspection parameters, will the use of high-speed, automated quality inspection equipment lead to excessive scrap rates? The increase in scrap rates will undoubtedly lead to lower profits. But in fact all quality standards are relative, such as the generally unacceptable minor defects, if it is in certain areas (gluing, subsistence) is acceptable. In the case of manual detection, a properly relaxed, flexible standard can be automatically formed. How can rational and data-based detection be completed? It is reasonable for the printer and the end user to reach an agreement and adopt a sub-regional and hierarchical quality inspection standard for the printed matter. This is only a rigid rule, but must be a quantifiable standard that can be manipulated and accepted by all parties. And these standards must be all kinds of data set by the user, such as the area to be detected, the detection level of each area, and the testing standards to be performed at each detection level. For example, we first partition the printed products tested, such as dividing the printed matter into the most rigorous testing areas - the most important parts of the print (trademarks, products), the strict inspection area - important parts (products), general inspection areas - backgrounds, neglected areas - Concealed parts (on the rubber wing, life part). Then, set each detection level. This point is very critical, it will directly relate to the ability to find faults, but also directly related to the number of reject rate, so customers will certainly require an acceptable and reasonable range of tolerances, including the setting of acceptable, fault-size Range tolerance, acceptable, fault gray tolerances.
5. Benefits
1 continuous, proactive observation - 100% of the drum, 100% of the time.
2 Ensure that consistent quality is observed, not related to the operator's experience or changing classes.
3 Improve productivity by optimizing press speed and quality levels.
4 Provide early warning of impending failures.
5 Faults are displayed in color on the screen to quickly identify the nature and source of the fault.
6 When printing expensive materials, maximize its print throughput and reduce overprint.
7 Reducing the waste of expensive printing materials, minimizing its usage, lowering costs, and improving customer retention.
8 Improve the company's image and make it competitive.
9 can be used in accordance with the requirements of the ISO9000 standard.
10 It is easy to produce short-term products with higher efficiency.
Helps maximize the use of existing equipment.
Today, full-automatic printing failure detection is a technology that is relatively unsatisfactory, but with the further development of cameras and computer systems, the networking of work processes, and the integration of data management functions, this technology will surely be acquired. With new development, printing quality and efficiency will surely be greatly improved.
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