Exploring online quality and offline rejection of flexible packaging printing quality

First, the status of intaglio printing quality control

The quality control of gravure includes both process control and result control. In the process of gravure printing, both process control and result control are indispensable. They are not only the key points for quality improvement in printing enterprises, but also the basis for formulating quality improvement measures.

In-print control is the standardization, standardization and data-based operation of each process of gravure printing. A certain quality standard is adopted to establish a quality control prevention mechanism. In the printing process, the main concern of the printer is to prevent continuous costs or a large amount of waste, and to prevent material waste. The defects that may cause a large amount of waste are overprinting, knife wire, chromatic aberration, and a large amount of flying ink.

The main means of current quality control in India is the computer overprint control system to control overprinting, still picture, strobe light control system. However, the premise of the normal operation of the computer overprint control system is that the tension of the system is stable. If the tension is unstable, the overprinting will be inaccurate, and the computer adjustment cannot be completely corrected. The current gravure printing machine has very limited control over the tension fluctuation. Therefore, even if there is a computer overprint control system, the printing process can not be completely guaranteed to be completely stable; the still picture and the strobe light are sampling the product quality, and the product quality cannot be fully monitored.

Post-press control is the inspection and control of the overall quality of printed products after printing. The main detection method is to use stroboscopic lamps for spot check in the process of rewinding, slitting and bag making.

Second, flexible packaging machine visual quality inspection system

The main defects of the flexible packaging printing industry (such as overprinting, knife wire, ink dot and other defects) are all appearing in the printing process, and the chances of defects appearing in the post-pressing process are less. With the development of technology, two kinds of machine vision-based printing quality inspection systems have emerged in the field of soft-package quality inspection for the two stages of printing control and post-press control in gravure quality control: online quality inspection system and offline quality inspection system. Its main purpose is to replace manual testing. The online quality inspection system is mainly installed on gravure printing machine, flexo printing machine and hot stamping machine to detect continuous waste in the printing process, and provide sound and photoelectric alarm to remind the operator to adjust the printing machine accordingly; the offline quality inspection system is mainly installed in On the post-press equipment such as rewinding machine and slitting machine, it is mainly used for finished product inspection to ensure the quality of the products. Part of the soft packaging and printing companies, have adopted the visual line detection system or off-line detection system.

On the whole, online quality inspection systems and offline quality inspection systems have their own advantages and disadvantages.

1. Advantages of online quality inspection system:

1) It can monitor the defects generated in the printing process in real time, prompting the operator to make timely adjustments to avoid and reduce defects.

2) It can reduce material waste and save costs by reducing printing waste.

3) Real-time statistical analysis of the defects that occur, prompting the printing company to improve the overall printing process.

2. Disadvantages of online quality inspection system:

1) After the defect is detected, the shutdown process cannot be performed.

2) Only prints of the installed presses can be detected.

3) The requirements for operators are high. The users of the online quality inspection system are generally printers. The printing company is in consideration of cost, and no special person is responsible for the online quality inspection system. While the printer is responsible for the high-speed printing and debugging of gravure printing, it also needs to take into account the operation of the online quality inspection system, which puts higher requirements on the operation skills of the printer.

3. Advantages of offline quality inspection system:

1) Testing products that have been printed and post-pressed to ensure that the final delivery of the product is qualified and to improve customer satisfaction.

2) An off-line quality inspection system can detect the prints of multiple presses.

3) Downtime processing can be performed after the defect is detected.

4. Disadvantages of offline quality inspection system:

Printing defects can not be avoided and reduced (after processing).