How to strengthen internal control to ensure the quality of inspection

Print quality online detection technology uses machine vision instead of human eyes to check the quality of printed products, overcomes the insufficiency of the human eye and maintains the stability of the inspection. It can record the test results and lay the foundation for the digitalization, dataization and standardization of printing production. Print quality can be traced throughout.

1. Setting of detection accuracy

Conventional printing process control is performed by printing a printed control strip on a sheet and then using a density method or a chromaticity method. The online quality detection system based on digital image processing technology analyzes and detects digital images, which is quite different from traditional density or chromaticity detection methods. In addition, even if both print quality online detection systems based on digital image processing technology are used, the control parameters and accuracy settings are quite different if different detection principles and methods are used.

Therefore, the on-line inspection system for print quality should have acceptable and quantifiable detection indicators, and the parameter settings should be as regular as possible. For example, the description of the overprint deviation, the broken line, and the like is a unit of length, and the description of the impurity, the ink dot, and the like is an area unit, and the detection requirement can be intuitively set for the quality defect of this type. For some types of defects that cannot be well identified by the system (such as ghosting, floating, etc.), when setting the index parameters, multi-faceted testing should be carried out according to the characteristics of the system. According to the product tolerance requirements and the system testing capability requirements, each is determined separately. The control threshold of the parameter ensures that the system detection capability can meet the actual production requirements.

In addition, in the setting of the detection accuracy, a standard that is appropriately tightened and flexible can be selected. If the accuracy is set too high, although the product defects can be reflected in real time, the workload of the quality inspectors will be increased, and the work efficiency will be reduced. If the accuracy is set too low, the leak detection will easily occur, resulting in the outflow of defective products. For example, in the rotary printing, the continuous dirty version phenomenon often occurs. If the problem is not processed in time, it will become more and more serious, and eventually the waste will be generated. If the precision setting is properly tightened, the system will give an alarm when the parameter reaches the critical value. The operator can adjust the printing status in time to stabilize the quality within a reasonable range.

2. Partitioned hierarchical control

For most ticket products, the quality requirements of different areas of the ticket face are often different. Therefore, in the system setting, the quality of the detection area can be set according to the degree of importance, and the difference can be distinguished by the difference in detection accuracy. For example, the important areas such as the “amount area” and “password area” in the bill should be strictly inspected, and the area that does not affect the overall effect of the product can be relaxed. Even if there is a slight defect, it can be regarded as a qualified product, thus greatly reducing The number of errors.

3. Inspection system maintenance

Since the printing effect is affected by many factors such as mechanics, chemistry, environment, etc., it is difficult to ensure that the printing effect of each batch is completely consistent in the process, and the detection system directly affects the determination of product quality, so the detection system is very important for printing quality control. . Our company has included the use and management of inspection systems into routine production management procedures. For example, the detection function of the detection system is periodically verified to ensure the stability of the detection function in different environments; the hardware devices such as the light source and the lens related to the detection system are regularly maintained to be in the normal detection state; when the standard template is generated and replaced Quality inspectors should check to ensure that the standard template is not replaced at will.

4. Operator training

Although the print quality online detection system can alleviate a lot of work, it is a new thing, and it puts high demands on the operators in terms of system recognition and operation. In the production process, the variable production environment leads to more uncontrollable factors. In order to effectively ensure the system to perform stable and precise inspection, the operator is required to have a certain degree of understanding of the system. Therefore, increasing the training of system-related personnel can enable the system to better serve production.

The above content is selected from Keyin Media. Printing Technology ·Digital Graphic Arts , No. 5, 2013, please pay attention to the journal channel for more journal content . Click on the latest journal content to enter the electronic journal channel of

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