Some Problems and Countermeasures of Quality Management of Printed Products

I. Introduction

No matter which type of printed material is produced, it must go through several processes in order to transfer the graphic information on the original to the substrate. Due to the rapid development of printing technology, standardization and quality control have become an important issue.

In scientific research, measuring and controlling quality is fundamental. In the printing process, the most important thing is to measure, improve, and control the printed raw materials, the printing equipment used, the technology used, and the quality of the finished product. At present, there are already a series of national standards that are consistent with international standards for the quality of printed products and testing methods. They require that each raw material used in the printing, each printing process, and finished product in each process must be measured or tested according to this standard to determine whether the requirements of the technical standards are met.

It is difficult to control the quality of raw materials in printing. The main raw materials used in printing are paper and ink. As far as paper is concerned, there are no less than twenty experiments on the suitability of printability and print quality, but no single instrument can measure the overall quality of printed paper. The same is true for ink experiments. There are also some problems with the quality control of printed products. Many of the originals have different requirements for use in printing. In many cases, technical standards are established by the user in consultation with the printer or seller. If there is no instrument and method that both parties recognize to identify this standard, this technical standard cannot be discussed.

At present, there are roughly three methods for evaluating the quality of printed matter: subjective evaluation method, objective evaluation method, and comprehensive evaluation method. The subjective evaluation method is based on a manuscript and is evaluated against a proof. The human factors here are due to differences in the appraiser's knowledge, skills, experience, hobbies, and aesthetic perspectives, which will to a large extent cause appraisal biases. The objective evaluation method is to quantitatively analyze the various quality links of printed products through specialized equipment and tools, and to make objective evaluations in conjunction with the quality standards for reproduction. The comprehensive evaluation method combines subjective and objective evaluations to evaluate print quality. At present, it seems that this is the best evaluation method.

Quality control is always an indispensable part of the printing process. Experience and superb craftsmanship were once the sole basis for quality control in the printing process. For example, visual and tactile determination of ink viscosity or color accuracy, although the eye is very sensitive to the difference in color and density, but it can not objectively, accurately and quantitatively reflect the quality of the situation. Only the use of special equipment and tools to test the basic properties of various raw materials and monitor the quality of printed products can produce stable and high-quality products.

Second, conventional control

An important part of print quality management is conventional control. The conventional control of printing quality refers directly to the control work that printing production personnel must perform. The conventional control of printing quality is mainly carried out in the printing shop. The implementation of the first-line printing operator is a routine control of one or several items. It is actually a kind of operation specification and usually should include the preparation for printing, the control of the printing process and the inspection of printed products.

1. Pre-print preparation

The inspection of graphic quality in the early stage of printing is the first inspection of graphic content. It needs to check the construction slips and proofs, and at the same time check for errors or defects in images, text, symbols, lines, etc. This inspection is relatively simple, as long as the thickness meets the standards and smoothness is fine.

Second, it is the inspection of the image quality. The quality of the image on the plate is the basis for the quality of the print. Without high-quality images on the plate, there is no high-quality print. The inspection of the image quality is performed by checking the outlets. Because whether it is a monochrome continuous-tone original or a color continuous-tone original, the printed image is represented by dots.

The contents of the inspection are conducted in two aspects.

One is the inspection of image imprints. With a visual inspection method, the monochromatic proofs and the corresponding parts of the printing plate are compared to observe if the shade of the printed product is the same. In addition to the overall observation, you can also choose to focus on observations. Observe whether the size of the dot is consistent with a magnifying glass, and the key area should be selected at the deepest part, the most shallow part, and the most important part of the image content. The hue of the main part after the printing is suitable for the requirement, the printing will not have big deviation. Due to the spread of ink in the printing and the dual reflection of light, the printing dots must have a certain degree of expansion. Therefore, the dots on the printing plate should be slightly smaller than the dots on the monochrome proof, and must not be larger than the dots on the proof sheet. In addition, you can use the test strip to check the depth of the plate.

The second is the inspection of the quality of outlets. The quality of the network is an important guarantee of image quality. With high-quality outlets, there will be high-quality reproduction and high-quality color reproduction. The dots on the plates must be real, the edges should be clear, and the best surrounding is bright and clean. Hairiness at the edge of the mesh will reduce the ink's adsorption performance during printing, and the mesh itself will exhibit unstable conditions. It is common to use a magnifying glass with a magnification of 10 or more to check the formation of dots.

2. Control of the printing process

In the lithography process, the paper, fountain solution, ink and printing plate contact with each other, and there are many changes. Inadequate carelessness will cause uneven ink and other ills. This has a great influence on the print quality.

Before the printer is officially turned on, the printing machine must undergo a trial printing operation so that the printing color is the same as the proof color. After signing, we can start printing. The work of signing the monochrome machine is even more important. It is related to whether the color of the finished image can be faithfully restored. In actual production, many products are checked at the third level, but there are still a considerable number of color shifts in the finished product image due to inaccurate sampling. This requires the operator, especially the operator of the monochrome machine, to be able to accurately determine the color deviation by using the measuring and control strips and other measuring instruments after each one-color printing.

The printing process is completed during high-speed operation, so the control of the ink balance will be critical. Moreover, practical experience also tells us that in the printing production, we are trying hard to achieve "three services", that is, Dijun, diligence, and diligent inspection are the most effective quality control measures in the printing process. Among them, the “Diligent Inspection” item L requires the quality of proofs to be checked during the printing process. During the printing process, the operator must often check the newly printed sheets. It includes the accuracy of the printing position and the quality of the printed image. These two items.

3. Inspection of printed products

Each printing shop or printing factory will have a finished product to inspect this post. The main contents of the inspection of printed products are as follows:

The first is to check the color and registration of printed products using color code and rules.

The second is to judge the overall quality of printed products (including color, layer, register, surface conditions, and drying conditions). Mark bad products (folding or clips, etc.) and draw them out in time. In addition, pay attention to the incorporation of other prints.

The third is the counting check, that is, checking whether the number of printed sheets is sufficient, usually a piece of paper clip is attached for every 500 sheets.

The conventional control of printing quality is a very complex, meticulous and important work in the printing shop. It directly affects the quality of printed products, affects the image of printing companies, and affects the survival and development of printing companies. Therefore, the printing shop must persist in this and always make unremitting efforts.

Third, the conclusion

The data quality of the printing quality control is through the necessary test methods, and the necessary control factors of the printing quality are measured and recorded in the form of data to serve as the basis for quality control. Standardization means that a series of laws that can guide production, such as formulas, curves, charts, data, etc., can be summarized through a large amount of data. At the same time, there are three standards for measuring the degree of data and standardization of printing quality control: First, stability is good, second, reproducibility is good, and third, efficiency is high.

Looking at the current status of China's printing industry, the dataization and standardization of printing quality control is far from the international developed countries. Therefore, how to improve and strengthen the digitization and standardization of printing quality control from the technical and management perspectives is the responsibility that the majority of printing workers cannot shirk, and it will also be the key to the survival of printing companies in the fierce competition in the future.

Author (Xu Faqiang)