Quality inspection and control of printed materials

Author: Chen Derong (Translator)
Publisher:
Publish Date: 2005-05-09
Features: To improve the quality of printed materials in China, the translator selected and translated 22 articles from numerous papers on the detection, evaluation, and control of printed material quality from abroad. The content includes quantitative evaluation of printed material quality, print quality measurement platforms, density measurement and colorimetric measurement, discussion on the mechanism of ink transfer, the relationship between the physical conditions of the printing area in offset presses and print quality, as well as the printability of inks and papers. It showcases the current international level in this field. The content of this book is suitable for print quality management personnel, printing technicians in printing plants, and teachers and students in printing vocational colleges and universities. Excerpt: Image resolution on a printing press is primarily affected by factors related to ink thickness. The thicker the ink layer, the higher the clarity. Ink thickness and solid density are all limited to the values discussed in the previous chapters. Resolution is also limited by ink thickness. Sometimes, higher resolution can be achieved through thinner ink layers. Johnson's research results have shown that in letterpress printing, the smallest details that can be resolved are approximately 8 micrometers (μm). This resolution level allows the use of a screen with 300 lines per inch. The resolution capability of the screen is slightly higher than that of the human eye at a standard reading distance. In color printing, image resolution is also affected by the registration accuracy between colors. Johnson pointed out that for modern printing machines operating under good conditions, the error in feeding all single sheets is actually within ±0.003 inches. The variation in color registration depends on the design of the printing job. Random variations are about 0.002 inches. In practice, to achieve satisfactory printing results, the registration error for all colors should be kept within ±0.004 inches. Spots and defect patterns Theoretically, it is possible to reduce all spots and defect patterns related to printing to zero. Economically, it is possible to reduce all types of spots to any reasonable level. In some cases, defect patterns can be eliminated. However, for issues such as ghosting, ink bleeding, and mottling caused by mechanical reasons, operators have no control. In these cases, the structure of the ink transfer system, the absorbency of the paper, and the screen angle all determine the extent of these defect patterns. On a printing press, spots and grain on films or plates cannot be corrected. Therefore, they all appear on the printed sheet. Surface characteristics The surface characteristics of the printed sheet can also be adjusted to approach an ideal level. The texture of the image varies depending on the substrate used. Generally, for the best photographic reproduction, it is best to use very smooth paper. The flatness issue is caused by the texture, bubbles, and delamination of the paper. All these factors can be controlled to produce perfectly flat printed materials. Glossiness The glossiness of the printed material is related to the glossiness, absorbency, and ink thickness of the substrate. The thicker the ink layer, the higher the glossiness. In practice, it is difficult to achieve a glossiness value above 90%. Postscript: The evaluation, measurement, and control of printed material quality should naturally attract our attention and concern. The reason is self-evident. To introduce the development of this field abroad to the domestic printing industry, papermaking industry, ink manufacturing industry, and all concerned parties, the translator has made every effort to gather some materials from foreign books and journals, translated and compiled them into this book, and now presents them to the readers. The main sources of the book's content are: 1. Advances in Printing Science and Technology 2. taga 3. Professional Printer The content of this book covers a wide range of disciplines, and some technologies are still under development. Although the translator has been careful, errors in translation are inevitable. We sincerely ask the readers to point them out. During the compilation and translation of this book, we received great assistance from the leaders and colleagues of the Printing Industry Press. Associate Editor Pang Doyi carefully and meticulously proofread all the translations. Sincere thanks are extended to them. Chen Derong July 23, 1989