Since 90s, printing industry has been faced with small batch, multi variety and high quality demand. Users are more and more strict in the quality of products. In the printing enterprises, the quality assurance evaluation is the core of the competition to enhance the brand effect. Strive for survival by quality, and develop with credit. Therefore, it is necessary to manage the standardized quality of printing products.
The quality of color printing products should be controlled by the current qualitative management and experience, and gradually develop towards quantitative management and scientific school system.
The quality of printing products has certain characteristics, which not only reflects the quality standards of industrial products, but also reflects the artistic quality standards. At present, the quality and standard of printing products are generally divided into two types: empirical qualitative standard and scientific quantitative standard.
First. The standard of fixed residence calendar
In the production practice, people based on the appearance of printed products, in the condition of no detection means, by virtue of human feeling, according to the actual experience to determine the quality of the product, known as the qualitative quality of experience, can not grasp the law of product quality change, only after the end of printing evaluation.
Two. Quantitative quality standard
The quantitative standard of color printing product quality must be based on data and standardization. The best product quality can be obtained only by managing the operation under the control of scientific data. Under the condition of using instruments and equipment, quantitative data can be used to reflect quality.
1. quantitative standard for measuring optical density value:
Optical density is affected by the thickness of ink and the concentration of ink. Using optical instruments to measure the density data of ink, the correct relationship between ink volume and dot area is obtained.
2. the quantitative standard of chromaticity value: measuring the hue, saturation and density of the ink under certain ink thickness, and checking the technical specifications of the ink.
3. quantitative definition of outline definition: clear outline refers to the physical form that dot, text and line should be printed on paper.
4. the quantitative standard for measuring the accuracy of the printing.
5. size measurement standard for graphic and text.
6. high tone dot reproduction rate and so on.
In order to achieve the quantitative standard of the quality of the above printing products and realize the data and standardization of the quality of the products, it is necessary for us to implement some testing methods in Shanghai printing plant.
1. color signal strip. In printing, a strip is set on the plate. The purpose is to control the average quality of the printed matter and to focus on the ink color and uneven point of the printing start and final state. Because there are many factors that affect the quality of printing, the consequences of these factors will ultimately reflect the change of print and print nodes. In order to manage the quality of printed matter, from printing to printing, all kinds of signal strips are used to master the change rule of printing plate and picture. Therefore, the color signal bar is the first step in the three management of data quality.
2. the density value of the field and the dot dot expand, the field density of the ink is closely related to the color of the ink, the saturation of the ink, the thickness of the ink layer and the physical condition of the paper surface. And the tone of the image varies with the density of the field. As for dot gain, multicolor printing is the biggest reason for the contrast of the contrast of the printed material. In addition to the change in field density, dot enlargement is influenced by various factors such as printing pressure, rubber cloth state, printing speed, paper quality, net number and so on. Therefore, in the printing process, the density value of the field is controlled in the best state, and the dot enlargement and field density are monitored at any time, so the tone in the printing work can be well controlled.
3. the curve of the loan and the curve of dot enlargement. As we all know, dot gain is hard to avoid, but only with varying degrees. However, if we take full account of the factors such as dot gain and dot scaling, the printing of the printed manuscript may be closer to the color in the original image if we take full account of the factors such as dot expansion and so on.
4. correction of the phototypesetting machine. When the phototypesetting machine outputs the film, the printed product will not be in accordance with the tone of the original if the percentage of the actual output dot is not consistent with the value that should be output. So we have to adjust the signboard to the right condition.
How to ensure the correct transfer of dots and realize the correct restoration of hue is the key to guarantee and improve the quality of color printing products. Data and standardization are important means of modern production. It is an important technical measure to scientifically manage quality and improve technical and economic benefits.