At present, many printed products will use spot color inks to ensure the consistent color of the printed products; in anti-counterfeiting printing, in order to improve the anti-counterfeiting effect, security anti-counterfeiting spot color inks are often used; in map printing, due to the process and printing materials Limits, often use a lot of spot color printing, and some even reach more than 20 colors. However, spot color inks are often used in small amounts compared to four-color inks, and ink plants cannot produce on a large scale, resulting in high cost of spot color inks. Therefore, most spot color inks are prepared by the printing house itself. Due to the small amount of spot color ink, the color matching cannot be less than the actual amount, it is easy to leave ink, and long-term storage will affect the performance of the ink. For printing companies, the remaining ink is not a small problem, it will greatly affect the production cost and cannot be ignored.
To solve this problem, the fundamental solution is to accurately calculate the amount of ink used in printing. Some ink manufacturers or suppliers provide users with rough calculation methods of ink usage. For example, the Dutch VANSONINK ink company and the British Goss Ink Company have proposed their own ink amount calculation methods; domestic counterparts have also summarized some methods in practice . Hengsong will calculate the method of printing ink consumption for you (in offset printing mode, the printing machine works normally, and the quality can be printed).
To determine the amount of ink, we must first analyze the various factors and accounting methods that affect the amount of printing ink.
Printing area
The printing area and the thickness of the ink layer determine the volume of the ink, which in turn determines the amount of ink. The size of the printed area is determined by the graphic of the original, but it is not easy to determine the actual graphic area to be covered by each spot color. For manuscripts with regular graphics and a known dot percentage (flat screen), the actual printing area can be easily obtained, but for manuscripts with irregular graphics and rich image layers, how to calculate the actual printing area? Here is a calculation method-digital image processing method, the steps are as follows:
Digitally collect and store the original image of the given area. For the simulated plane image and text, it will be converted into a digital image and stored in the computer after being processed by the input device; the digital image original can be eliminated
Process the collected manuscript information, that is, find all the pixel points in the manuscript that meet the requirements, and do addition and processing;
The sum of the calculation results is output, which is the actual dot area to be printed.
Some printing plants use another calculation method, which is also more practical. The specific time: weigh the pattern to be printed after copying, and cut a piece of the same copy paper of 250px * 250px to weigh. area:
Graphic area = (100 * pattern copy weight) / square paper weight
1. Ink layer thickness
The thickness of the ink layer is also one of the decisive factors for the amount of ink. Due to the complexity and variability of printing conditions and substrate conditions, the uncertainty and unevenness of the ink layer thickness have been caused. As offset presses continue to develop in the direction of high precision and high reliability, when the quality of printed materials is guaranteed, the maximum error of the ink layer thickness during the printing process will not exceed 0.058 μm, and the impact on the total ink volume is relatively small, so the general situation Below, we can consider that the thickness of the ink layer in the above printing environment is uniform.
The value range of the thickness of the ink layer is not arbitrary. Generally speaking, under a specific printing environment (printing machinery, printing materials, ink and printing workshop temperature, humidity, etc.), there is an optimal thickness of the ink layer, on the one hand, it can make the ink color Fullness, field density and printing contrast value reach the maximum; on the other hand, it can minimize the dot increase value, achieve the best restoration of the layer, and the print quality is stable.
Two methods can be used to measure the thickness of the ink layer: one is the more common emphasis method, which is to compare the weight difference of a substrate sheet before and after printing, and then divide it by the module area.
2. Ink proportion
That is, the density of the ink is often measured in g / cm3. This parameter can be calculated using an ink suitability tester or ink spreader, and some ink suppliers provide this parameter.
3. Number of prints
That is the total amount of prints that need to be printed.
4. Substrate characteristics
If the substrate only considers paper, it can be roughly divided into two types: coated paper and uncoated paper. Paper's own ink absorption, surface smoothness and structural strength will affect the amount of ink. However, the specific impact of these factors on the amount of ink is difficult to determine accurately, suitable for qualitative analysis, or given in addition to other factors
5. Characteristics of printing equipment
The influence of printing equipment characteristics on the amount of ink is mainly reflected in two aspects: one is the effect of printing pressure and speed on the thickness of the layer and the increase of the dot; the other is the minimum amount of ink on the printing machine, that is, the actual printing process, To cover the ink required by each mechanical surface in the printing ink path, plus a certain amount of ink reserved in the ink fountain to stabilize the ink supply.
6. In the printing process, in addition to the partial ink loss in the inking process and the printing plate and blanket cylinder, some ink will be lost during the trial printing, so we must also consider the impact of this factor on the overall ink consumption. The amount of loss can be obtained by quantitative analysis according to the actual printing situation
7. Pre-stored ink
Due to the existence of various unknown factors, generally speaking, printing houses will allocate more common spot color inks and store them in advance. This parameter is determined by the printing house itself.
The analysis shows that for the two main factors of printing area and ink layer thickness, quantitative analysis is required to determine their precise values, and the results must be verified if necessary; there will be no large errors in ink specific gravity and number of printed sheets; substrate characteristics, printing equipment The characteristics are all qualitative analysis is more important than quantitative analysis; ink loss rate, pre-existing ink factors are related to the actual situation of printing capacity of printing plants. Although the values ​​of some other factors cannot be accurately determined, the accuracy of the calculation of the overall ink volume will not have much impact, and the possible errors can be controlled within a very small range.
After the above parameters are known, the required spot color ink volume can be obtained by the following formula:
The amount of ink used in a printed matter (g) = printing area * ink layer thickness * ink specific gravity
Total ink volume = the amount of ink used in a printed product * the number of prints and the minimum amount of ink inked + the amount of ink loss
Of course, the characteristics of substrates, printing equipment characteristics, ink consumption and pre-stored ink data have obvious personalities. These data are variable when different printing plants process different printed products, so they should be determined according to the actual situation.
In short, the control of the amount of spot color ink is very cumbersome and complicated. In order to save the cost of spot color ink in printing plants, Hengsong is perfecting the color matching center to reduce the cost of ink and provide scientific printing partners with the most accurate and quantitative science. Computer color scheme.
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