The ink purchase volume of a medium-sized book printing company is about 150 tons/year.
The unit price of ink is calculated at 40 yuan/kg.
The ink cost of this printing company is about 6 million yuan a year.
Then the problem is coming,
Do we really use so many inks?
Are the inks purchased from the best use of the ink?
Introduce an accurate ink usage calculation method today.
Since the switching of different printing orders usually does not require ink replacement, the material control department of the printing enterprise cannot predict the ink usage per unit time or single order, and in the prepress production process of most printing companies, it will not predict printing. The amount of ink used in the machine.
Therefore, printing companies often over-purchasing inks, occupying valuable funds and storage space, and the ink in the production workshop is not controlled by the materials, so that operators often do not have the awareness of saving ink, and waste is widespread. Although some printing companies will roughly estimate the amount of ink used, it is not accurate. In this paper, the author will introduce a more accurate calculation method of ink usage.
Past ink usage estimation method
The previous ink usage estimation method was carried out according to the following formula:
Printing ink quality = printing ink volume × ink density
among them,
Printing ink volume = printing area × printing ink thickness
The accuracy of the ink usage estimated by this method is low, mainly because of the following two points:
First, the thickness of the printing ink is difficult to measure accurately. Since the thickness of the offset ink layer is actually only about 2 to 3 μm, measurement is difficult and the precision is low.
Second, this method only calculates the amount of ink printed on the paper surface. In the offset printing system, various components in the ink are also involved in the following processes: emulsification of fountain solution (ink balance), dry evaporation, paper Permeation absorption and the like. These ink loss amounts are ignored, resulting in inaccurate ink usage calculations.
An accurate method for calculating ink usage
The basic idea : the ink on the printed product is presented in the form of dots. That is, for a certain color printing, there are only two states of ink and non-inking on the printed product. Therefore, we propose the following ink usage calculation formula:
Printing ink quality = ink coverage area × unit area solid ink consumption × printing quantity calculation ink coverage area
This process is mainly to read prepress files through Prinergy software, use the software's PrintLink function to export relevant data, and then calculate the ink coverage area of ​​the printed documents. Specific steps are as follows:
(1) Under the Prinergy software, make a file for outputting the plate and the layout, and the file format is in PDF format.
(2) Put a large version of the printed sheet or signature and output a 1-bit-tiff file.
(3) Using the PrintLink function of Prinergy software, the TXT file is output, which contains the solid ink coverage under a certain printing surface.
(4) Calculate the average solid ink coverage of the entire job. For example, for book printing , there will be several signatures after the prepress printing, each signature will have two or one printing surface, and each printing surface will use PrintLink to output a TXT with solid ink coverage information. File, extract the average percentage of the corresponding color inks under each TXT file, and calculate the average value, which is the book's average solid ink coverage.
In the actual operation, if you calculate manually, there will be a large workload. Because a book often consists of multiple signatures, if there are 100 signatures, 100 TXT files will be generated, which is computationally intensive and error-prone. Therefore, we have compiled a macro program that directly extracts the relevant data in each TXT file and then aggregates it into an Excel file to quickly calculate the average in-situ ink coverage of the book.
(5) According to the following formula, the ink coverage area of ​​the job can be calculated:
Ink coverage area = paper area × average solid ink coverage rate Calculated per unit area of ​​solid ink consumption
The calculation of the ink consumption per unit area in the field is based on the actual printing test, and the calculation method is as follows:
In-situ ink consumption per unit area = actual ink quality ÷ total number of sheets ÷ the actual ink coverage area of ​​the screen
Ordinary commercial printing uses CMYK four primary color inks. It is only necessary to establish the ink layer thickness data corresponding to the combination of various types of paper and primary color inks, and the amount of each color ink can be calculated. Through the existing color management system, the ink consumption per unit area under standard conditions is measured, and the unit is kg/m2.
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