Anilox Roll Management Trilogy for Flexo Printing Machine from JCTPRINT（2）

 

2. Verification of BCM value

For a new anilox roller, in the first half year of use, its BCM value decay is the fastest. Therefore, what is the BCM value of the anilox roll before it is used must be controlled. Here are two methods to verify the BCM value of the anilox roller.

(1) BCM definition measurement method

The BCM definition measurement method is an early practical measurement method. First inject a unit volume of measuring ink on the anilox roller, then use a test blade to scrape the ink slowly and evenly, then press the A4 copy paper on the anilox roller by hand, transfer the ink by pressure, and finally use a special measuring instrument Measure the area of ink transferred on the A4 copy paper, the measured value is equivalent to the area of ink on the anilox roller. The BCM value of the anilox roller is obtained by dividing the unit volume of the measured ink by the ink area on the anilox roller.

This method is simple and easy to learn, but the operator needs a certain amount of time to practice repeatedly, which takes a long time. Normally, the operator must practice for 4 to 8 hours, and only after he is proficient can he control the measurement error to a small range, but the error is still around 3%. In the actual measurement process, a skilled operator can measure and calculate the BCM value of the anilox roller within 10 minutes.

（2）Three-dimensional optical measurement

The three-dimensional optical measurement method is a measurement method adopted by Jinan Jinchangtai Industry And Trade Co., Ltd. Its advantage is that it can accurately measure the anilox roll BCM value, but the required test equipment is expensive. If necessary, you can negotiate with Jinan Jinchangtai Industry And Trade Co., Ltd. to send the anilox roll back for measurement.

The three-dimensional optical measurement method directly measures the volume of the anilox, while the BCM definition measurement method measures a certain area of the anilox roller under a specific measurement of the volume of the ink. Both methods measure volume, and there is a common problem: the amount of ink carried by the anilox roller is not equal to the amount of ink transferred.

For example, an old anilox roller has a line number of 500 lines / inch, a BCM value of 4.0, and a verified BCM value of only 3.4; a new anilox roll has a line number of 600 lines / Inch, BCM value is 3.5. If you compare the same amount of ink transfer between the two, the color of the product printed by the old anilox roller is not lighter than that of the new anilox roller. This is because the cell surface area of the anilox roller with a line number of 500 lines / inch (with less anilox walls) is larger than that of an anilox roller with a line number of 600 lines / inch, so that the contact area between the ink and the printing plate is larger. And the anilox roller with a line number of 500 lines / inch and a BCM value of 3.4 has a smaller cell opening ratio, and its ink transfer rate is naturally greater than 600 lines / inch and an anilox roller with a BCM value of 3.5. The relationship between the anilox roller with the same number of lines and different BCM values and the color density of the print can be seen: the color density of the anilox roller of 1000 lines / inch can reach 1.7, but the minimum color density of the anilox roller of 800 lines / inch is only 1.5. The BCM is 2, the minimum color density of the Mark Andy small diameter anilox roller is 1.5, the color density of the Comco large diameter anilox roller can reach 1.7; the color density of the Comco large diameter anilox roller at the BCM value of 1.8 can reach 1.8 The color density is larger than that when the BCM value is 2.0, the reason is that the anilox roll transfer rate is different.

Even if it is the same anilox roller, when printing different substrates, its ink transfer rate is also somewhat different. Generally, the ink transfer rate of printed paper substrates is 28% ～ 35%, and the ink transfer rate of printed film materials is 26% ～ 27%, the difference between the two is 5% ～ 8% The ink absorption is high, so the ink transfer rate is high. But the ink penetrates into the paper, and the amount of ink left on the surface is less, resulting in a lower color density of the printed product.

With the above verification of the B C M value of the anilox roller, it seems that the status of the anilox roller is under control, but it is not. Since the anilox roller's ink load is not equal to the ink transfer amount, for the captain, the anilox roller's ink transfer amount is what he is most concerned about. It will be the most practical verification method to print the anilox roller after verifying the BCM value under the same conditions, and measure the color density of the printed matter, and infer the new BCM value of the anilox roller from this.