Multi-function crosshair
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Usually, when printing a school edition of two or more colors, it is based on whether the crosshair is registered. In addition, whether the front and back images of the printed sheet are aligned or not, and the cutting position of the paper are also judged based on the crosshair. So far, the function of the crosshair is very simple, but it is very important for multi-color printing plates that require registration.
Multi-function crosshairs, as the name implies, not only the school version registers a function, but indeed this crosshair can also be used for color management. According to the message of the crosshair, not only the deviation of the position of the printing plate can be measured, but also the density of the ink, the strength of the rolling pressure and the balance state of the left and right sides of the roller can be known after measuring the line width of CMYK, and the line width and the line are observed. The degree of deviation can be informed of the ink, dampening water, and blanket.
The emergence of the multi-function crosshair is not the result of special research and development after the project was established as one might imagine. On the contrary, it was developed in a rather accidental but inevitable situation.
Platemaking and printing are two different departments. Therefore, when there is a problem with the registration, and the problem does not know where it is, one party will complain that the plate is not ready, and the other party will complain about printing problems. This is a contradiction between the plate making department and the printing department, and the plate-making company and the printing company will never finish.
Tokyo Shinkawa Japan Flat Plate Equipment Co., Ltd. is a professional plate-making company. When working in photo-engraving, it is often difficult to understand the crosshairs that are precisely made during plate making. Why is it that the crosshairs on the machine are not allowed? The company also began to introduce printing equipment when it changed from photo-engraving to CTP plate-making. Until then, the plate-makers knew that the stretching of the paper in the printing and the lining of the drum could lead to various problems in printing such as poor registration. To solve these problems, the company set out to develop the cross-line measuring instrument Tri-PMC (PrintMarginCheker).
The Tri-PMC is read by a CCD micro camera as a crosshair of the image, and the software displays an image measurement chart and a small printer output measurement result.
The device is used for measuring the line width of the crosshair, the difference of the CMY versions based on the K plate, and the brightness of each color ink.
Fig. 1 is an enlarged view of a cross line having a line width of 50 μm, and it can be seen that the shape is more complicated than a normal cross line. In fact, development is the most difficult
Just the shape of the crosshair. Because it reflects both the information necessary for color management and the pleasing to the eye, the shape shown in the figure is now used.
The data in the table at the lower right corner of Figure 1 is the measurement of the line width and offset of the left cross line. It can be seen from the Y column in the figure that when K is used as a reference, the upper side is 27 μm and the left side is 3 μm. The left and right lines are 5 μm thicker than the upper and lower lines. On the printing plate, it was originally a crosshair of equal width. Why is there a difference in the printed sheet? In addition to the ink and wetting water, you should also consider whether the printing pressure is balanced or not and whether the blanket has been worn out.
Looking at Figure 2, the crosshairs around the Y version of the print are identical to the K version, but there is a deviation in the up and down direction. From this point, it can be known that this part of the paper has been stretched. In addition, it can be seen that the brightness of Y appears to be low. The reason for the lack of brightness is that there is too much water in the ink. At this time, if you put the water slightly, the brightness of Y will go up, and the curve showing the brightness in the chart will become sharper. At the same time, the amount of water supplied is small and the stretch of the paper is improved.
The state of the ink, the wetting water, and the blanket can be understood from the change of the multi-function crosshair. So it can also be said that the crosshair is a diagnostician for the health of the machine.
In the future, we will introduce the measurement data of the accumulated offset and brightness, and then automatically judge, display the response method, or based on the measurement result, the machine automatically adjusts the amount of ink and the amount of water. At the same time, the system that makes the colors are restored correctly.