How Does the Printing Machine work?–CTP publishing and four-color printing machine workflow.
1. CTP and film
Designers should have the most contact with printing. Small office printers can directly output data from the computer to the printer, and the printer can directly print graphics and text on paper.
But traditional printing is different. It belongs to plate printing. As the name suggests, it needs to make a computer design draft before printing,such as paper box, paper bag, tissue paper.etc.
The film that you may have heard of before is to print a computer manuscript on a transparent plastic film and then print it out. But now basically the computer manuscript is output directly to the CTP plate (we can imagine the CTP printing plate as a large and thin metal plate), waiting for printing on the machine.
2. Ink and water are not compatible
Traditional offset printing uses the principle of incompatibility between ink and water. To put it simply, the graphic content is separated from the blank part on the CTP plate through a special coating, so that the graphic part is ink-friendly, and the blank part has only water and no ink.
In this way, the CTP printing plate achieves that only the graphic part has ink.
3. Principle of Offset Printing
We use a sketch to get a rough idea of the printing process.
Figure 1. In a set of printing process, there are three cylinders in contact with each other: printing plate cylinder, blanket cylinder, impression cylinder.
Plate cylinder: Install the CTP plate on this cylinder, and then evenly apply ink and water. According to the above-mentioned principle of incompatible ink and water, only the graphic part has ink;
Rubber Cylinder: If the ink on the metal printing plate is directly transferred to the paper, long-term friction and the metal plate will be too hard, and the printing plate will wear out. At this time, we first transfer the graphics and text on the printing plate to a certain elastic blanket;
Impression cylinder: It is matched with the blanket cylinder. According to different paper thickness and paper texture, the gap between the blanket cylinder and the paper is appropriately adjusted. The paper is output from the middle of the two, so that the ink on the rubber is transferred to the paper more evenly.
Figure 1
4. Color printing process
Through Figure 1 above, we know how the ink is transferred to the paper through the printing plate. Let’s take a look at a four-color printing machine, the complete color printing process.
As shown in Figure 2, a general four-color machine will have four units. We have marked K, M, C, and Y respectively, and one color ink will be poured into the top of each unit;
Figure 2
Through Figure 1 we briefly explained the principle of printing, then the four-color machine has four units with the same configuration, printing one of CMYK colors separately;
The blank paper starts from the right, enters the four-color unit in turn, and comes out from the left to complete the printing of four colors (CMYK).
The paper passes through four units and prints in four colors in sequence, superimposed on each other in the same position, and the color printing process is completed.
5. Summary
1). We know that color printing is a variety of colors formed by using CMYK four-color inks through hanging screens and colors;
2).The CTP printing plate is to divide the design draft into 4 printing plates of CMYK four colors, and express the shade of each color through the size of the dots and omissions;
3). The printing plate is installed on the four units of the printing press, and the graphic content on the printing plate is printed on the paper through ink, and the four-color ink is superimposed to form a colorful effect;
4). If there are other spot colors to be printed (such as special gold, special silver, etc.), you can choose a five-color machine, that is, an additional unit is used to print this spot color.
