The topic that I said today is a bit old, but very common. In the past, the ability of gravure technicians relied on tempering and accumulating in production, with limited experience and shallowness. In an era of rapid change in this era, if you do not speed up your promotion, you will be eliminated by the times, so this article, whether for the old staff or the new rookie, can take a lot of detours.
Printing color sequence
Generally, there are two printing methods: printing and printing. The printing material (tip paper) basically uses the surface printing because of its physical characteristics. Plastic films are usually used in more ways. According to the variation law of the three primary colors and the principle of color registration (overprinting) and the actual experience in the production process, the printing color sequence of the following table (from light to dark) is: white → yellow → magenta → cyan → black The printing color sequence (from dark to light) is: black → cyan → magenta → yellow → white but sometimes it can be adjusted according to the process requirements.
Gravure tension control
Printing tension is an important process parameter of the printing process, and its tension system is also the core mechanism of the entire printing equipment . The setting of printing tension is determined according to the nature of the printing material. The material that is easy to stretch is difficult to overprint accurately, so the tension is generally set to be small, but the tension is too small, the material is slack, and irregular stringing phenomenon occurs, resulting in inaccurate overprinting. The tension setting value is based on the minimum tension that can be overprinted accurately and the winding is neat. Under normal circumstances, the winding tension is slightly larger than the unwinding tension, and the main purpose is to tighten the volume, compact and flatten the end face. Avoid the phenomenon of loose rolls, string rolls, etc., which is not conducive to the next process. For the different sizes and batches of base paper, the tension setting values ​​will be different, and the process control will be carried out during the actual printing process.
Printing pressure control
The printing pressure is the pressure of the printing rubber embossing roller, the printing pressure is not enough, the ink transfer is not good, and the graphic defect is prone to occur. Too much pressure makes it easy to emboss marks. Therefore, the general gravure printing machine is equipped with an electrostatic ink absorption roller, which uses electrostatic electricity to help the ink transfer, which is indispensable for the high speed gravure printing machine. Through the electrostatic ink absorption system, the ink can be transferred very well to the paper. Without the electrostatic ink absorption system, the ink can not be fully transferred, and patterns, lines, texts, etc. may appear to be smeared, missed, and uneven in hue and shade.
Different printing materials have different printing pressures, and have certain requirements on the rubber hardness of the rubber pressure roller. Generally, the rubber hardness requirement is slightly higher when printing a plastic film. When printing the tipping paper, the pressure is generally about 20 to 30 Pa. In the specific production process, appropriate adjustments should be made according to the printing effect and related factors such as ink. The magnitude of the printing pressure between the printing plate roll and the rubber embossing roll is obtained by adjusting the center distance between the two. The pressure causes the transfer of the ink to be generated, resulting in deformation of the rubber, maintaining a certain embossing width, and the embossing width varies depending on the diameter of the two rolls, the hardness of the rubber, and the printing pressure. Under the same printing pressure, the rubber roller with small diameter has good printing quality, and the roller with high rubber hardness has good printing quality because the obtained embossing width is small. In actual printing, the size of the embossing width should be comprehensively judged, that is, according to factors such as the type of printing material, the thickness and hardness of the rubber, and the width of the printed matter.
Ink viscosity adjustment and control
The accuracy and persistence of ink viscosity during printing is important, especially in high speed printing where the viscosity control of the ink is associated with a range of printing failures. It is an important factor affecting the quality of printed products. At the time of printing, the greater the viscosity of the ink, the worse the effect of ink transfer. When the viscosity of the ink is too large, the entire ink system is in a supersaturated state, and the fluidity in the ink is poor. It is easy to get together and it is not easy to smoothly enter the cell of the publication roll. If the viscosity of the ink is too small, the amount of organic flux in the ink is large. The resin, pigment and other components in the ink are relatively small, and cannot form a smooth film after drying, and the ink layer is white, dull, and lacks luster.
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