First, the arrangement of printing color sequence
There are two kinds of printing methods: surface printing and inward printing. The printing material (Teddy paper) basically uses surface printing due to its physical characteristics. Plastic film is usually printed in more ways. According to the principle of change of three primary colors and the principle of color registration (overprint), as well as the actual experience in the production process, under normal circumstances, the printing color sequence of the surface printing (from light to dark) is: white → yellow → magenta → cyan → black ink The color sequence (from dark to light) is: black → cyan → magenta → yellow → white but sometimes adjustments can be made according to the process requirements.
Second, gravure printing 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. Easy to stretch the material is difficult to overprint accurate, so the tension is generally set to a small, but the tension is too small, the material is loose, even more irregular stringing phenomenon, resulting in overprinting can not be accurate. The tension set value is based on the smallest tension that can be accurately overprinted and neatly wound. Under normal circumstances, the winding tension is slightly greater than the unwinding tension. The main purpose is to tighten the roll, close it, and flatten the end face. Avoid loosening, stringing and other phenomena unfavorable to the next process slitting. Different specifications, batches of raw paper, the tension setting value will be different, in the actual printing process control process.
Third, the steam heating temperature control
The control of the heating temperature is also determined by the nature of the printing material. There is a certain relationship between the heating temperature, the printing speed, and the volatilization rate of the flux. When the temperature is constant, if the volatilization rate of the flux is slow, the printing speed is reduced. On the contrary, the printing speed should be increased. When the volatilization rate of the flux is constant, if the printing speed is faster, the heating temperature is increased. On the contrary, the temperature can be lowered. When the printing speed is constant, if the flux volatilizes slowly, the heating temperature increases. On the contrary, the heating temperature should be reduced. In addition, the control of the heating temperature is also related to the printing process conditions, ink properties, ink thickness, and the like.
Fourth, the control of printing pressure
The printing pressure is the pressure of the printing rubber impression roller, the printing pressure is not enough, the ink transfer is not good, and the graphic defect easily occurs. Too much pressure makes it easy to imprint marks. Therefore, in general, the gravure printing machine is equipped with an electrostatic ink-absorbing roller, and the electrostatic transfer is used to assist the ink transfer, which is indispensable for the high-speed gravure printing machine. With an electrostatic ink-absorbing system, the ink can be transferred very well to the paper. Without an electrostatic ink-absorption system, the ink cannot be fully transferred. Patterns, lines, words, etc. may appear as pastes, missing prints, and unequal hue and shades. Different printing materials have different printing pressures, and there are certain requirements on the rubber hardness of the rubber roller. Generally, the hardness of rubber is slightly higher when printing plastic films. When printing tipping paper, the pressure is generally about 20 to 30Pa. In the specific production process, appropriate adjustments shall be made based on the printing effect and related factors such as ink.
The printing pressure between the printing plate roller and the rubber platen roller is obtained by adjusting the center distance between the two. The pressure causes the transfer of the ink to occur, resulting in deformation of the rubber, maintaining a certain impression width, and the impression width varies with the diameter of the two rollers, the hardness of the rubber, and the printing pressure. At the same printing pressure, the small diameter rubber roller prints well and the high hardness rubber roller prints with good quality because the resulting impression width is small.
In the actual printing, the width of the imprinting width should be comprehensively judged, that is, determined according to the types of printing materials, rubber thickness and hardness, and the width of the printed matter.
Fifth, ink viscosity adjustment and control
The accuracy and durability of the ink viscosity in the printing process is very important, especially in high-speed printing, the viscosity control of the ink is related to a series of printing failures. It is an important factor that affects the quality of printed products. When printing, the greater the ink viscosity, the worse the ink transfer effect. When the viscosity of the ink is too large, the entire ink system is in an oversaturated state, and the fluidity in the ink is poor. It's easy to get together and it's not easy to get into the rollout of the roll. If the viscosity of the ink is too small, the organic solvent content in the ink is high. The ink contains relatively few components such as resin and pigments, and does not form a smooth pellicle after drying. The ink layer is white, dull, and lacks gloss.
When gravure is printed, the viscosity of the ink must be adjusted first, and the flux is added to the ink to reduce its viscosity to a level suitable for the performance and process requirements of the printing press. The viscosity is mainly matched with the speed of the printing press. For high speed printing, try to use a low viscosity while maintaining the stability of the hue. Since the viscosity of the ink seriously affects the printing quality, the viscosity of the ink must be controlled within a suitable range during the gravure printing process. In the production process, the ink is volatilized at all times because the ink is constantly circulated, and the viscosity of the ink is detected every five minutes to control it in the normal range.
Scraper adjustment and control
Squeegee height position and front-to-rear position adjustment determines the contact position of the doctor blade and the printing plate roller, which also determines the distance between the die plate contact line and the imprinting line. The distance should be based on the printing speed, ink viscosity, and the cell site. Depth, drying speed, layout quality, printing plate diameter, etc. are adjusted, generally about 40MM. In general, the longer the distance, the greater the opportunity for ink drying in the cells, and the lower the ink transfer rate. From the point of view of printing, it is equivalent to the partial withdrawal of the ink. At the same time, the distance is a test of ink printability. When this distance is large, some inks will overflow the ink from the inside of the cell, which will affect the printing quality. On the contrary, it is advantageous to increase the ink transfer rate, but it is also prone to print defects such as dirty prints. The blade contact angle, which is the angle between the tangent of the contact point of the doctor blade and the printing plate roller and the doctor blade, is generally 30-60 degrees. Improve the contact angle, easy to scrape the layout of the ink to make the picture clear, when the ink layer may be printed, printing ink gloss and other phenomena, but also easy to damage the printing plate roller. On the contrary, when the contact angle is reduced, the printing ink layer is heavy, the gloss of the printed product is good, and the corners of the image are easily blurred. At the same time, the impurities in the ink are easily brought into the knife gap, which causes printing and processing problems such as knife cutting.
Squeegee pressure adjustment In general, the pressure applied to the platen roller by the blade is set according to need, and is usually about 20Pa. The principle of control is to reduce scraper pressure as much as possible without affecting the print quality. The greater the blade pressure, the greater the friction between the platen roller and the blade, and it is easy to damage the blade and the platen roller. The factors affecting the pressure of the squeegee include the printing speed, the accuracy of the printing roller, the quality of the squeegee itself, the viscosity of the ink, the impact of the ink on the squeegee, and the contact angle of the squeegee. Under normal circumstances, the faster the printing speed, the greater the required blade pressure.
The flatness of the scraper The leveling and warping of the scraper depends mainly on the method of installation. Of course, it may also be related to the presence of foreign matter on the tool holder groove or the doctor blade or the tablet. If the blade is not leveled, there is a possibility that the thickness of the ink layer may be different when the full-color product is printed, or the ink may not be completely clean, which may seriously affect the product quality and normal production.
In order to improve the squeegee effect, the squeegee is also periodically reciprocated along the length of the surface of the printing plate roller as the printing plate roll rotates. In this way, it is possible to reduce the wear on the locally fixed position and to avoid the accumulation of ink on the bottom of the blade. The movement of the scraper left and right reduces the knife line, improves the blade utilization, and reduces the wear of the printing plate roller.
Seventh, management of printing plate
Since the gravure printing mainly relies on the ink stored in the cylinder of the plate cylinder to transfer the printing material to the printing material to realize the printing pattern, the storage, maintenance and cleaning of the printing plate are important. The place where the plates are stored should be kept clean, ventilated and dry. Careful cleaning of the plates before and after the machine is required to prevent the accumulation of ink in the cells for a long period of time and affect the use of the plates. In particular, some fine-striped plates should be strictly observed before and after the printing to clean the plates.
There are two kinds of printing methods: surface printing and inward printing. The printing material (Teddy paper) basically uses surface printing due to its physical characteristics. Plastic film is usually printed in more ways. According to the principle of change of three primary colors and the principle of color registration (overprint), as well as the actual experience in the production process, under normal circumstances, the printing color sequence of the surface printing (from light to dark) is: white → yellow → magenta → cyan → black ink The color sequence (from dark to light) is: black → cyan → magenta → yellow → white but sometimes adjustments can be made according to the process requirements.
Second, gravure printing 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. Easy to stretch the material is difficult to overprint accurate, so the tension is generally set to a small, but the tension is too small, the material is loose, even more irregular stringing phenomenon, resulting in overprinting can not be accurate. The tension set value is based on the smallest tension that can be accurately overprinted and neatly wound. Under normal circumstances, the winding tension is slightly greater than the unwinding tension. The main purpose is to tighten the roll, close it, and flatten the end face. Avoid loosening, stringing and other phenomena unfavorable to the next process slitting. Different specifications, batches of raw paper, the tension setting value will be different, in the actual printing process control process.
Third, the steam heating temperature control
The control of the heating temperature is also determined by the nature of the printing material. There is a certain relationship between the heating temperature, the printing speed, and the volatilization rate of the flux. When the temperature is constant, if the volatilization rate of the flux is slow, the printing speed is reduced. On the contrary, the printing speed should be increased. When the volatilization rate of the flux is constant, if the printing speed is faster, the heating temperature is increased. On the contrary, the temperature can be lowered. When the printing speed is constant, if the flux volatilizes slowly, the heating temperature increases. On the contrary, the heating temperature should be reduced. In addition, the control of the heating temperature is also related to the printing process conditions, ink properties, ink thickness, and the like.
Fourth, the control of printing pressure
The printing pressure is the pressure of the printing rubber impression roller, the printing pressure is not enough, the ink transfer is not good, and the graphic defect easily occurs. Too much pressure makes it easy to imprint marks. Therefore, in general, the gravure printing machine is equipped with an electrostatic ink-absorbing roller, and the electrostatic transfer is used to assist the ink transfer, which is indispensable for the high-speed gravure printing machine. With an electrostatic ink-absorbing system, the ink can be transferred very well to the paper. Without an electrostatic ink-absorption system, the ink cannot be fully transferred. Patterns, lines, words, etc. may appear as pastes, missing prints, and unequal hue and shades. Different printing materials have different printing pressures, and there are certain requirements on the rubber hardness of the rubber roller. Generally, the hardness of rubber is slightly higher when printing plastic films. When printing tipping paper, the pressure is generally about 20 to 30Pa. In the specific production process, appropriate adjustments shall be made based on the printing effect and related factors such as ink.
The printing pressure between the printing plate roller and the rubber platen roller is obtained by adjusting the center distance between the two. The pressure causes the transfer of the ink to occur, resulting in deformation of the rubber, maintaining a certain impression width, and the impression width varies with the diameter of the two rollers, the hardness of the rubber, and the printing pressure. At the same printing pressure, the small diameter rubber roller prints well and the high hardness rubber roller prints with good quality because the resulting impression width is small.
In the actual printing, the width of the imprinting width should be comprehensively judged, that is, determined according to the types of printing materials, rubber thickness and hardness, and the width of the printed matter.
Fifth, ink viscosity adjustment and control
The accuracy and durability of the ink viscosity in the printing process is very important, especially in high-speed printing, the viscosity control of the ink is related to a series of printing failures. It is an important factor that affects the quality of printed products. When printing, the greater the ink viscosity, the worse the ink transfer effect. When the viscosity of the ink is too large, the entire ink system is in an oversaturated state, and the fluidity in the ink is poor. It's easy to get together and it's not easy to get into the rollout of the roll. If the viscosity of the ink is too small, the organic solvent content in the ink is high. The ink contains relatively few components such as resin and pigments, and does not form a smooth pellicle after drying. The ink layer is white, dull, and lacks gloss.
When gravure is printed, the viscosity of the ink must be adjusted first, and the flux is added to the ink to reduce its viscosity to a level suitable for the performance and process requirements of the printing press. The viscosity is mainly matched with the speed of the printing press. For high speed printing, try to use a low viscosity while maintaining the stability of the hue. Since the viscosity of the ink seriously affects the printing quality, the viscosity of the ink must be controlled within a suitable range during the gravure printing process. In the production process, the ink is volatilized at all times because the ink is constantly circulated, and the viscosity of the ink is detected every five minutes to control it in the normal range.
Scraper adjustment and control
Squeegee height position and front-to-rear position adjustment determines the contact position of the doctor blade and the printing plate roller, which also determines the distance between the die plate contact line and the imprinting line. The distance should be based on the printing speed, ink viscosity, and the cell site. Depth, drying speed, layout quality, printing plate diameter, etc. are adjusted, generally about 40MM. In general, the longer the distance, the greater the opportunity for ink drying in the cells, and the lower the ink transfer rate. From the point of view of printing, it is equivalent to the partial withdrawal of the ink. At the same time, the distance is a test of ink printability. When this distance is large, some inks will overflow the ink from the inside of the cell, which will affect the printing quality. On the contrary, it is advantageous to increase the ink transfer rate, but it is also prone to print defects such as dirty prints. The blade contact angle, which is the angle between the tangent of the contact point of the doctor blade and the printing plate roller and the doctor blade, is generally 30-60 degrees. Improve the contact angle, easy to scrape the layout of the ink to make the picture clear, when the ink layer may be printed, printing ink gloss and other phenomena, but also easy to damage the printing plate roller. On the contrary, when the contact angle is reduced, the printing ink layer is heavy, the gloss of the printed product is good, and the corners of the image are easily blurred. At the same time, the impurities in the ink are easily brought into the knife gap, which causes printing and processing problems such as knife cutting.
Squeegee pressure adjustment In general, the pressure applied to the platen roller by the blade is set according to need, and is usually about 20Pa. The principle of control is to reduce scraper pressure as much as possible without affecting the print quality. The greater the blade pressure, the greater the friction between the platen roller and the blade, and it is easy to damage the blade and the platen roller. The factors affecting the pressure of the squeegee include the printing speed, the accuracy of the printing roller, the quality of the squeegee itself, the viscosity of the ink, the impact of the ink on the squeegee, and the contact angle of the squeegee. Under normal circumstances, the faster the printing speed, the greater the required blade pressure.
The flatness of the scraper The leveling and warping of the scraper depends mainly on the method of installation. Of course, it may also be related to the presence of foreign matter on the tool holder groove or the doctor blade or the tablet. If the blade is not leveled, there is a possibility that the thickness of the ink layer may be different when the full-color product is printed, or the ink may not be completely clean, which may seriously affect the product quality and normal production.
In order to improve the squeegee effect, the squeegee is also periodically reciprocated along the length of the surface of the printing plate roller as the printing plate roll rotates. In this way, it is possible to reduce the wear on the locally fixed position and to avoid the accumulation of ink on the bottom of the blade. The movement of the scraper left and right reduces the knife line, improves the blade utilization, and reduces the wear of the printing plate roller.
Seventh, management of printing plate
Since the gravure printing mainly relies on the ink stored in the cylinder of the plate cylinder to transfer the printing material to the printing material to realize the printing pattern, the storage, maintenance and cleaning of the printing plate are important. The place where the plates are stored should be kept clean, ventilated and dry. Careful cleaning of the plates before and after the machine is required to prevent the accumulation of ink in the cells for a long period of time and affect the use of the plates. In particular, some fine-striped plates should be strictly observed before and after the printing to clean the plates.
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