Gravure Printing Technology

First, the main difference between engraving gravure and corrosion gravure According to the gravure printing plate production process, the printing plate can be divided into etching gravure gravure gravure.
1. The engraving engraving gravure and etching gravure processing engraving gravure processing is the use of electric engraving machine, with different angle needles, after the copper plated gravure roller strikes to form different depths of V-shaped groove, and then plated on the gravure cylinder surface The wear-resistant chromium layer, after polishing, can be made into a printing plate on the machine. During the printing process, the V-shaped grooves are used to transfer the ink onto the printing material.
Corrosion gravure is the use of imaging technology, in the copper plating gravure cylinder surface image, after corrosion, the surface of the drum U-shaped groove, and then chrome plating and surface polishing.
2. The difference between the engraving engraving and the gravure gravure engraving engraving gravure and the erosion gravure is not significant, but the service life of the gravure gravure and the gravure gravitational gravure has a big difference.
After the V-groove on the surface of the engraving gravure is worn, the depth of the groove becomes shallow. As the width of the bottom of the V-shaped groove becomes narrower, the area of ​​the halftone dot becomes smaller, the ink amount of the groove gradually decreases, the ink color becomes shallow quickly, and the printing plate is scrapped. . Engraving gravure in the process of engraving if the depth control is not good, it will affect the quality of printing, too deep in the printing process is likely to cause ghosting; too shallow will affect the life of the printing plate.
The corrosion plate surface is a U-shaped groove. With the wear of the printing plate, the depth of the groove becomes shallow, but the area of ​​the dot is not changed, and the decrease of the ink amount is relatively slow, and there is no significant change in the printing color. Its long service life.
At present, the domestic intaglio manufacturers use electric engraving plates. Corrosion gravure is mainly produced by foreign manufacturers, and the price is relatively high.
Second, the composition of the gravure printing machine The gravure printing machine mainly consists of the uncoiling machine, the guiding group, the printing group, the cutting group and the control group. The unwinding machine mainly completes the unwinding of the web under a certain speed and tension, and maintains a corresponding stable state, and simultaneously completes automatic or manual splicing of the web. The main function of the guide group is to ensure that the paper web is not offset laterally during the printing process, and at the same time, the paper tension is stable. The printing group is the main component of the gravure printing machine. The main processes for printing are ink supply, printing and drying. The slitting group will print the entire printed semi-finished product and cut it into a molded sheet product. The control group mainly sets the operating parameters and working conditions of the gravure printing machine, including the speed, tension, temperature, and the working status of the pressure roller, the squeegee, and the ink pump.
Third, the principle of winding machine and operation Unwinding machine is mainly composed of clutch, tension roller and tension controller. The three form a closed-loop automatic control system for automatically adjusting the speed and tension of web unrolling.
1. Working principle The unwinding machine is a driven device with no power. It mainly adjusts the supply of paper according to the need of the printing unit to feed the paper (paper pulls the rotation speed of the web). The control of the web rotation speed is achieved through the clutch and the paper spool. Most of the previous use of electromagnetic clutch, the current use of large and colorful pneumatic clutch.
In the printing process, the printing speed is not a constant value, sometimes gradually increasing, sometimes decreasing gradually, so the tension roller is needed to control the paper supply and tension.
The tension roller swings up and down around a fixed point. The thrust of the cylinder and the tension of the paper are balanced to ensure that the tension roller is in equilibrium. The position of the tension roller indicates the tension of the paper and the amount of paper supply, and the position information is input to the tension and the paper supply speed. During the printing process, the smaller the distance between the tension roller and the floating roller, the more conducive to the stability of the paper tension.
The tension controller is a key component in the tension control system of the uncoiler. It mainly completes the processing and analysis of detection signals and issues execution commands. At present, MCS-202E controllers are mainly used in China. The controller can indicate the working state of the brake disc using the clutch paper reel and set or correct the position of the tension roller at any time.
2. Operation of uncoiler According to the requirements of frontier printing, the gravure printing machine generally uses the order roll paper. Due to the different machine models, the outer diameter of the uncoiler paper mandrel is relatively different, typically 3, 6 or 12 inches. Therefore, when ordering a web, first consider the outer diameter of the mandrel. Generally, the inner diameter of the web should be 2 to 5 mm greater than the axis of the paper mandrel. Secondly, it should also be noted that the largest web that can be used by the unwinder Outer diameter, if the outer diameter of the web exceeds this range, it cannot be installed and used.
During installation, the paper core should be inspected for deformation. If the deformation is too great, it should be repaired. After the paper is unfolded and straightened, insert the paper core into the paper roll core, and then check the distance between the two ends of the paper core shaft to center the roll paper as far as possible.
After the roll paper machine, make sure that the horizontal position is in the same position as the roll paper. If the uncoiler is automatically tying paper, it should be docked or overlapped according to the requirements of the uncoiler. When splicing, first scribe at the splicing position, and then use double-sided and single-sided adhesive tape for pasting. During the splicing process, it must be ensured that the outer diametral line speeds of the two rolls are consistent.
If the uncoiler is manually picking up the paper, the roll-up web will be cut after stopping, and the horizontal position of the paper will be adjusted and it will be directly attached to the beginning of the new web.
Fourth, the adjustment of the lateral position of the paper in the printing process The so-called horizontal adjustment is to adjust the position of the paper along the axial direction of the printing plate. This is very different from the lateral registration of the pattern at the time of printing. It is generally divided into three parts: unwinding machine adjustment, printing before printing and before slitting.
1. Uncoiler adjustment The installation of the web on the decoiler is generally centered. However, when the pattern of the plate is skewed to one side, the lateral position of the web must be adjusted. This adjustment is generally performed manually at one time.
2. Adjustment before printing This is the main work in the horizontal adjustment, which is done automatically by the guidance group. The cylinder pushes the drive roller to swing around a fixed point to adjust the relative position of the drive roller. The dashed line is the width of the paper and the arrow is the direction of paper movement. In the process of use, the lateral position of the photoelectric detection switches on both sides is first set according to the position of the position of the printing plate pattern on the lateral position of the paper. This forms a closed-loop control system that guides the controller to control the lateral position of the paper. The system has high control accuracy and can reach (+-) 0.15 mm. In addition, it can also perform single-sided or double-sided control.
3. Adjust before slitting To ensure that the slitter is cut to the horizontal tangent position, the lateral position of the paper needs to be adjusted. This position generally adopts the same closed-loop control system as before printing, and also needs to set the position of the photodetector in advance.
Fifth, the control method and principle of the tension of the gravure printing machine 1. The division of the tension zone The tension zone of the gravure press can be divided into three zones: the unwinding tension zone, the printing tension zone and the slitting tension zone. The unwinding tension zone includes the tension control between the web paper mandrel and the paper feeding roller in the guide group; the printing tension zone includes the tension control between the paper feeding roller in the guide set and the paper roller in the printing set; The printing group puts the paper roll into slitting tension zone between slitting tension rollers. For gravure printers without a slitting group and only a rewinding group, the slitting tension zone includes the area from the paper roll to the rewind.
2. The control principle of the tension zone The tension control of the unwinding tension zone is mainly done by the uncoiler. Tension control is a main function of the unwinding machine, so the control principle of the tension zone is the same as the working principle of the unwinding machine, and a closed-loop control system is composed of a clutch, a tension roller and a tension controller.
The printing tension zone is an important part of the tension control system of the gravure printing machine, and it is the key to ensure the accuracy of printing registration. The tension control of the tension zone adopts the differential principle, and the system adjusts the tension of the paper by controlling the running speed of the paper feeding roller and the paper roller. At present, most of the gravure printing press rolls are synchronized with the running speed of the printing press. The paper roll end is connected with the stepping motor to achieve differential speed control.
The tension control in the slitting tension zone is also very important. If the slitting accuracy is not achieved due to the unstable tension, the waste will be rejected. For this reason, the tension zone generally adopts the same control method as the printing tension zone. The basic speed is the running speed of the printing group and the paper roll. The shaft end of the paper roll of the slitting group is connected with the stepping motor to realize the differential speed control.