Flexible packaging continues to develop rapidly. Gravure printing machines in this field must also continue to innovate and improve in order to meet the requirements of rapid development of flexible packaging. Therefore, equipment manufacturers must produce gravure printing presses with the advantages of high printing speed, high overprint accuracy, wide range of printing materials, stable operation, low noise, and easy operation.
I. Types of common gravure printing machines for flexible packaging
The types of gravure printing presses commonly used in flexible packaging are distinguished by the installation form of printing plates in the printing group, which can be divided into two types:
The first is a gravure printing machine with a shaft-mounted plate, with bearings at both ends of the plate;
The second is a shaftless gravure printing machine. The two ends of the printing plate are conical holes. The installation form is that the left and right printing shafts at both ends are tight against the printing plate.
It is distinguished by the driving form of printing plates in the printing group, and can also be divided into two types:
One is the drive shaft gravure printing machine. The power of all printing groups of the printing machine comes from a main motor. The main motor is placed in the middle of all printing groups, and then the power is transmitted to the front and rear printing group gears through the transmission shaft between the printing groups. The box is transmitted, and finally the plate is rotated by the gears in the gear box.
The second is an electronic shaft (also known as a transmission shaft-free) gravure printing machine. The printing plate of each printing group is driven by a servo motor (Figure 1, Figure 2, and Figure 3). In particular, the electronic shaft printing presses mentioned in this article are all installed in the form of shaftless plates. There are more electronic shafts with shaft-mounted versions in Europe and few in Asia, so I will not repeat them.
Classification and advantages of shaftless version
Practice has proved that the shaftless version is more convenient than the shafted version, and it seems more user-friendly. From the perspective of the transmission structure of the drive shaft and electronic shaft gravure printing machine, it can be seen that the electronic shaft has less gear transmission inherent to the drive shaft, Relatively speaking, the electronic shaft operation process is smoother and quieter than the drive shaft. In addition, the electronic shaft printing machine can print those printing materials without extension performance and perform second printing. Such orders are for the drive shaft printing machine. It is very difficult.
At present, there are basically three types of electronic shaft gravure printing machines in China:
Shown in Figure 1 is a servo motor that drives the printing plate to rotate through a first-stage timing belt deceleration transmission, which can be defined as a timing belt electronic axis.
Figure 2 shows a servo motor driven by a high-precision reducer and then driving the printing plate to rotate, which can be defined as a secondary direct-drive electronic shaft.
Figure 3 shows a servo motor that directly drives the plate to rotate, which can be defined as a direct-drive electronic axis.
This paper mainly explains the shaftless plate-engaging structure shown in Figure 3, which is driven directly by a servo motor to rotate the printing plate.
The printing group of the electronic axis gravure printing machine must have two functions of printing and registering. These two functions must be completed by a servo motor that drives the printing plate to rotate.
During the printing process, when the relative positions of the printing points of the front and back printing groups are not registered, the servo motor of the latter printing group must correct the printing position. According to the advance or lag of the printing position, the servo motor will adjust its phase to decrease. Or increase (by adjusting the angle of the printing plate to reduce or increase) to eliminate this advance or lag, the adjustment action is expressed as the servo motor reverses or forwards with respect to the original speed, and then drives the printing plate to work with the original speed. Reverse or forward.
In the normal printing process, register adjustment is very frequent, so the servo motor will frequently drive the printing plate to rotate forward or reverse. Therefore, the transmission process from the servo motor to the printing plate does not allow too much backlash. Otherwise, the purpose of register printing will not be achieved.
In the synchronous belt electronic shaft shown in Figure 1, during the transmission process from the servo motor to the printing plate, the existing links in the turning gap include key connection, the elasticity of the synchronous belt, and the gap driven by the synchronous belt. The secondary direct-drive electronics shown in Figure 2 During the transmission process of the shaft, servo motor to the printing plate, there are links in the rotation gap, such as the key connection and the rotation clearance inherent in the high-precision reducer itself. The direct-drive electronic shaft shown in Figure 3, the servo motor to the printing plate transmission In the process, the links existing in the swing gap are keyed.
From the comparison and analysis of the above three types of electronic shafts, we can draw a conclusion: In the direct-drive electronic shaft shown in Figure 3, during the transmission process from the servo motor to the printing plate, because the transmission links are the smallest, the backlash is also the smallest, so the registration efficiency and The accuracy will be the highest.
Third, the shaftless version structure of the direct drive electronic shaft
The main components of the shaftless version of the direct drive electronic shaft (see Figure 3) are:
1 Lateral correction motor; 2 Operating side plate bearing block; 3 Wall plate (frame); 4 Operating side plate axis; 5 Plates, 6 Transmission side plate bearing block; 7 Transmission side plate axis; 8 Linear guide 9 couplings; 10 servo motors; 11 servo motor mounts; 12 safety stops; 13 brackets one; 14 brackets two; 15 cylinders; 16 beams (frames).
The following is a detailed analysis of the shaftless version of this direct drive electronic shaft:
First, the left and right wall panels (item 3) and upper and lower beams (item 16), bracket one (piece 13), and bracket two (piece 14) are combined into an integrated frame, so that the shaftless version structure can have a stable operation. Bad environment
Secondly, the two parts of the operation side printing plate bearing seat and the transmission side printing plate bearing seat of the shaftless plate structure have sufficient length to support the printing plate shafts on both sides, which is a guarantee for the smooth operation of the printing plate.
When the printing press is in operation, the operating side printing plate shaft and the transmission side printing plate shaft simultaneously protrude to press the printing plate at the same time. This pressing force comes from the driving side plate cylinder, the traditional shaftless plate structure plate cylinder, the piston rod axis. It is theoretically consistent with the plate rotation centerline, and the tightening force does not generate additional torque. The direct-drive electronic shaft has no shaft mounting plate structure, because the rotation axis of the printing plate is the same as the rotation axis of the motor rotor, so the cylinder piston is installed. The axis of the lever axis cannot be consistent with the rotary axis of the printing plate. The cylinder for loading the plate must be moved to another position and the direction of the pressing force is parallel to the rotary axis of the printing plate. At this time, if a single cylinder is used for pressure, the cylinder The pressing force is opposite to the pressing force of the printing plate shaft on the operation side, and there is a distance, which will inevitably form an additional torque on the printing plate shaft on the transmission side, resulting in inconsistent forces on the printing plate shaft on both sides, thereby increasing the printing plate shaft on both sides Different axial degrees.
Under normal circumstances, such high-speed printing presses have a horizontal automatic registration function, and the horizontal automatic registration function is usually activated when the printing press is working. If these factors are combined, it may speed up the printing plate axis on both sides. Wear and tear.
To avoid this, a cylinder can be installed on each side of the rotary axis of the printing plate symmetrically. The mounting position should be such that the clamping force of the cylinders on both sides and the rotary axis of the printing plate are on the same plane, and the cylinders on both sides are pressed tightly. The position and direction of the resultant force of the force can be consistent with the rotation axis of the printing plate.
In actual application process, when the cylinders on both sides start to start, there is often an out-of-sync situation. Considering this factor, when designing the shaftless version structure of the direct-drive electronic shaft, a sufficiently long linear guide should be selected. Furthermore, the damage to the printing plate shaft caused by the asynchronous cylinders when they start is eliminated, and when the cylinders on both sides are in a normal working state (that is, the plate is pressed tightly), the pressing forces of the cylinders on both sides are already in a balanced state. No undesired additional forces on the plate axis.
Fourth, the conclusion
Based on the above-mentioned comparison and analysis, the comprehensive performance of the shaftless mounting plate structure of the direct-drive electronic shaft is higher than other plate mounting structures, which can enable the gravure printing machine to achieve high printing speed, high overprint accuracy, a wide range of printing materials, and operation. Stable, low noise, convenient operation, etc., meet the needs of the rapid development of flexible packaging.