Insufficient drying system of gravure printing machine and solutions
First, the current common gravure printing machine drying system
Most gravure printing presses currently rely on the operator to manually adjust the operating state of the drying system according to practical experience. The air intake of each unit relies on adjusting the opening of the damper to balance the wind pressure difference of each suction port, thereby adjusting the required air volume of each unit. At the same time, in the case of multi-unit parallel exhaust, it is necessary to adjust the exhaust valve to balance the wind pressure of each unit exhaust vent to achieve the exhausting requirements of several drying units. However, because the exhaust air is adjusted by multiple points and interacts with each other, the wind pressure difference between the points of the system is large, which is easy to cause the leakage of the oven exhaust gas. The smaller the circulating air volume required by the drying unit, the more difficult it is to adjust the balance. Therefore, it is necessary to increase the exhaust air volume to ensure Ovens reduce leakage, and this kind of continual adjustment is a cumbersome and difficult task to grasp. The lack of experience will lead to a more difficult situation, so production operators usually do not fine-tune in actual production. . In order to meet most of the process air volume and the improvement of its working environment, the air volume is generally adjusted to a large extent, which not only increases the heating energy consumption and the operating power of the exhaust fan, but also increases the input cost and operating cost of the subsequent exhaust gas treatment. .
In addition, for energy saving purposes, most of the drying system is equipped with a return air. When the unit printing solvent volume is large or the return air ratio is large, even if the total exhaust air volume is large, the unit exhaust air volume may be insufficient, and dry gas may appear. In the case where the solvent concentration exceeds the lower safety limit, there is a safety hazard of explosion.
In summary, the gravure printing machine manufacturers summarize the existing problems of the existing system: the system matching adjustment is difficult, the exhaust air volume is too large, the heating energy consumption is too high, there are safety hazards, and the cost of environmental protection is high.
Second, the current mainstream common solutions
In order to optimize the gravure drying system, many gravure printing press manufacturers have taken corresponding modifications.
First, let's analyze the relevant elements of gravure drying:
Purpose: To completely evaporate the solvent in the ink.
Countermeasure: Use hot air to fully contact the film surface ink for heat transfer and remove the solvent.
Objective: To ensure high speed and low energy consumption under the premise of safety and quality.
The control elements of the drying process include ink formulation, speed, temperature, air volume, safety factors, appearance, residue, energy consumption, environmental factors, oven leakage, and so many factors to balance to get a better result is very difficult For example, in order to obtain high speed, the method of lengthening the oven and changing the air nozzle to lengthen the heat and mass transfer time and efficiency, but the lengthening of the oven will bring problems such as the reduction of the overprint precision.
For existing equipment, we can analyze the assumption that the ink formulation and speed are the same:
1. The temperature is too high, causing problems such as bubbles, film deformation, and excessive energy consumption;
2, the temperature is too low, the product is not dry thoroughly, the solvent residue exceeds the standard;
3, the air volume is too large, causing problems such as film shake, ink drag, excessive energy consumption;
4. The air volume is too small, the drying is not thorough, the solvent residue exceeds the standard, and there are safety hazards.
Since the energy consumption has a great influence on the production cost, more gravure printing machine manufacturers use low-temperature and high-volume production. The advantage is that the energy consumption is properly controlled under the premise of ensuring safety and quality, and the thermal energy grade is low, and solar energy can be used. Heating pumps and other means provide heat to further reduce heating costs.