Discussion on Printing Technology of Metal Sheets

In order to compete with other packaging materials in terms of production cost and efficiency, the metal packaging industry, such as the metal thin-plate color printing process for coating, printing, and drying of metal sheets or metal cans, has been increasing the number of individual processes. The speed of production and the time taken for job transfer to improve production capacity and efficiency. However, with the reduction of individual production time, the use of larger and thinner metal sheets has increased the difficulty of implementing improved production efficiency, and the time for job transfer has gradually become a key point for improving production efficiency.
It is understood that today's manufacturers have high requirements for high-efficiency color printing production lines. They expect to print 8,000 sheets per hour, and can print color on all currently used and about-used sheet thicknesses, ie, 0.12 to 0.6 mm sheets. And achieve higher quality requirements. In fact, currently there are color printing lines in the market that can meet these requirements, but the maximum production capacity and the best color quality of the equipment must be used. The manufacturer must have a detailed understanding of the various process steps and parameters of color printing. In this paper, the sub-division of the coating, printing, and drying art of the color printing process will allow the manufacturer to understand the overall production efficiency of the metal color printing from various fine processing steps.
Coating process coating process can be subdivided into the following steps:
Metal sheet feeding;
· Transmission and recording of thin metal sheets;
· Thin metal coating;
·Conveyed to air dry system.
The parameters that affect these coating steps include:
The quality of metal sheet, such as size, thickness, surface ripple, bending degree, etc.;
·The quality of the coating, such as solids content, viscosity, service life, solvent type, etc.;
· Environmental parameters, including temperature, humidity, etc.;
Roller coating machines, such as coated designs, roller structures, and the like.
By controlling the key points of each process, coupled with high-speed roller coating equipment, it is feasible to achieve the goal of producing 8,000 sheets per hour.
Printing process The printing process of metal sheet can be mainly divided into the following steps:
· Transmission and recording of thin metal sheets;
· Determine the quality of the printed board image;
Transfer the image from the printing plate to the metal sheet;
• Transfer the metal sheet to the rotating grid or to the next processing device;
· Air-drying treatment (using ultraviolet and infrared air-drying system).
Similarly, manufacturers must know the parameters that affect the above production steps, including:
·Intensity, color tone, viscosity, etc. of the ink;
Roller size, knot strut hardness, etc.;
· Types of wetting agents and solution temperature, pH, and fluidity;
· The quality of the print, such as the spread of the image, the density and size of the dots, etc.;
· Printed board quality, such as exposure, development, paint and other effects;
The quality of the metal sheet, such as size, thickness, surface ripple, bending degree, etc.;
Roller surface characteristics, including rubber type, thickness, compressibility or incompressibility, mold release, etc.;
· Environmental parameters, including temperature and humidity;
· The ability of the embossing machine to handle the deviation of the sheet;
• The design, reliability, and maintenance of the press.
In order to achieve reliable printing, the effective control of these parameters is very important. In addition, if the Right First Time Approach can be implemented, the time for job transfer can be reduced, and printing can be performed with higher production speeds and fewer failures. All this means that the entire production process can achieve high efficiency and a shorter return on investment.
The drying process after the drying process can be roughly divided into the following steps:
· Transportation, including loading, unloading and stacking;
• Heat treatment, including providing a constant temperature during heating and baking;
· Metal sheet cooling;
Exhaust gas purification;
• Sheet output.
The parameters that will affect the above drying process are listed below:
· Heat source quality, such as the composition of gas and fuel oil, calorific value, and the constancy of supply;
· Conveyor devices, including the type and lubrication properties of the conveyor belt;
Environmental parameters such as temperature, humidity, dust, etc.
·Design and specifications of drying furnaces, including length, air volume, type of air circulation, incinerator, etc.;
·Maintenance.
In addition to using traditional drying techniques, ultraviolet and infrared air-drying devices can also be used instead. On the other hand, a uniquely designed exhaust gas purification system not only removes volatile organic compounds (VOCs) from exhaust gas, but also reduces energy costs through high-tech heat recovery systems.
It is worth mentioning that to make the entire production system highly efficient, individual good components and systems are indispensable, and it is important to connect the various units so that the entire production process can operate smoothly to ensure the overall quality of the production line. Production capacity remains at its peak. Therefore, manufacturers must thoroughly understand the operating characteristics of the production line in order to effectively increase their own production capacity. (Zheng Wu)
Excerpted from China Packaging Yearbook 1999