Printing in summer has caused certain losses to many enterprises, so that enterprises gradually realize that the quality of printing has been affected by climate changes, resulting in reduced product quality and low yield; retort packaging will also be affected by climate. Influence, resulting in high breakage rate. So, how to control when summer comes? What should pay attention to, to introduce:
1. Control of temperature, humidity and dryness
Because the temperature rises and exceeds the printing adaptation temperature required for printing, dry plates, blocked plates, and no color printing normally occur during printing; especially the shallow screen part is more difficult to grasp, resulting in waste. Therefore, it is best for enterprises with conditions to install air conditioners or install water-cooled air intake and exhaust systems to control the workshop temperature not to be too high. It is best to control it between 30-35 °C. In summer:
First, the humidity is too low to meet the requirements of printing humidity, which will also cause poor quality of printed products, and will increase the amount of charge generated by static electricity, which will affect the quality. Conditional enterprises have installed humidifiers because of low humidity. Unconditional enterprises should arrange for special personnel to regularly mop the floor with a damp cloth to increase humidity and improve printing adaptability.
The second is that due to rain and fog, excessive humidity will also cause losses to printing, especially for surface printing bags. Because of high humidity and high temperature, plastic films and printing inks absorb moisture, which will cause incomplete printing (fake dry). It will cause primary adhesion, secondary adhesion, fading, discoloration and penetration, transfer and other phenomena. Poor composite strength, delamination, peeling and other phenomena during lamination packaging, resulting in waste products. Nylon film for retort packaging bags is easy to delaminate and has a high breakage rate. It cannot be vacuumed, because the biggest disadvantage of nylon film is easy to absorb moisture, resulting in performance degradation. In severe cases, it may be stretched and deformed during printing, and overprinting may be inaccurate. Whether printing ink is printed on the surface, printed on the inside, or other types, etc., it is easy to absorb moisture in the air, resulting in performance degradation that cannot meet the requirements. Therefore, qualified enterprises have installed dehumidification devices, and unconditional enterprises have also adopted dehumidification. Chemical materials, such as: lime powder, discolored silica gel and other materials to reduce humidity. A dry and wet thermometer can be hung in the workshop to control the temperature and humidity, and the printing humidity is best controlled between 55%-75%.
2. Selection of printing ink and solvent
First of all, printing companies should determine the selection of ink according to the printing performance and printing speed of their own gravure printing machines. Because the performance of each printing press is different, the printing speed is also different, and the ink standards used are also different. Like the printing plate roller, the manual plate roller is darker when making the plate, and the electronic engraving plate roller is shallower, and the quality of the two plate rollers is also incapable. comparable. Therefore, the production of ink is also divided into high-grade, mid-grade and low-grade. The quality of each grade of ink is also different, the volatilization speed is also different, the viscosity is also different, and the quality of the materials used is also different. Therefore, the selected ink standards are also different.
Secondly, enterprises should choose the ink solvent according to the requirements of undertaking packaging color printing bags, and determine whether the inner printing of the surface printing is dedicated. The use of ink to replace the inner printing ink makes the composite packaging bag have poor peeling strength, peeling, delamination and odor residue where there is ink. This phenomenon does not meet the requirements of packaging and decoration. The composite packaging bag must use the inner printing ink; the retort packaging must use the special ink and special solvent. It should be used correctly according to the method required by the ink supplier, and the solvent should be correctly selected to ensure the quality of the printed product. The best choice of solvent is to choose the solvent that meets the national standard. When printing in summer, the printing master can easily grasp the volatilization speed of various solvents, which is easy to adjust. The printing master must master it, otherwise, it is easy to cause peculiar smell or fake dry phenomenon, so that the product quality cannot meet the requirements. At present, most of the leading markets use general-purpose polyester inks. Solvents commonly used in printing are: isopropyl alcohol, n-propyl ester, n-butyl ester, ethyl acetate, etc., which are called alcohol esters. If the substrate is polyester film (PET), nylon film (PA), aluminum platinum (AL), etc., special ink and special solvent must also be used.
3. Quality control of printing
1. Check the quality of the rolls in advance. Because the rolls are prone to many problems in summer.
2, Check the quality of the printing rubber roller in advance. Because of the high temperature in summer, the rubber of the rubber roller is prone to change and poor elasticity. To keep the rubber roller clean, the hardness of the two ends and the middle part should be between one and two degrees.
3. Control the working viscosity and volatilization speed of the ink, pay attention to the color change of the ink.
4. Control the knife line and knife wire.
5. Adjustment of solvent evaporation rate.
6. Control of oven temperature. Adjust oven temperature and air volume. The oven temperature is generally at a printing speed of 100m/min, and the oven temperature should be controlled at 45-55°C for BOPP, PET, PE, CPP, and 50-60°C for BOPA. White ink, gold ink and silver ink should be at 60-65℃. Control solvent residues.
7, Control the concentration of white ink, do not affect the composite strength if the viscosity is too low.
