1. The adhesion fastness of imprints on the film is poor, and it is not resistant to rubbing and friction
Causes and handling suggestions:
(1) PE or PP film without surface treatment or with unsatisfactory surface treatment effect, resulting in a surface tension of less than (3.6-3.8) × 10-2N/m. Use a surface tension measuring solution to detect the surface tension of the film. If the requirements are not met, the surface should be re treated.
(2) Excessive dilution of the ink, damage to the adhesive, or misuse of the diluent. The correct choice of diluent and the viscosity of the ink during dilution should be controlled within 25-35 seconds.
(3) The ink itself has poor adhesion fastness to the film. Change the type of ink or negotiate with the ink manufacturer for resolution.
2. Stacker plate
Causes and handling suggestions:
(1) If there are impurities in the ink, it should be filtered or replaced with new ink.
(2) The ink is thick, and a certain amount of diluent can be added to adjust the viscosity of the ink to a suitable value of 25-35 seconds.
(3) Ink dries too quickly. Add an appropriate amount of slow drying diluent to reduce the drying speed of the ink.
3. Pattern color change
Causes and handling suggestions:
(1) The viscosity of the ink changes. When diluting ink, it should be stirred while adding to allow the ink to fully dissolve in the solvent and control the desired viscosity. If possible, a mechanical circulation pump can be added for better results.
(2) After using the ink for a period of time, adding a diluent reduces the ink concentration. Thinner should be added every 30 minutes or so, and after 2-3 diluents are added, a portion of the original ink should be added and stirred evenly to avoid a decrease in ink concentration.
4. Mixed color
Mixing refers to the contamination of the color of the previous ink or the diffusion and migration of colors by the subsequent ink.
Causes and handling suggestions:
(1) The previous color ink dries too slowly, or the latter color ink dries too quickly. Use appropriate solvents according to the specific situation (the previous color of ink must be thoroughly dried), or adjust the temperature of the heating system for each part.
(2) Ink viscosity is on the high side. Reduce ink viscosity appropriately.
(3) Affected by the plasticizer inside the substrate film. Understand the types and precautions of film plasticizers, and replace the film if it is not suitable.
(4) Improper use of pigments and dyes in ink can cause migration. The use of inks made from dyes should be avoided as much as possible.
5. Printed matter rewinding adhesion
Causes and handling suggestions:
(1) The drying speed of the ink is slow, and there are more residual solvents in the printed matter. Adjust the drying speed of the ink by adding a fast drying diluent or increasing the drying temperature to minimize solvent residue.
(2) If the rewinding tension is too high, it should be appropriately reduced.
(3) The temperature and humidity of the air during rewinding are relatively high.
(4) The drying temperature is too high, resulting in the surface temperature of the film being too high, and the accumulated heat cannot be diffused in a timely manner during rewinding, or the cooling process is short, resulting in insufficient film cooling. The drying temperature should not be set too high or the cooling time should be extended.
6. Hairy edges on the pattern, irregular flash around the imprint
Causes and handling suggestions:
(1) The pressure between the ink roller and the printing plate is not appropriate, usually due to excessive pressure. The pressure between the two should be adjusted appropriately.
(2) The ink has dried on the printing plate or Anilox. Add a slow drying diluent to the ink or cover the ink tank to reduce the evaporation of solvents in the ink.
(3) The ink is too thick. Control the ink viscosity within 25-35 seconds, or flexibly control the ink viscosity according to the printing situation.
(4) Due to the influence of static electricity, there are burrs and burrs on the edge of the imprint. Install an electrostatic eliminator, or add an appropriate amount of Antistatic agent to the ink.