1.What problems exist with the substrate and pretreatment? How can they be solved?
Problem: Residual grease, moisture, dust, or watermarks from pretreatment (chemical conversion) and passivation solution residue on the substrate surface violently vaporize during baking, breaking through the coating.
Solution:
Ensure the cleaning and pretreatment equipment is operating normally, and that the spray pressure, concentration, and temperature meet specifications.
Check the condition of the squeeze rollers to ensure the substrate is completely dry and clean before entering the coating machine.
Monitor the substrate temperature to prevent condensation on the surface due to excessively low board temperature.
2.What problems are there with coatings and painting? How can they be solved?
Problems:
Coating Inherent Issues: Air bubbles formed during production, transportation, and circulation of the coating are not completely eliminated; the coating is contaminated with water, oil, or other incompatible substances.
Application Issues: The coating viscosity is too high, making it difficult for air bubbles to dissipate; the speed ratio between the coating roller and the pickup roller is improperly set, trapping air between the rollers.
Solutions:
Before applying the coating, allow it to settle sufficiently to defoam. Maintain a stable circulation system and avoid vigorous agitation that introduces air.
Strictly manage the coating to prevent contamination. Inspect and filter the coating.
Optimize the coating viscosity and adjust the appropriate roller speed ratio and roller pressure.
3.What problems are there with the curing process? How can they be solved?
Problem: Improper oven curing profile settings, especially excessively high temperatures in the preheating (or pre-curing) zone, cause rapid skin formation on the coating surface. Internal solvents, moisture, or air expand due to heat and cannot escape, resulting in pinholes.
Solution:
Adjust the curing profile: Appropriately lower the temperature at the oven inlet and extend the leveling and flash evaporation time in the low-temperature zone to allow solvents and gases to escape more slowly.
Ensure good ventilation within the oven to promptly remove solvent vapors.
4.What problems are there regarding the environment and foreign objects? How can they be resolved?
Problem: The workshop environment is unclean, and dust falls onto the uncured wet film; or the compressed air contains moisture or oil droplets, which are blown onto the wet film by the spraying system (if it is a spray coater) or air knife.
Solution:
Maintain positive pressure and cleanliness in the coating chamber.
Perform rigorous water and oil removal filtration of the compressed air, and regularly check the drainage system.
5.How to summarize and prevent this?
**Control the entry point:** Ensure the substrate is clean, dry, and free of defects before application.
**Manage the coating:** Guarantee the coating is clean, bubble-free, and has stable parameters.
**Optimize the process:** Setting a reasonable curing curve, especially one with a slow start and a rapid finish, is crucial.
**Maintain the environment and equipment:** Ensure a clean coating environment and that equipment is in good working order.
**First sample confirmation:** Carefully inspect the surface quality of the first sample at the start of production and after changing specifications.