Causes of Uneven Primer Coating Thickness on Steel Plate Pretreatment Lines and Solutions for Precise Paint Control

In automated pre-treatment painting lines, an excessively thin primer film fails to provide adequate long-term rust protection, while an overly thick film can wrinkle during the drying process and lead to paint wastage. Furthermore, excessive variation in film thickness across the width of the steel plate is a common cause of quality inspection failures in steel construction and shipbuilding facilities. These issues are primarily driven by suboptimal spray gun positioning, inconsistent conveyor speeds, fluctuations in paint supply pressure, and imbalanced air pressure settings.

The shot-blasting and painting system from Qingdao KEEJOO Group utilizes a symmetrical arrangement of multiple spray guns, supported by high-pressure airless piston pumps that ensure stable paint delivery through a real-time, closed-loop pressure control system. The height and angle of the spray guns are fully adjustable, allowing for comprehensive coverage across plates of varying widths. The entire conveyor line operates at a constant, frequency-controlled speed with minimal fluctuation. An optional in-line film thickness monitoring module enables real-time tracking of thickness deviations, with automatic parameter fine-tuning. The painting booth is designed as a sealed, negative-pressure environment to prevent paint mist from escaping, while paint residue is collected for centralized disposal. The system maintains a film thickness tolerance of ±5μm, ensuring exceptional consistency. This not only reduces paint consumption but also reliably meets stringent quality standards, thereby minimizing the need for rework due to coating defects in high-volume production.