The coating head structure of a five-layer coating and laminating machine is a core component ensuring uniform coating of multiple layers of material. Its design must consider multiple dimensions, including fluid dynamics, material properties, and mechanical precision. The coating head utilizes mechanisms such as multi-roller coordination, precise gap control, and dynamic pressure adjustment to ensure uniform distribution and consistent thickness of each coating layer.
The core structure of the coating head typically consists of an applicator roller, a coating roller, a traction roller, and a doctor blade system. The machining and assembly precision of each roller directly affects the coating effect. Taking two-roller transfer coating as an example, the gap between the applicator roller and the coating roller needs to be accurate to the micrometer level. Adjusting the gap size controls the amount of coating transferred. This design requires extremely high surface smoothness of the rollers to avoid uneven coating distribution caused by minute irregularities. For example, the surface roughness of a high-precision smooth roller needs to be controlled within an extremely small range to ensure that the coating forms a uniform liquid film on the roller surface, preventing local accumulation or delamination.
The doctor blade system is a key component in the coating head for achieving precise thickness control. The material, hardness, and installation angle of the doctor blade must be matched to the characteristics of the coating. For high-viscosity coatings, wire scrapers are commonly used. These are made of high-precision cold-drawn round steel with tightly wound stainless steel wire, driven by a miniature DC motor. The scraping pressure can be adjusted in real time to eliminate residual coating on the roller surface. Airflow scrapers, on the other hand, apply a uniform airflow to the coating roller. They are suitable for adhesives with good flowability, and the airflow distribution must cover the entire width of the roller surface to avoid insufficient scraping in certain areas. The contact pressure between the scraper and the roller surface needs to be dynamically balanced to thoroughly remove excess coating while preventing excessive pressure that could cause roller wear or coating splatter.
The coating heads of a five-layer coating and laminating machine must simultaneously manage the independent and coordinated application of five layers of coating. Each coating head is equipped with an independent pressure regulation system, precisely controlling the inter-roller pressure through hydraulic or pneumatic devices to ensure that each layer of coating reaches the preset thickness before lamination. For example, the first and second coating heads may use different blade types to accommodate coatings of varying viscosities; while the third to fifth coating heads adjust the coating amount through speed difference control, i.e., by adjusting the roller speed difference to change the coating transfer rate, avoiding the limitations of mechanical gap adjustment. This layered control strategy allows the equipment to flexibly handle diverse material combinations, such as laminating substrates like paper, film, and metal foil with coatings like water-based adhesives and hot melt adhesives.
The mechanical stability of the coating head is fundamental to ensuring long-term uniform coating. The main body of the equipment uses high-rigidity materials to reduce vibration during high-speed operation; the rollers employ a dynamic and static balance design to reduce sway caused by centrifugal force; and the built-in heating and insulation system ensures uniform roller surface temperature, preventing changes in coating fluidity due to temperature differences. For example, when coating hot melt adhesives, the rollers need to maintain a constant temperature to prevent localized cooling that could cause the adhesive to solidify, affecting coating continuity.
Environmentally adaptable design further enhances the uniformity performance of the coating head. The coating head is equipped with a sealed structure to prevent dust or impurities from entering the roller gap. Some high-end models also integrate a cleaning device that automatically cleans the roller surface during roll changes or shutdowns to prevent coating residue from hardening. Furthermore, the coordinated control of the coating head and drying system is crucial. By monitoring the coating drying status in real time, the coating speed and temperature are adjusted to prevent coating shrinkage or cracking caused by uneven drying.
The coating head of the five-layer coating and laminating machine, through multi-roll precision coordination, dynamic doctor blade adjustment, layer pressure control, and environmentally adaptable design, constructs a uniform coating guarantee system from micro to macro. This structure not only meets the stringent requirements of multi-layer composite materials for thickness accuracy, adhesion, and appearance consistency, but also supports rapid changeover through modular design, adapting to the diverse coating process needs of different industries.
