Water paint line

What is a water-based paint line?

A water-based paint line is an integrated system of equipment arranged and interconnected according to a defined process flow to carry out operations ranging from product loading and surface treatment to paint application, drying or curing, and product unloading. Depending on the product type, coating system, production volume, and required level of automation, the line may use a continuous conveyor, batch handling system, or other suitable product transfer and loading solutions.

Compared with powder coating, a water-based paint line requires particular attention to ventilation, overspray collection, and the management of airborne substances generated during the spraying process. Depending on the type of paint and the solvents or other volatile components involved, the system may include a spray booth, paint collection and filtration equipment, supply and exhaust air systems, and suitable air treatment equipment in accordance with process requirements and applicable regulations. Paint application can be performed manually, semi-automatically, or automatically using robots. With manual spraying, coating quality depends significantly on the operator's technique and experience. In an automated robotic system, parameters such as movement trajectory, spraying speed, spray distance, and spray angle can be programmed and controlled, helping maintain process consistency under suitable production conditions.

Water paint line

Water-based paint process

The water-based paint process is developed based on the product type, substrate material, coating system, and quality requirements of each application. In general, a water-based paint line can be organized into three main process groups: surface pretreatment and cleaning, paint application, and drying or finishing. Depending on product requirements, each process group may consist of multiple stages and can be carried out using manual, semi-automatic, or fully automated equipment.

Removal of surface contaminants

The initial stage is intended to remove contaminants and surface defects that may affect the subsequent painting process. Depending on the condition of the workpiece, the treatment may include removing dust, oil and grease, machining chips, welding slag or excess metal around welded areas, rust, existing paint coatings, and other contaminants adhered to the surface.

The treatment method is selected according to the substrate material and surface condition and may involve mechanical cleaning, abrasive blasting, chemical cleaning, or a combination of different methods. The objective of this stage is to create a clean and suitable surface for subsequent treatment, thereby supporting coating adhesion and overall paint film consistency.

Cleaning step before water painting process

Primer application

A primer is used in certain coating systems to improve adhesion between the coating and the substrate while supporting surface protection and the overall durability of the coating system. Depending on the product, substrate material, and technical requirements, the primer may be applied as a standalone coating or used in combination with subsequent topcoat layers. The selection of the primer and application conditions should be based on the coating system and the technical specifications provided by the paint manufacturer.

Cleaning

After contaminant removal and pretreatment, the product surface needs to be cleaned to remove residual contaminants, dust, oil, grease, and any chemicals that may remain on the surface. Depending on the process configuration, this stage may include water rinsing, multi-stage rinsing, or other suitable cleaning methods. Controlling rinse water quality, rinsing time, and drainage performance is important for minimizing chemical carryover into subsequent stages and maintaining a suitable surface condition before painting.

Drying

After rinsing, residual water on the product surface needs to be removed before the product proceeds to painting or the next drying stage. Depending on the line configuration, drying may be achieved through natural drainage, airflow, heated air, or a drying chamber. Proper control of surface dryness helps minimize the effects of residual water on paint application and coating consistency. Drying conditions should be determined according to the substrate material, coating system, and process requirements of each product.

Water-based paint application

Water-based paint, or liquid paint, can be applied to the surface using various methods, including air spray, airless spray, air-assisted airless spray, or electrostatic spraying where the paint system and equipment are compatible. Certain products or specialized processes may use dipping or other coating methods instead of spraying.

During application, parameters such as paint flow rate, pressure, viscosity, spray distance, movement speed, and spray angle should be properly controlled to minimize sagging, dripping, or uneven film thickness. Depending on product requirements, the coating system may consist of a primer, color coat, and topcoat. For automated spraying systems, robots can be programmed to maintain consistent spray trajectories, speeds, and distances. With manual spraying, coating quality depends more significantly on the operator's technique and experience.

Flash-off process

After spraying, certain coating systems require a flash-off period before the product enters the drying or subsequent treatment stage. During this stage, water, solvents, or other volatile components in the wet film are allowed to evaporate according to the characteristics of the coating system. The flash-off time and conditions should be determined based on the paint type, film thickness, temperature, humidity, airflow rate, and the paint manufacturer's specifications. Proper control of this stage can help minimize surface defects such as bubbling and pinholes and support consistent film formation during subsequent drying and curing.

Drying and heat treatment

After spraying and flash-off, the product may be dried or heat-treated depending on the characteristics of the coating system. Some paints can dry under ambient conditions, while other systems require drying or curing in an oven at specified temperatures and for a defined residence time. For coating systems that require heat treatment, oven temperature and residence time should be consistently controlled according to the paint manufacturer's technical specifications. Proper heating conditions help the coating achieve the required drying or curing state in terms of hardness, adhesion, appearance, and overall durability.

Configuration of a water-based paint line

Surface treatment equipment

Deionization and static control area: A static control area may be incorporated into certain paint lines to neutralize electrostatic charges on the product surface before painting. The system may use ionizing bars in combination with an airflow to reduce the tendency of charged surfaces to attract dust, thereby supporting surface cleanliness before paint application.

Primer spray booth: A primer spray booth is used for primer application when required by the process. The area may be equipped with suitable ventilation, air supply and exhaust, and filtration systems to control overspray and airborne substances generated during spraying. Depending on the primer and product requirements, the primer spray area may be integrated with temperature-control equipment or a suitable flash-off and drying area.

Paint mixing room

The paint mixing room is used to mix and prepare paint according to the formulation and technical specifications of each coating system. The process may include paint mixing, viscosity adjustment, and the addition of hardeners, solvents, water, or additives as specified by the paint manufacturer. The mixing area should be equipped with an appropriate ventilation system to control vapors generated during paint preparation. Depending on the paint type and scale of operation, the system may incorporate suitable collection, filtration, or air treatment solutions in accordance with process requirements and applicable regulations. Environmental control within the mixing room also helps minimize the ingress of dust and other contaminants into the paint material before it is transferred to the spraying process.

Water paint mixing room

Flash-off area

After paint application, the product may be transferred to a flash-off area to provide the time required for water, solvents, and other volatile components in the wet film to evaporate before the product proceeds to the drying or subsequent treatment stage. The flash-off area is typically positioned after the paint application stage or between coating layers, depending on the requirements of the coating system.

The supply and exhaust air systems are designed to maintain suitable airflow conditions, support the evaporation process, and help minimize coating defects. The flash-off time and operating conditions should be determined based on the paint type, film thickness, temperature, humidity, airflow rate, and the paint manufacturer's specifications.

Liquid paint spray booth

A liquid paint spray booth is designed to control spraying conditions, collect excess paint, and maintain an appropriate airflow pattern during the coating process. Depending on the paint type and spraying method, the booth may be equipped with supply and exhaust air systems, overspray collection equipment, filtration systems, and suitable air treatment solutions in accordance with process requirements and applicable regulations.

During spraying, a portion of the paint does not adhere to the product surface and becomes airborne as overspray. Therefore, the overspray collection and filtration system should be selected according to the paint type, spraying rate, and spray booth configuration. For coating systems containing organic solvents, additional ventilation and air treatment solutions should be considered based on the characteristics of the coating system and project requirements.

The spraying process can be performed manually, semi-automatically, or automatically using robots. Manual spraying can be suitable for low-volume production, products with diverse geometries, or applications requiring greater flexibility in operation. In automated systems, robots or dedicated spraying equipment can control the spray trajectory, speed, distance, and angle according to programmed parameters, helping maintain coating process consistency when properly designed and configured.

Handmade water paint

or carried out automatically by a paint spraying robot or by dipping into a tank.

Automatic water paint

Drying and coating treatment system

For water-based or liquid paint lines, the drying and coating treatment method is selected based on the paint type, film-forming mechanism, substrate material, coating thickness, and technical requirements of the product. Depending on the coating system, products may be dried under ambient conditions, using forced air or heated air, or in a drying chamber or oven. Certain specialized coating systems may use infrared (IR) radiation or ultraviolet (UV) radiation to support drying or curing. Infrared drying chambers or ovens can be used when the coating system and product are compatible with radiant heating. Heating performance depends on the paint type, substrate material and product geometry, surface color, distance between the heat source and the product, and equipment arrangement inside the oven.

For UV-curable coatings, ultraviolet radiation is used to initiate the curing process of photoreactive components in the coating system. This method is only suitable for coatings specifically formulated for UV curing and requires the coating, irradiation equipment, and operating conditions to comply with the technical specifications of the coating system. When a drying oven or thermal treatment oven is used, the temperature and residence time should be set according to the paint manufacturer's requirements while remaining compatible with the heat resistance of the substrate and product construction. Stable control of temperature, airflow rate, and treatment time helps maintain coating film quality and minimize defects that may occur during drying or curing.

Paint line drying chamber

Conveyor system

The system typically uses a dual-rail free-track conveyor or a monorail conveyor. The dual-rail conveyor consists of two independent rails, providing greater flexibility in configuring the conveying route, speed, and operation of individual stations through PLC control. A monorail conveyor has a simpler structure and generally offers a lower investment cost than a dual-rail system; however, its conveying layout and operating flexibility are more limited.

Paint line conveyor

Wet paint types

Wet paint refers to liquid coating materials that are widely used across various industries to meet different requirements for color, gloss, adhesion, surface protection, and other specialized performance characteristics. Depending on the resin, solvent, curing agent, and additives used, each coating system has different properties and application ranges.

Acrylic paint offers good film-forming properties, color retention, and weather resistance, making it suitable for a wide range of applications. Some acrylic systems are formulated to improve moisture resistance, UV resistance, or to meet specific requirements for appearance and surface durability.

Epoxy paint provides good adhesion, abrasion resistance, and resistance to many types of chemicals. Epoxy coatings are commonly used where high film hardness and surface protection are required. Heat resistance and outdoor durability depend on the specific coating system and formulation.

Silicone paint can provide good heat resistance and weather resistance in coating systems designed for high-temperature environments or outdoor applications. Moisture and UV resistance also depend on the composition, formulation, and intended application of each coating system.

Polyurethane paint provides durable film formation, good adhesion, and chemical and moisture resistance for a wide range of industrial applications. Some polyurethane systems can also maintain good color and gloss retention under outdoor conditions.

The selection of a coating system should be based on the substrate material, operating environment, appearance requirements, durability requirements, application method, and drying or curing conditions of the coating system. Parameters such as viscosity, coating film thickness, temperature, and treatment time should also be determined according to the requirements of each coating system.

Materials suitable for wet paint

Wet paint can be applied to a wide range of materials. However, coating adhesion and film quality depend on the characteristics of the substrate, surface preparation method, coating system, and drying or curing process. Therefore, each material group requires an appropriate coating system and surface treatment process.

Metals such as iron, steel, aluminum, and various alloys can be coated with wet paint to provide corrosion protection, improve surface durability, and meet requirements for color, gloss, and appearance. For metal products, surface pretreatment before painting plays an important role in coating adhesion and overall coating durability.

Plastics and PVC can be coated with certain specialized paint systems to improve appearance or provide specific surface properties. When designing a painting process for plastic materials, factors such as heat resistance, surface energy, cleanliness, and compatibility between the substrate and coating system should be considered.

Wood and engineered wood materials can also be coated with wet paint to provide color, gloss, and surface protection. Depending on the product, the process may include surface preparation, primer application, color coating, and topcoat application.

Concrete and certain construction materials can be coated with specialized paint systems to protect the surface, improve abrasion resistance, or meet appearance requirements. The coating type and application method should be selected according to the surface characteristics and actual operating conditions.

Composite materials can also be coated with suitable paint systems to provide color, improve appearance, or enhance surface protection. Since composite materials vary widely in composition and structure, the coating system and surface preparation method should be selected based on the specific characteristics of each product.

Features of automatic water-based paint lines designed and manufactured by CNC VINA

The coating process may vary depending on the product, substrate material, and coating system. Therefore, pretreatment, paint application, flash-off, drying, or curing stages should be selected and arranged according to the product characteristics and coating performance requirements.

CNC VINA provides automatic water-based paint lines and industrial coating systems designed according to the requirements of each project. Depending on the product, production capacity, paint type, application method, and level of automation, the line can be configured with surface treatment systems, paint spray booths, overspray collection equipment, flash-off areas, drying or thermal treatment systems, and product conveying systems. With experience in implementing automation solutions and production lines for various industrial products, CNC VINA can integrate individual processes and equipment into a coordinated system that meets the productivity, coating quality, and operating requirements of each project.

Customers can also refer to other coating lines supplied by CNC VINA, including Plastic coating line, Metal coating line, Powder coating line, Automatic coating line, and Automotive coating line. Contact CNC VINA to discuss your coating line investment requirements and receive consultation on a suitable design based on your products, production capacity, and process requirements.

CÔNG TY CỔ PHẦN ỨNG DỤNG CÔNG NGHỆ & CNC VIỆT NAM

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