Products Description
Powder Spraying Process for Construction Machinery
The powder coating process for construction machinery is a surface treatment technology widely applied in the manufacturing industry of construction machinery. It aims to provide excellent protection and decorative properties for construction machinery. The following will introduce in detail its process flow, equipment composition, and process characteristics.
Process Flow
Pretreatment
Degreasing: During the processing of construction machinery parts, various oil stains and impurities will adhere to them. First, the parts are immersed in a solution containing a powerful degreaser. Through the chemical reaction between the degreaser and the oil stains, the oil stains are decomposed and separated from the surface of the parts, thus achieving the purpose of degreasing and laying a good foundation for subsequent coating.
Water Washing: After degreasing, the parts need to go through multiple water washing processes to thoroughly remove the residual degreaser and impurities on the surface. The water washing process usually adopts a multi-stage countercurrent rinsing method, which can not only ensure the cleaning effect but also save water.
Rust Removal: For metal parts commonly used in construction machinery, if there is rust on the surface, rust removal treatment is required. There are two common rust removal methods: chemical rust removal and mechanical rust removal. Chemical rust removal uses acid solution to react chemically with rust to dissolve and remove it; mechanical rust removal, on the other hand, uses methods such as shot blasting and sandblasting. High-speed moving shot or sand grains impact the surface of the parts to remove rust and scale.
Phosphating Treatment: Phosphating is a process of forming a phosphate chemical conversion film on the surface of the parts. This phosphating film can significantly improve the adhesion between the coating and the metal surface and enhance the corrosion resistance of the parts. After phosphating treatment, passivation treatment is usually carried out to seal the pores of the phosphating film and further improve its corrosion resistance.
Drying: After the pretreatment, a large amount of water remains on the surface of the parts, and drying treatment must be carried out. The drying method generally adopts hot air circulation drying. The parts are put into a drying furnace, and the surface water is removed by circulating hot air to ensure that the surface of the parts is dry and clean, preparing for powder coating.
Powder Coating
Loading: The pretreated parts are accurately hung on the conveying device of the coating line, and the conveying device will send the parts to each coating station in turn.
Electrostatic Spraying: In the enclosed spraying chamber, the electrostatic spraying equipment sprays the powder coating through the spray gun. At the same time, the spray gun generates a high-voltage electrostatic field, making the powder coating particles charged. Under the action of the electric field force, the charged powder coating particles are evenly adsorbed on the surface of the parts, forming a uniform powder coating. This electrostatic spraying method enables the powder coating to achieve good coverage on the complex shapes and structures of the parts, including corners and gaps.
Fluidization and Recycling: During the spraying process, some powder coatings fail to be adsorbed on the surface of the parts in time and scatter. The powder recycling system will use equipment such as a cyclone separator and a filter cartridge to separate these scattered powder coatings from the air. Then, through the fluidization device, the powder is returned to the fluidized state so that it can be conveyed to the spray gun for spraying again, thus improving the utilization rate of the powder coating and reducing production costs.
Curing
High-temperature Curing: The parts with the powder coating sprayed enter the curing furnace along with the conveying device. In the curing furnace, the parts are heated to a specific temperature range (generally 180 - 220°C) and maintained for a certain time (usually 15 - 30 minutes). Under the action of high temperature, the resin and curing agent in the powder coating undergo a cross-linking reaction, causing the powder coating to cure into a hard, wear-resistant, and corrosion-resistant paint film, thereby obtaining good physical and chemical stability.
Cooling: After the cured parts are taken out of the curing furnace, cooling treatment is required to reduce their temperature to room temperature. The cooling method usually adopts forced air cooling. A fan blows cold air onto the parts to accelerate the cooling process, facilitating subsequent quality inspection and packaging.
Equipment Composition
Pretreatment Equipment: It includes degreasing tanks, water washing tanks, rust removal equipment, phosphating tanks, passivation tanks, and drying furnaces. These devices are equipped with systems such as heating, stirring, and circulation filtration to ensure the stability and consistency of the pretreatment process.
Powder Coating Equipment: It mainly consists of an electrostatic spray gun, a powder supply system, a powder recycling system, and a spraying chamber. The performance of the electrostatic spray gun directly affects the spraying effect. The powder supply system can accurately control the supply amount of the powder coating. The powder recycling system can effectively recycle the unused powder coating, and the spraying chamber provides a closed and clean environment for the spraying operation.
Curing Equipment: The curing furnace is the core of the curing equipment. Its heating methods include various types such as electric heating, gas heating, and fuel oil heating. It is also equipped with a temperature control system and a hot air circulation system to ensure that the temperature inside the furnace is uniform and meets the process requirements for the curing of the powder coating.
Conveying Equipment: Suspended conveying chains or roller conveyors are used to transport the parts smoothly and continuously between each process link, and the conveying speed can be adjusted according to the production rhythm.
Control System: It is composed of a programmable logic controller (PLC) or an industrial computer and is responsible for the automated control and monitoring of all devices in the entire powder coating process, including temperature, time, speed, spraying parameters, etc., to ensure the stability and consistency of the coating quality and realize the intelligent management of the production process.
Process Characteristics
Excellent Coating Performance: The coating formed by powder coating has high hardness, wear resistance, corrosion resistance, and weather resistance, which can effectively protect the parts of construction machinery from damage in harsh working environments and extend their service life.
Environmental Protection and Energy Conservation: Compared with traditional liquid coating, powder coating does not use organic solvents, greatly reducing the emission of volatile organic compounds (VOCs), which is friendly to the environment. At the same time, the recycling rate of powder coating is high, reducing the consumption of coating and saving resources.
High Production Efficiency: The powder coating process adopts an automated production line, with each process closely connected and operating continuously, resulting in a fast production speed. Moreover, the curing time of the powder coating is short, enabling rapid production, improving production efficiency, and meeting the needs of large-scale industrial production.
Good Appearance Quality: Powder coatings have a rich variety of colors and gloss levels to choose from, which can meet the personalized appearance requirements of different customers for construction machinery. The coating surface is flat and smooth, without defects such as flow marks and orange peel, and has good decorative properties.
Strong Adaptability: The powder coating process can be applied to construction machinery parts of various shapes and sizes. Whether they are large structural parts or small parts, good coating effects can be obtained. At the same time, for parts of different materials, such as steel and aluminum alloy, only the corresponding pretreatment process needs to be adjusted to carry out powder coating.
