Painting equipment introduction (Painting knowledge online learning)

The main equipment of painting is divided into surface pretreatment equipment before painting, painting equipment, film drying and curing equipment, mechanized conveying equipment, dust-free constant temperature and humidity air supply equipment and other ancillary equipment. In order to make the utilization rate of various painting equipment reach a relatively high level, it is necessary to establish a reasonable painting production line: first of all, we must determine the production program, complete the process design and program planning, and then carry out the design, manufacturing and installation of non-standard equipment. Therefore, process design and program planning are the basis for the establishment of production lines, and correct and reasonable routes will have a decisive impact on production operations and product quality. The content of process design mainly includes: pre-treatment method of workpiece surface coating quality requirements, spraying method, process flow, coating performance, spraying environment, time, etc.

1. Purpose of painting:

Through coating construction, the coating can form a solid continuous coating on the surface of the coated material and play its decorative, protective and special functions

1.1 Coating elements

The key of painting engineering is: painting process and equipment, painting materials, working environment, and painting management.

The quality of the coated material is the basic condition for obtaining high quality coating. Coating process, equipment and environment are the necessary conditions to give full play to the properties of coating materials, obtain high-quality coatings, reduce production costs and improve economic benefits. Painting management is an important condition to ensure the implementation of the developed process, ensure the stability of painting quality, achieve the purpose of painting and the best economic benefits.

2, painting main equipment

The main equipment of painting is divided into surface pretreatment equipment before painting, painting equipment, film drying and curing equipment, mechanized conveying equipment, dust-free constant temperature and humidity air supply equipment and other ancillary equipment.

2.1 Coating surface pretreatment equipment

2.1.1 Purpose of pretreatment:

Remove the foreign matter carried by the coated parts, such as oxide, rust, grease, etc., and provide a good substrate suitable for the coating requirements, such as phosphating, oxidation, passivation, to ensure that the coating has good anti-corrosion properties and decorative properties.

2.1.2 Pretreatment equipment is mainly divided into physical type and chemical type.

Physical form:

① Remove impurities attached to the surface of the steel plate, and use diluent to remove grease and other dirt.

② If there are sulfates or corrosive salts, they should be washed with water and dried with compressed air.

③ On the steel plate pretreatment line, the oxide, rust and other impurities are cleaned by shot blasting or sandblasting, and then the steel surface is cleaned with a vacuum cleaner or purified compressed air.

Chemical formula:

Dip type, spray type, combination type, combination type of spray - dip - spray.

It is mainly composed of tank body, tank heating system, ventilation system, tank stirring system, phosphating slag removal system, oil-water separation system, etc. Among them, phosphating slag removal and oil-water separation device is the key system, phosphating slag removal has sedimentation method, spinning liquid separation method, inclined plate sedimentation method, bag filtration method, plate and frame filter press and other common methods. The separation of oil and water mainly includes adsorption method, ultrafiltration method, hot oil separation method and centrifugal method.

2.2 Painting Equipment

2.2.1 Painting Method

There are many methods of painting, brush paint, dip paint, air spraying, high pressure airless spraying, electrostatic spraying, electrophoretic painting, spray paint, roll coating and so on.

2.2.2 Painting Environment

The ideal painting environment should meet the requirements of good lighting, appropriate temperature, humidity and cleanliness of the air, good ventilation and fire and explosion protection.

2.2.3 Spray painting equipment

The role of the painting equipment is to limit the oversprayed paint mist in a certain area and filter it, so that the operator can get a working environment that meets the health conditions and safety norms. In addition, construction conditions with certain temperature, humidity and cleanliness should also be provided.

2.2.3.1 Classification of common spray booth

1) Dry spray booth: suitable for small batch and more precise workpiece painting;

2) Spray painting room: suitable for small workpiece painting;

3) Water curtain painting room: suitable for medium workpiece painting;

4) Water spin spray booth: suitable for large work pieces with high decorative requirements and the precision requirement is not too high.

2.2.3.2 Main structure of spray booth

1) Chamber body: The role is to limit the spray paint mist to a certain range.

2) Paint mist filter device: dry type and wet type two.

Dry type: The paint mist is filtered through a baffle or filter paper.

Wet type: Through the mixing of air and water, the paint mist particles are separated from the air. (Wet room is more environmentally friendly than dry room)

3) Water supply system: ensure the normal circulation of water required by the wet spray booth.

4) Ventilation system: composed of supply air and exhaust air, it provides air with a certain temperature, humidity and cleanliness to the equipment to ensure that the indoor air is laminar flow.

5) Lighting device: ensure that the equipment has good illumination.

2.2.4 Paint Dipping Device

The workpiece is immersed in the paint, and the adhesion of the paint is used to make the surface of the workpiece adhere to a layer of paint.

2.2.5 Electrostatic spraying equipment

Electrostatic spray painting: based on the principle of electrostatic field action on charge. It generally includes electrostatic spray booth, high voltage electrostatic generator, electrostatic spray gun device, paint supply device, safety device and so on.

2.2.6 Electrophoretic painting equipment

Electrophoretic coating: electrophoretic coating is in the Yin and Yang poles, applied under the action of voltage, the charged paint ions move to the cathode, and the alkaline reaction generated by the cathode surface to form an insoluble substance, deposited on the surface of the workpiece.

It consists of four processes:

1) Electrolysis (decomposition)

The reaction at the cathode is initially an electrolytic reaction, generating hydrogen and hydroxide ions OH, which results in the formation of a highly alkaline boundary layer on the cathode surface. When the cation reacts with hydroxide to form an insoluble substance, the film is deposited, and the equation is: H2O→OH+H

2) Electrophoretic dynamic (swimming, migration) cationic resin and H+ move towards the cathode under the action of electric field, while the anion moves towards the anode process.

3) Electrodeposition (precipitation)

On the surface of the coated workpiece, the cationic resin interacts with the surface of the cathode alkaline, neutralizes and precipitates without deposits, and deposits on the coated workpiece.

4) Electroosmosis (dehydration)

The coating film on the surface of the paint solid and the workpiece is semi-transparent and has a majority of pores. The water is seeped out from the cathode coating film and causes the coating film to dehydrate under the action of an electric field. The coating film is absorbed on the surface of the workpiece to complete the entire electrophoresis process.

Electrophoretic surface treatment process features:

Electrophoretic paint film has the advantages of full, uniform, flat and smooth coating. The hardness, adhesion, corrosion resistance, impact property and permeability of electrophoretic paint film are obviously superior to other coating processes.

2.2.7 Powder electrostatic spraying equipment

Powder coating has good economy, no environmental pollution, high efficiency, one spray can make the coating thickness of 50 μm or more.

Powder electrostatic spraying equipment mainly includes powder spraying room, high voltage electrostatic generator, electrostatic spraying gun, powder feeder, powder recovery device and so on.

2.3 Drying Equipment

2.3.1 Main classification and composition of drying equipment

Drying equipment has various types of classification, usually according to the production organization, the shape of the chamber, the use of energy, heat transfer, air circulation in the room and other classification according to the heating method is divided into:

Convection drying, radiation drying, convection + radiation drying;

Divided into structural forms:

Straight through type, bridge type, half bridge type, dead end type, double layer type, P font, etc.

The main components:

1) Chamber body: the circulating hot air does not overflow, so that the indoor temperature is kept within a certain range;

2) Heating system: there are radiation heating and convection heating, to ensure that the indoor air temperature is controlled within the process requirements;

3) Air duct: Guide the circulation of hot air in the drying room to transfer heat to the workpiece

4) Air filter: filter dust in the air

5) Air heater; Heat indoor circulating air

6) Fan: forced drying room hot air circulation

7) Air curtain system: prevent hot air spillover, improve thermal efficiency;

8) Temperature control system: the device to ensure that the temperature of each section of the room meets the process requirements.

2.4 Mechanized conveying equipment

Mechanized conveying equipment is mainly divided into two categories: air conveying and ground conveying.

Air transport: ordinary suspension conveyor, double chain suspension conveyor, light suspension conveyor, accumulation type suspension conveyor, hoist conveyor and so on.

Ground conveyor: reverse deposit conveyor, skid conveyor, tank chain conveyor, ordinary ground conveyor and so on.

The role of mechanized equipment is to organize, coordinate and connect all kinds of equipment in the entire painting production line to achieve stable operation.

3. Main test requirements of coating equipment

1) The drying equipment mainly tests the uniformity of the furnace temperature, usually controlled at ± 5 ° C, and can test up to 6 positions at a time with the furnace thermometer.

2) Painting equipment mainly tests illuminance, temperature, humidity and average wind speed: For the higher requirements of the painting equipment, the illumination requirement is 800 ~ 1000Lx, the temperature requirement is 23 ± 2 ℃, the relative humidity is 55± 5%, the average wind speed is 0.45 ~ 0.55m/s 3) All the equipment in the operating area noise ≤ 85db.