Powder Coating Line Equipment Selection

1. Spray gun selection and matching

1. Type of electrostatic spray gun

Manual spray gun: suitable for small batch, multi-variety or complex workpiece (such as irregular parts, deep cavity parts), you need to choose a model with adjustable voltage (60~100kV) and powder output (such as Gema, Wagner brand), equipped with auxiliary electrode to enhance edge adsorption capacity.

Automatic spray gun: suitable for large quantities of standardized products (such as sheet metal, profiles), it is recommended to use multi-axis reciprocating or robot spraying system (such as ABB, Fanuc), which needs to be matched with closed-loop feedback control to ensure the stability of spraying trajectory and powder output.

Special spray gun: For the inner cavity or dead end, select a rotary cup spray gun or an inner hole spray gun (such as Nordson's Edge series) to improve the uniformity of coverage through centrifugal atomization.

2. Technical parameter requirements

Static voltage: 60~80kV is selected for conventional workpiece, and 80~100kV is required for complex parts or dark powder to enhance the adsorption force.

Powder output control: the accuracy should be within ±5% to prevent coating from being too thick or missing. Digital flowmeter (such as SAMES' MicroFlow) is used for real-time adjustment.

Spray gun spacing: set according to the size of the workpiece and the conveying speed, generally 200~400mm, to avoid electrostatic interference between the gun body.

2. Key to spray powder room design

1. Structural materials

The main body is made of stainless steel or anti-static PP material, the inner wall is smooth and easy to clean to avoid powder residue; the observation window is equipped with explosion-proof glass and automatic cleaning device.

2. Selection of recycling system

Single-stage recovery (cyclone separator): suitable for low color change frequency production line, recovery efficiency is about 70%~85%, low cost but high powder loss.

Multi-stage recovery (cyclone + filter element/cylinder): high efficiency recovery (>95%), recommended for frequent color change or high value powder production line (such as auto parts), the filter element material should be heat resistant (≤120℃) and easy to disassemble and clean (such as PTFE coated filter material).

Nano membrane recovery technology: a new solution with recovery rate> 98% and energy consumption reduced by 30%, but the initial investment is high.

3. Air flow control

The air supply system should ensure the micro negative pressure (-10~-30Pa) in the powder spraying chamber, the wind speed 0.3~0.6m/s, and the frequency conversion fan should be adjusted as needed to prevent powder leakage.

3. Selection of transportation system

1. Chain/hanging conveyor line

Light chain: suitable for small items (<50kg), speed 0.5~3m/min, equipped with anti-swing design to reduce vibration.

Heavy lifting chain: suitable for large parts (such as cabinets, car skeleton), the load capacity should reach 200~500kg, equipped with double chain anti derailment structure.

Underground track conveying: suitable for super heavy parts (>1 ton), maintenance passage and emergency shutdown device should be reserved.

2. Accumulation and continuous selection

Stacking: allows the workpiece to pause, suitable for multi-variety and small-batch production, but needs to control the length of the cache area to avoid temperature fluctuations in the curing furnace.

Continuous: suitable for large-scale production of a single category, high efficiency but poor color change flexibility.

4. Key points of solidification furnace configuration.

1. Heating method.

Electric heating: high temperature control accuracy (±2℃), suitable for precision parts (such as electronic shell), but high energy consumption cost.

Gas heating: low operating cost, need to be equipped with waste heat recovery system (such as heat exchanger), suitable for large parts (such as doors and Windows, pipes).

Infrared radiation: rapid heating (5~10 minutes), suitable for thin coating or heat-sensitive substrate (such as plastic parts), but need to evenly arrange infrared plate to prevent local over-drying.

2. Furnace design.

Insulation layer thickness: the thickness of furnace wall insulation material (ceramic fiber) is more than 150mm, and the temperature difference in furnace is controlled within ±5℃.

Air circulation system: the top air supply + bottom return air structure is adopted, and the uniformity deviation of wind speed is less than 10%, so as to avoid coating bubbling or color difference.

5. Optimization of powder supply system.

1. Selection of powder supply center.

Single pump and single drum: flexible color change but low efficiency, suitable for multi-color small batch production line.

Multiple pumps and buckets: Central powder supply system (such as ITW Gema's SmartCenter) is recommended to support 6~12 kinds of powder quick switching, and the color change time is less than 5 minutes to reduce downtime loss.

Venturi pump vs screw pump: Venturi pump is suitable for low viscosity powder, simple maintenance; screw pump is suitable for high density metal powder, higher powder supply stability.

2. Powder screening and mixing.

The sieve size should match the powder particle size (usually 100~150 mesh), and the vibration motor and magnetic selection device should be equipped to remove impurities.

The mixing ratio of new and old powder is recommended to be less than 30%, and a three-dimensional mixer (such as TURBULA) is used to ensure uniformity.

VI. Auxiliary equipment recommendations.

1. Air compressor and post-treatment equipment.

Oil-free screw air compressor (such as Atlas Copco) is selected, the supply pressure is 0.6~0.8MPa, and three-stage filtration (water removal, oil removal, dust removal, precision up to 0.01μm) is configured at the rear end.

2. Powder cooling device.

For thermal spray powder coating, a water cooling or air cooling unit is added after the recovery system to reduce the powder temperature to 25~30℃ to prevent blockage of the spray gun.

7. Expansion of intelligent equipment.

1. Intelligent spray gun and sensor.

Integrated thickness sensors (such as eddy current or ultrasonic thickness gauges) provide real-time feedback on coating thickness and automatically adjust the spray gun parameters.

2. Automation of transportation and scheduling.

AGV+RFID technology is adopted to realize automatic workpiece identification and path planning, reducing manual intervention.

3. Equipment selection and matching principle.

Capacity matching: the number of spray guns, the length of curing furnace and the conveying speed should be calculated according to the design beat (such as the spray area per hour or the number of workpieces) to avoid bottlenecks.

Formula reference: conveying speed (m/min) = single piece length (m) × target capacity (pieces/h) / 60.

Powder adaptability: metal powder should be selected with high wear resistance spray gun (such as ceramic nozzle) and explosion-proof recovery system; special effect powder (such as texture powder) should improve the accuracy of powder supply.

Flexible expansion: reserve 10%~20% of the equipment margin (such as spray gun station, furnace length), to support future capacity improvement or process upgrade.