In the manufacturing of parts and components, surface treatment is essential for their practical applications. However, during powder electrostatic spraying, particles can form on the surface, compromising the quality of the workpiece and affecting the stability of the assembled mechanical equipment.
Impact of Surface Particles
Particles on the workpiece surface not only mar its appearance but also degrade its performance. These particles can introduce external moisture, gases, or corrosive substances into the substrate, leading to localized corrosion and reducing overall quality. Therefore, minimizing surface particles during powder spraying is crucial to lower production costs and enhance efficiency.
Causes and Preventive Measures
1. Unmeltable Inclusions in the Powder
If dust particles, crushed fibers, or other substances are present in the powder and their size or height exceeds the coating's thickness, they will appear on the workpiece surface. The primary sources of these particles are:
- Powder Raw Materials: Particles originating from the manufacturer's production process can cause continuous particle formation during spraying. Improving powder production quality is essential to prevent this.
- Powder Usage: Particles may be introduced during powder handling, such as from the container or when opening the powder bag. To mitigate this, clean the powder container and ensure the bag’s surface is clean. Add powder in small, multiple batches to reduce particle introduction.
Preventive Measures:
- Screen the powder to check particle size before use.
- Manufacturers should provide particle distribution information.
- Conduct spraying tests on thinner samples to observe particle distribution.
2. Sand Collection from Lint
Maintaining a clean environment in the coating workshop is vital. Fibrous substances in the air can adhere to the workpiece surface due to static electricity, forming circular or linear sand accumulations. These fibers may come from operator clothing or maintenance materials.
Preventive Measures:
- Use dedicated changing rooms for operators.
- Prohibit items that may cause fiber floating in the spraying room.
- Use lint-free towels for equipment maintenance.
- Install stainless steel wire mesh filters to capture lint without impeding ventilation.
3. Environmental Dust Particles
Airborne dust can be attracted to the workpiece surface by static electricity during spraying. This dust may come from unclean air, vehicles, or workshop cleaning.
Preventive Measures:
- Ensure the spray workshop is well-sealed.
- Establish a positive pressure environment to maintain air circulation and filtration.
- Keep indoor and outdoor pressure consistent to maximize cleanliness.
- Install filters at the air inlet of the curing oven to minimize air convection and dust entry.
4. Powder Volatiles
Some powder substances may volatilize into gas at curing temperatures, leading to particle formation.
Preventive Measures:
- Use volatile inhibitors at the curing oven entrance to capture such particles.
5. Contaminants from Workpieces and Racks
Carried items such as rust on hanging rods, preprocessing residues, residual paint, iron filings on magnetic fixtures, and repair materials like tape and putty can fall off at high temperatures, contaminating the oven environment.
Preventive Measures:
- Ensure hangers and workpieces are clean before use.
Flush or clean new hangers before deployment.
Conclusion
Effectively managing and reducing surface particles during powder spraying enhances product quality and operational efficiency. By addressing the sources of contamination and implementing preventive measures, manufacturers can achieve better outcomes in their surface treatment processes.
