Picture frame effect in powder coating: causes and solutions
The so-called picture frame effect often occurs when textured powders are used in combination with corona guns. This causes visible lines or shadows to appear at the edges of the coated object, resembling a picture frame and impairing the appearance of the coating.
Causes of the picture frame effect
The main cause of the picture frame effect is the uneven charging of the powder at the edges of the workpiece. Especially with textured powders, electrostatic charging can cause increased powder accumulation at the edges, resulting in the undesirable lines.
Recommended solutions
- Use of the Super-Corona® ring: This ring can be easily retrofitted to existing guns and ensures a more even charge of the powder, reducing the picture frame effect.
- Adjusting the high voltage and powder output: After installing the Super-Corona® ring, the settings for high voltage and powder output should be readjusted to achieve optimum results.
- Use of PCC mode: The PCC mode (Precise Current Control) on the OptiStar control units enables more precise control of the charging current, resulting in more even powder distribution.
Conclusion
The picture frame effect can significantly impair the quality of your powder coating. By using suitable accessories such as the Super-Corona® ring and adjusting the device settings, you can effectively counteract this problem and achieve an even, high-quality coating.
