Picture frame effect with textured powders: identifying and eliminating causes
The so-called "picture frame effect" often occurs when textured powders are used in combination with corona guns. This phenomenon manifests itself in darker or glossier edges on the coated workpieces, which impairs the visual quality of the coating. Below, we explain the causes and provide practical solutions based on the recommendations of GEMA.
1. Cause: Use of textured powder with corona guns
When using textured powders in corona guns, the powder may become unevenly charged. This causes more powder to be deposited on the edges of the workpieces, which causes the picture frame effect.
2. Solution: Use of the Super-Corona® ring
The Super-Corona® ring from GEMA has been specially developed to minimise the picture frame effect. It can be easily retrofitted to existing guns and ensures more even charging of the powder.
3. Solution: Adjusting the settings
After retrofitting with the Super-Corona® ring, the high voltage and powder output settings should be readjusted to achieve optimum results.
4. Solution: Use of PCC mode
Using the PCC mode (Precise Charge Control) on GEMA OptiStar control units can also help to prevent the picture frame effect. This mode enables more precise control of the powder charge.
By observing these points and regularly maintaining your equipment, you can increase the efficiency of your powder coating processes and avoid quality problems.
