Pinholes look similar to craters/retractions, but the underlying mechanism may be completely different.The reliable order of troubleshooting is not to adjust the high pressure or change the paint first, but to: First confirm the defect morphology and occurrence stage → Distinguish the liquid paint from the powder process → Freeze the workpiece, material, air source, grounding and baking evidence → Check the underlying conductive and complete grounding paths → Branch Check the compressed air Water and oil contamination → Check the substrate for deflation, pretreatment and surface contamination → Check the film thickness, flash drying/warming and electric field loading → Replace and repeat the test to confirm the root cause. Four boundaries must be established first: Pinholes are not synonymous with withdrawal. Pinholes are more often manifested as small holes left by gas or volatiles penetrating wet membranes, molten powder membranes; withdrawal or fisheye is more often associated with low surface tension contamination, wetting failure, and localized surface tension gradients. Volcanic craters are morphological descriptions, not root causes. Pits with raised edges or central holes may be from bubble rupture, substrate deflation, solvent boiling, powder membrane reverse ionization, or may co-act with contamination. Poor conductivity of the bottom layer will change the electrostatic deposition, but the root cause of the shrinkage hole cannot be directly confirmed. Abnormal grounding or conductive paths may cause uneven film thickness, local over-spraying, powder rebound, charge accumulation, and high field strength, but the typical fisheye of liquid paint should still be preferentially checked for contamination and wetting. “Electric Field Breakdown” must be graded. It can be seen that ignition, high-voltage alarm or continuous discharge are safety events; microscopic reverse ionization in the powder film belongs to the deposition defect mechanism.The two cannot be confused into one that can continue to be produced.
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