汽車涂料課程-資料下載頁
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【正文】 ough Spray Introductory Automotive OEM Paint Course ?Paint defects causes and corrective actions ? Craters ? Orange peel ? Dry spray ? Pop Solvent boil ? Mottling, Floating and Flooding ? Sag Runs Paint Defects Causes and Corrective Actions Craters: Craters are circular recesses in the paint film. Causes are mainly due to oil, grease, wax and silicon residue. Causes: ? Incorrect use of paint additives. ? Unsuitable cleaning agents. ? Contaminated air from other work areas (polishes, oil, fine dust etc). ? Marks from clothing, rubber gloves, skin and hair lotions. ? Over spray paint from preceding or following process. ? Oil in pressed air. ? Poor cleaning of surface. Paint Defects Causes and Corrective Actions Orange Peel: Poor surface texture of the painted surface similar to the texture of an orange skin (a dimpled appearance). Causes: ? Spray gun held too far from surface of the object. ? Spray pressure too low (poor atomization). ? Paint film too thin. ? Solvent too fast. ? Viscosity of paint too high. ? Spray nozzle too small. ? Flashoff time too long between coats. ? Dry spray application technique. Paint Defects Causes and Corrective Actions Pop / Solvent Boil: Blister like surface defects due to solvent entrapment in the surface of the paint film. Causes: ? Film applied too thick. ? Flash off time between individual paint coats too short. ? Flash off time before baking too short. ? Too fast of heatup rate. ? Solvent selection too fast, use a slower evaporating reducing solvent. ? Viscosity too high. ? Air pressure too low. Paint Defects Causes and Corrective Actions Mottling /Floating / Flooding: Spots or strips of light and dark patches (blotchy) seen in a metallic coating. Causes: ? Uneven spray application. ? Flashoff between coats or prior to application of clearcoat too short. ? Color coat applied too thin. ? Spray viscosity too high causing wet films. ? Atomization pressure too low. ? Fan on spray gun too narrow. ? Spray gun too close to the unit. ? Overlap of previous gun stroke improper. Paint Defects Causes and Corrective Actions Sag / Runs: Vertical streaks of paint. These can be beads, droplets, larger globules or Curtain effects in the paint film. Causes: ? Viscosity too low (too thin). ? Solvent blend too slow evaporating. ? Paint or object to be painted too cold. ? Paint applied too thick. ? Flashoff time too short. ? Spray gun held too close to the object. ? Low atomizing pressure. ? Film thickness too high. ? Insufficient flash time between coats. Introductory Automotive OEM Paint Course ?Safety And Health Issues ? Flammable liquids ? Sparks in the spray booth area ? Exposure to skin, eyes and lungs ? Paint spills on clothing
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