Metal Finishing Guide Book


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Page 13 of 843

2. ACHIEVE CONSISTENT QUALITY Blasting is a recipe with many ingredients and techniques, so get to know what affects the speed and quality of your individual application. Variables: • Media: Shape, size, hardness, durability / breakdown rate, ability to be reclaimed for reuse, consistency after repeated usage. • Blasting: Dwell, distance, pressure (PSI), impingement angle, nozzle configuration, operator's visibility. Time between blasting and coating. • Substrate: Material, hardness, malleability, part "geography," and masking requirements. • Coating or corrosion to be removed: Brittleness, toughness, thickness, if it gets gummy when heated by friction, contamination by oils, excess dirt, etc. Changes, lot to lot, in the workpiece. • Operator and maintenance personnel: Technique, training, ability, and work ethic. • Compressed air: Volume (CFM), pressure (PSI), quality, airline restriction. • Equipment: Type and suitability, in-tune or worn, filter condition. Reclaim your media To economize, virtually all industrial systems reuse blast media several times over. But media breaks down as it impacts hard surfaces. In dry blasting, debris from the surface of the workpiece becomes pulverized dust. Dust and broken media must be removed, or the process degrades rapidly4. This requires a dust collector. On cheaper systems only a fraction of the ambient dust Ð nearest the blast cabinetÕs vent Ð is sucked out. ThatÕs not good enough. To maximize the extraction of dust and undesirable fines from the working media, several kinds of air wash or cyclonic separators are employed in conjunction Figure 2. Excellent visibility is a result of durable media, well designed & maintained equipment, run by trained operators. Benefit: high production with negligible rework5. 12

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