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Fig. 3. Typical mechanical plating layout. dling system. The plating takes place in stainless steel variable-speed tumbling barrels (Fig. 1). Because the entire process operates at an acidic pH of 1 to 2, the barrels must be lined with an inert, abrasion-resistant protective coating, such as urethane, neoprene, or polypropy- lene, to a thickness of 19 to 25 mm (0.75-1 in.). Typical plating barrels have capac- ities of 0.04 to 1.13 m3 (1.5-40 ft3 ), where capacity is defined as the total available working volume, typically 30 to 35% of the total volume. For example, a 0.57 m3 (20 ft3 ) plating barrel will hold approximately 910 kg (2,000 lb) of 25-mm- (1-in.)-long threaded fasteners and 1,000 kg (2,200 lb) of glass bead mix. See bar- rel loading capacity chart (Fig. 2). In Fig. 3, parts to be mechanically plated are brought to the barrel load- ing hoist (1). Glass media are trans- ferred from an overhead media reser- voir tank (2) into the plating barrel (3). The operator's platform and con- trol panels serve as the staging area for operator activities. After plating, www.metalfinishing.com/advertisers 355