Metal Finishing Guide Book


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from the point that the dangler contact knob should touch the inside bottom of the barrel, continuing through the barrel hub (trunion) to the outside mounting point of the danglers. For short barrels or stiff dangler cable, the danglers can be extended beyond the midpoint of the barrel to provide contact at the opposite end of the barrel to insure that they remain submerged in the load. Special dangler contact knobs have been developed to help maximize performance when a standard configuration is not totally adequate. Custom Fig. 9. Knob-style, two-section door with knobs that are heavier can be specified center bar and partition. to help ensure they remain submerged in the workload. Also, special knobs with larger contact surface area are available where improved conductivity is important. Special dangler contacts can be ordered with the knobs made of stainless steel, titanium, or other materials. This is important when the mild steel knobs of standard danglers would be negatively affected by the type of plating chemistry used. Be aware that the alternate materials will probably exhibit lower conductivity. Other stationary cathode contact types, such as disk, cone, center-bar, strip, and button contacts, will usually do a better job of plating rods, long parts, and delicate parts. These types of cathode contacts are referred to as stationary because they are affixed to the barrel itself and rotate with the load. They are, therefore, stationary relative to the load. Stationary contacts are less abrasive to the work and generally exhibit fewer problems with entanglement. A plate-style contact is usually utilized in oblique-style barrel equipment. Barrel Doors There are several available styles and fastening methods for plating-barrel doors. Clamp-style doors have predominated over the years. This is because they are both quick and easy to operate. Knob-style doors are also greatly utilized (see Fig. 10). The threaded components of knob doors must be designed for efficient operation and durability to extend useful service life to minimize replacement. Divided doors can be furnished for ease of handling because they are smaller, being one half of the total barrel length each. Divided doors are used with partitioned barrels that have a transverse divider in the middle of the barrel for compartmentalization when necessary to plate/process different types of parts in the same barrel at the same time. There is, as in all things, diversity in barrel equipment and door operations. Most shops use and prefer clamp-style doors. Clamps are efficient because of quick installation and removal. Others operate successfully with knob-style doors. Many shops use more than one style barrel and door retainers. Because barrel-door security for part retention and efficient mounting, fastening, and opening of barrel doors is critical to operation of the entire line, much attention is given to this area. Some other door designs secure the workload within capturing edges of the door opening, rather than from the outside. With this type of design, the door carries the weight of the workload on the capturing edges, 428

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