Metal Finishing Guide Book

2011-2012 Surface Finishing Guidebook

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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 sta- tionary 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 exhib- it fewer problems with entanglement. A plate-style contact is usually utilized in oblique-style barrel equipment. Fig. 9. Knob-style, two-section door with center bar and partition. 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 effi- cient operation and durability to extend useful service life to minimize replace- ment. 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 instal- lation 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 atten- tion is given to this area. Some recent other door designs secure the workload with- in 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, rather than the retaining clamps or knobs. This type of design is good for very small parts or workpieces that cumulatively pry and wedge into crevices. Other modern innovations to automate operation of plating barrel doors are sometimes utilized to eliminate manual labor for opening, loading, and closing. In equipment systems of this type the barrel door usually remains an integral functional component of the barrel assembly rather than a separate item to be manually manipulated. In addition to the inherent labor savings, the safety of the overall fin- ishing operation is increased because significant labor interaction with the equip- ment is eliminated. Automatic barrel operation translates into system automa- tion, which can greatly enhance efficiency and eliminate costs. Other additional automated aspects of barrels, hoist systems, and related material handling equipment can be configured in which the equipment automatically sizes and weighs workloads, loads the barrels, closes the barrels for processing, opens the barrels, and unloads the finished work to conveying equipment for further processing or drying (see Fig. 4). This is the ultimate evolution of a barrel-finishing system. 332

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