Products Finishing magazine is the No. 1 industrial finishing publication in the world. We keep our readers informed about the latest news and trends in plating, painting, powder coating, anodizing, electrocoating, parts cleaning, and pretreatment.
Issue link: https://pf.epubxp.com/i/866825
PRODUCTS FINISHING — PFonline.com 25 New contact and power distribution systems are being designed to meet those technical demands, however, as well as to address issues of chemical corrosion and contact cleaning. No one contact design would work perfectly with every plating application, however, as there are many different tank construction and design philosophies. The most common flight bar shape, for example, is rectangular, in a variety of thicknesses and heights, and they demand specialized contacts in order to work efficiently. In some cases, extreme chemical exposure requires special consideration to ensure proper contact over a longer period of time. And the availability of adequate space for contact placement on a tank rim may also require a custom design or modification. Considerations for a New System There are a number of important factors to consider in selecting new contacts: • Amperage or current requirement. • Length of each cycle time. • Weight and dimensions of flight bars with racks. • Pr ofile and dimensions of flight bars' contact areas. • Special or e xtreme chemical exposure. • Possible mechanical forces. • P ossible tank movement. • Available space for installation. A fire in a plating plant is not unheard of, and many workers in these shops have smelled and felt the heat from overheated f light bars and contact saddles. It's not uncommon for f light bars, contact saddles, base plates, cables and electrical bus bars to be warm to the touch, but hot is unacceptable, and will put the plant and personnel at high risk for injury. High heat is generated from the rectifier to the bus bars, in cables from the bus bars to the contacts, as well as in the interface between the f light bar and the contact saddle. Cables, particularly if they contain too small a cross section of copper and are inadequately sized, or if they are frayed, worn, chemically burned or have improperly crimped lugs, are many times the culprit when fire erupts. Often, the single most critical area of high heat generation is at the point where the flight bar and the contact saddle meet during the transfer of electrical power; in the case of a V-block contact saddle and a round bar, this interface would be only two thin lines of contact. In addition to temperatures high enough to cause fires or burn employees, a great amount of energy and current are lost in travelling to the parts on the rack, and this can adversely affect the time and deposition rate of plating. Many shops use an upside-down J channel or shepherd's hook design at the top end of the racks' arms for hanging off the bus bar. This is also an area of little surface contact, which leads to a reduced current flow. Rack contacts with a V design ensure that the contact area is large and consistent, easily alleviating this problem. A new and clean electrical contact system may perform well, but after a year or so of use, it will perform much differently. Hand cleaners can quickly clean finger contacts or other contact surfaces. This contact block system is relatively inexpensive and can be designed in a variety of sizes ranging to 5,000 amps per contact block. CONTACT SYSTEM