Powder Coated Tough - Fall/Winter 2007 - (Page 34) Powder Automation Selecting the appropriate equipment is very important. The product mix to be identified determines the sensing method needed. Photo Eyes. Most systems use photo eyes for identifying the vertical length of the product. When the product breaks the photo eye beam, input is registered in the PLC. The PLC uses this input data from the group of photo eyes to determine the zone or style configuration. In a style-based system, the photo eyes are arranged to detect surfaces on the product that are unique to that particular style. There are cases where photo eyes are not adequate to sense the product reliably. Typically, a photo eye beam is broad and forgiving for alignment. If the product to be coated is very narrow, the photo eye beam may “bleed” around the product. Apertures can be installed on the photo eye lenses to narrow the beam to increase sensing resolution. Laser type sensors are also available to increase sensing reliability. Light Curtains. Another case where photo eyes may not be practical are when narrow products are presented in a horizontal manner. If a product is to be recognized, it must break the photo sensor beam. If the product passes between the beams, it is not sensed. Light curtains are often employed to resolve this issue. A light curtain is an array of tightly spaced photo eyes, typically 3/8" to 3/4" apart, and can sense over a large, linear area. Light curtain controllers supply information to the PLC. This information can be supplied in many forms, from a linear voltage signal to serial data. Using light curtains is becoming more popular due to the product sensing flexibility. Hanger Flags. In style based systems it is sometimes not possible to sense differences between products reliably. The product mix may have only minor differences that the photo sensors or light curtains cannot detect. In these cases, a hanger flag can be employed. This flag is designed to be detected as a unique style relating to the product on the hanger. Normally, this flag is a flat plate with a series of holes. The number of holes determines the number of styles available to be sensed. Photo eyes are arranged to detect the presence or absence of the holes and a style number is determined through the binary equivalent of the hole pattern. For instance, a plate with a fourhole pattern can represent up to 16 styles, whereas a plate with eight holes can represent up to 256 styles. Additional photo eyes are employed to detect the presence of the product on the hanger. This is a very reliable method, but it does require the proper flag to be matched with the product, typically done at the loading area. Another method of style detection for the coating process is to retrieve the style type from the conveyor system. When the product is loaded, the style information is entered into the conveyor system PLC and tracked throughout the line. When the product enters the powder-coating booth, this style information is retrieved by the powder booth PLC from the “Reliability, that’s what HERR Paint Systems deliver.” Metals, wood, plastics. HERR provides reliable systems for all applications. • Turnkey Finishing Systems • Powder, E-Coat, Liquid • Equipment Components • System Relocation, Retrofits • Service & Maintenance • Spare Parts Reliability. Affordability. Value. Why great companies choose HERR Industrial. Visit our website to learn more: www.herrindustrial.com 1-800-700-HERR Reliability+Affordability=Value 34 Powder Coated Tough http://www.herrindustrial.com http://www.herrindustrial.com
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