Assembly Planbook - April 2008 - (Page 42) ASSEMBLY Conveyors The Intricacies of Accumulation Alpine and serpentine systems are assembly workhorses. anufacturers use accumulator conveyors to move a wide variety of products horizontally and vertically throughout their plants. An accumulator is any piece of equipment that allows product to amass in a production line so that upstream machines or operators can continue to function while downstream machines or operators are off line for whatever purpose. Accumulators have been around since assemblers first started using conveyors almost 100 years ago. Industries that rely on batching of products are some of the biggest users of the technology. Accumulator conveyors are typically used because products can rapidly be put back in line for further processing. Specifically, they can maintain the orientation of the product, accumulate products without any surface damage from the direct contact with each other, or redirect products to other conveyors to ease the congestion. There are four distinct approaches to accumulation: First in, first out (FIFO); last in, first out (LIFO); mass accumulation; and buffers. The first two approaches deal directly with the order that the manufacturer wants the product to be in at the conclusion of the manufacturing process. With FIFO and LIFO systems, however, customers need some method to track their products through the entire production process. Mass accumulation deals with accumulating vast quantities of product in M This closely packed alpine accumulating conveyor allows ascending and descending product on alternating levels. Crossover eliminates return chain and allows for a single drive motor. a specific area. But, it does not offer tracking capabilities and, as a result, many companies are moving away from this process. Buffers address the need for product to accumulate to accommodate the servicing or maintenance of a particular part of the manufacturing line. This allows the process to continue in spite of losing one or more pieces of machinery to either emergency or routine servicing. No matter what type of system is used, accumulators must be sized to accommodate the capacity required. Machine builders and systems integrators need four basic parameters to design an effective system: the shape, dimension and weight of the product; how the product will be presented; how much physical space exists in the manufacturing site; and the speed at which the product needs to be moved. Typically, most systems fall into two distinct categories: serpentine systems and alpine systems. Serpentine systems move horizontally, similar to the natural movement of a snake. Alpine systems move in a descending and ascending vertical pattern, similar to a roller coaster. In most cases, serpentine systems are required for products that must not accidentally tip over, while alpine systems are required when minimum floor space is available on an assembly line. However, exceptions to these rules do exist. Successful Applications There are many intricacies of accumulation. For instance, consider the following material handling applications. By Ray Johnson Lead Engineer Automated Conveying Systems Inc. Bloomington, MN 42 ASSEMBLY / April 2008 www.assemblymag.com http://www.assemblymag.com
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