Refresher course on sortation conveyors
Here's a guide to basic types of sortation conveyors and systems, where they are used, and who makes them.
By Ray Kulwiec -- Modern Materials Handling, 2/1/1999
Sortation is the process of arranging items, cartons, or products by category-i.e., shipping destination in a distribution application, or work-in-process sequence in progressive assembly. Items handled include cartons, containers, totes, bags, packaged sub- assemblies, and parcels.In materials handling applications, this function is usually accomplished with one of various types of sortation conveyors. The basic types are shown in the accompanying table, "Sortation conveyor equipment guide."
Sortation conveying is one step in the overall sortation process. Other steps in the process include merge and induction beforehand, and takeaway after sortation. And, in a distribution environment, some type of order picking, say to a takeaway conveyor, typically precedes the merge function.
The merge step thus involves one or multiple infeed lines, typically in the form of accumulation conveyors. Using various conveyor features such as skewed rollers or indexing belts, the merge system coordinates and monitors all infeed flow to the main conveying line leading to sortation. In doing so, it maintains a constant flow of items to keep the sortation system efficiently filled.
Induction follows merge and is the step that identifies product destination and provides for the necessary gap between items to allow for efficient sortation. Gap control is accomplished with various means of controlling belt speeds. Carton or item destinations are typically determined with bar-code scanners.
Sortation itself consists of using various devices, as shown in the accompanying table, that range widely in complexity and operating speed. The goal of sortation is to improve productivity, upgrade customer service, reduce space needs, and increase control over inventory and operations.
Takeaway is the final step of the sortation process. Its function is to move products from the sortation conveyor without affecting sortation discharge rate. Powered takeaways include roller and belt conveyors, and gravity takeaways are typically gravity roller conveyors. Gravity chutes also are used, in cases where product orientation and/or fragility are not concerns.
Today sortation conveyors are the backbone of many efficient and productive materials handling operations. They include applications as diverse as baggage handling (see "World's largest integrated baggage handling system opens in Hong Kong," MMH, 8/98, p. 55) and video cassette distribution (see "High-tech DC: just the right ticket for Blockbuster Video", MMH, 10/98, p. 34).
Modern Materials Handling is grateful to the Conveyor Product Section of Material Handling Industry of America (MHIA) for use of some of the information and illustrations in this article. This organization has released a CD-ROM on conveyor sortation, which is available for $20.00. For further information, contact MHIA, 8720 Red Oak Blvd., Suite 201, Charlotte, NC 28217, 1-800-345-1815, or www.mhia.org.
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