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Introduction to logistics_engineering


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Introduction to logistics_engineering

  1. 1. Material Handling System 7-97.3 Material Handling EquipmentIn this section we list the various equipment that actually transfers materials between different stages ofprocessing. In manufacturing companies, various material handling devices (MHDs) are used andtogether they constitute a material handling system (MHS). If we regard materials as the blood of amanufacturing company, then MHSs are the vessels that transport blood to the necessary parts of thebody. The major function of an MHS is to transport parts and materials; this type of activity does notadd any value to products and can be regarded as a sort of “necessary waste.” However, in some cases,MHSs perform value-added activities. The MHS is an important subsystem of the entire manufacturingsystem; it interacts with the other subsystems. Thus, when we try to design or run an MHS, we shouldlook at it from a system perspective. If we isolate an MHS from other subsystems, we might get an opti-mal solution for the MHS itself, but one that is suboptimal for the entire system. In the following sections, we will first introduce seven basic types of MHDs. We then discuss how tochoose the “right” equipment and how to operate equipment in the “right” way.7.3.1 Types of EquipmentSeveral different types of MHDs are available for manufacturing companies to choose. These companiesneed to consider a number of factors including size, volume of loads, shape, weight, cost, and speed. Asmentioned in the introduction, we need to consider the entire system when we try to make our choices. Ofcourse, in order to make good decisions, we need to have an overview of different MHDs. There are sevenbasic types of MHDs [1]: conveyors; palletizers; trucks; robots; automated guided vehicles; hoists, cranes,and jibs; and warehouse material-handling devices. We will introduce these types one by one briefly. ConveyorsConveyors are fixed path MHDs. They are only used when the volume of material to be transported islarge and relatively uniform in size and shape. Depending upon the application, many types of convey-ors are possible, including: accumulation conveyor, belt conveyor, bucket conveyor, can conveyor, chainconveyor, chute conveyor, gravity conveyor, power and free conveyor, pneumatic or vacuum conveyor,roller conveyor, screw conveyor, slat conveyor, tow line conveyor, trolley conveyor, and wheel conveyor.Pictures of a few conveyors are shown in Figure 7.8. The above list is not complete. Readers can refer for additional information on conveyors (and other types of MHDs).FIGURE 7.8 Various conveyor types and their applications in material movement and sorting (a–d). (Courtesy ofFKI Logistex, Dematic Corporation. With permission.)
  2. 2. 7-10 Introduction to Logistics EngineeringFIGURE 7.8 (continued)
  3. 3. Material Handling System 7- PalletizersPalletizers are used to palletize items coming out of a production or assembly line so that unit loadscan be formed directly on a pallet. Palletizers are typically automated, high-speed MHDs with a user-friendly interface so that operators can easily control them. Another type of equipment that is relatedto a pallet is a pallet lifting device. This MHD is used to lift and/or tilt pallets and raise or lower heavycases to desired heights so that operators can pick directly from the pallets. A palletizer is shown inFigure TrucksTrucks are particularly useful when the material moved varies frequently in size, shape, and weight;when the volume of the parts/material moved is low; and when the number of trips required for eachpart is relatively few. There are many different types of trucks on the market with different weight, cost,functionality, and other features. A sample is shown in Figure RobotsRobots are programmable devices that mimic the behavior of human beings. With the development ofartificial intelligence technology, robots can do a number of tasks not suitable for human operators.However, robots are relatively expensive. But they can perform complex or repetitive tasks automati-cally. They can work in environments that are unsafe or uncomfortable to the human operator, workunder extreme circumstance including very high or low temperature, and handle hazardous material. Automated Guided VehiclesAutomated guided vehicles (AGVs) have been very popular since they were introduced about 30 yearsago and will continue to be an important MHD in the future. AGVs can be regarded as a type of spe-cially designed robot. Their paths can be controlled in a number of different ways. They can be fullyautomated or semiautomated. They can also be embedded into other MHDs. A sample of AGVs andtheir applications is illustrated in Figure 7.11.FIGURE 7.9 Palletizer. (Courtesy of FKI Logistex, Dematic Corporation. With permission.)
  4. 4. 7-12 Introduction to Logistics EngineeringFIGURE 7.10 Order-picking trucks. (Courtesy of Crown Corporation. With permission.) Hoists, Cranes, and JibsThese MHDs use the overhead space. The movement of material in the overhead space will not affect theproduction process and workers in a factory. Typically, these MHDs are expensive and time consuming toinstall. They are preferred when the parts to be moved are bulky and require more space for transportation(Fig. 7.12). Warehouse Material-Handling DevicesWarehouse material-handling devices are also referred to as storage and retrieval systems. If they arehighly automated, they are referred to as automated storage and retrieval systems (AS/RSs). The primaryfunctions of warehouse material-handling devices are to store and retrieve materials as well as transportthem between the pick/deposit (P/D) stations and the storage locations of the materials. Some AS/RSsare shown in Figure 7.13.FIGURE 7.11 Application of AGVs (a and b).
  5. 5. Material Handling System 7-13FIGURE 7.11 (continued) Xijkl number of units of part type i to be transported from machine j to k using MHD lFIGURE 7.12 Gantry crane and hoist (a and b). (Courtesy of North American Industries and Wallace ProductsCorporation. With permission.)
  6. 6. 7-14 Introduction to Logistics EngineeringFIGURE 7.12 (continued)FIGURE 7.13 Automated storage and retrieval systems (AS/RSs). (Courtesy of Jervis B. Webb Company.With permission.)