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ارجوكم اريد بحث عن ....................Material Handling

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    ارجوكم اريد بحث عن ....................Material Handling

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    handling materials

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    السلام عليكم

    PART I: MATERIAL HANDLING PRINCIPLES AND EQUIPMENT


    According to the Material Handling Institute (MHI), "material handling embraces all of the basic operations involved in the movement of bulk, packaged, and individual products in a semisolid or solid state by means of machinery, and within the limits of a place of business." First, material handling involves the movement of material in a horizontal (transfer) and vertical (lifting) direction, as well as the loading and unloading of items. Second, materials moved include raw material to workstations, semi-finished products between workstations, and removal of finished products to their storage locations. Third, the selection of equipment is an important activity of designing a material-handling system. Fourth, the term bulk indicates that materials are moved in large, unpacked volumes (such as sand, sawdust, and coal). Fifth, using machinery for handling material is the preferred method, although the investment might be high. A summary of the objectives of material handling [Sule, 94] are:

    1. Increase efficiency of material flow
    2. Reduce material-handling cost
    3. Improve facility utilization
    4. Improve safety and working conditions
    5. Facilitate the manufacturing process
    6. Increase productivity

    Material handling can account for 30-75% of production costs and can reduce operational costs by 15-30%. It affects building requirements, departmental arrangements, and production time. For a list and short description of material handling principles see Table 6.2. There are three main types of handling equipment: conveyors, cranes, and trucks. Section 6.6 of the textbook provides additional types. A comprehensive list and brief descriptions of typical material-handling equipment can be found on pages 176-226. A similar list can be found in Sule 94 [Section 8.14].

    The 10 Principles of Material Handling

    A principle can be defined as a general rule, fundamental, or statement of an observable fact. In the field of material handling principles can be invoked to analyze, plan and manage material handling systems. In 1968 CIC-MHE published a preliminary set of principles, which have undergone a sequence of reorganizations and redefinitions during the last three decades, as a result of additional knowledge generated by a substantial number of practitioners in the field. In essence, the material handling systems can be considered as general guidelines that can be used to compare and evaluate material handling systems. The following list includes the 10 most important principles used today in the field:

    Planning Principle:A material handling facility should be the result of a cohesive and structured unit of specific courses of action (i.e., a plan) to determine what material needs to be moved, when and where it will be moved, and how it will be done.

    Standardization Principle: Methods, equipment, control devices, and software should be standardized without reducing the level of performance and the need for flexibility.

    Work Principle: Material handling flow should be as low as possible within the requirements demanded by the effectiveness and efficiency of a material handling system. “The best flow is no flow.”

    Ergonomic Principle: Material handling activities should be designed and proper equipment chosen after taking into consideration human capabilities and limitations to enhance the level of safety and working conditions.

    Unit Load Principle: The amount of material to be moved or stored as a unit should be sized and configured according to the specific needs and objectives of the material handling facility.

    Space Utilization Principle: The cubic space should be used as effectively and efficiently as possible.

    System Principle: A material handling system consists of a collection of elements working and interacting together as a unit to perform a common function. Alternatively, material handling activities and facilities are integrated to form a coordinated operational system including receiving, inspection, storage, production, assembly, packaging, load unitizing, order selection, shipping, transportation and returns handling.

    Automation Principle: The level of mechanization and automation depends on the specific operational requirements and financial capabilities of each situation.

    Environmental Principle: Environmental impact and energy consumption should be important factors in the selection of a material handling system.

    Life Cycle Cost Principle: In the economic analysis of a material handling system all cash flows need to be considered along the service life of the system.

    Conveyors

    Conveyors are used for machine-to-machine movement, assembly operations, department-to-department movement, and linkage of production with automated storage and retrieval systems along fixed paths. The American Material Handling Society lists 57 types of conveyors. Conveyors move materials continuously over a fixed path. Typical functions of conveyors are:

    · Transportation
    · Storage
    · Pacing

    Conveyors have adjustable speeds, their capacity is high, they can combine transferring with processing and inspection, can serve as temporary storage facilities between workstations, can be controlled automatically, and allow the utilization of the cube through the use of overhead conveyors. However, they can serve limited areas because of the fixed paths, can generate bottlenecks if not properly controlled, and hinder the movement of mobile equipment on the factory floor.

    Monorails, Hoists, and Cranes

    Cranes and hoists are overhead equipment for moving loads intermittently within a limited area. Bridge cranes, jib cranes, monorail cranes, and hoists are examples of this basic type of equipment. Lifting equipment is also generally capable of transferring material. It can handle very heavy loads, and it can be used for loading as well as unloading. However, it is expensive, it serves a limited area, and its utilization may not be very high.

    Industrial Trucks

    The purpose of these trucks is to carry loads over varying paths. There are several types, such as lift trucks, hand trucks, fork trucks, trailer trains, and automated guided vehicles. Several types of trucks are capable of loading, unloading and lifting, as well as transferring. However, generally, they cannot handle very heavy loads, their capacity per trip is limited, must be driven by an operator, and cannot combine handling with processing and inspection.

    Equipment Description

    A. Conveyors


    Chute Conveyor

    A chute conveyor is a slide, generally made of metal, which guides materials as they are lowered from a higher-level to a lower-level workstation. The shape of the chute can be straight or spiral to save space.

    Wheel Conveyor

    This kind of conveyor consists of wheels attached to side rails supported by a steel frame. The load is carried on the wheels, each of which rotates about a fixed axis. It can be gravity-operated or power-driven. Wheels can be made of steel, aluminum, or plastic. Most flat-bottomed surfaces will convey satisfactorily on wheel conveyors. If the part does not have a flat surface, it may ride in a box or on a small pallet.
    Roller Conveyor

    A roller conveyor consists of rollers attached to side rails supported by a steel frame. The load is carried on the rollers, each of which rotates about a fixed axis. The type of roller (steel, rubber, and wood) and the spacing of rollers depend on the type of load to be carried. It can be gravity-operated or power-driven. Gravity-operated conveyors have a slight downward slope (pitch), commonly equal to 3-6 inches per 10-ft section. On the power-driven conveyor, some of the rollers are driven by chains or belts to provide the motion for the material on the conveyor.
    Pneumatic Tube System

    A pneumatic tube system consists of a cylinder in which messages or small items are carried over a predetermined path by compressed air or vacuum. The requirement for a constant pressure or vacuum results in high operating and maintenance costs for large, complex systems.

    Belt Conveyor

    A belt conveyor is an endless belt, driven by power rollers or drums at one or both ends and supported by flat beds or rollers. These rollers can provide a flat belt or a through conveyor. The belt is made of rubber, woven wires, metal or fabric. Occasionally it can be magnetic. Portable belt conveyors are so popular they come in standard units.
    Chain Conveyor

    With a chain conveyor, an endless chain transmits power from a motor to a carrying surface or unit. The carrying unit can be quite varied. Specific examples of chain conveyors are flight conveyors (flights are "blades" attached perpendicular to the chain), apron conveyors, bucket conveyors, and slat conveyors. An apron conveyor is similar to a slat conveyor, the only difference being the partial overlapping of the slats in the apron conveyor to provide a continuous moving surface. A special type of chain conveyor is the trolley or tow conveyor (a powered trolley on a rail). The trolley is connected to a motor by a chain or cable.
    Conveyor Control

    The control system has four basic elements: input interface, logic, memory, and output interface. The input interface takes voltages or currents from switches, relays, and temperature or pressure sensors; it then transforms these power signals into power levels suitable for the control system logic device. The logic takes the input and actuates devices in specific sequences. The output electromechanical devices and motors generally need line voltage; the output interfaces boosts the low-powered logic commands.

    Accessories

    A variety of accessories is available. Some of the most widely used accessories are: pallets, boxes, tote pans, skids, and optical code or bar code readers. A pallet is a platform on which material can be stacked in unit loads and handled by lifting equipment such as the forklift. A box is a portable container (11.5 in x 2.75 in x 2.75 in to 71 in x 18 in x 19 in) in which parts or material can be stored in unit loads. Boxes are made of cardboard, wood, plastic, or metal. A tote pan is a portable container (16.75 in x 10.75 in x 3 in to 46 in x 34 in x 33 in) that is smaller in size than a box. It is used to carry small parts. Tote pans are made of plastic, metal, or wood. They can be moved either by power-driven or hand-operated devices. A skid is similar to a pallet, except that the construction does not permit stacking of loaded skids on top of each other. They are made of metal or heavy wood and are used to store and move heavy and/or bulky materials. They can be moved manually or mechanically and can be made portable by attaching two wheels on one end and a carrying dolly at the other. An optical or bar code reader is a hand-held device that can read an optical code to identify the product or handling device on which the code is affixed. They can be used to keep track of inventory or products as items are moved from station to station.

    B. Hoists and Cranes

    Overhead Monorail

    A track to transport carrying devices such as trolleys and hooks. The track itself can form a closed loop. Often used in transporting units to spray paint booths or baking ovens. Generally placed at 8 to 9 feet from floor. In the following diagram, we show a monorail telpher. A telpher is a light car suspended from and running on aerial cables. Usually, they are propelled by electricity.
    Hoist

    A hoist is a lifting device attached to monorails, cranes, or a fixed point. A hoist can be powered manually or by electric or pneumatic motors. A hoist is a lifting device itself. It is frequently named by the kind of crane to which it is attached. There are three major types: chain hoist (serves a fixed spot directly beneath the hoist), monorail hoist (free to move along an overhead rail), jib hoist (serves any area circumscribed by the jib in a 360-degree rotation).

    Cranes

    A crane is a piece of overhead equipment consisting of a boom or bridge along which a handling device, such as a hoist, traverses. A jib crane consists of a lifting device (hoist) traveling on a horizontal boom mounted on a vertical mast (pillar jib crane, bracket jib crane, cantilever jib crane). The horizontal boom can rotate to achieve a wide range of coverage. A bridge crane consists of a lifting device mounted on a bridge, which is supported at each end by tracks riding on or suspended from runways installed at right angles to the bridge. Variations include: stacker crane, tower crane, gantry crane. A tower crane consists of a hoist that travels on a horizontal boom attached at one end to a vertical post, with the other end of the boom being supported by a guy line to the top of the post. A gantry crane is basically a bridge crane with the boom supported at one or both ends by vertical gantry legs traveling on rails installed at ground level (instead of on an overhead runway). A monorail crane consists of a beam, which supports a carrying device mounted on wheels, which run along the beam. A stacker crane is one with a vertical beam suspended from a carriage, mounted on a device similar to a bridge crane, and is fitted with forks or a platform to permit it to place items into or retrieve items from storage racks on either side of the aisle it traverses.



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