MATERIAL HANDLING SYSTEM

    Material handling systems provide transportation and storage of materials, components and assemblies. Material handling activities start with unloading of goods from materials from delivery transportation, the goods then pass into storage, onto machining, assembly, testing, storage, packaging and finally loading into transport. Each of these stages of the production

Process requires a slightly different design of handling equipment.

   

    Therefore, material handling is simply defined as the movement, storage, control and protection of materials, goods and products throughout the process of manufacturing, distribution, consumption and disposal. The material handling industry manufactures and distributes the equipment and services required to implement material handling systems.

     Material handling systems have been mainly categorised as follows

v  Bulk material handling systems

v  Engineered material handling systems

v  Industrial truck material handling systems

v  Storage material handling systems

Two material handling systems belonging to each category are as follows

Bulk material handling system

v  Conveyor belts

v  Bucket elevators

Industrial truck material handling system

v  Forklift

v  Pallet jack

                                                                                                   

Storage material handling system

v  Shelves

v  Pallet racks

Engineered material handling systems

v  Automated guided vehicles

v  Automated storage and retrieval system

             

           

     Looking at their names application and uses, parts, operation and diagrams and pictures.

Bulk material handling systems

v  Conveyor belts

The conveyor belt is mainly used in the manufacturing, food processing and heavy industries for transporting industrial and agricultural materials, such as grain, coal, ores, etc. In large quantities of material, or in packaged form.

It is also used in conveyor transport such as moving sidewalks or escalators, as well as on many manufacturing assembly lines

     The conveyor belt is made up of the following parts.

·         Two pulleys

·          Conveyor belt

 The conveyor belt operates by powering one or both of the pulley. It consists of two or more pulleys with a continuous loop of material i.e. the conveyor belt that rotates about them. One or both of the pulleys are powered, moving the belt and the material on the belt forward s. By doing this, the belt and the material on the belt moves. The powered pulley is called the drive pulley while the unpowered pulley is called the idler. Material flowing over the belt may be weighed in transit using a beltweigher.

 
                    

  Figure 1: Belt conveyor                                                                 Figure 2: Two pulleys been

                                                                                                              Driven by a belt                                                                   

v  Bucket elevators

They are used for hauling flowable bulk materials vertically. It is mainly used for carrying difficult materials at slow speed. Bucket elevators can elevate a variety of bulk materials from light to heavy and from fine to large lumps in the various industries and manufacturing firms.

       Bucket elevators consist of the following parts:

·         Bucket

·         Belt

·         Pulley

·         Electric motor

·         Discharge chute

              OPERATION

       Bucket elevators are of two types, the vertical depends entirely on the action of centrifugal force to get the material into the discharge chute and runs at speeds relatively high. Inclined elevators with buckets spaced apart or set close together have discharge chute set partly under the head pulley. Since they don't depend entirely on the centrifugal force to put the material into the chute, the speed may be relatively lower. They pick up their load from a boot, a pit, or a pile of material at the foot pulley. The Bucket is set close to the belt with little or no clearance between them. It has top and down pulleys. The top pulley is driven by an electric motor .A diverter at the top of the elevator allows the grain to be sent to the chosen bin.

     

Figure 3: Bucket elevator

           Industrial truck material  handling system

v  Forklift

Forklift is a powered industrial truck used to lift and transport materials

        PARTS

·         Truck frame

·         Counterweight

·         Cab

·         Overhead Guard

·         Power source

·         Tilt cylinders

·         Mast

·         Carriage

·         Attachments

·         Tires

·         Load back rest

                                       OPERATIONS

  Forklifts derive their power from two intertwining mechanisms: a pair of hydraulic cylinders and a pair of roller chain pulleys. The lift handle is wired to an electrical air pump at the base of the machine. When pressed, the handle activates the air pump, which draws in outside air through a filter and forces it into a tube leading to both hydraulic cylinders.

     Air enters the bottom of the cylinder through a special "one way" valve that allows gases to enter without leaking back out.  This pressure, applied across the area of the piston head, results in a net upward force. This upward push causes the piston to move up, which increases the volume of the gas and decreases the pressure. This automatically leads to a physical equilibrium where, at a given lift height, the force from the gas equals the downward force of the forklift's load.

   To move the load higher, the operator pushes the handle forward. This signals the machine to pump more air into the cylinders. To lower the load, the operator pulls the handle back, which triggers a special valve to gently release gas from the cylinder. Forklift can be controlled by turning the steering wheel, the wheels on the rear axle turn back and forth.

 The lifting controls consist of two levers one for lifting the fork up and down as well as one for tilting the load back and forth.  The tilting functionality, however, is slightly different. At the base of the masts are two pairs of additional hydraulic cylinders that attach to the base of the vehicle. When the "tilt" handle is moved forward, air is pumped into the chamber. This increase in pressure pushes the piston head and causes the masts to "lean away" from the vehicle's body.

Figure 4: Forklift

v  Pallet jack

Pallet jack is a tool used to lift and move pallet

           PARTS

·         Wheels

·         Fork

·         Hydraulic jack

        OPERATIONS

The front wheels are mounted inside the end of the forks, and as the hydraulic jack is raised, the forks are separated vertically from the front wheels, forcing the load upward until it clears the floor.

                      

Figure 5 manual pallet jack

STORAGE MATERIAL HANDLING SYSTEM

v Shelves

         APPLICATION

·         Home

·         Business

·         Stores

USES

Shelves are mainly used to hold items of value that are being displayed, stored, or offered for sale.

    

      DESCRIPTION

 Shelves are normally made of strong materials such as wood, bamboo or steel, though shelves can be made of glass or plastic for light-weight objects. It is moulded either in

rectangular form or in a squared form and attached to a wall or vertical surface

                                           Figure 6:  Shelve

v  Pallet racks

APPLICATIONS

·         Home

·         Business

·         Stores

       USES

Pallet racks are material handling storage aid system designed to store materials on pallets.

      PARTS

·         Load beams

·         Upright frames

·         Diagonal brace and horizontal brace

·         Pallet support

·         Shims

·         Wire decking

·         Footplate

·         Row spacers

·         Guard rails

·         Wall ties

·         Column protectors

    OPERATION

The metal skate wheels contain an anti-backup device which keeps the pallets moving towards the picking position.  Additional wheels are been added for more pallet support and

the centre lines of the skate wheels are increased for heavier loads. 

                                  Figure7: Pallet rack

v  Automated guided vehicle (AGV)

Automated guided vehicles are mobile robot that follows markers or wires in the floor, or uses vision or lasers.

       They are mostly used in industrial applications to move materials around a manufacturing facility or a warehouse. They can tow objects behind them in trailers to which they can autonomously attach. The trailers can be used to move raw materials or finished product. The AGV can also store objects on a bed and can also be used for transporting materials such as food and medicine. AGVs are commonly used to transport raw materials such as paper, steel, rubber, metal, and plastic. This includes transporting materials from receiving to the warehouse, and delivering materials directly to production lines.

      Parts of the automated guided vehicle includes

•           Lasers

•           Guide tape

•           Laser target navigator

•           Gyroscopic navigator

•           Steering control

•           Wire

•           Robot

      The AGV operates by using a wired sensor which is placed on the bottom of the robot and is placed facing the ground. A slot is cut in the ground and a wire is placed approximately 1 inch below the ground. The sensor detects the radio frequency being transmitted from the wire and follows it. It makes use of tape for the guide path. It is fitted with the appropriate guide sensor to follow the path of the tape. The AGV carries a laser transmitter and receiver on a rotating turret. The laser is sent off then received again the angle and distance are automatically calculated and stored into the AGV’s memory. The AGV has reflector map stored in memory and can correct its position based on errors between the expected and received measurements. It can then navigate to a destination target using the constantly updating position.  It makes use of modulated laser light which gives greater range and accuracy over pulsed laser systems. Transponders are embedded in the floor of the work place. The AGV uses these transponders to verify that the vehicle is on course. It has a gyroscope which enable it to be able to detect the slightest change in the direction of the vehicle and corrects it in order to keep the AGV on its path.

The AGV uses differential speed control. In this method there are two sets of wheels being driven. Each set is connected to a common drive train. These drive trains are driven at different speeds in order to turn or the same speed to allow the AGV to go forwards and or backwards. Steered wheel control enables the governor to tow.

  Figure: 8 Automated guided vehicle                   Figure: 9 A unit load vehicle for

                                                                                            Steel plates                      

 

v  Automated storage and retrieval system (ASRS or AS/RS)

Automated storage and retrieval system is mainly made up of a variety of computer-controlled methods for automatically placing and retrieving loads from specific storage locations.

      Automated storage and retrieval system are mainly used in applications where there is high volume of loads being moved into and out of storage. It can be used with standard loads.

     It parts includes.

•           Trays

•           Chains or driver

•           Storage machine

•           Retrieval machines

•           Shuttles

•           Storage cabinet

 

               OPERATION

   Items are placed on trays or hang from bars, which are attached to chains or drives in order to move up and down. The shuttles that make up the system travel between fixed storage shelves to deposit or retrieve a requested load. The shuttle move along the ground to telescope up to the necessary height to reach the load, and can store or retrieve loads that are several positions deep in the shelving. Stations are provided to precisely position inbound and outbound loads for pickup and delivery by the crane.

 When a tray is requested, either by entering a tray number in the built in control pad or by requesting a part through software, an extractor travels vertically between the two columns of trays and pulls the requested tray from its location and brings it to an access point. The operator then picks or replenishes stock and the tray is returned to its home upon confirmation.

                                     Figure :10  Automated storage and retrieval system