MATERIALS HANDLING EQUIPMENTS
The Materials Handling equipments are classified into four basic types, viz., conveyors, cranes and hoists, trucks and auxiliary equipment.
These are gravity or powered devices, commonly used for moving loads from point to point over fixed paths. The various types of conveyors are:
(a) Belt conveyor- Motor driven belt, usually made of rubberised fabric or mental fabric on a rigid frame.
(b) Chain conveyor- Motor driven chain that drags materials along a metal slide base.
(c) Roller conveyor- Boxes, large parts or units loads roll on top of a series of rollers mounted on a rigid frame. The rollers may be powered or un powered.
(d) Pneumatic conveyor- High volume of air flows through a tube, carrying materials along with air flow. The other types of conveyors are bucket conveyors, screw conveyors, pipeline conveyor, vibratory conveyor, tube conveyor, trolley conveyor and chute or gravity conveyors. Advantages of conveyors are that they do not require operators, will move a large volume of products and are inexpensive to operate.
Cranes, Elevators and Hoists:
These are overhead devices used for moving varying loads intermittently between points within an area, fixed by supporting and binding rails:
(a) Cranes are devices mounted on overhead rails or ground level wheels or rails. They lift, swing and transport large and heavy materials. Examples are Gantry Crane, Jib Crane and Electrically Operated Overhead Crane (EOTC).
(b) Elevators are a type of cranes that lift materials- usually between floors of building.
(c) Hoists are devices which move materials vertically and horizontally in a limited area. They are used primarily, when materials must be lifted prior to being moved from one point to another. Example of hoists are air hoists, electric hoist and chain hoists.
These devices are used for moving mixed or uniform loads intermittently over variable paths. They are electric, diesel, gasoline or liquefied petroleum, gas powered vehicles equipped with beds, forks, arms or other holding devices. Examples are fork- lift trucks, pallet trucks, tractor with trailers, hand trucks and power trolleys.
These are devices or attachments used with handling equipment to make their use more effective and versatile. examples are ramps, positioners, pallets, containers and turn tables.
Miscellaneous Handling Equipments:
I. Pipe lines, which are closed tubes that transport liquids by means of pumps or gravity.
II. Automated guided vehicle (AGV) systems- These devices do not require operators and provide a great deal of flexibility in the paths they travel and the function they perform. The AGVs are controlled by signals sent through wires embedded in the floor or inductive tape on the floor surface. A remote control computer is needed to control the movement of AGVs.
III. Automatic transfer devices which automatically grasp materials, hold them firmly while operations are being performed and moved them to other locations.
IV. Industrial robots- A robot is a mechanism which has movable armlike projection with a gripper on the end that can perform a variety of repetitive tasks. Robots usually have a built â€“ in control that can be re- programmed and hence they are very versatile.
The process design and the principles of efficient materials handling provide the framework for selecting specific materials handling devices and the core of the materials handling system. Each of the handling devices discussed above has its own unique characteristics and advantages and disadvantages.
Evaluation of Materials Handling Performance:
Like any other materials activity, materials handling function should also be evaluated to judge its effectiveness. The performance of materials handling function can be evaluated with the help of several ratios such as the following:
1. Materials handling labor ratio.
2. Direct labor handling ratio.
3. Management/ Operation ratio.
4. Manufacturing cycle efficiency ratio
5. Space utilization efficiency ratio.
6. Equipments utilization ratio.
7. Aisle space potential ratio.
8. Materials handling personnel per 1000 factory employees.
9. Percentage of time lost by direct labor in materials .
10. Ratio of total number of moves to the total number of operations.
11. Percentage of usable cubic footage usually occupied.
12. Materials handling costs as percentage of manufacturing expenses