Objectives of Material Handling Systems
(i) To minimize the cost of the product.
(ii) To minimize delays and interruptions by making
available the materials in the right quantity and at right time.
(iii) To increase the production capacity by effective
utilization of capacity.
(iv) To assure safety in material handling through
improvement in working conditions.
(v) To utilize material handling equipment to its
maximum level.
(vi) To prevent damages to materials under handling.
(vii) To lower investment in process inventory.
Principles of Material Handling Systems
The principle of material handling is described as
follows. All material handling activities should be planned. Plan a system
integrating as many handling activities as possible and co-coordinate the full
scope of operations (receiving, storage, production, inspection, packing,
warehousing, supply, and transportation). Make optimum use of cubic space. The
quantity, size, and weight of the load handled should be increased. Wherever
possible, gravitational force should be utilized to move material. The material
flow must be optimized by planning proper operational sequence and equipment
arrangement. The unnecessary movement and/or use of equipment must be reduced,
combined, or eliminated. The measures should be exercised for safety while
using handling methods and equipment. Use mechanical or automated material
handling equipment. Standardize the method, types, and size of material
handling equipment. Use methods and equipment that perform a variety of tasks
and applications. Consider all aspects of equipment and material to be moved
and the method to be utilized. Reduce the ratio of dead weight to the payload
in mobile equipment. Equipment designed to transport material should be kept in
use. Reduce idle time/unproductive time of both equipment and manpower. There
must be a plan for preventive maintenance or scheduled repair of all material
handling equipment. Replace obsolete handling methods/equipment when more
efficient methods/equipment will improve operation. Use handling equipment to
help achieve its full capacity and to improve production control, inventory
control, and another handling. Determine the efficiency of handling performance
in terms of cost per unit handled which is the primary criterion.
Selection of Equipments
The selection of material handling equipment is a critical decision as it affects both the cost and efficiency of the handling system. While selecting material handling equipment following factors need to be taken into consideration.
1. Properties of the material:
The type (whether it is solid, liquid or gas), size, shape, and weight or
amount of material to be moved are important issues that help to preliminary
eliminate equipments from the range of available equipments. The nature of the material,
viz. fragile, corrosive, or toxic implies certain handling methods and
containers preferable to others.
2. Layout of the building: The
availability of space for handling is another restricting factor for material
movement. Low ceiling heights may restrict the use of hoists or cranes, and the
presence of supporting columns in the path can limit the size of the
material-handling equipment. In multi-storied buildings for industrial trucks,
chutes or ramps are used. Building layout helps to decide the type of
production operation (continuous, intermittent, fixed position, or group) and
can indicate the equipment is more suitable than the others. Floor capacity as
well helps to select the best equipment.
3. Production flow:
In case of constant material flow between two fixed positions, fixed equipment
such as conveyors or chutes can be suitably used. If the flow is not constant
and the direction of material movement changes occasionally from one point to
another as several products are being produced simultaneously, moving equipment
such as trucks would be preferable.
4. Cost of handling:
Material handling cost helps to take a final decision of selecting equipment.
Several costs including initial investment and operating and maintenance costs
are the major cost to be considered. Comparison of the total costs for each
item of equipment under consideration helps to come up with a more rational
decision for the most appropriate choice.
5. Type of operations:
Equipment selection depends on the nature of operations like whether handling
is temporary or permanent, whether the flow is continuous or intermittent, and
material flow pattern is vertical or horizontal.
6. Engineering aspects:
Equipment selection also depends on engineering aspects like door and ceiling
dimensions, floor space, floor conditions, and structural strength.
7. Equipment reliability:
Reliability of the equipment and supplier reputation and the after-sales
service also plays an important role in selecting material handling equipments.
Evaluation of Material Handling System
The factors that help in the evaluation of material handling equipment are material handling system costs which include investment cost, labor cost, anticipated service hours per year, utilization, unit load carrying ability, loading and unloading characteristics, operating costs, and size requirements. Other factors to be considered are a source of power, conditions where the equipment has to operate, and other technical aspects. Therefore, choices of equipments in an organization will improve the material handling system through work-study techniques. They usually result in improving the ratio of operating time to loading time through palletizing, avoiding duplicative movements, etc. Obsolete handling systems can be replaced with more efficient equipments. The effectiveness of the system can be measured in terms of the time spent in handling and the total time spent in production. The cost-effectiveness can be measured by the expenses incurred per unit weight of material handled. The expenses and time factors as a base for performance help to take remedial measures. Other indices for evaluating the performance of handling systems are:
Equipment Utilization Ratio: The
equipment utilization ratio is an important indicator for judging the material
handling system. This ratio can be computed and compared with similar firms or
in the same over some time. To know the total effort needed for moving
materials, it may be necessary to compute the Materials Handling Labour (MHL)
ratio. This ratio is calculated as under:
MHL = Personnel assigned to materials / handling Total
operating workforce … (1)
To determine the material handling system to deliver
materials at a place with maximum efficiency, it is desirable to compute the direct
labor handling loss (DLHL) ratio. The ratio is:
DLHL = Materials handling time lost of labor / Total
direct labor time … (2)
The material movement to operation ratio is calculated
by dividing the total number of moves by the total number of productive
operations. This ratio helps to know workers with too many unproductive
movements because of poor routing. The efficiency of materials handling mainly
depends on the following factors:
(i) Efficiency of handling methods employed for
handling a unit weight through a unit distance.
(ii) Efficiency of the layout which determines the
distance through which the materials have to be handled.
(iii) Utilisation of the handling facilities.
(iv) Efficiency of the speed of handling. An effective
material handling system depends upon tailoring the layout and equipment to
suit specific requirements.
Material Handing Equipments
When a large volume has to be moved from a limited number of sources to a limited number of destinations fixed-path equipments like rollers, belt conveyors, overhead conveyors, and gantry cranes are preferred. For increased flexibility varied path equipments are preferred. Broadly material handling equipment’s can be classified into two categories.
(a) Fixed path equipments: Fixed path equipments move in a fixed path. For example, conveyors, monorail devices, chutes, and pulley drive equipments. A slight variation in this category is the overhead crane can move materials in any manner within a restricted area of its design. Overhead cranes have a very good range in terms of hauling tonnage and are used for handling bulky raw materials, stacking, and at times palletizing.
(b) Variable path equipments:
Variable path equipments have no restrictions in the direction of movement. For
example, trucks, forklifts, mobile cranes, and industrial tractors. The size of
these equipments is an important factor to be considered. Forklifts are
available in many ranges, they are maneuverable and various attachments are
provided to increase their versatility.
The choice of material-handling equipment among the
various possibilities that exist is not easy. In several cases, the same
material may be handled by various types of equipments, and the great diversity
of equipment and attachments available does not make the problem any easier. In
several cases, however, the nature of the material to be handled narrows the
choice. Material handling equipments may be classified into the following major
categories.
(i) Conveyors:
Conveyors are useful for moving material either continuously or intermittently
between two fixed workstations. They are mainly used for continuous or mass
production operations and are suitable for most operations where the flow is
more or less steady. Examples of conveyors include conveyors with rollers,
wheels, or belts to help move the material along. These may be power-driven or
may roll freely. Although conveyors are costly to install they are less
flexible and for two or more converges it is necessary to coordinate the speeds
at which these conveyors move.
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| Fig. 1: Belt Conveyor |
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| Fig. 2: Roller Conveyor |
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| Fig. 3: Wheel Conveyor |
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| Fig. 4: Screw Conveyor |
(ii) Industrial trucks:
Industrial trucks can move between various points and are not permanently fixed
in one place and thus are more flexible in use than conveyors. They are most
suitable for intermittent production and for handling various sizes and shapes
of material. Different types of a truck include petrol-driven, electric,
hand-powered, etc. Trucks have the advantage that it has a wide range of
attachments that increase their ability to handle various types and shapes of
material.
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| Fig. 5: Platform Truck Conveyor |
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| Fig. 6: Fork Truck |
(c) Cranes and Hoists:
The cranes and hoists can move heavy materials through overhead space. They can
usually serve only a limited area. There are several types of cranes and hoists
with various loading capacities. Cranes and hoists may be used both for
intermittent and continuous production.
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| Fig. 7: Jib Crane |
| Fig. 8: Bridge Crane |
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| Fig. 9: Chain Hoist |
Fig. 10: Electric Hoist
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| Fig. 11: Spiral Chute |
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| Fig. 12: Industrial Tractor |
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| Fig. 13: Electrical Hoist |
(d) Containers: Containers are either ‘dead’ or ‘live’. The dead containers include cartons, barrels, skids, pallets, etc. hold the material to be transported but do not move. The ‘live’ containers are wagons, wheelbarrows, or computer self-driven containers. Handling equipments of this kind can both contain and move the material and is usually operated manually.
(e) Robots:
These days in modern industries many types of robots are used to move
materials. They vary in size, function, and maneuverability. Robots are used
for handling and transporting material as well as performing operations such as
welding or spray painting. An advantage of robots is that they can perform in a
hostile environment such as unhealthy conditions or carry on arduous tasks such
as the repetitive movement of heavy materials.
Effective Utilisation of Equipments
The following guidelines help to design and cost reduction of the materials handling system:
(i) Material handling increases the production cycle
time and thus eliminates handling wherever possible. Ideally, there should not
be any handling at all.
(ii) logically sequence the operations so that
handling is unidirectional and smooth.
(iii) Use gravity wherever possible as it results in the
conservation of power and fuel.
(iv) Standardize the handling equipments to the extent
possible as it means interchangeable usage, better utilization of handling
equipments, and lesser spares holding.
(v) Install a regular preventive maintenance program
for material handling equipments so that downtime would be minimum.
(vi) The criteria of versatility and adaptability must
be the prime factor in the selection of handling equipments to ensure
investments in special-purpose handling equipments will be kept at a minimum.
(vii) Weight of the unit load must be maximum so that
each ‘handling cycle’ is productive.
(viii) Elimination of unnecessary movements and
combination of processes should be considered while installing a material
handling system.
(ix) Non-productive operations in handling, such as
slinging, loading, etc., should be kept at a minimum through appropriate design
of handling equipment.
(x) Location of stores should be as close as possible
to the plant which uses the materials.
(xi) Use of queuing technique can be very effective in
the optimal utilization of materials handling equipments.
(xii) The material handling system should be simple
and safe to operate.
(xiii) Avoid any wasteful movements-method study can
be conducted for this purpose.
(xiv) Ensure proper coordination through judicious
selection of equipments and training of workmen.
Plant Layout and Material Handling
There is a close relationship between plant layout and material handling. A good layout ensures minimum material handling and eliminates rehandling in the following ways:
(i) Material movement does not add any value to the
finished product, the material handling should be kept at a minimum though not
avoided it. This is possible only through the systematic plant layout. Thus a
good layout minimizes handling.
(ii) The productive time of workers will go without
production if they are required to travel a long distance to get the material
tools etc. Thus, a good layout ensures minimum travel for workmen thus
enhancing the production time and eliminating the hunting time and traveling
time.
(iii) Space is an important criterion. Plant layout
integrates all the movements of men, and materials through a well-designed
layout with a system. It helps to keep material handling shorter, faster, and more
economical. A good layout reduces the material handling system.
(iv) Good plant layout helps in building efficient
material handling the material backtracking, and unnecessary workmen movement
ensuring effectiveness in manufacturing. Thus a good layout always ensures
minimum material handling.