The process of minimizing the physical and perceptual loads imposed on people engaged in any type of work is known as Motion Economy. It could be in the office, the shop floor, the kitchen or at the driving wheel. This science leads to better design of equipment, jigs and fixtures, hand tools, furniture and labour saving devices.
It also facilitates better layout of offices, warehouses, plants and operating areas like the office desk, work bench, aircraft, cockpit and crew compartments of armored fighting vehicles, etc. The application of the principles of Motion Economy eliminates or minimizes the wasteful and fatiguing movements and increases the productivity of workers. It insists on minimizing the movements with respect to:
i. Number of movements
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ii. Length of movements
iii. Classification of movements
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iv. Number of parts of body used
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v. Necessity for control
vi. Muscular force
vii. Complexity movements
viii. Distances between eye fixation
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ix. Time required for eye fixation
Different specialists propounded the following principles, for achieving motion economy:
i. Principle of Minimum Movement
ii. Principle of Natural Movement
iii. Principle of Simultaneous Movement
iv. Principle of Rhythmic Movement
v. Principle of Habitual Movement
vi. Principle of Continuous Movement
Simultaneous movements reduce fatigue and increase the rate of output. Greater fatigue is caused when only one hand works, while the other one is idle. Simultaneous movements include movements of the feet, while both the hands are operating, e.g., driving a car. The application of this principle, enabling both hands work at similar tasks simultaneously, leads to a better design of jigs, fixtures and duplication of tools.
It is advisable that the principle of symmetrical movements be applied in conjunction with simultaneous movements. Proper balance is achieved only when the movement of one hand is the mirror image of the movement of the other. Symmetry in movements eliminates mishandling and promotes ease and speed. When movements of the hands are asymmetrical, operators tend to throw in additional non-productive movements in order to achieve balance.
Rhythm is the regular repetition of a pattern of movement. It often includes the emphasis of a specific part of a cycle. Rhythm plays an important role in increasing the speed, eliminating the tendency of fumbling and reducing fatigue. The examples of rhythmic movements are rowing a boat, hammering done by a blacksmith and drawing water from a well using a seesaw lift.
The pattern of movements should be designed so as to facilitate habit formation. When a cycle of activities becomes a habit, movements are executed almost as a reflex action. Habitual movements eliminate hesitations and increase the speed of performance. Rhythm helps to expedite any habit formation. Tools, materials, displays and controls must always be located in the same position.
The pattern must be standardized for similar types of panels, work places and equipment. Continuous movements that are smooth and curved are superior to jerky straight-line movements, which involve sudden changes of direction and loss of momentum. Materials, tools and jigs must be so positioned to eliminate undue changes of direction and to incorporate smooth, curved and continuous movements.
These principles should not be treated as inflexible rules, but guidelines. For optimization, a proper evaluation of all the principles in their totality is required. This is because frequently, individual principles could be in conflict with one another. Conditions differ from job to job.
At times, it may be necessary to compromise on the principle of minimum movements in order to equitably distribute the physical load over the various muscles. At other times, it may be necessary to give due weight age to the principle of continuous movement. Hence, it is essential that the principles be applied with flexibility.