UNIT - III

Principles Of

Motion Economy

Principles Of Motion Economy

• A better method of doing a job is one which consume minimum of time and energy in performing limb ( hand, foot, legs etc) motions in order to complete the job and this is possible due to economizing the use of motion.

• They were first used by Frank Gilbreth, the founder of motion study, and have been amplified by other workers, notably Professor Barnes. They may be grouped under three headings

Use of the human body. Arrangement of the workplace. Design of tools and equipment.

Rules Concerning Human Body• Both hands should be used for productive work.• Both the hands start and finish their motions at same time.• The two hands should not be idle at the same time except during

periods of rest.• Motions of the arms should be symmetrical and in opposite

directions• Motion should be smooth and continuous.• Work should be arranged so that eye movements are confined to a

comfortable area, without the need for frequent changes of focus.• Continuous curved movements are to be preferred to straight-line motions involving sudden and sharp changes in direction.

Rules Concerning Workplace Layout & Material Handling• Definite and fixed stations should be provided for all tools and

materials to permit habit formation.• Tools and materials should be pre-positioned to reduce

searching.• Gravity feed, bins and containers should be used to deliver

the materials as close to the point of use as possible.• Tools, materials and controls should be located within the

maximum working area and as near to the worker as possible.• Materials and tools should be arranged to permit the best

sequence of motions.• The colour of the workplace should contrast with that of the

work and thus reduce eye fatigue.

Rules Concerning Design of Tools and Equipment• The hands should be relieved of all work of "holding" the

workpiece where this can be done by a jig, fixture or foot-operated device.

• Two or more tools should be combined wherever possible.• Where each finger performs some specific movement, as in

typewriting, the load should be distributed in accordance with the inherent capacities of the fingers.

• Handles such as those on cranks and large screwdrivers should be designed so as to permit as much of the surface of the hand as possible.

• Levers, crossbars and hand wheels should be so placed that the operator can use them with the least change in body position.

Work Place Layout

Design of Work place layout (a) Materials and tools should be available at their predetermined places and

close to the worker.

(b) Tools and materials should preferably be located in the order in which they will be used.

(c) The supply of materials or parts, if similar work is to be done by each hand, should be duplicated. That is materials or parts to be assembled by right hand should be kept on right hand side and those to be assembled by the left hand should be kept on left hand side.

(d) Gravity should be employed, wherever possible, to make raw materials reach the operator and to deliver material at its destination (e.g., dropping material through a chute).

(e) Height of the chair and work bench should be arranged in a way that permits comfortable

Design of Work place layout (f) An instrument with a pointer should be employed for check readings

where as for quantitative readings, digital type of instrument should be preferred.

(g) Hand tools should be possible to be picked up with least disturbance or rhythm and symmetry of movements.

(h) Foot pedals should be used, wherever possible, for clamping declamping and for disposal of finished work.

(i) Handles, levers and foot pedals should be possible to be operated without changing body position. (j) Work place must be properly illuminated and should be free from glare to avoid eye strain. (k) Work place should be free from the presence of disagreeable elements like heat, smoke, dust, noise, excess humidity, vibrations etc.

Suggested work place layout • A work place layout with different areas and typical dimensions. It shows

the left hand covering the maximum working area and the right hand covering the normal working area.

1. Normal working area It is within the easy reach of the operator.

Suggested work place layout 2. Maximum Working Area It is accessible with full arm stretch. Figure shows work place layout for

assembling small component parts. A-1 is the actual working area and the place of assembly (POA) where four component parts P-1, P-2, P-3, and P-4 are assembled together. Bins containing P-1, P-2, P-3, and P-4 and commonly employed tools (CET) (like screw driver, plier, etc.) lie in the normal working area A-2. Occasionally required Tools (ORT)

(hammers etc.) lie in the maximum working area A-3. After the assembly has been made at POA, it is dropped into the cut portion in the work table – PDA (Place for dropping assemblies) from where the assembly is delivered at its destination with the help of a conveyer. This work place arrangement satisfies most of the principles of motion economy.

POA

Suggested work place layout 3. Other areas •Other areas include studies related to fatigue, losses

caused due to fatigue, rest pauses, amount of energy consumed, shift work and age considerations.

Work Measurement

Work measurement•Work measurement is a technique to establish the time

required for a qualified worker to carry out a specified job at a defined level of performance.

Objectives of Work Measurement 1. To reduce or eliminate non-productive time. 2. To fix the standard time for doing a job. 3. To develop standard data for future reference. 4. To improve methods.

The Techniques Of Work Measurement•Time study;•Activity sampling, and its extension, rated activity

sampling;•Synthesis from standard data;•Predetermined motion time systems;(PMTS)•Estimating;•Analytical estimating;•Comparative estimating.

Time Study

•Time study is a work measurement technique for recording the times and rates of working for the elements of a specified job carried out under specified conditions, and for analyzing the data so as to obtain the time necessary for carrying out the job at a defined level of performance.

Basic Time Study Equipment

•A stopwatch;•A study board;•Pencils;•Time study forms.•Slide rules;•A reliable clock, with seconds hand;•Measuring instruments such as tape measure, steel rule,

micrometer, spring balance, and tachometer (revolution counter).

Predetermined Motion Time System (PMTS) •PMTS is a work measurement technique where by times,

established for basic human motions (classified according to the nature of the motion and the conditions under which it is made) are used to build up the time for a job at a defined level of performance.

•Few well-known systems using this concept are 1. M.T.M. : Method Time Measurement. 2. W.F.S. : Work Factor System. 3. M.T.A. : Motion Time Analysis. 4. D.M.T. : Dimensional Motion Times. 5. B.M.T. : Basic Motion Times.

Objects and Uses of PMTS

•It is very useful in Method Analysis•Improving the work and method before

starting the work on the job.•It sets time standard for different jobs.•It assist in constructing time formulae.•It provides a basis for wage plans and

labour cost estimation.•It facilitates training of the workers and

supervisors

Advantages of PMTS

•It eliminates inaccuracies associated with watch time study.

•It is superior to stop watch time study•Job can be arrived at without going to the place of

working area.•No rating factors is employed•Job cost in considerably reduced than standard

time study•PMTS helps in tools and product design

Application of PMTS

•Machining work.•Maintenance work.•Assembly Jobs•servicing and•Office work