PSYCH-105 Industrial Psychology
Chapter 3: Time and Motion Study
MOTION STUDY / MOTION ANALYSIS
A scientific way of determining the best method of doing a work with the help of close scrutiny of the motion by a worker or a machine is know as motion study. The purpose is to design an improved method which eliminates unnecessary motions and uses human efforts more productively. By using motion study and the principles of motion economy the task is redesigned to be more effective and less time consuming. Objective of motion study is job simplification so that it is less fatiguing and less time consuming. Through various methods of Motion Study (Micro-Motion Study (movie film) and the Chronocyclegraph) the Gilbreths were able to examine the smallest of motions.
Procedure of Motion Analysis
- Selection of an operation
- Observation and recording of motion performed by operator
- Identification of productive and idle motions
- Non productive motions are eliminative
- Redesign the procedure
- Training of workers
- Standardization of process
Motion study can be divided into three components, namely
i) Analysis of therbligs
ii) Micro motion
iii) Principles of motion economy
Micro Motion Study
Micro motion study may be defines as the study of the fundamental elements of an operation with the help of a high speed movie camera and large clock (known as micro-chronometer) marked off in hundredths of seconds to analyze the motion of works, in order to eliminate the unnecessary motion involved in the operation and balancing the necessary motions.
Traditionally, the data from micro motion studies are recorded on a Simultaneous Motion (simo) Chart while that from macro motion studies are recorded on a Right Hand – Left Hand Process Chart.
The study is known as memo-motion if it is done with the help of a slow speed camera. Memomotion study has been used to study the flow and handling of materials, crew activities, multiperson and machine relationships, stockroom activities, department store clerks, and a variety of other jobs. It is particularly valuable on long-cycle jobs or jobs involving many interrelationships.
Purposes of Micromotion Study
- As an aid in studying the activities of two or more persons on group work,
- As an aid in studying the relationship of the activities of the operator and the machine,
- As a means of timing operations (instead of time study),
- As an aid in obtaining motion-time data for time standards,
- As a permanent record of the method and time of activities of the operator and the machine,
- For research in the field of motion and time study.
However, its two most important uses are:
- To assist in finding the preferred method of doing work,
- To assist in training individuals to understand the meaning of motion study and, when the training is carried out with sufficient thoroughness, to enable them to become proficient in applying motion economy principles.
Principles of Motion Economy
There are a set of principles developed in order to achieve economy in movements and reduction in fatigue on the part of the operator. These are known as the “principles of motion economy”. These principles are particularly applicable and useful for developing improved methods at the workplace. An understanding of these principles helps in the design of equipment, jigs, tools and fixtures, layout of workplaces and development of better methods and forms a basis for improving the utilization and reducing the fatigue. The principles of motion economy may be classified under three headings:
(i) Use of the human body
(ii) Arrangement of the workplace
(iii) Design of tools and equipment
Use of the Human Body
- The two hands should’ begin as well as complete their motion at the same time.
- The two hands should not be idle at the same time except during rest periods.
- Motions of the arms should be made in opposite and symmetrical directions, and should be made simultaneously.
- Hand motions should be confined to the lowest classification with which it is possible to perform the work satisfactorily.
- Momentum should be employed to assist the worker wherever possible, and it should be reduced to a minimum if it must be overcome by muscular effort.
- Smooth continuous motions of the hand are preferable to zig zag motions or straight line motion involving sudden and sharp changes in direction.
- Ballistic movements are faster, easier, and more accurate than restricted (fixation) or ‘controlled’ movements.
- Rhythm is essential to the smooth and automatic performance of an operation and the work should be arranged to permit easy and natural rhythm wherever possible.
- Work should be arranged so that eye movements are confined to a comfortable area, without the need for frequent changes of focus.
Arrangement of the Workplace
- There should be a definite and fixed place for all tools and materials to permit habit formation.
- Tools, materials, and controls should be located close in and directly in front of the operator within the maximum working area.
- Gravity feed bins and containers should be used to deliver material close to the point of use.
- “Drop deliveries” should be used wherever possible.
- Materials and tools should be located to permit the vest sequence of motion.
- Provisions should be made for adequate conditions for seeing. Good illumination is the first requirement for satisfactory visual perception.
- The height of the work place and the chair should preferably be arranged so that alternate sitting and standing at work are easily possible. A chair of the type and height to permit good posture should be provided for every worker.
- The colour of the workplace should contrast with that of the work and thus reduce eye fatigue.
Design of Tools and Equipment
- The hands should be relieved of all work that can be done more advantageously by a jig, fixture, or a foot-operated device.
- Two or more tools should be combined wherever possible.
- Tools and material should be pre-positioned wherever possible.
- Where each finger performs some specific movement, such as an in typewriting, the load should be distributed in accordance with the inherent capacities of the fingers.
- Handles such as those used on cranks and large screw drivers should be designed to permit as much of the surface of the hand to come in contact with the handle as possible. This is particularly true when considerable force is exerted in using the handle. For light assembly work the screw driver handle should be so shaped that it is smaller at the bottom than at the top.
- Levers, cross-bars, and hand wheels should be located in such positions that the operator can manipulate them with the least change in body position and with the greatest mechanical advantage.