Motion study helps to reduce time, cost and industrial fatigue by (a) eliminating unnecessary motions, (b) combining related motions, (c) simplifying complex motions, (d) improving the sequence of necessary motions, etc. Motion study is a useful device for improving productivity of labor and equipment.
Gilbreth analyzed the motions of brick layers reducing them from 18 to 5. This led to increase in the productivity of bricklayers from 121 bricks per man per hour to 375 bricks. The technique of motion study can be applied in diverse fields of human effort It seeks to determine the one best way of performing any given job through analysis of work methods and procedures.
Techniques of Motion Study
Following are the important techniques of motion study.
(1) Therblig Analysis.
(2) Micro-motion study.
(3) Work Simplification.
1. Therblig Analysis. First technique is Therbling analysis. Gilbreths pointed out that every manual operation consists of elementary motions or therbligh (Gilbreths spelt backwards with one transposition). Gilbreths developed these through the analysis of a variety of manual motions. Therbligs are smallest elements of work. These therbligs and their symbols are as follows:
1. Search (Sh.) 2. Select (St.) 3. Grasp (G) 4. Transport Empty (TE) 5. Transport Loaded (TL) 6. Hold (H) 7. Release Load (RP 8. Position (P) 9. Preposition (PP) 10. Inspect (I) 11. Assemble (A) 12. Disassemble (DA) 13. Use 14. Unavoidable Delay (UD) 15. Avoidable Delays (AD) 16. Plan (PL) 17. Rest for overcoming fatigue (R)
Analysis of these Therbligs facilitates methods study in the following ways:
(i) These Therbligs are fundamental elements of any type of manual motions. Therefore, improvements gained in one job can be easily applied to another job.
(ii) Therblig analysis is a convenient and effective method of measuring and improving operations.
(iii) Experience in identifying and analyzing therbligs greatly improves the ability to observe and analyze jobs properly.
A therblig chart for an operation may be made from direct observation of a worker performing that job. But the duration of a therblig so small (thousandths part of a minute) that it is extremely difficult to record them in proper sequence from direct observation. This difficulty is overcome by recording the job on a motion picture film and later studying this film, frame by frame, in the laboratory. Such motion picture analysis of job methods is known as micro-motion study.
2. Micro-motion Study. Second technique is Micro-motion study. Where the movements of a worker or machine are very fast, a movie camera attached to a special type of clock (called micronometer) is used to record and time each motion. Such a study is called micro-motion study. Pictures so taken are later operated back at slow motion to identify needless and inefficient motions. The time value fora therblig is shown on the motion cycle chart (called simochart).
Thus, micro-motion study may be defined as a study of the fundamental elements of an operation with the help of a high speed movie camera so as to eliminate the unnecessary motions involved in the operation and creating a proper balance between the necessary motions. Such study provide a correct analysis of fast and very minute motions which cannot be studied through ordinary motion study. It helps to record both the method of performance and the time for each therblig simultaneously.
3. Work Simplification: Work simplification involves subdivision of an operation into constituent elements in order to simplify work operations and to eliminate wasteful motions. It covers all aspects of a work, e.g., equipment, layout, procedures, methods, etc. It helps to improve productivity and to reduce industrial fatigue. It is also known as process analysis because a manufacturing process is analyzed into basic elements so as to simplify and improve the work.