Work Study
What is Work Study? What is work?: Work is an activity in which one exerts physical and mental effort to accomplish a given task or perform a duty. Task: An amount of work that is assigned to a worker or for which a worker is responsible. Work Element: A series of work activities that are logically grouped together because they have a unified function in the task
Task
Work Elements
Basic Motion Elements The Pyramidal Structure of Work
A work element consists of multiple basic motion elements Examples: Reaching for an object, Grasping the object, Moving the object, Walking, Eye movement
Work Study
• •
Work Study is the systematic examination of the methods of carrying out activities such as to improve the effective use of resources and to set up standards of performance for the activities carried out. A generic term for those techniques, particularly method study and work measurement, which are used in the examination of human work in all its contexts, and which lead systematically to the investigation of all the factors which affect the efficiency and economy of the situation being reviewed, in order to effect improvement.
Work study
Method study
Work measurement
Method Study
Method-study concerned with “the way in which work is done (i.e., method)”. It is used to simplify the way to accomplish a work and to improve the method of production. Method-study results in a more effective use of material, plant, equipment and manpower. Method study is essentially concerned with finding better ways of doing things. It adds value and increase the efficiency by eliminating unnecessary operations, avoidable delays and other forms of waste. The improvement of efficiency is achieved through: 1.Present and analysis true facts concerning the situation. 2.To examination those facts critically 3.To develop the best answer possible under given circumstances based on critical examination of facts.
Steps or procedure involved in methods study
1. Select : select the work to be studied. • The job should be selected for the method study based upon the following considerations:
a) Economical aspect b) Technical aspect c) Human aspect 2. Record: record the relevant facts about the job by direct observation • Recording techniques used for method study are charts and diagrams.
Steps or procedure involved in methods study
Recording techniques for method study
Macro motion charts 1. Operations process chart 2. Flow process chart 3. Two Handed process chart 4. Multiple activity chart
Recording techniques for method study
Recording techniques for method study
Operation process chart: An operation process chart provides the chronological sequence of all operations and inspections that occur in a manufacturing or business process. Operation process chart used only two symbols, i.e., operation and inspection.
Operation
Move
Delay
Store
Inspection
Combined Activity
Recording techniques for method study
Operation process chart:
Recording techniques for method study
Flow process chart: A flow process chart is used for recording greater detail than is possible in an operation process chart. It is made for each component of an assembly rather than for the whole assembly.
Recording techniques for method study
Flow process chart:
Recording techniques for method study
String Diagram: String Diagram is a scale layout drawing on which, length of a string is used to record the extent as well as the pattern of movement of a worker working within a limited area during a certain period of time. It is a scale diagram on which color threads are wrapped around pins or pegs, which are used to indicate the paths taken by either worker or material or equipment when processing is done on material from start to finish.
Recording techniques for method study
String Diagram:
Steps or procedure involved in methods study
3. Examine: examine the way the job is being performed and test its purpose, place, sequence and method of performance. • In this step, the information provided by charts and diagrams is critically examined and screened by asking some searching questions. Like, what is done?, why it is done?, what else might be done? Etc. • This examination is carried out with a view to eliminate, combine, rearrange and/or simplify the activities. 4. Develop: develop the most practical, economical, and effective method. After critical examination of records is complete, it is necessary to transform the learning’s into the development of new methods. Some approaches are: a) Eliminate unnecessary activities. b) Combine two or more activities. For example, if one uses a combination tool for two operations, say, facing and drilling, the total set-up time will reduce. c) Re-sequence activities so as to reduce time and effort. d) Simplify process to reduce number of operations or reduce effort or reduce throughput, etc. e) Attack on constraints, which are preventing the method to perform better.
Steps or procedure involved in methods study
5. Evaluate: evaluate different alternatives to develop a new improved method comparing the cost-effectiveness of the selected new method with the current method of performance. 6. Define: define the new method in a clear manner and present it to those concerned, i.e., management, supervisors and worker. A report on new improved method should be prepared. It should include: • Description of the method. • Cost of installing the new method, including cost of new equipment and of relaying out shops or working areas. • Diagram of the work place layout. • Tools and equipment to be used and diagrams of jigs/fixtures etc. • Executive actions required to implement the new method. 7. Install: install the new method as a standard practice and train the persons involved in applying it. 8. Maintain: Maintain the new method and introduce control procedures to prevent a drifting back to the previous method of work.
Work measurement
Work measurement is the application of techniques designed to establish the time for a qualified worker to carry out specified jobs at a defined level of performance or at a defined rate of working. A qualified worker is one who has acquired the skill, knowledge and other attributes to carry out the work in hand to satisfactory standards of quantity, quality and safety. Defined rate of working is the amount of work that can be produced by a qualified worker/employee when working at normal space and effectively utilizing his time and where work is not restricted by process limitation. Uses of work measurement: To compare the efficiency of alternative methods. Cost estimation Pricing of products and services Incentive pay systems Capacity planning Production scheduling To provide information on which estimates for tenders, selling prices and delivery promises can be based.
Work measurement
Technique of work measurement: a) Time study: short cycle repetitive jobs b) Work sampling: Long cycle jobs c) Predetermined motion time standards: manual operations confined to one work centre.
Time Study
Steps in making a time study 1) Select the work to be study • The job is a new one not previously carried out. • A change in material or method of working has been made and a new time standard is required. • A complaint has been received about the time standard for an operation. • A particular operation appears to be “bottleneck” holding up the subsequent operations and possibly previous operations. • Standard times are required prior to the introduction of an incentive scheme. 2) Obtaining and recording all the information about the job, the operator and the surrounding conditions, which is likely to affect the carrying out of the work.
Steps in making a time study
3) Breakdown the operation into “elements.” 4) Measure the time by means of a stop watch taken by the operator to perform each element of operation. Either continuous method or snap back method of timing could be used. 5) At the same time assess the operator’s effective speed of work relative to the observer’s concept of normal speed. This is called performance rating. 6) Adjust the observed time by rating factor to obtain normal time (basic times) for each element. 7) Sum the normal times for each element to develop a total normal time for the task 7) Determining the allowances to be made over and above the normal time for operation. 8) Determining the “standard time” for the operation. 9) Test and review standards wherever necessary.
Time study
• Personal time allowance : 4% - 7% of total time - use of restroom, drinking water, etc. • Fatigue allowance - to compensate for physical or mental strain, noise level, tediousness, heat and humidity, assumption of an abnormal position, etc. • Delay allowance - based upon actual delays that occur.
Performance Rating
Allowance Fraction
Observed Time
Normal Time
Standard Time
Standard time = observed time + rating factor + Personal allowance + Fatigue allowance + delay allowance + work related contingency allowance.
Time study
• Observed time • Performance rating • Allowance fraction Find the standard time Normal time = Observed time x Performance rating = 8.6 x 0.95 = 8.17 minutes Standard Time = Normal time / (1 – Allowance fraction) = 8.17 / (1 - .125) = 8.17 / (0.875) = 9.337 minutes = 8.6 minutes = 0.95 = 0.125
Motion study
• Motion study is a technique of analyzing the body motions employed in doing a task in order to eliminate or reduce ineffective movements and facilitates effective movements. • 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. • Lillian Gilbreth used motion picture to study worker motions – developed 17 motions called “therbligs” that describe all possible work. • 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.
Motion study
1. Transport empty (TE) – reach for an object 2. Grasp (G) – grasp an object 3. Transport loaded (TL) – move an object with hand and arm 4. Release load (RL) – release control of an object 5. Use (U) – manipulate a tool 6. Hold (H) – hold an object 7. Pre-position (PP) – position object for next operation 8. Position (P) – position object in defined location 9. Assemble (A) – join two parts 10. Disassemble (DA) – separate multiple parts that were previously joined 11. Search (Sh) – attempt to find an object using eyes or hand 12. Select (St) – choose among several objects in a group 13. Plan (Pn) – decide on an action 14. Inspect (I) – determine quality of object 15. Unavoidable delay (UD) – waiting due to factors beyond worker control 16. Avoidable delay (AD) – worker waiting 17. Rest (R) – resting to overcome fatigue
