Method study enables the industrial engineer to subject each operation to systematic analysis. The main purpose of method study is to eliminate the unnecessary operations and to achieve the best method of performing the operation.
Method study is also called methods engineering or work design. Method engineering is used to describe collection of analysis techniques which focus on improving the effectiveness of men and machines.
According to British Standards Institution (BS 3138): “Method study is the systematic recording and critical examination or existing and proposed ways or doing work as a means or developing and applying easier and more effective methods and reducing cost. ”
Fundamentally method study involves the breakdown of an operation or procedure into its component elements and their systematic analysis. In carrying out the method study, the right attitude of mind is important. The method study man should have:
- The desire and determination to produce results.
- Ability to achieve results.
- An understanding of the human factors involved.
Method study scope lies in improving work methods through process and operation analysis, such as:
- Manufacturing operations and their sequence.
- Materials, tools and gauges.
- Layout of physical facilities and work station design.
- Movement of men and material handling.
- Work environment.
1. Objectives of Method Study
Method study is essentially concerned with finding better ways of doing things. It adds value and increases the efficiency by eliminating unnecessary operations, avoidable delays and other forms of waste.
The improvement in efficiency is achieved through:
- Improved layout and design of workplace.
- Improved and efficient work procedures.
- Effective utilisation of men, machines and materials.
- Improved design or specification of the final product.
The objectives of method study techniques are:
- Present and analyse true facts concerning the situation.
- To examine those facts critically.
- To develop the best answer possible under given circumstances based on critical examination of facts.
2. Scope of Method Study
The scope of method study is not restricted to only manufacturing industries. Method study techniques can be applied effectively in service sector as well. It can be applied in offices, hospitals, banks and other service organizations.
The areas to which method study can be applied successfully in manufacturing are:
- To improve work methods and procedures.
- To determine the best sequence of doing work.
- To smoothen material flow with minimum of back tracking and to improve layout.
- To improve the working conditions and hence to improve labour efficiency.
- To reduce monotony in the work.
- To improve plant utilisation and material utilisation.
- Elimination of waste and unproductive operations.
- To reduce the manufacturing costs through reducing cycle time of operations.
3. Steps or Procedure Involved in Methods Study
The basic approach to method study consists of the following eight steps. The detailed procedure for conducting the method study is shown in Fig. 7.3.
- SELECT the work to be studied and define its boundaries.
- RECORD the relevant facts about the job by direct observation and collect such additional data as may be needed from appropriate sources.
- EXAMINE the way the job is being performed and challenge its purpose, place sequence and method of performance.
- DEVELOP the most practical, economic and effective method, drawing on the contributions of those concerned.
- EVALUATE different alternatives to developing a new improved method comparing the cost-effectiveness of the selected new method with the current method with the current method of performance.
- DEFINE the new method, as a result, in a clear manner and present it to those concerned,i.e, management, supervisors and workers.
- INSTALL the new method as a standard practice and train the persons involved in applying it.
- MAINTAIN the new method and introduce control procedures to prevent a drifting back to the previous method of work.
Note: Only the first two steps have been dealt in detail.
4. Selection of the Job for Method Study
Cost is the main criteria for selection of a job, process and department for methods analysis. To carry out the method study, a job is selected such that the proposed method achieves one or more of the following results:
- Improvement in quality with lesser scrap.
- Increased production through better utilisation of resources.
- Elimination of unnecessary operations and movements.
- Improved layout leading to smooth flow of material and a balanced production line.
- Improved working conditions.
Considerations for Selection of Method Study
The job should be selected for the method study based upon the following considerations:
- Economic aspect
- Technical aspect, and
- Human aspect.
A. Economic Aspects
The method study involves cost and time. If sufficient returns are not attained, the whole exercise will go waste. Thus, the money spent should be justified by the savings from it. The following guidelines can be used for selecting a job:
- Bottleneck operations which are holding up other production operations.
- Operations involving excessive labour.
- Operations producing lot of scrap or defectives.
- Operations having poor utilisation of resources.
- Backtracking of materials and excessive movement of materials.
B. Technical Aspects
The method study man should be careful enough to select a job in which he has the technical knowledge and expertise. A person selecting a job in his area of expertise is going to do full justice.
Other factors which favour selection in technical aspect are:
- Job having in consistent quality.
- Operations generating lot of scraps.
- Frequent complaints from workers regarding the job.
C. Human Considerations
Method study means a change as it is going to affect the way in which the job is done presently and is not fully accepted by workman and the union. Human considerations play a vital role in method study. These are some of the situations where human aspect should be given due importance:
- Workers complaining about unnecessary and tiring work.
- More frequency of accidents.
- Inconsistent earning.
5. Recording Techniques for Method Study
The next step in basic procedure, after selecting the work to be studied is to record all facts relating to the existing method. In order that the activities selected for investigation may be visualised in their entirety and in order to improve them through subsequent critical examination, it is essential to have some means of placing on record all the necessary facts about the existing method. Records are very much useful to make before and after comparison to assess the effectiveness of the proposed improved method.
The recording techniques are designed to simplify and standardise the recording work. For this purpose charts and diagrams are used.
CHARTS USED IN METHODS STUDY
This is the most popular method of recording the facts. The activities comprising the jobs are recorded using method study symbols. A great care is to be taken in preparing the charts so that the information it shows is easily understood and recognized. The following information should be given in the chart. These charts are used to measure the movement of operator or work (i.e, in motion study).
- Adequate description of the activities.
- Whether the charting is for present or proposed method.
- Specific reference to when the activities will begin and end.
- Time and distance scales used wherever necessary.
- The date of charting and the name of the person who does charting.
Types of Charts
It can be broadly divided into (A) Macro motion charts and (B) Micro motion charts.
Macro motion charts are used for macro motion study and micro motion charts are used for micro motion study.
Macro motion study is one which can be measured through ‘stop watch’ and micro motion study is one which cannot be measured through stop watch.
MACRO MOTION CHARTS
Following four charts are used under this type:
- Operation Process Chart
It is also called outline process chart. An operation process chart gives the bird’ s eye view of the whole process by recording only the major activities and inspections involved in the process. Operation process chart uses only two symbols, i.e, operation and inspection. Operation, process chart is helpful to:
- Visualise the complete sequence of the operations and inspections in the process.
- Know where the operation selected for detailed study fits into the entire process.
- In operation process chart, the graphic representation of the points at which materials are introduced into the process and what operations and inspections are carried on them are shown.
- Flow Process Chart
Flow process chart gives the sequence of flow of work of a product or any part of it through the work centre or the department recording the events using appropriate symbols. It is the amplification of the operation process chart in which operations; inspection, storage, delay and transportation are represented. However, process charts are of three types:
- Material type—Which shows the events that occur to the materials.
- Man type—Activities performed by the man.
- Equipment type—How equipment is used.
The flow process chart is useful:
- to reduce the distance travelled by men (or materials).
- to avoid waiting time and unnecessary delays.
- to reduce the cycle time by combining or eliminating operations.
- to fix up the sequence of operations.
- to relocate the inspection stages.
Like operation process chart, flow process chart is constructed by placing symbols one below another as per the occurrence of the activities and are joined by a vertical line. A brief description of the activity is written on the right hand side of the activity symbol and time or distance is given on the left hand side.
- Two Handed Process Chart
A two handed (operator process chart) is the most detailed type of flow chart in which the activities of the workers hands are recorded in relation to one another. The two handed process chart is normally confined to work carried out at a single workplace. This also gives synchronised and graphical representation of the sequence of manual activities of the worker. The application of this charts are:
- To visualise the complete sequence of activities in a repetitive task.
- To study the work station layout.
- Multiple Activity Chart
It is a chart where activities of more than subject (worker or equipment) are each recorded on a common time scale to show their inter-relationship. Multiple activity chart is made:
- to study idle time of the man and machines,
- to determine number of machines handled by one operator, and
- to determine number of operators required in teamwork to perform the given job.
Diagrams Used in Method Study
The flow process chart shows the sequence and nature of movement but it does not clearly show the path of movements. In the paths of movements, there are often undesirable features such as congestion, back tracking and unnecessary long movements. To record these unnecessary features, representation of the working area in the form of flow diagrams, string diagrams can be made:
- To study the different layout plans and thereby; select the most optimal layout.
- To study traffic and frequency over different routes of the plant.
- Identification of back tracking and obstacles during movements. Diagrams are of two types: 1. Flow diagram and 2. String diagram.
(1) Flow Diagram
Flow diagram is a drawing, of the working area, showing the location of the various activities identified by their numbered symbols and are associated with particular flow process chart either man type or machine type.
The routes followed in transport are shown by joining the symbols in sequence by a line which represents as nearly as possible the path or movement of the subject concerned. Following are the procedures to make the flow diagram:
- The layout of the workplace is drawn to scale.
- Relative positions of the machine tools, work benches, storage, and inspection benches are marked on the scale.
- Path followed by the subject under study is tracked by drawing lines.
- Each movement is serially numbered and indicated by arrow for direction.
- Different colours are used to denote different types of movements.
(2) String Diagram
The 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. The primary function of a string diagram is to produce a record of a existing set of conditions so that the job of seeing what is actually taking place is made as simple as possible.
One of the most valuable features of the string diagram is the actual distance travelled during the period of study to be calculated by relating the length of the thread used to the scale of drawing. Thus, it helps to make a very effective comparison between different layouts or methods of doing job in terms of the travelling involved.
The main advantages of string diagram compared to flow diagram is that respective movements between work stations which are difficult to be traced on the flow diagram can be conveniently shown on string diagram.
Folloging are the procedures to draw string diagram:
- A layout of the work place of factory is drawn to scale on the soft board.
- Pins are fixed into boards to mark the locations of work stations, pins are also driven at the turning points of the routes.
- A measured length of the thread is taken to trace the movements (path).
- The distance covered by the object is obtained by measuring the remaining part of the thread and subtracting it from original length.
Symbols Used in Method Study
Graphical method of recording was originated by Gilberth, in order to make the presentation of the facts clearly without any ambiguity and to enable to grasp them quickly and clearly. It is useful to use symbols instead of written description.
(A) METHOD STUDY SYMBOLS
An operation occurs when an object is intentionally changed in one or more of its characteristics (physical or chemical). This indicates the main steps in a process, method or procedure.
An operation always takes the object one stage ahead towards completion.
Examples of operation are:
- Turning, drilling, milling, etc.
- A chemical reaction.
- Welding, brazing and riveting.
- Lifting, loading, unloading.
- Getting instructions from supervisor.
- Taking dictation.
An inspection occurs when an object is examined and compared with standard for quality and quantity. The inspection examples are:
- Visual observations for finish.
- Count of quantity of incoming material.
- Checking the dimensions.
A transport indicates the movement of workers, materials or equipment from one place to another.
Movement of materials from one work station to another.
Workers travelling to bring tools.
Delay D: Delay (Temporary Storage)
A delay occurs when the immediate performance of the next planned thing does not take place.
Work waiting between consecutive operations.
Workers waiting at tool cribs.
Operators waiting for instructions from supervisor.
Storage occurs when the object is kept in an authorised custody and is protected against unauthorised removal. For example, materials kept in stores to be distributed to various work.
ILLUSTRATION 1. Develop a Process Chart for making a cheese sandwich. SOLUTION. The following chart is one possible solution. The level of detail in process charts depends upon the requirements of the job. Time is often included to aid analysis of value added.
ILLUSTRATION 2. Develop a Multiple Activity Chart for doing three loads of laundry, assume you will have access to one washing machine and one dryer.
SOLUTION: The followingchart is one possible solution. The level of detail in process charts depends upon the requirements of the job. Time is often included to aid analysis of value added.
Multiple Activity Chart
(B) MICRO-MOTION STUDY CHART
Micro-motion study provides a technique for recording and timing an activity. It is a set of techniques intended to divide the human activities in a groups of movements or micro-motions (called Therbligs) and the study of such movements helps to find for an operator one best pattern of movements that consumes less time and requires less effort to accomplish the task. Therbligs were suggested by Frank O. Gilbreth, the founder of motion study. Micro-motion study was mainly employed for the job analysis. Its other applications includes:
- As an aid in studying the activities of two or more persons on a group work?
- As an aid in studying the relationship of the activities of the operator and the machine as a means of timing operations.
- As an aid in obtaining motion time data for time standards.
- Acts as permanent record of the method and time of activities of the operator and the machine.
The micro-motion group of techniques is based on the idea of dividing human activities into division of movements or groups of movements (Therbligs) according to purpose for which they are made. Gilbreth differentiated 17 fundamental hand or hand and eye motions. Each Therbligs
has a specific colour, symbol and letter for recording purposes. The Therbligs are micro-motion study involves the following steps:
- Filming the operation to be studied.
- Analysis of the data from the film.
The recording of the data through SIMO chart is done as micro motion chart.
Simultaneous motion cycle chart (SIMO chart) is a recording technique for micro-motion study. A SIMO chart is a chart based on the film analysis, used to record simultaneously on a common time scale the Therbligs or a group of Therbligs performed by different parts of the body of one or more operators.
It is the micro-motion form of the man type flow process chart. To prepare SIMO chart, an elaborate procedure and use of expensive equipment are required and this study is justified when the saving resulting from study will be very high.
Source: KumarAnil, Suresh N. (2009), Production and operations management, New Age International Pvt Ltd; 2nd Ed. edition.