Manufacturing & Operations Management

Topic 7Productivity

Work Study To Increase productivity, two important

functions of production management are : Installation of the most effective method of

performing the operation The control of resources like plant, equipment &

labour used in carrying out operations.

To fulfill these two requirement work study is used which comprise of Method Study & Work Measurement

Method Study defined

According to British Standards Institution ….

Method study is a systematic recording and critical examination of existing and proposed ways of doing work, as a means of developing and applying easier and more effective methods and reducing costs.

Work Study Method study along with Work Measurement is

termed as Work Study Method Study aims to determine

the most effective method of performing a job the most logical layout of manufacturing facilities the smooth flow of men and material throughout the

organisation and the right placement of inspection stages

to enable processing of a job through the smallest possible time and at least possible cost

Work Measurement on the other hand helps to determine the time required by the operator to complete a specified task for the defined method at the defined pace of performance.

Method Study and Work Measurement as two separate techniques, yet they are closely related and complement each other.

Method Study should precede work measurement as the time for a job can be assessed accurately only after standardizing the method

Scope of Method Study

Production method is a complicated combination of men, machines and materials, thus scope of method study is more broad based.

Scope of Method Study Method study analyse

Manufacturing operations and their sequence machines workmen materials Tools Gauges and measuring instruments Work bench layout Layout of physical facilities Movement of men and materials Materials handling Working conditions

Use of Method Study To evolve creatively and innovatively improve the

process and procedures to determine the correct sequence of operations and

avoid duplication to improve layout, smoothen materials flow, reduce

backtracking and avoid obstacles, to reduce the unoccupied time of an operator and

thereby obtain effective use of human effort to improve utilization of the equipment and thereby

reduce the manufacturing cycle time per piece to select material of right specifications, cut down

process waste, reduce defectives

Use of Method Study To select right cutting tool, improve tool life and reduce

tool cost per ton. To fix inspection stages to reduce defectives and

optimize quality assurance costs to achieve economy in human effort and reduction of

unnecessary fatigue to develop a better physical environment

Objectives of method study

Better design of plant, equipment and buildings

Improved layout of factory and offices better working condition and

environment higher standards of safety and health Improved flow of work Better Quality

Objectives of method study

Greater job satisfaction Higher earnings improved utilizations of resources effective material handling efficient process and procedures Optimum inventory improved administration Waste reduction Standardisation and rationalisation

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, person and method of performance.

DEVELOP the most practical, economic and effective method. EVALUATE different alternatives to developing a new improved

method, and compare the cost-effectiveness of the selected new method with the current method of performance.

DEFINE the new method in a clear manner and present it to those concerned, management, supervisors and workers.

INSTALL the new method as standard practice and train the persons involved in applying it.

MAINTAIN the new method & introduce control procedures to prevent a drawback to the previous method of work.

Basic procedure for Method Study

Selecting the work to be studiedThere are three factors that should be

kept in mind when selecting a job. Economic or cost-effective considerations. Technical considerations. Human considerations.

Step 1 for Method Study

1. Economic considerations: It is obviously a waste of time to start or

continue a long investigation if the economic importance of a job is small.

Questions that should always be asked Will it pay to begin a method study of this

job? Or Will it pay to continue this study?

Obvious choices for study are: A. Key profit-generating or costly operations or ones

with the largest Scrap/waste rates. E.g. excessive overtime.

B. Bottlenecks which are holding up other production operations, or lengthy operations that consume a great deal of time.

C. Operations involving repetitive work using a great deal of labor and ones that are likely to run for a long time.

D. Movements of material over long distances between workstations, those involving the use of a relatively large proportion of labor or which require repeated handling of material.

2. Technical or technological considerations:

Operations producing excessive defects Frequent complaints from workers regarding jobs whose

performance standards can not be achieved Operations involving very close or frequent supervision Jobs having inconsistant quality Jobs involved where too much of checking and rechecking is

involved

Human considerations:

Certain operations are often a cause of dissatisfaction by workers.

Repeated cases of accidents and health hazards They may bring on fatigue or monotony or may be unsafe to

operate. The level of satisfaction should point to a need for method

study. In a similar fashion, a choice of a particular job for study may lead to anxiety or ill feeling. The suggestion given here is to leave it alone.

Not to start a method study program in disturbed times (labour unrest, strikes etc) other wise the ideas even though good may be misinterpreted.

Also to keep in mind to go at a pace that the organisation can absorb. Surpise and hurried steps can be taken otherway by the workers

Record the factsThe next step in the basic procedure, after selecting the work

to be studied, is to record all the facts relating to the existing method.

The success of the whole procedure depends on the accuracy with which the facts are recorded, because they will provide the basis of both the critical examination and the development of the improved method.

Recording serves essentially as a basis for following analysis and examination.

Recording may be carried out in two phases: First, a rough sketch or charting of the job being

studied to establish whether the recorded information is of use;

Second, a more formal and accurate chart or diagram to include in a report or presentation.

Step 2 for method study

For recording , Graphical method is prefered over descriptive method Complicated process is difficult to

narrate in descriptive form and is labour and time consuming

Symbols & charting not only reduce the efforts but also segregate the effective part from the ineffective parts

Critical examination is easier and effective with symbols

Graphical method of recording the methods was originated by Gilbreth who used 40 symbols.

Then ASME and BSI have recommended use of only 5 symbols

Method Study Symbols 1. Operation

An Operation occurs when there is a distinct change in physical or

chemical characteristics of an object when there is an addition or subtraction when there is a consumption of physical effort When information is given or received

Operation takes the object a stage further towards completion

E.g. Turning, drilling, riveting, removal of worn out part , giving directions, loading, unloading

Method Study Symbols 2. Inspection

Inspection occurs when an object is verified against pre-determined standards of quality, or quantity or both.

Unlike operations , inspection does not carry the object a step forward towards completion

E.g. checking physical dimensions, physical count of items in warehouse.

3. Transport

A Transport occurs when an object or a person is moved from one place to another

E.g. Movement of materials in a trolley, Movement of secretary to MD’s cabin to take dictation

4. Delay D A delay occurs when the object is held

up resulting in delay in the start of next event i.e. next operation or inspection or transport

E.g. Worker waiting for tool to be issued , jobs waiting for inspection

Storage

A storage occurs when an object is kept in an authorised custody and is protected against unauthorised removal

E.g. Tools kept in a rck in tool room Copy of a document in a file

Charting Conventions Composition of the chart

Introduction Body Summary

Rejection Repetition Reprocessing Introduction of new materials Combined activities Numbering of activities

Charting Conventions A) Composition of Chart

Introduction : Name of the chart Present & proposed method Task under study Chart begins, chart ends, charted by, date of charting

Body : Shows activities by revelant symbols written one below

another according to the sequence Summary :

Gives frequency of each symbol, total time for each symbol and total distance travelled

B) Rejection : Rejected materials are shown in chart as :

Turning operation

To inspection table

Check for dimensions

2 % rejection to scrap bin

0.5

15 m

0.1

C) Repetition : If an activity or series of activities are to be repeated it is shown as :

Repeat2 times

0.5

0.25

0.5

0.3

Load component into drill jig

Swing arm into position

Drill 10 mm through hole

Clear drill, move drill head to next hole

D) Reprocessing : when a component is not completely rejected but is to be reworked.

0.5

0.25

0.5

0.1

Load job on milling machine

Carry out milling operation

Remove job from milling machine

To inspection bay

Inspect parts

E) Introduction of new materials

0.5

1.0

0.2

0.1

Bottles washed

Bottle Filling

Bottles capped

Bottles labled

Bottles 120 nos.

To washer

To filling area

20 m

15mCough syrup24 kg

Caps 120 Nos.

Lables 120 Nos.

F) Combined activity : Sometimes more than one activity are performed simultaneously

2.0

1.5

Mixing of batch

Batch unloaded and miosture Checked while unloading

G) Numbering of activities : symbols in process

charts are numbered for easy reference. Like symbols are numbered serially from beginning to end

1

1

2

2

1

1

3

Types of charts used for recording

Operation Process Cahrt Flow process Chart

Man Type Material Type Equipment Type

Multiple activity chart Two handed process chart Travel chart

Operation Process Chart A chart in which the major activities and

entry points of materials are recorded to have a graphic view of operations and inspections involved in the process

Only operations & inspections are depicted and activities like transport, delays and storage are not shown

It is a bird eye’s view of the entire process

Flow Process Chart It is a chart which sets out the sequence of flow of

work of a product, or any part of it through the section or the department or the factory by recording the events under review using appropriate symbols

In addition to operations & inspection, storage, delays and transport is also shown

Separate flow process chart is prepared for all major components

Flow process charts are of three types Man type : to denote activities performed by a man Equipment type : which exhibits activities performed by

an equipment Material Type : which shows the events that occur to

the materials

Need for a flow process chart

To explore the possibility of Reduce distance traveled by workmen or

material Avoiding waiting time or delays &

therefore reducing production loss Combining or eliminating operations Evolving better sequence Relocation of inspection stages to reduce

the frequency of inspection

Diagrams

Flow process charts records movements but they fail to provide a visual picture.

Problems concerning movements can be visualised by drawing a diagram

Diagrams are useful to : Study the different plant layout and

thereby select the best Study the extent of traffic over the

different routes of the plant Identify the extent of back-tracking,

cross traffic and obstacles Study the activity relationship between

departments / work centres

Types of Diagrams

Flow Diagrams String Diagrams

Flow Diagrams

Flow diagrams are scale plans on which the movements of an object are traced by lines

Flow diagram shows the relative position of all the machine tools, work benches, storage, racks, incpection bays

Steps to prepare flow diagram Layout of the workshop or factory is drawn

to scale on a paper Relative position of all the machine tools,

work benches, storage areas, inspection benches are marked on the layout

The paths followed by the subject under study are traced by drawing lines

Each movement is serially numbered and indicated by arrow for its direction

To avoid confusion, use different colour are used to denote different type of movements

Step 3 for Method Study

Examine critically: by using the questioning technique.

The questioning technique is the means by which the critical examination is conducted, each activity being subjected in turn to a systematic and progressive series of questions.

The questioning sequence used follows a well-established pattern which examines:

In the first stage of the questioning technique, the purpose, place, sequence, person and means of every activity recorded are systematically questioned, and a reason for each reply is required.

Step 4 & 5

Development & Evaluation & Selection

Step 6

Installation of proposed method Make proposal for approval by

management Secure formal approval Implement the proposal in the most

speedy and efficient way

Step 7

Maintain Monitoring and control Audit of the savings Review of the approach Performance appraisal

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.

We have seen how total time to manufacture a product is increased by:

adding undesirable features to product, bad operation of the processes, and ineffective time added because of worker and management.

All this leads to decreased productivity.

Work Measurement

Work measurement (WM) is concerned with investigating, reducing and eliminating ineffective time, whatever may be the cause.

WM is the means of measuring the time taken in the performance of an operation or series of operations in such a way that the ineffective time is shown up and can be separated out.

In practice, proving existence of the ineffective time is the most difficult task.

After existence is proved, nature and extent is easy to see!

Work Measurement

WM is also used to set standard times to carry out the work, so that any ineffective time is not included later.

Any addition the standard time would show up as excess time and thus can be brought to attention.

Since, standard times are set for all the activities through WM, it has earned bad reputation amongst workers.

Major reason for that has been the initial focus of the WM methods, which essentially targeted only the worker controllable ineffective times.

Management controllable ineffective times were ignored traditionally.

Purpose of WM

To reveal the nature and extent of ineffective time, from whatever cause,

So that action can be taken to eliminate it; and then, To set standards of performance that are attainable only if all

avoidable ineffective time is eliminated and work is performed by the best method available.

Uses of WM

To compare the efficiency of alternative methods. Other conditions being equal, the method which takes the least time will be the best method.

To balance the work of members of teams, in association with the multiple activity charts, so that, as far as possible, each member has tasks taking an equal time.

To determine, in association with man and machine multiple activity charts, the number of machines an worker can run.

Uses of time standards

To provide information on which the planning and scheduling of production can be based, including the plant and labor requirements for carrying out the program of work and utilization of resources.

To provide information on which estimates for tenders, selling prices and delivery promises can be based.

To set standards of machine utilization and labor performance which can be used for incentive scheme.

To provide information for labor-cost control and to enable standard costs to be fixed and maintained.

Techniques for WM

Time study Activity sampling; and rated activity sampling Synthesis from standard data Pre-determined motion time system Estimating Analytical estimating Comparative estimating.

Time study

A WM technique for Recording the times and rates of working for the elements of a

specified job carried out under specified conditions, Analyzing the data so as to obtain the time necessary for carrying out

the job at a defined level of performance.

Selecting a job for time study

The job in question 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.

Selecting a job for time study

To investigate the utilization of a piece of plant, the output of which is low, or which appears to be idle for an excessive time.

As a preliminary to making a method study, or to compare the efficiency of two proposed methods.

When the costs of a particular job appears to be excessive.

Qualified worker

One who is accepted as having the necessary physical attributes, who possesses the required intelligence, education, and has acquired the necessary skill and knowledge to carry out the work in hand to satisfactory standard of safety, quantity and quality.

In setting the time standards, specially when they are to be used for incentives, the standard to aimed at is one which can be attained by the qualified worker.

A representative worker is one whose skill and performance is the average of the group under consideration. (S/)He may not necessarily be a qualified worker.

Steps in making a time study

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.

Recording a complete description of the method, breaking down the operation into “elements.”

Examining the detailed breakdown to ensure that the most effective method and motions are being used.

Measuring and recording the time taken by the operator to perform each “element” of the operation.

Steps in making a time study

At the same time assessing the effective speed of the working of the operative in relation to the observer’s concept of the rate corresponding to standard rating.

Extending the observed times to “basic times.” Determining the allowances to be made over and above the basic time

for operation. Determining the “standard time” for the operation.

Breaking the job into elements

An element is an distinct part of a specified job selected for convenience of observation, measurement and analysis.

A work cycle is the sequence of elements which are required to perform a job or yield a unit of production. The sequence may sometimes include occasional elements.

For each job, a detailed breakdown of the complete job into elements is necessary. Because….

Reasons for breakdown of job

To ensure that productive work (or effective time) is separated from unproductive activity (or ineffective time).

To permit the rate of working to be assessed more accurately than would be possible if the assessment were made over a complete cycle.

To enable different types of elements to be identified and distinguished, so that each may be accorded the treatment appropriate.

To enable elements involving high fatigue to be isolated and to make the allocation of fatigue allowances more accurate.

Reasons for breakdown of job

To facilitate checking the method and so that subsequent omission or insertion of elements may be detected quickly.

To enable a detailed work specification to be prepared. The enable time values for frequently recurring elements, such as the

operation of machine control or loading and unloading work-pieces from fixtures, to be extracted and used in compilation of the synthetic data.

Time study: Rating

Rating is the assessment of the worker’s rate of working relative to the observer’s concept of the rate corresponding to the standard pace.

It is a comparison of rate of working observed by the work-study person with a picture of some standard level.

The standard level is the average rate at which qualified workers will naturally work at a job, when using the correct method and when motivated to apply themselves to their work.

This rate of working is called standard rating.

Time study: Rating

If the standard pace is maintained and the appropriate relaxation is taken, a worker will achieve standard performance over the working day.

Standard performance is the rate of output which qualified workers will naturally achieve without over-exertion as an average over the working shift provided they know and adhere to the specified method and, they are motivated to apply themselves to their work.

This performance is denoted as 100 on the standard rating and performance scales.

Time study: Rating

It should be noted though that the “standard pace” applies to particular workers (with good physique, physical conditioning) working in appropriate environment.

In practice, because of the inherent dissimilarities amongst workers, the rate of work is never the same throughout the working day.

It is not uncommon for workers to work faster at some periods of the day than they do during others. So standard performance is achieved on average over a period of time with in-built standard deviation.

In fact, working at the standard rate will not always mean moving the limbs with the same speed.

Time study: Rating

The purpose of rating is to determine from the time actually taken by the operator being observed the standard time which can be maintained by the average qualified worker and which can be used as a realistic basis for planning, and incentive schemes.

Time study is concerned with speed at which operator carries out the work, in relation to the concept of normal speed.

“Speed” here means the effective speed of operation.

Factors affecting rate of working

Factors outside the control of workers include: Variation in the quality or other characteristics of the material used,

although they be within the prescribed tolerance limit. Changes in the operating efficiency of tools or equipment within their

normal life. Minor and unavoidable changes in methods or conditions of

operations. Variation in the mental attention for the performance of elements. Changes in the climatic and other conditions.

Factors affecting rate of working

Factors within worker’s control: Acceptable variation in the quality of the process/product. Variation due to worker’s ability. Variation due to ability of mind, specifically attitude.

Optimum pace at which the worker will work depends on – The physical effort demanded by the work. The care required on the part of the worker. Training and experience.

Rating factor

The figure 100 represents standard performance. If the operator is apparently performing with less effective speed, than

the assigned factor is less than 100. If, on the other hand, the effective rate of working is above standard,

the operator gets a factor above hundred. Essential idea being:

Observed time x Rating = Constant

Rating factor

This constant is known as the basic time:

So, depending on the rating assigned for the operator, the basic time can either be less than or greater than the observed time.

Time Basic Rating Standard

Rating timeObserved x

Work content

The work content of a job or operation is defined as: basic time+ relaxation allowance+ any allowance for additional work (e.g. the part of relaxation allowance that is work related).

Standard time is the total time in which a job should be completed at standard performance – i.e. work content, contingency allowance for delay, unoccupied time and interference allowance.

Allowance for unoccupied time and interference may not be frequently included in the standard time calculations; however, the relaxation allowance is.

Standard time constituents

A contingency allowance is a small allowance of time which may be included in a standard time to meet legitimate and expected items of work or delays, precise measurement of which is uneconomical because of their infrequent or irregular occurrence.

Contingency allowance for work could include fatigue allowance; whereas the allowance for delay could be dependent on the workers.

Typically contingency allowances are very small and are generally expressed as percentage of the total repetitive minutes of the job.

Standard time constituents

Contingency allowance could be no more than 5%, and should only be given where the contingencies cannot be eliminated and are justified.

Standard time constituents

Relaxation allowance is an addition to the basic time intended to provide the worker with the opportunity to recover from the physiological and psychological effects of carrying out specified work under specified conditions and to allow attention to personal needs.

The amount of the allowance will depend on the nature of the job. One of the major additions to the basic time. Industrial fatigue allowance, in turn, forms a major portion of the

relaxation allowance. Relaxation allowances are also given as percentages of the basic

times.

Standard time constituents

Typical values of relaxation allowance are 12-20%. In addition to including relaxation allowances, short rest pauses could

be added over the period of work for an operator.

Other allowances

Start-up / shut-down allowance Cleaning allowance Tooling allowance Set-up / change-over allowance Reject / excess production allowance Learning / training allowance Policy allowance is an increment, other than the bonus increment,

applied to standard time to provide a satisfactory level of earning for certain level of performances under exceptional conditions.

Standard time

Now, we can add all the constituents to arrive at the standard time for a job.

Standard time = observed time + rating factor + relaxation allowance + work related contingency allowance + delay related contingency allowance.