work study slides im eee chem 13

5/27/2018 Work Study Slides IM EEE Chem 13

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Productivity

Ratio between output and input.

Output : desired

Input : Man, machine, material, etc.


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Concept of Work Content

BASIC Work Content: is the minimum time

theoretically required to do a job or operation. This cannot bereduced. This results only if (i) the design and the

specifications are perfect, (ii) process of manufacture is

exactly followed and (iii) no loss of working time occurs due

to any reason.

The actual time required to complete an operation or job is

more than the basic time in practical situations. This additional

portion is called the excess work content.

The amount of work contained in a given job is referred

to as work content and is measured in man-hours or machine-hours.


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Reasons for Excess Work Content

A. Work content added due to defects in

design or specs of a product

i. Bad design of product

ii. Lack of standardisation of components

iii.Incorrect specs & quality standardsiv.Faulty design of components

B. Work content added due to

inefficient methods of manufacture

i. Improper selection of manufacturing

process/machine

ii. Wrong selection of tools

iii.Improper layout of the shop/factory

iv.Inefficient methods of material handling

C. Ineffective time added due to

shortcomings of management

i. Bad working conditions, ii) frequent prod.

Interruptions due to breakdown, iii)poor prod.

planning and control, iv) lack of safety

measures, v) lack of quality mindedness, vi)

lack of instruc-tion vii) frequent changes in set-

ups, viii) lack of performance standards, ix)

shortage of materials / tools.

D. Ineffective time added due to reasons

attributed to workmen

i. Unauthorised absence from work, ii)substandatd performance, iii) careless-ness in

working, iv) unnecessary wastage of time /

idleness.


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Productivity

Productivity of man

Total timeof operation

under

existing

conditions

Basic Work Content

of product and / or

process

Work Content added by

defects in design of

product or process

Work Content added by

inefficient methods of

operations

Ineffective Time due tomanagement problems

Ineffective Time within

control of workers


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Productivity

Productivity of man

Bad design of product

Lack of standardization

Incorrect Quality Standards

Excess Material

Wrong Machine

Incorrect Processes operation

Wrong Tools

Bad Layout

Wrong Working method


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ProductivityProductivity of man

Excessive Product Variety

Lack of Standardization

Design Changes

Wrong / Lack of Planning

Unavailability of Raw

Material

Plant Breakdown

Bad Plant Condition

Bad Working Condition

Accidents

Absence, Late coming and / or

Idleness

Careless Workmanship

Accidents


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Techniques to reduce Work Content

A. Mngt technique to reduce work contentdue to product

i. Product development,

ii. standardisation,

iii. value analysis,

iv. market/consumer research

B. Mngt technique to reduce work contentdue to process/ methods

i. process planning ,

ii. method study

C. Mngt techniques to reduce ineffectivetime due to shortcomings ofmanagement

Product standardisation andsimplification, productspecialisation, iii) standardisation of

components, iv) production planning& control, v) materials control, vi)plant maintenance, vii) safetymeasures and improved workingconditions.

D. Mngt techniques to reduce ineffectivetime within the control of the workers

i) sound personnel policies, ii)Operators training, iii) safetytraining, iv) financial incentives.

The important functions of production management are setting up most

effective method of performing the operation and control the effective

utilisation of resources.


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Direct means of raising productivityApproach Type of

Improvement

Means Cost How quickly

results be

achieved?

Extent of

improvement

in

productivity

Role of Work

Study

Capital

Investment

Development

of new basic

process or

fundamental

improvement

of exiting one

Basic or

Applied

research,

pilot plant

High Generally

years

No obvious

limit

Method Study to

improve ease of

operation and

maintenance at

design stage

CapitalInvestment

Install moremodern or

higher

capacity plant

or Eqpt. Or

modernise

existing plant

Purchaseprocess

research

High Immediatelyafter

installation

No obviouslimit

Method study inPlant Layout and

to improve ease of

operation when

modernising

BetterManagemen

t

Reduction inWork Content

of the Product

ProductResearch,

developme

nt

Qlty Mngt

Method

study

valure

analysis

Not highcompare

to (1)

and (2)

above.

Generallymonths

Limitedofthe same

order as that

to be expected

from later

Method Study(and its extension

value analysis) to

improve design

for ease of

production


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Better

Management

Reduce work

content of the

process

Process

research, pilot

plant, process

planning,

Method study,

value analysis

Low Immediate Limited, but

often of a

high order

Method study to

reduce wasted

effort and time in

operating the

process by

eliminating

unnecessary

movement

Better

Management

Reduce

ineffective

time (due to

Management

or workers)

Work

measurement

Standardisatio

n, product

development,

PPC, material

control,

planned

maintenance,

personnelpolicy,

operator

training,

incentive

scheme

Low May start slowly

but effect grows

quickly

Limited, but

often of a

high order

Work

Measurement to

investigate

existing practice,

locate ineffective

time and

standards of

performance as a

basis for: a)

Planning &Control, b)

Utilisation of

Plant, c) Labour

cost control, d)

Incentive scheme


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Management approach to deal with Productivity

To eliminate the excess work content To reduce the ineffective time

The technique is known as Work Study.

Work study can be defined as the analyticinvestigation of the methods, conditions andeffectiveness of industrial work and therebythe determination of the ways in whichhuman efforts may most economically beapplied.


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Definitions.

Work Study is primarily concerned withdiscovering the best ways of doing the joband establishing standards based on suchmethods.

Work study is the technique of Methodstudy and work measurement employed to

ensure the best possible use of human andmaterial resources in carrying out aspecified activity. -ILO


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WORK STUDY.

Its a Mgt tool to achieve higher efficiency. Itprovides us a scientific approach to investigate intoforms of work with a view to increase productivity.

Concerned primarily with manual work Any industry to survive, must use latest technology &

most efficient method, improvised with a consistentaim of producing best quality goods at lower prices.

One way to improve is by efficient use of plant,equipment and Labor.


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Work Study aims at improving the existing and proposed ways of doing

work and establishment of standard time for work performance.

Work Study is the most effective tool to enhance productivity because

of the fact that it is a straight forward way of increasing the productiveefficiency of the organisation and also considers all the factors

influencing productivity.

Work Study comprises of method study and work measurement.


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WORK STUDY

Work study is simply study of work.

It is analysis of work dividing it into smallerparts followed by rearrangement of these parts

to give the same effectiveness at a lesser cost. Work study examines both the method and

duration of the work involved in the process.

Work study is a powerful tool for simplificationof work Robert Owen, Taylor and Bedeaux gave their contributions to this topic.


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Work study and the Worker

Why workers resist the work study:

It will change their familiar work methods.

Many workers resent being timed.

Fear of being fired.

Wh i W k S d ?


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What is Work Study? Production system focuses on increasing the efficiency by

maximizing the output per hour of employee effort.

The important functions of Production Management are setting upthe most effective method of performing the operations (std.method) and their control for effective utilization of resources.

Work Study (WS) is one of the most important managementtechniques which is employed to improve the activities inproduction. It provides a scientific approach to investigate into allforms of work, with a view to increase productivity.

The main objective of WS is to assist the management in the

optimum use of the human & material resources.

Main aim of this WS is to finding the best & most efficient way ofusing available resources i.e. men, material, money & machinery.


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What is Work Study? It is especially concerned with productivity. To increase

the productivity from a given quantity of resources.

Workstudy is ageneric term for thetechniquesofmethod study and work measurement. Thesetechniques are used in the examination of human

workinallitscontexts.Theyleadsystematicallytotheinvestigation of all the factors which affect theefficiencyandeconomyattheworkplaceinordertoaffectimprovement.

Work Study is the systematic examination of themethods of carrying on activities so as to improve theeffective use of resources and to set up standards ofperformance for the activities being carried out.

C f W k S d


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Components ofWork Study

It has threeaspects

1. More effective use of plant & equipment

2. More effective use of human effort3. Evaluation of human work


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Work Study - Basic Procedure8 step process

RECORD

EXAMINE

DEVELOP

MEASURE

DEFINE

INSTALL

MAINTAIN

SELECT

Most economical method

Job or process to be studied

All details concerning Job using various techniques

Recorded facts critically by asking questions

Amount of work involved & set

standard time to do the job

New method & standardtime

New method as a

standard practice

New method as

agreed standard


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Applications of work Study

Industries: production operations, research and development

Marketing: sales & distribution.

Offices: stores & warehouses.

Material handling

In designing field

Building & other construction

Transport

Hospital Army

Agriculture


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Advantages/ Objectives of Work Study


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METHOD STUDY

Method Study (MS) is the systematic recording and

critical examination of existing and proposed ways ofdoing work, as a means of developing and applying

easierand more effective methods and reducing costs.

MS aims at determining the most effective method of

performing the job, most logical layout of manufacturing

facilities, uninterrupted flow of materials throughout the

organization. It is concerned with reduction of work content

and establishing the one best way of doing the job.

MS is a collection of analysis techniques focusing onimproving the effectiveness of man and the machine.


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Method Study Methods engineering /work design

Breakdown of operation into components

Systematic analysis of each component

Eliminates un-necessary operations

It is systematic recording & examination of

existing methods of doing work and developing

more effective methods - BSIMS addresses three broad areas:

1. It is a diagnostic tool (location of faults)

2. It is a remedial tool (improve situation)

3. It is a constructive tool (set standards)


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Objectives of Method Study1. Improvement of manufacturing processes and procedures.

2. Improvement of working conditions.3. Improvement of plant layout and work place layout.

4. Reducing the human effort and fatigue.

5. Reducing material handling6. Improvement of plant and equipment design.

7. Improvement in the utility of material, machines and manpower.

8. Standardization of method.

9. Improvement in safety standard.


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Method Study

Method study is the technique of systematicrecording and critical examination of existing and

proposed ways of doing work and developing an

easier and economical method.

Method study examines the way a task (changing theclutch on a car, preparing a flower bed for planting,

cleaning a hotel room) is done. The industrial

engineer has an eye on operational efficiencies and

costs, quality of processes, service reliability, staffsafety etc. Method study techniques are applicable

from factory/workshop manufacturing to cabin crew

activities.

Method Study

Flow Chart


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Method Study Procedure

SELECT

RECORD

EXAMINE

DEVELOP

DEFINE

INSTALL

MAINTAIN

The work which can be studied with economic advantage

All relevant facts about the job / operation

The facts critically (purpose, place, sequence,person)

verify at regular intervals that the improved method is in use

Plan, arrange and implement the new method as Std.

method, procedure, layout, equipment, workingconditions, materials, quality, instructions

A record of improved method,

under prevailing conditions.

Reexamine and select the

best method


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BASIC PROCEDURE FOR METHOD STUDY

Thebasicprocedureforconductingmethodstudyisasfollows:

1.Selectthe work to be studied.

2. Record all facts about the method by directobservation.

3.Examinethe above facts critically.

4. Develop the most efficient and economic

method.5.Definethe new method.

6.Installthe new method as std. practice

7.Maintainthe new method by regular checking.

Method Study

Flow Chart


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Selecting the work to be studied

There are three factors that should be kept in mindwhile selecting a job for method study:

1. Economic or cost-effective considerations.

2. Technical considerations.

3. Human considerations.

1. Economic considerations:

It is obviously a waste of time to start or continue a

long investigation if the economic importance ofa job is small.

Questions that should always be asked are:

Will it pay to begin a method study of this job? Or

Will it pay to continue this study?


Obvious choices for study are:


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Obvious choices for study are:

A. Keyprofit-generating or costly operations or ones with the largest

Scrap/waste rates.

B. Bottlenecks which are holding up other production operations, or

lengthy operations that consume a great deal of time. C. Operations involving repetitive workusing a great deal of labour

and ones that are likely to run for a long time.

D. Movements of material over long distancesbetween workstations,

those involving the use of a relatively large proportion of labor or

which require repeated handling of material.

SelectPossible Results:

* Increased production rate * Reduced cost

* Less labor, materials, or equipment * Improved quality

* Improved safety * Reduced scrap

* Improved standards of cleanliness

One of the easiest techniques that can be used to identify key operations aslisted in part (A) is the Pareto analysis (sometimes also referred to as theABC analysis of value analysis).

The same observation can be extended by saying that among all theoperations in a given plant a small number account for the largest share of

cost or ofprofit, or the largest percentage ofwaste.


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To illustrate the point we will consider the following example.

Let us assume that a certain enterprise produces 20 different products. Eachof these products generates a certain profit.

By listing the annual production and profit contribution one obtains theresults shown in table 6.

The next step consists of rearranging these items in descending order ofimportance according to profit. The result would then appear like the oneshown in table 7.

From table 7 it can be seen that three products only, listed as A items,

account for 60 per cent of the profit. These are the most profitable and any improvement in methods of

producing these particular products would reflect highly on profits. Theywould be a priority for study.

Products listed under B, which are seven in number, contribute 25 percent of the profit. They could then assume a second importance, while

products C would command the last priority since their contribution toprofit is minimal. The same type of analysis can be conducted to determine the most costly

products or processes or the products or processes that yield the highestwaste.

Those would then become a priority for study by the work study specialist.


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St d d Li t f i t t b d h l ti


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1. Product and operation

2. Person who proposes investigation

3. Reason for proposal

4. Suggested limits of investigation

5. Particulars of the job

a) How much is produced or handled per week?b) What percentage is this of the total produced or handled in the shop or plant?

c) How long will the job continue?

d) Will more or less be required in future?

e) How many operatives are employed on the joba) Directly

b) Indirectly

f) How many operatives are there in each grade and on each rate of pay?

g) What is the average output per operative (per team) per day?

h) What is the daily output compared with the output over a shorter period (an hour)?

i) How is payment made? (team-work, piece work, premium bonus time rate, etc.)

Standard List of points to be covered when selecting

a job for Method Study(Sample list which needs to be adapted to individual needs)


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Standard List of points to be covered when selecting a job for Method Study

(contd.2)

j) What is the daily output

a) Of the best operative?

b) Of the worst operative?

k) When were production standards set?

l) Has the job any especially unplesant or injurious features? Is it

unpopular (a) with workers, (b) with supervisors?

6. Equipment

a) What is the approximate cost of plant and equipment?

b) What is the present machine utilisation Index?

7. Layout1. Is the existing space allowed fo the job enough?

2. Is extra space available?


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8. Product

1. Are the frequent design changes causing modifications?

2. Can the product be altered for easier manufacture?

3. What quality is demanded?4. When and how is the product inspected?

9. What savings or increase in productivity may be expected from a

method improvement?

a) Through reduction in the work content of the product or process.

b) Through better machine utilisation.

c) Through better utilisation of labour.

Standard List of points to be covered when selecting a job for Method Study

(contd. 3)

2. Technical or technological considerations:


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gOne of the important considerations is the desire by management to acquiremore advanced technology, i.e. in equipment or in processes.

Therefore, management may want to computerize its office paperwork or itsinventory system, or to introduce automation in the production operations.

Before such steps are taken, a method study can point out the most importantneeds of the enterprise in this respect.

The introduction of new technology should therefore constitute an importantfactor in the choice of methods of work to be investigated.

Based on the technical knowledge of the process

Jobs having inconsistent quality, Operations generating lot of scrap, Frequentcomplaint from workers, Extensive paperwork, Repetitive work (automation),

Hazardous work etc.

3. Human considerations: Most difficult to foretell, because of mental andemotional nature.

Certain operations are often a cause of dissatisfaction by workers.

Select an unpopular job - That may bring on fatigue or monotony or may beunsafe to operate or inconsistent earnings.

The level of satisfaction should point to a need for method study. In a similarfashion, a choice of a particular job for study may lead to anxiety or ill feeling.

The suggestion given here is to leave it alone.


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2. Record:All the details about the existing method are recorded. This isdone by directly observing the work. Records are useful for BEFORE

and AFTER comparison to assess effectiveness of proposed method.

Recording techniques are designed to simplify & standardize recording

work.

COMMONLY USED RECORDING TECHNIQUES

1. Outline Process Charts

2. Flow Process Chart

3. Two Handed Process Chart

4. Multiple Activity Chart

5. Simo Chart

6. Flow Diagrams

7. String Diagrams

8. Cyclegraph

9. Chronocyclegraph

10. Travel Chart

Man Type

Material Type

Equipment Type

USING TIME SCALE


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Typical Industrial problems and appropriate method study

technique

Type of Job Examples Recording Technique

Complete sequence of

manufacture

Manufacture of an electric

motor from raw material to

dispatch

Outline Process Chart

Flow Process Chart

Flow Diagram

Factory Layout: Movement

of materials

Movement of diesel engine

cylinder head through all

machining operations

Outline Process Chart

Flow Process Chart (Mat)

Flow Diagram

Travel Chart, Models

Factory Layout: Movement

of Workers

Cooks preparing meals in a

restaurant kitchen

Flow Process Chart (Men)

String diagram

Travel Chart

Handling of Materials Putting materials into &

taking them out of stores

Flow Process Chart (Mat)

Flow DiagramString diagram

Workplace layout Light assembly work on a

bench

Flow process Chart (Man)

Two handed process Chart

Multiple activity Chart

Simo Chart, Cyclegraph


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Type of Job Examples Recording Technique

Automatic machine

operation

Assembly line, operator

looking after semi-automatic lathe

Multiple activity chart

Flow Process Chart (Eqpt)

Movement of operatives at

work

Female operatives on short-

cycle repetition work

Films, Film analysis,

Simo Chart

Memotion photography

Micromotion analysis

Typical Industrial problems and appropriate method study technique

Symbols are used to represent the activities like operation, inspection,

transport, storage and delay.

Grouping of activities: Five sets of activities can be grouped in two

categories

Those in which something actually happens to the work-piece (it is

moved, worked upon orexamined)

Those in which it is not being touched (in storage or in delay)Objective is to maximize proportion of do activities.

All other activities, however necessary, are considered non-productive



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3. Examine: Critical examination is done by questioning

technique. This step comes after the method is recorded by

suitable charts and diagrams. The individual activity is

examined by putting a number of questions.

Critical examination is conducted wherein each activity, in turn, being

subjected to a systematic and progressive series of questions.

The questioning sequence used follows a well-established pattern

which examines:

the PURPOSE for which

The PLACE at which

The SEQUENCE in which the activities are undertaken.the PERSON by whom

the MEANS by which


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PRIMARY QUESTIONS

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.

SECONDARY QUESTIONS


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SECONDARY QUESTIONS

The secondary questions cover the second stage of the questioning

technique, during which the answers to the primary questions are

subjected to further query to determine whether possible alternatives of

place, sequence, persons and means are practicable and preferred as a

means of improvement upon the existing method.

PURPOSEWhat else might be done?

What should be done?

PLACEWhere else might be done?

Where should be done?

SEQUENCEWhen else might be done?

When should be done?

PERSON Who else might be done?Who should be done?

MEANSHow else might be done?

How should be done?

These questions, in the above sequence, must be asked systematically every time

a method study is undertaken. They are the basis of successful method study.


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4. Develop : Answer to the questions will result in thedevelopment of alternatives and of a better method. Develop

the most efficient and economic method.

Ex: Sending letters to customers.

5. Define:Once a complete study of a job has been made and a

new method is developed, it is necessary to obtain the

approval of the management before installing it. The work

study man should prepare a report giving details of the

existing and proposed methods, reasons for change,

advantages, limitations, savings expected, tools & equipment

required etc..

DEFINING THE IMPROVED METHOD


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DEFINING THE IMPROVED METHOD

The report should show:

1. Relative costs in material, labour and overheads of thetwo methods, and savings expected.

2. The cost of installing the new method, including thecost of new equipment and of re-laying out shopsor working areas

3. Executive actions required to implement the newmethod.

It should also give details regarding :

1. The tools and equipment to be used2. A description of the method

3. A diagram of the work place layout, jigs/fixtures etc.



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6. Install :This step is the most difficult stage in method study.

Here the active support of both management and trade union

is required. Here the work study man requires skill in gettingalong with other people and winning their trust.

a) Gaining acceptance of the change by the Management

b) Gaining acceptance of the change by the workers

c) Maintaining close contact with the progress of the job until satisfiedthat it is running as intended

7. Maintain:The work study man must see that the new method

introduced is followed. The workers after some time may slip

back to the old methods. This should not be allowed. The newmethod may have defects. There may be difficulties also. This

should be rectified in time by the work study man.


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Recording Techniques in

Method study

Outline processchart

Flow process

chart

Material type chart

Machine type chart

Two -Handed

process chart

Using a time scale

Multiple activity

chart

Simo chart

P.M.T.S. chartMan type chart

Indicating

Process

Sequence

Diagrams

indicating

movements

String Diagram

Flow Diagrams

Travel Chart

Chrono-cycle

Graph

Cycle Graph

S b l d i Ch t


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OPERATION:A large circle indicates operation. An operation takes place when there

is a change in physical or chemical characteristics of an object. Occurs when an object is

intentionally changed in one or more of its characteristics. An assembly or disassembly isalso an operation. When information is given or received or when planning or calculating

takes place it is also called operation.

Example: Reducing the diameter of an object in a lathe. Hardening the surface of an

object by heat treatment. Drilling, Painting, Chemical reaction, Data Entry, Cutting, Sorting,

etc.

INSPECTION:A square indicates inspection. Inspection is checking an object for its

quality, quantity or identifications.

Example:Checking the diameter of a rod. Examine the quantity or quality, read steam

gauge on boiler, detect the defectives. Counting the number of products produced. of an

object by heat treatment.

Symbols used in Charts

Symbols used in Charts contd.


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Symbols used in Charts contd.

STORAGE: An equilateral triangle standing on its vertex represents storage. Storage

takes place when an object is stored and protected against unauthorized removal.

Example:Raw material in the store room, finished products inventory, archived documents.

DELAY: A large capital letter D indicates delay. This is also called as temporary

storage. Delay occurs when an object or operator is waiting for the next activity. Occurswhen the immediate performance or the next planned action does not take place.

Example:An operator waiting to get a tool in the stores. Work pieces stocked near the

machine before the next operation. Work In Process inventory waiting to be processed,

Employee waiting for an elevator, Waiting for accumulation of a certain quantity for

packaging

TRANSPORTATION:An arrow indicates transport. This refers to the movement of an

object or operator or equipment from one place to another. When the movement takes

place during an operation, it is not called transport.Example:Moving the material by a trolley Operator going to the stores to get some tool,

Using elevator, carrying, moving with material handling devices

.

ASME Standard Symbols


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y


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Why Charts?

It gives a complete picture of what is being done andhelps to understand the facts and its relationship to oneanother.

Details on the chart must be obtained from directobservation. Should not be from memory.

Neatness and accuracy is important.

Increased value if following is included:

1. Product, equipment details (code#, drawing#)

2. Job or process being carried out

3. Location and time (date) of the study

4. Observers name

5. Chart reference number

(A) MACRO MOTION CHARTS


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(A) MACRO MOTION CHARTS

1.Operation Process Chart

Also called Outline process chart

Birds eye view of whole process

Records only major activities and inspections

Uses only two symbols i.e. operations & inspection

Constructed by placing symbols one below another

Uses

Visualize sequence of operations & inspections in process

Know where operations selected fits into the entire

process

OPERATION PROCESS / OUTLINE PROCESS Chart:


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OPERATION PROCESS / OUTLINE PROCESS Chart:Example : Manufacture of Electric Motor

1

4

7

Conventions followed in

preparing the chart

1. Write title at the top of the chart.

2. Begin the chart from the right handside top corner.

3. Represent the main component at

the right extreme.

4. Represent the sequence of

operations and inspections by their

symbols. Connect them by vertical

flow lines.5. Record the brief description of the

activity to the right side of the

symbols.

6. Note down the time for each activity

to the left of the symbol.

7. Number all operations in one serial

order. Start from the right hand top(from number 1).

8. Similarly number all inspections in

another serial order (starting from 1).

9. Continue numbering, till the entry of

the second component.

10. Show the entry of purchased parts

by horizontal lines.

4

7 11114

4

Record- Example


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Outline Chart

Face, turn, cut

Face opposite end

Dimension and finish

Straddle mill four flats

Remove burr

Final inspection of machining

Degreasing

Cadmium plating

Final check

Face both sides

Drill hole

Final check

Assemble and drill

Turn shank

Remove chip

Dimensions

Degreasing

Cadmium plating

Final check

Fit stop pin

Final check

Switch Rotor

Ex: Outline process chart of Plywood manufacture


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Ex: Outline process chart of Plywood manufacture

Record- Example


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Outline Chart

2. Flow Process Chart


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A flow process chart is a graphical representation of the sequence of all the

activities (operation, inspection, transport, delay and storage) taking place in a

process.

It is the detail version of outline process chart recording all the events.

Process chart symbols are used here to represent the activities.

Gives sequence of flow of work.

Constructed same as operation process chart

Three types1. Material type

(records how the material is handled or treated).

2. Man type

(records what the worker does).

3. Equipment type

(records how the equipment or machine is used).

Uses Reduce idle time and delays

Reduce distance travelled

Reduce production cycle time

To relocate inspection stages

1. The details must be obtained by directobservationcharts must not be based

on memory.2. All the facts must be correctly recorded.

3. No assumptions should be made.

4. Make it easy for future reference.

5. All charts must have the following details:

(a) Name of the product, material orequipment that is observed.

(b) Starting point and ending point.

(c) The location where the activities takeplace.

(d) The chart reference number, sheetnumber and number of total sheets.

(e) Key to the symbols used must bestated.

Ex: Machine/ Equipment Flow Process Chart: Biscuit Making


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Ex: Machine/ Equipment Flow Process Chart: Biscuit Making

Flow Process Chart - Example


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Distance in

meter

Symbol Process description

10 Move to cabinet

- Get loaf of bread

- Remove two slices of bread

- Lay slices on table top

- Close loaf of bread

- Replace loaf on shelf

- Open butter

- Spread butter on top slice- Inspect sandwich

- Move to serving area

10 Serve sandwich

Ex: Process chart for making a Cheese Sandwich


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Ex: Flow Process ChartEmergency ward

1 X Enter emergency room, approach patient window2 X Sit down and fill out patient history

3 X Nurse escorts patient to ER triage room

4 X Nurse inspects injury

5 X Return to waiting room

6 X Wait for available bed

7 X Go to ER bed

8 X Wait for doctor

9 X Doctor inspects injury and questions patient

10 X Nurse takes patient to radiology

11 X Technician x-rays patient12 X Return to bed in ER

13 X Wait for doctor to return

14 X Doctor provides diagnosis and advice

15 X Return to emergency entrance area

16 X Check out

17 X Walk to pharmacy

18 X Pick up prescription

19 X Leave the building

0.50 1510.0 -

0.75 40

3.00 -

0.75 40

1.00 -

1.00 60

4.00 -

5.00 -

2.00 200

3.00 -2.00 200

3.00 -

2.00 -

1.00 60

4.00 -

2.00 180

4.00 -

1.00 20

Process: Emergency room admission

Subject: Ankle in jury pat ient

Beginning: Enter emergency roomEnding: Leave hospi ta l

Stepno.

Time(min)

Distance

(ft)

Summary

Number

of stepsActivity

Time

(min)

Distance

(ft)

Step description

Insert Step

Append Step

Remove Step

Transport 9 11 815

Operation 5 23

Inspect 2 8

Store

Delay 3 8

3.Two Handed Process Chart


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It is the process chart in which the activities of two hands of the operator are

recorded.

Motions of both hands of worker are Right hand-Left hand chart recorded

independently.

It shows whether the two hands of the operator are idle or moving in relation to

one another, in a timescale.

It is generally used for repetitive operations.

Confined to work carried out at a single workplace Visualize complete sequence of activities in repetitive task

Study work station layout

Operation:Represents the activitiesgrasp, position, use, releaseetc. of a tool, component or material.

Transport:Represents the movement of the hand or limb to or from the work or a tool or material.

Delay:Refers to the time when the hand or limb is idle.

Storage (Hold):The term holdis used here instead of storage to refer to the time when the work is held byhand.

The activityinspectionby hand is considered as an operation. Hence, the symbol for inspection is not usedin this

chart. Two-handed process chart can be used for assembly, machining and clerical jobs.

Ex: Two-Handed Process Chart


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Ex: Two Handed Process Chart

Summary of the number of each activity can be tabulated at the bottom of the chart. The chart is first drawn for the existing method.

This chart is analyzed and if it is found that one hand is over loaded than the other, modification are done in the layout of the

workplace or in the sequence of activities. Then a new chart is made for the proposed cycle. This assists in finding a better method of

performing the task and to train the operator in the preferred method.

1. Provide all

information about

the job in the chart.2. Study the operation

cycle a few times

before starting to

record.

3. Record one hand

at a time.

4. First record theactivities of the

hand which starts

the work first.

5. Do not combine the

different activities

like operations,

transport etc.

Example of a Two-Handed Process Chart:


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p(Cutting Glass Tubes)

Example of a Two-Handed Process Chart:


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p(Cutting Glass Tubes)

Ex: Two-handed process Chart


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Ex: Left-Hand-Right-Hand Chart


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Ex: Left Hand Right Hand Chart

Standard format of a Two-handed process f lowchart


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Standard format of a Two handed process flowchart

E l f T h d d fl h t


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Example of a Two-handed process flowchart

F ixing Screw on a Assembly

Example of a Two-handed process flowchar t


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p p

F ixing Screw on a Assembly

Example of a Two-handed process flowchart


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4 Multiple Activity Chart or Man machine Chart


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4. Multiple Activity Chart or Man-machine Chart A man-machine/ Multiple Activity Chart chart is a chart in which the activities of

more than one worker or machine are recorded.

Activities are recorded on a common time scale to show the inter-relationship.

It is used when a worker operates a number of machines at a time. It is also

used when a number of workers jointly do a job. (Determine no. of machines

handled by one operator).

The chart shows the idle time of the worker or machine during the process.(Study idle time)

Work load is evenly distributed among the workers or machines by this the idle

time of worker or machine is reduced. Multiple activity chart is very useful in

planning team work in production or maintenance. (Determine no. of operators

required). Only two symbols are used in man-machine/ Multiple Activity Chart :

Working Idle

Purpose of Multiple Activity Chart


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Purpose of Multiple Activity Chart

To detect the idle time on machine and workers (The chart shows the exacttime relationship between the working cycle of the person and operating

cycle of the machine).

To optimize work distribution between workers and machines.

To decide number of workers in a group.

To balance the work team

To examine the activities. It is used for recording the complex movements of material or men.

Used to find out the most economical route.

Application ofMultiple Activity Chart:

Planning team work. Plant repair & maintenance.

Job construction.

It is used to check whether the work station is correctly located.


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Example of Multiple Activity Chart:Facing & Centering Operations


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Time Operator Machine 1Washer

Machine 2Dryer

# Sec Load clothes & detergent in

machine 1

Being loaded Idle

Idle Run Idle

- Remove clothes from machine 1 Being unloaded Idle

- Load clothes into machine 2 Idle Being loaded

- Load clothes & detergent into

machine 1

Being loaded Run

- Idle Run Run

- Remove clothes from machine 2 Idle Being unloaded

- Hang clothes Idle Idle

Multiple activity chart for doing three loads of laundry

Ex: Worker-Machine Chart for a Gourmet Coffee Store


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Diagrams


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Diagrams

Diagrams gives pictorial view of the layout of workplace on which

locations of different equipment, machines etc. are indicated.

The movement of subject(man or machine) is then indicated on the

diagram by a line or a string.

The diagram are valuable in highlighting the movement so the analystcan take steps to simplify or reduce it so as to obtain saving in time.

The most commonly used method study diagrams are:

o Flow diagram

o String diagramo Travel chart

o Cyclegraph and Chronocyclegraph

Types of LAYOUT


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FOUR MAJOR TYPES OF LAYOUT:

(A) layout by FIXED position, material to be processed dont

travel round the plant but stays in one place. When product is

bulky, heavy and only few units are made (Ship Building,

Aircraft construction, Manufacture of large Diesel engines)

(B) layout by PROCESS, Operations of the same nature are

grouped together. Cutting in garment industry, stitching inanother area. This is mostly chosen where great many products

share the same machine.

(C) Layout by PRODUCT, or LINE layout (Mass production) all

m/c & equipment necessary is set in the same area and in the

sequence of manufacturing process.

(D) layout by GROUP. Group production methods.

Types of LAYOUT


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1 Flow diagram


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1.Flow diagram

Drawing of working area & showing location of various activities

Shows the route followed and selects the optimum one Study different layout and selecting optimum one

Study traffic and frequency over different routes

Procedure :

Layout of workplace is drawn to scale

Relative positions of the m/c tools, storage & inspection benches are

marked on the scale

Path followed by the subject under study is tracked by drawing lines

Each movement is serially numbered & indicated by arrow for direction

Different colors are used to denote different types of movements

Flow diagram


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Its a top view of the work area correctly indicating the positions of

machining and other locations affecting the movement of subject.

Therefor it gives on-the-spot observation of the paths of movement

of product sometimes using symbols of process charts.

80


81/1782. String diagram


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Scale layout drawing

Length of a string is used to record extent & pattern of movements of a

worker within a limited area.

Movements difficult to trace on flow diagram can be shown Shows the route followed and selects the optimum one

Study different layout and selecting optimum one

Study traffic and frequency over different routes

Procedure :

A Layout of workplace is drawn to scale

Pins are fixed into boards to mark locations of workstations

Pins are also driven at turning points of the routes A measured length of thread is taken to trace the movements

The distance covered by object is obtained by measuring the remaining

part of the thread and subtracting it from original length


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START

END

83


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DRILL+CUT

FOLD

RIVET

MARK

IQC

STACK

OQC

SHEETMETAL

STAR

END

START

END

Comparison


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SHEET METALCHECK = 10 ft

CHECKCUT = 12 ft

CUTDRILL = 9 ft

DRILLFOLD = 10 ft FOLDRIVET = 10 ft

RIVETCHECK = 14 ft

CHECKSTACK = 12 ft

TOTAL = 67 ft

SHEET METALIQC = 2.8 ft.

IQCMARK = 5 ft.

MARKDRILL &CUT= 6ft

DRILL &CUTFOLD = 6ft.

FOLDRIVET = 5 ft.

RIVETOQC = 5 ft.

TOTAL = 30 ft.

Comparison

Scale 1cm = 2feet

Before After


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86


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87


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88


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89


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90


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91

CLASSIFICATION OF MOVEMENTS


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Class Pivot Body member(s) moved

1 Knuckle Finger

2 Wrist Hand and Finger

3 Elbow Forearm, hand and fingers

4 Shoulder Upper arm, forearm, hand and

fingers

5 Trunk Torso, Upper arm, forearm, hand and

fingers


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93


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94


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95


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96


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97


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99


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100


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101


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102


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103


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104


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105


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106


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107


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108


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109


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110


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111


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112


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113


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Improve Productivity, Reduce Costs, Improve Profits

Work Measurement:

Work measurement is the application of a set of techniques

designed to establish the quantum of work to be done in a given

time for a qualified worker to carry out specified jobs, under

specified conditions at a defined level of performance.


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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 andmanagement.

All this leads to decreased productivity.


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Time Study/ Work Measurement

Work measurement is identified as a scientificmethod of fixing standard of production orstandard time for a given job.

To manage, one must measure first.

Work measurement means the application of aset of techniques intended to establish the

i. Amount of work to be done by an operator

ii. At a given time

iii. Under a specific condition and

iv. At defined level of performance.


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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!


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WM is also used to set standard times to carry out the

work, so that any ineffective time is not included later. Any addition to 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 earnedbad 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 ignoredtraditionally.

f k


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Use of Work Measurement

1. Assessment of manpower requirements

2. Planning

3. Estimation of Production costs

4. Cost reduction and cost control

5. Improved methods

6. Basis for Incentives

7. Comparing alternative methods

8. Standard data9. Performance appraisal

10. Training needs assessment

Work Measurement

Work Measurement (WM) is the application of


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Work Measurement (WM) is the application oftechniques designed to establish the time for a qualified

worker to carry out a specified job at a defined level ofperformance. (British Standard Glossary of Terms in Work Study)

The purpose of WM is to reveal the nature & extent of ineffective time so that action can be taken to reveal the

eliminate it and then set standards of performance.

Two critical issues in work study:

1. Method study should precede the work measurement,

always.2. Elimination of management controllable ineffective time

should precede the elimination of the ineffective time within

the control of the workers.

To reduce the amount of ineffective time

PURPOSE OF WORK MEASUREMENT


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Provides management with a means of identifying the causes of

ineffective time.

1. To find ineffective time in a process2. To set standard for output level

3. To plan workforce needs

4. To evaluate workers performance

5. To determine available capacity

6. To determine price or cost of product7. To compare work methods

8. To facilitate operations schedules

9. To establish wage incentive schemes

10. Training of new employees

11. Checking employee progressGeneral criteria where WM can be applied for measurable jobs:1. Work should be identifiable in terms of No. of units a worker performed,

2. Work should be performed in a reasonably consistent manner, and

3. There should be considerable volume of work to justify performing the study.

Use of Work Measurement:

1. Assessment of manpowerrequirements

2. Planning

3. Estimation of Production

costs

4. Cost reduction and cost

control

5. Improved methods

6. Basis for Incentives

7. Comparing alternative

methods

8. Standard data

9. Performance appraisal

10. Training needs assessment

THE TECHNIQUES OF WORK MEASUREMENT


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1. Stop-watch time study

2. Work sampling

3. Predetermined time standards(PTS)

4. Standard Data

The choice of technique depends on:

The level of details desired and The nature of work itself

Direct observationalmethods

Indirect

methods

Steps in Work Measurement

Select the job to be timed (B l k i i i j b j b i h f l


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Selectthe job to be timed (Bottleneck operations, repetitive jobs, jobs with great amount of manuallabour, frequent overtime, new job/component, if cost of operation is high, introduce/revise incentive scheme etc)

Standardise the method of working; Select OperatorRecordall the relevant data relating to the circumstances in which the work is

being done, the method and the elements of activity in them

Examinethe recorded data and the detailed breakdown critically to ensure that

the most effective method and motions are being used and that unproductive and

foreign elements are separated from productive elements

Measurethe quantity of work involved in each element, in terms of time, using

the appropriate work measurement techniques

Compilethe standard time for the operation which will include time

allowances to cover relaxation, personal needs, contingencies, etc.

Defineprecisely the series of activities and methods of operations for which the

time has been compiled and issue the time as standard for the activities and

methods specified.

TIME STUDY

Basic Steps


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1. Obtaining and recording all available information about the job,

operator and the surrounding conditions likely to affect theexecution of the work

2. Recording the complete description of the method, breaking

down the operation into 'elements'

3. Measuring with a stopwatch and recording the time taken bythe operator to perform each 'element' of the operation.

4. Assessing the rating

5. Extending observed time to 'basic times'

6. Determining the allowances to be made over and above the basictime for the operation

7. Determining the 'standard time' for the operation.

Time StudyTime Study is the application of WM technique to establish time

for a QUALIFIED WORKER to carry out a SPECIFIED TASK


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for a QUALIFIED WORKER to carry out a SPECIFIED TASK

under SPECIFIED CONDITIONS and at the DEFINED LEVEL

OF PERFORMANCE. How much time one should take to reach Wgl Stn?

* Breaking into the work elements * Time for each work element

* Rate of performance

* Time of similar work elements should be compared to keep the standard time

constant

* Study a number of cycles instead of one or two

* Extreme values to be discarded

To separate productive & non-productive time

To assess rating of the worker

To identify different types of elements & to

measure their timings

To determine fatigue allowance

To prepare detailed work specifications

To fix Std. time for repetitive elements

Each element should have definite beginning & end

Element should be as short as possible to be conveniently

timed (0.04 min)

Manual & M/c elements should be separately timed

Constant separate from variable

Occasional & foreign to be timed separately

Steps in Work Measurement (Contd.)

Di id th j b i t l t Th di i i f


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Divide the job into elements. The division ofjobs is necessary for the following reasons.

1. Provide better understanding.

2. Break the study into manageable size.

3. Workers efficiency thorough out job.

4. Distinguish between various parts.5. Isolate man and machines.

Time the elements. Stop watch is generally used in thesystem. Either of continuous or Fly-back method is used for

recording time.

Ex: Dividing Drilling into elements1. Selecting the work piece and

placing it in jig.2. Tightening the screw3. Advancing the drill towards

the work piece4. Drilling5. Withdrawing the drill from the

operation6. Loosening the screw7. Removing piece from jig8. Removing the chips

The number ofcycles to be timed. There should besufficient readings to get reasonably accurate results It depends

Steps in Work Measurement (Contd.)


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sufficient readings to get reasonably accurate results. It dependson

1. Variation in times of element.2. Degree of accuracy required.

3. Prescribed level of confidence.

Rating ofoperator.RATING is gauging and comparing the

pace or the performance of a worker against a STD performancelevel set by the TS Engineer.

Objective rating. Here emphasis is laid on speed anddifficulty experienced in performing a job. At first operator is rated

on normal speed and movement. Then other factors are

considered. (based on (i) the amount of body used (ii) foot movement involved (iii) eye-hand coordination(iv) weight moved or lifted (v) handling requirements etc.).

Allowances.

Amount of work that can be produced by a qualified employee when working

t l d ff ti l tili i hi ti h k i t t i t d b

A FAIR DAY'S WORK


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at normal pace and effectively utilizing his time where work is not restricted by

process limitations.

Qualified Worker is one who is accepted as having the necessary physical

attributes, who possesses the required intelligence and education, and has

acquired the necessary skill and knowledge to carry out the work in hand to

satisfactory standards of safety, quantity and quality. (Choose the operator

among many doing the job under study).

It is the rate of output which qualified workers will naturally achieve

without over-exertion as an average over the working day or shift,provided that they know and adhere to the specified method and

provided that they are motivated to apply themselves to their work.STANDARD RATING

Rating is the assessment of the worker's rate of working relative to the

observers' concept of the rate corresponding to standard pace.

STANDARD PERFORMANCE

FACTORS AFFECTING RATE OF WORKING

(outside the control of worker)


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( )

1. Variation in the quality of materials used

2. Changes in the operating efficiency of the equipment

3. Changes in climatic and surrounding conditions of operation.

FACTORS WITHIN THE CONTROL OF WORKER

a. Acceptable variations in the quality of the product

b. Variations due to his ability

c. Variations due to his attitude

Thus, rarely the time taken to perform an element of operation by the operator is

constant from piece to piece of the job. Therefore, enough cycles are to be timed to

get representative time of each element.

No. of Observations required, = (()

Ifaccuracy level required is 10% the co-eff is 20; for5% it is 40; for2.5% it is 80.

Where, N = actual No. ofobservations taken in pilot study.

And x = each observed

elemental time

R ti f t

SCALES OF

RATING

100-133


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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 abovestandard, the operator gets a factor above hundred.

Essential idea being:

Observed time x Rating = Constant

60-80

75-100

0-100

Performance Rating


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(this 100 is Standard rating)

10. Calculating standard time of the job


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Constituents of Standard TimeBasic constituents of Standard Timeare:

Elemental times (Observed

times)

Compensation for the

difference in operatives pace ofperformance and standard

performance.

Relaxation allowance

Interference and Contingency

allowances

Policy allowance

Normal Time

Total

Allowance

Standard

Time

Relaxation

Allowance

Policy

Allowance

Interference

Allowance

Contingency

Allowance

Fatigue

Allowance

Personal

Needs

Allowance

Standard Time


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Normal or Basic Time of elements of the job when

added, gives BASIC TIME of the job. Becausenobody can work continuously some additional time

(given as allowances) is required to be added to

Basic Time to arrive at Standard Time.

Standard Time is calculated by taking the NormalTime and adding allowances for Personal Needs,

Fatigue, Contingency, Interference etc.

= Observed Time

Or


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=

Performance Rating

The expression of ten used in practice for Standard Time is:

= Normal Time ( 1 + )

Some times the allowances are allowed to be applied to the total work

period, then

=

( )

Illustrated Examples

An industrial operation consists of Ele Observe Performan Normal or


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An industrial operation consists of

FIVE elements with following

observed times and the performance

ratings:

Assuming rest and personalallowances as 15% and contingency

allowance as 2% of the basic time,

calculate standard time per piece.

Element Observed

Time (Min.)

Performance

Rating (%)

A 0.20 85

B 0.08 80

C 0.50 90

D 0.12 85

E 0.10 80

me

nt

d Time

(Min.)

ce Rating

(%)

Normal or

Basic Time

(Min)

A 0.20 85

B 0.08 80 0.064

C 0.50 90 0.450

D 0.12 85 0.102

E 0.10 80 0.080

0.866

Standard Time computation of an ordinary manual operation:An operator working on a Pillar Drill performed the following elements for which the

observed times and ratings are given hereunder:


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(i)Calculate normal time of each element and normal time of the job,

(ii) Also calculate standard time of the job.

Element

Code

Element Description Obseved

Time

Rating Relaxation

allowance

A Position job into a drill jig 0.20 80 11%

B Switch on the M/c & lower drill 0.008 100 11%

C Drill hole 2.20 90 13%

D Raise drill and switch off M/c 0.05 80 11%

E Remove job from jig 0.10 110 11%

Element

Code

Element Description Obsd

Time

Rating Relaxa

allowan

Work content/

Std time

A Position job into a drill jig 0.20 80 11% 0.1776

B Switch on the M/c & lower drill 0.008 100 11% 0.0888

C Drill hole 2.20 90 13% 2.2374

D Raise drill and switch off M/c 0.05 80 11% 0.0444

E Remove job from jig 0.10 110 11% 0.1221

Standard Time of the Job 2.6703 min

A cylindrical grinding operation involves elements detailed below along with theirrelated data:

Elemen

t code

Element description Obsrd

time

Rati

ng

Remark Assuming rest & personal allowance as

13% and contingency allowance as 2%,


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A Pickup job &tighten carrier

0.2 90 --

B Position untilbetween centres 0.05 80 --

C Advance wheel tojob

0.03 100 --

D Grindto size 0.78 100 --

E Spark off 0.06 100 --

F Withdraw wheel toclear job

0.05 100 --

G Measure 0.02 85 Once in5 pieces

H Release job frombetween cetres

0.06 80 --

I Loosen carrier &keep the job aside

0.10 90 --

J Dress wheel 0.04 90 Once in20 jobs

3% a d co ge cy a o a ce as %,

calculate standard time of the job.

Solution:

Eleme

nt

Obsd

time

rating Norm

al

time

freq NT/

cycle

Tota

l

Allo

Work

content

/ cycle


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w

A 0.20 90 0.18 1 0.18 15% 0.207

B 0.05 80 0.04 1 0.04 15% 0.046

C 0.03 100 0.03 1 0.03 15% 0.0345

D 0.78 100 0.78 1 0.78 15% 0.897

E 0.06 100 0.06 1 0.06 15% 0.069

F 0.05 100 0.50 1 0.05 15% 0.0575

G 0.20 85 0.17 1/5 0.034 15% 0.0391

H 0.06 80 0.048 1 0.048 15% 0.0552

I 0.10 90 0.09 1 0.09 15% 0.1035

J 0.40 90 0.36 1/20 0.018 15% 0.0207

1.330 1.5295

Standard time computation when Stop Watch

readings are given:


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A time study was conducted on a job consisting of three

elements. The stop watch readings of the first five cycles using

cumulative timing method are given below:

The rating factors were estimated at 80, 100, 110 for the threeelements respectively (on the rating scale of 100 corresponding to

normal performance). The allowance for personal needs, rest etc.

amount to 12%. Calculate the standard time for the job.

ELEME

NT

STOP WATCH READINGS in hundredth of a minute

1 2 3 4 5

A 10 73 139 203 266

B 25 88 155 218 280

C 64 128 193 257 320


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Eleme

nt

Elemental Individual time

(centiminutes)

Ave. time of

elements

(Min)

Rating Normal

(or

Basic)

time

Allowances Work

Content

1 2 3 4 5

A 10 09 11 10 09 0.098 80 0.0784 12% 0.0878

B 15 15 16 15 14 0.150 100 0.1500 12% 0.1680

C 39 40 38 39 40 0.392 110 0.4312 12% 0.4829

0.7387

Uses of time standards


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To provide information on which the planning and

scheduling of production can be based, including theplant 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.

Work /Activity Sampling


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For long cycle operations and for activities where Time Study

is not possible, Work Sampling is applied. Ex. Office work,supervisory work, activities in stores etc.

The second common technique for measuring a job is called

Work Sampling. It involves observing a portion or sample of

work activity and based on the findings of this sample,statements can be made about the activity.

The time it takes to make an observation depends on what is

being observed. Many a times only a glance is needed todetermine the activity and majority of studies require only

several seconds of observation.

Work Sampling

W k S li i t h i i hi h l b f


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Work Sampling is a technique in which a large number of

instantaneous observations are made over a period of time of a

group of machine, processes or people. Work sampling is a

method of finding the percentage occurrence of a certain activity

by statistical sampling and random observations.

Each observation records what is happening at that instant and the

percentage of observations recorded for a particular activity or

delay is a measure of thepercentage of time during which that

activity or delay occurs. (Also known as Activity Sampling, RatioDelay Study,

ObservationRatio Study, SnapReading Method and Random Observation Method)

Work sampling is a method of finding the percentage occurrence of a certainactivity by statistical sampling and random observations.


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Work sampling is the process of making sufficient random observations of anoperators activities to determine the relative amount of time the operatorspends on the various activities associated with the job.

The major goal of work sampling is to determine how long, or how much ofthe work day, is spent on specific types of work.

Work sampling may identify the fact that certain operators spend a largeportion of their time waiting for work, or performing paperwork tasks, or evenperforming activities that are not included in their job descriptions.

One of the basic foundations of statistical sampling theory is the concept thatthe larger the sample size, the results will be more accurate.

In work sampling, a sufficient number of observations must be made to be surethat the results accurately summarize the work performed. There are statisticalformulas to help determine how many observations should be made.

Number of observations in Work Sampling One of the basic foundations of statistical sampling theory is the

concept that the larger the sample size, the results will be more


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p g paccurate.

In work sampling, a sufficient number of observations must be madeto be sure that the results accurately summarize the work performed.There are statistical formulas to help determine how manyobservations should be made.

For 95 % accuracy (confidence level)

Sp = 2 { p (1p) / N }

Sp is significance level, p is extent of the phenomenon (problem) being

observed in a pilot studyexpressed as decimals, and N is totalnumber of observations.

N is then divided into number of machines, days, operators, etc.

A few words about sampling


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Sampling is mainly based on probability. Probability has been defined asthe degree to which an event is likely to occur.

A simple and often-mentioned example that illustrates the point is that oftossing a coin.

The law of probability says that we are likely to have 50 heads and 50 tailsin every 100 tosses of the coin. The greater the number of tosses, the morechance we have of arriving at a ratio of 50 heads to 50 tails.

The size of the sample is therefore important, and we can express ourconfidence in whether or not the sample is representative by using a certainconfidence level.

Establishing confidence levels

Let us go back to our previous example and toss five coins at a time, andthen record the number of times we have heads and the number of times wehave tails for each toss of these five coins. Let us then repeat this operation100 times.

Using Work Sampling


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Make tours of observations on representative of normal

working days

Tours should be carried out in random intervals, random

numbers could be generated to decide on the order

Familiarity of the observer with the process is not critical,

though beneficial.

CONDUCTING A STUDY


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It is recommended that a uniform procedure should be

followed to perform a work sampling study is to

1. Establish the Purpose

First, the objective of the study should be established. Worksampling can be used to determine an overall perspective onthe work done.

2. Identify the Subjects

Second, the people performing the task must be identified, i.e.general office work is being studied with the objective of determining overall productivity.

3. Identify the Measure of Output


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The third step in making the study is the identification of the

measure of the output produced or the types of activities performedon the jobs being studied. This step is especially important if theobjective of the study is to measure productivity with the intent of

setting a standard.

4. Establish a Time Period

Fourth, the time period during which the study will be conductedmust be established. Starting and stopping points for the study must

be defined as well.

5. Define the Activities

This step involves defining the activities that are performed by thepeople under study. For example, the definition used in a machineutilization study, including only the categories of working, idle, and

idle-mechanical breakdown.

6. Determine the Number of Observations Needed


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After the work elements are defined, the number of observations for

the desired accuracy at the desired confidence level must bedetermined. If a reasonable guess cannot be made, then a trial studyof perhaps 20 to 40 observations should be made to get an estimate.

7. Schedule the Observations

Once the number of required observations has been determined,either from appropriate statistical calculations or from tables, and theactual observations must be scheduled. Typically, the analyst willassign an equal number of observations each day during the course ofthe study. For example, if 800 observations are required and 20 workdays are established as an appropriate observation time, 40

observations should be recorded each day. A random number table can be used to establish the random times foreach observation.

8. Inform the Personnel Involved


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Before the study is actually performed, the personnelinvolved should be informed about the objective of the studyand the methodology that will be employed.

9. Record the Raw Data

The next is the actual recording of the raw data. Althoughthis recording can be performed by anyone, it is desirablethat a trained analyst be employed.

It is also very important that the observations be made atexactly the same location every time.

10. Summarize the Data After the data have been collected, they must be

summarized.


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To make things easier, it is more convenient to speak of a 95 per cent confidence level than of a95.45 per cent confidence level.

To achieve this we can change our calculations and obtain: 95 per cent confidence level or 95 per cent of the area under the curve = 1.96 p

99 per cent confidence level or 99 per cent of the area under the curve = 2.58 p

99.9 per cent confidence level or 99.9 per cent of the area under the curve = 3.3 p

In this case we can say that if we take a large sample at random we can be confident that in 95per cent of the cases our observations will fall within 1.96 p

Number of Samples


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Number of Samples

Confidence interval

Probability that true

proportion will fall

within confidence interval

p- e p+ ep

e= zp(1 - p)

n

Number of Samples


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Number of Samples

n= p(1 - p) z 2

e

DesiredConfidence (%) z

90 1.65

95 1.96

96 2.05

97 2.1798 2.33

99 2.58

n = required sample size

p = estimate of proportion time an activity takes place

z = number of standard deviations for desired confidence

e = maximum error allowable

Determination of sample size

As well as defining the confidence level for our observations we have to decide onthe margin of error that we can allow for these observations.


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Let us look at our example about the productive time and the idle time of the

machines in a factory. There are two methods of determining the sample size thatwould be appropriate for this example:

the statistical method and the nomogram method.

Statistical method. The formula used in this method is:

Let us assume that some 100 observations were carried out as a preliminarystudy and at random, and that these showed the machine to be idle in 25 percent of the cases (p = 25) and to be working 75 per cent of the time (q = 75).


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We thus have approximate values for p and q; in order now to determine thevalue of n.

Let us choose a confidence level of 95 per cent with a 10 per cent margin of error (that is, we are confident that in 95 per cent of the cases our estimateswill be 10 per cent of the real value).

E = z p Since E= 10

And Z = 1.96


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Nomogram methodAn easier way to

determine sample size is to

read off

the number of observations

needed directlyfrom a nomogram

such as the one reproduced

in figure 91.

Making random observations

To ensure that our observations are in fact made at random, we can use a


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To ensure that our observations are in fact made at random, we can use arandom table such as the one in table 12.

Various types of random table exist, and these can be used in different ways. Inour case let us assume that we shall carry out our observations during a dayshift of eight hours, from 7 a.m. to 3 p.m. An eight-hour day has 480 minutes.These may be divided into 48 ten-minute periods.

We can start by choosing any number at random from our table, for example

by closing our eyes and placing a pencil point somewhere on the table. Let usassume that in this case we pick, by simple chance, the number 11 which is inthe second block, fourth column, fourth row (table 12).

We now choose any number between 1 and 10. Assume that we choose thenumber 2; we now go down the column picking out every second reading andnoting it down, as shown below (if we had chosen the number 3, we should pick

out every third figure, and so on).

11 38 45 87 68 20 11 26 49 05


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Looking at these numbers, we find that we have to discard 87, 68 and 49 because theyare too high (since we have only 48 ten-minute periods, any number above 48 has to bediscarded).

Similarly, the second 11 will also have to be discarded since it is a number that hasalready been picked out. We therefore have to continue with our readings to replace thef i i i i


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four numbers we have discarded. Using the same method, that is choosing every secondnumber after the last one (05), we now have 14 15 47 22

These four numbers are within the desired range and have not appeared before. Ourfinal selection may now be arranged numerically and the times of observationthroughout the eight-hour day worked out. Thus our smallest number (05) representsthe fifth ten-minute period after the work began at 7 a.m. Thus our first observation willbe at 7.50 a.m., and so on (table 13).

Example: Conducting the study

Determining the scope of the study. Before making our actual observations, it is

important that we decide on the objective of our work sampling.

Th i l t bj ti i th t f d t i i h th i hi i idl


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The simplest objective is that of determining whether a given machine is idle or

working. In

work study slides im eee chem 13

Documents

work contentdue

excess work contenta

basic time

actual time

orprocesswork content

loss of working time

lack of standardisation

lack of quality mindedness