unit2 work study

8/3/2019 Unit2 Work Study

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Work study

2.0 Definitions:

Work study is the generic term for the techniques of Method study (motion study)

and work measurement (Time study) which are used for finding out the best andmost efficient way of using available resources namely men, Material andMachines.Motion study: Work simplification Developed by Frank Gilbreth &

Lillian Gilbreth.Time study : Work measurement Developed by F W Taylor.

2.1 Applications:1. Production operations, R & D 6. Buildings, Roads and other

Constructional activities2. Marketing, Sales and distribution 7. Transport

3. Stores, ware house and offices 8. Hospitals4. Material Handling 9. Army5. Design 10. Agriculture

2.2 Advantages of Work study:1. Uniform and improved production flow 6. Better service to customers2. Higher Productive Efficiency 7. Job satisfaction to employees3. Reduced Manufacturing Cost 8. Improved working conditions4. Fast and prompt Delivery 9. Higher wages to workers5. Good Industrial Relations

2.3 Contributions of F W Taylor:

1. Developed Time study and established work standards2. Developed the concepts of Scientific Management3. Introduced the concepts of Fair days task considering the fatigue of workers4. Developed the Functional organization where the importance of Specialists in

various fields is highlighted5. Suggested a Wage incentive scheme known as Taylors Differential Piece

Rate Plan2.4 Contributions of Frank Gilbreth:

1. Developed the concepts of Motion study2. Evolved the Principles of Motion Economy3. Introduced the use of Process Charts4. Identified the Fundamental motions involved in doing an activity Known as

THERBLIGS5. Developed Micro-motion study and SIMO chart, Microcrhronometer,

Cyclegraph, chronocyclegraph and flow diagrams.6. Carried out studies on fatigue and its elimination by lighting the load, spacing

the work and introducing rest periods.


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2.5 Motion Study:2.5.1 Definition:

Motion study: It is the science of eliminating wastefulness resulting fromill directed and inefficient motions.

Method study: It is a systematic investigation of the existing method of doing a job (process) and developing an easy, rapid,efficient, effective and less fatiguing procedure for doingthe job at lower cost.

The scope of motion study is enlarged to form the method study.

2.5.2 Objectives of Method study:1. Elimination of wastage of time and labor 2. Least fatigue to workmen3. To find the best way of doing a job4. Better lay out, neat and clean environment and working conditions

5. Effective utilization of resources6. Better quality of products7. Efficient material handling8. Reduced health hazards and safe working conditions9. Stream lined working procedures

2.5.3 Procedure of method study:Steps:1. Select the work for study and define objectives2. Record all the relevant information pertaining to the existing method.

Break up the operations of the job.Use(a) Process charts (c) Motion & Film analysis(b) Diagrams (d) Models

3. Critical examination -Question each details of the job. The basic questionsare on the following points.1. Purpose 4. Sequence2. Place 5. Means3. Persons

4. Develop the best method1. Practical & Feasible 2. Economical2. Safe & Effective 3. Acceptable to other departments

Design, Prod. Control, QC, sales5. Install the best method so devised

Stages: 1. Planning 3. Implementing2. Arranging

6. Maintain the new method1. Periodic checks & Verification2. Views of workmen, supervisors and other persons may be obtained.


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2.5.4 Flow process charts:

A chart representing the sequence of operations of a process is called the Flow process chart.

2.5.5 Symbols used in process chart:

1. Operation : 5. Inspection :6. Operation cum

Transport :

7. Inspection cum2. Storage: operation :

or Temp. Storage :8. Change point :

cum operation :3. Delay :

4. Transport :

2.5.6 Types of flow process charts:

1. Outline process chart: Gives over all picture of the process giving mainevents sequence wise.

2. Flow process chart3. Two handed process chart4. Multiple activity charts

Flow process chart: A detailed version of outline process chart.

1. Sets out sequence of low2. Records all he events in sequence using symbols3. Marks distances traveled and time taken by an event

Types:1. Man type : Records activities of an operator 2. Equipment type: Records the usage of equipment3. Material type : Records the changes in material in location or

condition


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S.No. Activity Operations Distancemovedmeters

TimeinMinutes

Remarks

1

2

3

4

5

6

7

----

Casting in foundry

Moved to gascutting m/c

Wait- setting m/c

Raisers cut

Wait for trolley

Moved to m/c

shop

Inspection beforemachining

10

20

3

5

20

10

6

15

By trolley

By trolley

Material type Flow process chart

Bring specimen from Metallurgical 10 m

LabStart polishing

Sprinkle the etching solutionHold the specimen in handLoad the specimen on polishingMachineWait for a few secondsTake the specimen to wash 2 mBasinWash the specimen

Etch the specimenWash againDry the specimen

Check under microscope

Keep the specimen in container Flow process chart (Man type)


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Left hand Symbols Right hand

LH RHPick up bolt

Hold

Hold

Hold

Idle

Pickup nut

To left hand

Assemble ( Screw up)

Two hand process Chart

Multiple activity charts:

It records the simultaneously the activities of all the workers in a team or theactivities of a worker and the machines he handles on a common time scale showing their inter relations.

OperatorsActivities

Time Operator

Machine 1 Machine 2 Remarks

StartingSetting M/c. 1Setting M/c. 2Idle

Setting M/c. 2Idle

Setting M/c. 1Idle

0510

2530

4045

5060

Multi activity chart


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2.5.7 Flow diagrams:Def: A flow diagram is a drawing or diagram which is drawn to scale showingthe relative positions of Prodn. Machinery, Jigs &fixtures, gang way etc. andmarks the path followed by men and materials.Steps:

1. Draw to scale the plan of work area.2. Mark up the positions of m/cs. , benches, stores, racks, inspection booths etc.

3. Observe the operations and draw the path of the materials and men onthe drawing showing the directions of movements.

4. Use different colours for different movements. Use symbols.

Flow diagram2.5.8 String Diagram:

A string diagram is preferred to flow diagram when the movements are very muchcongested and difficult to trace.

It is a lay out drawing on which a length of a string is used to record the extent aswell as the pattern of movements of workers and materials.

String Diagram

2

1

1

1 5

M4

M1M2

M3

Inspection

Stock room

storesStrin


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2.5.9 Operation analysis:

Operation analysis is a detailed study of different operations involved in doing a job.

1. Possible ways of improving a process:

1. Eliminations of some undue operations2. Combining one or more operations.3. Change of sequence of operations.

2. Questionnaire for effective solutions: Areas of questions:

1. Worker 5. Operations2. Material 6. Tools and fixtures3. Material handling 7. Working conditions

4. Machine set up

2.5.9.1 Motion analysis:

Analysis of an operation when carried out in terms of individual motionsof a worker is known as motion analysis.

1. Steps for carrying out operation analysis:

1. Select the operation to be studied2. List and chart various motions performed by operator 3. Identify the productive and idle motions4. Eliminate unnecessary and non-productive motions5. Redesign the existing procedure6. Impart necessary instructions to workers7. Verify the procedure for improvement and usefulness8. standardize the procedure


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2.5.10 THERBLIGS:Frank Gilbreth developed a set of elementary motions commonly found in manualoperations and called them THERBLIGS (spelled his name in reverse).Different motions of limbs are divided into fundamental events. Each element isallotted a symbol, a letter abbreviation and a color.

S.No THERBLIGS Abbr eviation

Sym bol

Color S.No THERBLIGS Abbr eviation

Sym bol

Color

1 Search SH Black 10 Assemble A Violet2 Hold H Gold

ochre11 Disassemble DA Light

violet3 Select SE Light

grey12 Use U Purple

4 Grasp G Red 13 Inspect I Burntochre

5 Release load RL Carmine red 14 Avoidabledelay DA Lemonyellow6 Transport

loadedTL Green 15 Unavoidable

delayDA Yellow

7 Transportempty

TE Olivegreen

16 Rest R Orange

8 Position P Blue 17 Plan PN Brown9 Preposition PP Pale

blue18 Find F Grey

2.5.11 SIMULTANEOUS MOTION CYCLE (S I M O) CHART:

Def: A SIMO chart is an extremely detailed left and right hand operation chart.1. It shows on a common time scale the simultaneous minute motions

(THRBLIGS) performed by the two hands.2. SIMO charts record the duration of micro motions.3. The time scale is in Winks. ( 1 Wink = 1/2000 min. )

SIMO chartOperation: Date:

Name : Film No. :Component name: Operation No. :

Method:LH Description Symbol Time in

WinksSymbol RH Description

Grasp chistleTo jobPositionHold

GTLPH

0 102030 - 4050

GTLADU

Grasp hammer To jobIdleUse


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2.5.12 PRINCIPLES OF MOTION ECONOMY

PRINCIPLES CONCERNING HUMAN BODY1. Both Hands for Productive Work.

2. Both hands to Start & Finish at the same time.3. Both hands should not be idle at the same time.4. Simultaneous, Symmetrical & Opposite motions.5. Motions to be Simple & Involve min. Limbs.6. Momentum can assist self ; Not to be overcome by Muscular effort.7. Motions should be Smooth & Continuous.8. Ballistic movements to be preferred.9. Mechanical Aids to be used.

10. Work movements to be Rhythmic & Automatic if possible.

PRINCIPLES CONCERNING WORK PLACE LAYOUT

1. Fixed & easily accessible Location for Tools & materials.2. Matls., tools etc. should be close to the work place.3. Use of chute/conveyor/gravity is preferred.4. Tools & Matls. To be placed in their sequence of use.5. Good illumination.6. Proper proportions of heights of chair & table.7. Seating to be Adjustable & comfortable.

PRINCIPLES CONCERNING TOOLS & EQUIPMENT DESIGN

1. Use of Jigs & Fixtures.2. Tools must be of multi-purpose.3. Max. surface contact while handling.4. Equal distribution of load for all the Fingers.

PRINCIPLES CONCERNING TIME COSERVATION

1. Ceasing of Work to be discouraged.2. Machines should not be run idle.3. Two or more Operations to be carried out simultaneously.4. Min. No. of Motions for a job.


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2.5.13 Work place layout:

Comfortable work place keeps the workers more satisfied resulting in more productivity.

1. Ergonomics:

It is the science which considers all the factors regarding the work placeenvironment including the knowledge of anatomy, physiology, psychology etc.

2. Design considerations:

1. Location of tools and materials 5. Proper chairs2. Cleanliness 6. Work bench3. Proper illumination 7. Use of gravity4. Noise 8. Proper machine elements

1. Actual working area 2. Normal working area 3. Max. Working area

Typical work place layout


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2.6 Time Study Def.:Time study (Work measurement) is defined as the application of different techniques

to measure & establish the time required to complete a job by a qualified worker, at a

defined level of performance. OBJECTIVES:1. To determine the time required to do a job.2. To compare & develop alternate methods.3. Estimation of man power requirement.4. Requirement of equipments.5. Effective Prodn. Planning & maintenance.6. Estimation of delivery dates.7. Basis for sound and fair incentive schemes.8. Effective labor control.

STANDARD TIME:

It is the amount of time required to complete a unit of work a) under existing working conditions, b) using specified machinery & method,c) by an operator able to work in proper manner , d) at a standard pace.

2.6.1 Stop watch procedure for collecting time study data:Steps involved:1. Identify the operations to be studied2. Obtain the improved procedure from method study department3. Collect the necessary equipments and ensure their accuracy

Stop watch, Time study record sheets, time study board etc.4. Select the worker to be observed5. Take the worker and supervisor into confidence and explain them the

objectives of the study6. Break the operations into small elements and write them in the proper form7. Separate the constant time elements from variable time elements ( machine

and manual elements)8. Conduct the observations and record them on the time study sheet9. Rate the performance of the worker during observing the timings10. Repeat the steps 8 and 9 for taking more observations11. Compute the average time from the observations12. Calculate the Normal time from the observed time using Performance rating

factor 13. Obtain the standard time by adding process allowance, rest and personal

allowance and special allowances to normal time. Policy allowances are inaddition to the standard time.

Normal time = Observed time x Performance rating factorStandard time = Normal time + Process allowances + Rest & personal

Allowances + Special allowancesTypes of stop watches: 1. Non-fly back 2. Fly back 3. Split hand


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2.6.2 Standard data:Standard data is a catalogue of normal time values for different elements of ajob1. Standard data (Macro data)2. Universal standard data (Microdata)

2.6.3 Time measuring techniques:

1. Stop watch method 2. Analytical estimating 3. Synthesis4. PMTS ( Pre determined motion time standards)

2.6.4 Performance rating:Definition:Performance rating is gauging and comparing the performance of a worker against astandard performance level set by the time study engineer.PERFORMANCE RATING FACTOR:

It is a factor by which the observed Time is multiplied in order to adjust for differences in operators performance.

Normal Time = Observed time x (performance level of worker /

Std. performance level expected)TYPES OF RATING:1. Speed rating.

NT = OT x (workers speed / Std. speed expected)2. Skill & effort rating.

This is suggested by Mr. C.E. Bedaux.Unit of Work is expressed in Bs60 Bs in an hour is standardB- Points = OT x (B- points earned x Relaxation factor) / 60R.F varies from 1 to 3 depending on the severity of the job

3. Westing House system.1. SKILL 2. EFFORT 3.CONDITION 4. CONSISTANCY

1. Super - 0.15 2. excellent - 0.11 3. Good - 0.084. Average 0 5. Fair - -0.05 6. Poor - -0.16

4. Synthetic Rating.Rating factor = Time value extracted from Predetermined Motion Time Study /

Observed time5. Objective rating.Job difficulty depending on1. Body used 2. Foot movement involved 3. Eye hand coordination4. Weight lifted 5. Handling RequirementsFirst rating the worker against the standard speed and then gives the allowance as

per the difficulty in the job.6. Physiological evaluation of Performance level.

Evaluated by1. Heart beating2. Oxygen consumption


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2.6.5 Allowances:1. Process allowance2. Personal and rest allowances

1. Personal 7. Noise2. Fatigue 8. Special protective dress

3. Abnormal posture 9. heat4. Visual concentration 10. Tediousness5. bad light 11. Mental strain6. Atmospheric conditions

3. Special allowances1. periodic activity2. interference

4. Policy allowances

2.7 Work sampling:Def:

It is a technique in which a large number of observations are made over a periodof time of one or group of machines, processes or workers.It is also known as activity sampling or ratio delay study.

1. Relies upon statistical theory of sampling and probability theory.2. Based on normal frequency distribution and confidence level.3. Each observation records the event happening at that instant and the

percentage of observations recorded for that event or delay.2.7.1 Procedure:

1. Determine the main objectives and define each activity to be measured2. Make sure all the concerned with the study understand the objectives3. State the desired accuracy limits for the results4. Conduct pilot study to

1. Estimate the approx. % occurrence of an activity(p)2. Estimate the required No. of observations for the desired accuracy set.3. Ensure the workers habituated to the visits of observation

5. Design the actual studyRequired no. of observations N= 4.p(100-p)/LXL

P= % occurrence L= % limit of accuracy

Normal distribution curve


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unit2 work study

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