3.III Work Measurement

Work Measurement

Session 3. iii

3.iii.A Work Measurement-Setting Time Standards

Time study :

Time Study is defined as a work measurement technique for recording the times and rates of working for the elements of a specified job carried out under specified conditions, and for analyzing the data so as to obtain the time necessary for carrying out the job at a defined level of performance.

Time Study Equipment :

Equipment used on site for time study

i. Stop Watch

ii. Study Board

iii. Time study Forms

Supplementary Equipment:

i. Calculator.

ii. Reliable clock with a seconds hand.

iii. Measuring instruments such as tape, steel rule, micrometer, spring balance and tachometer and or others as needed.

Setting Time Standards

Time Standard Forms : Time Study forms stationery is generally printed, photocopied to record observations on site and one kept on time study board

Introductory Sheet :Records information pertaining to studyRecords decomposed elements of operation.Format Layout is shown in slide

Continuation Sheet: Continuation sheets for subsequent cycles of study.


Short Cycle Study Form

Study Analysis Sheet : Study analysis sheet is used for recording results obtained through study.

Basic time for any elements are calculated from this sheet

Relaxation Allowance Sheet : Relaxation allowance sheet is used to compile relaxation allowances.


Time Study : Rating

Most time studies in industry are used to determine standard times for setting workloads and as a basis for incentive plans.

Various methods of assessing the rate of working, each of which has its good and bad points, have been developed.


The Qualified Worker :

It has already been said that time studies should be made, as far as possible, on a number of qualified workers; and that very fast or very slow workers should be avoided, at least while making the first few studies of an operation.

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


• The acquisition of skill is a complicated process. It has been observed that among the attributes which differentiate the experienced worker from the inexperienced are the following. The experienced worker.

• Achieves smooth and consistent movement:• Acquires rhythm :• Responds more rapidly to signals• Anticipates difficulties and is more ready to

overcome them:• Carries out the task without giving the appearance

of conscious attention, and is therefore more relaxed.


The Average Worker :• Rating is the assessment of the workers rate of

working relative to the observers concept of the rate corresponding to standard pace.

• Rating is a comparison of the rate of working observed by the work study man with a picture of some standard level which is holding in his mind.

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


Factors affecting The Rate of Working :

• Variations in actual times for a particular element may be due to factors outside or within the control of the worker. Those outside his control may be.

• Variations in the quality or other characteristics of the material used, although they may be within the prescribed tolerance limits.

• Changes in the operating efficiency of tools or equipment within their useful life.

• Minor and unavoidable changes in methods or conditions of operation.


• Variations in the mental attention necessary for the performance of certain of the elements.

• Changes in climate and other surrounding condition such as lights, temperature etc.

• These can generally be accounted for by taking a sufficient number of studies to ensure that a representative samples times is obtained.

• Factors within his control may be.• Acceptable variations in the quality of the product.• Variations due to his ability.• Variations due to his attitude of mind, especially his

attitude to the organization for which he works.


• The factors within the workers control can effect the times similarly described elements of work by affecting.

• The pattern of his movements, his working pace - both, in varying proportions.

• Study man must therefore have a clear idea of the pattern of movement which a qualified worker should follow.

• The optimum pace at which the worker will work depends on.

• The physical effort demanded by the work.• The care required on the part of the worker• His training and experience


• Greater physical effort will tend to slow up the ace.• The ease with which the effort is made will also

influence the pace• Care must be taken to distinguish between slowing

up due to effort and slowing up due to fatigue.• The studyman should be careful not to rate too

highly when– The worker is worried or looks hurried– The worker is obviously being over-careful– The job looks difficult to the studyman– The studyman himself is worrying very fast, as

when recording a short element study.


• Conversely, there is a danger of rating too low when– The worker makes the job look easy– The worker is using smooth, rhythmic

movements.– The worker does not pause to think when the

studyman expects him to do so.– The worker is performing heavy manual work.– The studyman himself is tried.


Scale of Rating :

• In order that a comparison between the observed rate of working and the standard rate may be made effectively, it is necessary to have a numerical scale against which to make the assessment.

• There are several scales of rating in use, the most common of which are those designated the 100 – 133 scale, the 60-80, the 75-100, and the British Standard Scale used in this book (essentially a restatement of the 75-100 scale) which is the 0-100 scale.


How The Rating Factor is Used :

• The figure 100 represents standard performance.• If the study man decides that the operation he is

observating is being performed with less effective speed than his concept of standard, he will use a factor of less than 100, say 90 or75 or whatever he considers represents a proper assessment.

• If, on the other hand, he decides that the effective rate of working is above standard he gives it a factor greater than 100 – say, 110,115 or 120.


• It is usual practice to round off rating to the nearest multiple of five on the scale : that is to say, would be able to rate nor closely than the nearest ten.

• If the study man's rating were always impeccable, then however many times he rates and times an element the result should be that.

• The next is to convert each observed time to a basic time entering the result in the column headed “BT” on the time study sheets.


Basic Time is the time for carrying out an element of work at standard rating i.e.,

Observed Time x Observed Rating

Standard Rating

Extension is the calculation of basic time for observed time

-------------------------------------------------------------------------------------

The effect of extending an observed time for an element to the basic time is shown graphically in figure below

Effect of extension on the time of an element :

(a) Performance above standard

Observed time OT x (R-100) / 100

------------------------------------------------------------------------------------------------------------------

Basic Time

---------------------------------------------------------------------------------------------------------------

(b) Performance below standard

Observed Time

----------------------------------------------------------------------------------------------------------------

OT x (R – 100) / 100

Basic Time


The Selected Time :• The selected time is the time choose as being

representative of a group of times for an element or group of elements.

• These times may be either observed or basic and should be noted as selected observed or selected basic times.

Constant Elements :• There are various methods of examining and

selecting the representative basic time for a constant element.

• Perhaps the most common and in many ways often the most satisfactory.


Variable Elements :• The analysis of variable elements present more

difficulty.• It is necessary to find out what it is that causes

the basis time to very, and quite often there may be several variables to take into account at once.

• Time may have to be allowed for cleaning machines and the workplace and for changing clothes in industries where special clothing is required.

• Activities of this sort are not usually taken into account in the calculation of standard times for individual jobs but are more often dealt with by time allowances.


Allowances :

• Even when the most practical, economic and effective method has been developed, however, the job will still require the expenditure of human effort, and some allowance must therefore be made for recovery from fatigue and for realization.

• Allowances must also be made to enable a worker to attend to his personal needs and other allowances (e.g. contingency allowances) may also have to be added to the basic time in order to give the work content.


• The most important allowances are :1) Factors related to the individual2) Factors related to the nature of the work itself3) Factors related to the environment

• Calculation of Allowances :– The basic model for the calculation of

allowances is shown in figure.– It will be seen from this model that relaxation

allowances (which are intended to aid recovery from fatigue) are the only essential art of the time added to the basic time.

– Other allowances, such as conditions, policy and special allowances, are applied under certain conditions only.


Allowances


Personal needs Fixed Allowance

Basic fatigue Relaxation allowance

Total allowance

Stress and Strain Variable allowances

Contingency allowances

Basic time

Environmental

Policy allowances

Work content

Special allowances

• Relaxation Allowances :

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

– The amount of allowances will depend on the nature of the job.


• Relaxation allowances have two major components : – Fixed allowances– Variable allowances

• Fixed allowances are composed of :i. Allowances for personal needs.

a. This allowances provides for the necessity to leave the workplace to attend to personal needs such as washing, going to the lavatory and getting a drink.

b. Common applied by many enterprises range from 5 to 7 percent.


i. Allowances for basic fatigue.a. This allowance, always is constant, is given

to take account of the energy expended while carrying out work and to alleviate monotony.

b. A common figure is 4% of basic time.c. This is considered to be adequate for a

worker who carries out the job while seated, who is engaged on light work in good working conditions, and who is called upon to make only normal use of hands, legs and senses.

• Variable allowances are added to fixed allowances when working conditions differ.


Rest Pauses:• Rest pauses are important for the following

reasons:– They decrease the variation in the worker’s

performance throughout the day and tend to maintain the level nearer the optimum.

– They break up the monotony of the day.

– They give workers the chance to recover from fatigue and to attend to personal needs.

– They reduce the amount of time off taken by workers during working hours.


• Other Allowances :– It is sometimes necessary to incorporate

allowances other than relaxation allowances in the compilation of standard time.

– Such allowances are:i. Contingency allowances.ii. Policy allowances.iii. Special allowances.


• The Standard time :

It is now possible to obtain a complete picture of the standard time for a straight forward manual job or operation, one which is considered t attract only the two allowances which have so far been discussed in detail :

a.Contingency allowance and

b.Relaxation allowance


The standard time for the job will be the sum of the standard time for all the elements of which it is made up, due regard being paid to the frequencies with which the elements recur, plus the contingency allowance (with its relaxation allowance increment).


Standard time is the total time in which a job should be completed at standard

performance.

Graphical Representation of Standard Time

for a simple manual job is made up.


Observed time Rating Factor Relaxation allowance

Cont. all.

If performed at a paceGreater than standard pace.

Basic Time

Work content

STANDARD TIME

Problems of Time Study and Fixing of Time Standards:

Time – Study always be done on the mutual understanding of the employer and employee.

For carrying out time-study in any industry the following conditions are necessary :

a) The management must tell the objectives of such study.

b) The supervisory staff and the workmen should be taken in confidence.

c) Correct measurements should be recorded.


a) Standard time should be rigid, should not be subjected for any change under pressure except when the method is changed.

b) If the worker wants to see time-study sheet, it must be open for examination and comment.

• The workers always look with suspicion on time-study because they feel that they are being forced to produce more.

• Hence it is necessary that the workers must have faith and confidence on time-study process and the time-study man.


• Basic – Time and Normal – Time :– Any job is consisting of many work-elements

and each work-element has been timed for a number of times to suit a particular level of confidence.

– The machining elements are separated from manual elements.

– Manual elements are necessarily timed, and one can avoid the timing of machining elements.

– Representatives time for each manual element is the average of the recorded data, which is entered in the analysis sheet will pencil


Time – Study Sheet

(Analysis)

---------------------------------------------------------------------------------------------------------

Department----------------------------- Study No. -------------------------------------------

Operation ------------------------------- Sheet No. --------------------------------------------

Machine No. ---------------------------- Time on. ---------------------------------------------

Product No. ----------------------------- Time off ---------------------------------------------

Material ----------------------------------- Elapsed Time -------------------------------------

Drawing No. ---------------------------- Operator -------------------------------------------

Clock No. -------------------------------------------

Date --------------------------------------- Studied by -----------------------------------------

---------------------------------------------------------------------------------------------------------

Contd…


R = Rating factor W.R = Watch readingS.T. = Subtracted time N.T = Normal or basic time


Description of work element

R. W.R S.T. N.T. Description of Work Element

R. W.R. S.T. N.T.

• After completing the time study sheet, the subtracted time (S.T) for each element is referred as `Observed-time’.

• Representative or

Observed – Time (T) = t1 + t2 + t3 + …….tn

---------------------------- n i = n T = t/n I = 1

where t is the time for the same element in minute, and n is the number of observations considered.


• To convert representative- time into `Normal-Time’• Normal Time = Representative time x Rating Factor

N.T. = T x R• Normal – time is computed for constant and variable

man controlled elements.• Production process is a combination of man controlled

elements and machine controlled elements.Observed Rating Constant Relaxation factor allowances allowances

Work delaysBasic timeWork ContentStandard time


STANDARD TIMEStandard time = Observed time x Rating factor + Allowances.This gives a complete picture of the standard time for a manual job or

operation, standard time is the total time in which a job should be completed at standard performance.

----------------Observed – time --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------Normal – time ----------------------------------------------------------------------------- Rating factor-------------------------------------------------------------------------------------------------------- Other

Relaxation allowances allowances Unavoidable delays---------------------Standard – time

------------------------------------------------------------- (When R < 100)


Setting Time-Standards For Machine – Work:• Consider a situation, where the job is to be

accomplished on machinery, and very often machining costs are much greater than the total wage bill of the plant, so it is important that the installed machinery and equipments must be extensively used.

• This is done even at the cost of labor productivity and there is nothing wrong in adopting such policy, work-study man can decide whether labor productivity or machine utilization is of primary importance.

• The most useful technique for studies on machine-utilization is activity-sampling particularly when many machines are involved.


---------------------------------------------------------------------------------------Machine maximum time

-------------------------------------------------------------------------------------- Machine – available time Not worked

-------------------------------------------------------------------------------------- Working day per week Over time

--------------------------------------------------------------------------------------


Machine running time

m/c m/c m/c

Idle Ancillary Down

Time Time time

Machine running time of standard Low performance

1) Machine utilization index = machine running time

-----------------------------

machine available time

2) Machine efficiency index =

Machine running time at standard

-----------------------------------------------

machine running time

3) Machine effective utilisation index =

Machine running time at standard

----------------------------------------------

Machine available time


Summary of Time Study Process :

1. Once the method study has been set, a time study is to be done on new methods to evaluate it.

2. First a preliminary study is undertaken to eliminate any existing defect in the system and to make the time study man thoroughly familiar with the new method.

3. In big and small batch production, this study is done generally together with the method study in save time and money.


4. Next the detailed time study is made together with an assessment of the operator efficiency. One or more studies may be made depending on the importance of the job or the cost of operation.

5. The main object of time study is to fix the standard time as a basis for wage payment and a measure of the efficiency of the organization.

6. The standard time is the only method of establishing norm of productivity, the achievement of which is one of the sure ways for an organization to retain its competitive position in the market.


Uses of Time Standards

After completing the Method-Study, it is very important to detail out from the record:

1. The details of the method being followed.2. The details of the tools and equipments being

used3. The details of every feature of the operations

being followed along with the time of operation.


A. Important points in technical set-up and work specification by Time Standard:

1. Details of the work-piece or product, on which the method improvement has been done.

2. Details of the machine or plant on which the specific operation is scheduled to be carried out including the speeds, feeds, various toolings and work-place layout.

3. Details of quality standards desired to obtain on this product including finish, tolerances, gauging requirement and other inspection method.


4. Details of all the work-involved including repetitive elements, variable elements; setting up and break down; cleaning, greasing etc necessary on the machines.

5. Details of all the work-involved including repetitive elements, variable elements; setting up and break down; cleaning, greasing etc necessary on the machines.

6. Details of the conditions under which time-standards have been set and issued with any special purpose.


B. Standard – time defines the standard unit of work.

It indicates so many minutes per piece or so many pieces per hour. Each time unit has a component of allowances also.

C. Standard – time used in production planning and control Plant-utilization Labor utilization.


Production program can be prepared, if the following information's are

available.1. Product to be made and its quantity required. (Sales

and forecasting department must indicate this information)

2. Operations necessary to carryout the work particularly specifying plant, equipment, tools needed and type of labour required. (process planning and Method Study must provide this information)

3. Time needed for each operation. (Work – measurement should indicate this information)

(Plant engineer should give this information in machine-hrs available)


4. Plant capacity available (Plant engineering should give this information in machine hers available) and labour available (labour office should provide this information in man hours available).

D. Standard time is useful for estimation of production cost in terms of time (minutes) of production calculated each week. Work measurement provides actual performance.

E. Standard time is used for incentive-scheme for different catagories of labour. Incentive schemes based on work measurement are sound and the labour would have faith on it.

F. Standard – time provides better control.


Work Sampling

3. iii. C.

Work Sampling

• Work Sampling• Activity sampling• Ratio delay Study• Developed by L.H.C. Tippet

Britich Cotton Industry Research Association in 1934

• A technique which enables information about an activity, machine, process by making random observations of the worker without the use of a stopwatch• Observation are made over an extended time to take care of variations

Work sampling is a method of finding the percentage occurrence of a certain

activity by statistical sampling and random

observation

Work Sampling

• A method of work measurement• Large number of instantaneous observations are

made, at random intervals; over a specified period of time, of a group of workers, machines or process

• Each observation records the state of observations of an activity / delay

• Estimate the percentage of time the activity or delay occurs

• Work sampling is based on the law of probability (Ex:- Tossing a coin)

Principles

• If we toss a coin the probability is a head or tail (50:50)

• If we toss 10 times there can be

55 Heads 45 Tails

48 Heads 52 Tails• The more number of tosses, the more accurate is

the answer.• The normal distribution curve• If we plot the occurrences of a number of

probabilities of combinations we get a smooth curve as shown below

Principles

Curve of Normal Distribution

• The curve called normal distribution curve tells us that in the majority of cases the tendency for the number of heads to equal the number of track.

• Normal distribution curves may be of different shapes. They may be flatter or more rounded.

• x - Average or measure of central distribution - The deviation from the average called

standard deviation• The area under the curve of normal distribution can be

calculated p = Standard in or of production• p = on both sides of x given 68.27 % of total areas

Principles

• Two p on both sides gives area 99.45• Three p on both sides gives area 99.73• If we base our study on 2 ; 99.45 of our

observations will fall within x + 2 p and 99.73 will fall within x + 3 p

• In work sampling we commonly use 99.5% confidence level.

Principles

A. Prepare for work sampling study

i. State objective of study

ii. Obtain concurrence of the supervision of department

iii. Establish quantitative measure of activity

iv. Selection of training of personnel

B. Performing Work Sampling

i. Describing and classifying elements

ii. Design of observation form

iii. Determine the period of study

iv. Determine randomized times of observation

v. Observing activity and recording data

vi. Summarizing the data at the end of each day

Procedure to conduct Work Sampling Study

C. Evaluating and Presenting results of Study

i. Evaluate the validity and reliability of data

ii. Presenting and analyzing data

iii. Planning for future studies

Determine Sample size

Procedure for selecting random observation

Error in work sampling

Conducting the work sampling study

Procedure to conduct Work Sampling Study

Work Study Predetermined Motion Time Systems

3. iii. D

Work Study Predetermined Motion Time Systems

• To establish standard time, we have subdivided work operation into elements of work, description of work, time taken to perform and add allowances to cover delays and fatigue etc.

• Later basic motions have been established by photographic / video studies by go / breath and these standardized motions are called “Therbligs”. Expansion of these studies by Taylor and Gilbreth has resulted in “Predetermined elemental times” (PDTM) using PDTM.

Work Study Predetermined Motion Time Systems…

• Defined as work measurement where by the time established for basic human motions are used to build up the time for a job at a defined level of performance.

• While using the systems for establishing elemental times, care is necessary to analyze component motions going into a much greater detail than done in method study analysis.

• Earlier these systems were considered suspicious but are now being widely accepted even in Indian industries.


• Example: Drilling OperationPick up partMove to spindle

• MTM Fundamental MotionsReach PositionMove DisengageApply Pressure ReleaseTurn Grasp


Pedal & Trunk Motions• Side set-up• Turn body• Walk• Bend• Stoop• Kneel on one leg• Kneel on both leg• Foot motions• Sit

MTM Application ProcedureMETHOD TIME MEASUREMENT

Determine the standard time for the most economical method:1. Establish Basic Method.2. Operational Basic Method.

a. Quality specificationb. Production equipmentc. Equipment / accessories and tools usedd. Location of plant and working conditione. Material usedf. Component drawingg. Operations involved.

MTM Application Procedure

3. Prepare detailed elemental breakdowna. Break activity into work elements and then MTM

motions.b. Describe element and record description.c. Record on MTM analysis sheet the various

motions to be carried out by both hands. d. Check motion sequence.e. Sign the study sheet.

4. Carryout the complete study.

MTM Application Procedure

Assign TMU’s to each element synthesize and arrive at the total time:

Convert TMU’s into equivalent time valves. Add necessary allowance. Compute and record the allowed time per element

and then per operation.

One can also use simplified MTM data

Source: Work Study and O&M

by Andhra Pradesh Productivity Control

Publisher: Andhra Pradesh Productivity Control

3.III Work Measurement

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