Reza Afshar_Time Study Presentation

FOR INTERNAL USE ONLY

Time Study

Reza Afshar

I.E. Department

Nov 2015

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Time Study Issue

• why is time study important to the organization?

• What are some worker concerns?

• How can they be resolved?

Time Study | Reza Afshar | 2015

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Definition And Objectives:

Time study is a technique of establishing an allow time standard for performing

a given task, based on measurement of the work content of the prescribed

method, with due allowance for fatigue and for personal and unavoidable

delays.

The objective of time study is to determine reliable standards for all work, both

direct and indirect, being undertaken by the enterprise for the efficient and

effective management of the operation.

With reliable time standards, capacity in terms of anticipated output, can be

determined of equipment and facilities. Work can be scheduled so as to

maximize out put over time, thus obtaining high utilization of both labor and

equipment. A system of variance reporting can be introducing thus simplifying

good management. Management can investigate the difference between

actual and standard times and appropriate action where necessary.


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Standard Times Facilities Methods Engineering:

Since is a common measure for all jobs, time standards are a basis for

comparing various methods of doing the same piece of work.

Standards times provide a basis for purchasing the most productive new

equipment.

They provide the means for introducing sound production control.

Furthermore, standard times serve as a means of securing an efficient layout

of the available space.

Since time is the basis for determining how much of each kind of equipment is

needed.

Accurate time standards provide a means of balancing the work with the

available work.

A further objective of the development of reliable time standards is the

procedure of accurate cost determination in advance of production.

Other good management practices that may be enhanced with the application

of measured time standards include budgetary control, the development of

supervisory bonuses, and ensuring of the maintenance of quality requirements.


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Time Study Equipment:

- Decimal minute stopwatches, a. mechanical , b. Electronic

- Decimal hour stopwatches, a. mechanical , b. Electronic

- Date collecting machine

- Videotape Equipment

- Motion picture camera


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Personal Characteristic:

Good Judgment

Analytic Ability

Honesty

Resourcefulness

Self-Confidence

Tact

The importance of the work measurement procedure, the following

personal characteristics can be considered essential for the successful

work measurement analyst:

Patience

Optimism

Pleasing Personality

Enthusiasm

Neat Appearance


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The Analyst should also regularly meet the following requirements:

To study the existing method carefully before conducting the time to ensure

that the method is correct.

To review with the supervisor all aspects of the operations in order to obtain

his or her endorsement of the tooling, materials, and procedure, being utilized

by the operator.

To respond to any questions posed by the operator, the union steward, or the

supervisor regarding the time study procedure.

To record accurately an adequate sample of element times in order to allow

the development of an equitable standard.

To evaluate the performance of the operator honestly and fairly.

To apply an appropriate allowance to all normal times where applicable.

To calculate accurately the standard times for each element for the time study.

To conduct himself or herself in such a manner that he or she will obtain and

hold the respect and confidence of the representative of both labor and

management.


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Direct Time Study Procedure:

• Define and document standard method

• Divide task into work elements

• Time work elements

• Rate workers performance

• Apply allowances


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Define and document standard method:

Goal: “One the best method”

Seek workers advice, if appropriate

Elements of document

Procedure(steps, actions, work elements, hand/body motions)

Tools, equipment

Machine setting(e.g., feeds, speeds)

Workplace layout

Frequency of irregular elements

working conditions

Setup


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Reasons for thorough documentation:

Batch production(likely to be repeated)

Methods improvement by operator

Disputes about method(too tight?)

Data for standard data system


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Divide Task Into Work Elements(1):

Series of motion activities logically grouped because of unified

purpose

Guidelines

Each work element should consist of a logical group of motion elements.

• e.g., reach, grasp, move, place

Beginning point of one element should be end of previous.

• NO time gap between elements.

Each element should have readily identifiable end point.

• i.e., easily detected, no ambiguity

Work elements should not be too long.

• < “several” min


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Divide Task Into Work Elements(2):

Guidelines(continued)

Work elements should not be too short.

• > 3 sec

Irregular elements should be identified & distinguished.

• i.e., not every cycle

Manual elements should be separated from machine elements.

• generally constant values

Internal elements should be separated from external elements.

• i.e. , performed by operator during machine cycle


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Irregular and Foreign Elements:

- Elements that occur routinely, but not every cycle-should be

included: irregular elements

- Elements that observer didn’t anticipate - probably should be

included: irregular elements

- Elements that are not normal work – should not be included:

foreign elements


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Time Work Elements(3): - Use stopwatch calibrated in 0.01 minutes:

Snapback method

• Start watch at beginning of every element.

• “ Snap” watch back to zero at end of element.

• Record time.

• Advantages. Element variations easily observable

No subtraction

Continuous method

• Start watch at beginning of observation(or beginning of each cycle)

• Record elapsed time at end od each element.

• Let it run …

• Advantages.

No so much manipulation of stopwatch.

Elements not so easily omitted.

Regular/irregular elements more readily distinguished(?)


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Rate Worker‘s performance

- Standard performance = 100%

- Rate

• Individual elements.

• Or entire work cycle.

- Most difficult & controversial step in time study

- Requires analyst’s judgment


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Effects of Working Conditions on Determining Allowances(1);


Constant Allowances

Personal allowances 5

Basic fatigue alloance 4

Variable Allowance

Standing allowances 2

Abnormal position allowances

Slightly awkward 0

Awkward (bending) 2

Very awkward (lying, stretching) 7

Use of force or muscular energy(lifting, pulling, or pushing) - weight lifted, in pounds:

5 0

10 1

15 2

20 3

25 4

30 5

35 7

40 9

45 11

50 13

60 17

70 22

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Effects of Working Conditions on Determining Allowances(2);

Bad light

Slight below recommended 0

Well below 2

Quite inadequate 5

Atmospheric conditions(heat and humidity)-variable 0-10

close attention

Fairly fine work 0

Fine or exacting 2

Very fine very exacting 5

Noise level

Continuous 0

Intermittent-loud 2

Intermittent-very loud 5

High-pitched-loud 5

Mental Stain

Fairly complex process 1

Complex or wide span of attention 4

Very complex 8

Monotony

Low 0

Medium 1

High 4

Tediousness

Rather tedious 0

Tedious 2

Very tedious 5

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Apply Allowance Pure Manual Work

Work Element a b c d*

Obs. Time 0.56 min 0.25 min 0.50 min

1.10 min

Perf. Rating 100 % 80 % 110 % 100 %

* irregular element performed every 5 cycles

PFD Allowance = 15 %

Standard time = Normal time * (1+allowances% )


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Apply Allowance Pure Manual Work


Obs. Time 0.56 min 0.25 min 0.50 min

1.10 min

Perf. Rating 100 % 80 % 110 % 100 %



Normal Time:

NT= 0.56(1.00) + 0.25(0.80 )+ 0.50(1.10) + 1.10(1.00)/5

= 0.56+0.20+0.55+0.22 = 1.53 min

Standard Time:

ST = 1.53(1+0.15) = 1.76 min


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Apply Allowance Task Including Machine Cycle


Obs. Time 0.22min 0.65 min 0.47 min

0.75 min

Perf. Rating 100 % 80 % 100 % 100 %

Mach. Time (idle) M 1.56 min (idle) (idle)



Machine Allowance = 20 %

Normal Time:

NT = 0.22(1.00) + Max{0.56(0.80),1.56} + 0.47(1.00) + 0.75(1.00)/15

= 0.22 + 1.56 + 0.47 + 0.05 = 2.30 min

Standard Time:

NT = (0.22 + 0.47 + 0.05)(1+0.15) + Max{0.52(1+0.15),1.56(1+0.20)}

= 0.85 + 1.87 = 2.72 min


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Number of Cycle To Be Timed

Let X be random variable, time of one work element in a task.

Time several cycle to estimate true mean:

ɑ/2 ɑ/2 1-a

low

estimate

ɑ/2 ɑ/2 1- ɑ

ɑ/2 ɑ/2 1-ɑ

close

estimate high

estimate

x µX

Overall, P(µx lies within X ± za/2 [σ/√nc])= 1 – ɑ

where nc = number of cycles timed

But σ unknown, so take preliminary sample of ns observations and use:

s=√(∑(x-x)^2) (ns-1)

x x


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Number of Cycle To Be Timed (2)

P(µx lies within X ± ta/2 [s/√nc]) = 1 – ɑ

Interval size = X ± KX

“ where K = proportion of sample mean”

(e.g. , if k=10%, interval size = X ± 0.10 X)

KX= ta/2 [s/√nc] (remember, s is an estimate of σ based on preliminary sample of ns)

So, rearranging,

nc=(ta/2s/kx)^2


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Number of Cycle To Be Timed : Example

From preliminary study, engineer has collected ns=10 samples on one work element;

- X=0.40 min

- S=0.07 (an estimate of ɑ based on preliminary of ns=10)

How many cycles should be timed to ensure element time is ± 10 % of the sample

mean, with 95 % cinfidence?

- df=(ns-1)=10-1=9

- ɑ= 0.05, ɑ/2=0.025

- tɑ/2=t0.025= 0.025

- Number of cycles = nc = (tɑ/2s / kx)^2 = [2.262(0.07) / 0.10(0.40)]^2

- = 15.7 ≈ 16 cycles

if 16 observed cycles yields

X=0.45 min

P(µx lies within X ± KX) = P(µx lies within 0.45 ± 0.10(0.45))

= P(µx lies within [0.405,0.495] = 95 %


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Determining the number of cycles to study Number of cycles required for a time study

Minimum Number of Cycles to Study for Given Activity:


Cycle time More than

10000/year

5000 to 10000

year

1000 to

5000/year

Less than

1000/year

More than 60 min 6 5 4 3

40 to 60 min 8 7 6 5

20 to 40 min 10 9 8 7

10 to 20 min 12 11 10 9

5 to 10 min 20 18 16 15

2 to 5 min 25 22 20 18

1 to 2 min 40 35 30 25

Less than 1 min 60 50 45 40

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Performance Rating (1)

• Also called performance leveling.

• Performance relative to engineer’s concept of “standard” performance.

• Most common method based on speed or pace: speed rating.

• > 100% means faster than standard pace

• engineer must use judgment

• must consider

degree of difficulty of work element

worker’s pace relative to standard

• Standards

• walk 3 mi/hr on flat, level ground, no load, 27-in steps.

• Problems: few work situation lend themselves to such precise

measurement.

• However, many situations in which experts judge

• Solutions

• Experience(including feedback)

• Training(e.g., using training films)


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Performance Rating (2)

• Pace depends on worker’s

• skill

• experience

• exertion

• attitude toward time study

• So, select skilled worker

• familiar with job

• Accepts time study as necessary management tool

• Characteristics of good performance rating system

• consistency among tasks(one task to another)

• consistency among engineers

• easily understood

• related to understand performance(well-defined concept)

• machine-paced elements rated at 100% (no worker control of machine)

• rating recorded during observation, not after

• worker notification


Reza Afshar_Time Study Presentation

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