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OPERATIONS MANAGEMENT

Lecture 3

Hamendra Dangi

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mailto:[email protected]

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Job DesignThe act of specifying the contents and methods of jobs.

Job designers focus on

• what will be done in a job,

• who will do the job,

• how the job will be done, and

• where the job will be done.

The objectives of job design include productivity, safety, and quality of work life.

Ergonomics is the incorporation of human factors in the design of the workplace.

It relates to design of equipment, design of work methods, and the overall design

of the work environment.

Current practice in job design contains elements of two basic schools of thought.

One might be called the efficiency school because it emphasizes a systematic,

logical approach to job design; the other is called the behavioral school

l because it emphasizes satisfaction of wants and needs.

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Specialization

http://www.baskent.edu.tr/~kilter3

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Behavioral Approaches to Job Design

Job enlargement. Giving a worker a larger portion of the total

task, by horizontal loading. (horizontal loading)

Job rotation. Workers periodically exchange jobs. means

having workers periodically exchange jobs.

Job enrichment. Increasing responsibility for planning and

coordination tasks, by vertical loading. (vertical loading)


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Methods Analysis

Selecting an Operation to Study

Documenting the Current Method

Analyzing the Job and Proposing New Methods

Installing the Improved Method

The Follow-Up

Analyzing and improving methods is facilitated by the use of various charts

such as flow process charts and worker-machine charts.


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Flow process charts are used to

review and critically examine the

overall sequence of an operation

by focusing on the movements of

the operator or the flow of

materials.


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Motion Study

systematic study of the human motions used to perform an operation.

Motion study principles

The use of the human body.

The arrangement and conditions of the workplace.

The design of tools and equipment.


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Working ConditionsTemperature and Humidity.

Ventilation.

Illumination.

Noise and Vibrations.

Work Breaks.

Safety.

Ethical Issues.


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Work Measurement

standard time is the amount of time it should take a qualified worker to complete

a specified task, working at a sustainable rate, using given methods, tools and

equipment, raw material inputs, and workplace arrangement.

• stopwatch time study

• historical times

• predetermined data

• work sampling


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where

n = Sample size needed

z = Number of normal standard deviations needed for desired confidence

s = Sample standard deviation

a = Desired accuracy percentage

x = Sample mean

where

e = Maximum acceptable errror

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ExampleA time study analyst wants to estimate the time required to perform a certain job.

A preliminary study yielded a mean of 6.4 minutes and a standard deviation of

2.1 minutes. The desired confidence is 95 percent. How many observations will

he need (including those already taken) if the desired maximum error is

a. ±10 percent of the sample mean?

b. One-half minute?


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Time Study Example

Desired accuracy with 5%Confidence level = 95%Sample standard deviation = 1.0Sample mean = 3.00

n =

2zs

hx

n = = 170.74 ≈ 171

21.96 x 1.0

.05 x 3

h = .05 x = 3.00 s = 1.0

z = 1.96 (from Table S10.1 or Appendix I)

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Time Studies

Involves timing a sample of a worker’s performance and using it to set a standard

Requires trained and experienced observers

Cannot be set before the work is performed

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Time Studies

1. Define the task to be studied

2. Divide the task into precise elements

3. Decide how many times to measure the task

4. Time and record element times and rating of performance

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Time Studies

5. Compute average observed time

Average observed

time

Sum of the times recorded to perform each element

Number of observations=

6. Determine performance rating and normal time

Normal time = xAverage observed

time

Performance rating factor

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Time Studies

7. Add the normal times for each element to develop the total normal time for the task

8. Compute the standard time

Standard time =Total normal time

1 - Allowance factor

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Rest Allowances

Personal time allowance

4% - 7% of total time for use of restroom, water fountain, etc.

Delay allowance

Based upon actual delays that occur

Fatigue allowance

Based on our knowledge of human energy expenditure

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Rest Allowances

1. Constant allowance

(A) Personal allowance ……………... 5

(B) Basic fatigue allowance ………… 4

2. Variable allowances:

(A) Standing allowance ……………… 2

(B) Abnormal position

(i) Awkward (bending) ………… 2

(ii) Very awkward (lying, stretching) …………………… 7

Figure S10.1

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Rest Allowances

(C) Use of force or muscular energy in lifting, pulling, pushing

Weight lifted (pounds)

20 …………………………………… 3

40……………………………………. 9

60……………………………………. 17

(D) Bad light:

(i) Well below recommended…. 2

(ii) Quite inadequate……………. 5Figure S10.1

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Rest Allowances

(E) Atmospheric conditions (heat and humidity) …………… 0-10

(F) Close attention:

(i) Fine or exacting……………….. 2

(ii) Very fine or very exacting…… 5

(G) Noise level:

(i) Intermittent—loud…………….. 2

(ii) Intermittent—very loudor high-pitched………………... 5

Figure S10.1

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Rest Allowances

(H) Mental strain:

(i) Complex or wide span of attention.…………………….. 4

(ii) Very complex………………….. 8

(I) Tediousness:

(i) Tedious…………..……………… 2

(ii) Very tedious.…………………… 5

Figure S10.1

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Time Study Example

Average observed time = 4.0 minutesWorker rating = 85%Allowance factor = 13%

Normal time = (Average observed time) x (Rating factor)

= (4.0)(.85)

= 3.4 minutes

Standard time = = =Normal time


3.4

1 - .133.4

.87

= 3.9 minutes

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Time Study Example

Allowance factor = 15%

PerformanceJob Element 1 2 3 4 5 Rating

(A) Compose and type letter 8 10 9 21* 11 120%

(B) Type envelope address 2 3 2 1 3 105%

(C) Stuff, stamp, seal, and 2 1 5* 2 1 110%sort envelopes

Cycle Observed (in minutes)

1. Delete unusual or nonrecurring observations (marked with *)

2. Compute average times for each element

Average time for A = (8 + 10 + 9 + 11)/4 = 9.5 minutes

Average time for B = (2 + 3 + 2 + 1 + 3)/5 = 2.2 minutes

Average time for C = (2 + 1 + 2 + 1)/4 = 1.5 minutes

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Time Study Example

3. Compute the normal time for each element

Normal time for A = (9.5)(1.2) = 11.4 minutes

Normal time for B = (2.2)(1.05) = 2.31 minutes

Normal time for C = (1.5)(1.10) = 1.65 minutes

Normal time = (Average observed time) x (Rating)

4. Add the normal times to find the total normal time

Total normal time = 11.40 + 2.31 + 1.65 = 15.36 minutes

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Time Study Example

5. Compute the standard time for the job

Standard time =Total normal time


= = 18.07 minutes15.36

1 - .15

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