3.1 work measurement_time study_w4

8/10/2019 3.1 Work Measurement_Time Study_W4

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7-2 Design of Work Systems

Work MeasurementWork Measurement

TIME STUDY

Standard time

Stopwatch time study

Historical times

Predetermined data

Work Sampling


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Historical ExperienceHistorical Experience

Relatively easy, convenient, and inexpensive

Not objective, unknown accuracy

Not recommended


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Labor processing standards are based onobserving worker doing task

Observe only a sample of work

Time StudiesTime Studies

Use average time & pace to set standard

Disadvantages

Requires a trained & experienced analyst Standard cannot be set before task is

performed


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The Eight Steps to Conducting aThe Eight Steps to Conducting aTime StudyTime Study

1. Define the task to be studied (after a methods

analysis)

2. Break down the task into precise elements

.

must be measured

4. Record the times and ratings of performance for

the task elements[Rating = (Observed rating / standard rating)]

(*Rating = assessment of a worker relative work rate based on observers

observation compared with standard pace.)


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7-6 Design of Work SystemsThe Eight Steps to Conducting aThe Eight Steps to Conducting aTime StudyTime Study -- continuedcontinued

5. Compute the average observed cycle time (elementtimes adjusted for unusual influences)

6. Compute the normal time for each task element

Normal time = (Average actual cycle time) x (Rating factor)


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7. Sum the normal times for each element to

develop a total normal time for the task

The Eight Steps to Conducting a TimeThe Eight Steps to Conducting a Time

StudyStudy -- continuedcontinued

.

Standard time =Total normal time

(1- Allowance factor)


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Direct Time Study (Example)Direct Time Study (Example)

Element Cycle 1 Cycle 2 Cycle 3 Cycle 4 Cycle 5 Average Normal

time

Std

time

1 8 9 8 10 8 8.6 9.46 11.129

2 10 12 10 11 12 11 12.1 14.235

3 25 25 25 25 25 25 25 25

4 8 8 6 8 6 7.2 7.92 9.318

Element 1:

Average time = (8+9+8+10+8)/5 = 8.6 sec

Normal time = Average time x Rating = 8.6 x 1.1 = 9.46 sec

Standard time = Normal time /(1-allowance) = 9.46 / (1-0.15) = 11.129 sec

Total Standard Time = 11.129+14.235+25+9.318 = 59.682 sec/product


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-- Example 2Example 2 --

Work Elements Cycle 1 Cycle 2 Cycle 3 Cycle 4

1 0.22 0.26 0.25 0.23

2 0.15 0.18 0.15 0.16

3 0.90 1.10 1.04 1.00

4 0.72 0.80 0.76 0.68

study. The worker is rated at 108%. The allowances are 5% for fatigue, 6% for delay,and 6% for personal relief. The workers salary is RM1000 per month.

a) Compute the total assembly standard time for the assembly process.

b) If the demand is 100,000 unit per month, estimate the number of operators

required for the assembly process. The company is operating 24 days per monthand a single 8 hour shift per day.

c) If the company can only manage to employ 18 workers, compute the over time

cost per day for each workerfor the production of 100,000 units per month.

Assume only 15 workers are available for over time and the over time pay rate is 1.5times of the normal wage.


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Solved ProblemSolved Problem

Element Cycle 1 Cycle 2 Cycle 3 Cycle 4 Average Normal

Time

Std

Time

1 0.22 0.26 0.25 0.23 0.24 0.259 0.312

2 0.15 0.18 0.15 0.16 0.16 0.173 0.2083 0.90 1.10 1.04 1.00 1.01 1.091 1.314

4 0.72 0.80 0.76 0.68 0.74 0.799 0.963

min/unit2.7970.9631.3140.2080.312TimeStandardAssemblyTotal

min312.017.01

1259.0

Allowance-1

1xTimeNormalTimeStandard

min0.2591.08x0.24RatingxTimeAverageTimeNormal

min24.04

0.230.250.260.22TimeAverage

=+++=

=

==

===

=+++

=


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min520,11

min602481operator1oftimeWorking

(b)

==mthhrmth

day

day

hr

b) If the demand is 100,000 unit per month, estimate the number of

operators required for the assembly process. The company is operating 24

days per month and a single 8 hour shift per day.

2524.28

mth

unit4118.70

mth

unit100,000

operatorperCapacity

DemandMonthlyrequiredoperatorsofNumber

mth

unit4,118.70

unit

min2.797

min520,11operator1byproducedquantityMonthly

===

== mth


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unit

137,7418mth

unit4,118.70operators18byproducedquantityMonthly

(c)

units==

c) If the company can only manage to employ 18 workers, compute the over time

cost per day for each workerfor the production of 100,000 units per month.

Assume only 15 workers are available for over time and the over time pay rate is 1.5

times of the normal wage.

234.50min

014,3

min797.26.1077

day

unit1077.6producedtorequiredTime

6.1077

24

mth

unit25,863

shortagequantityDaily

mth

,,-,s ortagequant tyont y

day

hr

day

unitday

unit

day

unit

mth

day

==

=

==

== (monthly shortage, need OT)


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Labor standard is set using output and % oftime worker spends on tasks

Involves observing worker at random timesover a long period

Work SamplingWork Sampling

van ages Less expensive than time studies

Observer requires little training

Disadvantages Ineffective with short cycles


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Used for

Ratio delay studies

Setting labor standards

Work SamplingWork Sampling

Measur ng wor er per ormance


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7-19 Design of Work SystemsThe Five StepThe Five Step

Work Sampling ProcedureWork Sampling Procedure

1. Take a preliminary sample to obtain an

estimate of the parameter value

2. Compute the sample size required

.

worker at appropriate times

4. Observe and record worker activities; rate worker

performance

5. Determine how workers spend their time (usually

as a percent)


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Work Sampling (Example)Work Sampling (Example)

Status Tally Sum Percentage

Productive IIIII IIIII IIIII IIIII IIIII IIIII IIIII IIIII I 41 41/45 = 91%

Idle IIII 4 4/45 = 9%

Work sampling studies were conducted for 6 consecutive days at a factory.

A total of 45 observations were made during the 8 hours working period for

each day. The number of units managed to be produced are 3000 units for 1

week. The factory is operating 6 days a week. The data above are included

with rating and allowance of 97% and 15%.

Compute the process standard time.


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Work Sampling (Example)Work Sampling (Example)

Status Tally Sum Percentage

Productive IIIII IIIII IIIII IIIII IIIII IIIII IIIII IIIII I 41 41/45 = 91%

Idle IIII 4 4/45 = 9%

min2880day6hr

min60

da

hr8n timeobservatioTotal ==

unit

min0.997

15.01197.091.0

unit3000min2880STTime,Standard

allowance1

1Rating]%Productive

outputTotal

n timeobservatioTotal[

STTime,Standard

=

=

=


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Tutorial 1Tutorial 1

Proses Description Average Time (min)

1 Manual 23

2 Manual 32

3 Automatic machine 9

4 Manual 8

Rating : 110%Allowance: 20%

(a) Compute the standard time for each process.

(b) If the company has no problem with the availability of manpower,recommend the maximum capacity for the factory for a 8 hour shift work.


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Proses Description Average Time

(min)

Normal

time

Std Time

1 Manual

2 Manual

(a)

machine4 Manual

(b)


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Emirates Consultant conducted a work sampling studies for 5 consecutive days at an

assembly factory. A total of 48 observations were made during the 8 hour working

period for each day. The data collected during the 5 day studies is illustrated in Table

1. The whole assembly process is operating on 5 working days per week, 95% rating

and the companys allowable allowances is 20%.

(i) Compute the standard time (min/unit) for the assembly process.

(ii) At peak demand period, the factory is normally required to produce 3,100 units per

. ,

overtime per day must be arranged in order to meet the peak demand.

Item Data

Total output over 5 days studies 2,500 unit

Assembly process at fast speed 35% of observationsAssembly process at moderate speed 45% of observations

Assembly process at slow speed 5% of observations

Production is stopped due to no operator 5% of observations

Production is stopped due to no material 10% of observations


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TimeStd

n timeobservatioTotal

(i)

=

=

day

unit

wk

unit

hours8normalduringCapacity

DemandPeak

(ii)

=

=


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day

min

hoursover timetheover time,dotoforcedareemployeesallIf

unit/dayshortageCapacity

=

=

day

hourovertimethen total

over time,foravailableareemployeesof60%onlygConsiderin

=

7 28 D f W k S


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END OF CLASSEND OF CLASS

3.1 work measurement_time study_w4

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