1 procedure for the determination of time required to perform a task involving either human or...
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Procedure for the determination of time
required to perform a task involving either human
or machine under certain standard conditions of
measurement
• Direct time study
• Predetermined time system
• Standard time data
• Work sampling
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Systematic procedure that divides an
operation into motions or work elements, with a
set of time data assigned to each elements
• Allowance excluded
• Various available systems, for examples
• Work - Factor System
• Method - Time Measurement (MTM)
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• Developed from 4-year implementation of Micromotion study
• Employed in 1938
• Four techniques:
• Detailed• Ready • Brief• Mento-Factor
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• Body Members
Finger, Hand, Arm, Body, Leg , Foot, etc.
• Distance by Inch
• Weight & Resistance
• Manual Control
Basic, Definite stop, Directional control,
Care, Change of direction
Time Unit: 1/10,000 min
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• Body Members
• Distance by Inch
• Weight & Resistance
• Manual Control
T, FT, L, HT
F, H, A, FS
0 = Basic
1, D = Definite stop
2, S = Directional control
3, P = Care
4, U = Change of direction
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A10
Description of job: …..
Time Required: …...
A30WS
Description of job: …..
Time Required: …..
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• More Focus on Basic elements
• First developed for Drill Press Work
• Time Unit: 1/ 100,000 hr
(TMU, 0.0006 min)
• A family of MTM
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• Transport (Reach & Move)
• Grasp
• Pre-Position
• Assemble
• Use (Manual, Process or Machine)
• Disassemble
• Mental Process
• Release
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Reach• Class of Reach: A - E
• Distance measured in Inch
• Motion of hand
• Example: R8C, Time Unit= 11.5
• Equivalent to …… Min.
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Move• Class of Move: ……..
• Load measured in …….
• Motion of hand ??
• Example: mM10C, Time Unit= …...
• Equivalent to …… Min.
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• Trial time study, Based on work instruction & work station layout
• Verify time data, Compared to Direct time study
• Applicable to most of jobs
• No Rating Factor
• Facilitate Motion-Minded training
• Tools & equipment Design / Setup
• Estimate processing time required for cost
estimation
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• Selection of Various Systems
• Well trained analyst
????
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Applications
1) Determine machine utilization / downtime
2) Determine allowances
3) Establish time standards
Concept: To find out the proportions of total time
devoted to various activities that constitute a
job, by taking a large number of observations
at random times.
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Basic idea
• Random sampling over a long period of working hour
• Binomial distribution: p,q ratio out of n observations,
which approaches Normal distribution when n is large
npq
Distribution of a proportion: at 95%CI and +/- 5% relative accuracy, Z = 1.96
Mean, proportion of working time = p
Standard Deviation =
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0) Obtain cooperation from all concerns
1) Trial observations or a past record
2) Determine the number of obs. needed: Alignment chart
3) Design data collection procedure
a. Observer: number of person, position
b. Period of the study
c. Time table for daily random observation
d. Observation sheet
4) Assure 95% CI and +/- 5% relative accuracy
5) Calculate utilization ratio or standard time
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Table of Random Numbers
Daily working hours
Frequency of daily obs.
Routes of observation
Observation sheet
Observe At First sight
Data Summary and control
Recheck CI and accuracy level
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Control Chart (P chart) is to make sure every reading is in normal condition
mean
UCL = p + 3sigma
LCL = p - 3sigma
day
p, daily
mean = expected value of relevant proportion, p
sigma = standard deviation of p
3 sigma = 99.7% of population should fall within the range
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P chart: To detect unusual situation during the study
Within chart values
Out of chart values
Reasons of the unusual daily p
a) accident
b) lack of proper production flow
c) a change in expected value of p reconstruct the p chart, using the new information
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• 95% CI & +/- 5% relative accuracy
• Alignment chart or
Table for determining the number of obs.
given degree of accuracy, value of p at 95% CI
• Table for determining the degree of accuracy given number of obs., value of p at 95% CI
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total output during total time
Rep. Time = (total time spent) (proportion)
Normal Time = Rep. Time (Performance Index)
Std. Time = Normal Time + Allowances
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Advantages: compared with Direct time Study
• No continuous observation
• Normally less cost
• Study crew operation by one analyst
• Study long cycle time operation
• Easy to observe
• Don’t need specialist
• Operator would not feel under too much attention
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Disadvantages
• No details about operation
• Not suitable for short cycle task
• ??