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FOR INTERNAL USE ONLY
Time Study
Reza Afshar
I.E. Department
Nov 2015
2 | © Bühler |
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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.
Time Study | Reza Afshar | 2015
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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.
Time Study | Reza Afshar | 2015
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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.
Time Study | Reza Afshar | 2015
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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
Time Study | Reza Afshar | 2015
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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(?)
Time Study | Reza Afshar | 2015
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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
Time Study | Reza Afshar | 2015
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Effects of Working Conditions on Determining Allowances(1);
Time Study | Reza Afshar | 2015
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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Time Study | Reza Afshar | 2015
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% )
Time Study | Reza Afshar | 2015
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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 %
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
Time Study | Reza Afshar | 2015
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Apply Allowance Task Including Machine Cycle
Work Element a b c d*
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)
* irregular element performed every 5 cycles
PFD Allowance = 15 %
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
Time Study | Reza Afshar | 2015
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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
Time Study | Reza Afshar | 2015
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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
Time Study | Reza Afshar | 2015
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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 %
Time Study | Reza Afshar | 2015
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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:
Time Study | Reza Afshar | 2015
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
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Time Work Elements(1): Collect data on time study form (on clipboard).
Time Study | Reza Afshar | 2015
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Time Work Elements(2): Standard Time Form
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www.buhlergroup.com
Time Study | Reza Afshar | 2015
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