END 202
END
202
Work Analysis and Design
‐ Time Study ‐
Ti
S d
Sibel ALUMUR ALEV
Sibel ALUMUR ALEV
February 2011
END 202 – Work analysis and design
Time Study
Method engineering steps
1.
2
2.
3.
4
4.
5.
6.
7.
8.
Select project (Pareto, Fish diagram, Gantt, PERT)
Get and present data (charts computations)
Get and present data (charts, computations)
Analyze data (operation analysis)
Develop ideal method (motion work equipment
Develop ideal method (motion, work, equipment design)
Present and install method (decision making tools)
(
g
)
Develop job analysis
Establish time standards (time study)
Follow up
END 202 – Work analysis and design
Time Study
Time study
• Time study is a technique for recording times Time study is a technique for recording times
and rates of working for specific job elements to establish standards
bli h
d d
• Why do we measure time?
– The most meaningful and useful measure of work is the amount of time it takes to accomplish it
p
– Time is objective
– Time is quantifiable
Time is quantifiable
– People understand time
END 202 – Work analysis and design
Time Study
Standard time
• Standard Time is the time that a person suited to the job and fully trained in the specified method will need to perform the ifi d
h d ill
d
f
h
job if he/she works at a normal or standard tempo
• Includes some additional time called allowances to provide for the worker’s f
’
personal needs, fatigue, and unavoidable d l
delays
END 202 – Work analysis and design
Time Study
Standard time can be used… •
•
•
•
•
•
To define a To
define a “fair
fair day
day’ss work
work”
To determine manpower requirements and capacity limitations
To compare alternative methods for accomplishing the same task
To provide a basis for wage incentives and for evaluating worker performance
To estimate cost
To estimate cost
To provide time data for production planning and scheduling, material requirements planning and g
q
p
g
other management functions that depend on accurate task time data
END 202 – Work analysis and design
Time Study
Time study
Methods to determine time standards:
• Estimation
• Historical records
• Time study techniques:
– Direct time study (with chronometer)
y(
)
– Standard data and formulas
– Predetermined time systems
Predetermined time systems
– Work sampling
END 202 – Work analysis and design
Time Study
Engineered standards
Direct time study
•
•
•
•
•
Involves direct observation of a task using a stopwatch or other chronometric device to record time
The task is divided into work elements and each work element is timed separately
Performance rating: The worker’s performance (pace) is evaluated
N
Normal time is calculated considering the performance l ti
i
l l t d
id i th
f
rating
Allowance is added to the normal time to determine the
Allowance is added to the normal time to determine the standard time
END 202 – Work analysis and design
Time Study
Standard data and formulas
•
•
Finding normal time values for work elements used in tasks using previously determined standard data or formulas
Steps:
–
–
–
–
Identify the work elements that make up the task together with the values of variables
Access the database to find the normal time for each f
f
element or use analytical formulas
Sum to determine the normal time for the task
Sum to determine the normal time for the task
Add allowances to determine standard time
END 202 – Work analysis and design
Time Study
Predetermined time systems
•
•
•
•
Relies on a database of basic motion elements (therbligs) such as reach, grasp, move
A
Associated with each motion element is a set of normal i t d ith
h
ti
l
ti
t f
l
times depending on distance, weight, etc.
List of all the basic motion elements, find the normal
List of all the basic motion elements, find the normal time for each element from the data base, sum the normal times and add allowances
Advantages
–
–
Performance rating is not required
Can be applied to determine time standard for a task before
Can be applied to determine time standard for a task before production
END 202 – Work analysis and design
Time Study
Work sampling
• Purpose is to determine proportions of time •
•
•
spent in different activities using randomized observations
Examples: to determine machine idle times, to p
determine operator utilization When used to establish time standards
When used to establish time standards statistical errors cause the standard times to be less accurate than obtained by other techniques
less accurate than obtained by other techniques
To be studied later…
END 202 – Work analysis and design
Time Study
Prerequisites
Prerequisites for valid time standards
• The task is performed by an average worker
• The worker
The worker’ss pace represents standard performance
pace represents standard performance
• The worker uses the standard method
• The work is performed on a standard work unit
END 202 – Work analysis and design
Time Study
Direct time study (with chronometer)
END 202 – Work analysis and design
Time Study
Analyst’s responsibility
•
•
•
•
•
•
The analyst should be trained on this job
The correct people should be warned (supervisor, worker, etc.)
Be sure that you have all the equipments with you
y
q p
y
Be respectful with the worker, avoid to make unnecessary comments
unnecessary comments
Be honest with the performance of the worker
Accurately record and note the times taken (time
Accurately record and note the times taken (time study results can influence the firm policy)
END 202 – Work analysis and design
Time Study
Supervisor’s responsibility
Supervisor should
• notify the operator in advance
notify the operator in advance
• see that the proper method is established
• select the best operator: competent and has l t th b t
t
t t dh
adequate experience on the job (not too fast neither too slow)
too slow) • sign the final and original copy of the time study
END 202 – Work analysis and design
Time Study
Operator’s responsibility
Worker should
• cooperate in helping to work
• assist the time study analyst in breaking the job down into elements
• work at a steady, normal pace
y,
p
• use the exact method prescribed END 202 – Work analysis and design
Time Study
Time study equipment
•
Stop watch
–
–
Analog – outdated
Analog
Electronic
• Split = continuous
• Lap = snapback
•
•
Videotape camcorders
Time study board –
–
Holds time study form and stop watch
stop watch
Left and right handed
•
Time study software
Time
study software
– Available for PC, for palms
• Time study form
Time study form
END 202 – Work analysis and design
Time Study
Time study form
END 202 – Work analysis and design
Time Study
Time study form – zoomed
Performance rating (100% is the standard performance of a qualified operator)
For continuous timing
Cycle
R
((Rating)
g)
W
(Watch
Time)
OT
(Observed
Time)
NT
(Normal
Time)
1
85
5
5
4.25
2
100
12
7
70
7.0
3
110
23
11
12.1
4
90
32
9
81
8.1
Normal time (NT): OT x R/100
Normal time (NT): OT x R/100
END 202 – Work analysis and design
Time Study
Time study procedures
1 Select the job
1.
Select the job
– To implement wage incentives
– To control costs
To control costs
– To compare methods/jobs
2 Select the operator
2.
Select the operator
– Qualified (intelligence, education, training, fit)
– Average
• Slow worker: loose standard times •
(not good for the firm)
Fast worker: tight standard times (not good for the workers)
END 202 – Work analysis and design
Time Study
Time study procedures
3 Record
3.
Record all details about the job
all details about the job
– Machines, hand tools, fixtures, working conditions, d
department, a sketch of layout, …
k h fl
4. Examine the job and break it down into elements
– Use sight and sound for breakpoints
g
p
– Relatively fine but not less than 0.04 min (3 sec)
– Keep manual and machine elements separate
Keep manual and machine elements separate
– Separate constant elements from variable elements
END 202 – Work analysis and design
Time Study
Time study procedures
4. Examine the job and break it down into elements
Types of elements •
•
•
•
•
•
repetitive: occurs each cycle
repetitive:
occurs each cycle
occasional: not every cycle
foreign: not necessarily part of the job
g
yp
j
machine: the time is fixed (no rating)
manual: depends on worker (rating)
constant
END 202 – Work analysis and design
Time Study
Time study procedures
5. Determine the number of cycles to be timed
a)
Statistical estimations
⎛ ts ⎞
n = ⎜⎜ ⎟⎟
⎝ kμ ⎠
2
t: t‐distribution value, refer to Table A3‐3, App. 3, pg 701
t:
t distribution value refer to Table A3 3 App 3 pg 701
s: standard deviation
k: an acceptable fraction for error
p
µ: sample mean value
EExample: µ = 0.30, s = 0.09, %5 desired acceptable fraction k,
l
0 30
0 09 %5 d i d
t bl f ti k
0.05 for 24 degrees of freedom: t = 2.064 (Table A3‐3, App. 3)
N 153 3 154 b
N = 153.3 ≈ 154 observations
i
END 202 – Work analysis and design
Time Study
Time study procedures
5. Determine the number of cycles to be timed
b) Approximate guide (from General Electric Company)
C l ti
Cycle
time ((min)
i )
Recommended
number of cycles
0.10
200 (20 min)
0.25
100 (25 min)
0.50
60 (30 min)
0.75
40 (30 min)
1 00
1.00
30 (30 min)
2.00
20 (40 min)
2.00-5.00
15
5 00 10 00
5.00-10.00
10
10.00-20.00
8
20.00-40.00
5
>40.00
3
END 202 – Work analysis and design
Time Study
Time study procedures
6 Measurement
6.
R
W O
OT NT
5
5
12 7
23 11
32 9
R
W OT NT
5
7
11
9
– Continuous timing
• Stopwatch
Stopwatch is never reset
is never reset
• You record the cumulative times
• At the end you need to subtract At the end you need to subtract
times
– Snapback timing
p
g
• Stopwatch is reset each time (each elemental work)
• Read direct times from zero
– No decimal point
END 202 – Work analysis and design
Time Study
Comparison btw continuous and snapback timing
Continuous timing
• Better adapted to measure and record very short elements
(3 successive elements of <0.04 min followed by 0.15 min)
• A complete record of the entire observation period
A
l
d f h
i
b
i
i d
• All delays and foreign elements are recorded
• More clerical work is involved
Snapback timing
More suitable for long elements
No need to make successive subtractions
Delays are not recorded
Some individual elements are removed or are studied
Some individual elements are removed or are studied independently of preceding and succeeding elements
• Overall time is obtained by summing: prone to error
•
•
•
•
END 202 – Work analysis and design
Time Study
Performance rating
Different options for rating the operator
• one rating to entire study (for short cycle)
one rating to entire study (for short cycle)
• an average rating for each element • evaluate the performance of each element as it occurs (for long and diversified
as it occurs (for long and diversified movements)
Normal time (NT): OT x R/100
END 202 – Work analysis and design
Time Study
Finding standard time
Adding allowances
Adding
allowances
• Different interruptions can take place. We must provide extra time to take them into account.
– Personal interruptions (trips to the restroom, drinking fountain)
drinking fountain)
– Fatigue
– Unavoidable delays (tool breakage, supervisor d bl d l
( lb k
interruptions, material variations, etc.)
END 202 – Work analysis and design
Time Study
Finding standard time
Adding allowances to obtain the standard time
ST = NT x (1 + allowance)
ST NT x (1 + allowance)
• 15% is the average allowance used for manual elements
• 10% is the average allowance used for machine elements
END 202 – Work analysis and design
Time Study
Time study steps
END 202 – Work analysis and design
Time Study
Time study steps
END 202 – Work analysis and design
Time Study
Performance rating and allowances
END 202 – Work analysis and design
Time Study
Performance rating
Rating of 100%
Rating
of 100%
• Standard (normal) performance = 100% = rate of output achieved by a qualified worker
of output achieved by a qualified worker, without exertion, using correct method.
Some examples
Some examples
• Distributing 52 cards in 0,5 min
• Walking with 5.4 km/h
Walking with 5 4 km/h
Rating can change due to
• Environmental conditions, fatigue, quality of Environmental conditions fatigue quality of
raw material, changes in method, …
END 202 – Work analysis and design
Time Study
How to rate the performance?
Rating methods:
1. Speed rating
2 Westinghouse system
2.
W ti h
t
3. Synthetic rating
y
g
4. Objective rating
END 202 – Work analysis and design
Time Study
1. Speed rating
• Speed
Speed rate considers only the rate of work per unit time
rate considers only the rate of work per unit time
• Measurement of the effectiveness of the operator by the ratio of the observed performance to standard
ratio of the observed performance to standard performance
• Can be used for elemental, cycle, or overall rating
, y ,
g
• Works needing great precision (aircraft engine parts fabrication) can appear slower than a simple work
• Record the rating in the R column before reading the stopwatch time! Do not rate by the watch!
• Begin by rating only by 10s (80,90,110) then move onto 5s (85,95,105)
END 202 – Work analysis and design
Time Study
1. Speed rating – example
Rating
g
Verbal anchor p
points
Walking
speed (mph)
Cards dealt
in 0
0.5
5 min
0
No activity
0
0
67
Very slow
slow, clumsy
2
35
100
Steady, deliberate
3
52
133
Brisk businesslike
Brisk,
4
69
167
Very fast, high dexterity
5
87
200
Upper limit for short period
6
104
END 202 – Work analysis and design
Time Study
2. Westinghouse system
• Westinghouse Electric Corporation (Lowry et al. 1940) developed a system of 4 factors in evaluating
1940) developed a system of 4 factors in evaluating the performance of the operator:
–
–
–
–
Skill: The proficiency at following a given method
Skill
Th
fi i
t f ll i
i
th d
Effort: Demonstration of the will to work effectively
C di i
Conditions: Include temperature, ventilation, light, noise
I l d
il i
li h
i
Consistency: Evaluated as the study is worked up
END 202 – Work analysis and design
Time Study
2. Westinghouse system
END 202 – Work analysis and design
Time Study
2. Westinghouse system – example
• Once each four factor are rated sum the four values and add 1 to give the performance rating factor
• The Westinghouse System is appropriate for either cycle rating or overall study rating but not for elemental rating
END 202 – Work analysis and design
Time Study
3. Synthetic rating
• Determines a performance factor based on fundamental predetermined motion times (F)
fundamental predetermined motion times (F)
F
R=
OT
R: Performance or rating factor
F: Fundamental motion time
OT: Observed mean time
END 202 – Work analysis and design
Time Study
3. Synthetic rating – example
Element no
Element no.
Observed time (OT)
Fundamental
motion time (F)
Rating factor g
(R)
1
0.08
0.096
123%
2
0.15
–
123%
3
0.05
–
123%
4
0 22
0.22
0 278
0.278
123%
• R1 = F1/OT
/ 1 = 0.096/0.08 = 120 %
/
• R4 = F4/OT4 = 0.278/0.22 = 126 %
Average rating factor is 123%
END 202 – Work analysis and design
Time Study
4. Objective rating
• Eli
Eliminates the difficulty of establishing a standard i
h diffi l
f
bli hi
d d
pace for every type of work
R = P× D
R: Performance or rating factor
P: Pace rating factor
g
D: Job difficulty adjustment factor (amount of body used, foot pedals, bimanualness, eye‐hand coordination, handling or sensory requirements, weight handledor
resistance encountered)
END 202 – Work analysis and design
Time Study
Rating application and analysis
Rating
0.16
> 100
0.20
= 100
0.25
•
•
•
•
< 100
Normal time (NT): OT x R/100
NT = 0.2 x 100/100 = 0.2
NT = 0.16 x 125/100 = 0.2
NT = 0.25 x 80/100 = 0.2
END 202 – Work analysis and design
Time Study
Rating application and analysis
Potential mistakes
Potential
mistakes
• Subjective rating • Capacity of working memory
• Cultural norms (UK, 100% = 4 mph)
Cultural norms (UK 100% = 4 mph)
• Training is crucial:
– Tight rater = rates below actual, unfair
– Loose rater = rates above actual, easy
,
y
– Conservative = rates close to mean
END 202 – Work analysis and design
Time Study
Allowances
• Normal
Normal time does not include unavoidable delays
time does not include unavoidable delays
• Need to make adjustments to compensate for such losses
such losses
• Allowances can be applied to 3 parts of the study
– The total cycle time
– Machine time only
– Manual effort only
Manual effort only
• 2 methods for developing allowances:
– Direct observation
Direct observation
– Work sampling
END 202 – Work analysis and design
Time Study
Noting allowances
END 202 – Work analysis and design
Time Study
Types of allowances
END 202 – Work analysis and design
Time Study
Types of allowances
• Constant allowances
Constant allowances
– Personal needs (≈ 5%): restroom, smoking, drinking, lunch
– Basic fatigue (≈ 4%)
Basic fatigue (≈ 4%)
• Variable fatigue
• Special allowances
S i l ll
– Unavoidable delays: interruptions from supervisor, material i
irregularities, machine interference
l iti
hi i t f
– Avoidable delays: socializing, idleness other than rest
– Extra allowances: attention time, cleaning, tool maintenance
E t
ll
tt ti ti
l
i t l
i t
– Policy allowances: new employees, differently ables, workers on light duty
on light duty
END 202 – Work analysis and design
Time Study
Variable fatigue allowances – 1
Source: International Labour Office (ILO)
END 202 – Work analysis and design
Time Study
Variable fatigue allowances – 2
Source: International Labour Office (ILO)
END 202 – Work analysis and design
Time Study
Revised table of allowances – 1
END 202 – Work analysis and design
Time Study
Revised table of allowances – 2
END 202 – Work analysis and design
Time Study
Applying allowances
ST = NT x (1 + allowance)
(
)
ST: standard time
NT: normal time
Example:
p
P
Personal needs
l
d
50%
5.0 %
Basic fatigue
4.0 %
Unavoidable delay
Unavoidable delay
10%
1.0 %
TOTAL
10.0 %
END 202 – Work analysis and design
Time Study
How to use allowances?
•
•
•
•
•
Generally we use it to take a rest
30 min lunch time is included
2 times 10 min of rest are included
For a 8 h of work, 50 min of rest ≈ 10%
F
Frequent short breaks are preferred over h b k
f
d
infrequent, long breaks
END 202 – Work analysis and design
Time Study
Standard data and formulas
END 202 – Work analysis and design
Time Study
Standard data and formulas
•
•
•
•
•
Use standard data, tabular or graphical collections of Use
standard data tabular or graphical collections of
normal times, for common work elements
Use formulas to provide quick and consistent normal
Use formulas to provide quick and consistent normal times for variable elements
When properly applied, standard data permit the rapid establishment of accurate time standards before the job is performed
A time study formula can establish standards in a
A time study formula can establish standards in a fraction of the time required for direct time study
Advantage of formulas over standard data is that a less g
skilled person can plug data into formulas more quickly than adding standard data elements
END 202 – Work analysis and design
Time Study
Standard data and formulas
Steps:
• Identify the work elements that make up the task y
p
together with the values of variables
• Access the database to find the normal time for each element or use analytical formulas
• Sum to determine the normal time for the task
• Add allowances to determine standard time
END 202 – Work analysis and design
Time Study
Predetermined time systems
END 202 – Work analysis and design
Time Study
Predetermined time systems
•
Relies on standard times assigned to the basic elements of work: –
–
–
•
•
basic motion times: further refinement is both difficult and basic
motion times: further refinement is both difficult and
impractical
synthetic times: often the result of logical combinations of therbligs
predetermined times: used to predict standard times for new work These fundamental motions are difficult to evaluate h
f d
l
i
diffi l
l
with stopwatch time study
Associated with each motion element is a set of normal
Associated with each motion element is a set of normal times depending on distance, weight, etc.
END 202 – Work analysis and design
Time Study
Predetermined time systems
Advantages
• They are realized on several workers under controlled conditions
controlled conditions
• The analyst doesn’t need to determine the performance rating which can be subjective
performance rating which can be subjective
• The operation is not interrupted
• The level of complexities for each elemental work Th l l f
l iti f
h l
t l
k
can also be computed
• There are more than 50 systems, such as: Work‐
Th
th 50 t
h
W k
Factor, MTM, MOST, etc.
END 202 – Work analysis and design
Time Study
Methods‐time measurement (MTM‐1)
• Maynard et al., 1948
y
,
• Results of frame‐by‐frame analyses of motion picture films
• Time values for the fundamental motions are given
Ex: reach, move, turn, grasp
• Assigns to each motion a pre‐determined time Assigns to each motion a pre‐determined time
standard which is determined by the nature of the motion and the conditions under which it is made
• Westinghouse technique of rating is used
• Ex. Reaching depends on distance and type of reach. Reach is divided into five distinct cases and Move into
Reach is divided into five distinct cases and Move into 3 cases (see p. 502).
• TMU: Time Measurement Unit = 0,00001 hour
,
END 202 – Work analysis and design
Time Study
Methods‐time measurement (MTM‐1)
Steps of MTM
Steps
of MTM‐1
1
• Determine all left‐hand and right‐hand motions required to perform the job properly
q
p
j p p y
• Determine the rated times from the methods‐time data tables in TMU for each motion
– Tables I‐X: reach, move, turn and apply pressure, grasp, position, release, disengage, eye travel time and eye focus, body, leg and foot motions, simultaneous motions
body, leg and foot motions, simultaneous motions
• Sum the TMU values (consider only limiting values)
• Add allowances
Add allowances
– The tabulated values do not carry any allowances – Some analysts state that no fatigue allowance is needed
END 202 – Work analysis and design
Time Study
Methods‐time measurement (MTM‐2)
• The
The data are adapted to the operator and are data are adapted to the operator and are
independent of the workplace or equipment
Used in work assignments where
• Used in work assignments where
– The effort portion of the work cycle is more than 1 min
– The cycle is not highly repetitive
y
g y p
– Does not involve a large number of either complex or simultaneous hand motions
• In addition to basic MTM motions, there are combinations of them – GET: reach + grasp + release
– PUT: move + position + release
END 202 – Work analysis and design
Time Study
Methods‐time measurement (MTM‐2)
END 202 – Work analysis and design
Time Study
Methods‐time measurement (MTM‐2)
11 classes of actions (categories)
(
g
)
• Get (reach‐grasp‐release)
• Put (move‐position)
• Get Weight
h
• Put Weight
• Regrasp
• Apply Pressure
• Eye Action
y
• Foot Action
• Step
• Bend and Arise
B d dA i
• Crank
END 202 – Work analysis and design
Time Study
Methods‐time measurement (MTM‐2)
Cases for GET(G)
Cases for GET(G)
END 202 – Work analysis and design
Cases for PUT(P)
Cases for PUT(P)
Time Study
Methods‐time measurement (MTM‐2)
• Principle of Simultaneous Motion: If two hands make the same task simultaneously, more time can be assigned depending on the difficulty
Principle of Limiting Motion: If two hands make
• Principle of Limiting Motion: If two hands make different tasks at the same time, we consider the slowest one
slowest one
• Principle of Combined Motion: If one hand makes two distinct movements we take the slowest
two distinct movements, we take the slowest time
END 202 – Work analysis and design
Time Study
Methods‐time measurement (MTM‐?)
• MTM‐3: helpful for works where there is an interest in p
saving time at the expense of some accuracy
• MTM‐V: for use in metal cutting operations, to establish set p times for all t pical machine tools
establish setup times for all typical machine tools
• MTM‐C: widely used in banking and insurance industries, for work tasks such as filing, data entry, and
industries, for work tasks such as filing, data entry, and keyboarding
• MTM‐M: for operator working on a microscope, microminiature
i
i i t
manufacturing
f t i
• MTM‐TE: for electronic tests
• MTM‐MEK: one‐of‐a‐kind and small‐lot production
MTM MEK: one of a kind and small lot production
• MTM‐UAS: for a process description, batch production
END 202 – Work analysis and design
Time Study
Maynard Operations Sequence Technique (MOST)
• Developed
Developed by Zandin
by Zandin in 1967, applied in in 1967 applied in
Sweden
• Simpler than MTM, but faster than MTM
Simpler than MTM but faster than MTM‐1
1 and and
MTM‐2 (at least 5 times faster than MTM‐1)
• There are three levels:
There are three levels:
– MaxiMOST: analyzes long, infrequent operations (range from 2 min to several hours and occur less
(range from 2 min to several hours and occur less than 150 times per week)
– MiniMOST: very short and very frequent (less than 1.6 min in length, more than 1500 times a week)
– BasicMOST: 0.5 min to 3 min of length
END 202 – Work analysis and design
Time Study
Predetermined time systems
END 202 – Work analysis and design
Time Study
Time study
Methods to determine time standards:
• Estimation
• Historical records
• Time study techniques:
– Direct time study (with chronometer)
y(
)
– Standard data and formulas
– Predetermined time systems
Predetermined time systems
– Work sampling
END 202 – Work analysis and design
Time Study
Engineered standards