Transcript Slide 1

4. Time Study
The major objective of this chapter is to
learn how to calculate a time standard
based on stopwatch time study
procedures.
TI 2111 Work System Design and Ergonomics
Time Study


A process for measuring the required time for
performing a given task, by a given method,
by a trained worker, working in a normal
pace.
Why needed?

For methods improvement

For determining time standards
TI 2111 Work System Design and Ergonomics
Needs for Time Standard






Developing schedules
Determining wage payment plans
Estimating production costs
Providing a base for estimating productivity
goals
Appraising employee performance
Evaluating alternative process, equipment
TI 2111 Work System Design and Ergonomics
Methods for Creating Time Standards

Direct time study




Cyclic work
Non cyclic work
Work sampling
Synthetic data

Predetermined times
TI 2111 Work System Design and Ergonomics
Direct Time Study - Tools
TI 2111 Work System Design and Ergonomics
Direct Time Study





Methods improvement
Selection of the examined workers
Explanation (union, managers, workers)
Collecting and recording information
Task division into elements
TI 2111 Work System Design and Ergonomics
Methodology

Who to choose?



Select an Average Worker (What is average?)
Experienced operator
Normal pace






Consistency (well defined, understood by all)
No undue strain for entire day (speed/effort)
Pace that should be performed, not average of current rate
Rating accuracy
Worker acceptance
Can you suggest a better method?
TI 2111 Work System Design and Ergonomics
Preparation for Timing




Identify the TASK/ CYCLE to be studied before time study
Analyze the Complete Task
 Method
 Layout of workplace
 Equipment used
 Environmental conditions
 Machine speeds and feeds
 Inspection equipment
Communications with foreman, workers
 Documents for process, task instructions
 Establish relationship
Elemental analysis
 Break task into elements
TI 2111 Work System Design and Ergonomics
Fundamental definitions

What is an ELEMENT?


Element is a component of job or task that
are logical divisions with easily identifiable
starting and end points, and are repeated
on a regular basis
What is a CYCLE?

Cycle is the completion of the activities
(elements) required to perform the job
under study.
TI 2111 Work System Design and Ergonomics
Element Analysis




Every element must have an easily
identifiable starting and ending point
(breakpoints)
No discontinuities between elements
Elements times: 0.04min (short), 0.25min
(reasonable)
Relative frequency must be included
TI 2111 Work System Design and Ergonomics
Timing Methods

Continuous



Advantage: Clock never stops, no time omitted
Disadvantage: observer does not know at the job
how individual elements vary
Snapback


Advantage: Observer can note individual
variability within an element and eliminate
substraction
Disadvantages: difficult to coordinate eye, watch
and task! Especially when operations are short
TI 2111 Work System Design and Ergonomics
Determining Number of Cycles
Time measurement


Measuring time of
each element
The number of
observation of each
element depends on
the significance level
and required level of
accuracy
Primary time study
(normally 5 to 10
observation)
Examination of the
required number of
observations (N)
Continue study up to N
observations
Re-checking the required
number of observations (n)
N=n
No
N>=n
Yes
End the time study
TI 2111 Work System Design and Ergonomics
Recommended number of
cycles/observations
TI 2111 Work System Design and Ergonomics
Maytag Company Approach
TI 2111 Work System Design and Ergonomics
TI 2111 Work System Design and Ergonomics
Rules for Performing Time Study





Don’t comment to the worker during the task
Stand (don’t sit) beside the worker
Write every event (even though it may seems not
important)
Have a good position to observe
Stop the study if the worker seems to be under
pressure and it affects his/her work
TI 2111 Work System Design and Ergonomics
Time Study On Cyclic Work




Rating evaluation may be written once in a
couple of cycles
Elements times: 0.04min (short), 0.25min
(reasonable)
Denoting non-cyclic elements
The breakpoint between elements should be
clear (touch, push, etc.).
TI 2111 Work System Design and Ergonomics
Types of Elements




Manual/machine (determines the task
duration)
Cyclic/non cyclic
Fixed time/ variable time (i.e. loading time as
a function of weight)
Avoidable/unavoidable unproductive
elements (sometimes hard to identify)
TI 2111 Work System Design and Ergonomics
Time Study on Non Cyclic Work




Use continuous timing
Divide the task into relatively large elements
Write the evaluated performance rate at the
end of each element
Multiply the observed time with the rate and
summarize the data
TI 2111 Work System Design and Ergonomics
RATING FACTORS
TI 2111 Work System Design and Ergonomics
Do we expect the average worker to
work in normal rating ?
TI 2111 Work System Design and Ergonomics
Rating Evaluation Methods




Subjective judgment
Practice by watching movies
For a study with long elements, rate each
separately
Methods:


Speed rating
Westinghouse
TI 2111 Work System Design and Ergonomics
Performance Rating Table (Westinghouse)
TI 2111 Work System Design and Ergonomics
Criteria for Successful Speed
Rating Evaluation



Experience in the class of work performed
Selection of an operator who gives
performances between 85 and 115
Use of the average value of three or more
independent studies
TI 2111 Work System Design and Ergonomics
Elements of Allowances
Personal
Need
Basic
Fatigue
Variable
Fatigue
Unavoidable
Delays
Constant
Allowances
Avoidable
Delays
Extra
Allowances
Special Allowances
Total Allowances Allowances
+
Normal
Time
=
Standard
Time
TI 2111 Work System Design and Ergonomics
Standard Data Systems
Elemental times, based on previous time
studies, which have been proven to be
accurate and reliable.
Tabulated element standards that allow the
measurement of a specific job without the
use of timing devices.
TI 2111 Work System Design and Ergonomics
Construction Cost Estimating
Given we have the plans for a
new building, how much labor is
needed and what will it be used
for?
TI 2111 Work System Design and Ergonomics
Punch Press Standard Data
(40” strip)
Given we have a new part to run
through the punch press, what
will be the standard time for
the part?
TI 2111 Work System Design and Ergonomics
Advantages Over Direct Time Study





More consistent standards results
Duplicate time studies on similar operations
are eliminated
Standards are established more rapidly
Less experienced analysts can calculate
standards (use the formula not develop it)
Accurate labor costs and production times
can be estimated before production begins
TI 2111 Work System Design and Ergonomics
To Illustrate the development of
standard data…
Model
Element 119
130
220
310
311
322
329
10
0.24
0.22
0.23
0.23
0.24
0.22
0.23
20
0.38
0.35
0.35
0.37
0.36
0.36
0.37
30
12.06
10.44
8.71
6.58
10.83
6.34
7.25
40
3.66
4.81
0.00
2.79
5.84
4.55
4.10
50
0.00
1.63
1.91
1.69
1.80
1.45
0.00
60
0.12
0.12
0.13
0.11
0.14
0.14
0.13
TI 2111 Work System Design and Ergonomics
Possible Drivers
D1
D2
119
15.72
18.00
27.25
130
16.88
23.50
33.50
220
10.62
2.50
1.50
310
11.06
3.00
7.25
311
18.47
25.00
44.00
322
12.34
12.00
18.25
329
11.35
3.00
8.00
20.00
Time 30/40/50 (Hrs/1000)
Model NT 3/4/5
18.00
16.00
14.00
12.00
D1
10.00
D2
8.00
6.00
4.00
2.00
0.00
0.00
10.00
20.00
30.00
40.00
50.00
Dimensions (D1 and D2 - inches)
TI 2111 Work System Design and Ergonomics
Correlation
n X1 X 2   X1  X 2 
r
2 
2
2
n X 2 
X1
n  X2   X2


1

 


 


 

TI 2111 Work System Design and Ergonomics
Is there a relationship between D1 and the
combined time for elements 30, 40, and
50?n
X1
X2
X1^2
X2^2
X1*X2
1
15.72
18.00
247.1184
324.00
282.96
2
16.88
23.50
284.9344
552.25
396.68
3
10.62
2.50
112.7844
6.25
26.55
4
11.06
3.00
122.3236
9.00
33.18
5
18.47
25.00
341.1409
625.00
461.75
6
12.34
12.00
152.2756
144.00
148.08
7
11.35
3.00
128.8225
9.00
34.05
Sums
96.44
87.00
1389.3998
1669.50
1383.25
r =
0.977
TI 2111 Work System Design and Ergonomics
Linear Regression
Y
Y = b 0 + b 1X
X
2

X  Y    X  XY 

b0 
2
n X 2    X 
b1 
n XY    X  Y 


n  X 2   X 
2
TI 2111 Work System Design and Ergonomics
Standard Times for Machining Operations

How long will it take
to drill a 1-inch hole
through two inches
of malleable cast
iron?
TI 2111 Work System Design and Ergonomics