TI 2111 Work System Design and Ergonomics 4. Time Study The major objective of this chapter is to...
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Transcript of TI 2111 Work System Design and Ergonomics 4. Time Study The major objective of this chapter is to...
TI 2111 Work System Design and Ergonomics
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
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 CyclesTime 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 therequired number of
observations (N)
Continue study up to Nobservations
Re-checking the requirednumber of observations (n)
N>=n
End the time study
N=n
No
Yes
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
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
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
Normal Time
Extra Allowances
Unavoidable Delays
Special AllowancesConstant Allowances
Basic Fatigue
Personal Need
Variable Fatigue
Avoidable Delays
Standard Time
Total Allowances Allowances + =
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
Element119 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
Model NT 3/4/5 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
0.00
2.00
4.00
6.00
8.00
10.00
12.00
14.00
16.00
18.00
20.00
0.00 10.00 20.00 30.00 40.00 50.00
Dimensions (D1 and D2 - inches)
Tim
e 30
/40/
50 (
Hrs
/100
0)
D1
D2
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 = b0 + b1XY
X
221
22
2
0
XXn
YXXYnb
XXn
XYXYXb