Why do we break down the activity to be studied into elements?(why not measure time straightly)
To provide a detailed work specification
To separate value adding & non-value adding activities
To select best method by comparing work elements of different methods
Stopwatch – one revolution = 1 minute (1 deciminute = 1/100th of minute)
Normal time = Observed time * rating factor
Standard time = Normal time + allowances
Rating – Comparing the pace rate or performance of a worker against standard performance level
to take into account different operators’ performance level
Rating techniques-
Speed- Worker’s speed/speed expected
However assigning a rating factor and allowances are largely subjective in nature and depends on personal judgment of timestudy engineer
Allowances- it is the additional time provided over and above normal time to take into account time for relaxation, attending personal needs
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Rest and personal allowances (to overcome fatigue incurred during working)
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Interference allowances (to take into account m/c stoppages etc)
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Special allowances (for activities which are generally not a part of work cycle)
Indirect (Without actually measuring)
In this we build up the total time for a job by summing up the times for different elements
Particularly useful for operations which are still in the planning phase and have not yet started (helpful in planning and scheduling)
Synthesis
Element time values are taken from a catalogue of elements time built from timestudies done in the past
PMTS also make use of previously collected data but it deals with basic human motions (or therbligs) of duration 0.1 seconds or less. Whereas in synthesis duration may be 3-4 seconds
Analytical estimating is used when past time data is not available and estimator has to rely on his past experience.
PMTS
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For short cycle & highly repetitive jobs
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Uses video film (micromotion study)
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More accurate than stopwatch timestudies
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No rating factor required but allowances need to be added
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But can deal with only manual motions of the operation
Method Time Measurement
Work Factor Systems
1 TMU = 0.0006 minutes (TMU = Time Measurement Unit)
1 wink = 0.0005 minutes (used in SIMO chart/micromotion study)
Analytical Estimating
For long and non-repetitive operations ; Least accurate
(Machine elements – calculated from information of feed, speed, depth of cut etc)
Comparison
It is difficult to compare different work measurement techniques, as each technique has its own set of application
Work sampling is used for long cycles eg amount of time actually spent working by a worker in a shift
Time study is used for short repetitive cycles eg worker working on a assembly line
PMTS is used for very short cycles which require a very detail analysis (micromotion study)
Time
study
Work sampling
Synthetic time
P.M.T.S.
Analytical
estimating
Time Required
MAX
MIN
Accuracy
MAX
MIN