Chapter 28 STOPWATCH TIME STUDY

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Chapter 28 STOPWATCH TIME STUDY
Stopwatch Time study should be preceded by a
methods analysis so the resulting standard is
ashould take time not a did take time.
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OVERVIEW
Stopwatch time study is one of the two methods
to establish a type I time standard.
The analyst observes one or more operators
continuously and records the time taken to
accomplish a task. This is called Observed
Time Observed Time x Rating Normal Time
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OVERVIEW
Standard time (Normal time) (100/100 pct
Allowances)
Example Observed time .01 hr./unit Rating
120 Normal time .012 hr./unit Allowances
10 Standard time (.012 hr./unit 100/90)
.0133hr./unit
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Time Study Sheets (from ERGO)
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PREPARATION

• There are basically two steps involved in
  Preparation
• 1. Methods Analysis
• 2. Operator Selection

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METHODS ANALYSIS

• From a productivity standpoint, supervisors of
  industrial engineering department have to do job
  design.
• The primary reason for doing a methods analysis
  before doing a time study is to establish a safe,
  productive job.
• The secondary reason is to leave a permanent
  record of the methods for future audits and
  improvements.

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METHODS ANALYSIS
The typical items that are recorded are Date
of observation(Improvement curve) Person observed
(Skilled..) Person observing (Viewpoint) Machine
used (Improvement curve) Tools used (Improvement
curve) Part no. processed etc..
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METHODS ANALYSIS

• After a good method has been established (using
  checklists), the job should be broken into
  Elements

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METHODS ANALYSIS

• Five Reasons to divide the tasks into elements
• Elements make it possible to reuse the data
• Elements permit different ratings for different
  elements(Machine time and manual time)
• Elements permit consistency checks, within the
  study and between studies
• Elements improve methods descriptions
• Data collection is flexible

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METHODS ANALYSIS

• After the task is broken into elements, we write
  the element description on the time study form
  with a description of its EP (End points ) or
  also called TP (Termination point)
• (Example)

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OPERATOR SELECTION

• It is very important to select the right operator
  for performing the time study
• There are two reasons
• Rating Accuracy(average worker)
• Worker Acceptance( do the study at different
  times)

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TIMING

• Timing Techniques (example)
• Videotape
• One watch, continuous
• One watch, snapback
• Three watch system
• Electronic watches

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TIMING

• Videotape
• The primary advantage is having a permanent
  record of the method.
• Videotaping is less intrusive so there might not
  be any discrepancies.
• The tape counter does not give very accurate data
  as it gives continuous timing use a stopwatch.
• The elements can also be performance rated
• If any dispute occurs then the tape can also be
  replayed

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TIMING

• One watch, continuous
• The stop watch does not stop, it is continuously
  run (Example)
• As the clock never stops, there is no time
  omitted and workers like that
• The disadvantage is that the observer does not
  know how individual elements vary and the
  observer tries to read a moving target.

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TIMING

• One watch, Snapback
• As the element ends, the time is noted and the
  stop is reset (set back to zero).
• The advantage is that no subtraction to be done
  and the observer is able to see the pattern.
• If the observer is confused then he might stop
  the watch.
• Continuous is preferred over snapback.

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TIMING
Three-watch system As in the title there are
three watches and it is a combination of snap
back and continuous type Initially the hands of
the first watch are moving, the seconds are
stopped at some value, and the thirds are
stopped at zero. The only disadvantage is that
there are three watches.
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TIMING

• Electronic watches
• These watches can be used either the snapback
• or the continuos mode
• The key feature is that, when the user depresses
  the
• button, the display time is frozen while the
  clock
• continues timing.
• Electronic watches with a computer built into the
• board, generally have replaced the traditional
• mechanical stop watch.

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NUMBER OF OBSERVATIONS

• There are two approaches to determining the
  number of observations
• Statistical
• Importance of Decision

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NUMBER OF OBSERVATIONS
Statistical A time study of sequential
observations is a sample from a population of
times. The goal is to estimate the population
mean from the sample mean. To minimize the
differences between the sample and population
means, increasing the sample size is one of the
answers.




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• The number of sample size depends on three
  factors
• Accuracy Desired (absolute or relative)
• Confidence Desired (based on Z score)
• Data Variability (use subsample to determine)
• Calculation formula (See Box 28.1)
• -Westinghouse/ General Electric and Niebels
• approaches are in Tables 28.2 and 28.3

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NUMBER OF OBSERVATIONS

• Irregular and Foreign Observations
• Irregular element (exp. Breakdown)
• Foreign element (exp. Customized part)

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NUMBER OF OBSERVATIONS

• Recording Techniques
• Missed Readings
• Omitted Readings
• Element out of order
• Unexpected element

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RATING
Normal Pace During the time study, the observer
will rate the worker, that is, determine the
adjustment to convert the observed time to a time
that a normal, experienced worker would take
APL MPL - Expectancy
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RATING
MPL (Motivated productivity level) The work
pace of a motivated worker possessing sufficient
skill and effort to do the job, physically fit to
do the job after adjustment to it, and working at
an incentive pace that can be maintained day
after day without harmful effect.
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RATING
Acceptable productivity level (APL) The work
pace established by management or jointly by
management and labor at a level that is
considered satisfactory it is established at a
given relationship to motivated productivity
level. Expectancy is the expected level of
productivity, it is also related to allowance, if
allowance is low expectancy discount tends to be
high and vice-versa.
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RATING TECHNIQUES

• There cannot be a set method to rate as different
  tasks within an activity requires different
  levels of skills and ways
• All tasks cannot be rated at a same scale
• (example)

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RATING TECHNIQUES

• Pace Rating
• The observer estimates the speed and concentrate
  on dynamic micromotions such as reach or move
  rather then stationary like position and grasp.
• Objective Rating (three steps) (example)
• The observer rates the speed
• Observer estimates the task difficulty
• task difficulty factor is multiplied with speed
  to get actual pace.

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RATING PROCEDURES

• Divide the elements and take multiple readings
• Categorize mental, fine manipulative and muscular
  jobs
• Categorize skilled, unskilled and semi skilled
  labor
• Categorize time of the day
• Rating is a very specialized task and enough
  training via videotapes, practice tests,
  different paces etc should be carried out before
  actual assignment

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RATING TECHNIQUES
120 100 80 60 40 20 0
Estimated Pace
Cte Error
Flat Rating
Consistency
Identity Line
0 20 40 60 80 100 120
140
Actual pace