Time Study

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Time Study

• IENG 311
• Work Methods
• Carter J. Kerk, PhD, PE, CSP, CPE

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Time Study

• Read Chapter 27 and 28 from Konz Johnson, 6th
  Edition
• Homework, Due Wednesday, September 20th
  (beginning of class)
• Review Questions
• Chapter 27 p. 545
• Chapter 28 p. 559

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Why Conduct Time Studies?

• You cant manage what you dont measure
• Cost Allocation
• Production Inventory Control
• Evaluation of Alternatives
• Acceptable Days Work
• Incentive Pay

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Normal Pace

• Walk at ? mph, Deal deck in ? Seconds
• Normal Curve (see next slide)
• Think about use for
• Incentives
• Dismissal

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Discipline Procedure (Example)
Step Description
0 Normal operator, acceptable performance
1 Oral warning
2 Oral warning detailed review of method with supervisor
3 Written warning additional training
4 Written warning some loss of pay
5 Written warning larger loss of pay
6 Discharge from job
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Establishing Time Standards

• Nonengineered (Type 2) Estimates
• Quick and dirty, low cost
• Mostly subjective
• Very little objective
• Examples
• Historical Records
• Ask an expert
• Time Logs
• Occurrence (or Work) Sampling (see Chapter 10)

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Establishing Time Standards

• Engineered (Type I) Estimates
• More accurate than non-engineered (Type II)
• Preceded by a methods and quality analysis
• Mostly objective, very little subjective
  characteristics

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Implementing Type I Standards

1. Select a logical organizational unit and plan to
   set standards for all touch labor in the unit
2. Orient supervisors and workers
3. Improve the work methods
4. Determine the time (TS or Standard Data)
5. Calculate standards, including allowances
6. Check and debug standards implement for a trial
   basis (1 month)
7. Go to full implementation, including discipline

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Implementing Type I Standards

• Also see MIL-STD-1567A on course website. This
  addresses Work Measurement

MIL-STD-1567A 3/11/1983 Original Release
MIL-STD-1567A Notice 1 5/3/1986 Update
MIL-STD-1567A Notice 2 1/3-/1987 Update
MIL-STD-1567A Notice 3 2/27/1995 Cancelled
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Time Study

• Observed Time (OT)
• the raw unadjusted time a worker takes
• Normal Time (NT)
• The time an experience worker should take
• NT (OT) (Rating)
• Standard Time (ST)
• NT increased to account for allowances (personal,
  fatigue, and delays)

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Standard Data

• Future topic for Chapters 29 and 30
• Predetermined Time Systems
• MTM, MOST, etc.
• Statistical Approach
• Advantage of Standard Data over Time Study
• Cheaper
• Consistency
• Faster

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Allowances

• Normal time is increased by three types of
  allowances
• Personal
• Fatigue
• Delay
• Shift Allowances or Work Allowances?
• Its a policy decision
• Shift Allowances (a percent of shift time)
• ST NT / (1 Allowances)
• Work Allowances (a percent of work time)
• ST NT ( 1 Allowances)

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Personal Allowances

• Given for activities such as blowing your nose,
  visits to the restroom, getting a drink of water,
  smoking, etc.
• Typically 5
• May or may not be considered part of the 15
  minute break at mid-morning and mid-afternoon
  and the 30 minute lunch

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Fatigue Allowances

• Given to compensate a worker for time lost due to
  fatigue
• Given only if fatigue is actually a possibility
• Physical Fatigue Table 27.6 27.8
• Mental Fatigue Table 27.9 27.10
• Environmental Fatigue Table 27.11 27.14
• Points do NOT equal percentages
• See Table 27.4 for summation

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Physical Fatigue
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Physical Fatigue
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Physical Fatigue
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Mental Fatigue
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Mental Fatigue
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Environmental Fatigue
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Environmental Fatigue
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Environmental Fatigue
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Environmental Fatigue
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Delay Allowances

• These compensate for machine breakdowns,
  interrupted material flow, conversations with
  supervisors, machine maintenance, cleaning, etc.
• Record delays during a long sampling period using
  time study or work sampling (occurrence sampling)
  and calculate the percent of time in delay.

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Learning

• The amount of time to complete a task improves
  with practice
• This is a natural process that has proven to be
  predictable statistically
• Learning components cognitive and motor learning
• Studied by Wright (1936)
• Cycle Time a(cum of cycles)b
• Plotted on log-log is a straight line
• See Figures 27.4 27.6

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Learning Curve
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Learning Curve
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Learning Curve
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Learning, Continued

• Variable a is the time to complete the first
  cycle
• Variable b is dependent on the rate of
  learning, either calculate or look up in Table
  27.15
• Improvement between doubled quantities is
  consistent

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95 Learning Curve Example
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Typical Values for Learning

• Cognitive learning has greater improvement (70
  curve), while motor learning is slower (90
  curve)
• 98.5 Grinding
• 90 Bench Inspection
• 84 Cigar Making
• 80 Keyboard Entry
• 68 Truck Body Assembly

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Timing Techniques

• Stopwatch
• Snapback
• Continuous
• Videotape
• With burned-in timer to at least 0.00 sec
• Many advantages to videotape
• Permanent, can be viewed many times, freeze
  frame, frame by frame advance, slow motion,
  shuttle speed, forward and backward, use with
  stopwatch, pace rating, training

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Number of Observations

• There are two approaches to determining the
  number of observations
• Statistical
• Importance of Decision
• Applying some common sense/practicality

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Statistical Determination of Number of
Observations

• Goal Trying to estimate the population mean
  from the sample mean
• Sample means are not precise
• To improve precision, you can increase the sample
  size, but this increases the cost of sampling

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Statistical Determination of Sample Size

• The number of observations to record depends on
• Accuracy desired
• Confidence desired
• Data variability
• Due to operation variation

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Accuracy Desired

• Relative or Absolute Terms
• Case 1 0.2 hour element (12 min)
• /- 5 relative accuracy is the same as an
  absolute accuracy of .2(.05) 0.01 h for a range
  of 0.19 to 0.21 hours. The target width is 0.02
  hours
• Case 2 0.02 hour element (1.2 min 72 s)
• /- 5 relative accuracy is the same as an
  absolute accuracy of .02(.05) 0.001 h for a
  range of 0.019 to 0.021
• Both have a /- 5 relative accuracy, but the
  absolute accuracy is 10 times different!

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Accuracy Desired

• The size of the target determines the number of
  shots needed to hit it.
• It is more difficult to hit a smaller target, so
  more shots are needed, or a larger sample size.
• People are often not precise in their statements.
  They may say 5 accuracy, without specifying
  whether it is absolute or relative.

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Confidence Required

• For 90 confidence, you want shots to hit the
  target 90 of the time.
• With 90 confidence with /- 5 accuracy for a
  0.02 h element, means that if there were 100
  different time studies, in 90 of the studies, the
  time study mean would be between 0.019 and 0.021
  h.

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Estimating Number of Observations

• Statistical Formulas
• See Box 28.1
• See Ergo Disk
• See IENG 381/382
• Importance of Decision (Estimating)
• See next two tables

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Workplace Terminology

• Assembly Line
• Job Shop
• Flexible Workstation
• Work Cell
• Warehouse
• Receiving
• Shipping

• Order Fulfillment
• Kitting