Work Measurement

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Work Measurement

• Establishing the time taken by a worker to carry
  out a specified job a a defined level of
  performance

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Purpose of Work Measurement

• To reduce the amount of ineffective time
• Provides management with a means of identifying
  the causes of ineffective time

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Uses of Work Measurment

• To compare the efficiency of alternative work
  methods
• To balance the work of members of teams
• To determine the number of machines an operative
  can run

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Work Standards

• A work standard is the time required for a
  trained worker to perform a task with normal
  effort and skills

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Uses of Work Standards

• Capacity planning
• Scheduling
• Costing
• Performance appraisal
• Motivating workers with incentives

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Areas of Controversy

• Conflict between management and workers
• Workers think standards too high
• Management think standards too low
• Conflicts expensive
• Need achievable standards for costing, scheduling
  etc.
• Time studies dehumanising
• Industrial Engineering departments expensive
• Using work standards for piecework incentives
  reduces incentive to improve work methods
• Trade off with quality

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Work Measurement Techniques

• Time study
• Activity sampling
• Predetermined motion time systems
• Synthesis from standard data
• Estimating
• Analytical estimating
• Comparative estimating

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Time Study

• Select work elements
• Timing the elements
• Determine sample time
• Setting the work standard

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Selecting Work Elements

• Obvious starting and stopping points
• Long enough to accurately time
• Should have been running smoothly for a period of
  time in a standard work environment
• Separate incidental operations from the
  repetetive work

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Timing Work Elements

• Stopwatch
• Investigate single sample times that differ
  greatly from other timings for the same element.
  Dont include irregular occurencies, use
  allowances.

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Determining Sample Size

• We are trying to estimate the average of the true
  time distribution to a certain precision with a
  particular confidence
• Do a set of initial samples
• Use

n required sample size p precision of
estimate as a proportion of true value t mean
time from sample (the select time) ? standard
deviation of sample times z number of standard
deviations for desired confidence
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Time Study Method
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Step 1 Selecting Work Elements
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Step 3 Determining the Sample Size
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Step 3 Determining the Sample Size
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Desired Confidence () z 90 1.65 95 1.96 96
2.05 97 2.17 98 2.33 99 2.58
Step 3 Determining the Sample Size
n ( )( )
1.96 ? 0.04 t
2
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Setting the Work Standard

• Need to judge the pace of the worker to produce a
  rating factor (RF).
• RF lt 1 means worker going slower than standard
• RF gt 1 means worker going faster than standard
• Allowances
• Contingency Allowance. For legitimate and
  expected work or delays which are uneconomic to
  measure
• Relaxation Allowance. To allow for physiological
  or psychological effects of conditions eg.
• 5-7 Personal
• 0-10 Energy Output
• 0-5 Noisy
• 0-100 Conditions

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Setting the Work Standard

• Basic time (BT) in Basic Minutes (BM) is
• Observed Time Rating Factor
• Basic Time for Cycle (BTC) is
• ? BT
• Standard time is
• BTC Allowances

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Step 4 Setting the Standard
(after 48 additional observations)
Work Element t RF BT 1. Get
carton 0.26 1.05 2. Put liner in
carton 0.10 0.95 3. Place cups in
carton 0.75 1.10 4. Seal carton and set
aside 1.08 0.90
BT 0.26 1.05
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Activity Sampling

• A large number of instantaneous observations made
  over a length of time
• Percentage of observations in which an activity
  is taking place approximates proportion of total
  time that activity takes place

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Activity Sampling

• Advantages
• Can measure activities which are too impractical
  or costly to measure by time study
• Only needs one observer
• Sampling can be interrupted
• Disadvantages
• Quicker and easier to use Work Study on jobs of
  short duration
• Does not provide elemental detail

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Number of Samples
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Number of Samples
n required sample size p estimate of
proportion time an activity takes place z
number of standard deviations for desired
confidence e maximum error allowable
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Predetermined Motion Time System

• Use established timings for basic human movements
  to build up time for job
• Potentially accurate
• Can be used before production in place
• Performance ratings may not be required
• Time consuming
• Cant use for low repeatability jobs
• Different part shapes

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Predetermined Motion Time System
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Predetermined Motion Time System
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Predetermined Motion Time System
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Predetermined Motion Time System
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Synthesis

• Build up job times from previous element times
  from studies on other jobs
• Useful where new jobs made up of well understood
  elements

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Estimating

• Estimate made by person familiar with job
• Least accurate of all methods