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Problem Solving Tools for Methods Engineering


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Title: Problem Solving Tools for Methods Engineering

Chapter 2
  • Problem Solving Tools for Methods Engineering

Our Text Book Website
  • http//

Outline for today
  • A short history of Human Factors and Ergonomics,
  • Methods Engineering/Work Design
  • Example of Methods Engineering
  • Discussion of in-class exercise,
  • Approaches for both physical and thinking

A Short History of Human Factors and Ergonomics
Year Event
1760 Perronet makes time studies
1820 Charles W. Babbage makes time studies
1832 Charles W. Babbage publishes On the Economy of Machinery and Manufactures
1881 Frederick W. Taylor begins his time study work
1901 Gantt develops the task and bonus wage system
1910 Gilbreth publishes Motion Study
1933 First Ph.D. granted in the United State in the field of industrial engineering from Cornell University
1949 The Ergonomics Research Society (The Ergonomics Society) founded United Kingdom
1957 The Human Factors and Ergonomics Society is founded United States
1970 Congress passes the OSHAct, Occupational Safety and Health Administration
1981 NIOSH lifting guidelines are first introduced
1990 Americans with Disabiities Act (ADA) is passed by Congress
1995 ANSI Z-365 Standard for Control of Work-Related Cumulative Trauma Disorders
2006 50th Anniversary of the Human Factors and Ergonomics Society
Methods Engineering
  • Technique for
  • Increasing production per unit of time.
  • Example increasing the number of customers
    that can be handled per cashier by installing bar
    code readers.
  • Decreasing cost per unit output.
  • Example decreasing total cost of each cell
    phone by reducing the number of parts and thus
    the labor hours required for assembly.
  • It is critical to look at impact on whole system.

Methods Engineering Focuses Primarily on
improving productivity though (re)design of
Motivation Incentives/rewards
Organizational structure
Work Process
Work operations
Tools (Products)
Work environment
Methods Engineering
  • Often used synonymously with
  • Corporate re-engineering
  • Work design
  • Operation analysis
  • The difference between these terms in the level
    of detail.

Big picture level
Detail level
Methods Engineering
  • Select project
  • I.D. product or service experiencing
  • Get and present data
  • Study situation, take measurements to
    determine where difficulties really lie,
  • Analyze the data
  • Figure out which of many problems are most
  • Develop ideal method(s)
  • Identify alternative approaches which may
    address most critical problems.
  • Present and install method
  • at the work site
  • Develop a job analysis
  • To insure operators are adequately selected,
    trained, rewarded, etc.
  • Establish time standards
  • Establish fair and equitable standards for
    work performance.
  • Follow up the method
  • Take measurements to determine if changes
    really did improve situation as predicted.

Example Mission Planning and control for the
Mars Exploration Rover
  • Researchers introduced automated planning tool,
  • Tool had to fit with users existing way of
    thinking about plans,
  • Introduction of new tools caused the planning
    process to change,
  • Product and processes were evolved together, over

Many methods can be used in many stages of the
design process
A typical spiral design process
Prototype Testing
Requirements Gathering
Final Performance Evaluation or Comparison
Design Specification
Design Review
Problem Solving Tools for Methods Engineering
help to identify what the most important problem
  • Observational tools
  • Site walk-thrus
  • Observation and interviews of workers and
  • Ethnographic studies

Problem Solving Tools for Methods Engineering
(Ch. 2.1)
  • Exploratory tools
  • Pareto Analysis (Vilfredo Pareto)
  • Fish Diagrams (from Japan, 60s)
  • Gantt and PERT charts (40s wartime).

Pareto Analysis
  • Items of interest are identified (e.g. types of
    product flaws that result in scrapped parts, time
    spent on each activity required to manufacture a
    product or perform a service.
  • Items are measured on a common scale (such as
    frequency total cost, total time, etc.)
  • Items are ordered in descending order

Example of a Pareto Chart
Example 2 Pareto chart worker time study
Example of a Fish Diagram
Fish Diagrams
  • Cause and effect diagrams
  • Effect is a problem fish head
  • Causes fish bones
  • Typical causes
  • Environment
  • Methods
  • Materials
  • Administrative
  • Machine
  • Human

Gantt Charts
  • Activities shown as bars with
  • Anticipated start times
  • Anticipated completion times
  • Actual start and completion times
  • Use a vertical line to show current time
  • May use color codes to show various things
  • Completed activities (grey)
  • On going activities, on schedule (green)
  • Overdue activities (red)
  • Almost over due activities (yellow)

Example of a GANTT chart
PERT Charts Program Review and Evaluation
  • Project networks
  • Like Gannt charts, PERT charts show activities,
    start and end times
  • Also show variation in activity durations
    optimistic, average, pessimistic,
  • Show dependencies between activities,
  • Can identify a critical path (longest path) that
    constrains minimum completion time of whole
  • Analyze how crashing activities can shorten
    duration of whole project.

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Example of a PERT chart
Problem Solving Tools (cont.)
  • Recording and Analysis tools
  • Operation Process Chart
  • Flow process chart
  • Flow diagram
  • Worker and Machine Process Charts
  • Gang Process charts
  • Synchronous servicing

Operation Process Charts
  • Chronological sequence of operations
  • Show operations as a flow chart though the
  • Show the types of operations
  • Operation
  • Transport
  • Inspection
  • Delay
  • Storage
  • Decision

Operation Process Chart Manufacture of a
telephone stand
Flow Process Chart
  • More detail than Operation Process Chart
  • Not usually used for entire assemblies,
  • Used for just one component (or operator)
  • Add in information on
  • Operation duration (time to complete)
  • Distance traveled (for transport operations)
  • Good for showing savings of a new method.

Flow Process Chart Preparation of direct mail
Flow Diagram
  • Show layout of work area
  • Show the flow of work through that area
  • Show congestion areas, crossing worker paths,
    total travel.
  • Identify how layout can be redesigned to reduce
    travel, motion, collisions, etc.
  • Store materials near where they are used.
  • Increase efficiency and safety.

Flow diagram
A revised and more efficient flow diagram
Worker and Machine Process Chart
  • Show one worker, many processes
  • Identify idle time for each,
  • Reorganize operations to reduce idle time.
  • Identify how many machines worker can manage

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Gang Process Charts
  • Show one machine, many workers,
  • Identify idle time for each,
  • Re-arrange tasks between workers to reduce idle

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Synchronous and Random Servicing
  • Synchronous servicing operations (usually done
    by machine) take a predictable amount of time, so
    the operator(s) servicing actions can be
    synchronized with the machines cycle times.
  • Random servicing (Asynchronous) operation
    occurrences happen with some unpredictability
    e.g. machine breakages, field service calls, etc.

Synchronous Servicing
n l m l w
  • The number of
  • Machines an operator
  • Can be assigned
  • Where
  • n number of machines operator handles
  • l total operator loading and unloading time
  • m total machine running time
  • w worker time between machines.

  • Should n be 3 or 4?
  • Figure out how much it costs per unit of
    production if
  • 3 machines are assigned to each worker
  • 4 machines are assigned to each worker
  • Choose the assignment that is least expensive.

Random Servicing
  • This method applies when you have one person
    handling several machines (or things) that
  • Do not run for a set length of time,
  • Need servicing at irregular intervals
  • Examples
  • Machine repair machines break at random times.
  • Call center, calls come in at random times.

Random Servicing Approach
  • The proportion of time, p, that a machine is up
    or down can be estimated through a time study
    (Chapter 9) or a work sampling study (Chapter 14)
  • q 1 - p
  • P the probability that m out of n total
    machines are down is
  • P (m of n) n! x pm qn-m
  • m! (n m)!

Random Servicing Example
  • Suppose at a call service center you have one
    phone operator to answer
  • n 4 phone lines
  • p 0.10 probability that a phone line is in
    use is.
  • q 1 p 0.9 the probability that a given
    phone line is unused, e.g. no one on the line.
  • In use means that a caller may be either
  • waiting on the line, or
  • speaking with the phone operator.
  • If calls come into the center at random, what is
    the probability that there will be exactly three
    phone lines in use? (e.g. One caller speaking
    with the operator, two callers waiting).

Random Servicing Example
  • No callers 4! x (.10 ) (.94)
  • 0! (4 0)!
  • One caller 4! x (.11 ) (.93 )
  • 1! (4 1)!
  • Two callers 4! x (.12 ) (.92) .05
  • 2! (4 2)!
  • Three callers 4! x (.13 ) (.91) .0036
  • 3! (4 3)!
  • Four callers 4! x (.14 ) (.90) .0001
  • 4! (4 4)!

Random Servicing Example
  • In other words, in this situation
  • 66 of the time, the sales assistant has no
  • 29 of the time, exactly one call
  • 5 of the time, exactly two calls, e.g. the
    assistant helps one customer while one customer
  • Less than a half a percent of the time (0.36 ),
    exactly three calls one customer is being
    helped while two customers listen to Musak. 
  • The probability that all 4 lines are in use at
    once is almost non-existent.

Coffee Shop Study
  • No studies had been done previously at this
    company to assess current efficiency
  • Goal to identify any way possible of improving
  • Initial request do a time study at 3 very
    different stores, improve productivity of coffee
    making process.
  • Corporate goal customer should be in and out
    within 3 minutes, door-to-door.

Observational tools
  • Site walk-thrus look at layout, tools equipment,
    how they are used.
  • Interviews of workers and managers to identify
    what they view as problems,
  • Ethnographic studies observe work in detail as a
    fly on the wall as it normally occurs in its
    normal setting, possibly over a long period of
    time. Good for observing interactions between
  • Time and/or motion studies to learn detail about
    what people do and how long it takes.

Job Worksite Analysis Guide
  • Check list of items to think about/examine while
    touring jobsite
  • How do parts/products flow in and out?
  • What kinds of motion are involved?
  • Are any tools being used?
  • Were there awkward motions?
  • Is worker fatigued? Stressed?
  • Is there decision making?

Time and Motion studies
  • In a time study
  • Often applied to large or small tasks,
  • Work is observed Work is broken into elements
  • Each element is timed,
  • The process is re-engineered to be faster, safer,
    less error-prone, etc.
  • In a motion study
  • Often applied to fine-grained continuous motions,
  • Motions are observed in performing a task,
    Motions are be divided into therbligs
  • The process is re-engineered by
  • eliminating unnecessary motions,
  • re-sequencing motions.

The two are often combined.
Tools for Time and Motion Studies
  • Tools can be simple and low cost
  • Stop watch,
  • Pen and paper,
  • Maybe a video camera. The task determines if it
    is necessary.
  • The technique is low-tech, but can still result
    in major cost savings!

How did your group speed up your assembly process?
  • Use multiple packers,
  • Use two hands,
  • Lay-out pieces in advance in order of assembly,
  • Orient each object in correct position in
  • Sequence objects to be easier to pack,
  • Fewer objects less material handing time

What about thinking tasks?
  • Time and motion studies apply to physical aspects
    of the task and physical objects.
  • What about the psychological aspects of a task?
    How can one study thought work and apply
    factors to improve the work of people who do
    driving, design, planning, management, and
    decision making?

Additional Approaches Time and thought studies
  • Protocol Studies
  • Have the person talk out loud as they solve a
  • E.g. create a design or manufacturing plan, or
    solve an algebraic problem
  • Record everything said and done on audio and
    video tape, or written notes
  • Ethnographic Studies
  • Observe in the workplace where people are doing
  • Nuclear power plant
  • Cockpit of airplane
  • NASA control center (for Mars Explorations)
  • Record what is said and done (video or written
  • Analyze

Example of a Protocol Study
  • Protocol means record
  • Need 2 volunteers
  • Experimenter
  • Subject
  • Tools
  • Normal tools used for task, often pencil and
    paper in an office setting,
  • Experimenter needs pencil and paper (or other
    recording equipment tape recorder, video).

A thinking task
Common themes in Human Factors approaches
  • Observation of human activities in performance of
  • Re-engineer many aspects of the task (tools,
    process, etc.) to improve effectiveness
  • The tools and techniques are often simple but

In-Class Exercise
  • Each group will be given a set of objects to
    assemble into a box.
  • The items will be varied in
  • shape
  • size,
  • flexibility,

In-Class Exercise
  • Figure out how to fit all the objects in the box
  • Decide what actions constitute therbligs or
  • Develop and record a procedure (in terms of
  • Figure out how to do it fast
  • Time your procedure (minutes, seconds)
  • Did your therblig descriptions change?
  • Did your procedure descriptions change?
  • Did other things change?

Rules of Exercise
  • Take all objects out and set them separately on
  • Fit all objects in the box so that you can close
    the lid all the way.
  • No squashing or damaging objects.
  • You may wish to assign different roles to the
    people on your team packer, time keeper, process
    recorder, observer, etc.
  • You will get several minutes to practice, then we
    will have a competition.

Exercise (continued)
  • Each group please report
  • Your best time to complete the task
  • Your therbligs
  • Your procedure (sequence of therbligs)
  • What you did to improve your time? (did you
    develop new therbligs? New sequence? Other?)

What Observational tools were used in Coffee Shop
  • Interviews with employees
  • Site walk-thru
  • Time studies of operations for three types of
    store setups and three job roles (4 hours
    observation each)
  • Cashier
  • Superglue
  • Barista
  • Other measurements (had to design measurement
    methods appropriate for context)
  • At what rate do customers enter?
  • How long does it take an individual customer to
    go door to pick-up?

Site walk-thru Customer Area
Tightly constrained workspace Hard to find a
safe place from which to observe!
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Which Exploratory Tools did we Use in the Coffee
Shop Study?
  • Other types of charts rate of customer arrival
    when are the busy times?
  • Comparison of total customer wait times at
    different stores,
  • Comparison of customer volume at different stores,

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Difficult Part
  • How do you translate this exploratory data into
    ideas of what to do?
  • What does this say about where the problems might
  • How do I know if the what the data shows is good
    or bad? Is the most costly item a problem or
    a necessary part of the process?