Department of Industrial Engieering Operations Analysis...
Transcript of Department of Industrial Engieering Operations Analysis...
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Department of Industrial Engieering
Assistant Prof. Abed Schokry
Operations Analysis Chapter 6 new
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Learning Outcomes
After successful studying this chapter You should be able to:
• Define operations analysis and methods engineering,
• Explain the objectives of operations analysis and methods
engineering,
• Distinguish between the different analysis techniques,
• Discuss the techniques: Histograms, Pareto charts, Pie charts,
Check sheets, Defect concentration diagrams, Scatter diagrams,
Cause and effect diagrams, Control chart, Flow Chart)
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Analysis techniques
Between operations Within an operation
Multi Activity charts Fish bone
Project scheduling Economic lot size
Flow diagrams and process
charts
Breakeven chart
Location of new item Subjective opinion
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Operations Analysis
• “Big” picture:
– Analysis of several operations or tasks
• “Little” picture:
– Analysis of an individual job
• “Miniature” picture:
– Analysis of specific motions
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Operations Analysis
Study of an operation or group of related operations
for the purpose of analyzing their efficiency and
effectiveness so that improvements can be developed
relative to specified objectives.
Objectives in operations analysis
– Increase productivity
– Reduce time and cost
– Improve safety and quality
• Methods engineering and operations analysis are very
similar, except that methods engineering places more
emphasis on design.
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Methods Engineering and Operations Analysis
• Methods engineering is the analysis and design of work
methods and systems, including the tooling, equipment,
technologies, workplace layout, plant layout, and work
environment
• Other names for methods engineering:
– Work study
– Work simplification
– Methods study
– Process re-engineering
– Business process re-engineering
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Objectives in Methods Engineering
• Increase productivity and efficiency
• Reduce cycle time
• Reduce product cost
• Reduce labor content
Other Objectives
• Improve customer satisfaction
• Improve product and/or service quality
• Reduce lead times and improve work flow
• Increase flexibility of work system
• Improve worker safety
• Apply more ergonomic work methods
• Enhance the environment (both inside and outside the facility)
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Location of One Item
• If we want to locate one item in a network of
customers— It is important to define some criterion
• Problem is to minimize some criterion:
– Distance moved by people or product
– Amount of energy lost
– Time to reach a customer
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Location of One Item: Solution
• Total cost is sum for all customers of weighting of
customer x distance moved
• Most of cost of moving may be a constant factor.
• Distance cost may rise by a factor of 2.
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Systematic Layout of Multiple Items: Step 1
Group the departments within the factory.
• Use a from–to table to establish product relationships.
• Use a relationship chart to establish service
relationships.
• Identify design constraints.
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Assign floor space to each activity area.
• Inventory will expand to fill the space.
• Consider space for the following:
– Operator
– Maintenance access
– Movement of parts of machine
– Local storage of parts and supplies.
Systematic Layout of Multiple Items: Step 2
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Make an activity relationship diagram.
• List all A relationships, then B’s, C’s, D’s, and E’s.
• Make a diagram with just the A’s.
• Add the B’s, keeping E restrictions in mind.
• Add the C’s.
• D’s are not used.
Systematic Layout of Multiple Items: Step 3
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Make scaled layouts of at least two designs.
• Use a CAD system or pieces of stiff paper.
• Areas/shapes of departments can be adjusted.
• Search for the best solution, not just a satisfactory one.
• E relationships may be satisfied with walls or barriers.
• A relationships may be satisfied with communication or conveyors.
Systematic Layout of Multiple Items: Step 4
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Evaluate the alternatives.
• Identify criteria and their weights.
• Grade each layout on each criterion.
• Calculate each layout’s “grade-point.”
• Have people sign off on the evaluation form.
• Select features from the alternatives to create an
improved set of designs.
Systematic Layout of Multiple Items: Step 5
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Detail the layout.
• Replace boundary lines with walls or barriers.
• Refine estimates of machine and operator quantities.
• Determine material handling and aisles.
• Locate machines and operators.
• Detail utilities and service areas.
Systematic Layout of Multiple Items: Step 6
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Important Items First (Pareto Distribution)
• Don’t waste time on unimportant problems.
• To check quickly whether a project is worth considering, calculate:
– Savings/year if material cost is cut 10%
– Savings/year if labor cost is cut 10%
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Pareto Distribution
• A small proportion of
the population has a
large proportion of the
criterion.
• (The vital few Concept)
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Pareto Chart
Special form of histogram in which attribute data are arranged
according to some criterion such as cost or value
• Based on Pareto’s Law: “the very important few and the
unimportant many”
• Often identified as the 80%-20% rule
– 80% of a nation’s wealth is owned by 20% of the population
– 80% of sales are accounted for by 20% of the Stock Keeping
Units
– 80% of a factory’s production output is concentrated in only
20% of its product models.
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Pareto Distribution
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Flow Diagrams and Process Charts
• Visually organize and structure a problem rather than
provide a solution.
• Flow diagrams:
– Show an operator or object’s physical movement.
• Process charts:
– Describe movement with descriptions and
symbols
• Assembly process charts:
– Show relationships among components and
emphasize storage problems.
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Multi-Activity Charts
• Purpose is to improve utilization of resources.
• Each column shows activity or idle time of a single
resource.
• Work best for standardized situations.
• Can reveal need for double tooling or kitting.
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Fish-Bone- Diagram (has other names)
• Depict a multidimensional list graphically.
• Widely used in Japanese Quality Circle
meetings.
• Start with the “effect” at the “head.”
• Add “bones” for possible causes.
• Add “minor bones” for details of causes.
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Cause and Effect Diagram
A graphical-tabular chart used to list and analyze the potential
causes of a given problem
• Can be used to identify which causes are most significant and
how to take corrective action against them
• Also known as a “fishbone diagram”
• In application, cause and effect diagrams are often developed by
worker teams who study operational problems.
• The diagram provides a graphical means for discussing and
analyzing a problem and listing its possible causes in an
organized and understandable way.
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• As a starting point in identifying the causes of the problem,
six general categories of causes are often used because
they are the factors that affect performance of most
production and service processes. They are called the 5Ms
and 1P
• Machines
– This refers to the equipment and tooling used in the process.
• Materials
– These are the starting materials in the process.
Cause and Effect Diagram (cont.)
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• Methods
– This refers to the procedures, sequence of activities, motions,
and other aspects of the method used in the process.
• Mother Nature
– This is for environmental factors such as temperature and
humidity that might affect the process.
• Measurement
– This relates to the validity and accuracy of the data collection
procedures.
• People
This is the human factor.
Does the worker bring the necessary skills to the process?
Cause and Effect Diagram (cont.)
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Cause and Effect Diagram (Ishikawa)
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Decision Structure Tables
• Describe complex, multi-rule, multivariable decision
systems.
• Enforce thoroughness (attention to details) in
methods analysis.
• May be constructed in spreadsheet programs.
• Also known as contingency (possibility) tables or
protocols.
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Subjective Opinions
Tools provide precise and quantified responses.
• Borg vote (rating of perceived exertion)
• Body discomfort map
• Absolute adjective scales
• Relative (paired) votes
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Evolutionary Operation of Processes (EVOP)
Evolutionary Operation (EVOP) is a manufacturing
process-optimization technique developed in the 1950s
by George E. Box. (DOX)
• Processes produce two things:
– Items for sale
– Information about the process
• EVOP views the production process as a “free”
ongoing experiment.
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Example Applications of EVOP
Application Criterion Some Variables
Turning Machining cost;
surface finish
Feed, speed, tool geometry
Welding Weld strength Cooling rate, amps, rod
type
Painting Scrap rate Paint–thinner ratio, gun
distance
Casting Yield Pouring temp, additive
percentages
Chemical
processes
Yield Time, temp, percentages of
constituents and
catalysts
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Yield Management
Yield management is a variable pricing strategy, based on
understanding, anticipating and influencing consumer
behavior in order to maximize revenue from a fixed, time-
limited resource (such as airline seats or hotel room
reservations or advertising inventory). As a specific,
inventory-focused branch of revenue management.
Yield management involves strategic control of inventory to
sell it to the right customer at the right time for the right
price. This process can result in price discrimination, in
which customers consuming identical goods or services are
charged different prices.
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Charting & Diagramming Techniques
• Network diagrams These are used for analyzing work flow,
assembly line balancing, and project scheduling.
• Traditional industrial engineering charting techniques
– These are used to symbolize and summarize the details of an
existing operation or sequence of operations.
– The traditional charting techniques can be used to analyze the
activities of one human worker, groups of workers, worker-machine
systems, materials, parts, and products.
• Block diagrams
– These diagrams represent alternative ways of illustrating
processes.
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Project Scheduling
• Plan the work
– List project tasks
– List precedence requirements
– Allocate resources to determine time
• Work the plan
– Execute
– Continually revise and update plan
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Gantt Charts
• List of tasks on Y axis, time on X axis
• Bars show planned start and finish times and actual
progress.
• Advantages:
– Shows situation at a glance
– Is easy to modify (without computers or math)
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Simplified PERT
• Shows sequence and precedence of tasks
• Numbers show forward pass and backward pass
times.
• Advantages:
– Shows potential problems
– Shows which tasks should be expedited (critical path)
– Sets up progress checkpoints
– Tends to be self-fulfilling
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Enhanced PERT
• Uses three time estimates (optimistic, most likely,
pessimistic)
• Requires estimate of task costs for normal and
“crash” time
• Advantages:
– Permits estimate of time variability
– Permits tradeoff of task times against cost
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Component of System design
CONTEXT
Equipment
User Task
Environment
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System design
• Factor considered in System Design
Factor Considered System centered User Centered Socially Centered
Equipment -specification
-maintenance
-design to minimize
human error
-design of tech-artifact
that support work
practices
Task -procedures, method,
instructions, task input-
output
-design to enhance
human abilities and
overcome limitation
-design of corporative
activities
Users -spec of roles, training
procedures, etc
-spec of roles and
responsibilities that
foster user satisfaction
-spec in situated roles
and responsibilities
-identify direct and
indirect user
Environment -facility
-safety, work hour, job
function
-workplace condt. And
design
-spec of informal work
practices and shared
artifact
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Data collection and analysis activities for the type of problem being
studied.
• Activities often used in this step include the following:
– Identify the basic function of the operation.
– Gather background information.
– Observe the existing process or observe similar processes if
the problem involves a new work design.
– Collect data on the existing operation and document the details
in a format that provides itself to examination.
– Conduct experiments on the process.
– Develop a mathematical model of the process or utilize an
existing mathematical model
– Perform a computer simulation of the process.
– Use charting techniques.
Analyze the Problem
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Data collection and analysis activities for the type of problem being
studied.
• Activities often used in this step include the following:
– Conduct experiments on the process.
– Develop a mathematical model of the process or utilize an
existing mathematical model
– Perform a computer simulation of the process.
– Use charting techniques.
Analyze the Problem (cont.)
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Techniques of Methods Engineering
• Data gathering and statistical tools
• Charting and diagramming techniques
• Motion study and work design
• Facility layout planning
• Work measurement techniques
• New approaches
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Basic Data Collection & Analysis Tools
1. Histograms
2. Pareto charts
3. Pie charts
4. Check sheets
5. Defect concentration diagrams
6. Scatter diagrams
7. Cause and effect diagrams
8. Quality Control
9. Flow Chart
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Histogram
• A histogram is a statistical graph consisting of bars
representing different values or ranges of values, in which
the length of each bar is proportional to the frequency or
relative frequency of the value.
• A useful tool because the analyst can quickly visualize the
features of the data, such as:
(1) the shape of the distribution,
(2) any central trend exhibited by the distribution,
(3) approximations of the mean and mode of the distribution,
(4) the amount of scatter or spread in the data.
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Histogram for Data Display
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Pie Charts
Example: Annual sales revenues and customer distributions for two
years
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Expected Benefits:
•Verification that there is or is not a relationship between 2 factors.
• Identifying an independent controlling factor for a dependent
factor.
Uses of this tool:
•To understand the behaviour of a process.
•To determine if there is a relationship between two factors.
•To visually demonstrate the correlation between two related
factors.
•To determine where there may be a cause and effect relationship.
Scatter Diagram - What is it for?
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Background:
•Sometimes two separate
things appear to change
together and there may be
suspicion that they are
related somehow. The Scatter
Diagram visually shows how
well correlated they are.
•The Japanese guru Kaoru
Ishikawa included Scatter
Diagrams as one of his 7
basic tools.
Uses:
•Use it during the analysis phase
to understand the behaviour of
a process and how a pair of
variables change relative to one
another (correlation).
•Use it to provide an input to
cause and effect analysis.
•After improvement, to find out
how much the behaviour of the
process has changed.
Scatter Diagram - Where it can be used?
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Scatter Diagram - How do I use it? - Correlation
None Low High Perfect
Degrees of correlation
NegativePositive Curved Partial
Types of correlation:
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Scatter Diagram - Risks
Risks:
•Assuming that because two factors are well correlated
there is a cause-and-effect relationship between them.
•Dots are clumped in one area of scatter diagram.
•Data needs to be plotted at the same point - therefore
the ‘weight’ of the numbers of points is lost.
•There is a difference in the sources of the data - this
may have a relevance.
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Scatter Diagram - how to avoid them?
Steps to avoid them:
•Understand the difference between correlation and causation. At
best, see correlation as indication of possible cause that will need
further testing to prove any actual causal relationship.
•Chose the axis scales carefully so that maximum spread is
achieved. (e.g. use values close to the minimum and maximum
values for the start and end points of each axis.
•Apply concentric circles to these points to indicate the ’weight’
•Plot the different sources using different symbols (See also
Sampling / Stratification)
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Do trials in three areas with
speed limits at 20, 25 and 30.
0
2
4
6
8
10
0 5 10 15
Vehicles per minute
Accid
ents
in d
ay
Scatter Diagram - Example
Understand factors that may
lead to road accidents
1. Identify purpose5. Plot Scatter Diagram
6. Interpret
Speed = Average Speed
Density = Vehicles per minute
3. Identify measures 0
2
4
6
8
10
0 10 20 30 40 50 60
Average speed
Accid
en
ts in
da
y
Average
Speed
Vehicles
per minute
Accidents
in day
15.40 0 1
43.40 3 6
31.00 2 2
27.40 1 1
32.80 1 3
40.20 3 5
34.20 6 4
8.40 0 1
20.80 1 1
33.40 3 3
32.00 1 2
17.00 0 1
26.60 1 1
15.40 1 2
29.40 2 2
4. Collect data
Close correlation between
speed and accidents when
speed is above about 25
Weak correlation between
traffic density and accidents
7. Take action
Traffic speed and density
2. Identify two factors
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Defect concentration diagram
This is used to understand the potential defect prone area of the parts produced
The “Concentration Diagram” check sheet carries the diagram of the problematic part, defects whenever observed to be updated in the same using tally marks
Based on the distribution of defects countermeasures are taken at process/system level
This tool is very useful to solve problems like Scratch, Dent, Breakage thru’ handling improvement
For plastic molded parts this tool is used to identify stress points, weak joints, effect of gate shape/position on the quality of parts etc.
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Component
name : XYZ
Concentration
diagram for
Scratches
produced ion
21-Aug-03
Total no of
defective
produced is 11
Area of
concern
Defect concentration diagram
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Defect concentration diagram
Solder: لحام
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Check Sheets Defined
What is a check sheet?
A basic tool for monitoring quality improvement
processes
A simple data collection device
There are two varieties of check sheets
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Check Sheets Defined (cont.)
Common Types
Distribution Check Sheets
Used to collect data in order to determine how a variable is dispersed within an area of possible occurrences
Location Check Sheets
Highlights the physical location of a problem/defect in order to improve quality
They may also utilize visual(schematic) drawings of areas in order to record where problems are occurring
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Common Types, Continued
Cause Check Sheets
Used to keep track of how often a problem happens
or records the cause to a certain problem.
Classification Check Sheets
Used to keep track of the frequency of major
classifications involving the delivery of products or
services
Check Sheets Defined (cont.)
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Check Sheet
Billing Errors
Wrong Account
Wrong Amount
Wrong Account
Wrong Amount
Monday
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• Deviation from Mean
• Upper and Lower Spec’s
• Range
Control Charts
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Upper Limit
Lower Limit
Unacceptable
deviation
X
Control Charts
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• A graphical picture of a PROCESS
Process Decision
The process
flow
Flow Chart
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Don’t Forget to:
• Define symbols before beginning
• Stay consistent
• Check that process is accurate
Flow Chart
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End of Chapter