Department of Industrial Engieering Operations Analysis ...site.iugaza.edu.ps/aschokry/files/2014/01/Operations-Analysis-Chap-6.pdf · Methods Engineering and Operations Analysis

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Islamic University of Gaza - Palestine

Department of Industrial Engieering

Assistant Prof. Abed Schokry

Operations Analysis Chapter 6 new


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


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.


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)


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.


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.



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.


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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.



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.


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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.



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)


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


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.


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.


• 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.)


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.


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.


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.


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


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


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


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


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


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.


Histogram for Data Display

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Pie Charts

Example: Annual sales revenues and customer distributions for two

years


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?


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.


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


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




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


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.)


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


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


Don’t Forget to:

• Define symbols before beginning

• Stay consistent

• Check that process is accurate

Flow Chart

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End of Chapter

Documents

Department of Industrial Engieering Operations Analysis ...site.iugaza.edu.ps/aschokry/files/2014/01/Operations-Analysis-Chap-6.pdf · Methods Engineering and Operations Analysis