Six Sigma Quality Engineering

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Six Sigma Quality Engineering

• Week 4
• Measure Phase

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Chapter 5 Outline

• Process Map/Spaghetti Diagram
• Cause Effect Fishbone Diagram
• Cause Effect Matrix
• Reproducibility Repeatability (Gage RR)
• Capability Analysis
• Components of Variation Studies
• FMEA

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Process Map/Spaghetti Diagram
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What is a Process Map?

• A process map is a graphical representation of
  the flow of a process
• A detailed process map includes information that
  can be used to improve the process, such as
• Process Times
• Quality
• Costs
• Inputs
• Outputs

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Types of Process Map

• Basic process map
• Detailed process map
• Work-flow (spaghetti diagrams)
• Top-down flowchart
• Deployment flowchart
• Opportunity flowchart
• Current State / Future state maps

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Uses of a Process Map

• Identify areas for focus of improvement efforts
• Identify and eliminate non-value added steps
• Combine operations
• Assist root cause analysis
• Baseline for failure mode and effect analysis
  (FMEA)
• Identify potential controllable parameters for
  designed experiments
• Determine needed data collection points
• Eliminate unnecessary data collection steps

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Detailed Process Map Example
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Process Maps

• Should include
• Major activities and tasks
• Sub-processes
• Process boundaries
• Inputs
• Outputs
• Documents reality, not how you think the process
  is supposed to be completed
• Should identify opportunities for improvement

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Steps for Process Mapping

• Scope the process
• Identify the start and end points of the process
  of interest
• Document the top level process steps
• Create a flow chart
• Identify the inputs and outputs
• What are the results of doing each process step?
  (Ys)
• What impacts the quality of each Y? (xs)
• Characterise the inputs

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Characterising Inputs

• Inputs can be classified as one of three types
• Controllable (C)
• Things you can adjust or control during the
  process
• Speeds, feeds, temperatures, pressures.
• Standard Operating Procedures (S)
• Things you always do (in procedures or common
  sense things)
• Cleaning, safety.
• Noise (N)
• Things you cannot control or don not want to
  control(too expensive or difficult)
• Ambient temperature, humidity, operator...

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Example
Outputs (Ys) Diameter Taper Surface finish
Inputs (xs) Rotation speed Traverse speed Tool
type Tool sharpness Shaft material Shaft
length Material removal per cut Part
cleanliness Coolant flow Operator Material
variation Ambient temperature Coolant age
C C C C C C C S C N N N S
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Order Entry Process MapAs-Is
BEFORE 40 NVA STEPS
NOTE FROM THE CUSTOMERS VIEWPOINT ALL OF ORDER
ENTRY IS NON-VALUE ADDED
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Order Entry Process MapNew
REMEMBER FROM THE CUSTOMERS VIEWPOINT ALL OF
ORDER ENTRY IS NON-VALUE ADDED
We eliminated the steps that were NVA and
UNNECESSARY (WASTE)
BEFORE 40 NVA STEPS
AFTER 11 NVA STEPS
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Work-flow or Spaghetti Diagram

• A work flow diagram is a picture of the movements
  of people, materials, documents, or information
  in a process.
• Start by tracing these movements onto a floor
  plan or map of the work space.
• The purpose of the work-flow diagram is to
  illustrate the inefficiency in a clear picture.
• How can you make the map look simpler? What lines
  can you eliminate?

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56 Frame (Small Motor) Assy Fabrication - Before
x
x
x
x
BEFORE KAIZEN Area 4640 sq ft Operator Travel
3696 ft Product Travel 1115 ft
x
x
x
x
x
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Cause Effect Fishbone Diagram
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Cause Effect Fishbone Diagram

• Objectives
• To understand the benefits of Cause Effect
  Analysis
• To understand how to construct a C E Diagram
• Analysis
• A method a work group can use to identify the
  possible causes of a problem
• A tool to identify the factors that contribute to
  a quality characteristic

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Uses of C E Fishbone Diagram

• Visual means for tracing a problem to its causes
• Identifies all the possible causes of a problem
  and how they relate before deciding which ones to
  investigate
• C E analysis is used as a starting point for
  investigating a problem

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Fishbone Diagram

• Effect
• The problem or quality characteristic
• The effect is the outcome of the factors that
  affect it

Effect
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Fishbone Diagram

• Causes
• All the factors that could affect the problem or
  the quality characteristic
• Five Major Categories
• Materials
• Methods
• People
• Machines
• Environment

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Machine
Environment
Effect
People
Methods
Material
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Cause Effect matrix
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The Eight Steps in Cause and Effect Analysis

• Define the Effect
• Identify the Major Categories
• Generate Ideas
• Evaluate Ideas
• Vote for the Most Likely Causes
• Rank the Causes
• Verify the Results
• Recommend Solutions

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• Reproducibility Repeatability (Gage RR)

Data is only as good as the system that measures
it. If you cant measure it, you cant manage
it.
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The Science of Measurement
I often say that when you measure what you are
speaking about and express it in numbers, you
know something about it. LORD KELVIN,
1891 He clearly stressed that little progress
is possible in any field of investigation without
the ability to measure. The progress of
measurement is, in fact, the progress of science.

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Objectives

• Measurement Systems Analysis
• Key Terminology
• Variable Gauge RR
• A tool for estimating measurement system error
• How to conduct a gauge RR
• Minitab Output
• Gauge R R Study Exercise

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Definitions

• Variable Data
• Continuous measurements such as length, voltage,
  viscosity
• Repeatability
• Variation in measurements obtained with one gage
  when used several times by one appraiser.
• Reproducibility
• Variation in the average of the measurements made
  by different appraisers using the same
  measurement system.

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What is GRR?

• Measurement Systems Analysis

How good is our measurement system?
?2T ?2p ?2m
?2T Total Variance ?2p Process
Variance ?2m Measurement Variance
GRRRRRRR!!!
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Gauge RR Allows Control of the Measurement System
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Variable Gauge RR - Whats Involved?
3 Appraisers
1 Gauge
10 Parts
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How to set up a Variable GRR Study

• Preparation Planning
• 1 Gauge
• 3 Operators (Appraisers)
• 10 Parts
• 3 Trials
• Randomize the readings
• Code the parts (blind study) if possible
• 3 Ops x 10 parts x 3 trails 90 Data Points
• 4 Ops x 10 parts x 3 trails 120 Data Points

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Minitab Gage RR Graphical Output
The number of distinct categories of parts that
the process is currently able to distinguish
(Must distinguish at least 5 types of parts)
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Acceptability Criteria

• RR Indices
• ? 10 Acceptable Measurement System
• 10 - 30 May be acceptable based upon
  application, cost of measurement device, cost
  of repair, etc.
• ? 30 Not acceptable. Measurement system
  needs improvement.
• Number of Distinct Categories Index
• 1 Unacceptable. One part cannot be
  distinguished form another.
• 2 -4 Generally unacceptable
• ? 5 Recommended

Module 0025
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Minitab Gage RR Graphical Output
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Minitab Gage RR Graphical Output
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Minitab Gage RR Graphical Output
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Minitab Gage RR Statistical Output
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Minitab Gage RR Statistical Output
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Capability Analysis
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Process Capability Study
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Cpk Cp

• Cpk incorporates information about both the
  process spread and the process mean, so it is a
  measure of how the process is actually
  performing.
• Cp relates how the process is performing to how
  it should be performing. Cp does not consider the
  location of the process mean, so it tells you
  what capability your process could achieve if
  centered.

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Process Capability Study
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Non-normal distributions

• Use Capability Analysis (Nonnormal) to assess the
  capability of an in-control process when the data
  are from the nonnormal distribution. A capable
  process is able to produce products or services
  that meet specifications.
• The process must be in control and follows a
  nonnormal distribution before you assess
  capability. If the process is not in control,
  then the capability estimates will be incorrect.
• Nonnormal capability analysis consists of a
  capability histogram and a table of process
  capability statistics

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Questions? Comments?