six sigma quality engineering

8/2/2019 Six Sigma Quality Engineering

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CSUNEngineeringManagement

Six Sigma Quality

Engineering

Week 4Measure Phase


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Chapter 5 Outline

Process Map/Spaghetti Diagram Cause & Effect Fishbone Diagram Cause & Effect Matrix Reproducibility & Repeatability (Gage R&R) 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 aprocess

A detailed process map includes information that can be usedto 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

KLNS

(Y'AciDe(Y's)Surf- Re- Re- 'De

TB

(SS

N

NDTA

ATN

(x'CCNSNNN

NSCN

(x's)C TiN PN OS RS M(x's)C MaHydC PicS AgN Qu

N CoN ProS PaN OpS Sh

BATH

(Y's)

Uniformity ofNo excess fl

TUNN

(Y's)

Dry castinWarm cas

IN ZIN

H / BU

(Y's)Coating- Thickn

- Unifor- Total

- Appea- Rough

- Comp

TER SPNOCK

RUM

(AS

(Y's)

Zinc :Appe

RemoFittin

COAFITTI(x's)C Speed of c

C TemperatuC Make up ofS CleanlinesN GeometryS Pendant stS Amount peS Weight of p(Heat remoS Time fromN Humidity

(x's)

C Speed ofS TemperaN GeometrN HumidityS Air veloci(x's)S QualityC TempeS LevelS LevelN GeomeN OperatS QualityN SpecifiS Rate oS FluidityN Power

(x's)

S WatN WatC SpeN Mas(Rate

(x'

CC

NS


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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 supposedto 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

Machining a shafton a lathe

Inputs (xs)Rotation speedTraverse speedTool typeTool sharpnessShaft materialShaft lengthMaterial removal per cut

Part cleanlinessCoolant flowOperatorMaterial variationAmbient temperatureCoolant age

Outputs (Ys)DiameterTaperSurface finish

CCCCCCC

SCNNNS


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BEFORE40 NVA STEPS

NOTE: FROM THE CUSTOMERS

VIEWPOINT ALL OF ORDER ENTRY

IS NON-VALUE ADDED

Order Entry Process MapAs-Is


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AFTER11 NVA STEPS

REMEMBER: FROM THE CUSTOMERS VIEWPOINT

ALL OF ORDER ENTRY IS NON-VALUE ADDED

We eliminated the steps thatwere NVA and

UNNECESSARY (WASTE)BEFORE

40 NVA STEPS

Order Entry Process MapNew


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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 ofthe work space.

The purpose of the work-flow diagram is to illustrate theinefficiency in a clear picture.

How can you make the map look simpler? What lines canyou eliminate?


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56 Frame (Small Motor) Assy & Fabrication -Before

BEFORE KAIZEN:Area: 4640 sq ftOperator Travel: 3696 ftProduct Travel: 1115 ft x

xx x

x xx

xx


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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 aproblem

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 investigatinga 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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Effect

PeopleMethodsMaterial

Machine Environment


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Cause & Effect

matrix


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The Eight Steps in Cause and EffectAnalysis

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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Rating of

Importance to

Customer

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Total

Process Step Process Input

1 0

2 0

3 0

4 0

5 0

6 0

7 08 0

9 0

10 0

11 0

12 0

13 0

14 0

15 0

16 0

17 0

18 0

19 0

20 0

0

Total 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

Lower Spec

TargetUpper Spec

1

2

3

4

5&

6


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Reproducibility & Repeatability

(Gage R&R)

Data is only as good as the system that measures it. If you

cant measure it, you cant manage it.


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I often say that when you measure what you are speakingabout and express it in numbers, you know something about it.

LORD KELVIN, 1891

He clearly stressed that little progress is possible in any field ofinvestigation without the ability to measure. The progress of

measurement is, in fact, the progress of science.

The Science of Measurement


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Objectives

Measurement Systems Analysis Key Terminology

Variable Gauge R&R

A tool for estimating measurement system error

How to conduct a gauge R&R

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 usedseveral times by one appraiser.

Reproducibility

Variation in the average of the measurements made by differentappraisers using the same measurement system.


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What is GR&R?

Measurement Systems Analysis

GRRRRRRR!!!

2T =

2p +

2m

2T = Total Variance

2p = Process Variance

2m= Measurement Variance

How good is ourmeasurement system?

G R&R All C t l f th


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Gauge R&R Allows Control of theMeasurement System


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Variable Gauge R&R - Whats Involved?

1 Gauge

3 Appraisers

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 R&R 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

R&R 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 systemneeds improvement.

Number of Distinct Categories Index

1 Unacceptable. One part cannot be

distinguished form another. 2 -4 Generally unacceptable

5 Recommended

Module0025


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Minitab Gage R&R 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 ableto 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?