CSUN EngineeringManagement

Six Sigma Quality Engineering

Week 4Measure Phase

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

Process Map/Spaghetti Diagram

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

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

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

Detailed Process Map Example

PICKLE RINSE

(Y's)Acid freeDebris removed

(Y's)Surface cleanliness- Removel of sand- Removal of rust- 'Defect free'

SHOTBLAST

(Y's)Surface cleanliness (dust / rust free)Surface roughness

HANG ON PENDANTSSTAND

UNCOATED FITTINGS

(x's)C TimeC Shot size / mix of sizesN HumidityS Type / Material / Original size of gritN Effectiveness of seperatorN Product geometryN Condition of machineN Dust arrestor conditionS Amount of work being shotblastC Time between pickle and shotblastN Operator

(x's)C TimeN Product geometryN OperatorS Rocked / Not rockedS Method of packing

(x's)C Make up of mix, Concentration and % of Hydrochloric Acid, Hydrofluoric Acid, Activol, WaterC Pickling timeS Age of mix / SGN Quality of work / containerN Containers / tankN Product geometryS Packing methodN OperatorS Shotblast prior to pickling

LYE BATH

(Y's)Uniformity of fluxNo excess flux (removed by Dry ing Oven)

DRYING TUNNEL

(Y's)Dry castingsWarm castings

DIP IN ZINC BATH / BUMP

(Y's)Coating Quality- Thickness of z inc / z inc alloy layers- Uniformity of coverage- Total coverage- Appearance- Roughness / texture- Compos ition of coating

WATER SPRAY KNOCK OFF

RUMBLE

(Y's)AppearanceSmooth Finish

(Y's)Zinc : Zinc Alloy thicknessAppearance (brightness)Removal of ash (c leanliness)Fitting temperature COATED

FITTINGS

(x 's)C Speed of chain / time in bathC Temperature of lye bathC Make up of lye bathS Cleanliness of lye bathN Geometry of partsS Pendant sty le / orientation of workS Amount per pendantS Weight of product per minute put through bath (Heat removal + heat pickup)S Time from shotblastN Humidity

(x's )C Speed of chainS Temperature of tunnelN Geometry / Mass of fittingsN HumidityS Air velocity

(x 's )S Quality of supplier / materialsC Temperature of z incS Level of drossS Level of leadN Geometry / mass of fittingsN Operator (Sk imming surface / agitation of pendants)S Quality of pendantsN Specifiacation (BS, ISO, EN)S Rate of withdrawalS Fluidity of z incN Power of bumper unit

(x 's)S Water volumeN Water temperatureC Speed of chainN Mass / Geometry of fittings (Rate of cooling)

(x's )C TimeC Number of fittings per loadN Geometry of fittingsS Condition of rumbling barrel

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

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? (Y’s)• What impacts the quality of each Y? (x’s)

Characterise the inputs

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...

Example

Machining a shaft on a latheInputs (x’s)

Rotation speedTraverse speedTool typeTool sharpnessShaft materialShaft lengthMaterial removal per cutPart cleanlinessCoolant flowOperatorMaterial variationAmbient temperatureCoolant age

Outputs (Y’s)DiameterTaperSurface finish

CCCCCCCSCNNNS

BEFORE40 NVA STEPS

NOTE: FROM THE CUSTOMER’S VIEWPOINT ALL OF ORDER ENTRY IS NON-VALUE ADDED

Order Entry Process MapAs-Is

AFTER11 NVA STEPS

REMEMBER: FROM THE CUSTOMER’S VIEWPOINT ALL OF ORDER ENTRY IS NON-VALUE ADDED

We eliminated the steps that were NVA and

UNNECESSARY (WASTE)BEFORE

40 NVA STEPS

Order Entry Process MapNew

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?

56 Frame (Small Motor) Assy & Fabrication - Before

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

xxx x

x xxxx

Cause & Effect Fishbone Diagram

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

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

Fishbone Diagram

Effect

• The problem or quality characteristic

• The effect is the outcome of the factors that affect it

Effect

Fishbone Diagram

Causes

All the factors that could affect the problem or the quality characteristic

Five Major Categories

• Materials

• Methods

• People

• Machines

• Environment

Effect

PeopleMethodsMaterial

Machine Environment

Cause & Effect matrix

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

Rating of Importance to

Customer1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Total

Process Step Process Input

1 02 03 04 05 06 07 08 09 0

10 011 012 013 014 015 016 017 018 019 020 0

0

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

Lower SpecTargetUpper Spec

1

2

3

4

5&6

Reproducibility & Repeatability (Gage R&R)

“Data is only as good as the system that measures it. If you can’t measure it, you can’t manage it.”

“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.

The Science of Measurement

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

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.

What is GR&R?

Measurement Systems Analysis

GRRRRRRR!!!

2T = 2

p + 2m

2T = Total Variance

2p = Process Variance

2m = Measurement Variance

How good is our measurement system?

Gauge R&R Allows Control of the Measurement System

Variable Gauge R&R - What’s Involved?

1 Gauge

3 Appraisers

10 Parts

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

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)

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 system needs improvement.

Number of Distinct Categories Index• 1 Unacceptable. One part cannot be

distinguished form another.• 2 -4 Generally unacceptable 5 Recommended

Mod

ule

0025

Minitab Gage R&R Graphical Output

Minitab Gage R&R Graphical Output

Minitab Gage R&R Graphical Output

Minitab Gage R&R Statistical Output

Minitab Gage R&R Statistical Output

Capability Analysis

Process Capability Study

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.

Process Capability Study

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

Questions? Comments?