Six Sigma Quality Engineering

1
Six Sigma Quality Engineering

• Week 7
• Analyze Phase

2
Chapter 6 Outline

• Process Map
• Inputs characteristics
• Cause Effect
• Fishbone Diagram (Minitab)
• CE Matrix (Excel)
• Failure Mode Effect Analysis (FMEA)
• Process Capablity
• Cpk
• Cp
• Minitab Tutorial
• In this session you will learn how to
•     Produce X and R charts
•     Produce histograms with normal curves
•     Perform a process capability analysis

3
Detailed Process Map Example
4
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...

5
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
6
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

7
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

8
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

9
CE (Fishbone Diagram)

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

Effect
10
Causes (Fishbone Diagram)

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

11
Machine
Environment
Effect
People
Methods
Material
12
Cause and Effect (Matrix)

• Benefit
• Gain new knowledge and perspectives by sharing
  ideas with others
• Helps us understand our processes
• Provides a basis for action
• Whenever a problem is discovered, using CE
  analysis forces us to take a proactive stance by
  seeking out causes

13
2
1
56
3
4
14
CE Matrix

• Instructions

This table provides the initial input to the FMEA
and experimentation. When each of the output
variables (requirements) are not correct, that
represents potential "EFFECTS". When each input
variable is not correct, that represents "Failure
Modes". 1. List the process output variables
2. Rate each output on a 1-to-10 scale to
importance to the customer 3. List process input
variables (from the process map) 4. Rate each
input's relationship to each output variable
using a 0, 1, 3, 9 scale 5. Select the high
ranking input variables to start the FMEA
process Determine how each selected input
variable can "go wrong" and place that in the
Failure Mode column of the FMEA.

15
FMEA

• It is an approach to
• Identify potential failure for a product or a
  process
• Estimate risks that are associated with causes
• Determine actions to reduce risks
• Evaluate product design validation plan
• Evaluate process current control plan

16
FMEA types

• There are two types
• Process Will focus on Process Inputs
• Design Will used to analyze product designs
  before they are released to production

17
The use of the FMEA

• Improve processes before failure occur (Proactive
  approach)
• Prioritize resources to ensure process
  improvement efforts are beneficial to customers
• Track and document completion of projects
• It is a living document. It will be updated and
  reviewed all the time

18
Inputs Outputs to FMEA

• Inputs
• Process Map
• CE Matrix
• Process History
• Process technical procedures
• Outputs
• Actions list to prevent causes
• Actions list to detect failure modes
• Document history of actions taken

19
FMEA step-by-step

• For each process input, determine the ways in
  which the input can go wrong- the failure modes.

What can go wrong with input
20
FMEA step-by-step

• For each failure mode associated with the inputs,
  determine the effects of the failures on the
  customer.

What the effect on outputs?
21
FMEA step-by-step

• Identify potential causes of each failure mode.

What are The causes?
22
FMEA step-by-step

• List the current controls for each cause or
  failure mode (Prevent/Detect).

How are these Found or prevented?
23
FMEA step-by-step

• Create Severity, Occurrence, and Detection rating
  scales.
• Severity of effect- importance of effect on
  customer requirements. It is a safety and other
  risks if failure occurs.
• 1 Not Severe, 10 Very Severe
• Occurrence of cause- frequency in which a give
  Cause occurs and creates Failure Mode. Can
  sometimes refer to the frequency of a failure
  mode.
• 1 Not Likely, 10 Very Likely

24
FMEA step-by-step

• Create severity, Occurrence, and Detection rating
  scales.
• Detection- ability to
• Prevent the causes or failure mode from occurring
  or reduce their rate of occurrence
• Detect the cause and lead to corrective action
• Detect the failure mode
• 1 Likely to Detect, 10 Not Likely at all to
  Detect

25
FMEA step-by-step

• Risk Priority Number
• After rating we get the output on an FMEA Risk
  Priority Number. It is calculated as the product
  of Effects, Causes, and Controls
• RPN Severity X Occurrence X Detection

Effects
Causes
Controls
26
FMEA step-by-step

• Dynamics of the Risk Priority Number
• The team defines the rating scales 1-10 for the
  severity, Occurrence, and Detection ratings. The
  team choose the levels and numbers
• How severe is it Not Severe 1
• Somewhat
  3
• Moderately
  5
• Very Severe
  10

27
FMEA step-by-step

• Dynamics of the Risk Priority Number
• The team defines the rating scales 1-10 for the
  severity, Occurrence, and Detection ratings. The
  team choose the levels and numbers
• How often does it Occur?
• Never/rarely
  1
• Sometimes
  3
• Half the time
  5
• Always
  10

28
FMEA step-by-step

• Dynamics of the Risk Priority Number
• The team defines the rating scales 1-10 for the
  severity, Occurrence, and Detection ratings. The
  team choose the levels and numbers
• How well can you detect it?
• Always
  1
• Sometimes
  3
• Half the time
  5
• Never
  10

29
FMEA step-by-step

• Determine recommended actions to reduce high
  RPNs

What can be done?
30
FMEA step-by-step

• Take appropriate actions and recalculate RPNs

Assign responsible Parties
31
Process Capability Study
32
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.

33
Process Capability Study
34
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

35
Questions? Comments?