Chapter 6 Outline
Process Map Inputs characteristics
Cause & Effect Fishbone Diagram (Minitab) C&E 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
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 PENDANTS
STAND
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 / tex ture- Composition 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 (Skimming 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
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 lathe
Inputs (x’s)Rotation speedTraverse speedTool typeTool sharpnessShaft materialShaft lengthMaterial removal per cutPart cleanlinessCoolant flowOperatorMaterial variationAmbient temperatureCoolant age
Outputs (Y’s)DiameterTaperSurface finish
CCCCCCCSCNNNS
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
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
C&E (Fishbone Diagram)
Effect
• The problem or quality characteristic
• The effect is the outcome of the factors that affect it
Effect
Causes (Fishbone Diagram)
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 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 C&E analysis forces us to take a proactive stance by seeking out causes
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 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 Spec
Target
Upper Spec
1
2
3
4
5&6
C&E 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 customer3. 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.
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 customer3. 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.
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
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
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
Inputs & Outputs to FMEA
Inputs Process Map C&E Matrix Process History Process technical procedures
Outputs Actions list to prevent causes Actions list to detect failure modes Document history of actions taken
FMEA step-by-step
For each process input, determine the ways in which the input can go wrong- the failure modes.
What is the process
step/input under investigation?
In what ways does the input go wrong?
What is the impact on the Output Variables
(Customer Requirements)
or internal requirements?
How
sev
er is
the
eff
ect
to t
he
cust
omer
?
What causes the input to go wrong?
How
oft
en d
oes
caus
e of
FM
oc
cur?
Process Step/Input
Potential Failure Mode
Potential Failure Effects Potential Causes
OCC
SEV
What can go wrong with input
FMEA step-by-step
For each failure mode associated with the inputs, determine the effects of the failures on the customer.
What is the process
step/input under investigation?
In what ways does the input go wrong?
What is the impact on the Output Variables
(Customer Requirements)
or internal requirements?
How
sev
er is
the
eff
ect
to t
he
cust
omer
?
What causes the input to go wrong?
How
oft
en d
oes
caus
e of
FM
oc
cur?
Process Step/Input
Potential Failure Mode
Potential Failure Effects Potential Causes
OCC
SEV
What the effect on outputs?
FMEA step-by-step
Identify potential causes of each failure mode.
What is the process
step/input under investigation?
In what ways does the input go wrong?
What is the impact on the Output Variables
(Customer Requirements)
or internal requirements?
How
sev
er is
the
eff
ect
to t
he
cust
omer
?
What causes the input to go wrong?
How
oft
en d
oes
caus
e of
FM
oc
cur?
Process Step/Input
Potential Failure Mode
Potential Failure Effects Potential Causes
OCC
SEV
What are The causes?
FMEA step-by-step
List the current controls for each cause or failure mode (Prevent/Detect).
How are these Found or prevented?
Prevent Detect
Current Controls
What are the existing controls and procedures (inspection and test) that prevent/detect either
the Cause or Failure Mode? Should include an SOP number.
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
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
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
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
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
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
FMEA step-by-step
Determine recommended actions to reduce high RPN’s:
Ho
w w
ell
can
yo
u d
ete
ct
cau
se o
r F
M?
What are the actions for
reducing the occurrence of the
Cause, or improving
detection? Should have actions only on high RPN’s or
easy fixes.
Who is responsible for the
recommended action?
What are the completed actions
taken with the recalculated RPN?
Be sure to include
completion month/year.
DET
RPN
SEV
OCCResponsible Actions Taken
RPN
Actions Recommended
DET
What can be done?
FMEA step-by-step
Take appropriate actions and recalculate RPN’s
Ho
w w
ell
can
yo
u d
ete
ct
cau
se o
r F
M?
What are the actions for
reducing the occurrence of the
Cause, or improving
detection? Should have actions only on high RPN’s or
easy fixes.
Who is responsible for the
recommended action?
What are the completed actions
taken with the recalculated RPN?
Be sure to include
completion month/year.
DET
RPN
SEV
OCCResponsible Actions Taken
RPN
Actions Recommended
DET
Assign responsibleParties
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?
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