As9103 free download

Process Variations in
Support of

“Variation Management
of Key Characteristics”
Education Package – Based on Version

Company Confidential
Contents & Document Structure
 Introduction: Why manage variation?
 What is variation?
 Why manage variation?

 To know more about Key Characteristics

 What are Key characteristics ?
 Identifying Key Characteristics
 Benefits of identifying Key Characteristics
 Who, Why and How to determine Key Characteristics ?
 Approaches and tools to determine Key Characteristics

2
Contents & Document Structure -cont.
 presentation
 Scope of
 KC and applicability
 A seven stage process
 Stage 1 Understand Key Characteristics and Required
Performance
 Stage 2 Plan Manufacturing Processes
 Stage 3 Operate on Trial Basis to Generate Data
 Stage 4 Analyse data to identify appropriate Action and
 Stage 5 Take action from study (operate, re-design and
improve)
 Stage 6 Continue to Monitor the Performance
 Stage 7 Is a Process Change required ?
3
Contents & Document Structure -cont.
 presentation –cont.
 Summary and key factors of success
 Summary of actions
 stages in relation to First Article Inspection,
Process Reproducibility and PDCA cycle
 Key factors of success

4
Why manage variation?
What is variation?

 No two products or processes are exactly alike

 Variation exists because any process contains
many sources of variation
 The differences may be large or immeasurably
small, but always present
 Problems occur when the variation exceeds what
the customer expects

5
Why manage variations?
 Variation of some sort is responsible for all non-
conformances / customer dissatisfaction
 All non-conformances cost money, which reduces
investment, money available for pay rises,
potential to retain business
 By reducing variation it reduces the risk of non-
conformances and improves ease of assembly
 Process Control helps to identify:
 Different types of variation
 The amount of variation
 How well the process will meet customer requirements
 Once we know how much variation exists and the
source, we can take steps to reduce it

6
Why manage variations?
Why do we need to minimise product and
process variations?
 To enhance confidence that all your true stakeholder
expectations are met
 To continuously improve the overall business results
 To drive the continuous improvement of manufacturing
processes
 To reduce costs by eliminating wastes and unnecessary
efforts
 Levels of non conformances
 Fitting/adjustment/selective assembly
 Scraps and rework
 Inspection and verification
 Warranty claims
 To improve product performances and reliability

7
Why manage variations?
Why do we need to minimise product and process
variations?
• Reducing Variation allows to lower total
cost of acquisition while improving
stakeholder satisfaction

8
Why manage variations?
People generally believe that % is very good but…
For a country like USA, % equates to:
 1 hour of unsafe drinking water every month
 2 unsafe plane landings per day at O'Hare International Airport in Chicago
 16, pieces of mail lost by the U.S. Postal Service every hour
 20, incorrect drug prescriptions per year
 incorrect surgical operations each week
 50 newborn babies dropped at birth by doctors every day
 22, checks deducted from the wrong bank accounts each hour
 32, missed heartbeats per person per year
 76 newborn babies each month would be given to the wrong parents

Do you still believe that % is good

enough everywhere ? 9
9
Why manage variations?
Quality Planning Lever Customer takes possession
(Loss of control for Producer)
Inspection

Quality

Potential for non-conformance

non-conformance

Inspection is Receipt
necessary but not Reject Customer
sufficient Complaint Recall
Warranty
Investigation

10
Why manage variations?
Quality Planning Lever
Control of Product and Process Variation
Plan a method to Review and
achieve minimum improve the
variation process
Customer takes possession
Potential for non-conformance (Loss of control for Producer)
Run and
Understand
Customer
analyze QUALITY
the
requirements Inspection
process

Reducing process non-conformance

variation will reduce
cost of inspection 11
Why manage variations?
Impact of Product and Process Variation on Total
costs of acquisition

Increasing Do you know

quality where your
costs business is?

Failure costs

Appraisal costs
Prevention costs

Inspection costs
Prevention costs

Effective variation management

12
Why manage variations?
Managing product and process variations

Voice of
the Process
(VOP)

Voice of the
Customer
(VOC)

On Target with minimum variation 13

Why manage variations?

Possibility of
weight
reduction

Reduced
Tolerance

Example: Wall thickness

14
Why manage variations?

Reduce variation
of mechanical
properties

LSL= Lower Spec Limit Example: Tensile Strength

15
Why manage variations?

Less likelihood of
scrap or rework

Greater tolerance to nominal shift

Example: Reduce number of Quality issues
16
Why manage variations?
Process Capability versus Customer Satisfaction
Process Capability Product Performance Customer Satisfaction
- Awareness! +
Cost of unstable

Performance
process &/or excess
variation
•concession •Warranty claims
•scrap •Financial losses
•rework •Poor reliability
VOC
•poor performance •High cost of
•surpises ownership` •Business growth
Key Characteristic
•Enhanced reputation
•Customer delight

$
VOP

VOC
Part Engine Aircraft

Development Production

In-service 17
Do you know what Key Characteristics
are?

Which ones were missed?

18
What are Key Characteristics(KCs)?
• Definition : The feature of a material or part whose
variation has a significant influence on product fit,
performance, service life or manufacturability
– Key characteristic for a part, sub-assembly or system:
selected geometrical, material properties, functional and
cosmetic features which are measurable and whose
variation is necessary in meeting Customer
requirements
– Key characteristic for a process : selected measurable
parameters of a process whose control is essential
– Substitute Key characteristic : when Customer defined
key characteristic is not readily measurable and other
characteristic may need to be controlled

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What are Key Characteristics(KCs)?
 KCs are the variables whose attributes have the
greatest impact on the Customer Perspective
Key Characteristics
(Product or Process)
Impact on Quality

X3 X2 X6 X1 X4 X5

Product or Process Variables

20
What are Key Characteristics(KCs)?

CUSTOMER’S
REQUIREMENT:
GAP TO BLOCK X+/- y
KC

KC

KC

KC

NON-CRITICAL FEATURES

• Key Characteristics are the critical features at every

level of a product’s design, assembly and
manufacture necessary to satisfy the customer’s
requirements
21
What are Key Characteristics(KCs)?
• Product Characteristics
– Example: Aerodynamic
gap
• Assembly
Characteristics
– Example: Defined gap
between two panels KC

• Manufacturing
Characteristics
– Example: Wing skin
thickness

22
What are Key Characteristics(KCs)?
Example 1

23
What are Key Characteristics(KCs)?

 Example 2 KC

– Service-Life KC

Characteristics KC
KC

KC

 A KC of a cargo-door actuator is its expected time to failure (MTBF)

 This KC flows down to several part-level KCs, including the case depth and
case hardness of a nitralloy gear within the actuator
 Case depth and hardness are then flowed down to the KCs in the nitriding
process, which produces the case depth and hardness
 The KCs in this process are the nitriding temperature, the time at
temperature and the disassociation rate of ammonia during the nitriding
process
24
Benefits of Identifying KCs
 If KCs are properly identified and correctly controlled
 Products will have higher quality
 Losses will be reduced
 Costs will be cut
 Customers will be more satisfied

• Typically, around KCs is usual for an individual

component
• A larger number of KCs may be identified for a more
complex component or process

25
Who, Why and How to determine KCs ?
 The Customer (or the designer):
 What?: Key characteristic for:
 a part
 a sub-assembly
 a system
 Why?: He knows:
 the final Customer expectations
 the functional requirements for the part
 the sub-assembly on which it will be installed
 the historic data of similar parts in service, etc …
 How?: Mainly based on risk analysis methodology:
 Safety
 Performances
 Maintainability
 Reliability

26
Who, Why and How to determine KCs?
 The supplier (or the manufacturer):
 What?: Key characteristic for a process
 Why?: He understands
 his processes
Introduces
Business
 his tools improvement
 his manufacturing capabilities, and cost
 where he failed in the past savings
 where he is loosing money
 where his scrap rate is high
 where his Customer return rate is high, etc…
 How?: Mainly based on risk analysis methodology
 Reproducibility
 Variability

27
Who, Why and How to determine KCs ?

Key characteristics may be defined by the

producer even when the customer or the
designer has not defined them.

Use of should not be limited to

cases where Key Characteristics exist in
drawing

28
Approaches & Tools used to identify KCs
Integrated Product / Project Teams, Design Build Teams
Engineering
Customer / Functions Customer Manufacturing,
Who Design Quality Suppliers Safety Procurement
Sales (Aero, Support Assembly,
Stress, etc.) Tooling

Flight Performance Criteria Manufacturing Process Operational Service (Repairs,

Driver Safety (Aero, Stress, etc.) Variation Change Maintainability, etc.)

Historical Brainstorming Sessions

Risk Top Level Statistical Design of
Selection Analysis
Problem
Aircraft Variation Flowdown / DFMA Workshops /
Methods Areas / Data Experiments Specialists Experience
/ FMEA documents Analysis
Analysis

Identify Team

Identify Driver
Top Level Identify Zones and / or Parts
Process
Identify Design Configuration and / or Manufacturing and Assembly Processes

Identify Key Characteristics

Examples of Process
Geometric Electrical Properties, Material Properties, Mechanical Properties, Repair Criteria, property e.g.
Key Tolerances e.g. voltage e.g. hardness e.g. MTBF
e.g. torque temperature
Characteristics

Drivers, actors involved, selection methods, process and

KC selected may vary depending on the product and 29
should be fixed by each company. 29
Approaches & Tools used to identify KCs
 From Customer Needs to Key Characteristics: Existing
Advanced methods to determine KCs
 Voice of Customer (VOC)
 Critical to Quality (CTQ)
 Affinity Diagram
 QFD – Quality Function Deployment
 Functional analysis
 Risk analysis (FMEA Failure Modes and Effects Analysis)
 Etc

30
Approaches & Tools used to identify KCs
 Need to flow down KC for each package
Finished
Product
Customer
Final
Assembly

Part A Part B Part C Part D

KC KC
Product Product Product Product
Supplier Part A Part B Part C Part D
Process Process Process Process

Part CA Part CB
KC KC
Product Product

Suppliers N-1 Part CA Part CB

Process Process

Part CA Part CA
Suppliers N-2 Input
KC
Input

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Approaches & Tools used to identify KCs
 Different methods exist to identify Key Characteristics

Loss Function

Product, Process and

Problem Analysis

Historical Data Analysis

KCs
IDENTIFYING KEY
CHARACTERISTICS
Design of
FMEA Experimen
t
Statistical Variation Analysis Part
A
Proc
ess
Part
B
Proc
ess
Part
C
Proc
ess
Part
D
Proc
ess

Part Part
CA CB
KC KC
Produ Produ
ct ct

Part Part
CA CB
Proc Proc
ess ess

Part Part
CA KC CA
Input Input

Flow Down

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Scope of

•Establishes requirements for management

of key characteristics variation
• Specifies general requirements
• Provides a process

•Primarily intended to apply to new parts

but should also be applied through out
the life of the programme to ensure that
changes are taken into consideration

33
KC and applicability
 KCs clearly given by your
Customer (drawing and Use of is
specifications) a Requirement

 KC’s not identified by your

Customer:
 To identify Product KCs: Use of is a
 Working group involving Customer General
 In service experience (e.g. non Recommendation
quality analysis)
but may become
To identify Process KCs


In service experience (e.g. non

mandatory for
some critical


quality analysis)
 Internal issues (scrap rate, rework products or some
rate, etc…) contracts
 Cost and lead time reduction
 Risk analysis
34
 : A seven stages process

 - Variation Management of KCs

Stage Stage Stage Stage Stage Stage Stage

1 2 3 4 5 6 7
Yes
Take action
Plan a Operate Analyse
Understand from study Continue Is a
process that the data to
KCs and (operate, to monitor process
will produce process to identify
required re-design the change
acceptable generate appropriate
performance and performance required?
performance Data action
improve)
No

35
Stage 1 - Understand KCs and
Required Performance

Stage Stage Stage Stage Stage Stage Stage

1 2 3 4 5 6 7
Yes
Take action
Plan a Operate Analyse
Understand from study Continue Is a
process that the data to
KCs and (operate, to monitor process
will produce process to identify
required re-design the change
acceptable generate appropriate
performance and performance required?
performance Data action
improve)
No

36
Stage 1 - Understand KCs and
Required Performance
 Ownership of the process
Establish an appropriate cross-functional team :
 Design Engineering
 Manufacturing Engineering
 Process Operators
 Customers
 Component Definition
 Quality
Whoever has an input or
 Laboratory
is affected by your
 Inspectors
process
 Anyone else who is involved

The primary owner of the process is that group, department or

function that holds prime accountability for the development and 37
production of manufacturing methods (this is not only Quality) 37
Stage 1 - Understand KCs and
Required Performance
 An appropriate cross-functional team will allow
identifying all parameters and constraints

 Design Engineer: Potential design failure modes,

causes and effects
 Manufacturing Engineer: Process issues, potential
failures, causes and
effects
 Inspection Department: Definition of inspection methods
and criteria
 Buyer (Purchasing): Feedback from Supply Chain and
flow down of requirements
 Quality Engineer (Facilitator): Feedback from similar product,
customer returns, guarantee that
process is adequately followed
 Etc… It shall look at product, process & Customer requirements:
What does he want and how we can do it ?
38
Stage 1 - Understand KCs and
Required Performance
 An appropriate cross-functional team will allow
identifying all parameters and constraints
 Design Engineer: Potential design failure modes,
causes and effects
 Manufacturing Engineer: Process issues, potential
failures, causes and
effects
 Inspection Department: Definition of inspection methods
and criteria
 Buyer (Purchasing): Feedback from Supply Chain and
flow down of requirements
 Quality Engineer (Facilitator): Feedback from similar product,
customer returns, guarantee that
process is adequately followed
 Etc…
It shall look at product, process & Customer requirements:
What does he want and how we can do it ?
39
Stage 2 - Plan Manufacturing
Processes

Stage Stage Stage Stage Stage Stage Stage

1 2 3 4 5 6 7
Yes
Take action
Plan a Operate Analyse
Understand from study Continue Is a
process that the data to
KCs and (operate, to monitor process
will produce process to identify
required re-design the change
acceptable generate appropriate
performance and performance required?
performance Data action
improve)
No

40
Stage 2 -Plan Manufacturing Processes
 Identify key manufacturing
processes impacting key
characteristics
 Ensure process owner exist for
each key characteristic
 Establish a minimum acceptable
capability ratio (Cp, Cpk, …) for
each key characteristic
 Identify sources of variation and
potential risks… and mitigate them
 Relate process data back to what
designers want…
… and designers: Also understand
capability of manufacturing
Processes

41
Stage 2 -Plan Manufacturing Processes

 Process Control Document (PCD)

A written description of manufacturing plan

developed to control variation in KCs. It is a
living document and is updated to reflect the
addition/deletion of any KCs

42
Stage 2 -Plan Manufacturing Processes
PROCESS CONTROL DOCUMENT Page 2 of 2
Process Control Document Number Part Number / Latest Change Level Date (Original) Date (Rev)

•Process Control STAGE 3

Preliminary Process Capability Study -
STAGE 4
Results of Study
STAGE 5 STAGE 6
Action Ongoing Monitoring Methods

Document (PCD)
Type of from Control Chart/Other
CCF Stable Calculations
Control Capability
No. Y/N study
Hist / New Date Gauge Gauge # MSA % n Freq. Chart Mean Estimated St DevCp Cpk Y/N Type Frequency Review.

PROCESS CONTROL DOCUMENT Page 1 of 2

Process Control Document Number Process Owner Date (Original) Date (Rev) Flowchart Created?
Yes/No
Producer Approvals and Date Customer Approvals and Date
Part Name / Description Name: Name:

Producer / Plant Manufacturer Code Name: Name:

STAGE 1 STAGE 2
Conformance Control Feature Minimum Are Sources of Is Risks Mitigation
CCF No CCF Name Operation Work Instruction No. Requirement Origin of CCF Variation Identified? Specified?
Process ID Number /Change Level Yes/No Yes/No
Cp Cpk

Used to record
characteristics
and progress of
process

43
Stage 2 -Plan Manufacturing Processes
SIPOC = Supplier - Inputs - Process - Outputs - Customer

S I P O C
Process Process Process Process Process Process
OUTPUT
Step 1 Step 2 Step 3 Step 4 Step 5 Step 6

Identification of most contributing process steps

Identification of process KCs

Reduction of process KC variation

44
Efficient product KCs management is based on efficient Process KCs management
44
Stage 3 - Operate on Trial Basis to
Generate Data

Stage Stage Stage Stage Stage Stage Stage

1 2 3 4 5 6 7
Yes
Take action
Plan a Operate Analyse
Understand from study Continue Is a
process that the data to
KCs and (operate, to monitor process
will produce process to identify
required re-design the change
acceptable generate appropriate
performance and performance required?
performance Data action
improve)
No

45
Stage 3 - Operate on Trial Basis to
generate Data
Create Data collection plan for all
key characteristics (who, what,
PROCESS CONTROL DOCUMENT Page 2 of 2
Process Control Document Number Part Number / Latest Change Level Date (Original) Date (Rev)
ABC FK, Rev 14/03/01 28/08/01
STAGE 3 STAGE 4 STAGE 5 STAGE 6

Preliminary Process Capability Study - Results of Study Ongoing Monitoring Methods

Type of Action from
CCF ABC Stable Calculations Control Chart/Other
Control Study, Capability
No. Y/N
Hist / New Date Gauge Gauge # MSA % n Freq. Chart Mean Estimated St Dev Cp Cpk Y/N Type Frequency Review Freq.
PROCESS CONTROL DOCUMENT Page 1 of 2
1 New 14/03/ CMM 20 % xmR Yes Yes Comp 10% Quarterly
Process Control Document Number Process Owner Date (Original) Date (Rev) Flowchart Created?
ABC 2 Hist
Michael 14/03/
Edwards Micr 14/03/01
20% xmR
28/08/01 Yes
Yes/No No Manual 20% Quarterly
Producer Approvals and Date Customer Approvals and Date

where, frequency, conditions,…)

Part Name / Description Name: Name:
High Pressure Turbine Blade, Trent , FK M Engineer 25/08/01 T Rent 27/08/01
Producer / Plant Manufacturer Code Name: Name:
Rolls-Royce HPTB Facility,Derby TBF12 C Owner 26/08/01
STAGE 1 STAGE 2

Conformance Control Feature Minimum Are Sources of Is Risks Mitigation

CCF No Requirement Origin of CCF Variation Identified? Specified?
CCF Name Operation Work Instruction No.
Process ID Yes/No Yes/No
Number /Change Level Cp Cpk
1 L/E film cooling hole position EDM H Rev. 4 01/02/01 Manufacturer defined Yes Yes

and ensure you have a capable

measurement system
 Produce parts/components
to specified work
instructions in a
representative environment

Perform First Article Inspection (

Refers)
Measure key characteristics on a
sufficient number of parts and collect data
to document any deviations
46
Stage 3 - Operate on Trial Basis to
Generate Data

Capable Measurement System

“If it say’s 10 how do we
know if it’s 10 and not
or ”
Measurement Variation
Repeatability & Reproducibility
Gauge R&R
47
Stage 3 - Operate on Trial Basis to
Generate Data
 Why Worry About Measurement Variation?
Consider the reasons why we measure:
Verify product/ Assist in
process continuous
conformity to improvement
specifications activities
LSL USL* How might measurement variation
* affect these decisions?
Product What if the amount of
measurement variation is
unknown?
Measurement

Measurement variation can make our processes LOOK worse than they are

* LSL and USL: Lower and Upper Specification Limits

48
Stage 3 - Operate on Trial Basis to
Generate Data
 Measurement Unit Discrimination
The technological ability of the measurement systems
units to adequately identify variation in a measured
parameter
Ruler
Caliper
Micrometer

49
Stage 3 - Operate on Trial Basis to
Generate Data
 Measurement Accuracy
 Instrument accuracy is the difference between the
observed average value of measurements and the
master value. The master value is an accepted,
traceable reference standard.

Master Value
(Reference Standard)

Average Value

Calibration of gauges!
50
Stage 3 - Operate on Trial Basis to
Generate Data
 Measurement Linearity
 A measure of the difference in accuracy (bias) over the
range of instrument capability
 Over what range of values for a given characteristic can the
device be used?
 When the measurement equipment is used to measure a
wide range of values, linearity is a concern
Gauge 1 Gauge 2
Linearity is an issue here Linearity is not an issue here
..
..
Accuracy
.. . . . Accuracy
.. .. .
.. .
. . .
2 4 6 8 10 2 4 6 8 10

Measurement Range Measurement Range 51

Stage 3 - Operate on Trial Basis to
Generate Data
 Measurement Repeatability
 The variation between successive measurements
of the same part, same characteristic, by the same
person using the same instrument
Also known as test - retest error
Master Value

52
Stage 3 - Operate on Trial Basis to
Generate Data
 Measurement Reproducibility
The difference in the average of the measurements
made by different persons using the same or
different instrument when measuring the identical
characteristic Master Value
Inspector A

Inspector B

Inspector C
Inspector B
Inspector A

Inspector C

53
Stage 3 - Operate on Trial Basis to
Generate Data
Gauge Reproducibility & Repeatability (R&R) test
 Everybody measure the part using the Vernier

 Record the measurement (without letting anybody see it)

 Pass the part and Vernier to the next person

 Repeat?
Inspector B
Inspector A

Inspector C

Reproducibility Causes Repeatability Causes

54
Stage 3 - Operate on Trial Basis to
Generate Data
 Understanding Gauge R&R
 Repeatability and Reproducibility can be
expressed as a percentage of the drawing
tolerance used

 There are set of methods and formulas that work

this out! It doesn’t take long to do

• Ideally, we should not use more than 10% of the

available tolerance with measurement errors

55
Stage 3 - Operate on Trial Basis to
Generate Data
 First Article Review (Ref ) in relation to Key
characteristics (Stage 3)
 Adequate identification of Product and Process KCs and Capability of
processes and tools used to achieve KC’s shall be demonstrated at First
Article Inspection (FAI) review
 At New Product Introduction (NPI) producer shall ensure that FAI is
performed on a part that has been produced:
 According to specified work instructions that will be used in serial production
 In a representative environment, using scheduled Production means:
“ § Note 2 : The organisation shall not use prototype parts, or parts
manufactured using different methods from those intended, for the normal
process for the FAI”

PR
FAI Process