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8/8/2019 Outline & Introduction v3.2 [02]
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1Tony M Consulting Pty. Ltd
TMC
Tony M Consulting Pty. Ltd
TMCGEOMETRIC DIMENSIONING
& TOLERANCING
(GD&T)
Curriculum Outline
&
Introduction
2Tony M Consulting Pty. Ltd
TMC
Tony M Consulting Pty. Ltd
TMCPHILOSOPHY OF DESIGN
Roll of design Engineers in Industry
Engineering Structures
Cost Effective Design
How & Why things can Go Wrong
Function
Communications (Role of GD&T)
Myths
The Engineers Crutch
Conventions & National Standards
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3Tony M Consulting Pty. Ltd
TMC
Tony M Consulting Pty. Ltd
TMC
DATUM THEORY
What is a DATUM ?
3-Plane Concept.
Datum Features - Planes
- Cylinders
- Targets
Effect of Size & Form
Gauge/Inspection Datum Set-up
Practical exercises
4Tony M Consulting Pty. Ltd
TMC
Tony M Consulting Pty. Ltd
TMC
GEOMETRIC CHARACTERISTICS
Symbols (General Outline).
Detailed Discussion, application techniques,
Interpretations & practical exercises.
a) Flatness, Straightness, Roundness & Cylindricity
b) Profiles of Lines & Surfaces
c) Parallelism, Perpendicularity & Angularity
d) Runout, True Position, Concentricity & Symmetrye) True Position in depth
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5Tony M Consulting Pty. Ltd
TMC
Tony M Consulting Pty. Ltd
TMC
PRACTICAL TOLERANCING
A] Capturing DESIGN INTENT
B] Application
C] Interpretation
D] Drawing Practice
E] Gauging
F] Significant Characteristics
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TMC
Tony M Consulting Pty. Ltd
TMC
FMEA & GD&T
Co-ordination & interaction
WORKSHOP
Critique of drawings
Review of real examples from
your organization
Function Matrix
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T h e R o l e o f D e s i g n E n g i n e er s i n I n d u s t ry
The major function of a Design Engineer in Industry today is to Develop information
which permits an idea or concept to be converted into a physical object or system that
precisely meets the functions of that idea or concept.
The Design Engineer plays a pivotal role in manufacturing organizations
TMC
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TMC
Design A Definition
The PHYSICALISATION
of the
IMAGINATION
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TMC
Traditional:
The traditional structure in Manufacturing Industries is to have a special
Department with its own hierachy. This is further broken down into specialist engineering
functions, such a s Product D esign,Manufacturing E ngineering, Testing etc.
Engineering Structures
10Tony M Consulting Pty. Ltd
TMC
Tony M Consulting Pty. Ltd
TMC
Modern:
Engineers are incorporated into Multi-Functional teams with specific
project responsibilities. The teams usually have members with different disciplines, ie.
Engineers(their sub-disciplines are dependent on the project ), Manufacturing, Quality,
Marketing, Purchasing, Finance, MIS, etc.
Under this type of structure accountability is through the Team Leader
who may or may not be an Engineer.
The ability of the engineer to communicate accurately, under this structure is even
more demanding than in the traditional structure.
Engineering Structures
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TMC
Tony M Consulting Pty. Ltd
In order to be able to do his/her job properly the engineer mustbe trained to understand the following:
1) Laws of Physics as they apply to the concept
2) Mathematics
3) Mechanical systems, their functions & their environmental
limitations
4) Various materials available, their characteristics & applicability
5) Any Legal or other demands relevant to the application of the
concept
6) Costing
7) Testing methods
8) Performance evaluation techniques (statistics)
9) Manufacturing
10)Using TOOLS Effectively (eg. CAD)
11) Effective Engineering Communications
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TMCTMC
Tony M Consulting Pty. Ltd
An Engineers capability is measured according to how well he/she
applies that training to ensure that the resulting system efficiently
performs the idea/concepts function, ie,
SKILL
In order to demonstrate the above capability the Engineer must be
able to COMMUNICATE his/her system requirements in a way that
can be UNDERSTOOD
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13Tony M Consulting Pty. Ltd
TMC
Tony M Consulting Pty. Ltd
TMC C O S T E F F E C T I V ED E S I G N
Every COMPONENT drawing in whatever form has a cost
C SO KS IT L
L
No. Made No. Made
COST
SKILL
The above curves apply to all enterprises, whether producing components,
works of art or making component drawings.
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TMC
Tony M Consulting Pty. Ltd
TMC
There are many examples in the World which demonstrate that
poorly executed drawings/specifications of an excellent concept
will create a poor reputation for Manufacturing & Reliability in the
Market place,
While well executed drawings/specifications can make a
mediocre/conservative concept achieve an excellent reputation for
Manufacturing & Reliability etc. in the Market place.
Well executed Drawings/Specifications also minimize problems &
delays in the process from Concept to Production.
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TMC
Tony M Consulting Pty. Ltd
TMCThings That can Go Wrong
Common Problems in Manufacturing Industry
Example A
A component is submitted for Off Tool Sample approval & found not to perform
properly with its interacting components.
WHY ?
1) The component was not made to drawing because:-
a) The supplier made a mistake
b) The SupplierMis-interpreted the Drawing
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TMC
Tony M Consulting Pty. Ltd
TMCThings That can Go Wrong
Example A (contd)
2) The component was made to the Drawing BUT:-
a) The Engineer/Draughtsman made a mistake
b) The Engineer/Draughtsman putINCORRECTinformation on the
Drawing because he/she did not understand fully theFUNCTIONAL
RELATIONSHIP with its interacting components.
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TMCThings That can Go Wrong
Common Problems in Manufacturing Industry
Example B
A component is submitted for Off Tool Sample approval which(after an
extensive test program) was found to work satisfactorily with its interacting
components, although it does NOT CONFORM to the Drawing
WHY ?
1) The Supplier process was not capable of producing parts within the Specified
tolerance range & making changes to the tooling would jeopardise the cost &/or
the program timing.
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TMCThings That can Go Wrong
Example B (contd)
2) The Engineer/Draughtsman did not investigate the TRUE tolerance allowance
for the feature(s) because:-
a) He/she played safe in allocating the tolerance(s)
b) he/she did not understand/investigate the trueFUNCTIONAL
VARIABLES of the component with itsINTERACTING components.
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TMC
These examples are intended to illustrate some of the
problems that can affect a Companys relationship with a
Customer or the effective operations within the Company.
Highlighted are the effects of not understanding or using the
means of communication properly between Designers,
Engineers or Draughtsmen with those responsible for making
the Components/Assemblies.
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TMC
Error Detection Stage
Costo
fcorre
ction
Design Prototype Tooling Pilot Prodn. Serial Prodn. In Market Prod. Recall
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IMPORTANT!
Engineering drawings & specifications are LEGAL
DOCUMENTS
1] In respect to contract between Supplier &
Customer.
2] In respect to Product Liability issues that can
arise from the market place
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TMC
COMMUNICATIONS
Communications between
Human Beings is by means of
LANGUAGE
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TMC
To UNDERSTAND and, toensure that you convey the
true meaning of your
Feelings, Needs, Ideas etc., the
LANGUAGE MUST BE
LEARNED
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TMC
All languages have common attributes:-
SOUNDS are used to communicate feelings,needs, ideas etc. directly to another person or group
who understand thespoken language.
SYMBOLS are used to communicate feelings,
needs, ideas etc. to another person or group who areremote and understand the written language.
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TMC
WRITTEN communication is also NECESSARY
when continuous reference is required to ensure
that the information does not change from one
reading to the next.
Reliance on VERBAL communication used in
conveying PRECISE information can lead to many
mistakes & so be sources of conflict.
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TMC
Geometric Dimensioning & Tolerancing
System
-Is the Language that Engineers use to
communicate their requirements of a
component or an assembly so that the end
product meets the DESIGN INTENT-
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TMCWHY USE GEOMETRIC DIMENSIONING AND TOLERANCING?
Why is it that we should be so interested in this subject?
FIRST AND FOREMOST ITS USE SAVES MONEY!
It saves money directly by providing for maximum producibility of the
part through maximum production tolerances. It provides "bonus" or extra
tolerances in many cases.
It ensures that design dimensional and tolerance requirements, as they
relate to actual function, are specifically stated and thus carried out.
It adapts to, and assists, computerization techniques in design and
manufacture. It ensures interchangeability of mating parts at assembly.
It provides uniformity and convenience in drawing delineation andinterpretation, therebyreducing controversy and guesswork.
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TMC
Aside from the primary reasons stated before there are others of a more general nature:
The intricacies of today's sophisticated engineering design demand new and better ways of
accurately and reliably communicating requirements. Old methods simply no longer suffice.
Diversity of product line and manufacture makes considerably more stringent demands of
the completeness, uniformity, and clarity of drawings.
It is increasingly becoming the "spoken word" throughout industry, the military, and
internationally, on engineering drawings & documentation. Every engineer or technician
involved in originating or reading a drawing should have a working knowledge of this new
state of the art.
WHY USE GEOMETR IC DIMENSIONING AND TOLERA NCING?
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TMCFUNCTION
How do we define FUNCTION
There are TWO entities that require consideration from
an engineering aspect:
1) An ASSEMBLY (or Sub-assembly)
2) An individual COMPONENT
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TMC
1) An ASSEMBLY (or Sub-assembly)
An Assembly (or Sub-assembly) is a group of components that
are joined together and/or interact, such that for a given
physical INPUT manipulates that input to create an OUTPUT
which achieves a desired objective.
FUNCTION
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TMC
A COMPONENT is a single piece within an Assembly (or
Sub-assembly) that has essential characteristics/features
which interact with other components in order that the
Assembly (or Sub-assembly) can reliably perform its
design intent.
2) An Individual COMPONENT
FUNCTION
32Tony M Consulting Pty. Ltd
TMC Define the CONDITIONS & EXPECTATIONS for theFunctions
Environment
Corrosion Resistance
Temperature/Humidity
Ageing (Accelerated)
Life ExpectationNumber of Cycles
Fatigue
Critical Features
Interacting Features
Strength
Mass
Manufacturability
Customer
&
Legal Requirements
Specifications
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TMCFunction Loss Matrix
1) List all the Features of the Component/system/assembly.
3) Determine the Criticality/Severity Rating if those features are
OUTSIDE the Specification [L-Low, M-Medium or H-High]
6) Review the Matrix
Refer ISO/QS 9000 PPAP Manual
2) Indicate which features have a DATUM function
4) Indicate each features dependence [datum reference]
5) Indicate the control symbol(s) appropriate to each feature
34Tony M Consulting Pty. Ltd
TMC
Etc.
E
Width
D
Thickness
C
Hole
B
Hole
A
Surface
Sec.
Datum
Prim.
DatumShapePositionSizeTert.SeconPrim
Control SymbolCriticality RatingDatum
Feature
Design Function/Relationship Matrix
Component/Sub-Assy. Pt. No. (Dimensioning)
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TMCMYTHS
1) Using GD&T increases Cost !!
Proper use of GD&T reduces cost by MAXIMISING
the tolerances of features.
It is provable that the cost of production of a feature
increases according to the inverse of the size of the
tolerance
36Tony M Consulting Pty. Ltd
TMCMYTHS
2) Computer generated Data/Drawings are precise &
do not require additional information !!
Complex surfaces such as styled features must still be located
in a mechanical environment within an acceptable tolerance.
Eg. A instrument panel surface profile must be located so
that it fits properly in its environment so that the overallstyle of the interior of the vehicle meets the designers
intent.
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TMCMYTHS
3) GD&T can not be applied to all situations !!
GD&T is not just the use of a library of symbols, but a
LANGUAGE to communicate design intent.
If a situation occurs during the establishment of functional
requirement of a feature that is not covered by the standard
library then the requirement can be noted using the GD&T
principles to convey that requirement.
Use the GD&T language/vocabulary in a combination thattruly conveys the DESIGN INTENT
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TMC
What is the Engineers CRUTCH?
That note on the drawing that classifies the tolerance
according to the number of decimal points on the feature
dimension.
0 ---------- +/- 1 mm
0.0---------+/- 0.2 mm
0.00--------+/- 0.1 mm
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TMCWhat should we do instead?
2) Are there any formal standards that cover the function that is
required? Eg, Hole/shaft fits, Injection moulding tolerances,
codes of practice etc.
1) Refer to the Function Matrix for guidance to
evaluate the REAL tolerance requirement.
3) Consider how the feature will be Manufactured, &
what is the relative cost in Tooling & Piece cost.
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TMC
International Standards & Conventions
Agreement between US ANSI/ASME & ISO Standards covering
GD&T is about 90 95% .
Other national standards such as Australian Stds. Are generally
aligned with ISO.
Overall it can be considered that the GD&T language is
UNIVERSAL in its application & understanding. Ie, no matter whichethnic group needs to know what the designers intent is, can
understand, provided the GD&T language is understood.
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TMC Standards necessary for GD&T coverageANSI/ASME Y14.5M
The following documents must be considered when adopting ISO/GD&T standards
1. 15011101- Technical Drawings Geometrical tolerancing2. ISO/5458- Technical Drawings Positional tolerancing
3. ISO/5459- Technical Drawings Datums and Datum Systems
4. ISO/2692- Technical Drawings Maximum material principle
5. ISO/3040- Technical Drawings Cones
6. ISO/1660- Technical Drawings Profiles
7. ISO/129- Technical Drawings General principles
8. ISO/406- Technical Drawings Linear and angular dimensions
9. ISO/10578 Technical Drawings Projected tolerance zones
10. ISO/2692:1988/DAM 1 Technical Drawings Least material principle
11. ISO/8015 Technical Drawings Fundamental tolerance principle
12. ISO/7083 Technical Drawings Symbols proportions
13. ISO/10579 Technical Drawings Non-rigid parts
Additional 1S0 standards involved:1. ISO/1000 - SI Units
2. ISO/286 - Limits & Fits
3. ISO/TR5460 Technical Drawings-Verificat ion principles4. ISO/2768-2 General geometrical tolerances5. ISO/1302 - Surface Texture
6. ISO/2768-1 Tolerances for linear and angular dimensions
7. Other peripheral standards on screw threads, gears, drills, welding, etc., may alsobe required for coverage beyond Y 14.5 for product design.
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TMC
Complete Symbols
List
Items Marked #
are not described
in detail in this
course as they areself explanatory