outline & introduction v3.2 [02]

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


TMC


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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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


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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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PRACTICAL TOLERANCING

A] Capturing DESIGN INTENT

B] Application

C] Interpretation

D] Drawing Practice

E] Gauging

F] Significant Characteristics


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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

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Design A Definition

The PHYSICALISATION

of the

IMAGINATION


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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.



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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.



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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


TMCTMC


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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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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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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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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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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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.



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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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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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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COMMUNICATIONS

Communications between

Human Beings is by means of

LANGUAGE


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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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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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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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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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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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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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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


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


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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


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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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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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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Complete Symbols

List

Items Marked #

are not described

in detail in this

course as they areself explanatory

outline & introduction v3.2 [02]

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