gd&t01 introduction60

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Chapter1 1

Geometric Dimensioning &

Tolerancing

42 Slides ~1h


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Chapter1 2

Chapter 1. INTRODUCTION


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Chapter1 3

OBJECTIVE OF THIS PROGRAM:

Understand & use of Geometrical

Dimensioning & Tolerancing as specified by

ASME Y14.5-1994

For smooth integration into engineering

design systems (Specification)

Modern inspection

systems(Interpretation)


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Chapter1 4

Prerequisite for the Program:Adequate knowledge of reading of production

drawings

GD&T NTTF


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Chapter1 5

Introduction:

Geometric dimensioning and tolerancing (GD&T) is

a method for stating and interpreting design

requirements.

GD&T is an international system of symboliclanguage, and is simply another tool available to

make engineering drawings a better means of

communication from design through manufacturingand inspection.

GD&T NTTF


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Chapter1 6

GD&T NTTF

Advantages of GD&T:Uniformity in design practice

Fewer misinterpretations

Interchangeability Ensured

Design requirements specified explicitlyLatest gaging techniques accommodated

Lower production costs

Maximum tolerance allocationHigher production yields

Less rework or scrap


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Chapter1 7

Structure of Presentation:

Begins with basic principlesBuilds with applications-oriented concepts.

Complex material is presented

in a building-block approach with examplesillustrating each concept.

End-of-chapter evaluations further

reinforce the explanations given in each section..

Completely covers the material in ASME

Y14.5M-1994

(Some drawing examples are dimensioned and

toleranced in inches and some in millimeters)

GD&T NTTF


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Chapter1 8

GD&T NTTF

Structure of Presentation:Does not

Prescribe design or engineering practices

State design requirements

Specify inspection techniques


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Chapter1 9

GD&T NTTF

NOTE:

Sometimes it is necessary to state how

something is to be manufactured or inspected

(Cylinder Bore)

Drawings in this presentation are not

complete production drawings, but onlyillustrate the principles / concepts.


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Chapter1 10

GD&T NTTF

DRIVERS OF GD&T:

Demand for Products

Demand for Accuracy

Interchangeability

Globalization(Design anywhere)


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Chapter1 12

GD&T NTTF

.

GD&T:

Standardized Method for stating and

interpreting design requirements.

International system of symbolic language

Tool available to make engineering drawingsa better means of communication from design

through manufacturing and inspection.(Sri

Nagasamy)


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Chapter1 13

What is a Standard?

A model or Rule with which other similar things

are to be compared

Internationally applicable

To improve

CommunicationControl

Productivity

GD&T NTTF


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Chapter1 14

GD&T NTTF

Change:The most constant thing in society

Updation to make the standard useful to theindustry


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Chapter1 15

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WHY GD&T?Adds clarity to our coordinate system of

dimensioning

In Coordinate System, a part of the designer's

intent was always left to interpretation by the

craftsman (i.e., dimension origin, form profile and

orientation).


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Chapter1 16

WHY GD&T?

Most significant difference between the two

systems is the location of round features

Coordinate system had a square tolerance zone,

which allowed some good parts to be rejected

GD&T NTTF


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Chapter1 17

GD&T NTTF

GD&T IS NOT A REPLACEMENTThe coordinate system is not being replaced

entirely with GD&T.

GD&T is specified to enhance the coordinate

system as required by design.GD&T symbols, provide a means of completely

specifying uniformity and describing the designer's

intent.


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Chapter1 18

GD&T IS NOT A REPLACEMENT

Symbols eliminate most of the drawing

misinterpretation by not having notes in drawingmargins and by not having complete textual

descriptions of features and design requirements.

(Poka-Yoke)(XT - Brake part design)

GD&T NTTF


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Chapter1 19

GD&T NTTF

COMPLETE SPECIFICATION:

Complete specification of design requirementspossible with symbols

Symbols allow the designer to specify maximum

tolerances for parts that must assemble with otherparts.


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Chapter1 20

COMPLETE SPECIFICATION:

These maximum tolerances also ensure the

interchangeability of parts.

The use of symbols for complete specification is

becoming increasingly important with the

growing interrelated ownerships of companiesaround the world.

GD&T NTTF


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Chapter1 21

GD&T NTTF

ADVANTAGES:

Two key principles for applying GD&TFunction

Relationship of parts in an assembly.

Method of specifying feature location.


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Chapter1 22

ADVANTAGES:

In the past, features were located with the

coordinate system.

The coordinate system is a method of

Tolerancing that uses a plus/minus tolerance.

Plus and minus tolerances are specified forlengths, widths, diameters, shapes, and locations.

GD&T NTTF


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Chapter1 23

GD&T NTTF

Misinterpretation?


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Chapter1 24

GD&T NTTF

An illustration of how drawings

may be dimensioned and toleranced with thecoordinate system is shown in Figure 1-1.

This method of Tolerancing permits the length and

diameters to vary by a plus/minus value. It alsoallows the maker of the part to put the center hole

wherever he or she desires.

By looking at the drawing, we can only assume

that the hole is centered. This is an example of a

drawing being left open to misinterpretation by

anyone reading it.


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Chapter1 25

GD&T NTTF


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Chapter1 26

GD&T NTTF

An example of how holes are specified with the

coordinate system is shown in Figure 1-2.The tolerance as specified establishes a square

tolerance zone based on the plus/minus five

thousandths of an inch tolerance in the x and ydirections.

There is no consideration for the actual mating

size.

The tolerance zone is ten thousandths of an inch

on each side of square regardless of the actual

mating size.


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Chapter1 28

GD&T NTTF

Zone of Tolerance


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Chapter1 29

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Chapter1 30

Calculate the Loss of Tolerance field??

GD&T NTTF

Permitted zone of Tolerance

by Coordinate System

Permissible zone of Tolerance by Design Intent


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GD&T NTTF

Area of Square = (d / Sqrt2)**2

d

Area of Circle = ( / 4) d**2

150 %


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Chapter1 32

GD&T NTTF

An illustration of how the tolerance zone appears

is shown in Figure 1-3.

The axis of the hole or pin must be positioned in

that square zone in order for the feature to belocated properly.

The feature may lean or slant an uncontrolledamount as long as the axis stays within the square

zone.


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Chapter1 34

GD&T NTTF

That .007 should be usable all around the desired

true position, as illustrated in the example in Figure1-5.

GD&T provides a method of specifying atolerance zone that takes the shape of the feature

into consideration if so desired by the designer.

GD&T also allows consideration for the

feature's actual local size for calculating total

tolerance.


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Chapter1 35

The symbolic method of specifying design intent

eliminates most misinterpretation of drawingnotes.

The proper application of geometric tolerancesensures the interchangeability of parts.

GD&T NTTF


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Chapter1 36

GD&T NTTF

EXERCISE:

1. Drawings are the primary .tool

between designers and manufacturing.


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Chapter1 37

GD&T NTTF

ANSWERS FOR EXERCISE:

1. Drawings are the primary communicationtool

between designers and manufacturing.


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Chapter1 38

2. GD&T is a system made up of

...primarily

.

GD&T NTTF


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Chapter1 39

2. GD&T is a system made up ofsymbolsprimarily.

GD&T NTTF


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Chapter1 40

3. The GD&T standard is one of the standards

maintained by the .

GD&T NTTF


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Chapter1 41

3. The GD&T standard is one of the standards

maintained by the ASME.

GD&T NTTF


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Chapter1 42

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EXERCISE:

4. GD&T adds to the coordinate dimensioning

system and ensures of mating when specific

...is required.


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4. GD&T adds to the coordinate dimensioning

system and ensured of mating

when specificclarityis required.

GD&T NTTF


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5. GD&T does not . the

coordinate dimensioning and tolerancing system.

GD&T NTTF

GD&T NTTF


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GD&T NTTF


5. GD&T does not replace the coordinate

dimensioning and tolerancing system.

GD&T NTTF


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Chapter1 46

6. GD&T at best can be described as a

dimensioning and tolerancing

system.

GD&T NTTF

GD&T NTTF


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Chapter1 47

6. GD&T an best be described as a total

dimensioning and tolerancing system.

GD&T NTTF

GD&T NTTF


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Chapter1 48

GD&T NTTF

EXERCISE:7.GD&T is used to control the..

of a part feature and its relationship to other

features.

GD&T NTTF


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Chapter1 49

GD&T NTTF

ANSWERS FOR EXERCISE:7.GD&T is used to control the form of a part

feature and its relationship to other features.

GD&T NTTF


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Chapter1 50

8. GD&T is also used to control feature &

.

GD&T NTTF

GD&T NTTF


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Chapter1 51

8. GD&T is also used to control feature

size &

location

GD&T NTTF

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Chapter1 52

9. The key principles of GD&T are

. &

.

GD&T NTTF

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Chapter1 53

9. The key principles of GD&T are

Function&

Relationship.

GD&T NTTF

GD&T NTTF


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Chapter1 54

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EXERCISE:

10. Two advantages of the GD&T system aremaximum &

ensured of mating parts.

GD&T NTTF


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Chapter1 55

GD&T NTTF


10. Two advantages of the GD&T system aremaximum tolerances &

ensured interchangeabilityof mating parts.

GD&T NTTF


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Chapter1 56

11. The total amount that a part size may vary isa size..

GD&T NTTF

GD&T NTTF


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Chapter1 57

11. The total amount that a part size may vary

is a sizetolerance

GD&T NTTF

GD&T NTTF


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Chapter1 58

12. A common method used to specify a tolerance

for the nominal size of a feature is

.. values.

GD&T NTTF


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THANK YOU

gd&t01 introduction60

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