GD&T-MULTI METRICS

Copyright © 2004 - 2008 by Multi Metrics, Inc. Menlo Park, CA All Rights Reserved

by

Bill Tandler

A SmartGD&T Workshop

Spatial 3D Insider’s SummitBoulder 2008

GD&T Fundamentalsand potential Automation in

CAD/CAM/CAI

TM


Workshop Overview

1. What is GD&T?

2. The Perfect Imaginary World of GD&T

3. A GD&T Encoded Part

4. GD&T – Design, Mfg. & Metrology Connections

5. The Anatomy of a Feature Control Frame

6. Feature Control Frame Decoding

7. The Datum Reference Frame Establishment Process

SmartGD&T™


What is GD&T?

$

$ $

$ $


Many people think GD&T is


Grim, Depressing & Troublesome

Many people think GD&T is


and a fine way to waste a


and a fine way to waste a

Great Deal of Time


Others think GD&T is the


Greatest Design Tool

ever !

Others think GD&T is the


But in fact,


But in fact, GD&Tis the only tool we have for

managing imperfect geometry


perfectly!

But in fact, GD&Tis the only tool we have for

managing imperfect geometry


Purpose of GD&T


Most people would say . . .

The main purpose of GD&T is to communicate Design intent unambiguously to manufacturing and inspection.

Purpose of GD&T


The primary purpose of GD&T, is to ensure that what we communicate to manufacturing and inspection is worth communicating, namely represents functional, assemblable parts.

but in fact . . .

Purpose of GD&T


Or, in greater detail . . .


GD&T is a symbolic language for



1. researching



1. researching2. refining and



1. researching2. refining and3. encoding

the function of each feature of a part in Design,




the function of each feature of a part in Design,in order - through decoding - to





1. guarantee assemblability and operability prior to drawing release

in order - through decoding - to






2. set reduce cost and set precise objectives for manufacturing, and







2. set reduce cost and set precise objectives for manufacturing, and

3. turn inspection and manufacturing process feedback into truly scientific processes



In fact,without GD&T


1. Reliable Tolerance Stack-Up Analysis is impossible . . .




2. Manufacturing is a guessing game based on tribal understandings . . .




2. Manufacturing is a guessing game based on tribal understandings . . .

3. All inspection is pure invention on the part of the inspector.



A question . . .


Did you notice the use of the words

“encoding” and “decoding”

?


Another question . . .


Have you ever asked two or three colleagues for help

“interpreting”GD&T ?


. . . and gotten two or three




. . . and gotten two or three

“different interpretations”

?




Surely if GD&T is used to decorate drawings for later

“interpretation”




it is useless!


$

$

$and because machine shops know that most GD&T is purely decorative, they have to charge more to cover the cost of ensuring that their interpretations are in

line with those of their customers.



it is useless!


Now for some insights into


The Simplicitybut

Uselessness of CD&T

(Classical Dimensioning &Tolerancing)

Now for some insights into


The Classical tool kitconsists of only one tool, namely the

toleranced nominal dimension 50 ± 1

But is one tool enough?Ø20±0.2 Ø30±0.2

18±0.1

25±0.1

15±0.1

45±1

45±0.5

140±0.5

45±0.145±0.1

Ø16.5±0.2

25±130±0.5


Although perfectly capable of controlling size, the classical alternative . . .

Technical Disadvantages of Classical Tolerancing

Ø20±0.2 Ø30±0.2

18±0.1

25±0.1

15±0.1

45±1

45±0.5

140±0.5

45±0.145±0.1

Ø16.5±0.2

25±130±0.5


1) does not clearly define coordinate systems, 2) does not differentiate between reference and controlled features,3) controls the location of bores with square instead of round tolerance zones,4) provides no means of linking location tolerances to feature size,5) provides no means for controlling compound curved surfaces,6) provides no means for managing feature form,7) provides no means for researching and refining part functionality, and8) provides no means for guaranteeing the assemblability of mating parts.

Although perfectly capable of controlling size, the classical alternative . . .

Technical Disadvantages of Classical Tolerancing

Ø20±0.2 Ø30±0.2

18±0.1

25±0.1

15±0.1

45±1

45±0.5

140±0.5

45±0.145±0.1

Ø16.5±0.2

25±130±0.5


Classical Tolerancing leaves us beholden to

Tribal Understandings&

Interpretation

As a result . . .


How does GD&T compare ?


The Frustrationsand

Power of GD&T

(Geometric Dimensioning &Tolerancing)


GD&T Frustrations

1. GD&T is Complex.

2. GD&T is Sporadically used.

3. GD&T is often used to “decorate” drawings, rather than “encode” function.

4. GD&T is often “interpreted” rather than “decoded”.


GD&T Opportunities

1. GD&T encourages fault tolerant designs and can guarantee assemblability.

2. GD&T reduces Mfg. cost through unambiguous communication and looser tolerances.

3. GD&T turns 3D Metrology into a reliable, scientific process for the first time.


The GD&T tool kit

A

45

40

25 18

CB

A


The GD&T tool kit

A

45

Geometry Control Tools

40

25 18

CB

A


The GD&T tool kit

A

45

Geometry Control Tools Feature Control Frames

40

25 18

CB

A


The GD&T tool kit

A

45

Geometry Control Tools Feature Control FramesBasic Dimensions, and

40

25 18

CB

A


The GD&T tool kit

A

45

Geometry Control Tools Feature Control FramesBasic Dimensions, andDatum Feature Labels

40

25 18

CB

A


1) clearly defines coordinate systems, 2) clearly differentiates between reference and controlled features,3) controls the location of bores with cylindrical tolerance zones,4) links location tolerances to feature size using (M) and (L) Modifiers5) provides powerful tools for controlling compound curved surfaces,6) provides powerful tools for managing feature form,7) provides powerful means for researching and refining part functionality, and8) through tolerance stack-up analysis, makes it possible to guarantee assemblability.

GD&T is perfectly capable of controlling size, and . . .

Technical Advantages of GD&T

15

25

4545

D

A

45

25

E

ALL OVER

30

25

B

C

45


GD&T liberates us from

Tribal Understandings&

Interpretation

As a result . . .


Now for some

Fundamental GD&T Concepts


The Perfect

Imaginary World

of GD&T

Let’s take a closer look at


The Perfect Imaginary World of GD&T



1. Tolerance ZonesBounded regions of space within which a particular component of a feature is required to lie.







Tube-like




Tube-likeCylindrical




Tube-like

Slab-like

Cylindrical




2. Tolerance ValuesThe sizes of tolerance zones.

Tube-like

Slab-like

Cylindrical





Wall ThicknessTube-like

Slab-like

Cylindrical





Wall ThicknessDiameter

Tube-like

Slab-like

Cylindrical



Width




Tube-like

Slab-like

Cylindrical




Width

Tube-like

Slab-like

Cylindrical1. Tolerance ZonesBounded regions of space within which a particular component of a feature is required to lie.


3. Datums Perfect imaginaryreference points, lines and planes.





3. Datums Perfect imaginaryreference points, lines and planes.


Width

Tube-like

Slab-like

Cylindrical





3. DatumsReference points, lines and planes.

4. Coordinate SystemsFrames of reference for orienting and locating tolerance zones.


Width

Tube-like

Slab-like

Cylindrical


Y X

Z







Width

Tube-like

Slab-like

Cylindrical



Y X

Z





5. Basic DimensionsTools for orienting and locating tolerance zones.


Width

Tube-like

Slab-like

Cylindrical


50 70


Y X

Z







Width

Tube-like

Slab-like

Cylindrical


50 70


Y X

Z






6. A symbolic LanguageSets of Geometry Control Tools for imposing the perfect imaginary world on the imperfect real world.


Width

Tube-like

Slab-like

Cylindrical


50 70


Y X

Z

Diameter ToolPosition Tool

Cylindricity Tool


Width

Tube-like

Slab-like

Cylindrical1. Tolerance ZonesBounded regions of space within which a particular component of a feature is required to lie.





6. A symbolic LanguageSets of Geometry Control Tools for imposing the perfect imaginary world on the imperfect real world.


Now let’s put it all to work . . .


Here’s a partially GD&T encoded drawing, . . .



B

C

25

A

50

50


Datum Feature Labels

B

C

25

A

50

50



Datum Feature Labelsidentify the functionally most important features of a part.

B

C

25

A

50

50



Geometry Control Tools

B

C

25

A

50

50



Geometry Control Toolscontrol the size, form, orientation and

location of part features

B

C

25

A

50

50



Feature Control Frames

B

C

25

A

50

50



Feature Control Frames specify tolerance zones and

coordinate systems

B

C

25

A

50

50



B

C

25

A

50

50

In Particular



coordinate systems


B

C

25

A

50

50

In Particular


Tolerance Zone Shape


coordinate systems


B

C

25

A

50

50


coordinate systems



Tolerance Zone Size

In Particular


B

C

25

A

50

50


coordinate systems


Tolerance Zone ShapeCoordinate System Establishment Instructions

Tolerance Zone Size

In Particular


Basic Dimensions

B

C

25

A

50

50



Basic Dimensionslocate tolerance zones

B

C

25

A

50

50



B

C

25

A

50

50

. . . and here’s the actual part, . . .


X(A,B,C)Z(A,B,C)

25

50

Y(A,B,C)

50

B

C

25

A

50

50

. . . and here are the GD&T defined Tolerance Zones !


X(A,B,C)Z(A,B,C)

25

50

Y(A,B,C)

50

B

C

25

A

50

50

A slab-like Flatness

Tolerance Zone



X(A,B,C)Z(A,B,C)

25

50

Y(A,B,C)

50

B

C

25

A

50

50

A slab-like Perpendicularity Tolerance Zone



X(A,B,C)Z(A,B,C)

25

50

Y(A,B,C)

50

B

C

25

A

50

50

A tube-like Diameter

Tolerance Zone



X(A,B,C)Z(A,B,C)

25

50

Y(A,B,C)

50

B

C

25

A

50

50

A cylindrical Position

Tolerance Zone



Now a quick overview of

The GD&T – Design Connection



The GD&T – Design Connection

1. Encourages aggressive feature function analysis

2. Encourages fault tolerant design

3. Supports truly Functional Datum Feature selection

4. Requires effective Geometry Control Tool selection

5. Encourages balanced Tolerance value selection to guarantee Operability, Assemblability & Manufacturability

6. Permits truly functional Tolerance Stack-Up Analysis (TSUPA™) to guarantee functionality prior to model release

Important Concepts & Processes



The GD&T – Manufacturing Connection



The GD&T – Manufacturing Connection

1. Enables reliable manufacturing process planning through unique Feature Control Frame decoding

2. Permits aggressive Design feedback on questionable call-outs

3. Requires religious use of specified Datum Features where possible

4. Allows use of Temporary Datum Features where necessary

5. Enables scientific manufacturing process quality assessment




The GD&T – Metrology Connection



The GD&T – Metrology Connection


1. Completely defines CMM based inspection processes through potentially fully automated Feature Control Frame decoding

2. Essentially automates Functional Gage design

3. Requires adequate raw data point cloud densities

4. Requires adequate raw data accuracy – at least 20X the tightest tolerance value

5. Permits fully automated Rule based Datum Reference Frame establishment

6. Enables strict, Rule based Actual Value processing


Clearly Functional GD&T is essential for reliable manufacturing and metrology processes

Clearly

bad GD&Tis nothing but trouble !


Primary Focuses in this presentation:


1. Feature Control Frame Anatomy

2. Material Condition Modifier clarifications

3. Feature Control Frame decoding

4. Datum Feature, Datum Feature Simulator and Datum definitions

5. Rules for Datum Feature Simulation and Datum Reference Frame establishment

6. The Datum Reference Frame establishment Process.

Primary Focuses in this presentation:


Let’s start with the

Anatomyof a

Feature Control Frame


Feature Control Frame Anatomy



Ø0.5 M A B S C M

Feature Control Frames have three major compartments



Ø0.5 M A B S C M

Feature Control Frames have three major compartments



1. Specifies the Geometry Control Tool

Ø0.5 M A B S C M



2. Specifies the Tolerance Zone

Ø0.5 M A B S C M




3. Specifies the Datum Reference Frame Establishment Process

Ø0.5 M A B S C M





Ø0.5 M A B S C M








Tolerance Zone Size

Ø0.5 M A B S C M







Tolerance Zone Size

Ø0.5 M A B S C M

Tolerance Zone Size Modifier






PrimaryDatum Feature

Ø0.5 M A B S C M



Tolerance Zone Size







SecondaryDatum Feature

Ø0.5 M A B S C M



Tolerance Zone Size








TertiaryDatum Feature

Ø0.5 M A B S C M



Tolerance Zone Size







Tolerance Zone Mobility Modifiers



TertiaryDatum Feature

Ø0.5 M A B S C M


Tolerance Zone Size





Ø0.5 M A B S C M

Material Condition Modifier Effects

Tolerance Zone SizeModifiers Ø25±1


Ø0.5 M A B S C M


Tolerance Zone SizeModifiers

Impact on the Tolerance Zone The Encoded Function

Ø25±1


Ø0.5 M A B S C M



M

Impact on the Tolerance Zone

M ore tolerance

The Encoded Function

Ø25±1


Ø0.5 M A B S C M



M


M ore tolerance


Clearance

Ø25±1


Ø0.5 M A B S C M



M

L


M ore tolerance

L ots of tolerance


Clearance

Ø25±1


Ø0.5 M A B S C M



M

L


M ore tolerance

L ots of tolerance


Clearance

Interference / Overlap

Ø25±1


Ø0.5 M A B S C M



M ore tolerance

L ots of tolerance

S tuck at 0.5 mm

M

L

S


Clearance


Ø25±1


Ø0.5 M A B S C M



M ore tolerance

L ots of tolerance

S tuck at 0.5 mm

M

L

S


Clearance


Centering / Aiming

Ø25±1


Ø0.5 M A B S C M



Impact on Manufacturing

Ø25±1


Ø0.5 M A B S C M



Encourages pushing features toward their LMC !M

Ø25±1



Ø0.5 M A B S C M



Encourages pushing features toward their LMC !M

L

Ø25±1


Encourages pushing features toward their MMC !


Ø0.5 M A B S C M



M

L

S

Ø25±1


Encourages pushing features toward their LMC !

Encourages pushing features toward their MMC !

Encourages keeping features at their mean sizes !


Ø0.5 M A B S C M



Impact on Coordinate Metrology

Ø25±1


Ø0.5 M A B S C M




Ø25±1

M Requires determining the unconstrained, in-space actual mating size of a feature to expand the Tol Zone


Ø0.5 M A B S C M




Ø25±1

M

L

Requires determining the unconstrained, in-space actual mating size of a feature to expand the Tol Zone

Requires determining the unconstrained, in-material actual mating size of a feature to expand the Tol Zone


Ø0.5 M A B S C M



Easy to implement, because there is nothing to do !

M

L

S


Ø25±1

Requires determining the unconstrained, in-space actual mating size of a feature to expand the Tol Zone

Requires determining the unconstrained, in-material actual mating size of a feature to expand the Tol Zone


Tolerance Zone MobilityModifiers

Ø0.5 M A B S C M


Ø25±1



Ø0.5 M A B S C M


Impact on the DRF & Tolerance Zone The Encoded Function

Ø25±1



Ø0.5 M A B S C M

M



Ø25±1

M obilizes the tolerance zone



Ø0.5 M A B S C M

M



{ Mating Part play due to in-space clearance

Ø25±1




Ø0.5 M A B S C M

M



{

Ø25±1


This will be demonstrated in the application at the end of the workshop!

Mating Part play due to in-space clearance



Ø0.5 M A B S C M

M

L



{

Ø25±1


L oosens the tolerance zone




Ø0.5 M A B S C M

M

L



Mating Part play due to in-material overlap

{

{

Ø25±1






Ø0.5 M A B S C M



S tabilizes the tolerance zone

M

L

S



{

{

Ø25±1





Ø0.5 M A B S C M

M

L

S



Mating Part centering

{

{

{

Ø25±1



S tabilizes the tolerance zone





Ø0.5 M A B S C M


Impact on the Datum Feature Simulators

Ø25±1



Ø0.5 M A B S C M



Ø25±1

M M Fixes the size of the Simulator at the Virtual Maximum Material Boundary



Ø0.5 M A B S C M



Ø25±1

L

M

L

M Fixes the size of the Simulator at the Virtual Maximum Material Boundary

Fixes the size of the Simulator at the Virtual Least Material Boundary



Ø0.5 M A B S C M

SS



Ø25±1

L

M

L

Fixes the size of the Simulator at the Virtual Maximum Material Boundary

Fixes the size of the Simulator at the Virtual Least Material Boundary

M

Requires the Simulator to expand or contract to consume all the available space



Ø0.5 M A B S C M



Ø25±1



Ø0.5 M A B S C M


Ø25±1


Encourages pushing Datum Features toward their LMC. M should always be treated as S for set-upM



Ø0.5 M A B S C M


Ø25±1


M

L

Encourages pushing Datum Features toward their LMC. M should always be treated as S for set-up

Encourages pushing Datum Features toward their MMC. L should always be treated as S for set-up



Ø0.5 M A B S C M


Ø25±1


Encourages keeping Datum Features at their mean sizes

M

L

S

Encourages pushing Datum Features toward their LMC. M should always be treated as S for set-up

Encourages pushing Datum Features toward their LMC. L should always be treated as S for set-up



Ø0.5 M A B S C M



Ø25±1



Ø0.5 M A B S C M


M

L


Ø25±1

Present significant problems for CMM software and raise the specter of theRule of Simultaneous Requirements !

&



Ø0.5 M A B S C M


S


Easy to implement, because there is nothing to do !

M

L

Present significant problems for CMM software and raise the specter of theRule of Simultaneous Requirements !

Ø25±1

&


Here’s an interesting question !


Feature Control Frame Types ?

Compound Composite

What’s the difference between these two



Compound Composite


It’s huge and very simple:



Compound Composite


The differences are described on pp. 93–133 in the ASME Y14.5M 1994 Standard . . .




Compound Composite


The differences are described on pp. 93–133 in the ASME Y14.5M 1994 Standard . . .


. . . but can be condensed into


Composite Feature Control Frames

Compound Composite

The Rule of


Compound Composite

The Datum Features in the second and all lower tiers of a Composite Feature Control Frame may only constrain rotational degrees of freedom ! (Y14.5M 1994 – pp. 93-133)

Composite Feature Control FramesThe Rule of


Decoding GD&T

Now we’ll illustrate the process of


But first let’s do the

“Quick Read”


Reading the Feature Control Frame.


Position -



Position - within a diameter of 0.5 mm



Position - within a diameter of 0.5 mm at MMC -



Position - within a diameter of 0.5 mm at MMC - relative to A



Position - within a diameter of 0.5 mm at MMC - relative to A, B



Position - within a diameter of 0.5 mm at MMC - relative to A, B regardless of feature size,



Position - within a diameter of 0.5 mm at MMC - relative to A, B regardless of feature size, and C



Position - within a diameter of 0.5 mm at MMC - relative to A, B regardless of feature size, and C at Maximum Material Condition.



Now, let’s

Decode

it!


Position requires

Decoding the Feature Control Frame.


Position requires the bounded axis of the Considered Feature



Position requires the bounded axis of the Considered Feature to lie within a cylindrical tolerance zone



Position requires the bounded axis of the Considered Feature to lie within a cylindrical tolerance zone of diameter 0.5 mm



Position requires the bounded axis of the Considered Feature to lie within a cylindrical tolerance zone of diameter 0.5 mm at MMC -



Position requires the bounded axis of the Considered Feature to lie within a cylindrical tolerance zone diameter of 0.5 mm at MMC - expanding by as much as 1 mm



Position requires the bounded axis of the Considered Feature to lie within a cylindrical tolerance zone diameter of 0.5 mm at MMC - expanding by as much as 1 mm as the Unconstrained Actual Mating size of the Considered Feature departs from MMC toward LMC -



- which is oriented and located by BASIC dimensions -



- which is oriented and located by BASIC dimensions - relative to a Datum Reference Frame established using




Y[A,B,C]

Z[A,B,C]

Y[A,B,C]

X[A,B,C]



Y[A,B,C]

Z[A,B,C]

Y[A,B,C]

X[A,B,C]

- which is oriented and located by BASIC dimensions - relative to a Datum Reference Frame established using Datum Feature A,



- which is oriented and located by BASIC dimensions - relative to a Datum Reference

Frame established using Datum Feature A, simulated rocking,

Y[A,B,C]

Z[A,B,C]

Y[A,B,C]

X[A,B,C]



Y[A,B,C]

Z[A,B,C]

Y[A,B,C]

X[A,B,C]

- which is oriented and located by BASIC dimensions - relative to a Datum Reference Frame established using Datum Feature A, simulated rocking, Datum Feature B,




simulated stably, regardless of its size,

Y[A,B,C]

Z[A,B,C]

Y[A,B,C]

X[A,B,C]



Y[A,B,C]

Z[A,B,C]

Y[A,B,C]

X[A,B,C]

- which is oriented and located by BASIC dimensions - relative to a Datum Reference Frame established using Datum Feature A, simulated rocking, Datum Feature B, simulated stably regardless of its size, and Datum Feature C,




simulated stably, regardless of its size, and Datum Feature C, simulated mobly at its Virtual Maximum Material Condition size.

Y[A,B,C]

Z[A,B,C]

Y[A,B,C]

X[A,B,C]



Got it?One more time !


Position requires



Position requires the bounded axis of the Considered Feature



Position requires the bounded axis of the Considered Feature to lie within a cylindrical tolerance zone



Position requires the bounded axis of the Considered Feature to lie within a cylindrical tolerance zone of diameter 0.5 mm



Position requires the bounded axis of the Considered Feature to lie within a cylindrical tolerance zone of diameter 0.5 mm at MMC -



Position requires the bounded axis of the Considered Feature to lie within a cylindrical tolerance zone diameter of 0.5 mm at MMC - expanding by as much as 1 mm



Position requires the bounded axis of the Considered Feature to lie within a cylindrical tolerance zone diameter of 0.5 mm at MMC - expanding by as much as 1 mm as the Unconstrained Actual Mating size of the Considered Feature departs from MMC toward LMC -



- which is oriented and located by BASIC dimensions -







Y[A,B,C]

Z[A,B,C]

Y[A,B,C]

X[A,B,C]



Y[A,B,C]

Z[A,B,C]

Y[A,B,C]

X[A,B,C]

- which is oriented and located by BASIC dimensions - relative to a Datum Reference Frame established using Datum Feature A,



- which is oriented and located by BASIC dimensions - relative to a Datum Reference

Frame established using Datum Feature A, simulated rocking,

Y[A,B,C]

Z[A,B,C]

Y[A,B,C]

X[A,B,C]



Y[A,B,C]

Z[A,B,C]

Y[A,B,C]

X[A,B,C]





simulated stably, regardless of its size,

Y[A,B,C]

Z[A,B,C]

Y[A,B,C]

X[A,B,C]



Y[A,B,C]

Z[A,B,C]

Y[A,B,C]

X[A,B,C]

- which is oriented and located by BASIC dimensions - relative to a Datum Reference Frame established using Datum Feature A, simulated rocking, Datum Feature B, simulated stably regardless of its size, and Datum Feature C,




simulated stably, regardless of its size, and Datum Feature C, simulated mobly at its Virtual Maximum Material Condition size.

Y[A,B,C]

Z[A,B,C]

Y[A,B,C]

X[A,B,C]



With decoding in hand, we’re ready to investigate the

Datum Reference FrameEstablishment Process


We’ll use the indicated Datum Features . . .


We’ll use the indicated Datum Features . . .


We’ll use the indicated Datum Features and their Tolerance Zone Mobility Modifiers


We’ll use the indicated Datum Features and their Tolerance Zone Mobility Modifiers


We’ll use the indicated Datum Features and their Tolerance Zone Mobility Modifiers to establish the specified Datum reference Frame !



Y[A,B,C]

Z[A,B,C]

Y[A,B,C]

X[A,B,C]



Y[A,B,C]

Z[A,B,C]

Y[A,B,C]

X[A,B,C]

And discover how the modifier M leads to



Y[A,B,C]

Z[A,B,C]

Y[A,B,C]

X[A,B,C]

And discover how the modifier M leads to

Tolerance Zone Mobility


Concepts

Foundations for establishing a Datum Reference Frame


1. Datum Features

2. Datum Targets

3. Datum Feature Simulators

4. Datums

Concepts



Concepts

Tools


1. Datum Features

2. Datum Targets


4. Datums


Concepts

1. Datum Feature Labels

2. Tolerance Zone Mobility Modifiers

3. Feature Control FramesTools


1. Datum Features

2. Datum Targets


4. Datums


Concepts





Rules

1. Datum Features

2. Datum Targets


4. Datums


Concepts





Rules 1. Rules of Datum Feature Simulator Management

2. Rules of Natural Datum Reference Frame Establishment

1. Datum Features

2. Datum Targets


4. Datums


Concepts







Details1. Datum Features

2. Datum Targets


4. Datums


Datum FeaturesDefinition:



Datum Features are specially labeled, imperfect, physical surfaces of real parts, which serve to constrain degrees of rotational and translational freedom during assembly processes.


40

25 18

CB

A



A is a Planar Surface


40

25 18

CB

A




B is a Bore


40

25 18

CB

A

Datum Features


B is a Bore

C is a Slot

Definition:



Datum Targets

Definition:


Datum Targets

Definition:

Datum Targets are limited portions of Datum Features:

which encode the fact that the mating Datum Feature, assembly or manufacturing fixture, will only engage the indicated, limited portions of the Datum Feature under consideration.

• Points• Lines• Limited Areas


Datum Targets

SØ10A2

40

SØ10

A3

A

40

500

SØ10SØ10

SØ10SØ10

A1

0

50

A1

A2

A2

A2


Datum Targets

Point Datum Targets A1, A2 and A3 are to be simulated by spherical simulators of dia. 10mm

SØ10A2

40

SØ10

A3

A

40

500

SØ10SØ10

SØ10SØ10

A1

0

50

A1

A2

A2

A2


Datum Feature Simulators

Definition:



Definition:

Datum Feature Simulators are conceptually perfect, or physically almost perfect, inverse Datum Features,



1. from which we extract Datums

Definition:





2. in which we establish Datum Reference Frames, and

Definition:






3. with which we transfer Datum Reference Frames to actual parts.

Definition:







Definition:


The machining fixtures and gages used in manufacturing and inspection processes are examples

of physical Datum Feature Simulators.






Definition:


Mathematical Datum Feature Simulators are constructed by Coordinate Measuring Machine

software systems during Datum Reference Frame establishment procedures.


Datum Feature Simulator Details


40

25 18

CB

A

Datum Feature A: a Planar Surface



40

25 18

CB

A

18

16

Datum Feature Simulator A:an inverse Planar Surface




Datum Target Simulator Details


SØ10A2

40

SØ10

A3

A

40

500

SØ10SØ10

SØ10SØ10

A1

0

50

A1

A2

A2

A2

Point Datum Targets A1, A2 and A3



SØ10A2

40

SØ10

A3

A

40

500

SØ10SØ10

SØ10SØ10

A1

0

50

A1

A2

A2

A2

16

18

Datum Target Simulators A1, A2 and A3:Three Tooling Balls

Point Datum Targets A1, A2 and A3



40

25 18

CB

A

Datum Feature B: a Bore



40

25 18

CB

A

18

16

Datum Feature Simulator B:an expanding Cylinder

Datum Feature B: a Bore

S



40

25 18

CB

A

Datum Feature C: a Slot



40

25 18

CB

A

18

16


Datum Feature Simulator C:A fixed “Tombstone”


M


Datums

Definition:


Datums

Definition:

Datums are the minimum set of one perfect imaginary reference point, and/or straight line, and/or plane, which together, fully characterize the orientation and location of a datum feature simulator.


Pointon-Line

Line

Point

Linein-Plane

Pointon-Linein-Plane

Degrees of Constraint Capability

Pitch Yaw Roll Translation

Plane

Note 1.

Planar Surface Slab

Compound Curved Surface

Wedge Cyl. Pattern

Cone Torus

Sphere

Cylinder

Datum Feature Simulator DFS + Datum Datum Datum Type Rx Ry Rz Tx Ty Tz

Datum Feature Simulators & Datums


Datum Details


40

25 18

CB

A

Datum Details



Datum A: the tangent plane onDatum Feature Simulator A

40

25 18

CB

A

Datum Details



Datum Details for Datum Targets

SØ10A2

40

SØ10

A3

A

40

500

SØ10SØ10

SØ10SØ10

A1

0

50

A1

A2

A2

A2Datum Targets A1, A2 and A3:

Points


Datum A: the tangent plane onDatum Target Simulators A1, A2 and A3

SØ10A2

40

SØ10

A3

A

40

500

SØ10SØ10

SØ10SØ10

A1

0

50

A1

A2

A2

A2Datum Targets A1, A2 and A3:

Points

Datum Details for Datum Targets


Datum Details

40

25 18

CB

ADatum Feature B: a Bore


Datum B: the axis ofDatum Feature Simulator B

Datum Details

40

25 18

CB

ADatum Feature B: a Bore


Datum Details

40

25 18

CB

A



Datum C: the mid-plane ofDatum Feature Simulator C

Datum Details

40

25 18

CB

A



Concepts







Details

1. Datum Features

2. Datum Targets


4. Datums


Rules of Datum Feature Simulator Management



1. Form: All simulators shall have perfect form.




2. Orientation: All simulators shall be perfectly oriented by their associated basic angular dimensions.





3. Location: Unless otherwise indicated, all simulators shall be perfectly located by their associated basic linear dimensions.





3. Location: Unless otherwise indicated, all simulators shall be perfectly located by their associated basic linear dimensions.

4. Size: - Simulators referenced RFS shall expand or contract to consume all the space available in or outside their associated Datum Features. - Simulators referenced at MMC or LMC shall be fixed at the Virtual MMC or LMC size of their associated Datum Features.


Rules of Natural Datum Reference Frame Establishment


1. Rule of Datum Feature Precedence: Datum Features shall be used in the order in which they appear in the Feature Control Frame, reading from left to right.




2. Rule of Degrees of Constraint Precedence: Each Datum Feature shall first attempt to constrain pitch & yaw, then only roll, and only then translational degrees of freedom.





3. Rule of Non-Override: No Datum Feature may impact degrees of freedom constrained by higher precedence Datum Features.





3. Rule of Non-Override: No Datum Feature may impact degrees of freedom constrained by higher precedence Datum Features.

4. Can-May-Must Rule: - If a Datum Feature can constrain a degree of freedom, and also may, then it must.



The Six StepDatum Reference FrameEstablishment Process

Now for . . .


Datum Reference FrameEstablishment Process Steps

1. Decode the Feature Control Frame



2. Identify the Datum Features





3. Construct the Datum Feature Simulators






4. Extract the Datums from their Simulators







5. Use the Datums to establish the DRF in the simulators by constraining the rotational and translational degrees of freedom of a starter coordinate system







5. Use the Datums to establish the DRF in the simulators by constraining the rotational and translational degrees of freedom of a starter coordinate system

6. Marry the Datum Features to their simulators to transfer the Datum Reference Frame to the actual part.



The Six Step Datum Reference Frame Establishment Process

Z(1)

Y(1)

C

X(1)25

Y(1)

40

A

B

18


Z(1)

Y(1)

C

X(1)25

Y(1)

40

A

B

18

Step 1.

Decode the Feature Control Frame




What ? One more time ?

No !


Z(1)

Y(1)

C

X(1)25

Y(1)

40

A

B

18


Step 2.

Identify the Datum Features


Z(1)

Y(1)

C

X(1)25

Y(1)

40

A

B

18


Step 2.


Feature A: a planar surface


Z(1)

Y(1)

C

X(1)25

Y(1)

40

A

B

18


Step 2.


Feature A: a planar surfaceFeature B: a hollow cylinder


Z(1)

Y(1)

C

X(1)25

Y(1)

40

A

B

18


Feature A: a planar surfaceFeature B: a hollow cylinderFeature C: a slot

Step 2.




Step 3.

Construct the Datum Feature Simulators

A

25

Z[A,B,C]

B

40

Y[A,B,C] Y[A,B,C]

C

X[A,B,C]

18



Step 3.


A

25

Z[A,B,C]

B

40

Y[A,B,C] Y[A,B,C]

C

X[A,B,C]

18

18

16



Step 3.


A

A

25

Z[A,B,C]

B

40

Y[A,B,C] Y[A,B,C]

C

X[A,B,C]

18

18

16

Simulator A: a planar surface



Step 3.


B

A

25

Z[A,B,C]

B

40

Y[A,B,C] Y[A,B,C]

C

X[A,B,C]

18

18

16

Simulator A: a planar surfaceSimulator B: an expanding solid cylinder



Step 3.


Simulator A: a planar surfaceSimulator B: an expanding solid cylinderSimulator C: a slab fixed in size at

the Virtual Maximum Material Boundary of the slot

C

A

25

Z[A,B,C]

B

40

Y[A,B,C] Y[A,B,C]

C

X[A,B,C]

18

18

16



Step 4.

Extract the Datums from their Simulators

A

25

Z[A,B,C]

B

40

Y[A,B,C] Y[A,B,C]

C

X[A,B,C]

18



Step 4.


Datum A: the tangent plane on Simulator A

A

A

25

Z[A,B,C]

B

40

Y[A,B,C] Y[A,B,C]

C

X[A,B,C]

18



Step 4.


Datum A: the tangent plane on Simulator ADatum B: the axis of Simulator B

B

A

25

Z[A,B,C]

B

40

Y[A,B,C] Y[A,B,C]

C

X[A,B,C]

18



Step 4.


Datum A: the tangent plane on Simulator ADatum B: the axis of Simulator BDatum C: the mid-plane of Simulator C

C

A

25

Z[A,B,C]

B

40

Y[A,B,C] Y[A,B,C]

C

X[A,B,C]

18



Step 5.

Use the Datums to establish the DRF in the Simulators by constraining a

“starter” coordinate system.

A

25

Z[A,B,C]

B

40

Y[A,B,C] Y[A,B,C]

C

X[A,B,C]

18



Step 5.

Use the Datums to establish the DRF in the Simulators by constraining a “starter”

coordinate system.

A

25

Z[A,B,C]

B

40

Y[A,B,C] Y[A,B,C]

C

X[A,B,C]

18

Datum Set



Step 5.


coordinate system.

“Starter” Coordinate System

Y

X

Z

A

25

Z[A,B,C]

B

40

Y[A,B,C] Y[A,B,C]

C

X[A,B,C]

18

Datum Set



Step 5.


coordinate system.

Datum A constrains Rx & Ry (pitch & yaw) plus Tz

Y

X

Z

A

25

Z[A,B,C]

B

40

Y[A,B,C] Y[A,B,C]

C

X[A,B,C]

18

A



Step 5.


coordinate system.

Datum A constrains Rx & Ry (pitch & yaw) plus Tz

Y

X

Z A

Z[A]

X[A]

Y[A]

A

25

Z[A,B,C]

B

40

Y[A,B,C] Y[A,B,C]

C

X[A,B,C]

18



Step 5.


coordinate system.

Datum A constrains Rx & Ry (pitch & yaw) plus TzDatum B constrains Tx and Ty

X

Y

Z

B

A

25

Z[A,B,C]

B

40

Y[A,B,C] Y[A,B,C]

C

X[A,B,C]

18



Step 5.


coordinate system.

Datum A constrains Rx & Ry (pitch & yaw) plus TzDatum B constrains Tx and Ty

X

Y

Z

B

X[A,B]

Y[A,B]

Z[A,B]

A

25

Z[A,B,C]

B

40

Y[A,B,C] Y[A,B,C]

C

X[A,B,C]

18



Step 5.


coordinate system.

Datum A constrains Rx & Ry (pitch & yaw) plus TzDatum B constrains Tx and TyDatum C constrains Rz (roll)

C

X[A,B]

Y[A,B]

Z[A,B]

A

25

Z[A,B,C]

B

40

Y[A,B,C] Y[A,B,C]

C

X[A,B,C]

18



Step 5.


coordinate system.

Y[A,B,C]X[A,B,C]

Z[A,B,C]

C

A

25

Z[A,B,C]

B

40

Y[A,B,C] Y[A,B,C]

C

X[A,B,C]

18

Datum A constrains Rx & Ry (pitch & yaw) plus TzDatum B constrains Tx and TyDatum C constrains Rz (roll)



Step 6.

Marry the Datum Features to their simulators to transfer the DRF to the

actual part.

Y[A,B,C]Y[A,B,C]

40

18

X[A,B,C]

CB

Z[A,B,C]

25

A


The Six Step Datum Reference Frame Establishment ProcessY[A,B,C]Y[A,B,C]

40

18

X[A,B,C]

CB

Z[A,B,C]

25

A

Step 6.


actual part.

X[A,B,C]

Z[A,B,C]

Y[A,B,C]



may rock relative toDatum Feature A.

DRF [A,B,C] . . .

Y[A,B,C]Y[A,B,C]

40

18

X[A,B,C]

CB

Z[A,B,C]

25

A

Step 6.


actual part.

X[A,B,C]

Z[A,B,C]

Y[A,B,C]




DRF [A,B,C] . . .

Y[A,B,C]Y[A,B,C]

40

18

X[A,B,C]

CB

Z[A,B,C]

25

A

Step 6.


actual part.

X[A,B,C]

Z[A,B,C]

Y[A,B,C]

Unless Datum Feature A isrepresented by Datum Targets . . .




DRF [A,B,C] . . .

Y[A,B,C]Y[A,B,C]

40

18

X[A,B,C]

CB

Z[A,B,C]

25

A

Step 6.


actual part.

X[A,B,C]

Z[A,B,C]

Y[A,B,C]

Unless Datum Feature A isrepresented by Datum Targets . . .. . . in which case DRF [A,B,C] will be stable relative to Datum Feature A !



will rock relative toDatum Feature A.

will be stable relative to Datum Feature B.

Y[A,B,C]Y[A,B,C]

40

18

X[A,B,C]

CB

Z[A,B,C]

25

A

Step 6.


actual part.

DRF [A,B,C] . . .

X[A,B,C]

Z[A,B,C]

Y[A,B,C]



will rock relative toDatum Feature A.


will be partially roll mobile relative to Datum Feature C

Y[A,B,C]Y[A,B,C]

40

18

X[A,B,C]

CB

Z[A,B,C]

25

A

Step 6.


actual part.

DRF [A,B,C] . . .

X[A,B,C]

Z[A,B,C]

Y[A,B,C]



40

18

X[A,B,C]

CB

Z[A,B,C]

25

A

Why?

DRF [A,B,C] . . .

will rock relative to Datum Feature A.





40

18

X[A,B,C]

CB

Z[A,B,C]

25

A

Simulator C does not consume all the space inside Datum Feature C !

Because . . .

DRF [A,B,C] . . .






40

18

X[A,B,C]

CB

Z[A,B,C]

25

A

Simulator C does not consume all the space inside Datum Feature C !

Because . . .

DRF [A,B,C] . . .




Y[A,B,C]

25

40

X[A,B,C]



40

18

X[A,B,C]

CB

Z[A,B,C]

25

A

DRF [A,B,C] . . .




Y[A,B,C]

25

40

X[A,B,C]

And . . .



40

18

X[A,B,C]

CB

Z[A,B,C]

25

A

DRF [A,B,C] . . .




Y[A,B,C]

25

40

X[A,B,C]

And . . .although the Considered Feature seems to be out of tolerance . . .



40

18

X[A,B,C]

CB

Z[A,B,C]

25

A

Y[A,B,C]

25

40

X[A,B,C]

DRF [A,B,C] . . .




And . . .although the Considered Feature seems to be out of tolerance . . .



40

18

X[A,B,C]

CB

Z[A,B,C]

25

A

DRF [A,B,C] . . .




And . . .although the Considered Feature seems to be out of tolerance . . . if we roll the DRF, which also rolls the tolerance zone, . . .

Y[A,B,C]

25

40

X[A,B,C]



40

18

X[A,B,C]

CB

Z[A,B,C]

25

A

Y[A,B,C]

25

40

X[A,B,C]

DRF [A,B,C] . . .







40

18

X[A,B,C]

CB

Z[A,B,C]

25

A

DRF [A,B,C] . . .





Y[A,B,C]

25

40

X[A,B,C]



40

18

X[A,B,C]

CB

Z[A,B,C]

25

A


DRF [A,B,C] . . .




Y[A,B,C]

25

40

X[A,B,C]



40

18

X[A,B,C]

CB

Z[A,B,C]

25

A

And . . .although the Considered Feature seems to be out of tolerance . . . if we roll the DRF, which also rolls the tolerance zone, . . . the Considered Feature comes into tolerance !

DRF [A,B,C] . . .




Y[A,B,C]

25

40

X[A,B,C]


This is exactly what a functional gage would do, and therefore exactly what CMM software does – i.e. should do –


This is exactly what a functional gage would do, and therefore exactly what CMM software does -

at least on sunny days !


And in really sophisticated systems, the whole process is automated !

This is exactly what a functional gage would do, and therefore exactly what CMM software does -

at least on sunny days !


Concluding Remarks


Concluding Remarks

We have come here to demonstrate that GD&T can and must only be


Concluding Remarks


“encoded” and “decoded”


and that many GD&T processes can and should be

Concluding Remarks






and that many GD&T processes can and should be

Automated !

Concluding Remarks


SmartGD&T Solutions:

And so it’s time for


What isSmartGD&T ?

SmartGD&T is a rule-based, process driven approach to either the ASME Y14.5M 1994 or ISO 1101 standard, which makes it possible to “encode” and “decode”, rather than “interpret” GD&T, and get it right the first time.


SmartGD&T Solutions:

1. Systematize the language with precisely defined

ConceptsToolsRulesProcesses

2. Automate GD&T related design, manufacturing and inspection processes

3. Provide on-demand, web based support.

4. Build internal, live support teams.


Founded in 1975, Multi Metrics currently provides the following

Services

Products



Services

• SmartGD&T Pseudo-Code

Products

Detailed Guidelines for automating GD&T processes in CAD, CAM and CAI software



Services

• SmartGD&T Pseudo-Code• e-GAD – on-line electronic GD&T Aided Design• Training Manuals & Presentation Materials• Training Models• Reference Books

Products



• SmartGD&T Technology Licensing

Services


Products

Patents and Support for automating GD&T processes in CAD, CAM and CAI software



• SmartGD&T Technology Licensing

• Corporate GD&T Implementation Planning

• On-Site GD&T End–user and Trainer Training

• On-Site GD&T Encoding & Decoding Services

Services


Products


Solution Details

SmartGD&T TM


clarify and systematize the language!

SmartGD&T Solution #1


• Crystalline Definitions !

• Explicit, easily found Rules !

• Smooth Processes

is all about

SmartGD&T TM

Technology

clarify and systematize the language!




Provide web based electronic support!


e-GADelectronic GD&T Aided Design

TM




e-GADelectronic GD&T Aided Design

TM

1. The “SmartGD&T Best Practices Guide”

2. The “SmartGD&T On-Line Tutor”



Consists of:


The SmartGD&T

Best Practices Guide


A searchable,Encyclopedia of GD&T


SmartGD&T Best Practices Guide

TheHome Page

For clarity, we break GD&T down into the four groups:

1. Concepts

Users click on any item in the top or bottom bars to access the desired content or function.

2. Tools

3. Rules

4. Processes

Click on Search to scan any or all groups


The SmartGD&T

On-Line-Tutor


A Collection of Voiced Over,Animated Training Segments


This is an example of the just-in-time GD&T tutorials which make up the On-Line Tutor.

This segment describes the sixth and final step in the Datum Reference Frame Establishment Process.

SmartGD&T On-Line Tutor

TheOn-Line Tutor


This is an example of the pop-up Topic Menu for the On-Line Tutor.

The Topic Menu provides access to each segment of the tutorial and also indicates their duration.

TheOn-Line Tutor

SmartGD&T On-Line Tutor


build internal support teams!



Multi Metrics. Inc.provides on-site & remote

ASME Y14.5M 1994 based

Implementation & Training

build internal support teams!



Automate GD&T processes!



Automate GD&T processes!


Multi Metrics licenses

to help software developers automate

1. GD&T encoding in the CAD world and

2. GD&T decoding in the CAM and CAI worlds

SmartGD&T Technology


InnovMetric Software Inc. the masters of dense point cloud metrology.

• IMI has built a comprehensive SmartGD&T Technology based GD&T decoding and processing engine in PolyWorks, their highly esteemed dense point cloud metrology software system,

• has completely automated geometry processing algorithm selection in keeping with SmartGD&T Technology based fundamental rules,

• has completely automated the Datum Reference Frame establishment process, based on the applicable SmartGD&T Technology patent, and

• has produced a GD&T processing system which is as ergonomic as it is powerful.

Multi Metrics’ first SmartGD&T Technology partner is


How can we help you ?


Please visitwww.multimetrics.com

and give us a call at650-328-0200


Thank you !&

Special Thanks to

Spatial !

Bill Tandler

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GD&T-MULTI METRICS