199679022-ASME-Y14-5-2009-GDT-Tandler-pdf

Copyright © 2004 - 2009 by Multi Metrics, Inc. Menlo Park, CA All Rights Reserved

by

Bill Tandler

A SmartGD&T™ Workshop

SmartGD&TIntroductory Remarks

TM

for the

Carl Zeiss CMM User Group Meeting 2009


Workshop Overview

1. What is GD&T? – A Reminder2. Fundamental GD&T Concepts3. Feature Control Frames: Structure & Decoding4. The Datum Reference Frame Establishment

Process in Concept and using CMM Software

SmartGD&T™


What is GD&T ?


Grim, Depressing & Troublesome

Many people think “GD&T” stands for

or

Greatest Design Tool ever !


Perfectly!

and it’s the only tool we have for

managing imperfect geometry

But of course, GD&T stands for

Geometric Dimensioning & Tolerancing


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

Definition

but in fact . . .The primary purpose of GD&T, is to ensure that what we communicate is worth communicating . . . . namely represents functional, assemblable parts.


In fact ….

without GD&Tall coordinate metrology must remain

Pure Inventionon the part of the inspector


How about the GD&T tool kit?It consists of:

Geometry Control ToolsFeature Control FramesBasic Dimensions, andDatum Feature Labels


1. Tolerance ZonesBounded regions of space within which feature components are required to lie.

2. Tolerance ValuesThe sizes of tolerance zones.

3. DatumsReference points, lines and planes.

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

5. Basic DimensionsTools for orienting and locating tolerance zones.

6. Geometry Control ToolsA symbolic language for imposing the perfect imaginary world on the imperfect real world.

TZ Wall ThicknessTZ Diameter

TZ Thickness

The Perfect Imaginary World of GD&T

Tube-like

Cylindrical

Slab-like


The imperfect actual part!

The actual part embedded in its associated tolerance zones

The coordinate system and tolerance zone “forest” defined by the GD&T Code

The encoded CAD Model GD&T at Work


1. Datum Features2. Datum Feature Simulators3. Datums4. Datum Reference Frames5. Basic Dimensions6. Material Condition Modifiers7. Actual Values

Fundamental Concepts


Physical Datum FeaturesImportant Concepts

Definition:

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


Substitute Datum FeaturesImportant Concepts

The CMM Connection:

Coordinate Metrology systems use geometry processing algorithms to extract form-perfect substitute Datum Features from actual Datum Features.


Substitute Datum FeaturesImportant Concepts

SubstituteDatum Feature A

Alternatives:

1. Least squares plane2. Mid-plane of the minimum slab-like zone3. In-space, surface of the minimum slab-like zone4. In-space, force constrained tangent plane


Important Concepts

1. Unconstrained, maximum inscribed cylinder2. Least squares cylinder3. In-space surface of the minimum tube-like zone

Substitute Datum Features

SubstituteDatum Feature B

Alternatives:


Important Concepts

1. Mid-plane of two least squares planes2. Mid-plane of the in-space boundary planes of

two minimum slab-like zones

Substitute Datum Features

SubstituteDatum Feature C

Alternatives:



More Important Concepts


Datum Feature SimulatorsDefinition:

The conceptually perfect, or physically almost perfect, geometric counterparts of Datum Features, which are beholden to the Rules of Datum Feature Simulator Management, and:

Important Concepts

1. from which we extract Datums

2. in which we first establish Datum Reference Frames, and

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


Physical Datum Feature SimulatorsImportant Concepts

PlanarDatum Feature Simulator

AExpanding Cylindrical

Datum Feature Simulator B

Fixed “Tombstone”Datum Feature Simulator

C


Important Concepts

The CMM Connection:

Coordinate Metrology systems use geometry processing algorithms to extract form, and potentially size, orientation and location constrained, perfect, inverse substitute features from actual datum features and CAD models.

Mathematical Datum Feature Simulators


Computer generated, size, orientation and location constrained, slab representing Datum Feature Simulator C

Important Concepts

Computer generated unconstrained, tangent planerepresenting Datum Feature Simulator A

Computer generated, orientation constrained, maximum inscribed, cylinder representing Datum Feature Simulator B

Mathematical Datum Feature Simulators





Important Concepts

DatumsDefinition:

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

Datums serve to constrain the degrees of freedom of starter coordinate systems and turn them into

Datum Reference Frames.


Datum Feature Simulators & Datums


Datum C is the mid-plane ofDatum Feature Simulator C

Important Concepts

Datum A is the tangent plane onDatum Feature Simulator A

Datum B is the axis ofDatum Feature Simulator B

DatumsExtracted from Datum Feature Simulators


Important Concepts

DatumsExtracted from Datum Features

The CMM Connection:

Coordinate Metrology systems often bypass the simulator step and use geometry processing algorithms to extract Datums directly from Datum Features. This is perfectly possible, but BEWARE !


Important Concepts


In fact, Datum B is the axis of the orientation constrained, maximum inscribed cylinder inside Datum Feature B

Case 1

What is Datum B ???Surely Datum B is the axis of the maximum inscribed cylinder inside Datum Feature B !

Right !

Wrong !


Important Concepts


In fact, Datum C is the mid-plane of the orientation & location constrained, virtual maximum material condition slab inside Datum Feature C.

Right !

What is Datum C ???

Wrong !

Surely Datum C is mid-plane of the maximum inscribed slab inside Datum Feature C


Important Concepts

Question:

What do the letters in a Feature Control Frame represent:1. Datums ?2. Datum Features ?3. Datum Feature Simulators ?


Important Concepts

Question Answer

Datum Features …. of course!

Points, lines and planes cannot be “simulated” regardless of their size, or simulated at their virtual Maximum Material Boundaries.





Important Concepts

Datum Reference Frames

Definition:

Datum Reference Frames are Cartesian Coordinate Systems

established using Datums.


Important Concepts

Datum Reference FramesIn the CAD Model


Important Concepts

Datum Reference FramesIn the Simulator Set


Important Concepts

Datum Reference FramesIn the Actual Part





Important Concepts

Basic Dimensions

Definition:

Basic dimensions are framed angular and linear dimensions, which serve to orient and locate tolerance zones, …..

…... but only those tolerance zones which can be oriented and located.


Important Concepts

They locate the Position tolerance zone for the lower, right hand bore.

Basic Dimensions Case 1

What purpose do these basic dimensions serve?


Important Concepts


It locates the Position tolerance zone for the slot (Datum Feature C).

What purpose does this basic dimension serve?


Important Concepts

This basic dimension serves no purpose, because Parallelism tolerance zones cannot be located.


What purpose does this basic dimension serve?





Important Concepts

Material Condition Modifiers

Definition:


can be associated with:

Datum Features

Tolerance Values

M L S

and


Important Concepts


M permits the tolerance zone to expand by as much as 1 mm as the bore departs from MMC toward LMC.

When associated withtolerance values they impact the size of a tolerance zone.


Important Concepts


S stabilizes the tolerance zone relative to Datum Feature B, regardless of its size.

When associated withDatum Features they impact the stability or mobility of a tolerance zone.


Important Concepts


M mobilizes the tolerance zone relative to Datum Feature C, as C departs from its Virtual MMC size.

When associated withDatum Features they impact the stability or mobility of a tolerance zone.





Important Concepts

Actual Values

The Actual Value of a geometric characteristic is the size of the smallest associated tolerance zone that just accommodates the controlled component of the considered feature.

Definition:


Important Concepts

Actual Values

What are the Actual Values of the Size of a bore?

Case 1

1. Actual Mating Size = the Diameter of the Maximum Inscribed Cylinder

2. Actual Local Size = the Diameter of the largest Minimum Circumscribed Circle


Important Concepts

Actual Values Case 2

Actual Position = the Diameter of the location constrained, minimum circumscribed cylinder which just contains the bounded axis.

What is the Actual Value of the Position of a bore?


Important Concepts



Important Concepts


Actual Straightness = the Diameter of the smallest unconstrained cylinder which just contains all the points in the Median Line.

What is the Actual Value of the Straightness of a bore?


What’s the

TheMeasured Value

of a Geometric Characteristic is the measuring uncertainty limited

Actual Value

Measured Value ?


Feature Control Frame

Anatomy


Feature Control Frame Anatomy

Specifies the Geometry Control Tool

Tolerance Zone Size Modifier

Specifies the Tolerance Zone

Tolerance Zone Mobility Modifiers

Specifies the Datum Reference Frame Establishment Process

PrimaryDatum Feature

SecondaryDatum Feature

TertiaryDatum Feature

Tolerance Zone Shape

Tolerance Zone Size


Material Condition Modifier Effects

Tolerance Zone SizeModifiers

M ore tolerance

L ots of tolerance

S tuck at 0.5 mm

M

L

S

Impact on Tolerance Zone Encoded Function

Feature Clearance

Feature Overlap

Feature Centering



Tolerance Zone SizeModifiers

Easy to implement, and generally well managed !

Easy to implement, but is it truly understood ?

Easy to implement – nothing to do !

M

L

S

Impact on Coordinate Metrology


Tolerance Zone MobilityModifiers

M Fixes Simulator at its Virtual MM Boundary

L Fixes Simulator at its Virtual LM Boundary

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

M

L

S


Impact on Simulators



M obilizes the tolerance zone

L oosens the tolerance zone

S tabilizes the tolerance zone

M

L

S


Impact on DRF & Tolerance Zone Encoded Function

Mating Part play, guaranteeing clearance

Mating Part play, guaranteeing overlap

Mutual Centering

{{




Presents challenges !

Presents challenges !

Should present no problems !

M

L

S

Impact on Coordinate Metrology


Decoding GD&Tas opposed to

Interpreting GD&T

Now we’ll illustrate


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

Reading the Feature Control Frame.


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 Considered Feature departs from MMC toward LMC -

Decoding the Feature Control Frame.


- 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 mobly, at its Virtual Maximum Material Condition size.

Decoding the Feature Control Frame.


Namely this Datum Reference Frame !


1. Datum Features2. Datum Feature Simulators3. Datums4. Degrees of Freedom

Concepts

1. Datum Feature Labels2. Tolerance Zone Mobility Modifiers3. Feature Control Frames

Tools

Rules 1. Rules of Datum Feature Simulator Management2. Rules of Natural Datum Reference Frame Establishment

Foundations for establishing a Datum Reference Frame


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 dimensions.

3. Location: Unless otherwise indicated, all simulators shall be perfectly located by their associated basic 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 MMC or LMC shall be fixed at the Virtual MMC or LMC size of their associated Datum Features.


1. Datum Feature Precedence: Datum Features shall be used in the order in which they appear in the Feature Control Frame.

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

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

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

Rules of Natural Datum Reference Frame Establishment


Step 1.Decode the Feature

Control Frame

Step 2.Identify the Datum

Features

Step 3.Construct the Datum Feature Simulators

Step 4.Extract the Datums from the Simulators

Step 5.Use the Datums to constrain a

starter coordinate system in the Simulators

Step 6.Transfer the DRF to the

part by mating the Datum Features with their

simulators

A: planar surface

Expanding Cylindrical Simulator B

Virtual MMCTombstone Simulator C

Planar Simulator A

The Six Step Datum Reference Frame Establishment Process

B: hollow cylinderC: slot


Concluding Remarks

1. GD&T is clearly essential for Metrology2. GD&T is clearly complex3. GD&T is sporadically used and therefore

easily lost.

1. GD&T Advisor Teams2. GD&T Encoding Automation3. GD&T Decoding Automation

Keys for Success


by

Bill Tandler

A SmartGD&T Overview

Updated 2009-10-29

The NewASME Y14.5 2009 Standard

TM

for the

Carl Zeiss CMM User Group Meeting 2009


Tutorial Overview

1. “What is GD&T?” - A Reminder2. New Concepts3. New Tools Impacting Datums4. New Tools Impacting Tolerance Zones5. Disappointments

SmartGD&T™


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

“What is GD&T?” A Reminder

but in fact . . .The primary purpose of GD&T, is to ensure that what we communicate is worth communicating . . . . namely represents functional, assemblable parts.


1. Design

2. Manufacturing

3. Inspection

4. Assembly

is a risk management tool for . . .

GD&T


GD&T is a symbolic language for1. researching2. refining and3. encoding

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

1. assess the fault tolerance of our designs2. guarantee assemblability and operation prior

to drawing release3. reduce manufacturing costs by setting

precise, achievable objectives4. turn inspection into a truly scientific process


1. Concepts2. Tools3. Rules4. Processes5. Best Practices

GD&T consists of

This review of the 2009 Standard addresses these two components


1. New Names for Material Condition Modifiers2. Loss of the RFS Modifier S

Y14.5 2009 Changes and their Impact

New Concepts(a partial set)



New Tools impacting Datums1. A more complete definition of Datums2. Applicability of the modifiers S M L to Planar Datum Features3. The new Datum (Feature Simulator) Translation Modifier: ►4. New Degrees of Constraint Modifiers: [u,v,w,x,y,z]5. Expanded Composite Feature Control Frames – Up to four tiers.6. New Datum Reference Frame Axis Labels: X[A,B,C], Y[…] etc.



1. Unequally Disposed Profile Modifier: U2. Non-Uniform Modifier: [NON-UNIFORM]3. ALL OVER Modifier: 4. Continuous Feature Modifier: CF5. Independency Modifier: I

New Tools impacting Tolerance Zones(a partial set)



Disappointments1. Still no clearly defined, accessible, sets of Rules.2. The Concentricity and Symmetry tools unchanged.3. The Radius and Controlled Radius Tools still define

non-functional crescent shaped tolerance zones.4. Still no tool for controlling the orientation and location

of curved “spines”.5. Still no page number references in the index.






If all these modifiers are called“Material Condition” Modifiers

how can we differentiate between their effects?

New Names for Material Condition Modifiers



The Great Divide

MobilityThese modifiers impact Tolerance Zone Size

“Tolerance Value”Modifiers “Material Boundary”

Modifiers

These modifiers impact Tolerance Zone

New 2009 Name

New 2009 Name



Here are our favorites

It’s great to finally highlight the differences,

but the names could be better.



The Great Divide

MobilityThese modifiers impact Tolerance Zone Size

“Tolerance Zone Size”Modifiers

“Tolerance Zone Mobility”Modifiers

These modifiers impact Tolerance Zone

the SmartGD&T recommended names






Loss of the RFS Modifier S

1982required

1994permitted

2009forbidden

Not good !



Why not good ?

2009forbidden

1. Explicit modifiers inform us directly, and save time when “decoding” Feature Control Frames. Time is money !

2. An explicit S confirms that the designer chose S intentionally after considering M and L , rather than having overlooked the need to make a choice. Awareness and certainty save money !



Retaining an explicit S is therefore highly recommended !

You can do so with a corporate document specifying it as a corporate modification to the Standard, or with a note, both very common practices in industry.

2009





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.

Datums serve to constrain the degrees of freedom of starter coordinate systems and turn them into

A more complete definition of “Datums”

Datum Reference Frames.


Datum Feature Simulators & Datums


1. A more complete definition of Datums2. Applicability of the modifiers S M L to Planar Datum Features3. The new Datum (Feature Simulator) Translation Modifier: ►4. New Degrees of Constraint Modifiers: [u,v,w,x,y,z]5. Expanded Composite Feature Control Frames – Up to four tiers.6. New Datum Reference Frame Axis Labels: X[A,B,C], Y[…] etc.


New Tools impacting Datums


C is a planar surface.

Applicability of the modifiers S M L to Planar Datum Features

Prior to 2009, the Tolerance Zone Mobility modifiers S M and L could not be applied to planar surfaces !


If C is a location constrained planar

Datum Feature,TZM

modifiers are now allowed


The 2009 Y14.5 Standard now makes Tolerance Zone Mobility modifiers applicable to planar surfaces, but only those which are “location constrained”, in other words, to those for which Maximum Material and Least Material boundaries can be defined.


This change eliminates one half of the so-called“Tertiary Datum Problem”


If there is more than one way for a Datum Feature to constrain degrees of rotational freedom, there must be codeto distinguish between the alternatives.


Here’s the part drawing !


Examples



And here are theDatum Feature Simulators



Each alternative encodes a different function and requires different simulator behavior

The question is:How should Simulator C behave?


Simulator “C”


First . . . the details for M :

Simulator fixedIn-

Space

M fixes Simulator C at the Virtual Maximum Material BoundaryPermitting residual in-space roll M obility !


S requires Simulator C to slide up to and consume all the space outside Datum Feature C, imposing

Next . . . the details for S :

Simulator Sliding

Simulator “C”


in-space roll S tability !


L fixes Simulator C at the Virtual Least Material BoundaryPermitting residual

And here . . . the details for L :

DFS “C”


in-material roll L ability !

Simulator fixedIn-

Material



Simulator C is fixed in-space !

If the planar surface is referenced at M

in-space roll M obility !

Review



Simulator C is sliding !

If the planar surface is referenced at S

in-space roll S tability !



Simulator C is fixed in-material !

If the planar surface is referenced at L

in-material roll L ability !


How useful is this addition?


Veryencodes potential “mobility” (or play) between mating planar features during assembly, and permits taking advantage of it.

encodes “stability” between mating planar features during assembly, and forbids taking advantage of potential “play”.

encodes potential “looseness” between a planar Datum Feature in its cast versus its machined condition, and permits taking advantage of it during material removal.

M

S

L





Datum (Feature Simulator) Translation Modifier: ►

Applicability

The translation modifier applies only to “Datum Features of Size”.

Whereas S M and L require Datum Feature Simulators to expand, contract or be fixed in size, addition of the translation modifier frees Datum Feature Simulators of size to also translate during the DRF establishment process.



If there is more than one way for a Datum Feature to constrain degrees of rotational freedom, there must be codeto distinguish between the alternatives.

The translation modifier eliminates theother half of the so-called

“Tertiary Datum Problem”



Here’s one possible application of the Translation modifier.

Here’s a part drawing !

Examples



Here are theDatum Feature Simulators



In this case Datum Feature C serves as a clocking Datum Feature !

And here are the details for M without

M requires Datum Feature Simulator C to be fixed in size and location, leading to potential roll mobility based on Datum Feature C’s location.



In this case Datum Feature C also serves as a clocking Datum Feature !

Next . . . the details for S without

S requires Datum Feature Simulator C to be fixed in location, but expand, leading to roll stability based on Datum Feature C’s location.



In this case Datum Feature C serves as an aligning Datum Feature !

Finally . . . the details for S with

S requires Datum Feature Simulator C to expand and requires it to slide, leading to roll stability based on Datum Feature C’s orientation.



The simulator is fixed in location and fixed in size.

If M is used without

Clocking with residual roll M obility



The simulator is fixed in location but is required to

expand.

If S is used without

Clocking with roll S tability



The simulator is required to

expand and slide.

If S is used with

Aligning with roll S tability


M +

encodes the “stability” and “aligning” function of roll constraining datum features of size during assembly.

encodes the potential “lability” (looseness) and also the “clocking” function of roll constraining, cast, forged or molded datum features during secondary machining operations.

encodes the potential “mobility” and also the “clocking” function of roll constraining datum features of size during assembly.

S +

L +


Impact


Quite


How useful is the Translation modifier ?

Because, even though it will be rarely required, it enables explicit feature

function encoding.





Degrees of Constraint Modifiers: [u,v,w,x,y,z]

What’s the purpose of Datum Features ?

To constrainrotational and translational

degrees of freedomduring assembly processes!

Let’s start with a question:



There are 6 degrees ofrotational and translational freedom:

3 Rotational:

and a set of six new tools for constraining them:

[u,v,w,x,y,z]

1. Tx2. Ty3. Tz

uvw

xyz

1. Pitch2. Yaw3. Roll

3 Translational:

The Degrees of Constraint Modifiers



Degrees of Constraint modifiers are placed inside brackets to the right of the Material Boundary modifier associated with a Datum Feature label, and serve to specify the degrees of freedom that a particular Datum Feature is required and permitted to constrain !

Degrees of Constraint modifiers make theCan, May, Must rule explicit !



Example:

All we have to do is list them in the Feature Control Frame

five Datum Features.

Just for fun, let’s try to control the left hand bore relative to a Datum Reference Frame established using . . .



But this doesn’t work, because A, B and C already constrain all six degrees of freedom !

Example:



Example:

UsingDegrees of Constraint

modifiers !

However, if this is a real, functional objective, which it could be, how can we encode it?



Example:Let’s use -1. A to constrain only pitch

and yaw.2. B to constrain only roll.3. C to constrain only

translation in Z4. D to constrain only

translation in X.5. E to constrain only

translation in Y.



And here it is !The

Datum Reference Framedefined by our fiveDatum Features !



But first, the 2009 change in

Composite Feature Control Frames

Now we need a much morepractical

Degrees of Constraint Modifiers

example.





Composite Feature Control Frames – Up to four tiers

Composite Feature Control Frames ?But, what’s so special about

They provide specialfunction encoding power.

Composite Feature Control Frames can now have up to four tiers !!!



by limiting the Datum Features in the second and all lower tiers to constraining only rotational degrees of freedom !

How?



The functional objectives we want to encode are:1. the coaxiality of the two small bores relative to the long

bore (Datum Feature A) on the right, shall be heldwithin 100 microns.

1. the combined parallelism of the two small bores relative to the long bore shall be held within 50 microns.

1. the mutual coaxiality of the two small bores shall be held within 10 microns.

Focusing on the two small bores on the left and the long bore on the right . . . .

Example



1. Because A in the first tier constrains pitch, yaw and both degrees oftranslational freedom, the first tier imposes global coaxiality relative to A.

Here’s how we can do that using a Composite Feature Control Frame!




Here’s the DRF defined by Datum Feature A



First Tier Tolerance Zone Ø0.10


. . . and here is the location constrained, cylindrical Position tolerance zone of diameter 100 microns.



2. Because A in the second tier constrains only pitch and yaw, the second tier imposes refined mutual coaxiality and refined parallelism relative to A . . .

. . . and defines an orientation constrained, cylindrical Position tolerance zone of diameter 50 microns, which is free to slide up and down.



3. Due to the absence of all external constraints, the third tier merely further refines the mutual coaxiality of the two bores . . .

. . . and defines a totally unconstrained, cylindrical Position tolerance zone of diameter 10 microns, which is free to pitch, yaw and slide up and down.



Third Tier Tolerance Zone Ø0.01

First Tier Tolerance Zone Ø0.10

Second Tier Tolerance Zone Ø0.05Here are all three tolerance zones

stacked together !



We no longer needComposite Feature Control Frames

Degrees of Constraint Modifiers !

We go from a “Composite” to a Compound”Feature Control Frame and use Degrees of Constraint Modifiers !



How useful areDegrees of Constraint Modifiers ?

Very !They eliminate the need for Composite Feature

Control Frames and provide even more function encoding power

than we had before !





Datum Reference Frame Axis Labels: X[A,B,C], Y[…] etc.

As we have already seen,

locating the axes of a Datum Reference Frame isn’t so easy !

Let’s do an exercise.



Datum Feature A constrains pitch, yaw and one degree of translational freedom.

Can you figure out the locations of the X, Y and Z axes of the DRF defined here?

Datum Feature B constrains roll and one more degree of translational freedom.

Datum Feature C constrains thelast degree of translational freedom.



Here they are !Can you figure out the locations of the X, Y and Z axes of the DRF defined here?



But which axis is X, which is Y and which is Z ?


Datum Reference Frame Axis Labels

We now have


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



so everyone knows exactly what’s going on !


1) DRF axis labels accelerate the decoding of Feature Control Frames in the machine shop and in inspection.

2) DRF axis labels standardize coordinate measuring machine data reporting.

3) DRF axis labels are required when using Degrees of Constraint modifiers, because the axes are referenced in the code.

Benefits







The Surface Profile tool specifies symmetrical skin-like tolerance zones by default.

Unequally Disposed Profile Modifier: U

The Tolerance Zone



Can we escape from dependence on visual cues ?

The Tolerance Zone Boundaries

The 1994 Standard specifies unilateral tolerance zones graphically.



How does it work?

The 2009 Standard specifies unilateral tolerance zones symbolically using the unequally disposed modifier U


The value in front of the modifier specifies the total tolerance, and . . .


. . . the value behind the modifier specifies the in-space portion of the tolerance.



Once we latch, it seems to

work !


The 2009 Standard specifies unilateral tolerance zones symbolically using the unequally disposed modifier U



The 1994 Standard also specifies unequal bilateraltolerance zones graphically:

How does 2009 handle this ?



The 1994 Standard also specifies unequal bilateraltolerance zones graphically:

The same way !


The value in front of the modifier specifies the total tolerance, and . . .


. . . the value behind the modifier specifies the in-space portion of the tolerance.




The 2009 Standard also uses the symbol U to specify unequal bilateral tolerance zones



We have eliminated dependence on visual cues !

How useful is theModifier U ?

Very !






Non-Uniform Modifier: [NON-UNIFORM]

How do we specify a Surface Profile Tolerance Zone whose thickness is required to vary ?

. . . Using a the non-uniform modifier plus . . .

. . . graphical indications of the boundaries embedded in the CAD model or added to the drawing.






ALL OVER Modifier:

The 2009 Standard provides a symbol as a replacement for the note ALL OVER.

But the note ALL OVER isstill permitted !






Continuous Feature Modifier: CF

When applied to an interrupted collection of Features of Size, the “Continuous Feature” modifier imposes the Envelope Rule on the entire set as a group.

Other applications of the Continuous Feature modifier are also possible, but are not mentioned in the 2009 Standard.






The Independency Modifier: I

This . . .

Replaces this !

I means: Independent of the Envelope Rule



No ! because the automatically imposed Envelope Rule requires global Cylindricity of 0.02 mm, which is impossible in such a long shaft.

ExampleIs this a functional specification?



No ! Because without the Envelope Rule the shaft could turn into a garden hose !

ExampleDoes this make sense?



Yes ! We now have a thoroughly functional solution !

Example

Does this make sense?

What if we add “incremental” Cylindricity ?



Disappointments1. Still no clearly defined, accessible, sets of Rules.2. The Concentricity and Symmetry tools unchanged.3. The Radius and Controlled Radius Tools still define

non-functional crescent shaped tolerance zones.4. Still no tool for controlling the orientation and

location of curved “spines”.5. Still no page number references in the index.


Multi Metrics, Inc.is the home of

SmartGD&T TM

Concluding Remarks


What isSmartGD&T ?

Concluding Remarks

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.


Founded in 1975, Multi Metrics provides the following

• SmartGD&T Technology Licensing• Corporate GD&T Implementation Planning• On-Site GD&T End–user and Trainer Training• On-Site & Remote GD&T “Encoding” & “Decoding”

Services

Services

• SmartGD&T Pseudo-Code• Training Manuals & Presentation Materials• Training Models• Reference Books

Products


How can we help you ?


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Thank you !Bob Connors

&The Carl Zeiss CMM User

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Bill Tandler

Documents

199679022-ASME-Y14-5-2009-GDT-Tandler-pdf