FOS_ASME - Copy.ppt

ASME Y14.5 presentation by Alex Krulikowski May 2005

ASME Y14.5Proposal

on Feature of Size


1. How to ensure minimum size is met on a feature of size where portions (or in some cases all) of the features are not opposed.

2. Clarify the definition of “size” in Y14.5.

3. Understand the definition of “size” from Y14.5.1

4. Using the size definition from Y14.5.1 to clarify what size means in Y14.5

5. Proposal to change Y14.5 to clarify: actual local size, opposed, size, and feature of size

Topics


Definition of “feature of size” from Y14.5

1.3.17 Feature of Size. One cylindrical or spherical surface, or set of two opposed elements or opposed parallel surfaces, associated with a size dimension.


Dimensioning Concepts Applied to a Feature or a

Feature of SizeDimensioning Concept Applies to a Feature of Size Applies to a Feature

Flatness

Cylindricity

Datum Targets

Circularity

Profile of a Line

Tangent Plane

Position

Concentricity

Profile of a Surface

Bonus

Datum Shift

Viirtual Condition

MMC, LMC and RFS

Symmetry

Yes No

YesNo

Rule #1


Definition of “Opposite” from the Oxford English Dictionary


Example of Fully Opposed Surfaces in Facing and Opposite

Directions

Facing _________from each other

A B C D

E F

Tab Tab

Slot

SurfacesSurfacesConsidered Facing

A & B

B & C

B & D

E & F

Away

Towards

Same Direction

Towards

Opposed

Opposed

Same

Opposed

C & D Away Opposed


Examples of Fully Opposed Line Elements Facing and Opposite

Directions

Facing _________from each otherSurfaces

SurfacesConsidered Facing

A & B

B & C

B & D

E & F

Towards

Away

Same Direction

Towards

Opposed

Opposed

Same

Opposed

C & D Towards Opposed

A B C D

HE F G

G & H Towards Opposed


Examples of Partially Opposed Features

4.

Surfaces A and B containgaps and interruptions

A

B

3.

Surfaces A and B are offset

A

B

1.

Surfaces A and B aredifferent lengths

A

B

Surfaces A and B aredifferent shapes

2.

BA


Examples of Partially Opposed Line Elements

A

Distance A containsoffset line elements

2.A

Distance A contains lineelements of different lengths

1.


Examples of Cylindrical Shapes with Truncated Ends


Examples of Interrupted Features of Size

2X10.610.0

8.2

7.8INTERRUPTED

2.62.0

0.2 M

INTERRUPTED

23.222.8

INTERRUPTED

0 M

0.2


Examples of Partially Opposed from Y14.5


Examples of Partially Opposed

• There are at least 18 examples of partially opposed features of size in Y14.5.

• There are numerous cases of partially opposed features of size in industry.

• Partially opposed features of size cause problems when determining the LMC size in the non-opposed areas.


Definition of “feature of size” from Y14.5

1.3.17 Feature of Size. One cylindrical or spherical surface, or set of two opposed elements or opposed parallel surfaces, associated with a size dimension.


5-1

Definition of “Size” from Y14.5

Assumes Rule #1 is in effect

In Y14.5 the definition for size is limited.


5-1


Problems with “Actual Local Size”

• The direction of measurement is not described, resulting in many answers possible for the value.

Actual local size

•Only works with “opposed points”

• It describes a “two-point” measurement


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However, Y14.5 does not define how size is interpreted when Rule #1 is overridden


5-1

Y14.5 Invokes Y14.5.1

Y14.5 invokes Y14.5.1 which defines how size is interpreted both with and without Rule #1.


Definition of “Size” from Y14.5.1



LMC

MMC

SPINE

ASME Y14.5 presentation by Alex Krulikowski May 2005A


• A 0-dimensional spine is a point, and applies to spherical features.

• A 1-dimensional spine is a simple (non-intersecting curve in space, and applies to cylindrical features.

• A 2-dimensional spine is a simple (non-intersecting surface, and applies to parallel plane features.

Spine Types


When perfect form at MMC is required



Size and Partially Opposed Features

• Actual local size requires fully opposed surfaces.

• Actual local size is defined as a two-point measurement. There is no direction for the measurement defined. Should actual local size be defined as a tolerance zone?

• Actual local size is only explained as a method for checking a minimum distance.

• How is a max size checked when Rule #1 is overridden as in figure 6-3?

In Y14.5 In Y14.5.1

• Does not require fully opposed features.

• Does not use the term actual local size. Uses two half space boundaries to define the size tolerance zone.

• Explanation for use with max or min size definition

• Works with or without Rule #1.


Size according to Y14.5

The 64.6 – 65.0 diameter is considered a feature of size. Using the Y14.5 definition of size, it is impossible to measure the actual local size of the diameter.


Now lets look at how the

same size dimension

would be interpreted using

Y14.5.1


Size according to Y14.5.1

The 64.6 – 65.0 diameter is considered a feature of size. Using the Y14.5.1 definition of size, the size tolerance zone of the 64.6-65.0 diameter is defined by two half space boundaries.

The boundaries are established by two balls: The MMC limit is defined by a ball equal to the MMC size. The LMC limit is defined by a ball equal to the LMC limit.

The balls are moved along appropriate spines to define the tolerance zone.


Examples of Size Using Y14.5.1

10.610.0

Drawing Meaning

10.6 MMC boundary

MMC ball LMC ball

No difficulty measuring the portion of the feature that does not have opposed points


Drawing Meaning

10.610.0

10.6 MMC boundary

MMC ball LMC ball

Examples of Size Using Y14.5.1

No difficulty measuring the portion of the feature that does not have opposed points


5-1

1.3.24 Size, Actual. The general term for the size of a feature. See ASME Y14.5.1 paragraphs 2.3.1 and 2.3.2 for an explanation of variations in size.

Text in Y14.5M-1994 Proposed Text


Delete paragraph 1.3.25 and replace all instances of Actual local size with Actual Size. (11 places in text and 4 places in figures)

Recommendations


5-1

2.7 LIMITS OF SIZE

Unless otherwise specified (by specification of a straightness control applied to a size dimension, or a note as described in paragraph 2.7.2), the limits of size prescribe the extent within which variations of geometric form, as well as size are allowed. This control applies solely to individual features of size as defined in para. 1.3.17.


Recommendations


Recommendations

• Show the MMC and LMC balls located along spines in several examples

• Add a paragraph and examples to explain “opposed”

• Add a paragraph and examples of features of size with partially opposed features.


The end

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