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The Development of Support for PMI in STEP AP203E2 and AP214

Tony RangerTechnical DirectorTheorem Solutions Ltd.

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Theorem Solutions : Interoperability Experts

Theorem Solutions : Major Partnerships

Siemens PLM Software

UG NX, JT, NX I-DEAS, Parasolid

Dassault Systemes

Catia V5, Enovia, Delmia

Parametric Technologies

ProE Wildfire, ProductView

Theorem involvement with STEP

1993 : STEP development for CADDS 5

PDES Inc. AeroSTEP pilot

Boeing, Rolls Royce, Pratt & Whitney, General Electric

AP203 Class 6 Brep Solids

1993-Present

Members of PDES Inc. and ProSTEP

Participants in CAX-IF

(previously STEPNet & ProSTEP Roundtable)

Member of AP203 Certification Board

Participated in ISO SC4 meetings

Production STEP Processors

CADDS 5

UG NX

Parasolid

CATIA V4

SC03

STEP and 3D PMI

Representation Data

The semantic information in an intelligent form

machine readable

Presentation Data

The display definition of the information

human readable

Example of Simple Dimension

What you see here is the presentation

Representation and Presentation Data

Representation DataDiameter Dimension

Value of dimension 1.0

Plus Minus Tolerance for diameter 0.003

Presentation Data3 Text Strings : “<0>” “1.000” “<$t>.003” (UG NX)

“\S\X” “1.000” “\S\1.003” (STEP)

Text font, width, height, character and line spacing

WCS Definition

Position in WCS

Leader line, dimension line, arrowhead symbol

definition and placement

Sub Classifications of Presentation Data

There are many ways of defining the presentation data.

The CAX-IF has defined 3 ways for which recommended practices will be produced.

Polyline Presentation

Minimal Semantic Presentation

Full Semantic Presentation

Polyline Presentation Data

Definition of presentation data

(my understanding)

All display graphics defined as polyline or circular arc 3D geometry.

Minimal Semantic Presentation Data

Definition of presentation data

(my understanding)

The minimum amount of data which, together with the representation data, allows the target system to create the PMI display information in its natural (native) form.

Full Semantic Presentation Data

Definition of presentation data

(my understanding)

A full set of semantic presentation data (text, curves, symbols) such that the PMI display information can be created in the target system.

Some Advantages / DisadvantagesPolyline Presentation

Polyline is very simple WYSIWYG

No intelligence

Difficult to validate content

Some Advantages / DisadvantagesMinimal Semantic Presentation

Minimal Semantics is not WYSIWYG

Full intelligence – translated PMI object behaves as native object because it is a native object

Some Advantages / DisadvantagesFull Semantic Presentation

Full Semantics is almost WYSIWYG

Limited intelligence – because it is not created as native semantic PMI object. In UG NX may create “Assorted Parts Dimension”

Can be linked with intelligent objects – dependent on system API functionality.

Text Font

IGES translation for drawings – the light box test.

Different systems have different font tables.

Even if fonts have the same name they may not satisfy the window text.

STEP provides for the AP to define supported fonts.

STEP Document Structure

Resource Parts

e.g. Part 42

Product data representation and exchange: Integrated generic resource: Geometric and topological representation

AICs

e.g. Part 520

Application interpreted construct: Associative draughting elements

APs

e.g. Part 202

Application protocol: Associative draughting

STEP Entity Definition Context

AICs are based on resource parts and extend them for a specific application discipline. Additional subtypes of entities may be created to specialise the meaning of that entity.

Application Protocols are built from resource parts and AICs. Any recommended practices produced are specifically relevant to APs which support all of the entity definitions, the rules, the valid defined text strings and select types.

Text Font

IGES translation for drawings – the window test.

Different systems have different font tables.

Even if fonts have the same name they may not satisfy the window text.

STEP provides for the AP to define supported fonts.

AP 214 : ‘ISO 3098-1 font A’ ‘ISO 3098-1 font B’

AP 203 E2 : ‘ISO 3098’

In addition, there is a capability for non-formal support of fonts.

These need to be semi-formalised via recommended practice.

ISO 3098 Technical Product Documentation - Lettering

ISO 3098-1 Font A

Recommended Practice for Text Font

text_literal ->font : font_select;

font_select = SELECT (pre_defined_text_font, externally_defined_text_font);

pre_defined_text_font : SUBTYPE OF (pre_defined_item);

pre_defined_item -> name : label;

Current recommended practice is to always use a subtype of pre_defined_text_font.

draughting_ pre_defined_text_font has rules limiting the content of the name attribute.

New Recommended Practices ?

text_literal ->font : either pre_defined_text_font or externally_defined_text_font

pre_defined_text_font -> name : label;

New Recommended Practice could provide for use of pre_defined_text_font with specifically agreed names. E.g. Arial

New Recommended Practices ?

text_literal ->font : either pre_defined_text_font or externally_defined_text_font

pre_defined_text_font -> name : label;

New Recommended Practice could provide for use of pre_defined_text_font with specifically agreed names. E.g. Arial

externally_defined_text_font is a subtype of externally_defined_item

source : identifier – for example “UG NX”

Item_id : identifier – for example “blockfont”

Key property of a text string is the space it takes in the display.

Recommended Practice for Handling Text

Key property of a text string is the space it takes in the display.

Recommended Practice for Handling Text

This is a PMI note providing some information This is an appended note.

Key property of a text string is the space it takes in the display.

If the space that the text uses is incorrect, it can cause problems.

Recommended Practice for Handling Text

This is a PMI note providing some information This is an appended note.

This is a PMI note providing some informationThis is an appended note.

Key property of a text string is the space it takes in the display.

If the space that the text uses is incorrect, it can cause problems.

Recommended Practice for Handling Text

This is a PMI note providing some information This is an appended note.

This is a PMI note providing some informationThis is an appended note.

Recommended Practice : use text_literal_with_extent to define text. During post-processing, select text size properties to ensure the text uses the same extents box.

Combinations of forms of data within STEP

Representation Data

Useful only for systems which do not require presentation content (e.g. UG NX)

Representation Data and Presentation Data

Minimal or Full Semantic Presentation Data

Presentation Data

Full Semantic or Polyline Presentation Data

Associativity

CAD systems can retain full associativity of PMI with the underlying geometry.

STEP supports associativity of PMI with geometry but it is very cumbersome and yet not as detailed as the native CAD data.

Linear Dimension

This is a vertical dimension between the end points of 2 parallel lines.

Linear Dimension

This is a vertical dimension between the end points of 2 parallel lines.

Object Associativity

Within UG NX the associativity information is quite detailed – the UF_DRF_object_assoc_data structure defines which end of the line is referenced or, for arc edges, can point to the centre of the arc or a tangency point on the arc.

Within STEP, the information is much more cumbersome and is not so detailed.

STEP Object Associativity

Linear Dimension to Centre of Arc

For this, UG NX has associativity flag to identify referred point as the centre of the arc.

STEP Object Associativity

Axis_placement

Derived Associativity Data

The STEP associativity is defined but it is not as specific as the data held by the native CAD systems.

The STEP post-processors can look for possible relationships – such as tangent point or arc centre point – and can derive the level of information required by the CAD systems but it requires more work.

Complex PMI

Complex PMI

What does it mean to the user?

This applies to 6 holes

Diameter Dimension

Value 3.4

Max limit tolerance plus 0.08

Min limit tolerance -0.025

Depth of hole 6

Max limit tolerance on depth 0.5

Min limit tolerance on depth 0.0

Countersink Diameter 4.1

Max limit tolerance on countersink diameter 0.25

Min limit tolerance on countersink diameter 0.

Countersink included angle between 82 and 100 degrees

Screw Thread Definition “M4X0.7 – 6H” has a minimum depth of 4

Position tolerance for hole centre has diameter of 0.25

Projected Tolerance Zone has minimum height of 6

Position related to datums D, E, C (in that order)

What does it mean to UG NX

It is a diameter dimension

It has 6 text strings

What does it mean to UG NX

It is a diameter dimension

It has 6 text strings

What does it mean to UG NX

It is a diameter dimension

It has 6 text strings

It has a value text : “3.4”

It has a prefix text : “6X”

The other 4 texts are appended text

Most interesting is text object with 3 lines

“<#C><0>4.1<T+0.25! 0> X 82<$s>-100<$s>”

“M4X0.7-6H <#D>4 MIN”

“<&70><+><&10><+><0>0.25<P>6<+>D<+>E<+>C<+><&90>”

Interpreting the data

For STEP, this needs to be interpreted into a set of representation entities.

dimensional_size

plus_minus_tolerance

position_tolerance

Datums

Interpreting the data

For STEP, this needs to be interpreted into a set of representation entities.

dimensional_size

plus_minus_tolerance

position_tolerance

Datums

But these representation entities leave a lot of information which is not defined.

Interpreting the data

For STEP, this needs to be interpreted into a set of representation entities.

dimensional_size

plus_minus_tolerance

position_tolerance

Datums

Text Data is required to complete the semantic content. Representation data in itself is incomplete.

Full Part PMI

Top View of Part

Is it usable?

Complex PMI example

Saved View as Work View

User Creates sub-set of full PMI to be visible in view

STEP draughting model + camera model

The way that the presentation information is gathered together within a part is using a draughting model.

The geometry is defined within a shape representation. The draughting model references the geometry from the shape representation and can add additional annotation information in a single presentation.

The draughting model can also reference a camera model. The Recommended Practice will state that a draughting model containing a single camera model together with all or a subset of the PMI represents a saved view definition.

Draughting model linked to geometry

Extracted from the Polyline Recommended Practice Document

LOTAR Polyline Presentation Project

Objective : to create a Recommended Practice document for Polyline Presentation of PMI and to create processors for CATIA V5 and UG NX to demonstrate the capability.

Participants : US & European Aerospace companies, ProSTEP, Dassault Systemes and Theorem Solutions.

Status : RP document close to final draft, software in final testing stages.

Saved Views will be supported in the RP document but not in the initial software.

Objective : to create a Recommended Practice document for Semantic Presentation of PMI and to create processors for ProE Wildfire and UG NX to demonstrate the capability.

Participants : NIST, PDES, PTC and Theorem Solutions.

Status : RP document under development, software in early development stages.

Saved Views will be supported in the RP document and possibly in the software.

NIST Semantic Presentation Project

Complex PMI example reflected through STEP

Reflected via Polyline Presentation

Original

Reflected via Full Semantic Presentation

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Thank You

Questions?