<Figure 11—Insert between_shape_aspect.png> from research folder
<Caption> —>Figure 11 illustrates linked shape_aspect and geometric_representation_items for the “between specification” example.
<New paragraph>
The instance roles in the representation data set in Figure 11 are:
#12 is the model feature being referenced,
#1 is the between_shape_aspect,
#3 is “N” (and product_definitional is TRUE since it is on the surface),
#5 is “M” (and product_definitional is TRUE since it is on the surface),
#2 and #4 compose #1 with #3 and #5, respectively,
#9 is the actual point for “N”,
#8 is the actual point for “M”,
#13 is the polyline that is the path between “N” and “M”,
#6, #7, #14 bind geometric elements to persistently identifiable shape_aspect instances. In this example, the actual geometric model details of instance #12 are not provided. Many other options are possible, e.g., #8 and #9 could be point_on_surface ENTITY types and the basis surface would then be provided, typically some form of face geometry. Other structural options are possible in the geometric model but the methodology of binding geometric elements to shape_aspects using item_identified_representation_usage (or the subtype geometric_item_specific_usage) should be followed to permit persistent identification and to support the unambiguous composition of the model feature itself.
The receiving STEP interface software would extract the associated geometric data from the file into an internal CAD model, would store the between_shape_aspect in an internal GPS model with persistent associativity to the internal CAD model, and would transform the between_shape_aspect with the CAD system internal symbol generator into a presentation of the “N←→M” in the receiving system attached to the tolerance frame. The presentation arrangement would be controlled by ISO 16792 and ASME Y14.41-2012 but would not be an exact match of the presentation arrangement in the source system.
Acknowledgements
Figure nine provided by B. Fischer, TDP360 LLC. Copyright remains with Advanced Dimensional Management, LLC.
The contributions of the STEP PMI team are gratefully acknowledged, without whose generous contribution of time and knowledge this paper would not exist. They are in no particular order: Lothar Klein, Ed Paff, Bryan Fischer and Jochen Boy. The contributions of the CAX-IF team are gratefully acknowledged.
Concluding remarks
Needs work::::
Refer to testing (e.g., SFA paper)
What is in store for AP242 E2
What is coming down from Y14, TC10, TC 213
March along the ‘digital thread’
Mfg (cnc,…)
Inspection (QIF,…)
============Original content of concluding remarks====
This document described the updates to the STEP PMI Information Model accomplished with the publication of ISO 10303-242. The areas of management data, presentation, representation, persistent identification, model feature, requirements on design model geometric properties, dimensional tolerances, datum system, geometric tolerances, continuous_shape_aspect_exchange_scenario, and deprecated entities in ISO 10303-47 were addressed.
Areas to consider for follow-on projects for subsequent editions of ISO 10303-242 include additional GPS domain specific standards related to:threads, surface texture specifications, edge condition specifications, welding specifications, machining feature groups, and statistical process control specifications. Extending ISO 10303-59{#49576} recommended validation for new shape_aspects and for revolute shapes could be considered. Planned_characteristics / Requirement_assignment to PMI data, i.e., could be extended to include dimensional_size, dimensional_location, geometric_tolerance as members of assigned_requirement.item. Model critical feature characteristics (e.g., non- GPS PMI) as commonly communicated via association to numbered “balloons” on drawings is yet another area to consider.
Additional areas to consider for follow-on projects for AP 242 include the additional GPS domain specific standards related to:threads, surface texture specifications, edge condition specifications, welding specifications, machining feature groups,SPC specifications.
Extending ISO 10303-59 recommended validation for new shape_aspects and for revolute shapes.
Extend Planned_characteristics / requirement_assignment to GD&T data, i.e., include dimensional_size, dimensional_location, geometric_tolerance as members of assigned_requirement.item. This is the recognition gap again as no one thought to add those items to requirement_assigned_item “because they aren’t requirements they are notes, and anyway all data in the darned drawing is a requirement so what’s your beef?”
From Horst :
Model critical feature characteristics (e.g., non- GD&T PMI) as commonly communicated via association to numbered “balloons” on drawings. Is he asking for drawing exchange? only possible interpretation is that recognition gap must be addressed.
Bibliography placed here
Footnotes
[1] The details of the datum system information model differ from that proposed in{McCaleb, 1999, #9787}.
[2] CAD system support for associating a coordinate system with datum_system is evolving.