ISO 10303-47 pdf download – Industrial automation systems and integration一Product data representation and exchange一 Part 47: Integrated generic resource: Shape variation tolerances.
4.1 Introduction
The subject of the shape_a.spect_def.nilion schema is to provide dcfinitions ot the spatial characteristics of a shape that are required tor dimensionmg and lolerancing. This schema provides representations br a derived – shape_aspect and a datum. A derived_shape_aspect is a shape_aspect that is developed from the defined shape ot the product, but thai is not required for defining the product shape. A datum is a shape_ aspect that provide the origin 1mm where dimensions and tolerances arc referenced. A derived_shape_aspect and a datum are aspects of the shape that arc required tot dimensioning 4ud tolerancing the site. (tie locauon. the orientation. and the form of a product shape.
4.2 Fundamental concepts and assumptions
The product shape is the concept of shape as a property that characterizes a product. Geometric models and engineering drawings are formal methods used to represent the product shape. Dimensions and tolerances arc elements ol the product shape definition which arc independent trom how the shape is represented. Dimensions may he explicitly identified as part of (he shape characteristics, implicitly included in a geometric model that represents the shape, or explicitly presented in a two-dunensional drawing.
A shape aspect is an element of a product shape. Dimensions may be specified tor both the entire product shape and aspects of the shape. This schema augments the shape aspects and the relationships among then) as the definitional mechanism for specifying dimensions and tolerances. A shape_aspect. relationships between shape_aspect elements, and their specified dimensions and toicrances are always detlited in the context of the product shape property. These dimensions and tolerances caii be represented as elements of geomctric models or engineering drawings.
For the purpose ol ideittilying dimensions and tolerances, this schema speci lies the concept of a derived shapc_ aspect. A derived shape_aspect is a shape_aspect that is defined based on the specific way in which it relates to another shape aspect. The derived shape aspect is used in conjunction with their related shape aspect elements to specify dimensions and tolerances. The specific geometry that can represent the derived shape_aspect and a shape aspect that provide the dellnitional relationship are not in the scope of this schema.
5.4.3 dimensional_characteristic_representation
A dimeasi al_characteristic_representation is an association of an implicit dimension with an explicit non- geometric representation.
NOTE- A diimmsion fi a shape_aspect may be explicitly represented as an actuai value, a scaled value, a precision dependent value, or a pair of values that specify die upper and lower site limits. A dimensiosalcbaracteristk – – representation associates one of the above value types with the implicit dimension value that may he derived from the geometric representation of the chapeaspect.
EXPRESS specification:
ENTITY dimensional_characteristic_representation;
dimension : dimensional_characteristic;
representation shape_dimension_representation;
END_ENTITY;
Atthbute definitions:
dimension: an implicit measurement for which an explicit non-gcomctric representation is defined. representation: the explicit non-geometric representation assigned to the dimension.
5.4.4 dimensional_location
A dimensional_location specifies that a spatial constraint exists between two shape_aspect elements that are represented as a non-directed measure applied along a measurement path.
ISO 10303-47 pdf download – Industrial automation systems and integration一Product data representation and exchange一 Part 47: Integrated generic resource: Shape variation tolerances
