ISO 17450-1:2011 幾何学的製品仕様（GPS）—一般的な概念—パート1：幾何学的仕様と検証のモデル | ページ 6

3.1

実表面

物理的に存在し、ワークピース全体を周囲の媒体から分離する機能のセット

3.2

表面モデル

仮想ワークピースまたは実際のワークピースの一連の物理的限界を表すモデル

注記 1:このモデルはすべての閉じた曲面に適用されます。

注記 2:表面モデルでは、単一のフィーチャー、フィーチャーのセット、および/またはフィーチャーの一部を定義できます。製品全体は、各ワークピースに対応する一連のサーフェス モデルによってモデル化されます。

3.3

幾何学的特徴

ポイント、ライン、サーフェス、ボリューム、またはこれらのアイテムのセット

注記 1:非理想表面モデルは、特定のタイプの幾何学的特徴であり、ワークピースとその周囲の間の境界面を定義する点の無限のセットに対応します。

注記 2:幾何学的特徴は、理想的な特徴または非理想的な特徴である可能性があり、単一の特徴または複合特徴のいずれかと見なすことができます。

3.3.1

理想的な特徴

パラメータ化された方程式によって定義された機能

注記 1:パラメータ化された式の式は、理想的なフィーチャのタイプとその固有の特性に依存します。

注記 2:デフォルトでは、理想的な機能は無限です。その性質を変えるには、「制限された理想的な機能」のように「制限された」という用語を追加してこれを指定するのが適切です。

3.3.1.1

理想的な特徴の属性

理想的な要素に本質的に付随する特性

注記 1 理想的な特徴については，次の 4 つのレベルの属性を定義することができる。1) 形状。 2) 寸法フィーチャの場合、サイズを定義できる寸法パラメータ。 3) 状況機能; 4) スケルトン (サイズがゼロに設定されている場合)

注記2理想的な特徴がサイズの特徴である場合、形状のパラメーターの1つをサイズと見なすことができます。

3.3.1.1.1

寸法パラメータ

パラメータ化された式の式で使用される理想的なフィーチャの線形または角度寸法

注記 1寸法パラメータは，サイズの形体のサイズに対応することができる。

3.3.1.1.2

スケルトン フィーチャー

サイズがゼロに設定されている場合に、サイズのフィーチャーの縮小から生じる幾何学的フィーチャー。

注記 1公称モデルでは、スケルトン フィーチャーは公称積分フィーチャーの幾何学的属性です。名義積分特徴とその骨格は、同じ不変性クラスに属し、同じ状況特徴を持ちます。

注記 2非理想形体では、同じ一体形体に対して複数のスケルトン形体が存在する可能性があります。

例：

トーラスの場合、2 次元のパラメータがあり、そのうちの 1 つはサイズ (トーラスの小さい直径) です。その骨格は円です。その状況特徴は、平面 (円を含む) と点 (円の中心) です。

3.3.1.1.3

シチュエーション機能

幾何学的特徴の位置および/または方向を定義できる点、直線、平面、またはらせん

a)球の状況点

b)コーンの状況点

図 2 —状況直線の例

a)シリンダーの状況直線

b)コーンの状況直線

図 3 —シチュエーション プレーンの例

a)平面ペアの状況平面

b)コーンの状況平面

c)2 つの非平行平面の状況平面

図 4 —らせん状況の例

3.3.1.1.4

shape

mathematical generic description defining the ideal geometry of a feature

Note 1 to entry: An ideal feature of preset shape can be qualified or named.

3.3.1.2

invariance class

group of ideal features defined by the same displacement(s) of the ideal feature for which the feature is kept identical in the space

3.3.1.3

type

name given for a set of shapes of an ideal feature

Note 1 to entry: See Tables 2 and 5.

Note 2 to entry: From a type of an ideal feature, a particular feature can be defined by giving value(s) to intrinsic characteristic(s).

Note 3 to entry: The type defines the parametrized equation of the ideal feature.

3.3.1.4

nature

property of an ideal feature to be a point, a line, a surface, or a volume or a set of these items

3.3.1.5

feature of size

feature of linear size or feature of angular size

3.3.1.5.1

feature of linear size

feature of size with linear size

geometrical feature, having one or more intrinsic characteristics, only one of which may be considered as a variable parameter, that additionally is a member of a “one parameter family”, and obeys the monotonic containment property for that parameter

Note 1 to entry: A feature of size can be a sphere, a circle, two straight lines, two parallel opposite planes, a cylinder, a torus, etc. In former standards, wedges and cones were considered as features of size, and torus size was not mentioned.

Note 2 to entry: There are restrictions when there are more than one intrinsic characteristic (e.g. torus).

Note 3 to entry: A feature of size is particularly useful for the expression of material requirements, i.e. least material requirement (LMR) and maximum material requirement (MMR).

Note 4 to entry: In Figure 5, the diameter of the sphere is an example of a size of a feature of linear size; the geometrical feature used to establish the feature of size is its skeleton feature. In the case of the sphere, the skeleton feature is a point.

EXAMPLE 1:

A single cylindrical hole or shaft is a feature of linear size. Its linear size is its diameter.

EXAMPLE 2:

A compound feature consisting of two single parallel planes such as a groove or a key is a feature of linear size. Its linear size is its width.

Figure 5—Relation between the feature of size, the skeleton feature and the size

Key

1	size
2	cylinder
3	median feature
4	two opposite planes
5	skeleton: a straight line
6	skeleton: a plane
7	skeleton: a point
8	sphere
9	median feature
10	skeleton: a circle
11	situation feature
12	torus

3.3.2

non-ideal feature

imperfect geometrical feature fully dependent on the non-ideal surface model or on the real surface of the workpiece

Note 1 to entry: A non-ideal feature is by default of finite dimension.

3.3.3

nominal feature

ideal feature defined in the technical product documentation by the product designer

Note 1 to entry: A nominal feature is defined by the technical product documentation.

Note 2 to entry: A nominal feature can be finite or infinite; by default, it is finite.

3.3.4

real feature

geometrical feature corresponding to a part of the workpiece real surface

3.3.5

integral feature

geometrical feature belonging to the real surface of the workpiece or to a surface model

Note 1 to entry: An integral feature is intrinsically defined, e.g. skin of the workpiece.

Note 2 to entry: For a statement of specifications, geometrical features obtained from partition of the surface model or of real surface of workpiece shall be defined. These features, called “integral features”, are models of the different physical parts of the workpiece that have specific functions, especially those in contact with adjacent workpieces.

3.3.6

derived feature

geometrical feature, which does not exist physically on the real surface of the workpiece and which is not natively a nominal integral feature

Note 1 to entry: A derived feature can be established from a nominal feature, an associated feature, or an extracted feature. It is qualified respectively as a nominal derived feature, an associated derived feature, or an extracted derived feature.

Note 2 to entry: The centre point, the median line and the median surface defined from one or more integral features are types of derived features.

3.3.7

extracted feature

geometrical feature defining a set of finite number of points

Note 1 to entry: When the representativeness is defined by an infinite number of points, the word “extracted” is not associated with the considered terms.

Note 2 to entry: The concept “extracted” can apply to an integral feature or to a derived feature.

Note 3 to entry: An integral feature is by default an infinite representative, whereas an integral feature is extracted with a finite representative and performed in accordance with specified conventions.

3.3.8

associated feature

ideal feature established from a non-ideal surface model or from a real feature through an association operation

Note 1 to entry: An associated feature can be established from an derived feature (extracted, filtered), or an integral feature (real, extracted, filtered).

3.3.9

filtered feature

non-ideal feature which is the result of a filtration of a non-ideal feature

Note 1 to entry: Non-ideal filtered features exist. Nominal filtered features or associated filtered features do not exist.

Note 2 to entry: With regards to the function, the features considered are often not directly integral features, but integral features after a filtration.

Figure 6—Specification and verification filtered features

Key

1	non-ideal feature before filtration
2	filtered feature (non-ideal feature after filtration)

3.3.10

reconstructed feature

continuous geometrical feature defining a set of finite number of points

Note 1 to entry: When the representativeness is defined by an infinite number of points, the word “extracted” is not associated with the considered term.

Note 2 to entry: The concept “extracted” can apply to an integral feature or a derived feature.

Note 3 to entry: An integral feature is by default an infinite representative, whereas an integral feature is extracted with a finite representative and performed in accordance with specified conventions.

3.4

operation

specific tool required to obtain features or values of characteristics, their nominal value and their limit(s)

3.5

characteristic

single property defined from one or more geometrical feature(s)

Note 1 to entry: A characteristic is expressed in linear or angular units or without a unit.

3.6

specification

expression of permissible limits on a characteristic

3.7

variation

phenomenon whereby the value of a characteristic is not constant within one geometrical feature taken from one workpiece or within a set of workpieces

3.8

deviation

difference between the value of a characteristic obtained from the real surface of the workpiece or the non-ideal surface model and the corresponding nominal value