GB/T 1958-2017Geometrical Product Specifications(GPS)—Geometrical tolerance—Verification (English PDF)

3.1 Integral feature

Lines on the face and face. [GB/T 18780.1-2002, definition 2.1.1]

Note: GB/T 18780.1-2002 also specifies terms such as nominal components, actual (composition) elements, extracted components, and fitted components.

3.2 Derived feature

A center point, center line, or center plane obtained from one or several components. [GB/T 18780.1-2002, definition 2.1.2]

Note: GB/T 18780.1-2002 also specifies the nominal export elements, extraction and export elements, and fitting and exporting elements.

3.3 Feature of size

A geometry determined by a linear or angular dimension of a certain size.

Note: Dimensional elements can be cylindrical, spherical, two parallel planes, conical or wedge shaped. [GB/T 18780.1-2002, definition 2.2]

3.4 Situation feature

A point, line, plane, or spiral class element that determines the direction and/or position of a feature. [GB/Z 24637.1-2009, definition 3.26]

3.5 Datum feature

The actual (composition) element on the part that is used to establish the baseline and actually act as a reference (eg, an edge, a surface, or a hole). [GB/T 17851-2010, definition 3.5]

3.6 Simulated datum feature

The actual surface used to create the datum and contact the actual datum element during processing and inspection with sufficient accuracy (eg one Plate, a support, a mandrel or benchmark target, etc.). [GB/T 17851-2010, definition 3.6]

3.7 Operation

A specific method of obtaining feature or feature values and their nominal and limit values. [GB/Z 24637.1-2009, definition 3.20]

3.8 Evaluation

The operation used to determine the eigenvalues, nominal values, and their limits. [GB/Z 24637.1-2009, definition 3.8]

3.9 Associated feature

The ideal element established by a non-ideal surface model or actual surface by a fitting operation. [GB/Z 24637.1-2009, definition 3.1]

3.10 Operation set; operator

An ordered set of operations. [GB/Z 24637.2-2009, definition 3.3.1]

3.11 Specification operation

Use only mathematical expressions, geometry, algorithms, or a combination thereof to clarify the operations that are expressed. [GB/Z 24637.2-2009, definition 3.2.1]

Note: The default specification operation, specific specification operation and actual specification operation are also specified in GB/Z 24637.2-2009.

3.12 Verification operation

The operation of the measurement process and/or the implementation process of the measuring instrument specified by the actual specification operation. [GB/Z 24637.2-2009, definition 3.2.5]

Note: The ideal inspection operation, the actual inspection operation and the simplified inspection operation are also specified in GB/Z 24637.2-2009.

3.13 Specification operation set

An ordered set of specification operations. [GB/Z 24637.2-2009, definition 3.3.3]

Note: GB/Z 24637.2-2009 also specifies the complete specification operation set, incomplete specification operation set, default specification operation set, specific specification operation set and real Inter-standard operation set.

3.14 Verification operation set

An ordered set of inspection operations. [GB/Z 24637.2-2009, definition 3.3.9]

Note: The ideal inspection operation set, simplified inspection operation set and actual inspection operation set are also specified in GB/Z 24637.2-2009.

3.15 Uncertainty

Characterizing a parameter that is reasonably assigned to a predetermined value or associated value, associated with a predetermined value or associated value. [GB/Z 24637.2-2009, definition 3.4.1]

Note: GB/Z 24637.2-2009 also specifies measurement uncertainty, specification uncertainty, correlation uncertainty, method uncertainty, and measurement instrument uncertainty. Degree, compliance uncertainty and total uncertainty.

7.1 Shape error and its evaluation

7.1.1 Shape error

The shape error is the amount of change of the extracted element of the measured element to its ideal element. The shape of the ideal element is theoretically the correct size or/and Parametric equation definition, the position of the ideal element is obtained by fitting the extracted elements of the measured element. Minimum area method C (Chebyshev method), least squares method G, minimum external method N and maximum inscribed method X, etc., related symbols in engineering drawings or technical documents And the description refers to Appendix A, Table A.1; if there is no corresponding symbol on the engineering drawing, the fitting method for obtaining the ideal element position is generally The default is the minimum area method, and the minimum area discrimination method is shown in Appendix D.

Note 1. The minimum area method and the least square method are classified into three cases according to different constraints. unconstrained (symbols are C and G) and extra-element constraints (symbol is CE) And GE) and intra-entity constraints (symbols for CI and GI).

Note 2. The parameters available for the evaluation of the shape error value are. peak-to-valley parameter (T), peak height parameter (P), valley depth parameter (V) and root mean square parameter (Q), in which the peak and valley parameters The number (T) is the default evaluation parameter.

Example: Figure 1, Figure 2 and Figure 3 show three different roundness pattern labeling examples and explanations. In Figure 1, the method of obtaining the ideal element position and the shape error The evaluation parameters of the difference are all based on the default labeling. The specification requires the minimum area method to fit the position of the ideal element. The peak-valley parameter T is used as the evaluation parameter. number. In Fig. 2, the symbol G indicates that the fitting method for obtaining the position of the ideal element adopts the least square method, and the evaluation parameter of the shape error value adopts the default labeling and evaluation. The parameter is the peak-to-valley parameter T. In Fig. 3, the symbol G indicates that the fitting method for obtaining the position of the ideal element adopts the least square method, and the symbol V indicates the value of the shape error value. The estimated parameter is the valley depth parameter.

7.1.2 Minimum area method for shape error assessment

The minimum area method refers to the method of fitting the extracted elements of the measured elements to the ideal element position by Chebyshev method (Chebyshev).

The method is that the maximum distance of the extracted elements of the measured feature relative to the ideal element is the smallest. Use this ideal element to contain the extracted elements of the measured elements When the minimum width f or the diameter d is contained, the containment area is referred to as a minimum containment area (referred to as a minimum area), as shown in FIGS. 4 and 5.

Note 1. Figure 4 shows the minimum area method for different constraints. unconstrained minimum area method (C), outer area constraint minimum area method (CE) and entity Minimum area method (CI) for inner constraints.

Note 2. The width f of the minimum area is equal to the distance between the highest peak point on the measured element and the ideal element (P) and the lowest valley point on the measured element. The sum of the distance values (V) of the primes (T); the diameter d of the smallest region is equal to twice the maximum distance from the point on the measured element to the ideal element.

Note 3. In general, the shape of the smallest area of each shape error item is consistent with the shape of the respective tolerance band, but the width (or diameter) is extracted from the measured The hormone itself determines.

7.2 Directional error and its assessment

7.2.1 Direction error

The direction error is the amount of variation of the extracted element of the measured element to the ideal element with a certain direction, and the direction of the ideal element is determined by the reference (and The theoretical correct size) is determined.

Note: When the direction tolerance value is followed by the maximum intrinsic ( ), minimum external ( ), least square ( ), minimum area ( ), paste ( ) and other symbols, It is the directional tolerance requirement of the fitting element of the measured element, otherwise it refers to the directional tolerance requirement of the measured element itself.

Example: Figure 6 is an example and explanation of the parallelism requirements for the attached features. The symbol indicates that this specification is the directional tolerance requirement for the fitted features of the measured feature. In the range of the measured length of the upper surface, the fitting element (or filtering element) of the measured element is fitted by the fitting method to obtain the fitting element of the measured element (ie. paste The cut factor) has a parallelism tolerance value of 0.1 mm with respect to the reference element A.

7.2.2 Evaluation of direction error

The direction error value is represented by the width or diameter of the directional minimum containment area (referred to as the directional minimum area). The minimum orientation area is used by Benchmarks and theories The correct size determines the direction of the ideal element to contain the extracted elements of the measured feature, the package with the smallest width f or diameter d The area is shown in Figure 7.

Note: The orientation minimum area shape of each direction error item is consistent with the shape of the respective tolerance band, but the width (or diameter) is determined by the measured extraction element itself. Decide.

7.3 Position error and its assessment

7.3.1 Position error

The position error is the amount of change of the extracted element of the measured element to the ideal element with the determined position, and the position of the ideal element is determined by the reference The theory is correctly sized.

Note: When the position tolerance value is followed by the maximum intrinsic ( ), minimum external ( ), least square ( ), minimum area ( ), paste ( ) and other symbols, Is the position tolerance requirement of the fitting element of the measured element; otherwise, it refers to the position tolerance requirement of the measured element itself.

7.3.2 Assessment of position error

The position error value is represented by the width f or the diameter d of the positioning minimum containment area (referred to as the minimum positioning area). The minimum location is Refers to the minimum width f or diameter when the extracted elements of the measured element are contained in the ideal element that determines the position by the reference and the theoretical correct size. The containment area of d is shown in Figure 8. […]