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Problems solved by technology
[0002] A common problem in the assembly process of precision / ultra-precision mechanical systems: In the case of qualified parts processing, the accuracy of the assembled system cannot meet the design requirements, and the assembly success rate is low
Therefore, the established geometric error model cannot be applied in assembly simulation, and its influence on assembly accuracy and assembly performance is analyzed.
[0005] In product assembly design and analysis, the impact of part surface processing errors on assembly is usually only calculated for the impact of part size errors on product assembly quality, while the shape and position errors and surface errors of parts are ignored. At the same time, the current part entity modeling Technology cannot unify the geometric error information of the machined surface into the CAD model, which loses the accuracy of assembly simulation analysis
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Embodiment 1
[0031] (1) To measure the geometrical error data of the surface of the part, using appropriate digital measurement methods to obtain accurate actual part surface data is the most basic link in the modeling of geometrical error. Use high-precision measuring instruments such as three-coordinate measuring machines to measure parts. The actual surface is machined, and the measurement data of the double-ordered topological rectangular mesh feature on the surface of the machined part is obtained;
[0032] (2) Preprocessing of measurement data, performing probe radius compensation on the measured data, and eliminating bad points to obtain regular measurement data points on the surface of the part, that is, the shape value point Q k,l (k=0,1,…,n; l=0,1,…,m), rectangular field value The number of data points in two directions of grid points is n+1, m+1;
[0033] (3) Randomly determine the degree of NURBS surface as p and q, and the shape point Q k,l The weight factor is w k,l =1;
...
Embodiment 2
[0058] (1) Using a high-precision three-coordinate measuring machine to collect data on a milling plane on a flat part, the size of the flat part is 120cm×60m×15m, the three-coordinate measurement accuracy is: (2.2+L / 330)um, and the measurement method is: For contact measurement, the probe radius of the measuring probe used in the three coordinates is 1.5mm. The sampling interval is: 5mm, and the three-dimensional coordinates XYZ of 253 measurement points in 23 rows and 11 columns with topological rectangular grid features are obtained, such as figure 2 shown;
[0059] (2) Preprocessing of the measurement data, performing probe radius compensation on the measured data, and eliminating the bad points to obtain the regularized measurement data points on the surface of the part, that is, 23 × 11 type value points Q k,l (k=0,1,...,n; l=0,1,...,m), n=22, m=10, such as figure 2 (b);
[0060] (2) Determine the degree of the NURBS surface as p=3 and q=3, and the type value point ...
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Abstract
The invention discloses an NURBS curved surface reconstruction-based geometric error representation method. The method comprises the following steps of performing geometric error data measurement on the surface of a to-be-processed part to obtain measurement data, with double ordered topologic rectangular mesh characteristics, of the surface of the processed part; performing measurement head radius compensation for the measurement data, and removing bad points to obtain a part surface regularized measurement data point matrix, namely, data points; randomly determining a frequency of an NURBS curved surface and weight factors of the data points; performing parameterization on the data points in a row direction u and a column direction v by adopting an AVG technology; performing NURBS curved surface interpolation to obtain all control vertex coordinates; and building a real geometric shape error mathematic model of the surface of the to-be-processed part by adopting an NURBS curved surface interpolation reconstruction technology, and generating a geometric error curved surface model through forward calculation.
Description
technical field [0001] The invention belongs to the field of test equipment, and in particular relates to a geometric error characterization method based on NURBS surface reconstruction. Background technique [0002] A common problem in the assembly process of precision / ultra-precision mechanical systems: in the case of qualified parts and components, the accuracy of the assembled system cannot meet the design requirements, and the assembly success rate is low. One of the main reasons is that the surface of machined parts actually always has some geometric errors, and its surface is microscopically composed of many many peaks and valleys of different sizes and shapes. The influence of the geometric error of the part surface on the assembly quality is mainly reflected in the influence of the irregular asperities on the surface of the part on the fitting properties and fitting accuracy. In order to study the influence of geometric errors on assembly accuracy, the geometric er...
Claims
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