Generation Geometrical Product Specification Research Articles

Implementation uncertainty evaluation of cylindricity errors based on geometrical product specification (GPS)

Cylindrical feature has become one of the most important features in mechanical designs. It is essential to establish a proper model for evaluating cylindricity error to ensure achieving accurate assessment based on the new generation geometrical product specification (GPS). In this paper we developed a method for uncertainty evaluation of cylindricity errors. This method is based on the particle swarm optimization (PSO) algorithm and the uncertainty theory in new generation GPS to address the issues involved in uncertainty in new GPS system. The association operation in GPS was used as an evaluation method for cylindricity error. One of the advantages of the proposed approach is that the PSO algorithm has faster convergence speed and calculating precision, the evaluation results are more accurate and accord with requirements of new generation GPS standard. We present an example to describe how uncertainty can be used as an economic tool to help commercial transactions where the workpiece is evaluated against the specification. The result indicates that the proposed method can improve the veracity of evaluation.

Evaluation and management procedure of measurement uncertainty in new generation geometrical product specification (GPS)

Because of measurement errors objectively existing, measurement results always deviate from the “true value” of the measurand. Measurement uncertainty, as a quality index characterizing measurement results, attracts wide attention in the world. Unifying the evaluation of uncertainty and its expression will help understand measurement results, and promote international technical and commercial communication. According to the International Organization for Standardization ISO/BIPM “Guide to the Expression of Uncertainty in Measurement” – usually referred to as the GUM, which was published in 1993, this paper deals systematically with the way of evaluation and expression of measurement uncertainties. It expands the concept and meaning of measurement uncertainties, and normalizes the Procedure for Uncertainty of Measurement MAnagement (PUMA) by using new thoughts based on the GUM and the systematic quantifying-unifying in the new generation Geometrical Product Specification (GPS). Furthermore, the concept of uncertainty has been expanded to the whole GPS system beyond just measurement uncertainty, and the functions, specifications and measurement verification of workpieces are quantified and integrated by using the statistic and quantificational characteristic of expanded uncertainty. The optimum allocation of resources amongst specification, manufacturing and verification is realized, the total efficiency of products is increased by the adjustment function of uncertainty as an economic tool.

Research on the uncertainties from different form error evaluation methods by CMM sampling

As a part of the new measurement uncertainty system proposed in the new generation of Geometrical Product Specifications and Verification, the evaluation methods of uncertainties to form errors have been researched in mechanical engineering, which are calculated based on the error propagation principle and statistical concept under certain conditions. In this paper, the evaluation datum is obtained by using both the least squares method and the genetic optimization algorithm. Their computation uncertainties to flatness and roundness were compared with each other using the sample data from a coordinate measurement machine (CMM). The results show that the uncertainties obtained from the genetic algorithm-based method are similar to those from the least squares method according to their evaluation parameters. The evaluation uncertainties from different methods become a little smaller with more sample points. A more significant conclusion is that the evaluation uncertainties from two methods are so small that they almost do not affect the measurement uncertainties to form error, which, in fact, mainly comes from the CMM sampling. Therefore, for the efficiency and simplification of calculation, especially for the cylintricity with more parameters, the uncertainties from evaluation methods can be neglected where the precision is not so strict.

A Surface Texture Information System Integrated with AutoCAD for Next Generation GPS

To meet the requirements of next generation Geometrical Product Specification and Verification (GPS), a surface texture information system integrated with AutoCAD is developed. The information system mainly consists of three parts: a surface texture database containing large amount of surface texture specification information, inference algorithms and interfaces with AutoCAD, so that unambiguous, explicit and complete specification for design, manufacture and verification of surface texture can be provided in AutoCAD for function assurance.