Geometrical Product Specification Research Articles

Form Deviation Uncertainty and Conformity Assessment on a Coordinate Measuring Machine

Coordinate measuring machines are widely used in the industrial field due to their ease of automation. However, estimating the measurement uncertainty is a delicate task, especially when controlling for deviation, given the large number of factors that influence the measurement. A precise estimate of the uncertainty is crucial to avoid incorrect conformity assessments. The purpose of this study is to control geometrical-form tolerance specifications, taking into consideration their associated uncertainty. A surface fitting model based on the least squares criterion is proposed, allowing one to obtain the variance–covariance matrix by iterative calculation according to the Levenberg–Marquard optimization method. The form deviation is then evaluated following the Geometrical Product Specifications (GPS) Standard, and its associated uncertainty is estimated using the guide to the expression of uncertainty in measurement (GUM) propagation of the uncertainty law. Finally, the conformity assessment is performed based on the measured deviation and its associated uncertainty. Different results for the measurement of straightness, flatness, circularity, roundness, and cylindricity are presented and detailed. This model is thereafter validated by a Monte Carlo simulation, and interlaboratory comparisons of the obtained results were performed, which showed satisfactory outcome. This contribution is of great use to manufacturing companies and metrology laboratories, allowing them to meet the normative guidelines, which stipulates that each measurement result must be accompanied by its associated uncertainty.

A new method for evaluating roundness error based on improved bat algorithm

Roundness error is one of the core indicators for evaluating the geometric accuracy of round parts mechanical products, directly affecting product performance and service life. In the field of metrology, the accurate, rapid and standardized assessment of roundness error has always been a hot topic. This paper proposed a new method for evaluating roundness error based on improved bat algorithm. This method was based on the new geometric product specification for extraction, filtering and fitting. Based on the advantages of solving optimization problems using the bat algorithm, transformed the roundness error evaluation problem using the minimum zone method into a problem of using the bat algorithm to find the center of the minimum zone circle, then further solved for the roundness error value. Also, this algorithm effectively avoided falling into local optimal solutions by introducing chaotic inertia weights during the velocity update phase, it improved the accuracy and speed of the evaluation. Introduced adaptive parameters during the loudness and emission rate update phases to enhance the algorithm’s global search capability, it enhanced the stability of the algorithm. The experimental results indicated, the efficiency of roundness error evaluation in the new method was significantly better than that of the genetic algorithm, the simplex algorithm and the emperor penguin algorithm. There was a significant improvement in evaluation accuracy and stability. The feasibility of this method in roundness error evaluation using the minimal zone method was validated.

Intercomparison to validate implementations of different laboratories of algorithms for the analysis of surface texture

The surface texture is an important feature of machine parts for any kind of contact. The quantification of its properties has been a well-established area in quality assurance for many decades. With the increasing demand for precision and interchangeability in the globalised marketplace, the results of surface analysis must be unambiguous and reliable. This is why the International Standardization’s Technical Committee on Geometric Product Specification has updated its standards. Consequently, instrument manufacturers and calibration laboratories need to ensure that their analysis software complies with the new ISO standards. An intercomparison has therefore been carried out to validate surface texture analysis software. Over the past two decades, a number of tests have been conducted on surface texture measurement and analysis methods, including issues of instrument response, discretisation and quantisation. This article examines the numerical and computational aspects of analysis algorithms that process data sets of discrete values of finite floating-point precision as input. The method of testing texture analysis algorithms utilising software measurement standards (softgauges) and the specification of the test tasks are explained. The results of the comparison are presented and discussed.

INTERPRETATION WORKFLOW OF GEOMETRIC TOLERANCES

The application of the principles of the geometric product specification (GPS) has increasing importance in the machining industry. The tolerancing process should harmonize the relationship between tolerancing, machining process, measuring and design requirements. The aim of the article is to present the interpretation process and the suggested workflow of geometric tolerances. The dimensional and geometric tolerances are compared, and some critical problems of geometric tolerancing are demonstrated by case studies.

Overview of Principles and Rules of Geometrical Product Specifications According to the Current ISO Standards

The article provides an overview of the philosophy of geometrical product specifications (GPS), which are, in addition to material specifications, a key component of effective planning and production of mechanical products as well as communication between partners in these processes. The principles and basic rules for precise and unambiguous specification of all requirements are embodied in a series of ISO GPS standards. It includes standards that describe the required accuracy of geometrical features of size and geometrical tolerances. An overview of the fundamental principles and rules imposed by the current ISO GPS standards and their content was carried out. This includes a description of the organization of the ISO GPS system and a summary of the content of the more relevant standards, which have recently undergone multiple revisions. The ISO GPS standards are based on the duality principle of specification and verification. In the present research, we focused primarily on geometrical specifications, while omitting the parallel pillar of verification, which, according to the ISO GPS matrix model, contains an even greater number of standards that define this area in more detail.

GPS-navigator: an advanced search engine to gather information and navigate through standards in the field of geometrical product specification

GPS-navigator: an advanced search engine to gather information and navigate through standards in the field of geometrical product specification

Handling the Functional Features of Accelerator Components Using ISO GPS Situation Features

The building blocks of a scientific facility based on particle beams comprise magnets and electro-magnetic devices. The optical design usually imposes a demanding accuracy with respect to their theoretically exact position and orientation. It happens that the functional features are either not clearly defined – what is the « axis » of a magnet –, or not explicitly used along their lifecycle. Improving how to handle these functional features would contribute to meeting demanding challenges. The European Spallation Source (ESS) is aiming at providing a powerful proton linear accelerator and a target system to produce pulsed neutrons. The challenging complex design and integration yielded to introducing a tool shared in common by all stakeholders along the lifecycle: the “situation features”, as defined in ISO GPS (Geometrical Product Specifications) standards. They are here developed, and extended to beyond-mechanics use cases. Two examples of fiducialization and installation phases are presented for neutron beam guides and quadrupole magnets. Perspectives of generic use are also highlighted.

GPS&V Textual Language

The ISO Technical Committee 213 (TC 213) develops standards about geometrical product specifications and verification (GPS&V). Those standards define both the meaning (semantic) and the writing (syntax) of specification indications used in Technical Product Documentation to control the size, geometry and surface texture deviation allowance on a mechanical part. The specification indications are defined as graphical symbols whose dimension and proportion are described in different ISO standards. The arrangement of those symbols is standardized so that reliable if not univocal information can be conveyed from the writer of the specification indication to the readers of the specification indication. This set of standardized rules constitutes a Graphical Language, primarily developed for humans widely used on two dimensional drawings or in three dimensional models. However, since the specifications are becoming more and more complex it is foreseen that the machines will be more involved in the communication process of the geometrical tolerancing information in the future. This paper describes in some details a context-free grammar that has been written to test the feasibility of a machine-readable Textual Language development.The grammar is based on the Universal Coded Character set (UCS). It shall be able to convey the same information as the current Graphical Language defined in ISO standards. The paper also reports on some testing tools that have been developed and made publicly available through a web interface. While this paper is only concerned with the syntax of the specification indications, some proposals are presented for an extended use of the grammar to check also semantic rules.

On Skin Model Describability using Laplace-Beltrami Operator for Geometrical Product Specification and Verification

The skin model serves as a foundational concept defined in ISO standards on Geometrical Product Specifications and verification (ISO GPS), facilitating the consideration of geometric variations on the surfaces of mechanical products. However, the lack of a solid scientific foundation and practical operational applications has become a barrier for skin model concept to keep up with the development of standardized feature operations. A previous investigation was devoted to a scientific approach to defining and interpreting the skin model for ISO GPS, grounded in the structure of solids and set theory. In this paper, the use of the Laplace-Beltrami Operator (LBO) is explored as a mathematical operation to enhance the computational representations of the skin model. The describability of skin model is achieved by applying LBO in both continuous and discrete cases. Geometric filter banks, established through LBO, are employed for skin model to identify defects at various scales of observation. An application of LBO is demonstrated through a case study to highlight the use of established geometric filter banks for skin model. Further discussions show that the spectral analysis of a surface using LBO enables the characterization of skin model, contributing to the current and future standardization of geometrical product specification and verification. Finally, conclusion and future works are highlighted.

Virtual-tutoring-supported teaching for Geometrical Product Specification

The digitalisation of education has developed in many areas in recent years with applications like web-based training and virtual seminars. In technical teaching areas, however, they are often only available as stand-alone solutions. Due to the possibilities brought about by the rapidly progressing development of artificial intelligence, the potential for digital teaching must be recognised and used. It is necessary to establish demand-oriented, intelligent control loops that support communication, knowledge transfer and learning level control. This will enable future generations to learn individually and thus increase the efficiency and sustainability of the teaching-learning process. As part of a current research project, a multimedia study format for the field of production measurement technology is being designed at Chemnitz University of Technology. A virtual tutor is an innovative element that guides, reminds, supports, informs, collects points and motivates learners individually with gamification elements.This paper presents the requirements, implementation possibilities and transferability of the current research of virtual-tutor-supported teaching to Geometrical Product Specification. It shows how knowledge elements of the ISO GPS system are linked with new digital teaching-learning methods that promote interaction between the participants and especially the transfer into applicable knowledge. In addition, examples of gamification elements are presented.

Comparative Analysis of ISO GPS Knowledge and Usage in the Italian Market

This research consists in a detailed analysis of the ISO Geometrical Product Specifications (GPS) system's knowledge and usage in Italy. Data was collected by means of a questionnaire, from a wide range of industrial sectors and academic institutions. The dataset encompasses 143 responses, forming the basis for an in-depth examination of ISO GPS system implementation in Italy. This analysis involves three levels of comparison: (1) an examination of knowledge level and typical usage between Beginners and Experienced individuals, (2) an investigation into ISO GPS adoption patterns in Industry and Academia, with and without specific ISO GPS training, and (3) an exploration of differences among professionals who are responsible for conveying geometric specifications and those in charge of interpreting and applying them. The findings reveal significant insights into ISO GPS implementation in both academic and industrial domains. They highlight the need for the improvement of ISO GPS education offer and the development of more effective utilization practices, with potential implications for future ISO GPS standards development strategies.

On Dealing with Outliers in Geometrical Measurements

Smart specification and verification of product geometry for manufacturing rely heavily on robust mathematical and computational support. This paper introduces statistical methods that are tailored to address the challenges facing the next generation of ISO GPS standards that govern geometrical product specification and verification. A key focus of this work is the handling of outliers, which are inevitable in industrial metrology. The paper begins by defining outliers based on established statistical literature, standards, and practices. It then explores the application of these concepts to the context of geometrical measurements in ISO GPS standards, while also considering the unique characteristics of structured multidimensional data under the Euclidean distance metric prevalent in this domain. By employing optimization theories and techniques in a unified formulation, the paper extends existing mean and rank-order statistical tools to present preliminary findings for structured data in multidimensions. Furthermore, it outlines potential future research directions concerning mathematical theories and computational techniques aimed at effectively applying median and rank-order statistics, and their incorporation into the future ISO GPS standards.

Evaluation of Students’ Measuring Capability in the Dimensional Control Laboratory Using R&R Procedure by Variables

Abstract The curriculum of technical bachelor programs often focuses on various theories in order to emphase understanding but there is also an actual need to provide the students with specific technical skills. This paper presents an effective means to evaluate the students’ capability to measure geometrical product specifications namely the procedure of Repeatability and Reproducibility by variables. The measurement results were processed using MINITAB statistical software with its module called Gage R&R Study. The conclusion was that the analyzed measurement system is excellent.

Optimization of 3D Tolerance Design Based on Cost–Quality–Sensitivity Analysis to the Deviation Domain

Under the new geometric product specification (GPS), a two-dimensional chain cannot completely guarantee quality of the product. To optimize the allocation of three-dimensional tolerances in the conceptual design stage, the geometric variations of the tolerance zone to the deviation domain will be mapped in this paper. The deviation-processing cost, deviation-quality loss cost, and deviation-sensitivity cost function relationships combined with the tolerance zone described by the small displacement torsor theory are discussed. Then, synchronous constraint of the function structure and tolerance is realized. Finally, an improved bat algorithm is used to solve the established three-dimensional tolerance mathematical model. A case study in the optimization of three-part tolerance design is used to illustrate the proposed model and algorithms. The performance and advantage of the proposed method are discussed in the end.

Perpendicularity assessment and uncertainty estimation using coordinate measuring machine

The validation of the conformity of parts according to the ISO 98-4 standard, cannot be achieved without an accurate estimation of the measurement uncertainty, which can become difficult when it comes to a complex measurement strategy to control a geometrical specification of a mechanical part using a Coordinate Measuring Machine (CMM). The purpose of the study in this paper is to analyze the measurement strategy following the Geometric Product Specification (GPS) Standard, to estimate the associated uncertainty of the different parameters of each step, to be able to achieve the uncertainty of the measurement of a given specification (perpendicularity error in our study) using the Guide to the expression of uncertainty in measurement (GUM). This uncertainty will be thereafter validated by a Monte Carlo simulation, and an interlaboratory comparison will be conducted to compare the obtained results according to the ISO 13528 standard. Our contribution is based on a more accurate estimation of the measurement strategy's parameters uncertainties. This approach can also be used by accredited calibration laboratories (ISO 17025) or in the general case in the control of perpendicularity specification of mechanical parts using a coordinate measuring machine. A case study has been conducted, controlling a perpendicularity specification with a tolerance limit of 15 µm, after the calibration of the CMM to obtain the variance-covariance matrices. The mechanical part perpendicularity error (12.55 µm) was below the limit, however, was judged “not conform” when considering the estimated uncertainty (4.06 µm) and the interlaboratory comparison was satisfactory despite the difference of the acceptance criterion.

Towards a Definition of “Geometric Verification Specifications” Within the ISO GPS System

The primary scope of tolerancing is to ensure functional requirements will be met by specifying geometrical tolerances. The duality principle, described within the ISO Geometrical Product Specification (GPS) standards, presents a perspective where the verification conceptually mirrors the specification. While this is a valuable model, further refinement is required to accommodate the different aims of inspection in support of the manufacturing process. This work aims to elaborate on the concept of a "geometrical verification specification" that is subordinate to the functional and/or manufacturing specifications. This verification specification may evolve as additional knowledge of the manufacturing process and inspection resources becomes available. A well-formed geometric verification specification should facilitate an appropriate inspection by any qualified operator, which in turn assures comparable measurement results across multiple instruments and facilities.

Estimation of parallelism measurement uncertainty according to the Geometrical Product Specifications standard using coordinate measuring machine

The dimensional and geometrical specifications control of a mechanical part is commonly done using a coordinate measuring machine. Collecting and processing measurement data through a probe, it allows measuring the conformity of the part according to specific tolerances. An accurate estimation of the uncertainty of measurement is critical; it is within this framework that our study is oriented; we aim to estimate the measurement uncertainty of parallelism error using the Guide to the Expression of Measurement Uncertainty (GUM), then we will proceed to a Monte Carlo simulation to compare the obtained uncertainty, we will then proceed to an inter-laboratory comparison to validate our model. Our contribution is based on a more detailed and precise estimation of the uncertainties of the measurement process taking into accounts the calibration of the machine and the propagation of uncertainties.

Use of geometrical product specifications in the structural design of second generation bearing hub unit

The article discusses selected issues of the application of ISO GPS standards and their use in defining the specifications of designed products. Their importance in meeting the functional requirements specified by the designer and expected by the user is highlighted. This was presented on the example of a comparative analysis of the design of a second-generation composite bearing hub, which is a modification of a double-race angular contact ball bearing. A comparison of the ways in which the requirements of the more important dimensions are specified was made according to ISO 492:2002 and ISO 492:2014. Verification of the requirements description according to the GPS will be carried out during the manufacturing process of the bearing hub unit.

Virtual task-specific measurement uncertainty determination for laser scanning

The framework of the Geometrical Product Specification defines the nominal geometry of the components and the characteristic tolerances. Various ISO standards describe the nine defined geometrical properties per characteristic of a workpiece. To prove conformance to the task specific tolerances according ISO 14253–1, the uncertainty budget needs to be determined. This paper presents a digital twin of an optical measurement system as a holistic concept to perform the task specific uncertainty determination. Different measurement strategies are applied to illustrate their effect on the measurement uncertainty of geometrical properties. Not all geometrical properties are relevant for an optical measurement system. Therefore, the discussed properties as a function of the optical measurement strategy in this paper are: size, distance, form and orientation.

Tolerance analysis method considering multifactor coupling based on the Jacobian–torsor model

Assembly quality affects the performance of mechanical products and reasonable tolerance designs are central to assembly quality. Unreasonable tolerance design leads to the mechanical equipment performance degradation under complex operating conditions. This study developed a novel tolerance analysis method that considers the influence of temperature, load, and other environmental factors based on the Jacobian–torsor and skin models. First, the deformation caused by multifactor coupling was analyzed using the finite element method, and the feature surface of deformation is extracted. Second, the deformation extraction and tolerance conversion based on the new generation geometrical product specification theory was used to convert the deformation of the feature into the dimension, orientation, and form tolerance. Third, the modified Jacobian–torsor model considering multifactor coupling was constructed by superimposing the converted tolerance with the design tolerances. Finally, the abrasion problem of the airborne actuator was considered as an example to verify the effectiveness and accuracy of the novel method. Through the accurate calculation of tolerances, it accurately analyzes the assembly state of the product under the influence of environmental factors, and provides more accurate guidance for the design and optimization of product tolerance in complex working conditions.