•The results of the tests carried out to validate a new method for evaluating the uncertainty of coordinate measurements categorised as the Sensitivity Analysis (SA) method.•General formulae are ...given to calculate the uncertainty of measurement of a circle diameter and coaxiality.•The relevant experiment is based on ISO 15530-3 recommendations.
The paper presents the results of the tests carried out to validate a new method for evaluating the uncertainty of coordinate measurements categorised as the Sensitivity Analysis (SA). This method concerns measuring dimensions and geometrical deviations. Measurement uncertainty is evaluated on the basis of information given in the Maximum Permissible Error (MPE) formula for a Coordinate Measuring Machine (CMM). Measurement models express the measured characteristics as a function of differences of coordinates of a small number of appropriately selected points of the workpiece. If reverification test results for the CMM used are available, then the estimated uncertainty takes into account the actual accuracy of the CMM. General formulae are given to calculate the uncertainty of measurement of a circle diameter and coaxiality. The relevant experiment is based on ISO 15530-3 recommendations. Acalibrated cylindrical square was used for validation. 17 circles’ diameters and 84 different combinations of datum length and distance of the toleranced element from the datum for measuring coaxiality were adopted as validated characteristics. The validation results are presented in tables and graphs and the chi-square test for equality of variances was used to confirm that the method is correct. The validation results are positive.
The paper is dedicated to the evaluation of the accuracy of rotary parts produced with the use of advanced manufacturing technology. The authors investigated the impact of the layer thickness of the ...applied material and the orientation of the model when printing using the PolyJet method™ on the geometrical quality of manufactured products. To analyze the influence of the assumed factors on the geometrical quality of the holes, a novel evaluation method has been developed. The proposed method takes into account parameters such as roundness deviation, profile irregularity coefficient, dominant harmonic component of the roundness profile, cylindricity deviation, diameter error, and surface topography parameters. The study presented in this paper had two main objectives. The former was to analyze the impact of the layer thickness of the applied material and the orientation of the model when printing using the PolyJet method™ on the geometrical quality of rotary parts. The latter objective was to test a novel, multi-parametric method of evaluation of the accuracy of produced parts in practice. The results obtained by the authors prove that the new evaluation method can be useful in the assessment of the accuracy of manufactured products.
The manufacturing process may lead non-rigid parts to endure large deformations which could be reduced during assembly. The manufacturing specifications of the single parts should refer to their free ...state or “as manufactured” state; the functional specifications should instead address the “as assembled” state. Therefore, a functional geometrical inspection requires dedicated fixtures to bring the parts in “as assembled” state. In this paper, through a linearized model that considers fixturing and elastic spring-back, we aim to correlate the functional specification to the manufacturing specifications. The model suggests a hybrid approach called “restricted skin model” that allows to reduce the degrees of freedom considering the form error when relevant. Firstly, the framework is verified in a mono-dimensional test case. Subsequently, it is verified including FEM simulation and actual measurement for two simple assemblies. The results show that the model can correctly interpret the theoretical assembly behaviour for actual applications. The use of the “restricted skin model” approach shows a negligible difference when compared to full FEM simulation with differences of 2.1 · 10
−7
mm for traslations and 6.0 · 10
−3
deg for rotations. The comparison with actual measurement values showed an error of ±0.2 mm at the assembly features. Furthermore, the linearized model allows a possible real-time application during production that enables to adjust manufacturing specification limits in case of process drifting.
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.
A research work is presented, carried out to validate a method based on sensitivity analysis for evaluating the uncertainty of CMM measurements. The fitness for purpose of cylinder squares for ...verifying the uncertainty evaluation of coaxiality measurements has been confirmed. Ring gauges too were used and found useful, but only as to its diameter. A type B method for predicting the uncertainty considering the actual technical condition of the CMM is proposed.
For more than twenty years, the international system for the geometrical tolerancing of components has been reformed. With the aim for a non-verbal specification and verification of components, the ...ISO system for Geometrical Product Specification and Verification (ISO GPS system) has emerged. Due to the necessary extensive specification language, which additionally contains mathematical descriptions, references, 3D specifications, defaults, rules for manufacturing and measurement etc., the ISO GPS system has now reached a complexity, which cannot easily be understood and decoded by the different engineers and departments in the companies, especially small and medium-sized enterprises as well as handicraft businesses. This makes an application in the entrepreneurial practice almost impossible. A structure and guidelines for the application are currently missing. Furthermore, there is a lack of requirements and a general approach for a necessary multi-layered training of specialists like engineers or machine workers as well as managers. There are also no generally accepted standards for the application of the ISO GPS system in companies. Often, small businesses, as contractors to large companies, have to deal with the challenges due to ISO GPS conform specifications. This problem has recently been amplified by the rapid progress of digitization and the increased use of 3D data including PMIs or application of 3D model-based definitions.
For this reason, an implementation strategy for an integrated GPS system for small and medium-sized enterprises has been developed as part of a current research project at the Chemnitz University of Technology. To overcome the difficulties caused by the complexity of the ISO GPS system, an agile training concept based on GPS competencies, a roadmap for the integration process, and a GPS maturity model for the assessment of the process have been developed. Fundamental results of the research project with focus on the development of the GPS maturity model for a transparent agile implementation process are presented in this paper.
A proposal for estimating the uncertainty of coordinate measurements is presented, which can be applied in industrial conditions. The basis is the sensitivity analysis method supplemented with an ...experiment with the use of a non-calibrated object. The measuring task modelling procedure for complex geometrical characteristics is described. The results of research on the correlation of experimental results and the sensitivity analysis results are given.
Geometrical features are fundamental elements for the fulfilment of the functional product requirements. Therefore, their inevitable deviations caused by manufacturing inaccuracies are the main ...issues in the field of tolerance management. To close the gap between physical part description and nominal model representation, the framework of discrete geometrical representatives via Skin Model Shapes has been developed and continuously enhanced. As the underlying concepts are based on final virtual parts, consistent inferences to every single manufacturing step are not fully investigated in literature.
This paper presents the development of Skin Model Shapes based on the virtual representation of intermediate part outcome (in-process geometry) and the integration of machining processes. Thus, integration and simulation of different kinds of deviations are enabled at each manufacturing stage considering error accumulation due to machine specific inaccuracies, such as tool movement and fixturing. Furthermore, the effect of inaccuracies on the final conformance result can be quantified at each manufacturing stage. A case study is presented to illustrate the entire approach and to demonstrate the validity of the proposed methods.
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