Papers by Keyword: Geometrical Product Specification

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Authors: Ya Zhang, Jian Zhong Fu, Zi Chen Chen
Abstract: Measurement process has an important impact on the reliability of measurement. The reliability of measurement is weighed by measurement uncertainty. It is very difficult to estimate the uncertainty in the indirect measurements according to the transfer formula given by GUM (Guide to the Expression of Uncertainty in Measurement). Monte Carlo method was proposed to solve the problem of uncertainty estimation and seek suitable measurement process in the indirect measurements. The mathematical relation between the measurand and the direct measures is established firstly. Then Monte Carlo method was adopted to conduct the sampling and synthesis of measurement uncertainty contributors. At last, the measurement method was evaluated and improved according to Procedure for Uncertainty Management, which is given by next generation of GPS (Geometrical Product Specification). Experimental result shows that Monte Carlo Simulation method has a good application foreground in the uncertainty estimation and measurement process design.
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Authors: Min Zhang, Bart Boeckmans, Jean Pierre Kruth, Wim Dewulf, Zhao Yao Shi
Abstract: To gain a maximum benefit of high-speed optical scanning in the metrological calibration of emerging AM (Additive Manufacturing) fixtures it is necessary to investigate the metrology performance of laser line scanning in particular on coordinate measuring machines (CMMs) based on new generation of Geometrical Product Specification standard. A set of designed experiments was set up both on an actual fixture and artefacts manufactured by the Additive Manufacturing company, Materialise-RapidFit+. It enables to identify the influence of a fixture’s geometrical characteristic, material, colour, transparency and roughness, as well as of the alignment of the part coordinate system (PCS) mathematically relating to the machine coordinate system (MCS). Performance measures that were tracked included inspection accuracy, measuring repeatability and time consumption. Results demonstrate that the laser line scanning strategy enables to lower the time consumption in the order of 49% for a fixture with six locators mounted on it and a PC with 128GB RAM, especially providing a superior accuracy performance for complex geometries compared to a tactile measuring strategy.
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Authors: Kamil Kolařík, Zdenek Pala, Libor Beranek, Jiří Čapek, Zdenek Vyskocil, Nikolaj Ganev
Abstract: Nickel super-alloys are widely used in aerospace as material for turbine blades. Unfortunately, their machining is difficult since mechanical hardening and, consequently, extreme tool wear occur. Casting can no longer meet the requirements for precision, hence, the castings are being ground or milled. In this contribution, a quality check of the milled surface by several surface integrity parameters is proposed with respect to the surface structural inhomogeneities caused by mutual effect of plastic deformations and thermal fields during the cutting process. Castings from Inconel 738LC were milled with cutting conditions chosen by Design-Of-Experiments method and the resulting surfaces were assessed by non-destructive X-ray diffraction methods in several areas corresponding to various cutter orientation and work-piece angle. Surface integrity was described by macroscopic residual stresses, microstrains, grain sizes and phase composition. Mostly, favourable compressive surface residual stresses were observed in the cutting direction, grain sizes were distinctively smaller when the tool axis was perpendicular to the machined surface.
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Authors: Wojciech Płowucha, Władysław Jakubiec
Abstract: Long-lasting works on the ISO 15530 series can be a proof for complexity of uncertainty evaluation of coordinate measurements for different characteristics defined according to the rules of geometrical product specification (GPS). Even the best known procedures (using the calibrated workpiece and using computer simulation) have not been implemented widely. The authors have elaborated the methodology and the software (EMU-CMMUncertaintyTM) which makes possible evaluation of the measurement uncertainty with less effort. The software has been developed with following assumptions. Uncertainty budget includes influences of particular geometrical errors of the CMM, probing system errors as well as temperature errors. Applied algorithms use type B method according to the rules of GUM. Uncertainty is analysed separately for each characteristic (task-specific approach). Uncertainty of measurement for particular characteristic is calculated with the formula describing the characteristic as a function of differences of coordinates of characteristic points of the workpiece. The paper presents some new details concerning formulation of uncertainty budget. Among others the methodology is presented for estimation of uncertainty component arising from the fact that some characteristic points are not integral features (surface points) but derived features (axes points).
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