International audienceThe development of a complete system of inspection and quality control of manufactured parts requires the coordination of a set of complex processes allowing data acquisition, their dimensional evaluation and their comparison with a reference model. By definition, the parts inspection is the comparison between measurement results and the theoretical surfaces definition in order to check the conformity after manufacturing phase. The automation of this function is currently based on alignment methods of measured points resulting from an acquisition process and these nominal surfaces, in a way that they ''fit best''. The distances between nominal surface and measured points (i.e. form defects) calculated after alignment stages are necessary for the correction of the manufacturing parameters (Henke, Summerhays, Baldwin, Cassou, & Brown, 1999). In this work, a method for automated control based on association of complex surfaces to a cloud points using the Iterative Closest Point (I.C.P.) algorithm for alignment stage is proposed. An industrial application concerning a tooth gear manufactured in our country's tractor engines is presented
Abstract:The aim of this study is to propose a 5-axis toolpath smoothing method in order to improve the quality of machined surfaces. Currently, toolpaths are commonly computed from CAD models presenting small geometrical discontinuities. These discontinuities may be caused by an insufficient quality of the CAD model (geometrical discontinuities) and the use of meshed surfaces (e.g. STL files). Normally, CAM systems generate linearly interpolated toolpaths. CNC options are then used on the machine to smooth the toolpath. The geometrical discontinuities of CAD models and linear toolpath interpolation may induce a unsmooth toolpath. This type of toolpath causes marks on the machined workpiece even if classical enhanced CNC options are used. Generally, these marks are unacceptable for the functionality of the workpiece. To reduce this problem, this study proposes a method to efficiently smooth toolpaths and consequently improve the obtained surface quality. The proposed method may be employed with high end controllers commonly used on 5-axis CNC machines. First, a five degree polynomial interpolation method is presented. This interpolation is computed to ensure geometrical continuity in the slope and curvature of the obtained toolpath. Next, a concatenation method is proposed to reduce the size of the CNC program and to improve the toolpath smoothness. Moreover, the purpose of this concatenation is to obtain an optimized repartition of points along the toolpath. Furthermore, in a reverse engineering process this method avoids surface reconstruction, decreasing the process time and improving the quality of the obtained surface. The efficiency of these methods is validated by the machining of biomedical prostheses. The CAD model used for the test is a meshed surface.2
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