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The influence of CAD model continuity on accuracy and productivity of CNC machining

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Abstract

Efficient and productive manufacturing of freeform shapes requires a suitable three-dimensional CAD model at the entrance to the CAM system. The paper deals with the impact of NURBS or B-spline CAD model geometric continuity on the accuracy and productivity of 5-axis ball-end milling of freeform surfaces. The relationship between a different order of CAD model geometric continuity and the quality of the toolpath generated in CAM system is analysed and demonstrated on an example of a Blisk blade profile. In order to reveal the effect of CAD geometry on the quality of the machined surface, linear interpolation of cutter location points, i.e. piecewise linear discrete toolpath, is considered. Also, no further smoothing of the toolpath is applied. The distance of the cutter location points is commonly used as the indicator of toolpath quality. In addition, the discrete curvature of a linear discrete toolpath is introduced here, and its dependence on the curvature and continuity of the underlying CAD model is demonstrated. In this paper, it is shown that increasing the order of CAD model geometric continuity significantly eliminates sharp changes in the distance of cutter location points, and smoothes the discrete curvature of the toolpath. Finally, it is experimentally verified that increasing the continuity of the CAD model from G0 to G3, while maintaining the same cutting conditions, leads to an increase in workpiece accuracy and a reduction in machining time, without the need to smooth the toolpath generated in the CAM system.

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Funding

This work was supported by the Student Grant Competition of the Czech Technical University in Prague, grant Applications of mathematical-geometric modelling in mechanical engineering SGS21/148/OHK2/3T/12 (authors David Kučera and Ivana Linkeová) and grant Research and improvement of intelligent production machines and systems SGS22/159/OHK2/3T/12 (author Michal Stejskal).

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Authors and Affiliations

  1. Department of Technical Mathematics, Faculty of Mechanical Engineering, Czech Technical University in Prague, Karlovo nám. 13, Prague, 12135, Czech Republic

    David Kučera & Ivana Linkeová

  2. Department of Production Machines and Equipment (RCMT), Faculty of Mechanical Engineering, Czech Technical University in Prague, Horská 3, Prague, 12800, Czech Republic

    Michal Stejskal

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  1. David Kučera
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  2. Ivana Linkeová
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  3. Michal Stejskal
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Correspondence to Ivana Linkeová.

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All authors contributed to the study conception and design. Material preparation, data collection and analysis were performed by all authors. The first draft of the manuscript was written by all authors and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.

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Kučera, D., Linkeová, I. & Stejskal, M. The influence of CAD model continuity on accuracy and productivity of CNC machining. Int J Adv Manuf Technol 124, 1115–1128 (2023). https://doi.org/10.1007/s00170-022-10422-w

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