An automatic approach for generating parametric models from topology-optimization results for three-axis CNC machining

Converting topology-optimization results into parametric models is crucial for manufacturing lightweight, high-stiffness products. However, currently available technologies cannot effectively automate and perform this conversion, especially for three-axis CNC machining. To bridge this gap, this study proposes an automatic approach for generating parametric models from topology-optimization results. First, integrating the machining characteristics of three-axis CNC machining, surface voxel accessibility analysis and different voxel clustering are carried out to determine the optimal machining directions and removable geometry of the (common) raw material model. Then, a parametric sketch contours generation method is presented for the removable geometry. This also provides the essential preparation for generating a parametric model by adding subtractive features to the raw material model. Particularly, a classified layered projection method is developed to ensure the final parametric model preserves the shape of the topology-optimization result as much as possible. This method can project and fit the removable geometry into quadratic curve sketch contours in a layer-by-layer scheme. Based on the sketch contour of each layer, the corresponding subtractive feature can be generated and added to the raw material model to remove the corresponding removable geometry. Performing this subtractive process layer by layer can generate the final parametric model of the topology-optimization result. Herein, certain constraints are also implemented during the subtractive process to ensure that the final model can preserve the stiffness of the topology-optimization result. Finally, the automatic conversion experiments on two complex and representative topology-optimization results show an average reduction of 19.3 % in maximum displacement (i.e., compliance) and an average increase of 45.2 % in mass as well as 28.4 % increase in volume when averaging the changes across both generated parametric models compared with their original topology-optimization results. The methodological comparisons also show that the presented approach has special benefits, including the ability to convert topology-optimization results automatically and effectively into parametric models, while maintaining stiffness and being processable by three-axis CNC machining.