A general CNC manufacturing process can be categorized into subtractive manufacturing (SM) and additive manufacturing (AM) based on the manufacturing direction of materials. Even with modern Computer-Aided Manufacturing (CAM) system, it is still a challenging job to formulate a proper process planning of both manufacturing processes owing to the complicated kinematics of machine tools and other physical constraints, such as cutting force threshold of cutters.

Given a volume bounded by two freeform surfaces to be manufactured, process planning is to “slice” the volume into segments with one or multiple interface surfaces, each of which will be manufactured sequentially. The research is strived to develop a general interface surface modeling strategy to optimize the process plann...[ Read more ]

A general CNC manufacturing process can be categorized into subtractive manufacturing (SM) and additive manufacturing (AM) based on the manufacturing direction of materials. Even with modern Computer-Aided Manufacturing (CAM) system, it is still a challenging job to formulate a proper process planning of both manufacturing processes owing to the complicated kinematics of machine tools and other physical constraints, such as cutting force threshold of cutters.

Given a volume bounded by two freeform surfaces to be manufactured, process planning is to “slice” the volume into segments with one or multiple interface surfaces, each of which will be manufactured sequentially. The research is strived to develop a general interface surface modeling strategy to optimize the process planning of subtractive and additive manufacturing. The tradeoff between time efficiency and finished surface quality is the primary issue in both processes under the conventional layer-by-layer manufacturing paradigm. To alleviate the problem, after a thorough investigation of the characteristics of the two manufacturing processes, multivariate and morphing-based interface surface modeling strategies are proposed respectively catering to two different manufacturing requirements. The multivariate method models the interface surface as a B-spline surface with various control points. The shape of the surface can be easily and flexibly manipulated with the control points. Inspired by morphing technique, the morphing-based method parameterizes interface surface as a geometry metamorphosis between of the two end surfaces of the volume. Then, three different application scenarios utilizing the modeling schemes are presented: process planning optimization concerning both roughing and finishing, optimization of multi-pass machining process, and variable-depth curved layer printing framework.

In the attempt to minimize the total machining time of milling process, a two-process planning is considered where a single interface surface slices the whole cut volume into two processes, i.e., roughing and finishing process. The machining time of both processes crucially relies on the shape of interface surface. In the first scenario, the shape of the interface surface left after roughing is optimized subject to the kinematic capacities of the specific machine tool and the deflection cutting force threshold of a ball-end cutter. Following this work, a more general process planning with multiple interface surfaces is presented with the dynamic interface surface modeling scheme. The crux is to find a series of morphing parameters such that the total machining time is minimized. By introducing a layer-wise time indicator, a searching algorithm is implemented to greedily search for the next morphing parameter based on the current one. The preliminary computer simulations and real physical cutting experiments have been conducted for both methods resulting in substantial savings (+20%) in total machining time compared to conventional strategies adopted in academia or industry.

In the context of additive manufacturing, the similar dynamic interface surface modeling scheme is applied to a curved layer 3D printing. Together with variable-thickness thin-shell modeling and print path planning method, a variable-depth curved layer printing framework is proposed. Under the popular paradigm of FDM, computer simulations and experimental result have shown the potential of printing stair-step-free and variable-depth thin-shell structures with enhanced mechanical property and high productivity.