Process planning utilizing a non-spherical cutting tool for multi-axis machining of complex parts

Abstract

Multi-axis machining is widely used in the manufacturing industry, and one common technique is multi-axis milling. This process is known for its flexibility and accuracy. When machining complex freeform parts, using a non-spherical tool can greatly improve efficiency by adjusting the tool posture to maximize contact with the part surface. However, there is limited research on non-spherical cutting tools, and no reported works on iso-scallop height five-axis tool path generation for a non-spherical tool. In this thesis, three process planning methods are proposed for 3+2-axis and 5-axis machining of complex parts using non-spherical cutting tools. First, we propose a partition-based 3 + 2-axis strategy for machining general complex freeform surfaces with a non-spherical tool. This approach requires only a finite number of distinct tool orientations, making it suitable for a three-axis machine tool instead of an expensive five-axis machine tool. Additionally, using a three-axis machine tool improves rigidity, enhancing the kinematics, dynamics, and machining accuracy. Next, we present path planning method to generate iso-scallop height tool paths for 5-axis machining using non-spherical cutting tools. Specifically, we first define and construct two fields on the surface to be machined-the collision-free tool orientation field (vector) and the iso-scallop height distance field (scalar). The iso-lines of the scalar field and their associated tool orientation field vectors then naturally serve as potential iso-scallop height five-axis tool paths, and we present a propagation-based algorithm to construct the desired tool path from the iso-lines. The computer simulation and physical cutting experiments confirm that everywhere on the surface, except maybe near the saddle curves of the scalar filed, the scallop height is exactly the given threshold. By adding the saddle curves as extra tool paths, the final machined surface then is assured of the required scallop height requirement. Finally, we present a partition-based 5-axis machining method for non-spherical cutting tools. We first define three indicators to partition the surface with respect to cutting width and collision situations where the Leiden method is used for clustering-based partitioning. Two-phase solution are proposed to improve the cutting efficiency further. In the first phase, the tool orientations inside each subregion are smoothed under the consideration of enlarging the cutting width. In the second phase, the iso-scallop height tool paths are generated in each subregion, and feed directions are restricted as perpendicular to the tool orientations as possible, as can maximize the cutting width. The computer simulation and physical cutting experiments confirm that everywhere on the surface, except maybe near the saddle curves of the scalar filed, the scallop height is exactly the given threshold. By adding the saddle curves as extra tool paths, the final machined surface then is assured of the required scallop height requirement.

Date of Award	2024
Original language	English
Awarding Institution	The Hong Kong University of Science and Technology
Supervisor	Kai TANG (Supervisor)