Tool path planning and chatter avoidance in curved surfaces machining

本研究的目的是对曲面加工中刀具轨迹规划进行基础研究和发展策略。这样的表面在许多工业零件中都会遇到，比如涡轮叶片、叶轮、工具和模具。这些表面的铣削操作，特别是在半精加工和精加工阶段，消耗相当多的时间。当部件准备好进行这些操作时，已经增加了一个重要的值。申请人进行的研究表明，需要制定刀具路径策略，以避免在后期阶段发生颤振，同时最大限度地提高金属去除率并使表面达到所需的粗糙度。建立颤振模型的一个关键因素是包括过程阻尼。这种阻尼出现在加工材料，如钛，在低速。申请人已经成功地建立了这样的车削操作模型，并设法解析地建立了稳定性叶。这些裂片表示切割的极限宽度与切割速度的关系。在这个项目中，开发的迭代方法来建立分析叶将扩展到铣削。颤振模型，包括过程阻尼，然后将应用于五轴侧铣削。

The objective of this proposal is to conduct fundamental investigations and to develop strategies for tool path planning in machining of curved surfaces. Such surfaces are encountered in numerous industrial parts like turbine blades, impellers, and tools and dies. Milling operations of these surfaces, especially in the semi-finishing and finishing stages, consume considerable time. A significant value has already been added by the time the part is ready for these operations. Research conducted by the applicant has shown that there is a need for developing tool path strategies to avoid chatter at those later stages while maximizing the metal removal rate and generating the surface at required roughness. A critical factor in developing a chatter model is to include process damping. This damping arises in machining materials, like Titanium, at low speeds. The applicant has successfully developed such model for turning operations and managed to establish the stability lobes analytically. These lobes show the limit width of cut against cutting speed. In this project, the developed iterative approach to establishing the analytical lobes will be extended to milling. The chatter model, including process damping, will then be applied to 5-axis flank milling. The developed chatter model will be integrated with the 3 ½ ½ machining strategy to generate the optimal number of surface subdivisions (patches), and feed directions while avoiding machining instability. In this strategy each patch is machined at fixed workpiece tilt angles. While it leads to higher rigidity and shorter machining time, it is more prone to gouging and interference as the tool moves across patches. In this project these problems will be addressed. The developed chatter model will also be integrated with tool positioning strategies in simultaneous 5-axis machining to optimize the tool path over the entire workpiece surface. The machine kinematics will be taken into account to help schedule the feed rate.All equipment necessary to conduct the experimental verifications is available in the Waterloo 5-axis machining lab.