Trochoidal (TR) milling has been a popular means in NC machining for slotting operation, owing to its unique cyclic pattern that restricts the tool-workpiece engagement and hence reduces the cutting force load and helps heat dissipation. Especially when cutting extremely hard materials such as super titanium alloy, the TR tool path has been an excellent milling strategy for reducing tool wear and restraining heat generation. Nevertheless, there are still limitations in the traditional TR milling, e.g., unfavorable chip removal rate and cannot tackle 3D cases, since the planar circle is used as the TR tool path. In this research, we strive to give a comprehensive improvement to the TR machining method for promoting its feasibility and effectiveness.

First, for the 2D planar TR milling,...[ Read more ]

Trochoidal (TR) milling has been a popular means in NC machining for slotting operation, owing to its unique cyclic pattern that restricts the tool-workpiece engagement and hence reduces the cutting force load and helps heat dissipation. Especially when cutting extremely hard materials such as super titanium alloy, the TR tool path has been an excellent milling strategy for reducing tool wear and restraining heat generation. Nevertheless, there are still limitations in the traditional TR milling, e.g., unfavorable chip removal rate and cannot tackle 3D cases, since the planar circle is used as the TR tool path. In this research, we strive to give a comprehensive improvement to the TR machining method for promoting its feasibility and effectiveness.

First, for the 2D planar TR milling, the traditional circle tool path suffers from a longer total machining time due to its unfavorable chip removal rate. As an improvement to this quandary, a new type of TR pattern is proposed, which is applicable to an arbitrary complex slot with a curved boundary and varying width. This new type is more flexible to adjust, unlike the conventional circular type whose adjustment margin is severely limited. Then, towards the objective of minimizing the total machining time, optimization is performed to find the best tool path of the new TR pattern for the given slot, subject to the given threshold on the maximum cutter-workpiece engagement angle, which is the key to gauge the heat dissipation and cutting force.

Then, aiming at further extending the application of TR milling, we propose a novel five-axis TR flank milling strategy applicable to machining more complex 3D-shaped cavities. Rather than the traditional circular TR pattern, our proposed method can adaptively generate a spatial cubic curve-based cyclic five-axis tool path according to the given complex 3D cavity, and, subject to the given tool-workpiece engagement threshold, the material removal rate is maximized in the process of tool path generation.

Next, to further improve the machining performance of the TR milling, a TR tool path planning strategy considering the kinematic optimization is proposed considering the characteristics of machine tool. According to the capability of each motion axes, we strive to optimally allocate the machine tool movement in the TR machining process. Also, we further enhance the machining efficiency by adaptively adjusting the cutting depth and machining feed rate. Both computer simulation and physical cutting experiments are conducted and the preliminary results have given a definitive confirmation on the correctness and effectiveness of the proposed methods.

Finally, a variable-depth multi-layer machining strategy is adopted in the TR milling for machining deep freeform 3D slots. Aiming at minimizing the total cutting time, instead of conservatively dividing the slot into equi-depth layers, we strive to minimize the number of layers with variable layer depths while at the same time satisfying the two most critical physical constraints on the tool -- the tool deformation and the tool stress.