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Title: Stability Performance of a Stochastic Toolpath in Machining
The overall quality of a machined part relies heavily on the tool path that is used. Several methods of toolpath generation are currently employed. A more recently developed toolpath method is known as trochoidal milling, which is also known by several other terms, such as adaptive milling. This type of path benefits the machining process by attempting to reduce chip thickness on entry and exit to the workpiece. In doing so, utilization of this type of path can reduce tool wear and enables higher feed rates, thus improving machining efficiency.\par Another advantage of the trochoidal approach is that it often creates paths which are relatively more smooth compared to traditionally designed paths. In order to follow the contours of the final geometry, the path can yield a significant number of direction changes which result in constantly changing forces directions on the tool. Chatter, or self-excited vibration that occurs in the tool or workpiece, can therefore be mitigated or avoided since resonance does not have time to increase the vibration’s amplitude. The trochoidal milling tool path strategy typically operates on the XY plane. The operator will assign a step-down value, which defines the Z-depth at each pass. This strategy can create issues during freeform milling: because of this step-down effect, the trochoidal path may only be able to perform clearing and not finishing. This is due to the excess material left on the workpiece when a large step-down value is used. A significant and randomized variation range of the trochoidal path is tested in this research. Using this new proposed method, stochastic behavior of the toolpath is implemented. The toolpath consists entirely of circular arcs which drive the tool in a pseudo-random fashion. As the tool nears completion of the pass, the generator will give heavier probabilistic weight to points which have not yet been machined, thereby improving the efficiency of the process. It is hypothesized that this toolpath can generate the same chip-inhibiting properties of the trochoidal path while granting the ability to perform finishing cuts. The stability of such a path is determined in this work. A key parameter of this path is the allowable radius range of the circular arcs. For example, short, tight arcs or long, relatively straight arcs can be used. The influence of these arcs is analyzed against several different metrics, such as generation time, path efficiency, and chatter. The stability lobes for several radii parameters were determined. It was found that the most efficient path utilized a median parameter value, signifying a negative parabolic relationship between path efficiency and tool path radius. It was also discovered that smaller arcs result in decreased chatter. Future studies will explore the behaviors of this path when milling 3D surfaces.  more » « less
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Proceedings of ASME International Mechanical Engineering Conference and Exposition
Medium: X
Sponsoring Org:
National Science Foundation
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