The overall quality of a machined part relies heavily on the tool path that is used. Several methods of toolpath generation are currently used. 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 operates 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 machining at higher feed rates, thus improving machining efficiency.Another advantage of the trochoidal path 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 result in a significant number of curves. When progressing through these curves, the force vectors acting on the tool will be constantly changing. Chatter, which is a self-excited vibration that occurs in the tool or workpiece, can be 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 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 variation of the trochoidal path is tested in this research. In this new method, stochastic behavior of the toolpath is implemented. The toolpath consists entirely of circular arcs which traverse the tool in a pseudo-random fashion. As the tool nears completion of the pass, the generator will target points which have not yet been machined, 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 approximate radius 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.

Stability Performance of a Stochastic Toolpath in Machining

Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2021/volume/85543

ASME 2021 International Mechanical Engineering Congress and Exposition (IMECE2021)

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