Plunge milling with constant scallop height by adaptively modifying the step interval for pocket wall

Abstract

Plunge milling plays an important role in machining of components with cavity structures. As a non-continuous material removal strategy, residual material is inevitably remained between two adjacent plunge cutter locations, also named as scallop. Large scallop height causes machining error, as well as fluctuations of cutting width in the following machining operation like semi-finish milling. As such, a constant scallop from plunge milling is essential to improve machining stability and tool life in following operation. In this paper, a new plunge milling toolpath generation method with adaptive interval is developed to restrict the maximum scallop height within a given value. Geometric relationship between plunge tool location and cusp of the constant scallop is firstly analyzed to determine the curves that the cusp of the constant scallop and plunge tool location located on. Then an iterative cusp of the constant scallop calculation algorithm is constructed based on the constructed geometric relationship. The next plunge tool location is obtained through a similar algorithm. Therefore, interval between current and its previous tool location is determined. In this way, the generated plunge milling toolpath can satisfy the given machining error allowance and keep a constant scallop height. It also has minimum number of plunge cutter locations to achieve maximum machining efficiency. Advantages of the proposed method are validated through a machining experiment by comparing the machining results with conventional plunge milling toolpath with constant step interval.