Machinable volume extraction for automatic process planning

This paper describes an algorithm to extract machinable volumes that need to be removed from a stock, given a boundary model of the part. 'Machinable' implies that these volumes are extracted and arranged in a hierarchy such that each volume in the list is accessible for machining after its preceding volume has been machined. These volumes can be used to automate process planning and NC tool path generation. The algorithm identifies the cavity volumes in the part with respect to outermost faces in the part and fills them with the appropriate primitive volume to obtain the stock from which the part can be realized. Unlike the decomposition-based approaches reported, this algorithm directly identifies primitive volumes that when combined form the cavity volumes corresponding to the machining features. Primitive volumes enable handling parts with interacting features and renders redundant the additional processing of machining features required to generate a NC tool path. The primitive machinable volumes are cuboids, wedges and collars. The algorithm handles both prismatic and cylindrical (turned) components. Results of implementation for prismatic and turned components are provided and the extension of the algorithm to handle preformed stock is discussed.