New STEP-NC-compliant system to automate process planning for the turning process

STEP-NC is a smart standard, developed by the International Organization for Standardization (ISO) as a substitute for the ISO 6983 G-code, because the language of the G-Code, normally used for computer numerical control (CNC), is qualified as being unable to link the CAD/CAM/CNC digital chain and meet the needs of modern intelligent manufacturing in terms of tractability, interoperability, flexibility, adaptability, and extensibility. The purpose of this work is to implement the new STEP-NC standard in a computer-aided process planning (CAPP) turning process to overcome the shortcomings of ISO 6893 G-code and enable the process to meet the demands of modern manufacturing. Therefore, the first objective of this paper is to design and implement a CAPP for the turning process, designated as CAPP-Turn, to ensure machining of rotational parts within this modern vision. However, to achieve the CAPP-Turn system, it is necessary to build a robust automatic manufacturing feature recognition (AMFR) module to establish full communication between the first two links of the digital chain, the design CAD and manufacturing CAM, by using a hybrid graph-rules method. The second objective of this work is to elaborate a new consistent-fast algorithm that allows one to extract the machining turning entities for parts with the most efficiency and complex geometry. It then becomes necessary to introduce the main machining entities defined within the framework of this standard and to explain the different parameters that are necessary for the unambiguous definition of these entities whether of a geometric, topological, or other nature. In fact, most of the AMFR systems presented in the literature are restricted to the external turning process and cannot handle parts with complex geometry and interacting features. Moreover, the frontal turning features are largely neglected in most of these systems, despite their importance for fulfilling certain functions in mechanical systems. This article first details the global architecture of the CAPP-Turn and clearly describes the interaction between the CAD part and STEP-NC output file. It then explains the model of the AMFR system, which encompasses (i) a parser module that translates geometric and topological data from a STEP AP203 CAD file into Python entity class objects; (ii) an AMFR that analyzes the objects created and applies predefined rules to construct all possible turning machining; and (iii) a module capable of distinguishing external features from internal, frontal features from axial, and handling interacting features from the simple features. After these steps, the AMFR provides all suitable sequencings for part machining. Finally, to demonstrate the potential advantages and power of the proposed AMFR, a selected part is chosen for testing. The result shows that the AMFR performs well in recognizing all types of features regardless of their type: internal or external, axial or frontal, simple or interacting.