Digital Twin has become a frontier research topic in recent years and the important development direction of intelligent manufacturing. For numerical control machining, a Digital Twin system can be used as an intelligent monitoring and analysis center by reflecting the real machining process in a virtual environment. The machining simulation is the key technology to realize this kind of application. However, existing machining simulation systems are designed for off-line situation that cannot be used directly in Digital Twin environment. The challenges for machining simulation are analyzed and explained in this article: (1) complete process data representation in simulation system; (2) executing in cooperating with computer numerical control system; (3) more efficient simulation algorithm. In order to meet these challenges, a new machining simulation system is proposed. STEP-NC standard is used to save complete process data exported from the computer-aided manufacturing system and synchronization algorithm is developed based on the communication data of computer numerical control system. Most importantly, an optimized tri-dexel-based machining simulation algorithm is developed to perform high efficiency that can follow the real machining process. Finally, a Digital Twin system for NC machining is presented that has been tested and verified in a workshop located in COMAC (Commercial Aircraft Corporation of China Ltd).

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Design and manufacturing of composite structures are driving the next generation innovation cycles for the aerospace, automotive and energy markets. Automated fiber placement (AFP) is quickly becoming the preferred manufacturing method of those structures as it offers manufacturing automation, reduces production cycle times, and decreases human induced errors. One of the major steps towards manufacturing structures with AFP technology is the selection of the optimal layup strategy. This is limited by, not only geometrical and process parameters, but certification allowable and guidelines. This paper outlines a systematic review of the multiple layup strategies practices currently used and/or investigated for the AFP manufacturing process. The optimal layup strategy needs to be selected and verified to obtain laminates with little to no manufacturing defects. Through a methodical description, the different layup strategies found in the literature are described as well as their mathematical implementation. Following, a geometrical benchmark is presented so that new layup strategies can be compared to others based on the same reference. The article can be the foundation for any new layup strategy investigation.

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