@article{cai_wang_burnett_2020, title={Using augmented reality to build digital twin for reconfigurable additive manufacturing system}, volume={56}, ISSN={["1878-6642"]}, DOI={10.1016/j.jmsy.2020.04.005}, abstractNote={The extrusion-based additive manufacturing (AM) processes are those where one or multiple tools (usually nozzles) are driven along predefined paths to deposit fabrication materials. They are usually inherently slow because solid contours have to be filled with mere single deposition lines of material. An intuitive way to improve the fabrication speed is to introduce multiple independent actuators for concurrent deposition of materials without collision among them. In this paper, a methodology of using augmented reality (AR) technique is presented to conveniently communicate the layout information between a reconfigurable AM system made of robotic arms and its corresponding digital twin for toolpath planning and simulation. A prototype system made of two desktops AM robotic arms is developed, and transformation matrices are derived to determine the spatial relation between different items in the system, including camera, markers, robotic arms and part substrate. Case studies are conducted to demonstrate the capability of this methodology in automatically retrieving layout information and assisting users to deploy pre-determined layout. The results show that the developed methodology enables rapid retrieval of position information from the physical system layout into the digital twin simulation and optimization and facilitates convenient deployment of an optimized layout determined in the digital twin into the physical system.}, journal={JOURNAL OF MANUFACTURING SYSTEMS}, author={Cai, Yi and Wang, Yi and Burnett, Morice}, year={2020}, month={Jul}, pages={598–604} }
 @article{zhang_starly_cai_cohen_lee_2017, title={Particle learning in online tool wear diagnosis and prognosis}, volume={28}, ISSN={["1526-6125"]}, DOI={10.1016/j.jmapro.2017.04.012}, abstractNote={Automated Tool condition monitoring is critical in intelligent manufacturing to improve both productivity and sustainability of manufacturing operations. Estimation of tool wear in real-time for critical machining operations can improve part quality and reduce scrap rates. This paper proposes a probabilistic method based on a Particle Learning (PL) approach by building a linear system transition function whose parameters are updated through online in-process observations of the machining process. By applying PL, the method helps to avoid developing a complex closed form formulation for a specific tool wear model. It increases the robustness of the algorithm and reduces the time complexity of computation. The application of the PL approach is tested using experiments performed on a milling machine. We have demonstrated one-step and two-step look ahead tool wear state prediction using online indirect measurements obtained from vibration signals. Additionally, the study also estimates remaining useful life (RUL) of the cutting tool inserts.}, journal={JOURNAL OF MANUFACTURING PROCESSES}, author={Zhang, Jianlei and Starly, Binil and Cai, Yi and Cohen, Paul H. and Lee, Yuan-Shin}, year={2017}, month={Aug}, pages={457–463} }
 @inproceedings{qin_cai_dong_lee_2016, title={Direct printing of capacitive touch sensors on flexible substrates by additive e-jet printing with silver nanoinks}, volume={139}, DOI={10.1115/msec2016-8740}, abstractNote={In this paper, techniques of direct printing of capacitive touch sensors on flexible substrates are presented. Capacitive touch sensors were fabricated by using electrohydrodynamic inkjet (E-jet) printing onto flexible substrates. Touch pad sensors can be achieved with optimized design of silver nanoink tracks. An analytical model was developed to predict touch pad capacitance, and experiments were conducted to study the effects of sensor design (e.g. number of electrodes, electrode length, and electrode distance) on the capacitance of printed coplanar capacitance touch sensors. Details of the fabrication techniques were developed to enable rapid prototype flexible sensors with simple structure and good sensitivity. The presented techniques can be used for the on-demand fabrication of different conductive patterns for flexible electronics with high-resolution and good transparency.}, number={3}, booktitle={Proceedings of the ASME 11th International Manufacturing Science and Engineering Conference, 2016, vol 1}, author={Qin, H. T. and Cai, Y. and Dong, Jingyan and Lee, Yuan-Shin}, year={2016} }
 @inproceedings{cai_moore_lee_2016, title={Intricate geometric design and manufacturing on vibration-assisted needles for medical applications}, DOI={10.1115/msec2016-8743}, abstractNote={This paper presents a unique design of solid surgical needle featured by its 4-plane bevel tip and shaft slots with the aim to further explore the potential of vibratory needle insertion for medical applications. The design philosophy of the needle was introduced. To overcome the challenging issues faced in fabricating the designed needles, a non-traditional manufacturing process using electric discharging machining (EDM) for the tip and slots is presented. Two important parameters for needle cutting edges, the inclination angle and the included angle, were derived from the two fabrication variables of the bevel angle and the interval angle. Needle prototypes of the proposed design were fabricated with different geometries, and they are used to conduct several different experiments. In the first experiment, the needles were inserted into tissue phantom, and the friction slope was chosen as the performance criterion. In the second experiment, the testing medium was skin-mimicking polyurethane sheet, and the puncture force and depth were used to evaluate the performance. In both experiments, different vibration conditions of frequency-amplitude combinations (250Hz-5μm, 250Hz-50μm and 1500Hz-5μm) were applied in terms of frequency and amplitude. The preliminary results showed both weakness and potentials of the proposed design, and indicated the necessity for more experiments. Experiments and results to validate the presented method are also presented. The design and manufacturing techniques presented in this paper can be used for the design and development of surgical needles and cutters for engineering and medical applications.}, booktitle={Proceedings of the ASME 11th International Manufacturing Science and Engineering Conference, 2016, vol 2}, author={Cai, Y. and Moore, J. and Lee, Yuan-Shin}, year={2016} }