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Review Article

J. Manuf. Sci. Eng. 2019;141(5):050801-050801-16. doi:10.1115/1.4042607.

Although extrusion-based 3D printing processes have seen many successful applications at the macroscale, it has proven to be challenging for consistent, repeatable, and cost-effective printing at the microscale due to its dynamic complexities. To fully tap into the promise of microextrusion printing (ยตEP) of fabricating fine resolution features, it is critical to establish an understanding of the fundamentals of ink flow, interface energy, drying, and the process-property relationship of the printing process. To date, a comprehensive and coherent organization of this knowledge from relevant literature in different fields is still lacking. In this paper, we present a framework of the underlying principles of the microextrusion process, offering an overall roadmap to guide successful printing based on both results in the literature and our own experimental tests. The impacts of various process parameters on the resolution of printed features are identified. Experiments are carried out to validate the developed framework. Key challenges and future directions of microextrusion 3D printing are also highlighted.

Commentary by Dr. Valentin Fuster

Research Papers

J. Manuf. Sci. Eng. 2019;141(5):051001-051001-12. doi:10.1115/1.4042608.

Conventional machining of Ti6Al4V/TiC composites is a very difficult process, which exhibits a peculiar cutting force pattern where the thrust forces are higher than the tangential forces. This behavior results in rapid tool wear and consequently very short tool life. This study is concerned with describing the reasons for the attendant behavior using experimentally validated 3D finite element simulations and alleviating this behavior via laser assisted machining (LAM). Simulations were conducted using an equivalent homogeneous model (EHM) and a multiscale heterogeneous model (MHM) of the Ti6Al4V/TiC composite. Results showed a good agreement between the tangential forces obtained from experiments, EHM, and MHM for conventional machining and LAM. However, only the MHM was able to successfully predict the unusual high thrust forces. The MHM simulation results showed that the tool/particle interaction along the tool nose region presented the highest resistance due to the high resistance against pushing the TiC particles by the tool into the machined surface. This resistance results from the efficient load transfer capability between the particles and the matrix below the machined surface. When using LAM, the stated resistance was decreased by the reduction in load transfer capability of the Ti6Al4V/TiC workpiece such that the thrust and tangential forces were reduced by 78% and 37%, respectively, according to the MHM simulation. The experimental results showed that the tool wear was improved by 68% by LAM. All the results demonstrated that the MHM successfully captured the underlying machining mechanism of the Ti6Al4V/TiC composites.

Commentary by Dr. Valentin Fuster

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