Browsing by Author "Danh-Tuyen Nguyen"

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Analyses of a new four-facet drill
(2014-10-01)
Lee, An-Chen
;
Danh-Tuyen Nguyen
;
Wu, Guan-Ting
;
機械工程學系
;
Department of Mechanical Engineering
In this paper, a new four-facet drill was presented and analyzed. For evaluating the performance of the new and conventional drills, the geometrical analyses of the rake faces and flank surfaces as well as the prediction of cutting forces and torques were conducted. The results showed that the normal rake and clearance angles along the cutting lips of the new drill are always positive and a positive constant, respectively. In contrast, those of the conventional one are negative at certain points on cutting lips close to the drill axis and variable, respectively. Therefore, the cutting forces and torques of the new drill in drilling can be reduced as compared with the conventional one. The prediction of cutting forces and torques in drilling the workpiece made of plain-carbon steel (AISI1045) showed that the reductions of the total thrust force and torque along cutting lips for the new drill over the conventional drill are up to 50.12 and 26.54 %, respectively, and hence, the tool life of the new drill is expected to be longer than the conventional one\'s.
Design of grinding wheel profile for new micro drill flute
(2018-06-01)
Danh-Tuyen Nguyen
;
Hai-Anh Nguyen
;
An-Chen Lee
;
機械工程學系
;
Department of Mechanical Engineering
Derived from our previous research, a new micro drill bit with higher accuracy and productivity was developed. Because the drill flute plays a significant role in its cutting performance, the design of grinding wheel profile for the new micro drill flute by an inverse problem method is examined in this research. First, the cross-section of the new micro drill flute is modeled by mathematical equations. Second, machine parameters and work-piece geometric parameters are set up. Third, the engagement equation between the grinding wheel and flute surfaces is developed. Fourth, that equation is solved to obtain the locus of contact points. Finally, the translation and rotation transformations of that locus are carried out to obtain the grinding wheel profile for the new micro drill flute. Numerical examples are demonstrated and validated by Vericut software.
Dynamic Analysis of a Micro Drilling System by the Modified Transfer Matrix Method
(2016-01-01)
Lee, An-Chen
;
Danh-Tuyen Nguyen
;
機械工程學系
;
Department of Mechanical Engineering
Normally, breakage is the main cause of failure of a micro drilling system, of which coupling effect of lateral and torsional displacements plays the most important role. This research developed a modified transfer matrix method to investigate the dynamics of a micro drilling system focusing on displacements induced by not only lateral, shear, torsional deformations, but also the coupling effect between lateral and torsional vibrations. The micro drilling system is modeled as pre-twisted rotating Timoshenko beam elements with a continuous-system concept. Each element includes components of linear bearings, axial drilling force, gyroscopic moments, and eccentricity. The overall transfer matrix of the system is developed to determine the state vector of the system including displacements and forces. Finally, a numerical example was presented, where the lateral and torsional displacements and critical speed of the micro drilling system at the micro drill's tip were presented.
Structure optimization of a micro drill bit with nonlinear constraints considering the effects of eccentricity, gyroscopic moments, lateral and torsional vibrations
(2017-01-01)
Danh-Tuyen Nguyen
;
Tien-Dat Hoang
;
Lee, An-Chen
;
機械工程學系
;
Department of Mechanical Engineering
A micro drill structure was optimized to give minimum lateral displacement at its drill tip, which plays an extremely important role on the quality of drilled holes. A drilling system includes a spindle, chuck and micro drill bit, which are modeled as rotating Timoshenko beam elements considering axial drilling force, torque, gyroscopic moments, eccentricity and bearing reaction force. Based on our previous work, the lateral vibration at the drill tip is evaluated. It is treated as an objective function in the optimization problem. Design variables are diameter and lengths of cylindrical and conical parts of the micro drill, along with nonlinear constraints on its mass and mass center location. Results showed that the lateral vibration was reduced by 15.83 % at a cutting speed of 70000 rpm as compared to that for a commercial UNION drill. Among the design variables, we found that the length of the conical part connecting to the drill shank plays the most important factor on the lateral vibration during cutting process.