Browsing by Author "Cheng, Chung-Wei"

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Application of Ultrafast Laser Nanostructuring to Selective Laser Melting Parts
(2015-12)
Cheng, Chung-Wei
;
Chien, Chih-Wei
;
Lin, De-Yau
;
Horng, Ji-Bin
;
機械工程學系
A method is proposed for the fabrication of 3D metal (Ti6AL4V) parts that have microstructures covered with controllable nanostructures using selective laser melting (SLM) followed by laser-induced periodic surface structures (LIPSS). The metallic parts with microstructures was first fabricated by the SLM process, then a ultrafast laser machining platform was used to locally nanostructuring of the metal parts by LIPSS process. The experimental results show that periodic-like nanostructures with two different periods, i.e. 800-900 nm on the top surface and 450-600 nm on the bottom surface of the SLM-produced microstructures, were obtained simultaneously by a picosecond laser at wavelength 1064 mu with the same laser irradiation parameters. The liquid test demonstrates that the SLM+LIPSS process provides a structuring method to generate hydrophobic-enhanced metal parts. The process can provide a variety of 3D hierarchical micro/nanostructuring on metal material for biomedical application (e.g. customized implants) which is more than a conventional SLM process can provide.
Application of Ultrafast Laser Nanostructuring to Selective Laser Melting Parts
(2015-12-01)
Cheng, Chung-Wei
;
Chien, Chih-Wei
;
Lin, De-Yau
;
Horng, Ji-Bin
;
機械工程學系
A method is proposed for the fabrication of 3D metal (Ti6AL4V) parts that have microstructures covered with controllable nanostructures using selective laser melting (SLM) followed by laser-induced periodic surface structures (LIPSS). The metallic parts with microstructures was first fabricated by the SLM process, then a ultrafast laser machining platform was used to locally nanostructuring of the metal parts by LIPSS process. The experimental results show that periodic-like nanostructures with two different periods, i.e. 800-900 nm on the top surface and 450-600 nm on the bottom surface of the SLM-produced microstructures, were obtained simultaneously by a picosecond laser at wavelength 1064 mu with the same laser irradiation parameters. The liquid test demonstrates that the SLM+LIPSS process provides a structuring method to generate hydrophobic-enhanced metal parts. The process can provide a variety of 3D hierarchical micro/nanostructuring on metal material for biomedical application (e.g. customized implants) which is more than a conventional SLM process can provide.
Characteristic Comparison of Transversally Laminated Anisotropic Synchronous Reluctance Motor Fabrication Based on 2D Lamination and 3D Printing
(2015-01-01)
Zhang, Zhi-Yong
;
Tsai, Mi-Ching
;
Huang, Po-Wei
;
Cheng, Chung-Wei
;
Huang, Jian-Mi
Synchronous reluctance motors (SynRM) have been widely used because of their excellent performance, such as high efficiency and accurate speed control. This paper focused on the efficiency and starting ability of SynRM. Based on the view of steel sheet material and motor fabrication, the iron loss influences on SynRM regarding different grades of silicon steel are compared, and the performance of a squirrel cage assisted SynRM is investigated. Moreover, a new fabrication involving additive manufacturing (namely 3D printing) and a new high conductivity magnetic powder for facilitating the new SynRM fabrication process are proposed.
Characteristic Comparison of Transversally Laminated Anisotropic Synchronous Reluctance Motor Fabrication Based on 2D Lamination and 3D Printing
(2015)
Zhang, Zhi-Yong
;
Tsai, Mi-Ching
;
Huang, Po-Wei
;
Cheng, Chung-Wei
;
Huang, Jian-Mi
Synchronous reluctance motors (SynRM) have been widely used because of their excellent performance, such as high efficiency and accurate speed control. This paper focused on the efficiency and starting ability of SynRM. Based on the view of steel sheet material and motor fabrication, the iron loss influences on SynRM regarding different grades of silicon steel are compared, and the performance of a squirrel cage assisted SynRM is investigated. Moreover, a new fabrication involving additive manufacturing (namely 3D printing) and a new high conductivity magnetic powder for facilitating the new SynRM fabrication process are proposed.
Direct joining of 3D-printed thermoplastic parts to SLM-fabricated metal cellular structures by ultrasonic welding
(2018-10-01)
Tang, Sheng-Hung
;
Cheng, Chung-Wei
;
Yeh, Ren-Yu
;
Hsu, Ray-Quan
;
機械工程學系
The joining capability of metal cellular structures fabricated using the additive manufacturing (selective laser melting (SLM)) method is investigated herein. The metal cellular structures are composed of sub-millimeter holes and internal pores. The direct joining of 3D-printed ABS-M30i thermoplastic parts to metal cellular structures by ultrasonic welding is demonstrated. The SLM-fabricated structures comprised of partially melted powders provide micro-scale roughness, which enhances the micro-mechanical interlocking between joining parts. A shear strength 17.7MPa and normal tensile strength of 15.2MPa were obtained, up to 55 and 48% of ABS-M30i ultimate tensile strength, respectively. Moreover, normal tensile plastic strength up to 86% of the shear strength was obtained.
Fabrication of Porous Ti Structures with Nanostructures from Ti Powders by Femtosecond Laser Pulses
(2015-12-01)
Cheng, Chung-Wei
;
Huang, Chien-Jung
;
Cheng, Hui-Ta
;
Kuo, Ching-Nan
;
機械工程學系
The fabrication of titanium (Ti) porous structures covered with periodic nanostructures from micro Ti powders by femtosecond laser-induced sintering and simultaneous laser-induced periodic surface structures (LIPSS) are demonstrated. Different types of structures are obtained only by controlling the laser power of a femtosecond laser at wavelength 800 nm: sintered structures and sintered/melted structures with periodic nanostructures of period 550 similar to 650 nm.
Femtosecond laser melting of silver nanoparticles: comparison of model simulations and experimental results
(2018-05-01)
Cheng, Chung-Wei
;
Chang, Chin-Lun
;
Chen, Jinn-Kuen
;
Wang, Ben
;
機械工程學系
Ultrafast laser-induced melting of silver nanoparticles (NPs) using a femtosecond laser pulse is investigated both theoretically and experimentally. The sintered Ag structure fabricated from printed Ag NP ink using femtosecond laser (1064 nm, 300 fs) irradiation is experimentally studied. A two-temperature model with dynamic optical properties and particle size effects on the melting temperature of Ag NPs is considered. The rapid phase change model is incorporated to simulate the Ag NPs' ultrafast laser-induced melting process, and a multi-shot melting threshold fluence predicted from the simulated single-shot melting threshold is developed.
Femtosecond laser-induced periodic surface structures of copper: Experimental and modeling comparison
(2019-03-01)
Chang, Chin-Lun
;
Cheng, Chung-Wei
;
Chen, Jinn-Kuen
;
機械工程學系
;
Department of Mechanical Engineering
This study compared the experimental and numerical results of femtosecond laser-induced periodic surface structures (LIPSS) produced on copper surface. The experiments were carried out using a fiber laser of duration 300 fs, wavelength 515 nm, and a repetition rate 100 kHz. The periods of LIPSS were obtained by 2D fast Fourier transform analysis of the SEM images, and the depths were measured with an Atomic force microscope. Numerical analysis was performed using a two-dimensional two-temperature model (TTM) along with a modified Drude-critical points model, periodic energy distribution, and the phase change and explosion models for material ablation. The simulation results are in fairly good agreement with the experimental measurements.
High precision patterning of ITO using femtosecond laser annealing process
(2014-09-30)
Cheng, Chung-Wei
;
Lin, Cen-Ying
;
交大名義發表
;
機械工程學系
;
National Chiao Tung University
High precision patterning of crystalline indium tin oxide (c-ITO) patterns on amorphous ITO (a-ITO) thin films by femtosecond laser-induced crystallization with a Gaussian beam profile followed by chemical etching is demonstrated. In the proposed approach, the a-ITO thin film is selectively transformed into a c-ITO structure via a low heat affect zone and the well-defined thresholds (ablation and crystallization) supplied by the femtosecond laser pulse. The experimental results show that by careful control of the laser fluence above the crystallization threshold, c-ITO patterns with controllable line widths and ridge-free characteristics can be accomplished. By careful control of the laser fluence above the ablation threshold, fast fabrication of the two parallel sub-micro c-ITO line patterns using a single femtosecond laser beam and single scanning path can be achieved. Along-length sub-micro c-ITO line pattern is fabricated, and the feasibility of fabricating c-ITO patterns is confirmed, which are expected to be used in micro-electronics devices. (C) 2014 Elsevier B.V. All rights reserved.
Micromachining of stainless steel with controllable ablation depth using femtosecond laser pulses
(2016-08)
Cheng, Chung-Wei
;
Tsai, Xian-Zhe
;
Chen, Jenq-Shyong
;
機械工程學系
;
Department of Mechanical Engineering
This study proposes an approach for determining the lateral displacement distance between adjacent scanning paths for femtosecond laser ablation of a uniform crater profile on stainless steel with a controllable ablation depth. The first step performs the ablation experiment and measures the ablation depth. The second step calculates the laser intensity accumulation factor according to different lateral displacement distances. The required lateral displacement distance needed to achieve the design ablation depth can be obtained based on the experimental data.
NURBS Path Tracking Control of a Scanning Mirror System Based on EtherCAT Fieldbus
(2018-01-01)
Huang, Ruei-Yu
;
Cheng, Chung-Wei
;
Lee, An-Chen
;
機械工程學系
;
Department of Mechanical Engineering
In this paper, an EtherCAT scanning mirror system with function of NURBS path tracking control was investigated. By using EtherCAT protocol to connect master computer with a scanning mirror system, we did a first attempt to implement position control by the master computer, so that one can apply an advanced control algorithm to the system instead of applying a distributed control algorithm on the proprietary driver of the slave device. The technical issue of this configuration like commutation delay caused by the three-buffer-mode is addressed. A two-staged H-infinity with feed-forward controller is designed for the position control loop. Moreover, considering the widely used of non-uniform rational B-spline (NURBS) in the field of CAD/CAM, we added the function of NURBS path planning in the controller so that the system can deal with complex NURBS curves. The experiment results showed that the proposed method can reduce tracking error and have better performance when comparing with traditional distributed control strategy.
Single Track of Selective Laser Melting Process: Modeling and Experimental Comparison
(2019-09-01)
Cheng, Chung-Wei
;
Liou, Yao-Wen
;
Lee, An-Chen
;
Tsai, Mi-Ching
;
機械工程學系
This study uses finite element software to simulate the single melted track of powder (Maraging Steel) on a substrate (S45C). The simulation model considers the absorption penetrating depth of laser power on the powder bed and the penetrating energy irradiating the substrate. A volumetric heat source is applied to the powder bed model, and a surface heat source is applied to the substrate model to obtain the simulated temperature field distribution. The interface melt width between the powder bed, substrate surface, and the substrate melt depth are estimated according to the temperature field distribution. In the experiments, a self-developed SLM experimental system is used, and the laser power and scanning speed are adjusted to observe the effect of a single continuous track on the S45C substrate, which is compared with a theoretical simulation.
Sound absorption of metallic sound absorbers fabricated via the selective laser melting process
(2017-01)
Cheng, Li-Wei
;
Cheng, Chung-Wei
;
Chung, Kuo-Chun
;
Kam, Tai-Yan
;
機械工程學系
The sound absorption capability of metallic sound absorbers fabricated using the additive manufacturing (selective laser melting) method is investigated via both the experimental and theoretical approaches. The metallic sound absorption structures composed of periodic cubic cells were made of laser-melted Ti6Al4 V powder. The acoustic impedance equations with different frequency-independent and frequency-dependent end corrections factors are employed to calculate the theoretical sound absorption coefficients of the metallic sound absorption structures. The calculated sound absorption coefficients are in close agreement with the experimental results for the frequencies ranging from 2 to 13 kHz.
Synchronized multi-spot scanning strategies for the laser powder bed fusion process
(2019-05-01)
Tsai, Chun-Yu
;
Cheng, Chung-Wei
;
Lee, An-Chen
;
Tsai, Mi-Ching
;
機械工程學系
The laser powder bed fusion (LPBF) process can produce parts with complex internal geometries that cannot be easily manufactured using a material removal process. However, owing to the different heat transfer efficiencies of a laser melting process, the optimal process parameters are limited to a small range. This study used galvanometric scanner technology and a diffractive optical element (DOE) to build an experimental multi-spot LPBF system. Adjustable characteristics were the angle and the lateral distance between spots. An adjustable multispot method was used to modulate the temperature field on the powder bed and enhance the processing quality and throughput. The results from the synchronized three-spot method using different scanning strategies improved the layer surface roughness Ra by 3.2 mu m. Moreover, the scanning time was decreased by 38.1% of the single-spot method.
Ultrafast laser ablation of copper by GHz bursts
(2020-07-31)
Cheng, Chung-Wei
;
Chen, Jinn-Kuen
;
機械工程學系
;
Department of Mechanical Engineering
The ablation of copper, using a 10 GHz burst ultrafast laser with a wavelength of 1030 nm, a pulse duration of 1 ps, a variable total laser fluence, and a number of sub-pulses per burst, is investigated theoretically. A two-temperature model with an extended Lorentz-Drude model for dynamic optical properties is used to simulate the melting and ablation process. Due to the heat accumulation from the preceding pulses, multipulse laser ablation could be advantageous over a single pulse. Moreover, the ablation performance can be maximized by properly selecting the pulse number, separation time, and energy in a laser burst. The numerical result shows that the present prediction is in fairly agreement with existing experimental result. Under the same total laser fluence of 32 J/cm(2), a 10 GHz burst laser with an optimized 128 sub-pulse can significantly enhance the ablation depth, 4.2 times that a single pulse does. It is found that the optimized ablation depth is a linear function of the total fluence of ultrafast laser bursts.