Yih-Lin Cheng and Tzu-Wei Tseng
Material-jetting (MJ) three-dimensional (3D) printing processes are competitive due to their printing resolution and printing speed. Driving waveform design of piezoelectric…
Abstract
Purpose
Material-jetting (MJ) three-dimensional (3D) printing processes are competitive due to their printing resolution and printing speed. Driving waveform design of piezoelectric printhead in MJ would affect droplet formation and performance, but there are very limited studies on it besides patents and know-hows by commercial manufacturers. Therefore, in this research, the waveform design process to efficiently attain suitable parameters for a multi-nozzle piezoelectric printhead was studied. Therefore, this research aims to study the waveform design process to efficiently attain suitable parameters for a multi-nozzle piezoelectric printhead.
Design/methodology/approach
Ricoh’s Gen4L printhead was adopted. A high-speed camera captured pictures of jetted droplets and droplet velocity was calculated. The waveforms included single-, double- and triple-pulse trapezoidal patterns. The effects of parameters were investigated and the suitable ones were determined based on the avoidance of satellite drops and preference of higher droplet velocity.
Findings
In a single-pulse waveform, an increase of fill time (Tf) decreased the droplet velocity. The maximum velocity happened at the same pulse width, the sum of fill time and hold time (Tf + Th). In double- and triple-pulse, a voltage difference (Vd) above zero in the holding stage was adopted except the last pulse to avoid satellite drops. Suitable parameters for the selected resin were obtained and the time-saving design process was established.
Research limitations/implications
Based on the effects of parameters and observed data trends, suggested procedures to determine suitable parameters were proposed with fewer experiments.
Practical implications
This study has verified the feasibility of suggested design procedures on another resin. The required number of trials was reduced significantly.
Originality/value
This research investigated the process of driving waveform design for the multi-nozzle piezoelectric printhead. The suggested procedures of finding suitable waveform parameters can reduce experimental trials and will be applicable to other MJ 3D printers when new materials are introduced.
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Keywords
Yih-Lin Cheng, Chih-Hsuan Chang and Chunliang Kuo
The material-jetting-type (MJ) 3-D printing technology has advantages in resolution and color printing. During the printing process, a leveling technique is needed to precisely…
Abstract
Purpose
The material-jetting-type (MJ) 3-D printing technology has advantages in resolution and color printing. During the printing process, a leveling technique is needed to precisely control the thickness and flatness of each layer. Roller-type leveling mechanism has been adopted in commercial MJ 3-D printers, but it is lack of research on roller leveling process parameters and establishing experimental procedures. Therefore, in this study, a roller-type leveling mechanism for a MJ color 3 D printer was developed, and experimental approaches were utilized to determine process parameters.
Design/methodology/approach
The roller-type leveling mechanism was chosen to provide functions of flattening and removal of excess material. The parameters studied were roller speed and rotational direction. Surface roughness, Ra, of printed single-layered specimens was measured at 15 locations for plane roughness and along five lines for line roughness to evaluate the leveling results. Adopting suitable parameters, color samples with and without leveling were printed for comparison and verification.
Findings
According to plane roughness results, forward rotation achieved better leveling. Plane roughness was the major criteria to determine roller speed with the assistance of standard deviation of line roughness. The best parameters of the self-developed MJ color 3-D printer were found to be rolling forward at 1,100 rpm. In addition, printed color samples showed great improvement in surface roughness with leveling and no obvious color mixing after leveling.
Research limitations/implications
Leveling is important to achieve desired layer thickness, smooth surface and good color quality in color 3-D printing. For MJ 3-D printing, only patents were revealed regarding roller design, but paper publications have not been presented. This research practically proposed to use experimental approach to understand the effects of roller operating parameters and to find the suitable ones based on surface roughness results.
Practical implications
This research established the experimental procedures and also suggested guidelines of experimentally obtaining suitable roller leveling process parameters. Developers can refer to this study results to design and adjust leveling mechanism in a new MJ 3-D printer.
Originality/value
The experimental approach can be applied to similar MJ 3-D printing systems if different materials are introduced or the platform speed is changed. The observed trends suggested several guidelines to plan limited experiments only to obtain suitable roller process parameters.
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Yih‐Lin Cheng and Jin‐Chiou Chu
A continuous positive airway pressure (CPAP) device is one of the main treatments for obstructive sleep apnea (OSA) patients. Most patients treated by this method complain about…
Abstract
Purpose
A continuous positive airway pressure (CPAP) device is one of the main treatments for obstructive sleep apnea (OSA) patients. Most patients treated by this method complain about the comfortableness of the mask, but the commercial mask cushions are only available in fixed sizes. Therefore, the purpose of this paper is to apply the rapid tooling (RT) technique to manufacture customized nasal mask cushions, to increase the performance and with price competitiveness.
Design/methodology/approach
The patient's face was first duplicated twice by Hygrogum and plaster. The face model, on which the cushion CAD design was based, was digitized by the reverse‐engineering technology. The RT of the cushion was then designed and manufactured by two rapid prototyping techniques – Objet's PolyJet and shape deposition manufacturing (SDM). Finally, silicone was cast into the RT to obtain customized cushions. The customized cushion was compared with two other commercial cushions through fit testing and cost estimation.
Findings
The proposed approach can successfully manufacture customized cushions within a day. The SDM process has advantages in this application over Objet's system. The fit testing showed that the fit factor of the customized cushion was better and less loading was required, which should lead to great improvement in the patient's comfort. Moreover, the price‐to‐performance ratio of the customized cushion can be lower than the commercial ones if more than three cushions were made by a single rapid tool.
Originality/value
This paper has proposed a new application of RT on customized nasal mask cushions for CPAP devices. The customized cushion has lower price‐to‐performance ratio and the cost remains competitive.
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Yih‐Lin Cheng and Meng‐Long Lee
In order to manufacture scaffolds for tissue engineering, a dynamic mask rapid prototyping system to cure UV‐curable biodegradable material was developed. The aim of this paper is…
Abstract
Purpose
In order to manufacture scaffolds for tissue engineering, a dynamic mask rapid prototyping system to cure UV‐curable biodegradable material was developed. The aim of this paper is to document this system.
Design/methodology/approach
A digital micro‐mirror device (DMD) was used as the dynamic mask generator, with each layer's mask pattern dictated by our self‐developed software. To build the scaffolds, UV light reflected by the DMD was then focused onto the biodegradable material to cure it. The biodegradable material used in this experiment was a mixture of 85/15 PLGA, PEG‐HEMA, and a photo‐initiator.
Findings
The dynamic mask rapid prototyping system was successfully built and scaffolds made of UV‐curable biodegradable material were fabricated to verify the system capacity. The working exposure time for each layer was 45 s except for the first layer, which was 60 s. Scaffolds with 0°/90° and 60°/120° strips in alternating layers were fabricated and the pore size error in X and Y axes of 0°/90° design was found to be 7.33 and 2.13 percent, respectively. Preliminary cell culture tests indicate the fabricated scaffold is not harmful to MG‐63 cell growth.
Research limitations/implications
Different scaffold designs and more UV‐curable biodegradable materials may be further implemented and tested through this system.
Originality/value
This research developed a novel system for tissue engineering scaffold fabrication which can process UV‐curable biodegradable material.
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M.A. Paczkowski and S.T. Reddy
Over the past few years there has been increasing utilisation of higher density surface mounting on printed wiring boards. As components and pads decrease in size, the topography…
Abstract
Over the past few years there has been increasing utilisation of higher density surface mounting on printed wiring boards. As components and pads decrease in size, the topography of the solder mask relative to the conductors becomes an important solderability issue. There exists convincing evidence that thinner, more conformal solder mask geometries improve soldering yields of both stencilled and wave soldered surface mount components. In order to provide the solder mask coverage required for improved assembly performance, the authors critically compared several commercially available solder mask coating technologies. The coating methods were appraised according to both assembly and printed wiring board manufacturing criteria. Within this programme, seven liquid photoimageable solder masks were also evaluated. The materials were rated according to their final cured properties (electrical, mechanical, chemical performance), their manufacturability in the printed wiring board manufacturing process (maximum throughput, major defects, etc.) and their performance in assembly operations (soldering yields, propensity to ‘solder ball’ formation, white residues, scratches, etc.). The information obtained was used to choose a solder mask strategy which would not only improve assembly efficiency but also increase PWB manufacturing yields and flexibility.
Che-Chih Tsao, Ho-Hsin Chang, Meng-Hao Liu, Ho-Chia Chen, Yun-Tang Hsu, Pei-Ying Lin, Yih-Lin Chou, Ying-Chieh Chao, Yun-Hui Shen, Cheng-Yi Huang, Kai-Chiang Chan and Yi-Hung Chen
The purpose of this paper is to propose and demonstrate a new additive manufacturing approach that breaks the layer-based point scanning limitations to increase fabrication speed…
Abstract
Purpose
The purpose of this paper is to propose and demonstrate a new additive manufacturing approach that breaks the layer-based point scanning limitations to increase fabrication speed, obtain better surface finish, achieve material flexibility and reduce equipment costs.
Design/methodology/approach
The freeform additive manufacturing approach conceptually views a 3D article as an assembly of freeform elements distributed spatially following a flexible 3D assembly structure, which conforms to the surface of the article and physically builds the article by sequentially forming the freeform elements by a vari-directional vari-dimensional capable material deposition mechanism. Vari-directional building along tangential directions of part surface gives surface smoothness. Vari-dimensional deposition maximizes material output to increase build rate wherever allowed and minimizes deposition sizes for resolution whenever needed.
Findings
Process steps based on geometric and data processing considerations were described. Dispensing and forming of basic vari-directional and vari-dimensional freeform elements and basic operations of joining them were developed using thermoplastics. Forming of 3D articles at build rates of 2-5 times the fused deposition modeling (FDM) rate was demonstrated and improvement over ten times was shown to be feasible. FDM compatible operations using 0.7 mm wire depositions from a variable exit-dispensing unit were demonstrated. Preliminary tests of a surface finishing process showed a result of 0.8-1.9 um Ra. Initial results of dispensing wax, tin alloy and steel were also shown.
Originality/value
This is the first time that both vari-directional and vari-dimensional material depositions are combined in a new freeform building method, which has potential impact on the FDM and other additive manufacturing methods.
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Wann‐Yih Wu, Chinho Lin and Li‐Yeuh Lee
Maintains that women in the USA have much more leadership chances, less harassment and more respect from subordinates than Japanese women (who live in a male‐dominated world), who…
Abstract
Maintains that women in the USA have much more leadership chances, less harassment and more respect from subordinates than Japanese women (who live in a male‐dominated world), who are reluctant to make decisions or take risks without consultations. Observes that women from Taiwan seem to have a much more transactional leadership style – taking risks and making rapid decisions. Discusses, in great detail, using extensive research via a multiple‐item scale to measure each item and lays out the results using figures and tables with great detail. Concludes with full results of the study and what they mean.