• Korean Chemical Engineering Research
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• v.60 no.2
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• pp.308-312
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• 2022

3D printing technology, which creates a physical object by various material deposition, has been widely used in recent years in the manufacturing field because of its advantages. Among the various printing technologies, droplet-based 3D printing technology (e.g., Polyjet^®) enables a high-resolution printing using photocurable materials such as hydrogels. Depending on the degree of light exposure, ejected photocurable droplets may have different properties (e.g., viscosity) until they collide with the substrate and it leads to the different spreading behaviors of the droplets (i.e., impact, spreading, and recoiling) during deposition on the substrate. In this study, experimental observation and analysis of the changes in hydrogel droplet viscosity and spreading behavior according to the light exposure were carried out based on high-speed image processing.

• Journal of Sensor Science and Technology
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• v.30 no.6
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• pp.388-394
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• 2021

The conventional microelectromechanical system (MEMS) process has been used to fabricate sensors with high costs and high-volume productions. Emerging 3D printing can utilize various materials and quickly fabricate a product using low-cost equipment rather than traditional manufacturing processes. 3D printing also can produce the sensor using various materials and design its sensing structure with freely optimized shapes. Hence, 3D printing is expected to be a new technology that can produce sensors on-site and respond to on-demand demand by combining it with open platform technology. Therefore, this paper reviews three standard 3D printing technologies, such as Fused Deposition Modeling (FDM), Direct Ink Writing (DIW), and Digital Light Processing (DLP), which can apply to the sensor fabrication process. The review focuses on strain/load sensors having both sensing material features and structural features as well. NCPC (Nano Carbon Piezoresistive Composite) is also introduced as a promising 3D material due to its favorable sensing characteristics.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.37 no.4
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• pp.382-393
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• 2024

The Microplotter system with a fluid dispensing method, sprays fluid based on ultrasonic pumping through piezoelectric devices. This technique can possible for various materials with a wide range of viscosities to be printed in microscale. In this paper, we introduces dispenser printing technology as well as aim to understand and apply various processes using the equipment. In addition, we will explain how to optimize the equipment by adjusting parameters such as spray intensity, tip height during printing, and patterning speed. By utilizing Microplotter's advantage of being compatible with a wide range of fluids, including metal nanoparticles, carbon nanotubes, DNA, and proteins, it is expected to be used in various fields such as printed electronics, biotechnology, and chemical engineering.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.11
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• pp.1018-1024
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• 2010

The printer noise consists of the noise of the various components and parts such as motor, fan and solenoid. And the human's printing sound recognition shows various aspects when the printer starts to print papers because the components operate at the same time. Especially, printers are usually installed in the quiet office room. Therefore the printing noise is related to its competitiveness in the market. The importance of the printer sound qualities is increasing and it is necessary to develop the sound quality evaluation system, so it is a key point to identify the noise source of the printer and develop the sound quality index to each component. By using this evaluation system, it is possible to evaluate the sound quality of a prototype printer compared to the already existing one. In this paper, the printer sound quality evaluation system was developed by the following steps. Firstly, the signal processing method was applied to the recorded printing sound to identity and split the noise of components. Secondly, the MLR(multiple linear regression) method and the psychoacoustics were used to develop the sound quality index. Finally, the improvement of the printer sound quality is possible by using the result of the MLR and the path analysis. The output of this research will be applied to the development of a new printer.

• Journal of Digital Convergence
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• v.16 no.10
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• pp.235-241
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• 2018

The printout management system should analyze the pattern of existence of personal information (resident number, card number) in the output log and users should be provided with functions such as warning message pop-up, forced printing termination, mailing to administrator, independently logs management. Authentication management can also be performed only by registered users by installing an agent on a user PC, and it should have a restriction function to permit or deny work according to user information. In addition, when printing/copying/scanning using this equipment, it is possible to use document printing and multifunction copier after ID card authentication and ID/PW should be input to device when ID card is not used. In this study, we developed these interfaces with WOWSOFT co., Ltd, a security company that has better technology than the existing printout security methods, to construct the printout management system. Also we designed the interface of basic functions necessary for printout management and contributed to the establishment of printout management system.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.19 no.2
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• pp.113-126
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• 2009

In the recent years, health effect of dimethylformamide(DMF) has been one of critical industrial hygiene issues. There might be many factors to increase the exposure level of DMF. Among those factors, industrial ventilation would be one of the main factors. In this study, industrial ventilation systems of printing processes in synthetic leather factories were thoroughly surveyed and the improved ventilation systems were proposed. 7 synthetic leather factories were selected for this study. After the ventilation systems were visually inspected, each component of the system was tested by using the appropriate instruments. Hood face velocities, fan exhaust flow rates, fan static pressures, fan rotation rates, etc were measured. In addition, flow visualization techniques were used to observe flow patten around hoods and inside the factory buildings. After gathering all qualitative and quantitative information, the test results were analysed to see if any improvement might be necessary. For the system to be improved, the re-design plans were made by using computational fluid dynamics softwares. The softwares used in this study were AIRPAK and STAR-CD. The effectiveness of the several improvement options were tested, then the best cost effective option was selected. Finally, the standard ventilation systems were proposed to minimize the exposure levels of DMF.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.11 no.3
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• pp.179-189
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• 2001

This study was performed to identify the current status of work environment management and to provide appropriate recommendations for small scale industry with less than 5 workers from September, 2000 to October, 2000 in Seoul city and Gyoung-gi province. The 211 companies were surveyed by checklist included the elements of management of work environment, hazardous chemicals, MSDS, personal protective equipment, and ventilation system. The proportion of metal products manufacturing and printing industries are 25.6 % and 22.3%, respectively. The daily working hours in printing industry is longer than others. The industries that produce potentially hazardous agents, such as noise, dust, metal, organic solvents, radiation and chemical material are pulp, plating, machinery, and printing, respectively. In above industries, only 2.8 % of those recognised and had MSDS. The proportion of companies providing fire extinguishers, safety showers are found to be 13.3 %, 7.1 %, respectively. Only 24.2 % of companies provided personal protective equipment to the workers. The ventilation system was operated in most of companies. But local exhaust ventilation system is provided to 22.3 % of those, also had not been annually inspected. This study showed that the current status of occupational safety and health was not appropriate for workers in small scale industries. It is suggested that annual physical examination have to be performed, MSDS usage must become widespread, and employer and emplyees in small scale industry should be educated for the treatment and storage of hazardous chemicals to improve the occupational safety and health of the working environment. also, regulatory standard has to be applied to local exhaust ventilation system in small scale industry to improve the working condition.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.2164-2169
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• 2005

SFFS(Solid Freeform Fabrication System) can quickly makes models and prototype parts from 3D computer-aided design (CAD) data. Three dimensional printing(3DP) is a kind of the solid freeform fabrication. The 3DP process slices the modeling data into the 50-200um along to z axis. And we pile the powder and make the manufactures. A manufacture is made by the SFFS has the precision of the 50um. Therefore the x-y table of SFFS to move a printhead must be the system that has a high speed and accuracy. So we proposed the SMCSPO algorithm for SFFS. The major contribution is the design of a robust observer for estimating the state and the perturbation of the timing belt system, which is combined with a robust controller. The control performance of the proposed algorithm is compared with PD control by the simulation and the experiment. The control algorithm of the SFFS is presented in the office environment. The system between control system and printhead for the SFFS is also integrated

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.24 no.6
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• pp.710-717
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• 2015

Projection stereolithography is an additive manufacturing method that uses beam projection to cure the photo-reactive resin used. The light source of a cross-section layer-form illuminates photo-curable resin for building a three-dimensional (3D) model. This method has high accuracy and a fast molding speed because the processing unit is a face instead of a dot. This study describes a Scalable Projection Stereolithography 3D Printing System for improving the accuracy of the stereolithography. In a conventional projection 3D printer, when printing a small sized model, many pixels are not used in the projection or curing. The proposed system solves this problem through an optical adjustment, and keeps using the original image as possible as filling the whole projection area. The experimental verification shows that the proposed system can maintain the highest level of precision regardless of the output size.

• 한국정보디스플레이학회:학술대회논문집
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• 2004.08a
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• pp.544-547
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• 2004

Glass frits for dielectric layers are mostly used for screen printing process. Several additives have already been known to be well matched with lead-oxide glasses system. The use of lead oxide, however, creates environmental problems, so many recent studies on lead-free glasses compositions have been carried out. A study of the suitability between additives and lead-free glass system is needed. In this study, we have used a screen-printing method to make thick films of lead-oxide glass and lead-free glass using different additives, and analyzed and compared the transmittance of the thick films.