• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.2
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• pp.82-90
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• 2019

In this paper, the effects of different 3D printing conditions including oil lubrication and annealing are observed for their effects on tensile testing. In 3D printing, a press-out extrude filament is rapidly heated and cooled to create internal stress in the printed part. The 3D printing internal stress can be removed using oil-coated filament and annealing. During the oven cooling at an annealing temperature of $106^{\circ}C$, the stress of the specimens with laminated angle $0^{\circ}$ tends to increase by 12.6%, and that of the oil-coated filament printing specimens is increased by 17%. At the annealing temperature of $106^{\circ}C$, the stress of the oil-coated filament printing specimens tends to increase by 35%. In this study, we have found that the oil lubrication and annealing remove the internal stresses and increase the strength of the printed specimens. The oil lubrication and annealing reform the crystalline structures to even out the areas of high and low stress, which creates fewer fragile areas. These results are very useful for the manufacture of 3D printing products with a suitable mechanical strength for applications.

• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.6
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• pp.113-118
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• 2020

The purpose of this study is to evaluate the shrinkage characteristics of the cement-based composite for 3D printing construction, and to evaluate the shrinkage before/after extrusion and after printing during the printing process. As a result of evaluating the compressive strength by curing age of OPC-mix and printing-mix, similar trends were shown until 7 days of age, but the maximum shrinkage of 252 ㎛/m was larger in the case of OPC-mix compared to printing-mix. During the printing process, the compressive strength of the cementitious composite material after extrusion was about 6.5 MPa lower than the material before extrusion until the 7th day of age, but the level of strength on the 28th day of age was similar. As for the shrinkage characteristics, the result of shrinkage after printing showed greater shrinkage in the range of 220-260 ㎛/m compared to the result of shrinkage before extrusion.

• Journal of Biomedical Engineering Research
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• v.43 no.2
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• pp.116-123
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• 2022

This study analyzes the Mechanical properties of a medical bone plate by 3D printing. With the recent development of 3D printing technology, it is being applied in various fields. In particular, in the medical field, the use of 3D printing technology, which was limited to the existing orthosis and surgical simulation, has recently been used to replacement bones lost due to orthopedic implants using metal 3D printing. The field of application is increasing, such as replacement. However, due to the manufacturing characteristics of 3D printing, micro pores are generated inside the metal printing output, and it is necessary to reduce the pores and the loss of mechanical properties through post-processing such as heat treatment. Accordingly, the purpose of this study is to analyze the change in mechanical performance characteristics of medical metal plates manufactured by metal 3D printing under various conditions and to find efficient metal printing results. The specimen to be used in the experiment is a metal plate for trauma fixation applied to the human phalanx, and it was manufactured using the 'DMP Flex 100(3D Systems, USA), a metal 3D printer of DMLS (Direct Metal Laser Sintering) method. It was manufactured using the PBF(Powder Bed Fusion) method using Ti6Al4V ELI powder material.

• Journal of the Korea Safety Management & Science
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• v.25 no.1
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• pp.7-14
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• 2023

We attempted to provide an overview of the laws and current state of the 3D printing industry in South Korea and around the world, using the annual industry surveys and the Wohler report. Additionally, we reviewed articles relating to the potential exposure to hazards associated with 3D printing using metal materials. In South Korea, there were 406 3D printing-related businesses, employing 2,365 workers, and the market size was estimated at 455.9 billion won in 2021. Globally, the average growth rate of the 3D printing industry market over the past 10 years was 27.4%, and the market size was estimated at $11.8 billion in 2019. The United States had the highest cumulative installation ratio of industrial 3D printers, followed by China, Japan, Germany, and South Korea. A total of 6,168 patents related to 3D printing were registered in the US between 2010 and 2019. Harmful factors during metal 3D printing was mainly evaluated in the powder bed fusion and direct energy deposition printing types, and there is a case of material extrusion type with metal additive filaments. The number, mass, size distribution, and chemical composition of particles were mainly evaluated. Particle concentration increases during the opening of the chamber or post-processing. However, operating the 3D printer in a ventilated chamber can reduce particle concentration to the background level. In order to have a safe and healthy environment for 3D printing, it is necessary to accumulate and apply knowledge through various studies.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.30 no.2
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• pp.153-162
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• 2020

Objectives: 3D printing technologies have become widely developed and are increasingly being used for a variety of purposes. Recently, the evaluation of 3D printing operations has been conducted through chamber test studies, and actual workplace studies have yet to be completed. Therefore, the objective of this study was to determine the emission of volatile organic compounds(VOCs), metals, and particles from printing operations at a workplace. This included monitoring conducted at a commercial 3D printing service workplace where the processes involved material extrusion, material jetting, binder jetting, vat photo polymerization, and powder bed fusion. Methods: Area samples were collected with using a Tenax TA tube for VOC emission and MCE filter for metals in the workplace. For particle monitoring, Mini Particle Samplers(MPS) were also placed in the printer, indoor work area, and outdoor area. The objective was to analyze and identify particles' size, morphology, and chemical composition using transmission electron microscopy with energy dispersive spectroscopy(TEM-EDS) in the workplace. Results: The monitoring revealed that the concentration of VOCs and metals generated during the 3D printing process was low. However, it also revealed that within the 3D printing area, the highest concentration of total volatile organic compounds(TVOC) was 4,164 ppb at the vat photopolymerization 3D printing workplace, and the lowest was 148 ppb at the material extrusion 3D printing workplace. For the metals monitoring, chromium, which, is carcinogenic for humans, was detected in the workplace. As a characteristic of the particles, nano-sized particles were also found during the monitoring, but most of them were agglomerated with large and small particles. Conclusions: Based on the monitoring conducted at the commercial 3D printing operation, the results revealed that the concentration of VOCs and metals in the workplace were within Korea's occupational exposure limits. However, due to the emission of nano-sized particles during 3D printing operations, it was recommended that the exposure to VOCs and metals in the workplace should be minimized out of concern for workers' health. It was also shown that the characteristics of particles emitted from 3D printing operations may spread widely within an indoor workplace.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.10
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• pp.6336-6343
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• 2014

The aim of this study was to consider new 3D printing techniques and how to use them in architecture, compare the 3D printing and current techniques, and analyze them economically. 3D printing technology is expected to result in considerable changes to the entire system, such as production and distribution using this new technology in the near future. In addition, architecture is expected to follow this trend. This study examined how to take advantage of 3D printing technology in construction to prepare for a new architectural trend of 3D printing technology in the future. This study examined the 3D printing technology that is used in buildings and the current state of 3D printing technology. In addition, the 3D printing technology and current technology was also compared, and analyzed economically. 3D printing technology is the step before the stage of practical use. On the other hand, the commercialization of 3D printing technology makes it possible to reduce the cost compared to the current method. Furthermore, as the technology is developed in the future, the cost is expected to be reduced further. Therefore, the use of 3D printing technology in architecture is expected increase continually.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.10
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• pp.34-38
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• 2016

This study aims to develop qualification criteria for training and establishing an expert pool of 3D printing operation experts and 3D printing development specialists in the emerging 3D printing industry. We investigate the domestic and international 3D printing industry, as well as 3D printing- related training institutions and quantity of test examinees. Utilizing competency analysis, this study examines the competencies and educational content of both 3D printing operation expert as well as 3D printing development specialists. In addition, a survey was conducted on the issue of institutionalization of qualification criteria for 3D printing operation expert and 3D printer development specialists. This study further proposes evaluation methods for qualification criteria for both 3D printing operation expert and 3D printer development specialists based on simulations of both written and performance tests. Based on the findings, this study proposes instructional program outlines as well as comprehensive guidelines for training and qualification processes for 3D printing operation expert and 3D printer development specialists.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.28 no.3
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• pp.183-192
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• 2022

With the growth of the packaging industry, demand on the packaging printing comes in various forms. Customers' orders are diversifying and the standards for quality are increasing. Offset printing is mainly used in the packaging printing since it is easy to print in large quantities. However, productivity of the offset printing decreases when printing various order. This is because it takes time to change colors for each printing unit. Therefore, scheduling that minimizes the color replacement time and shortens the overall makespan is required. By the existing manual method based on workers' experience or intuition, scheduling results may vary for workers and this uncertainty increase the production cost. In this study, we propose an automated scheduling method of parallel offset printing process for packaging printing. We decompose the original problem into assigning and sequencing orders, and ink arrangement for printing problems. Vehicle routing problem and assignment problem are applied to each part. Mixed integer programming is used to model the problem mathematically. But it needs a lot of computational time to solve as the size of the problem grows. So guided local search algorithm is used to solve the problem. Through actual data experiments, we reviewed our method's applicability and role in the field.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.14 no.6
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• pp.142-148
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• 2015

3D printing technology is a promising technique for fabricating complex 3D architectures based on the CAD/CAM system, and it has been extensively investigated to manufacture structures in the fields of mechanical engineering, space technology, automobiles, and biomedical and electrical applications. Recent advances in the 3D printing of soft structures have received attention for the application of the construction of flexible sensors of soft robotics or the recreation of tissue/organ-specific microenvironments. In this review paper, we would like to focus on delivering state-of-the-art fabrication of soft structures with 3D printing technology and its various applications.

• Journal of the Korean Society of Industry Convergence
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• v.6 no.3
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• pp.247-252
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• 2003

This study is to research on two phase printing method by use of colorants extracted from sappan wood. As for the research, printing effect of printing paste, streaming time, optimal mordant concentration, change of surface color and colorfastness were measured. This experiment showed that modified starch were best on surface color among the modified starch, sodium-alginate, guar gum. And the surface color was best when the steaming time was 60 minutes, mordant concentration 8%(ow.f). And for colorfastness experiment, colorfastness to drycleaning was good, but colorfastness to light and colorfastness to washing showed no desirable result.