• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.24 no.3
• /
• pp.334-341
• /
• 2015

This paper summarizes the results of an investigation into the environmental factors that have an indirect impact on parts quality, as well as those process variables and modeling information that have a direct impact. The effects of strength, surface hardness, roughness, and accuracy of shape, that is, qualities that users generally need to know, were evaluated with laminating direction experimentally. The 3D printing methods used in this experiment were fused deposition modeling (FDM), stereolithography apparatus (SLA), selective laser sintering (SLS), 3D printing (3DP) and laminated object manufacturing (LOM). The goal was to achieve a high standard of quality control and product quality by optimizing the fabrication process.

• Journal of the Korean Society for Precision Engineering
• /
• v.24 no.5
• /
• pp.97-103
• /
• 2007

A novel selective metallization process to fabricate the fine conductive line based on inkjet printing has been investigated. Recently, Inkjet printing has been widely used in flat panel display, electronic circuits, biochips and bioMEMS because direct inkjet printing is an alternative and cost-effective technology for patterning and fabricating objects directly from design without masks. The photosensitive etching resist used in this process is an organic polymer which becomes solidified when exposed to ultraviolet lights and has high viscosity at ambient temperature. A piezoelectric-driven inkjet printhead is used to dispense 20-30 ${\mu}m$ diameter droplets onto the copper substrate to prevent subsequent etching. Repeatability of circuitry fabrication is closely related to the formation of steady droplets, adhesion between etching resist and copper substrate. Therefore, the ability to form small and stable droplets and surface topography of the copper surface and chemical attack must be taken into consideration for fine and precise patterns. In this study, factors affecting the pattern formation such as adhesion strength, etching mechanism, UV curing have been investigated. As a result, microscale copper patterns with tens of urn high have been fabricated.

• The Journal of the Korean dental association
• /
• v.58 no.1
• /
• pp.19-26
• /
• 2019

Purpose: The purpose of this study is to compare the adhesion of Candida albicans according to build angle in 3D printing denture base resin. Methods: The 3D printing was performed by setting the build angle of the disk type specimen designed by CAD program at 0 degree, 30 degrees, 60 degrees, and 90 degrees. Surface roughness was measured using a non-contact 3D microsurface profiler. The specimens were incubated in Candida albicans suspension for 24 hours. The attached Candida albicans were detached by cell scraper. The suspension of detached C. albicans was serially diluted and plated on Trypticase soy broth. After 48 hours of incubation, total colony forming unit was counted. Results: There was no significant difference in surface roughness(Sa) between the test groups, but the interlayer boundary was observed. There was no statistically significant difference in total colony forming units of Candida albicans between the test groups. Conclusion: There was no difference in the average surface roughness and adhesion of Candida albicans between the specimens. It is considered that the setting of the build angle should be set considering the accuracy or strength rather than the roughness of the surface.

• Journal of the Korean Society of Clothing and Textiles
• /
• v.47 no.2
• /
• pp.311-322
• /
• 2023

In this study, the properties of various material combinations were evaluated and an ideal material for fabricating protection pads for women's army combat uniforms was determined. Eight specimens were used for the evaluation: two types of materials, namely thermoplastic polyurethane for 3D printing, T and ethylene-vinyl acetate, E; two infill densities, namely 10%, 10 and 30%, 30; two types of pad designs, i.e., without holes, A and with holes, B; 2×2×2=8 and control E. The tensile strength, flexural strength, impact absorption, and weight of these specimens were evaluated. Results revealed that E was the most flexible material; however, its tensile strength and impact absorption were very low. Protection pads made from T (T-10A, T-10B, T-30A, and T-30B) had excellent tensile strength and impact absorption; however, they had low performance in ease of movement. Alternatively, protection pad with holes and an infill density of 30% produced using a combination of T and E had a high initial tensile modulus and exhibited excellent impact absorption. Moreover, it was flexible and light, which satisfies the standards and conditions required by protection pads. However, if T-E-10A and T-E-30B exhibited low impact absorption, as required, they can be regarded as appropriate materials for protection pads.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.23 no.6
• /
• pp.99-104
• /
• 2019

In the present study is focused on the evaluation of the shrinkage characteristics of mix proportion using viscosity agent for printing. Also, another purpose is to compare the shrinkage properties of the mold cast specimen with the additive manufactured specimen using 3D printing techniques. Viscosity agent makes the shrinkage was reduced by an average of 25% (as of 56 days) compared to the reference mix. The effects of reduced shrinkage were also founded, with a reduction of about 15% (as of 28 days).As a result of evaluating the shrinkage using the additive manufactured specimen and the mold cast specimen prepared by the printing mix, the shrinkage of the additive manufactured specimen was reduced by about 25% (based on 28 days). Based on the results of this study, it is possible to predict the shrinkage rate and the occurrence of cracks due to shrinkage on the printing of cement-based composite materials using 3D printing.

• Biomedical Engineering Letters
• /
• v.8 no.4
• /
• pp.337-344
• /
• 2018

Additive manufacturing (AM) is an alternative metal fabrication technology. The outstanding advantage of AM (3D-printing, direct manufacturing), is the ability to form shapes that cannot be formed with any other traditional technology. 3D-printing began as a new method of prototyping in plastics. Nowadays, AM in metals allows to realize not only net-shape geometry, but also high fatigue strength and corrosion resistant parts. This success of AM in metals enables new applications of the technology in important fields, such as production of medical implants. The 3D-printing of medical implants is an extremely rapidly developing application. The success of this development lies in the fact that patient-specific implants can promote patient recovery, as often it is the only alternative to amputation. The production of AM implants provides a relatively fast and effective solution for complex surgical cases. However, there are still numerous challenging open issues in medical 3D-printing. The goal of the current research review is to explain the whole technological and design chain of bio-medical bone implant production from the computed tomography that is performed by the surgeon, to conversion to a computer aided drawing file, to production of implants, including the necessary post-processing procedures and certification. The current work presents examples that were produced by joint work of Polygon Medical Engineering, Russia and by TechMed, the AM Center of Israel Institute of Metals. Polygon provided 3D-planning and 3D-modelling specifically for the implants production. TechMed were in charge of the optimization of models and they manufactured the implants by Electron-Beam Melting ($EBM^{(R)}$), using an Arcam $EBM^{(R)}$ A2X machine.

• Journal of Powder Materials
• /
• v.30 no.2
• /
• pp.140-145
• /
• 2023

Although the Ti-6Al-4V alloy has been used in the aircraft industry owing to its excellent mechanical properties and low density, the low formability of the alloy hinders broadening its applications. Recently, laser-powder bed fusion (L-PBF) has become a novel process for overcoming the limitations of the alloy (i.e., low formability), owing to the high degree of design freedom for the geometry of products having outstanding performance used in high-tech applications. In this study, to investigate the effect of bulk shape on the microstructure and mechanical properties of L-PBFed Ti-6Al-4V alloys, two types of samples are fabricated using L-PBF: thick and thin samples. The thick sample exhibits lower strength and higher ductility than the thin sample owing to the larger grain size and lower residual dislocation density of the thick sample because of the heat input during the L-PBF process.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.26 no.4
• /
• pp.73-80
• /
• 2022

This study evaluated changes in fluidity and rheological properties over time for 3D printed composite materials, and evaluated compressive strength and splitting tensile strength properties for laminated and molded specimens. The composite material for 3D printing starts to change rapidly after 30 minutes of extrusion, and the viscosity of the material tends to be maintained up to 90 minutes, but it was confirmed that construction within 60 minutes after mixing is effective. The compressive strength of the laminated test specimen showed equivalent or better performance at all ages compared to the molded test specimen. In the stress-strain curve of the laminated specimen, the initial slope was similar to that of the molded specimen, but the descending slope was on average 1.9 times higher than that of the molded specimen, indicating relatively brittle behavior. The splitting tensile strength of the P-V laminated specimen was about 6% lower than that of the molded specimen. It is judged that this is because the interfacial adhesion force against the vertical load is affected by the pattern direction of the laminated test specimen.

• The Journal of Advanced Prosthodontics
• /
• v.12 no.5
• /
• pp.322-328
• /
• 2020

PURPOSE. This study evaluated the shear bond strength between 3D printed provisional resin and conventional provisional resin depending on type of conventional provisional resin and different surface treatments of 3D printed resin. MATERIALS AND METHODS. Ninety-six disc-shaped specimens (Ø14 mm × 20 mm thickness) were printed with resin for 3D printing (Nextdent C&B, Vertex-Dental B. V., Soesterberg, Netherlands). After post-processing, the specimens were randomly divided into 8 groups (n=12) according to two types of conventional repair resin (methylmethacrylate and bis-acryl composite) and four different surface treatments: no additional treatment, air abrasion, soaking in methylmethacrylate (MMA) monomer, and soaking in MMA monomer after air abrasion. After surface treatment, each repair resin was bonded in cylindrical shape using a silicone mold. Specimens were stored in 37℃ distilled water for 24 hours. The shear bond strength was measured using a universal testing machine at a crosshead speed of 0.5 mm/min. Failure modes were analyzed by scanning electron microscope. Statistical analysis was done using one-way ANOVA test and Kruskal-Wallis test (α=.05). RESULTS. The group repaired with bis-acryl composite without additional surface treatment showed the highest mean shear bond strength. It was significantly higher than all four groups repaired with methylmethacrylate (P<.05). Additional surface treatments, neither mechanical nor chemical, increased the shear bond strength within methylmethacrylate groups and bis-acryl composite groups (P>.05). Failure mode analysis showed that cohesive failure was most frequent in both methylmethacrylate and bis-acryl composite groups. CONCLUSION. Our results suggest that when repairing 3D printed provisional restoration with conventional provisional resin, repair with bis-acryl composite without additional surface treatment is recommended.

• The Journal of Advanced Prosthodontics
• /
• v.12 no.4
• /
• pp.218-224
• /
• 2020

PURPOSE. The objectives of this study were to evaluate the fracture strength and fracture patterns of provisional crowns fabricated from different materials and techniques after receiving stress from a simulated oral condition. MATERIALS AND METHODS. A monomethacrylate-based resin (Unifast Trad) and a bis-acryl-based (Protemp 4) resin were used to fabricate provisional crowns using conventional direct technique. A milled monomethacrylate resin (Brylic Solid) and a 3D-printed bis-acrylate resin (Freeprint Temp) were chosen to fabricate provisional crowns using the CAD/CAM process. All cemented provisional crowns (n=10/group) were subjected to thermal cycling (5,000 cycles at 5°-55℃) and cyclic occlusal load (100 N at 4 Hz for 100,000 cycles). Maximum force at fracture was tested using a universal testing machine. RESULTS. Maximum force at fracture (mean ± SD, N) of each group was 657.87 ± 82.84 for Unifast Trad, 1125.94 ± 168.07 for Protemp4, 953.60 ± 58.88 for Brylic Solid, and 1004.19 ± 122.18 for Freeprint Temp. One-way ANOVA with Tamhane post hoc test showed that the fracture strength of Unifast Trad was statistically significantly lower than others (P<.01). No statistically significant difference was noted among other groups. For failure pattern analysis, Unifast Trad and Brylic Solid showed less damage than Protemp 4 and Freeprint Temp groups. CONCLUSION. Provisional crowns fabricated using the CAD/CAM process and the conventionally fabricated bis-acryl resins exhibited significant higher fracture strength compared to conventionally fabricated monomethacrylate resins after the aging regimen. Therefore, CAD/CAM milling and 3D printing of provisional restorations may be good alternatives for long term provisionalization.