• IE interfaces
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• v.9 no.2
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• pp.119-128
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• 1996

A procedure is presented for a 3D-contour machining without cutter interferences. The 3D-contouring machining along a spatial curve is often required for manufacturing trimming and flange dies in motor industries. Input data for the machining contour is a spline curve with polynomial vector equation provided by CATIA system. Points are sampled on the contour curve and line segments and helical curves are approximated from the point data. Cutter interference is checked on the approximated spline and all of interference curves are substituted with interference-free helical curves for a tool path generation. The non-machined curve areas are locally machined by tools with smaller diameters. A tool radius offset is considered for generating NC data to be free with tool size.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.494-497
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• 2000

This paper presents the fine-shearing experimental investigation using brass sheets. Shearing including blanking, trimming, piercing, etc is one of the most frequently used processes in sheet metal manufacturing. In this study, an individual set of tooling was designed and fabricated to carry out experiment for shearing process. In order to investigate the effect of shearing surface correspond to die clearance, the profile of shearing surface was examined by using microscope. Futhermore, the relationship between shearing force and the profile of shearing surface was considered.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2001.05a
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• pp.231-234
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• 2001

Shearing, including blanking, trimming, piercing, etc, is one of the most frequently used processes in sheet metal manufacturing. In this paper, an individual set of tooling with an in-die sensor was designed and precisely fabricated to carry out the experiment for the shearing process investigation. Through various experiments, it has been examined the influence of process parameters such as clearance, edge material properties and pad configuration. Since the tension between the part and the scrap increases when the clearance increases, the clearance should be selected properly in order to reduce the burr height. Also removal of the lower pad makes the sheared surface worse and the shearing system unstable. The shearing force increases when the clearance decreases and the friction of the tooling material decreases. Dynamic reaction force is also important to obtain the fine sheared surfaces.

• Design & Manufacturing
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• v.16 no.1
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• pp.27-35
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• 2022

Thermoforming is a plastic manufacturing process that applies a force to stretch a film of heated thermoplastic material over an engineered mold to create a 3-dimensional shape. After forming, the shaped part can then be trimmed and finished to specification to meet an end-user's requirements. The process and thermoplastic materials are extremely versatile and can be utilized to manufacture parts for a very wide range of applications. In this study, based on K-BKZ nonlinear viscoelastic model, thermoforming process analysis was performed for an interior room-lamp. The predicted thickness was minimum at the corner of a molded film, and maximum at the center of the bottom. By using the Taguchi method of design of experiments, the effects of process conditions on residual stresses were investigated. The dominant factors were the liner thickness and the film heating time. As the thickness of the liner increased, the residual stress decreased. And it was found that the residual stress decreased significantly when the film heating temperature was higher than the glass transition temperature. A thermoforming mold and a trimming mold were manufactured, and the spring back was investigated through experiments. The dominant factors were film heating time, liner thickness, and lower mold temperature. As the film heating time and liner thickness increased, the spring back decreased. In addition, it was found that the spring back decreased as the lower mold temperature increased.

• JSTS:Journal of Semiconductor Technology and Science
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• v.9 no.3
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• pp.160-165
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• 2009

A 12b 2 MS/s cyclic ADC processing 3.3 Vpp single-ended rail-to-rail input signals is presented. The proposed ADC demonstrates an offset voltage less than 1 mV without well-known calibration and trimming techniques although power supplies are directly employed as voltage references. The SHA-free input sampling scheme and the two-stage switched op-amp discussed in this work reduce power dissipation, while the comparators based on capacitor-divided voltage references show a matched full-scale performance between two flash sub ADCs. The prototype ADC in a $0.18{\mu}m$ 1P6M CMOS demonstrates the effective number of bits of 11.48 for a 100 kHz full-scale input at 2 MS/s. The ADC with an active die area of $0.12\;mm^2$ consumes 3.6 m W at 2 MS/s and 3.3 V (analog)/1.8 V (digital).

• Journal of Technologic Dentistry
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• v.16 no.1
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• pp.57-77
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• 1994

The purpose of this study is to investigate the extent to which dental laboratories use proper materials, procedures, devices, and equipments to fabricate crown & bridge, PFM(Porcelain Fused to Metal) crown & bridge, partial denture, complete denture, and other prosteses. 100 laboratories in Seoul were selected for this investigation. Questionnaires were constructed focusing on five topocs:crown & bridge, PFM crown & bridge, partial denture, complete denture, and other prostheses. The results from this survey were as follows : 1. Most dental laboratories used old, inexpensive, and familiar materials rather than newly developed ones. 2. Most of the dental technicians did not stick to the standard procedures of handling materials, but to their own experiences. 3. Newly developed equipments to fabricate dental prostheses were possessed by nearly 30% dental laboratories. 4. About 80% of dental laboratories were using the procedures they had learned in the school : die trimming for accurate crown margin and softening heat treatment after RPD gold casting. But less than 30% of laboratories were shown to follow the boxing procedure to produce master cast and laboratory remounting in the process of complete denture. The findings show that dental laboratory procedures to fabricate dental prostheses are incomplete and inaccurate in some instances. So, further studies are neededs to clarify the causes of some inaccurate procedures, the better and more equipments should be supplied to produce the more accurate dental posthesis, and more efforts at enancing the appropriate use of dental materials and procedures should be made.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.9
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• pp.1027-1033
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• 2011

A VCM sheet is a metal sheet on which PET/PVC is coated for outer panels of home appliances. The purpose of this study is to obtain methods for suppressing PET tearing that occurs during the press forming of the VCM sheet. In order to identity the factors that minimize PET tearing, an FE analysis was performed. The occurrence of PET tearing cannot be predicted using the conventional forming limit diagram. PET is torn by friction between a die and sheet, which is caused by the thickening of material at a die corner. To reduce the thickening of material, the blank shape was re-designed and the thickened material at a flange was removed by a trimming process. The results of the FE-analysis involving modified process parameters showed that the thickness of the product at a die corner is distributed within the clearance of drawing and flangeforming process. A forming experiment was conducted to verify the proposed process parameters. A good final product was obtained without PET tearing of the VCM sheet.

• The Journal of Korean Academy of Prosthodontics
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• v.33 no.2
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• pp.358-394
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• 1995

The author studied the actual conditions on the production of dental prosthesis made in laboratories, and also studied interrelationships between dentists and laboratory technicians in both personal and technical aspects. Two hundred-eighty four technicians, work in dental laboratories presently, were surveyed via mail and direct contact during the period from June 1 to June 30 and August 27 to August 28 in 1994 respectively. The obtained results were as follows : 1. Among the respondents, 90.5% we re working in commercial dental laboratories and their laboratories were mainly located in the Seoul area(40.9%, P<0.05). The numbers of employees in these laboratories were less than 10 persons(70.0%, P<0.01), and 75.9% of these laboratories have been in operation less than 15 years. 2. Most laboratory procedures were accomplished according to established disciplines. However, procedures such as die trimming in fixed restorations and the qualifications of the people designing removable partial dentures were not. Other problem areas were boxing of the working cast, the person determining the posterior palatal seal area, selection and arrangement of artificial teeth, occlusion rim correction and laboratory remounting of the processed denture in complete denture restorations. 3. Only half of the requesting dentists could send work authorizations to the laboratories with their work and even so, its contents were quite lacking. Consequently, there must be some standards in writing work authorization. 4. Technicians most desired clean and accurate impressions in fixed and removable dentures, and enough tooth reduction in porcelain fused to metal restorations. 5. For the establishment of better relationships between dentist and dental technician, the respondents desired the establishment of equal footing first(33.5%), and frequent conversations and muture understanding second(25.9%).

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.437-438
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• 2006

Generally, the vertical roll process is used to achieve extensive width reduction in hot strip mill. However, it is difficult to avoid the defects such as dog-bone and seam-defect. The sizing press has been developed in response to the defects mentioned above. Especially, this study is carried out to investigate the deformation of slab by two-step sizing press. The deformation behavior in the width sizing process is more favorable than that in conventional vertical rolling edger. The objective of this study is to determine the optimal anvil shape parameters in the sizing press with two-step die from the viewpoint of edge-seam length. In general, the edge-seam defect occurs parallel to the rolling direction at both edges in horizontal rolling process after sizing press. The optimal combination of the parameters is determined by FE-simulation and Artificial Neural Network (ANN). The slab deformation in sizing press with convex anvil is analyzed by FE-simulation. The most suitable profile of the anvil is also discussed fur the improvement of trimming loss because of the side seam defect by FE-simulation and ANN.

• Journal of Welding and Joining
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• v.33 no.5
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• pp.53-60
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• 2015

Laser surface Melting Process is getting hardening layer that has enough depth of hardening layer as well as no defects by melting surface of substrate. This study used CW(Continuous Wave) Yb:YAG and STD11. Laser beam speed, power and beam interval are fixed at 70mm/sec, 2.8kW and 800um respectively. Hardness in the weld zone are equal to 400Hv regardless of melting zone, remelting zone overlapped by next beam and HAZ. Similarly, microstructures in all weld zone consist of dendrite structure that arm spacing is $3{\sim}4{\mu}m$, matrix is ${\gamma}$(Austenite) and dendrite boundary consists of ${\gamma}$ and $M_7C_3$ of eutectic phase. This microstructure crystallizes from liquid to ${\gamma}$ of primary crystal and residual liquid forms ${\gamma}$ and $M_7C_3$ of eutectic phase by eutectic reaction at $1266^{\circ}C$. After solidification is complete, primary crystal and eutectic phase remain at room temperature without phase transformation by quenching. On the other hand, microstructures of substrate consist of ferrite, fine $M_{23}C_6$ and coarse $M_7C_3$ that have 210Hv. Microstructures in the HAZ consist of fine $M_{23}C_6$ and coarse $M_7C_3$ like substrate. But, $M_{23}C_6$ increases and matrix was changed from ferrite to bainite that has hardness above 400Hv. Partial Melted Zone is formed between melting zone and HAZ. Partial Melted Zone near the melting zone consists of ${\gamma}$, $M_7C_3$ and martensite and Partial Melted Zone near the HAZ consists of eutectic phase around ${\gamma}$ and $M_7C_3$. Hardness is maximum 557Hv in the partial melted zone.