• 제목/요약/키워드: casting post

검색결과 64건 처리시간 0.025초

THE EFFECTS OF SPURE AND INVENTS ON THE CASTING ACCURACY AND POROSITY OF TI-NI CASTINGS

  • Cho Lee-Ra;Yi Yang-Jin;Park Chan-Jin
    • 대한치과보철학회지
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    • 제41권3호
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    • pp.342-350
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    • 2003
  • Statement of problem. Titanium-Nickel alloy might be used in various prosthetic restorations since it has a unique property such as super-elasticity and high fatigue resistance. However, little is known about the casting ability of this alloy. Purpose. This in vitro study compared the casting accuracy and the porosity made with different investments and various sprue designs to ascertain what casting condition would be better for the fabrication of Ti-Ni cast restorations. Material and methods. A total of 70 Ti-Ni alloy crowns were made and divided into 7 groups of 10 copings on a metal master die. For measuring the effect of the sprue numbers, two groups with one and two 8-gauge sprues were compared. Moreover, the results of the conventional sprue and the double thickness sprues were compared. Three investments were used; carbon free phosphate bonded investment, titanium investment and gypsum bonded investment. The cast restorations were evaluated at 48 points on the entire circumferential margin with a stereomicroscope measuring in micrometers. Each crown was radiographically examined for casting defects and porosity. Data on casting accuracy were analyzed using two-way and Post hoc Scheffe's comparison to determine whether significant differences existed at the 95% confidence level. Student-Newman-Keuls test were performed to identify significant differences in the number of voids. Results. The double sprueing group and double thickness group had significantly less marginal discrepancy than the single sprueing group (P<.05 and P<.01, respectively). The castings with phosphate bonded investment showed the least marginal discrepancy and the smoothest surface. The castings invested in the gypsum bonded investment had the greatest gaps in margin and the largest failure rate. The double sprueing group and phosphate bonded investment group had significantly smaller void numbers and smaller void size than the other groups. Conclusion. Within the limitations of this in vitro study, the casting accuracy of the groups using thicker, double sprue design and the phosphate bonded investment was significantly superior. Moreover, void number and size were less than other groups.

대형주강품에 대한 CAE 시스템 개발 연구 (Development of a Simultaneous CAE System for the Application to Large Steel Castings)

  • 이영철;이두호;김종기;소찬영;최정길;홍준표
    • 한국주조공학회지
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    • 제17권5호
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    • pp.465-471
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    • 1997
  • An integrated computer program consisting of a pre-processor, main solver, and post-processor was developed for the design of large steel castings. The pre-processor, based on the AutoCAD, enables the user to produce approval drawings, casting design drawings and mesh diagrams in sequence using a personal computer. In the main solver, two numerical models were employed; one models the fluid flow during mold filling, and the other models the heat transfer and solidification. The post-processor can be used to present simulation results such as flow pattern, mold filling sequences, solidification times, temperature gradients and location of shrinkage defects by color graphics. In order to validate the applicability of the present integrated program, a series of experiments on simple-shaped steel castings were carried out. After the validation of the present model, it was applied to the casting design of the large steel anchor of an SC42 alloy. Various solidification parameters such as a temperature distribution and a solidification time in the casting and the mold were compared with those obtained experimentally. Simulated results predicting shrinkage defects were in good agreement with those obtained experimentally. It was found that the present method can be successfully applied to the quantitative casting design for complex-shaped large steel castings.

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사형제품 기계가공을 위한 안전금형 개발에 관한 연구 (A Study on Development of Safety Shell Molds for Precision Machining of Sand Mold Casting Product)

  • 최재훈;남승돈
    • 대한안전경영과학회지
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    • 제15권4호
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    • pp.179-184
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    • 2013
  • An accident from machine work is often fatal to the worker. This accident is mostly preventable through perfect process jig. In case of this machine work, however, the disaster frequently occurred because of the design which is not considered the beginning of product design, post-process and mass process of production. As for sand casting method, this has the merits of the production; the product is easily produced by manual labor. On the other hand, this method has the demerits of a bigger dimensional error contrary to other mass process of production. When the sand casting product is in machine work, there are various problems such as unsafe fix and excessive cutting, product desorption and rapid life depreciation of equipment and tools. Considering the characteristics of sand casting method, it is accepted as difficulty to improve the problems. In this study, it suggests shell mold method for mold instead of the machine work after the sand casting of the circle shape container product. And the surface accomplishes the following average of surface roughness Ra$9.94{\mu}m$ of machine work with the casting of flask mold by shell mold method. In accordance with the simplification of processing process and reducing the average thickness variation by mass production of product with detailed appearance, it has a good influence on safety accident prevention caused by production and damaged product. It is confirmed that making higher degree of size precision of all machine work product is possible to increase the safety and productivity, reduce the processing process and improve environment.

RP part 표면정도 향상을 위한 후처리 공정 개발 -왁스 코팅과 연삭 후처리 공정 이용- (Development of Post-process for Improving the Surface Roughness of Stereolithography parts - Using Wax Coating and Grinding Post-process -)

  • 안대건;김호찬;최홍태;이석희
    • 한국정밀공학회:학술대회논문집
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    • 한국정밀공학회 2002년도 추계학술대회 논문집
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    • pp.659-662
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    • 2002
  • SL(Stereolithography) part is made by piling up thin layers which causes the stair stepping effect at the surface of SL parts. This effect brings about excessive surface roughness and requires additional post-process finishing such as abrasive techniques that are detrimental to part geometry and time consuming. Hence a wax coating and grinding post-process is proposed to improve the surface quality of SL part. The wax that has suitable properties for the proposed post-process is coated all over the part surface. By grinding the thin layer of coated on the SL part only, the surface roughness can be improved without any damage on the part. From the experimental results, This approach is considered to be very practical fur die casting with RT(Rapid Tooling) techniques.

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광조형물의 표면조도 향상에 관한 연구 (A Study on Improving the Surface Roughness of Stereolithography Parts)

  • 안대건;김호찬;정해도;이석희
    • 한국정밀공학회지
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    • 제21권9호
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    • pp.196-203
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    • 2004
  • SL(Stereolithography) part is made by piling up thin layers which causes the stair stepping effect at the surface of SL parts. The effect brings about excessive surface roughness and cuts down the merits of using SL part. Hence, additional post-machining finishing such as traditional grinding is required. But the traditional post-machining is detrimental to part geometry and time consuming. In this study, therefore, a paraffin coating and grinding post-machining is newly proposed to improve the surface quality of SL fart. The paraffin which has suitable properties for the proposed post-machining is coated all over the part surface. By grinding the only over-coated paraffin based on boundary of the SL part surface, the surface roughness can be improved without any damage on the part. Also, it is verified that SL part finished by the proposed post-machining process can be applied for rapid tooling as pattern through manufacturing silicon rubber molding and casting test.

해류 수직구조를 파악하기 위한 LADCP Casting 및 자료처리 방법 (Casting Lowered-ADCP and Data Processing Methods for Configuring Vertical Current Structure)

  • 김응;전동철;신창웅;김동국
    • Ocean and Polar Research
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    • 제33권spc3호
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    • pp.397-407
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    • 2011
  • To understand the vertical structure of ocean currents from raw data observed by lowered-ADCP (LADCP), these data require post-processing. Data were processed using Krahman's version 10.8 processing software based on Matlab. It is estimated the influence of auxiliary data affecting the processed current structure. The bottom-tracked velocities and the GPS information significantly contribute the offset on reference velocities in the bottom layer and barotropic ones in the middle layer, respectively. Good quality data can be obtained when LADCP is least tilted in pitch and roll during observation. In situ application of LADCP to the (northward) volume transports of Kuroshio in the East China Sea proved to be 24.8. Sv (= $1{\times}10^6m^3s^{-1}$) in October 2007, and 28.2 Sv in June 2008, respectively. The volume transport is relatively large over the continental slope when compared to the shelf or the deep sea.

개량차분법에 의한 대형주강품의 3차원 응고해석 (Three Dimensional Solidification Analysis in Large Steel Castings by Modified Finite Difference Method)

  • 유승목;이두호;김종기;소찬영;홍준표
    • 한국주조공학회지
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    • 제11권1호
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    • pp.54-62
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    • 1991
  • A computer program which consists of pre-processor, main solidification simulator and post-processor has been developed for three dimensional solidification analysis of steel castings. The pre-processor is used for mesh generation in a small personal computing system. The modified finite difference method is adopted for the main solidification simulation algorithm. The post -processor graphically presents the simulation results and shows the formation of shrinkage defects. Several experiments on large steel castings in sand mold were carried out. The temperature variations in casting and mold with time are measured experimentally, and the results are compared with calculation results. Several numerical examples for the prediction of shrinkage cavity in large steel casting of SC42 and SCNCrM2 alloys are compared with experimental results. The effect of sleeve and chills on solidification patterns are also studied. Formation of shrinkage defects for the three cases of experimental castings are relatively well predicted by present model.

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Three-dimensional accuracy of different correction methods for cast implant bars

  • Kwon, Ji-Yung;Kim, Chang-Whe;Lim, Young-Jun;Kwon, Ho-Beom;Kim, Myung-Joo
    • The Journal of Advanced Prosthodontics
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    • 제6권1호
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    • pp.39-45
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    • 2014
  • PURPOSE. The aim of the present study was to evaluate the accuracy of three techniques for correction of cast implant bars. MATERIALS AND METHODS. Thirty cast implant bars were fabricated on a metal master model. All cast implant bars were sectioned at 5 mm from the left gold cylinder using a disk of 0.3 mm thickness, and then each group of ten specimens was corrected by gas-air torch soldering, laser welding, and additional casting technique. Three dimensional evaluation including horizontal, vertical, and twisting measurements was based on measurement and comparison of (1) gap distances of the right abutment replica-gold cylinder interface at buccal, distal, lingual side, (2) changes of bar length, and (3) axis angle changes of the right gold cylinders at the step of the post-correction measurements on the three groups with a contact and non-contact coordinate measuring machine. One-way analysis of variance (ANOVA) and paired t-test were performed at the significance level of 5%. RESULTS. Gap distances of the cast implant bars after correction procedure showed no statistically significant difference among groups. Changes in bar length between pre-casting and post-correction measurement were statistically significance among groups. Axis angle changes of the right gold cylinders were not statistically significance among groups. CONCLUSION. There was no statistical significance among three techniques in horizontal, vertical and axial errors. But, gas-air torch soldering technique showed the most consistent and accurate trend in the correction of implant bar error. However, Laser welding technique, showed a large mean and standard deviation in vertical and twisting measurement and might be technique-sensitive method.

한국전통가구의 금속 손잡이 영문표기 연구 - 한국 및 서구를 중심으로 - (A Study on Terminology of Metal Handles in Traditional Korean Furniture - Focusing on Korean and Western Furniture -)

  • 문선옥
    • 한국가구학회지
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    • 제23권4호
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    • pp.449-459
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    • 2012
  • The article aims to making a comparison between traditional Korean and Western furniture metal handles to give the detail information of the handle terms by analyzing the related literature including internet and interviews. In terms of that, the Korean and Western metal handles are compared in the types, components, materials, methods, and terms affecting the development made by the craftsmen before the Industrial Revolution about the mid or late 18th century. As a result, first, ring and drop pull handles were mostly and wooden knobs were a little used to open the furniture doors and drawers. The Korean drop pulls, Deulswae, came out after the ring pulls, Gori, while the Western drops called loop or bail handles as well, came out before the ring pulls. Second, the components were composed by ring, Gori, loop or bail, Deulswae, Post, Baemok, washer, Baemokbatchim, and backplate, Deulswaebatchim. Most of the Western handles were fastened by the bolt and nut, while the post of two strips, Baemok, fastened the Korean metal handles. Third, the metal handles were created of brass and iron mostly, gilded gold and silver. Forth, the method were largely used by casting, engraving, forging, plating, and hammering in the Korean handles, and by casting, molding, engraving, and stamped in the Western handles. Finally, the terms such as "knobs, pulls, drops, ring and drop pulls, loop or bail handles, posts, washers, backplate, casting, molding, engraving, forging, plating, and stamped" were clarified by the two comparison in Korean and English.

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Comparative clinical study of the marginal discrepancy of fixed dental prosthesis fabricated by the milling-sintering method using a presintered alloy

  • Kim, Mijoo;Kim, Jaewon;Mai, Hang-Nga;Kwon, Tae-Yub;Choi, Yong-Do;Lee, Cheong-Hee;Lee, Du-Hyeong
    • The Journal of Advanced Prosthodontics
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    • 제11권5호
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    • pp.280-285
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    • 2019
  • PURPOSE. The present study was designed to examine the clinical fit of fixed dental prosthesis fabricated by the milling-sintering method using a presintered cobalt-chromium alloy. MATERIALS AND METHODS. Two single metal-ceramic crowns were fabricated via milling-sintering method and casting method in each of the twelve consecutive patients who required an implant-supported fixed prosthesis. In the milling-sintering method, the prosthetic coping was designed in computer software, and the design was converted to a non-precious alloy coping using milling and post-sintering process. In the casting method, the conventional manual fabrication process was applied. The absolute marginal discrepancy of the prostheses was evaluated intraorally using the triple-scan technique. Statistical analysis was conducted using Mann-Whitney U test (${\alpha}=.05$). RESULTS. Eight patients (66.7%) showed a lower marginal discrepancy of the prostheses made using the milling-sintering method than that of the prosthesis made by the casting method. Statistically, the misfit of the prosthesis fabricated using the milling-sintering method was not significantly different from that fabricated using the casting method (P=.782). There was no tendency between the amount of marginal discrepancy and the measurement point. CONCLUSION. The overall marginal fit of prosthesis fabricated by milling-sintering using a presintered alloy was comparable to that of the prosthesis fabricated by the conventional casting method in clinical use.