• Title/Summary/Keyword: Machining of large parts

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CNC Tool Path Planning for Free-Form Sculptured Surface with a New Tool Path Interval Algorithm (새로운 공구경로간격 알고리듬을 이용한 자유곡면에서의 CNC 공구경로 계획)

  • Lee, Sung-Gun;Yang, Seung-Han
    • Journal of the Korean Society for Precision Engineering
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    • v.18 no.6
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    • pp.43-49
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    • 2001
  • A reduced machining time and increased accuracy for the sculptured surface are very important when producing complicated parts. The step-size and tool-path interval are essential components in high speed and high resolution machining. If they are small, the machining time will increase, whereas if they are large, rough surfaces will be caused. In particular, the machining time, which is key in high speed machining, is affected by the tool-path interval more than the step-size. The conventional method for calculating the tool=path interval is to select a small parametric increment of a small increment based on the curvature of the surface. However, this approach also has limitations. The first is that the tool-path interval can not be calculated precisely. The second is that a separate tool-path interval needs to be calculated in each of the three cases. The third is that the conversion from Cartesian domain to parametric domain or vice versa must be necessary. Accordingly, the current study proposes a new tool-path interval algorithm that do not involve a curvature and that is not necessary for any conversion and a variable step-size algorithm for NURBS.

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Ultrahigh Vacuum Technologies Developed for a Large Aluminum Accelerator Vacuum System

  • Hsiung, G.Y.;Chang, C.C.;Yang, Y.C.;Chang, C.H.;Hsueh, H.P.;Hsu, S.N.;Chen, J.R.
    • Applied Science and Convergence Technology
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    • v.23 no.6
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    • pp.309-316
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    • 2014
  • A large particle accelerator requires an ultrahigh vacuum (UHV) system of average pressure under $1{\times}10^{-7}$ Pa for mitigating the impact of beam scattering from the residual gas molecules. The surface inside the beam ducts should be controlled with an extremely low thermal outgassing rate under $1{\times}10^{-9}Pa{\cdot}m^3/(s{\cdot}m^2)$ for the sake of the insufficient pumping speed. To fulfil the requirements, the aluminum alloys were adopted as the materials of the beam ducts for large accelerator that thanks to the good features of higher thermal conductivity, non-radioactivity, non-magnetism, precise machining capability, et al. To put the aluminum into the large accelerator vacuum systems, several key technologies have been developed will be introduced. The concepts contain the precise computer numerical control (CNC) machining process for the large aluminum ducts and parts in pure alcohol and in an oil-free environment, surface cleaning with ozonized water, stringent welding process control manually or automatically to form a large sector of aluminum ducts, ex-situ baking process to reach UHV and sealed for transportation and installation, UHV pumping with the sputtering ion pumps and the non-evaporable getters (NEG), et al. The developed UHV technologies have been applied to the 3 GeV Taiwan Photon Source (TPS) and revealed good results as the expectation. The problems of leakage encountered during the assembling were most associated with the vacuum baking which result in the consequent trouble shootings and more times of baking. Then the installation of the well-sealed UHV systems is recommended.

Development of a Multi-Tasking Machine Tool for Machining Large Scale Marine Engine Crankshafts and Its Design Technologies (대형 선박엔진 크랭크샤프트 가공용 복합가공기 기술 개발)

  • An, Ho-Sang;Cho, Yong-Joo;Choi, Young-Hyu;Lee, Deug-Woo
    • Journal of the Korean Society for Precision Engineering
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    • v.29 no.2
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    • pp.139-146
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    • 2012
  • A multi-tasking machine tool for large scale marine engine crankshafts has been developed together with design technologies for its special devices. Since work pieces, that is, crankshafts to be machined are big and heavy; weight of over 100 tons, length of 10 m long, and diameter of over 3.5 m, several special purpose core devices are necessarily developed such as PTD (Pin Turning Device) for machining eccentric pin parts, face place and steady rest for chucking and resting heavy work pieces. PTD is a unique special purpose device of open-and-close ring typed structure equipped with revolving ring spindle for machining eccentric pins apart from journal. In order to achieve high rigidity of the machine tool, structural design optimization using TMSA (Taguch Method based Sequential Algorithm) has been completed with FEM structural analysis, and a hydrostatic bearing system for the PTD has been developed with theoretical hydrostatic analysis.

Automatic Generation of Machining Sequence for Machined Parts Using Machining Features (특징형상을 이용한 절삭가공부품의 가공순서 자동생성)

  • Woo, Yoonhwan;Kang, Sangwook
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.17 no.2
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    • pp.642-648
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    • 2016
  • As 3D solid modeling prevails, a range of applications have become possible and intensive research on the integration of CAD/CAM has been conducted. As a consequence, methods to recognize the machining features from CAD models have been developed. On the other hand, generating a machining sequence using the machining features is still a problem due to a combinatorial problem with a large number of machining features. This paper proposes a new method that utilizes the precedence constraints through which the number of the combinations is reduced drastically. This method can automatically generate machining sequences requiring the lowest amount of machining time. An airplane part was used to test the usefulness of the proposed method.

Method to Simulate the Automatic Processing of Large Aircraft Wing Ribs (대형항공기 날개 리브 가공을 위한 자동화 공정 시뮬레이션)

  • Song, Chul Ki;Lee, Dae-geon;Lee, Chang-beom;Kim, Gab-soon
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.19 no.9
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    • pp.85-92
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    • 2020
  • In this study, the automatic processing of the wing ribs of large aircraft was simulated. Specifically, in the simulation for the automatic processing of the fly ribs, the process of the automated loading device with a robot was examined, along with the wing rib processing and manufacturing automation processes. Moreover, the process time, corresponding to all the stages in the wing rib processing, was calculated. The results pertaining to the machining and manufacturing times of 34 wing ribs (Nos. 1-17), as obtained through the proposed simulation approach, indicated that the total machining time for the left and right wing ribs and rib guns was 537.7 h. The production time was calculated as 1,117.4 h. It is considered that the processing of the wing ribs of large aircraft can be automated in a factory, based on the results of the proposed simulation process.

High Precision Hybrid Milling Machine Using Dual-Stage (듀얼스테이지를 이용한 고정밀도의 하이브리드 밀링머신)

  • Chung, Byeong-Mook;Yeo, In-Joo;Ko, Tae-Jo;Lee, Cheon
    • Journal of the Korean Society for Precision Engineering
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    • v.25 no.7
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    • pp.39-46
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    • 2008
  • High precision machining technology has become one of the important parts in the development of a precision machine. Such a machine requires high speed on a large workspace as well as high precision positioning. For machining systems having a long stroke with ultra precision, a dual-stage system including a global stage (coarse stage) and a micro stage (fine stage) is designed in this paper. Though linear motors have a long stroke and high precision feed drivers, they have some limitations for submicron positioning. Piezo-actuators with high precision also have severe disadvantage for the travel range, and the stroke is limited to a few microns. In the milling experiments, the positional accuracy has been readily achieved within 0.2 micron over the typical 20 mm stroke, and the path error over 2 micron was reduced within 0.2 micron. Therefore, this technique can be applied to develop high precision positioning and machining in the micro manufacturing and machining system.

Implementation of Concurrent Engineering for Large Assembly Design:Part(I)- Assembly-centric Modeling Methodology as BOM Structrue- (부품수가 많은 조립체 설계를 위한 동시공학의 구현: Part(I)- BOM에 따른 조립체 중심적 모델링 방법론-)

  • 정융호
    • Korean Journal of Computational Design and Engineering
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    • v.2 no.2
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    • pp.93-102
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    • 1997
  • Most design changes are due to interferences and fit-up as parts are assembled if such a large product as an automobile or an aircraft is developed by many concurrent engineers. In this part (1) of the thesis, the assembly-centric modeling methodology with CAD systems is proposed in order to reduce the design changes. Unlike part-centric modeling method, a part is modeled with its own coordinate system which is used in downstream process as machining and measuring. The part coordinates initially have the same orientation as its assembly which is predefined in BOM (Bill of Material). Then, the corrdinates origin of the part is moved to its location to be assembled from that of its assembly coordinate system. To implement this methodology, the position data of the part w.r.t. its assembly are stored in a database to build the same hierarchical assembling structure as BOM structure. This modeling approach has the advantage of reflecting asembling sequence, because the process of positioning parts is similar to that of real assembling. And with the method, a designer can easily adjust all of the part positions of an assembly to resolve interferences if he modifies just the coordinates origin of the assembly, which results in moving included parts and assemblies together.

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The Position Decision Experiment of Magnetic Sensor in Ball-screw Driven Linear Stage (볼나사 구동 리니어 스테이지의 마그네틱 센서 위치결정 실험)

  • Cha, Young-Youp
    • Journal of Institute of Control, Robotics and Systems
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    • v.19 no.1
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    • pp.10-14
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    • 2013
  • High precision machining technology has become one of the important parts in the development of a precision machine. Such a machine requires high precision positioning as well as high speed on a large workspace. For machining systems having a high precision positioning with a long stroke, it is necessary to examine the repeatability of reference position decision. Though ball-screw driven linear stages equipped linear scale have high precision feed drivers and a long stroke, they have some limitations for reference position decision if they have not equipped the accurate home sensor. This study is performed to experimentally examine the repeatability for home position decision of a magnetic sensor as a home switch of ball-screw driven linear stage by using capacitance probe.

A Position Decision Experiment in Ball-screw Driven Linear Stage using a Photomicrosensor (포토 마이크로 센서를 이용한 볼나사 구동 리니어 스테이지의 위치결정 실험)

  • Cha, Young-Youp
    • Journal of Institute of Control, Robotics and Systems
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    • v.20 no.4
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    • pp.463-467
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    • 2014
  • High precision machining technology has become one of the most important parts in the development of a precision machine. Such a machine requires high precision positioning as well as high speed on a large workspace. For machining systems having high precision positioning with a long stroke, it is necessary to examine the repeatability of the reference position decision. Though ball-screw driven linear stages equipped with linear scale have high precision feed drivers and a long stroke, they have some limitations for reference position decisions if they have not been equipped with an accurate home sensor. This study is performed to experimentally examine the repeatability for home position decision of a photo micro sensor as a home switch of a ball-screw driven linear stage by using a capacitance probe.

A Study on the Characteristic Analysis of a Tilting Index Table for Machine Tools (공작기계 틸팅 인덱스 테이블의 특성 해석에 관한 연구)

  • Choi, Chi-Hyuk;Lee, Choon-Man
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.10 no.3
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    • pp.7-12
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    • 2011
  • In the recent field of 5-axis machine tools, it is necessary to improve machining ability. The tilting index table is a key unit in order to manufacture some non-rotational and 3-dimensional parts by using conventional machining centers. In this study, the structural analysis of a tilting index table is carried out and the displacement and distribution of stress in the tilting index table is analysed to design the table safely. The modal analysis is performed in order to confirm the frequency response about the vibration having a large effect on the machine tools. The dynamic analysis is performed in order to confirm the rigidity, and the structural stability has been verified.