• 한국정밀공학회지
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• 제21권12호
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• pp.60-66
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• 2004

Increasing demands on precision machining of 3D free-form surface have necessitated the tool to move smoothly with varying feedrate. To this regard, parametric interpolators such as NURBS (Non-Uniform Rational B-Spline) interpolator have been introduced in CNC machining system. Such interpolators reduce the data burden in NC code, increase data transfer rate into NC controller, and finally give smooth motion while machining. In this research, a new concept to control cutting load in NURBS Interpolator was tried based on the curvature of curve. This is to protect cutting tool, and to have good machinability. For proof of the system, cutting force and surface topography were evaluated. From the experimental results. the interpolator is good enough for machining a free-form surface.

• 한국생산제조학회지
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• 제19권4호
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• pp.455-461
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• 2010

Automated magnetic abrasive polishing which can be applied after machining of the mold on a machine tool without unloading is very effective for finishing a complicated injection mold surface. This study aims to realize one step polishing of free form surface with the same machine tool. For this purpose, magnetic flux density according to the change of curvature radii was simulated for selecting polishing conditions and experimental verification was performed with a complicated mold of aluminum alloy. As a result, it was seen by the simulation that the magnetic flux density at a gradual curvature of the mold was higher than at a steep curvature and the higher magnetic flux density produced the better surface roughness in the experimentation. The deviation for the surface roughness of the mold decreased on the whole and the uniform mold surface was obtained after the automated magnetic abrasive polishing.

• 한국정밀공학회지
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• 제13권12호
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• pp.99-105
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• 1996

Increasing demands on precision machining of free-form surfaces have necessitated the tool to move not only with position error as small as possible, but also with smoothly varying feedrates. In this paper, linear, circular and spline interpolators were developed in reference-pulse type using PC. M-SAM and M-DAM were designed by the comparison and analysis of previous interpolation methods. Spline interpolator was designed to follow the free-form curves. To apply to the real cutting process, constant feedrate compensation and acceleration-deceleration compensation were conceived. Finally, its performance was tested using retrofitted milling machine. As a result, new interpolation algorithm is favorable in precision machining of free-form curves.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2006년도 추계학술대회 논문집
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• pp.467-468
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• 2006

• 한국정밀공학회지
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• 제16권4호통권97호
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• pp.129-137
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• 1999

A parametric curve interpolator has been proposed for machining curves instead of a linear interpolator in which curves are approximated by a set of line segment. The parametric curve interpolator is superior to linear interpolator in machining time and contour error and generate exact position commands directly from curve equations. In this paper, a new toolpath generation method is proposed based on the parametric curve interpolator. This method retains all the benefits of parametric curve interpolator and can bound the scallop height within a specified value. By interpolating curves and surfaces directly from the mathematical equations, the amount of data from CAD/CAM system to CNC controller can be significantly reduced. The proposed method was implemented on a CNC controller and was confirmed to give a better result than the other existing method.

• 한국산학기술학회논문지
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• 제20권1호
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• pp.290-296
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• 2019

차량용 HUD는 자동차 전면 유리창에 안전 운전과 편의 운전 관련 다양한 정보를 표시해 주는 장치로 중요한 역할을 수행한다. 본 논문에서는 증강현실 기술에 적용이 가능한 대면적 비구면 자유형상 미러를 가공하기 위해 초정밀 가공기를 이용하여 가공을 실시하였고 그 결과를 측정하였다. 초정밀 다이아몬드 절삭은 정밀도가 높을 뿐만 아니라 표면 거칠기와 잔류 응력을 낮게 할 수 있어서 우수한 표면 무결성을 갖는 고급 부품의 생산에 유리하다. 또한 비구면 자유 형상의 몰드를 사용함으로써 광학 전달 함수의 개선, 왜곡 경로의 감소 및 특수 이미지 필드 곡률의 실현과 같은 장점을 얻을 수 있다. 이와 같은 비구면 자유형상 금형을 가공하기 위한 방법으로는 초정밀가공기를 이용한 다이아몬드 절삭 방법을 사용하였으며, 제작된 비구면 자유형상 미러 금형의 평가는 비구면 형상 측정기를 이용하여 실시하였다. 이러한 방법에 의해 $1{\mu}m$ 이하의 형상 정밀도(PV)와 $0.02{\mu}m$ 이하의 표면 거칠기(Ra)를 갖는 비구면 자유형상 금형을 제작할 수 있었다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2001년도 춘계학술대회 논문집
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• pp.439-442
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• 2001

The Accuracy of a free-form artifact is affected by machine tool errors, machining process errors, environmental causes and other uncertainty. This paper deals with methodological approach about machine tool errors that are defined the relationship between CMM and OMM inspections of the free-form artifact. In order to analyze the measurement data, Reverse engineering was used. In other words, Surface of Free-Form Artifact is generated by NURBS surface approximation method. Finally, Volumetric error map is made to compare surface of CMM data with that of OMM data.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1988년도 한국자동제어학술회의논문집(국내학술편); 한국전력공사연수원, 서울; 21-22 Oct. 1988
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• pp.279-284
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• 1988

In this paper, NCTOP is an interactive NC auto programming system for two-dimensional machining. NCTOP consists of seven modules, that is pattern form input, free form input, AutoCAD interface, logic processing, postprocessor processing, output, and database upgrade module. The geometry information of a workpiece to be machined is put into NCTOP program. Then it generates NC program which is final output. NCTOP uses the machining dates from the data base.

• 한국정밀공학회지
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• 제20권10호
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• pp.31-40
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• 2003

In this paper, optimal cutting condition to minimize the form error in side wall machining with a flat end mill is studied. Cutting forces and tool deflection are calculated considering surface shape generated by the previous cutting such as roughing. Using the form error prediction method from tool deflection, optimal cutting condition considering form accuracy is investigated. Also, the effects of tool teeth number, tool geometry and cutting conditions on form error are analyzed. The characteristics and the difference of generated surface shape in up and down milling are discussed and over-cut free condition in up milling is presented. Form error reduction method through successive up and down milling is also suggested. The effectiveness and usefulness of the presented method are verified from a series of cutting experiments under various cutting conditions. It is confirmed that form error prediction from tool deflection in side wall machining can be used in optimal cutting condition selection and real time surface error simulation for CAD/CAM systems. This study also contributes to cutting process optimization for the improvement of form accuracy especially in precision die and mold manufacturing.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2001년도 추계학술대회 논문집
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• pp.106-110
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• 2001

The ball-end milling process is widely used in the die/mold industries, and it is very suitable for the machining of free-form surfaces. However, this process is inherently inefficient process to compared with the end-milling or face milling process, since it relays upon the machining at the cutter/surface contact point. The machined part is the result of continuous point-to-point machining on the free-form surface. And cusps (or scallops) remain at the machined part along the cutter paths and they give the geometrical roughness of the workpiece. Thus, for the good geometrical roughness of the workpiece, it is required very tightly spaced cutter paths in this ball-endmilling process. However, with the tight cutter paths, the geometrical roughness of the workpiece is not regular on the workpiece since the cusp height is variable in the previously developed ISO-parametric or Cartesian machining methods. This paper suggests a method of tool path generation which makes the geometrical roughness of workpiece be constant through the machined surface. In this method, Ferguson Surface design Model is used and cusp height is derived from the instantaneous curvatures. And, to have constant cusp height, an increment of parameter u or v is estimated along the reference cutter path. In ball-end milling experiments, the cusp pattern was examined, and it was proved that the geometrical roughness could be regular by suggested tool path generation method.