• Journal of Korean Institute of Industrial Engineers
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• v.21 no.4
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• pp.493-506
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• 1995

Presented in this paper is an algorithm to obtain the intersections of a polyhedral surface composed of triangle facets with a series of parallel planes for extracting machining information from the surface. The change of the topology of the intersection curves is caused by characteristic points of the surface when sectioning the surface with parallel planes. The characteristic points are internal maximum, internal minimum, internal saddle, boundary maximum, boundary minimum, boundary max-saddle, and boundary min-saddle points. The starting points of the intersects are found efficiently and robustly using the characteristic points. The characteristic points as well as the intersection contours can be used to evaluate the machining information for process planning, and to generate NC tool path in CAD/CAM system.

• 제어로봇시스템학회:학술대회논문집
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• 1997.10a
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• pp.1275-1278
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• 1997

Cutting process has been automated by progress of CNC and CAD/CAM, but polishing process has been depended on only experiential knowledge of expert. To automate the polishing pricess polishing robot with 2 degrees of freedom which is attached to a machining center with 3 degrees of freedom has been developed. this automatic polishing robot is able to keep the polishing tool normal on the curved surface of die to improve a performance of polishing. Polishing task for a curved surface die demands repetitive operation and high precision, but conventional control algorithm can not cope with the problem of disturbance such as a change of load. In this research, we develop robust controller using real time sliding mode algorithm. To obtain gain parameters of sliding model control input, the signal compression method is used to identify polishing robot system. To obtain an effect of 5 degrees of freedom motion, 5 axes NC data for polishing are divided into data of two types for 3 axis machining center and 2 axis polishing are divided into data of two types for 3 axis machining center and 2 axis polishing robot. To find an efficient polishing condition to obtain high quality, various experiments are carried out.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.11
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• pp.1958-1966
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• 2003

Three-axis CNC surface machining entails a series of processes including rough cutting, intermediate cutting and finish cutting for a reference surface defined in CAD/CAM. This study is targeting development of an integrated NURBS surface interpolator that can incorporate rough, intermediate and finish cutting processes. In each process, volume to be removed and cutting condition are different according to the shape of a part to be machined and the reference surface. Accordingly, the proposed NURBS surface interpolator controls motion in real-time optimized for the machining conditions of each process. In this paper, a newly defined set of G-codes is proposed such that NURBS surface machining through CNC is feasible with minimal information on the surface composition. To verify the usefulness of the proposed interpolator, through computer simulations on NURBS surface machining, total machining time, size of required NC data and cutting force variations are compared with the existing method.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.8
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• pp.1418-1425
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• 2003

In CAD systems, a surface to be machined is expressed by a series of curves, such as B-spline, Bezier and NURBS curves, which compose the surface and then in CAM systems the curves are divided into a large number of line or arc segments. These divided movement commands, however, cause many problems including their excessive size of NC data that makes almost impossible local adjustment or modification of the surface. To cope with those problems, the necessity of real-time curve or surface interpolators was embossed. This paper presents an efficient real-time tool-path generation method fur interpolation of NURBS surfaces in CNC machining. The proposed tool-path generation method is based on an improved iso-scallop strategy and can provide better precision than the existing methods. The proposed method is designed such that tool-path planning is easily managed in real-time. It proposed a new algorithm for regulation of a scallop height, which can efficiently generate tool-paths and can save machining time compared with the existing method. Through computer simulations, the performance of the proposed method is analyzed and compared with the existing method in terms of federate, total machining time and a degree of constraint on the scallop height.

• International Journal of CAD/CAM
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• v.4 no.1
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• pp.11-17
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• 2004

In this paper, an exponential bound of the distance between a Loop subdivision surface and its control mesh is derived based on the topological structure of the control mesh. The exponential bound is independent of the process of recursive subdivisions and can be evaluated without subdividing the control mesh actually. Using the exponential bound, we can predict the depth of recursion within a user-specified tolerance as well as the error bound after n steps of subdivision. The error-estimating approach can be used in many engineering applications such as surface/surface intersection, mesh generation, NC machining, surface rendering and the like.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1993.10a
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• pp.389-394
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• 1993

Die making process is classified into design,manufacturing,polishing,assembly, and performance test. Die polishing is not a machining process by cutting edge of tool, but it is finishing by relative cutting movement under the surface contact between grinding particles and workpiece, and this process comprised 30~40% of total manufacturing hours. However, die polishing process is still performed by the skilled workers. Now a days, it is very difficult to secure skilled workers due to the hardworking environment and this situation will be getting worse in the future which has great difficulty of dies and molds industries.This process has the common problem on the elimination of tedious manual polishing among the tool making industries. Therefore this study is aimed at the development of an automatic polishing attachment which could be attached onthe spindle of CNC machine tool and controlled by the NC program data created by CAD/CAM system. As a result, this study will contribute the realization of automatic fine polishing process and improvement of quality level of dies and molds.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.69-72
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• 2002

The geometry parameter of tool such as rake angle and clearance angle is defined clearly to solve the difference in communication between design and measurement stage. Using the developed simulation program, wheel is properly determined and end mill can be manufactured accurately. The performance test with well defined end mill provides sufficient information to decide optimal geometry. For machining hardened steel, end mills are designed and manufactured. Optimal rake angle and clearance angle is obtained from performance test. A specific software for automatic end mill production is developed far simulation and fur generation of NC code as Cad/CAM system.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.04b
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• pp.97-101
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• 1995

This paper describes a new surface finishing process which uses magnetic abrasive polishing. This is applied to automatic finishing of die & mold surface. Nowadays, most of die & mold meanufaturing procedures have been automated by the introduction of NC machine tool and CAD/CAM system. But the surface finishing of die & mold must be done by hand work of well-skilled workers. Though many attempts were tried in the past 15 years to eliminate this hand work, the automatic finishing of die & mold surface with 3D curvature has not been achieved yet. New magnetic abrasive finishing process is thought as one of the possible methods for the automation of 3D surface finishing. In order to improve the grindability of the method, ultra-high speed and 5-axis machining was introduce. The magnetic abrasive polishing which has adopted these methods was confirmend to improve the efficiencyof die & mold surface finishing.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.7 no.3
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• pp.99-103
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• 1998

The curved surface machined by plate end mill causes a excess non-cutting volume, in these cases ball end mill is used for the curved surfaces. This study is aimed to obtain the optimum cutting conditions of various cutting speed, table speed, tool diameter, radius of curvature roughness on the conditions of various cutting speed, tool diameter, radius of curvature when machining the curved surface using the ball end mill. After designing curve rates, obtaining NC data by CAD/CAM system through CC-Cartesian method and transferred the data through DNC system, we machined the specimens by the CNC machining center, The surface roughness of specimens was measured by surface roughness tester and CNC 3D coordinate measuring machine. The cutting condition were the same as follow velocity; 15, 20, 25 30m/min, feed rate;40, 60, 80, 100m/min and radius of curvature; 30,40,50,60mm, tool diameters; ø8, ø12, ø16, ø 20mm. Analizing the working results, we can acquire the optimum cutting condition of curved specimen at the cutting velocity of 20~25m/min and the feed rate of 80mm/min. As the same cutting condition the best surface roughness was showed at ø16mm of the tool diameter. But the tool diameter was smaller than ø8mm. we could improve for the surface roughness by controlling the cusp.

• Journal of the Society of Naval Architects of Korea
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• v.44 no.2 s.152
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• pp.198-209
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• 2007

In this paper, we present the gouging and collision-free tool-path generation for manufacturing model propellers using the 5-axis NC machine. Because it takes much time to generate tool-paths when we use general purpose CAD/CAM systems, a specific system would be necessary for marine propellers. Overall manufacturing process is composed of two steps: roughcut and finishcut steps. The roughcut is conducted using only 3-axis for efficient machining and the finishcut is done using 5-axis for avoiding collision. The tool-path that might happen to gouging is searched and the tool position is also decided for avoiding interference between the tool and the propeller blades. The present algorithm is applied extensively to the surface piercing propellers. Some results are demonstrated for its validation.