• Journal of the Society of Naval Architects of Korea
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• v.29 no.2
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• pp.30-37
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• 1992

Since a ship is a complex steel construction which consists of sculptured surfaces and inner surface members, a high technique of information modeling is indispensable to describe the form of hull surface and steel structure members consistently. A model contains both topological and geometrical information of the structural members. Therefore, the hull form should be represented by the wireframe of surface model so that the accuracy in each design stage is satisfied. The structural members like plane surfaces, stiffeners and the relations between such members are to be described systematically in data base. A collection of the data stored in database is a model to be built. The model will be used not only to generate the drawings and documents for ship design and production but also to interconnect other systems such as compartmentation, outfitting, piping, etc. Computer graphics is adopted of the visualization of model.

• Applied Microscopy
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• v.43 no.2
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• pp.75-80
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• 2013

The morphological features of pollen grains collected from the broad-leaved and cylindrical-leaved Portulaca species of the Hawaiian Islands were investigated. The variation in size and surface pattern were examined using scanning electron microscopy and statistical analysis. Pollens of the Portulaca were apolar grains of monads exhibiting apertures, colpi, and relatively thin echini. Of particular interest was the differing size of pollen grains among the species studied. Pollens of the broad-leaved Portulaca were considerable in size with a length of about $73{\sim}86{\mu}m$, while the cylindrical-leaved Portulaca tended to have smaller pollen grains ranging from 50~65 in diameter. The smallest pollens were found in cultivar 2 having an average of $43{\mu}m$. The pollen was intectate, and the exine surface appeared granulous, having sculptured elements of spinules and puncta. Two types of puncta were discerned; one forming an operculum, and the other, a simple perforation. Numerous spinules and small puncta were found throughout the cylindrical-leaved Portulaca. In the present study, morphological features of pollen grains from ten Hawaiian Portulaca species, including endemic and unknown taxa, revealed the aforementioned pattern of variation. This paper aim to provide morphological information that could be of phylogenetic value within the Hawaiian Portulaca.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.4
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• pp.68-75
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• 2005

This paper presents a new method for the optimization of feed rate in sculptured surface machining. A NC verification model based on Z-map was utilized to obtain chip load according to feed per tooth. This optimization method can regenerate a new NC program with respect to the commanded cutting conditions and the NC program that was generated from CAM system. The regenerated NC program has not only the same data of the ex-NC program but also the updated feed rate in every block. The new NC data can reduce the cutting time and produce precision products with almost even chip load to the feed per tooth. This method can also reduce tool chipping and make constant tool wear.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.12
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• pp.2009-2018
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• 2001

This paper presents a region offsetting algorithm for tool-path generation. The proposed region offsetting algorithm is developed by expanding the 'PWID offset algorithm [Choi and Park, 1999]'designed to offset a simple polygon. The PWID offset algorithm has three important steps; 1) remove 'local invalid ranges'by invoking a PWID test, 2) construct a raw offset owe and 3) remove 'global invalid ranges'by finding self-intersections of the raw offset cure. To develop a region offsetting algorithm, we modified the PWID offset algorithm by expanding the concept of the 'global invalid range'in the third step. The time complexity of the proposed algorithm is approximately Ο(n), where n is the number of points, and it is free of numerical errors for practical purposes. The proposed algorithm has been implemented and tested with various real regions obtained by intersecting a sculptured surface with a plane.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.2
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• pp.133-140
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• 2009

Presented in this paper is a method to generate round-endmill toolpaths for sculptured surfaces represented as a triangular mesh model. The proposed method is applicable in toolpath generation for ball-endmills and flat-endmills because the round-endmill is a generalized tool in three-axis NC (numerical control) milling. The method uses a wireframe model as the offset model that represents a cutter location surface. Since wireframe models are relatively simple and fast to calculate, the proposed method can process large models and keep high precision. Intersection points with the wireframe offset model and a tool guide plane are calculated, and intersection curves are constructed by tracing the intersection points. The final step of the method is extracting regular curves from the intersection curves including degenerate and self-intersected segments. The proposed method is implemented and tested, and a practical example is presented.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.410-413
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• 2005

There are technical requirements to manufacture large size functional parts with not only simple geometries like a flat or spherical surface but also sculptured geometries. In addition, the required machining accuracy for these parts is becoming more severe day-by-day. In general, the forms of machined parts are determined by relative position between the workpiece and the tool during cutting. To improve machining accuracy, the relative position error should be maintained within the required accuracy. This study deals with estimation and calibration of depth of cut using AE signal in micro-machining.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.22 no.3_1spc
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• pp.489-495
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• 2013

This study analyzed thevariation in the cutting force when the cutting area of a terrace volume is machined, which is generally left after the rough cutting of a sculptured surface. The numerically simulated results for the cutting forces are compared with cutting force measurements by considering the theoretical prediction of the cutting area formation and specific cutting volume. The variation in the cutting force is measured using a dynamometer installed on a machining center for 19 different kinds of test pieces, which are selected according to the variation in the terrace volume factor, tool diameter factor, and cutting depth factor. As a result, it is verified that the cutting forces evaluated by the numerical analysis coincide with the measured cutting forces, and it is proposed as a practical cutting force prediction model.

• Journal of the Society of Naval Architects of Korea
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• v.30 no.1
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• pp.1-9
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• 1993

Various geometric modeling techniques for a hull have been developed with wide application of computer to the ship design. Up to now, they are used for the representation of the sculptured surface with the piecewise polynominal curves or surfaces for a conventional hull. In this paper, a convenient and accurate modeling technique that is instancing and blending of the geometry primitives is introduced for a non-conventional hull such as SWATH, trimaran, caisson etc. Geometric characteristics, hydrostatic particulars and stability of the definded hull are calculated.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.5 no.4
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• pp.47-52
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• 1996

The interpolator is very important in CNC machines. This study proposed a parametric curve interpolator(PCI) which can be used for machining any sculptured surface represented in a parametric form and generates commands for tool motion between CAD data points according to given accuracy demands. The proposed interpolator is superior to the existing linear interpolator in accuracy, feed rate and acceleration continuity. Moreover in comparison to the recently developed cubic spline interpolator, the PCI has the capability of handling higher order parametric curves and also ensures precise tracking in the velocity domain. Results from real time simulations and experiments on open architecture CNC machines equipped with the proposed interpolator are presented to show its practical capagility. It is believed that the combination of the proposed interpolator and the open architecture machine controller further advances the area of command generation which is an important aspect of CAD/CAM.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.9
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• pp.53-57
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• 2009

There are technical requirements to manufacture large size functional parts with not only simple geometries like a flat or spherical surface but also sculptured geometries. In addition, the required machining accuracy for these parts is becoming more severe. In general, the form accuracy of machined parts is determined by the relative position between workpiece and tool during machining process. To improve machining accuracy the relative position errors should be maintained within the required accuracy. This study deals with the estimation and calibration of depth of cut using the AE signal in micro-machining. Also, this sensing technique can be applied to detect the initial contact between workpiece and tool.