@article{koc_lee_2002, title={Adaptive ruled layers approximation of STL models and multiaxis machining applications for rapid prototyping}, volume={21}, ISSN={["0278-6125"]}, DOI={10.1016/S0278-6125(02)80159-5}, abstractNote={This paper presents a new method of generating adaptive ruled layers for rapid prototyping (RP) processing of complex parts. To increase the accuracy and reduce the build time, an adaptive ruled layer approximation of the stereolithography (STL) models and multiaxis path planning for rapid prototyping are proposed. In this paper, a new method of constructing ruled layers from slicing STL points is developed to approximate the STL models with better surface accuracy. A technique of surface error analysis is presented to find the maximum errors at different layers of RP parts. By finding the RP surface errors, adaptive ruled layers are generated for the RP process of the STL CAD models. Using the constructed ruled layers of the STL models, the multiaxis material removal process is integrated with traditional RP processes to achieve better surface accuracy and to reduce the total RP build time. Computer implementation and illustrative examples are presented.}, number={3}, journal={JOURNAL OF MANUFACTURING SYSTEMS}, author={Koc, B and Lee, YS}, year={2002}, pages={153–166} }
 @article{koc_lee_2002, title={Non-uniform offsetting and hollowing objects by using biarcs fitting for rapid prototyping processes}, volume={47}, ISSN={["0166-3615"]}, DOI={10.1016/S0166-3615(01)00141-5}, abstractNote={This paper presents a new method of using non-uniform offsetting and biarcs fitting to hollow out solid objects or thick walls to speed up the part building processes on rapid prototyping (RP) systems. Building a hollowed prototype instead of a solid part can significantly reduce the material consumption and the build time. A rapid prototyped part with constant wall thickness is important for many different applications of rapid prototyping. To provide the correct offset wall thickness, we develop a non-uniform offsetting method and an averaged surface normals method to find the correct offset contours of the stereolithography (STL) models. Detailed algorithms are presented to eliminate self-intersections, loops and irregularities of the offsetting contours. Biarcs fitting is used to generate smooth cross-section boundaries and offset contours for RP processes. Implementation results show that the developed techniques can generate smoothed slicing contours with accuracy for rapid prototyping without suffering from handling the huge number of linear segments of the traditional methods.}, number={1}, journal={COMPUTERS IN INDUSTRY}, author={Koc, B and Lee, YS}, year={2002}, month={Jan}, pages={1–23} }
 @article{koc_ma_lee_2000, title={Smoothing STL files by Max-Fit biarc curves for rapid prototyping}, volume={6}, ISSN={["1355-2546"]}, DOI={10.1108/13552540010337065}, abstractNote={Presents a method of Max‐Fit biarc curve fitting technique to improve the accuracy of STL files and to reduce the file size for rapid prototyping. STL file has been widely accepted as a de facto standard file format for the rapid prototyping industry. However, STL format is an approximated representation of a true solid/surface model, and a huge amount of STL data is needed to provide sufficient accuracy for rapid prototyping. Presents a Max‐Fit biarc curve fitting technique to reconstruct STL slicing data for rapid prototyping. The Max‐Fit algorithm progresses through the STL slicing intersection points to find the most efficient biarc curve fitting, while improving the accuracy. Our results show that the proposed biarc curve‐fitting technique can significantly improve the accuracy of poorly generated STL files by smoothing the intersection points for rapid prototyping. Therefore, less strict requirements (i.e. loose triangle tolerances) can be used while generating the STL files.}, number={3}, journal={RAPID PROTOTYPING JOURNAL}, author={Koc, Bahattin and Ma, Yawei and Lee, Yuan-Shin}, year={2000}, pages={186–203} }
 @article{lee_koc_1998, title={Ellipse-offset approach and inclined zig-zag method for multi-axis roughing of ruled surface pockets}, volume={30}, ISSN={["0010-4485"]}, DOI={10.1016/S0010-4485(98)00051-7}, abstractNote={This paper presents a new method for 5-axis rough cutting of ruled surface pockets. An inclined zig-zag method is proposed for rough cutting the core material region, and an ellipse-offset method is developed for semi-roughing the residual material regions of ruled surface pockets. The ellipse-offset method is developed to calculate the non-constant offset curves for 5-axis tool path planning of rough cutting. Different from the traditional 21/2D machining method, the developed ellipse-offset method allows the cutter to change its tool orientation and to get as close to the part surface as possible in roughing. The proposed method allows the manufacturing engineers to use 5-axis machining to rough cut the parts to near-finish shape for finishing. Computer implementation and illustrative examples are presented in this paper.}, number={12}, journal={COMPUTER-AIDED DESIGN}, author={Lee, YS and Koc, B}, year={1998}, month={Oct}, pages={957–971} }