1. Introduction In recent years, products are required to follow the trend of fashion. It is very popular in using freeform surface to design the model of products. Designers, however, have to modify the surface of original models because of the different sizes when products are constructed based on a CAD model. In addition, in order to decrease the cost, products have same components. When designers modify a 3D CAD model, the shape of same components should be local constrained to make the adjoining surfaces remain continuous. The large difference between the industry of shoe manufacture and other industries is on one product with many different sizes. Take sports shoes grading as an example, grading for a standard full-size shoe (from # 6 to #18) has 21 different sizes. And a designer has to create a model for each size. Shoe sole can be divided into two main parts: one is the midsole and the other is the outsole. Thus, designers have to create 42 models for a full-size shoe. The amount of shoe manufacture is a challenge for a factory. In traditional factories, before designers create a 3D CAD model of a shoe, they still use a 2D cardboard traditions planning and milling machine to manufacture. Materials and methods This paper presents a customized shoe grading system that can save time and manufacturing costs and enhance the quality of a product. It is a quick and precise solution for all shoe grading needs. Grading procedure: We present the grading procedure (Fig. 1) consists of two stages, a preliminary stage and the grading stage. In the preliminary stage, grading parts containing the surface or curve data on the shoe component when we want to grade must be prepared. This can be done using an ordinary CAD system. In the grading stage, grading data, schedules, and parameters are set up for grading. The following flow chart gives an overview of the complete procedure. Preliminary Setup: In this system before using shoe grading, a preliminary stage is required. Surfaces and curves of shoe areas and components need to be prepared and arranged properly to ensure that the data used will result in grading accuracy. For examples (Fig.2~ Fig.5) of the curves and surfaces required for grading various components and ways to arrange these curves and surfaces so that they can be used in the grading system. Acknowledgments We thank Acer Chen, the director of the mold factory, Pou Chen Group in Taiwan for providing shoe mold data used in our research and for evaluating the effectiveness of using this system in the on-line factory. Remaining errors are our sole responsibility. Grading Steps: In the grading stage, we present several steps that designers need to setting up the grading data and parameters in the system. The steps are given below. 1. Open files. 2. Set up the grading schedule. 3. Classify files. 4. Setting up grading parameters. 5. Carry out grading. 6. Check grading results. A customized shoe grading system for the footwear industry Peng,H.-L. Department of Mechanical Engineering, National Chung Cheng University, Chiayi County, Taiwan For further information For further information, please contact wolfcax@pouchen.com.wolfcax@pouchen.com Results This shoe grading system is implemented using Microsoft Visual C++ and OpenGL in Microsoft Windows environment. Fig 6 shows one example of 3D graded model generation by our customized system to grade shoe cases, in which we fix the contours of constrained surface, grading from size 9 to size 15. In the shoe design process, the shoe upper must be bonded with corresponding sole. When it is finished shown in Fig.7, we use the “replace curves” grading category to make the shoe upper and sole matched in our shoe grading process. The “replace curves” is to make the related surfaces or curves to be automatically placed into the new figure. The figure after grading (Fig. 7) shows that the boundary curves replaced are closed curves. In this case, the original boundary curve of a shoe sole must be extracted and placed via using the “replacement-original curves”. The new boundary curve of a shoe upper is placed by using the “replacement-new curves”. Table 1 and Figures 8a-e give another example of the results of five products of shoe using our grading system tested in a shoe factory. (5) H. J. Lamousin and W. N. Waggenspack (1994), NURBS-Based Free-Form Deformations, in: IEEE Computer Graphics and Applications, November, 59-65. (6) B. Guo and J. Menon (1996), Local shape control for free-form solids in exact CSG representation, in: Computer Aided-Design, Vol 28 (6/7), 483-493. (7) J. Y. Lee and K. Kim (1996), Geometric reasoning for knowledge-based parametric design using graph representation, in: Computer Aided Design, Vol 28 (10), 831-841. Literature cited (1) T. W. Sederberg and S. R. Parry (1986), Free form deformation of solid geometric models, in: Proc. SIGGRAPH 86, Vol. 20,August, 151-160. (2) S. Coquillart (1990), Extended free-form deformation: A sculpturing tool for 3D geometric modeling, in: Proc. SIGGRAPH 90, Vol. 24 (4), 87-196. (3) S. Coquillart and P. Jancene (1991), Animated free-form deformation: An interactive animation technique, in: Proc. SIGGRAPH 91, Vol 25 (4), 23-26. (4) W. M. Hsu, J. F. Hughes and H. Kaufman (1992), Direct manipulations of free- form deformations, in: Proc. SIGGRAPH 92, Vol 26 (2), 155-184. Figure 1 Grading procedure Figure 2 The top gauge line. Figure 3 Line for determining direction of grading along the z-axis Figure 5 The curve comprised of the boundary curves of the shank and full scale curve. Conclusions In this paper we presents a customized shoe grading system that allows designers to really reduce the time needed to grade shoe design. In this system we presents two approaches using in this shoe grading system to enables designers to fix the dimensions of specified shoe components and quickly grade the remaining components to achieve the desired range of shoe sizes. Toe springs, color dams, shanks, sidewall thickness, logos, decorations, and various geometric shapes and sizes can all be fixed and not be affected by the grading, resulting in perfectly matched components. Final, this paper presents a shoe grading system has been used for shoe industry. The benefit of the system is to save time and manufacturing costs and enhance the quality of a product. It is a quick and precise solution for all shoe grading needs. Figure 6 3D shoe model before grading Figure 7 Two 3D shoe models, red is before grading, blue is after grading Figure 8a Case 1 Figure 8b Case 2 Figure 8d Case 4 Figure 8c Case 3 Figure 8e Case 5 Table 1 Results of five cases of shoes using our grading system