User-adaptive sketch-based 3D CAD model retrieval

3D CAD models are an important digital resource in the manufacturing industry. 3D CAD model retrieval has become a key technology in product lifecycle management enabling the reuse of existing design data. In this paper, we propose a new method to retrieve 3D CAD models based on 2D pen-based sketch inputs. Sketching is a common and convenient method for communicating design intent during early stages of product design, e.g., conceptual design. However, converting sketched information into precise 3D engineering models is cumbersome, and much of this effort can be avoided by reuse of existing data. To achieve this purpose, we present a user-adaptive sketch-based retrieval method in this paper. The contributions of this work are twofold. Firstly, we propose a statistical measure for CAD model retrieval: the measure is based on sketch similarity and accounts for users’ drawing habits. Secondly, for 3D CAD models in the database, we propose a sketch generation pipeline that represents each 3D CAD model by a small yet sufficient set of sketches that are perceptually similar to human drawings. User studies and experiments that demonstrate the effectiveness of the proposed method in the design process are presented

Automatic design of fixture configurations: Representation and planning

Automation of process planning has been the focus of widespread research interest in manufacturing engineering. Of late, there have been efforts to integrate Computer Aided Design (CAD) and Computer Aided Manufacturing (CAM) by means of intelligent systems. These systems allow the designer to interactively design a part and use the information generated by the CAD module to automatically produce viable process plans down to the generation of the NC code for machining it. An important function of such process planners is the generation of fixturing schemes for the part. The function of fixture planning has a direct impact on the processing time and achievability of specified tolerances. This work is aimed towards development of a knowledge based fixture planner working in such an automated environment. The capability of modern machining centers to handle a large variety of part geometries directly implies the necessity of a large range of fixturing methodologies. An attempt has been made to formulate a generalized representation scheme for a variety of fixture elements using geometrical as well as functional properties. A methodology is described to build up assemblies of fixture elements complete with the workpiece to form fixturing schemes. An environment is described for developing a versatile fixture planner that can work in a closed loop automated process planning system. The proposed approach has been implemented as part of an existing automated integrated manufacturing system called the Quick Turnaround Cell. QTC presently uses a much simpler fixturing module, CLAMPS, that can handle only vise fixtures

Geometric techniques for efficient waste removal in LOM

A new CAPP system is proposed for the layered manufacturing technology of LOM (laminated object manufacturing). The traditional technique wastes much effort and time in the generation of rectangular grid patterns onto the exterior of the model to facilitate waste removal. In the proposed approach, several geometric properties of the model are exploited to dramatically reduce the waste removal grids. This, in turn, leads to reduced build time with no effect on the build quality. The proposed method uses parting planes similar to those used in mold design in regions external to the part's convex hull, and an octree decomposition in the remaining regions. An integrated CAPP system incorporating these ideas has been developed, and several example parts demonstrate the efficiencies that the system delivers

A Morphing-Based Surface Blending Operator for Footwear CAD

A new operator to interpolate a smooth surface between two given disjoint surfaces is presented in this paper. The method uses a modified form of shape morphing to generate interpolation points in the region of the gap. An energy minimization formulation is used to enhance transition smoothness. The work is motivated by a practical problem in footwear CAD, although the operator will find use in other applications. Some preliminary results from our implementation are presented. Copyright © 2004 by ASME

Gap Filling Using a Blend of Morphing and Extension with Application in Footwear Design

Several techniques for filling gaps or holes in a sculptured surface are known; perhaps the best studied include morphs and surface blending functions. Both of these techniques have several desirable properties, as some shortcomings. Here we develop a new operator that creates a holefilling surface by interpolating the outputs of morphing and blending functions. By controlling the interpolating function, more control can be exhibited over the resulting shape than is provided by either of the standard operations individually. Further, we also demonstrate a method to produce a `fair' surface (in the traditional, energy minimization sense) interpolating two gap-filling surfaces, created respectively by morphing and blending (or extension). The technique was motivated by problems encountered in the CAD of footwear

Traversing the machining graph of a pocket

A simple and linear-time algorithm is presented for solving the problem of traversing a machining graph with minimum retractions encountered in zigzag pocket machining and other applications. This algorithm finds a traversal of the machining graph of a general pocket P with Nh holes, such that the number of retractions in the traversal is no greater than OPT þ Nh þ Nr, where OPT is the (unknown) minimum number of retractions required by any algorithm and Nr is the number of reducible blocks in P (to be defined in the paper). When the step-over distance is small enough relative to the size of P, Nr becomes zero, and our result deviates from OPT by at most the number of holes in P,a significant improvement over the upper bound 5OPT þ 6Nh achieved [Proceedings of the Seventh ACM-SIAM Symposium on Discrete Algorithms, 1996; Algorithmica 2000 (26) 19]. In particular, if Nh is zero as well, i.e. when P has no holes, the proposed algorithm outputs an optimal solution. A novel computational modeling tool called block transition graph is introduced to formulate the traversal problem in a compact and concise form. Efficient algorithms are then presented for traversing this graph, which in turn gives rise to the major result