THE SHAPE OF A FLEXIBLE BLADE FOR FREE-FORM LAYERED MANUFACTURING OF PLASTIC FOAM OBJECTS

The need for rapid, cost-effective and finish-less manufacturing of large sized, sculptured, physical models from various soft materials is increasing in several fields. For objects fabricated from plastic foams an advantageous approach is free-form, thick-layered manufacturing. Although it is technologically demanding, to achieve the best results (a) computer definition of the geometry has to be accurate, (b) the geometric model has to be directly sliced, (c) higher order approximation of the nominal shape is necessary, and (d) a quasi-free-form working out of the front surfaces of the layers is needed. The authors have developed the mathematical and/or technological fundamentals and process of free-form cutting based on heated flexible blades. The shape and the relative positions of the flexible blade are controlled continually as needed by the normal curvatures of the front faces of the layers. The paper elaborates on the computation methods for physically-based and geometrically-based modeling of flexible blades. The algorithms for approximating curve generation and curve matching are also presented. The paper extends to some of the most important aspects of the global thick-layered fabrication process. INTRODUCTION AND PROBLEM STATEMENT Large sized, free-form physical models of various soft materials (e.g., layers of plastic foam, paper, plywood, etc.) are extensively used in several application fields. In industrial design, for instance, foam models are used to evaluate the shape and aesthetics of consumer durables, e.g., automobiles, household appliances (de Jager, P., 1997). In the entertainment industry, extra-sized human and animal mannequins and maquettes are made of plastics. Easy to manufacture and to finish plastic models are also used in engineering for simulation of aerodynamic and hydrodynamic behaviors of objects. In the packaging industry plastic means are applied to protect other more valuable objects from damage. But they are also used as decoration in the advertisement industry, as scenery in movie film making, stage setting in theaters, and so forth. The physical models/prototypes used in these applications have to be adequate for certain functional, aesthetic and economic requirements beyond manufacturing aspects. Thus, the need for effective and precise layered manufacturing does exist (Vergeest, J. S. M., Broek, J. J., Schierbeek, B. B., Tangelder, J. W. H., 1991). Physical prototypes can be produced nowadays by several manufacturing processes (Marsan, A. and Dutta, D., 1997). A classification of the most widely used prototyping technologies are shown in Figure 1. Decremental processes form the shape of objects by material removal. Typical manufacturing technology is high-speed milling with ball-end cutter (Tangelder, J. W. H., Vergeest, J. S. M. and Overmars, M. H., 1998). Incremental processes are typically based on deposition technologies and can be further classified based on dimensionality of deposition. A hybrid process is a specific