Physical concept modeling (PCM) is a rapidly maturing subfield of rapid prototyping. It aims at producing physically editable materialized models to support functional and shape synthesis during conceptual design. PCM raises unprecedented design methodological and technological issues. Numerous technological problems stem from (i) the free-form shape and large size of the fabricated objects, (ii) the required surface finish and decoration, (iii) the need for on-line manufacturing with short production time and minimal costs, and (iv) the requested trade-off in terms of the efforts and the improvement of the product. The FF-TLOM technology has been earlier proposed by the research team of the authors to solve these problems. It permits to convert early CAD models into a materialized model even for large-sized objects that cannot be fabricated by conventional layer depositioning or high-speed milling. This paper presents algorithms for preliminary morphological segmentation of the CAD model to improve the performance characteristics of the FF-TLOM process. The authors deal with only free-form objects without zero- and first- order shape singularities. The segmentation algorithms are based on normal vector analysis and feature point recognition. Pre-defined segmentation features are used to guide the process. The actual extent of the segments is found by dimensional and geometric analyses that are supported by a segmentation feature graph. The developed algorithms are able to define the segments in such a way that at least one planar surface is provided for the further orthogonal slicing. The segments are sliced into layers of standard thickness based on a higher order approximation of the free-form shapes.
展开▼
