2002 (Backfills for previous years) / DB reference years
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Author A.F. "Lex" Lennings, Delft University of Technology, P.O. Box 5029, 2600 GA Delft, The Netherlands; Tel 31-30-296-5957; Fax 31-30-296-2292; a.f.lennings@io.tudelft.nl
Source Rapid Prototyping & Manufacturing 2000
Abstract Where Rapid Prototyping can be defined as "A Process that Automatically creates a Physical Prototype from a 3D CAD-model, in a Short Time," two fundamentally different methods can be used for RP: 1. Removing material from a solid block until only the geometry of the model is left over. 2. Adding material into an empty space until the geometry of the model is completely filled. The first method refers to CNC machining, the second to various Layered Manufacturing Techniques (LMT). The development of LMT methods like stereolithography has created the growing demand for Rapid Prototyping. The advertised automatic translation from 3D CAD model to prototype using a laser operation resulted in the perception of an almost magical miracle machine. This perception has obscured the fact that most LMT machines are not so easy to use. On the other hand CNC machining has suffered from the notions that it was supposed to be too complicated to be called Rapid Prototyping, that it could not meet the 'Automatic' re quirement, and that it was too slow. This may have been true in the past, however, new developments in both software and machines have emerged that now have made CNC a very competitive process for Rapid Prototyping. Two available RP methods, LMT and CNC, do result. Each of them having specific strengths and weaknesses, each of them having a distinct application area within the total RP field. In this presentation we will compare both approaches and show the advantages and disadvantages of both using real life example projects: for LMT various High-end systems and Concept Modellers, for CNC software like Powermill and DeskProto with both low cost desktop and more expensive High Speed milling machines.
Main advantages of LMT include the following: almost absolute design freedom: any geometry can be produced; price independent of the complexity; total black-box process; for Concept Modellers even easy-to-use. Main advantages of CNC include the following: possible to start with a low investment (making in-house RP affordable); almost any material can be used; uncomplicated physical process (trouble-free); free choice of accuracy (and thus speed); large sized models are possible
As a result we will show that generally speaking for styling block models and concept models CNC-based RP is best, where for fully functional prototypes LMT based RP is the best option. This conclusion will again be illustrated using a number of real life examples. XX