Numerically controlled machining from three dimensional machine vision data




Bradley, Colin

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Prototyping is an essential step in the manufacture of many objects, both consumer and industrial. A fundamental step in this process is the definition of the three dimensional form of the object shape; for example, a designer's models created in clay or wood. A three dimensional vision system (range sensor) offers the advantage of speed in defining shapes compared to traditional tactile sensing. In this thesis, the viability of using range sensors is demonstrated by developing a rapid prototyping system comprised of a laser-based range sensor and software that creates a computer model of the object. One particularly important application of the computer model is for the generation of a control program, or toolpath, for a computer-numerically-controlled (CNC) machine tool. This is an important application in mold and die manufacture and mold manufacture for automobile components from full scale models. The computer model can also be incorporated into computer aided design and analysis programs. The most suitable vision system, for rapid prototyping applications, has been selected from a group of available sensors and integrated with a coordinate measuring machine that acts as a translation system. The range data produced have been utilised in a multi-patch surface modelling approach in order to model objects where many types of surface patches, such as quadric and free form, are blended together on one object. This technique has been demonstrated to provide accurate and smooth surface reconstructions that are suitable for generating CNC toolpaths. The viability of machining from multiple surface patch models has been demonstrated and, in addition, a new technique for the machining of free form surfaces developed. An alternative method for fully defining complex three dimensional shapes employing a rotary sensing of the object is also presented that permits the efficient generation of CNC machine toolpaths.



Machine-tools, Numerical control, Programming