| Freeform surfaces can be used in optical systems to achieve novel functions, improve performances, reduce size, and decrease the cost of various products. Therefore, optical freeform surfaces find applications in the fields of optics, medicine, fiber communication, life science, aerospace etc. Freeform optics has become the key element of quantitative light technology, which is becoming increasingly important in various fields. However, designers are reluctant to utilize freeform surfaces due to the complexity and uncertainty of their fabrication. Slow Slide Servo is a novel machining process capable of generating freeform optical surfaces or rotationally non-symmetric surfaces at high levels of accuracy. In order to achieve high accuracy optical complex surface by using Slow Tool Servo turning, the major research efforts include the following points.1. The theory of Slow Tool Servo turning and key technologies. A systematic introduction of the theory of Slow Tool Servo turning is first given by analyzing machine architecture and movements. By comparing with some other conventional technologies, the key technologies are high dynamic feed drive system, advanced interpolation technology and position control spindle technology. Then, the research emphasis on the performance of feed drive system and curve interpolation algorithm. Several aspects are discussed to improve the motion accuracy and control performance of feed drive system. PVT interpolation algorithm is introduced to Slow Tool Servo turning to overcome inherit drawback of conventional interpolation algorithm. In order to estimate the machining scope and accuracy, study on the machining capacity of Slow Tool Servo turning.2. The design theory of tool geometry parameters in ultra-precision Slow Tool Servo turning complex optical surface. Based on the requirements of slow tool servo, two types of tool are designed and analytic geometry models of cutting edge are built. A geometrical approach is introduced to formulate the relationship between tool tip and complex surface. By virtue of surface analytic method, the problem is solved efficiently, combined with the NURBS representation of complex surface. Experiments are carried out to validate solving algorithm. In addition, the relation models between tool shape and roughness, optical property and materials are built.3. The programming theory of tool path in ultra-precision Slow Tool Servo turning complex optical surface. In the basic design algorithm of complex optical surface slow tool servo turning, firstly study on the tool contact path design method and accuracy control skills of discrete process. Then, cutting edge compensation problem is considered. Two algorithms (normal direction compensation method and keeping X steady method) are proposed to avoid interfaces between surface and tool tip of zero rake angle. A tool path correct algorithm is developed to overcome over cutting and lack cutting due to non-zero rake angel. With regard to the calculate problem of tool path outer of surface region, space curve interpolation algorithm and surface continuation methods are proposed. In order to improve the manchining accuracy, error compensation algorithm is studied base on the tool path correction.4. The error model and simulation algorithm of Slow Tool Servo turning. Base on the discrete vector intersection, geometry simulation algorithm of slow tool servo turning is constructed. Then, major error sources and its transformations in complex surface turning are analyzed. An error model of slow tool servo turning is built base on multi-body theory. Experiments are carried out to validate simulation algorithm and error model.5. Finally, plentiful experiments are performed on a variety of complex optical surfaces including off-axis parabolic, array lenses, wave front correcting glass, spiral phase plate, continuous phase plate and so on. The successful machining results prove the validity and advantages of the proposed algorithms and the proposed process improvements.
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