Study On The NC Programming System In Multi-Axis Free-Form Surface Machining With High-Precision And High-Efficiency

Currently, the NC program, considered as one of the measures that can mostobviously exert its benefit in the system of CAD/CAPP/CAM, has got an extensiveattention both in our country and foreign countries for its important role in such aspectsas achieving the automation of design and machining, improving the machiningprecision and quality, shortening the time-to-market of new product and so on. Based onthe geometry feature of the free-form surface, the problem is researched about how toimprove the machining efficiency on the condition of ensuring the machining precision. Aimed at the high precision and high efficiency, on the basis of thorough analysisof the key technical problems which the system has to solve, a more perfect NCsystem's frame aimed at the complex NURBS surface multi-axis machining, enjoyingself-adaptation capacity while selecting the processing parameters and perfect cutters'control capacity in the aspect of collision-free and ensuring high calculating precisionwhile computing the row spacing was established. On the basis of analysis of the relation between the cutters'sizes and the machiningefficiency, the scheme for maximizing the machining efficiency was put forward toselect the cutter's category and size. Based on the selecting arithmetic of all types ofcolliding characteristic points which was put forward in this thesis, some selected pointswere analyzed and the maximum cutters'sizes free from collision during the wholemachining of the complex surface were got quickly and effectively. In addition, withrespect to the large-sized complex surface, the cutter-selecting arithmetic formulti-cutter was designed, which improved the whole machining efficiency of thecomplex surface. This arithmetic also implemented the partition of the machining areain accordance with the selected cutters. On the basis of a systematic analysis about how to obtain the cutter's located-pointdata from the cutter contact points, a collision-free control arithmetic of selecting thecolliding characteristic points and the arithmetic of the partition of the surface was putforward. Based on the bounding box principle and the visible cone principle, thecollision between the cutter and the surface was avoided during each stage. In addition,during the process of avoiding collision between the cutters and the complex surface,the machining form was also considered, and on the precondition of no collisionbetween the cutters and the complex surface, the cutting state of the cutter was III英文摘要optimized and the machining efficiencywas improved. On the basis of a thorough study of the original cause of the error duringcalculating the row racing, a row-racing calculating arithmetic enjoying higherefficiency and high precision was put forward. The arithmetic was based on thecircular-spline technology, respectively realized the high-precision approach betweenthe circular arc and the complex surface's normal transversal and that the projectioncurve of the blade. According to the characteristics that it's easy to get the offset curvefrom a circular curve, a row-spacing calculating arithmetic free from calculating errorwas designed. In addition, to solve the problem that the error caused during dispersingthe cutter's path would directly affect the scallop height between neighboring paths, aself-adapting control arithmetic was put forward, which would ensure the machiningprecision of the complex surface. Based on the comprehensive consideration of the cutter's size, the servoperformance of the machine, the geometry characteristic of the cutter's path and themachining quality of the surface, a reasonable arithmetic was put forward to select thecutter's feeding speed. Besides, the original cause that the feeding speed would fluctuatewhile moving along the machining path, an error-compensating arithmetic based on thenumeric approaching principle was put forward, which can ensure...