Research On Polishing With Intersected Free-form Surfaces And Expert System

With the development of mold industry and its correlation industry, manyproducts' production and their renewal are taking the mold design, manufacture andrenewal as the premise. In the key part of the mold production, the precision workof surfaces is the most important ache in the manufacture. Moreover, because theproportion of the processing components which include free-form surfaces is moreand more higher, the request of the processing quality and the efficiency is moreand more higher. Because the unique technical content in the free-form surfaceprecision work, it has become a difficult question in the modern manufacturetechnology. But the corresponding handwork grinds is time-consuming, and alsothe efficiency is low, at the same time it's difficult to obtain the good shapeprecision and the surface quality. Especially, regarding the large-scale moldfree-form surface, its precision work is weak ache in the mold production andmanufacture, and even has become the bottleneck of restraining the development ofthe mold manufacturing industry.The domestic and foreign scholars positively are carrying on automaticallypolishing processing system development and the practical research in order toovercome question which exist low efficiency universal existence in the processingmold free curved surface. They have yielded many important results throughexploring new polish method and technology. Especially in the recent 20 years, aseries of automatically polishing method and system are successively constructedby the computer technology, for example Japan developed the numerical controlmiller, which can realize the three dimensional curved surface polishingautomatically in mold processing.It is very imperative for improving efficiency while guaranteed the moldfree-form surface finishing processing precision because mold finish man-houraccounts for the high proportion in the entire mold manufacture. In the specialobject of large-scale mold free-form surface, it has the contradiction of workingspace and the precision, the rigidity. Moreover, in very many situations the moldthe cavity surface is the irregular free-form surface. It brings very greatlytroublesome to the automated finishing processing tool path and feed because thesecurved surface shapes complex. As a result of the mold free curved surfacecomplexity, the polishing tool has the good self-regulating, namely the so-calledcompatibility. The polishing tool must change the tool type along with the freecurved surface processing outline. Based on this, the large-scale mold free curvedsurface highly effective finishing processing was still a world difficult problem inparticular regarding the mold free curved surface. So it is imperative for carryingon theory and technique research deeply in highly effective finishing processing.This article carries on based on the Jilin Province science and technology hallfund project "subdivision planning of the mold curved surface polishing in thevirtual machine tool". Some questions about mold free-form surface automaticallyhighly efficiency finish is carried on developing deeply on the basis of reading andanalysis the domestic and foreign literature material in the paper.The NURBS method is one kind of advanced modeling method forparameterized curve and surface which has the characteristic of stable computationand high speed. In this topic, the NURBS description mold free-form surface isadopting. Base on the NURBS method, subdivision planning method of artificiallypolishing process is analyzed and free-form surface boundary as well assubdivision planning algorithm is put forward base on curvature according to thecomputer graph information and the NURBS curved surface construction feather.The purpose of subdivision is enhancing the polishing efficiency as far as possibleon the basis of the polishing quality being reached. Considering the surfacepolishing automation, the procedure realization process for boundary's distilling isput forward (see the figure 2.4).The contrast experiment in allusion to concrete object (figure 1) is carried onin order to validating the effectiveness to polishing in form of subdivision.This mold free-form surface is divided into two groups according as thesymmetry axis: The region 1 is group A who's processing is the traditional method;The region 2, 3 and 4 is formed to group B who's processing is the combinationmethod. Using the subdivision planning method the group B is divided into threesurface pieces in the two-dimensional parameter field: The area surface 2 is thebiggish change curvature area, which takes the 8cm balls grinding wheel;the areasurface 3 takes the 16cm balls grinding wheel;the area surface 4 is the cylinder,which takes the 10cm wimble grinding wheel. In order to contrast, the region 1takes the 8cm balls grinding wheels. Each surface remains the same rudimentalheight to guarantee that its precision is consistent.The result shows that the time used subdivision rough grinds is less than thatof subdivision polishing in the situation of surface roughness basic maintenancestable. Polishing efficiency enhances 18.63%, and indicates subdivision polishingcan enhance the efficiency truly.Boundary between surfaces which is produced based on subdivision planningalgorithm has the irregularity, and even "not smooth". Therefore, it is necessary tosmooth it.There are many ways to smooth curve, and non-smooth boundary problem existsafter the mold free-form surface piece processing, it has carried on processing based on thediscrete energy method of point to process the fair of the pieces. It has established fairpolishing model and has produced its algorithm step. Through analyzing theconcrete example (Figure 2), it indicated that the fair polishing model based on theseparate energy method is correct, and it can realize the fair polishing between thecurved surface pieces.Fig 2 pre and post-smooth NURBS curveThe figure 2 shows that the NURBS curve not only has got many meliorates,but has guaranteed that its curvature change is relatively well-proportioned in theprocess of smoothing. At the same time, the result proves the rationality andvalidity of separate energy algorithm based on points. Applying this algorithm in thesubdivision polishing, the efficiency of the entire work piece will enhance greatly.At present, being short of the polishing knowledge and the technicalsystematization, seriously effect to the automation and affection for the entirepolishing process, constructing the expert system becomes a development tendencybased on science analysis on polishing knowledge and technology.Through analyzing the polishing skill of the skilled grinding worker, polishingprocessing and polishing theories, it has constructed the base frame of expertsystem of the integrated force sensor mold free-form surface subdivision polishing.Unifying the VC technology, the knowledge base design and its management,inference engine and its inference algorithm is completed.The realization of the expert system is on the foundation of computer andpolishing knowledge. The expert system for the free-form surface subdivisionpolishing uses the newest object-oriented software development technology and theVC++6.0 integrated development environment who's function is so formidable,and unifies the OpenGL image display technology and SQL Server 2,000 dataexploitation. Through reasonable plan to the system structure, it not only enhancesthe system development speed and the programming efficiency greatly, but ishelpful to the further expansion and consummation for the system. In this topic, themain interface is given, on the foundation its main function modules are introduced,and design conception for each module is put forward.