The Construction Of Virtual Measuring System For Spiral Surface Machining Precision Prediction Based On “improved Method Of Weighted Random Number” And Bp Neutral Network

Spiral surface is a kind of widely used complex curved surface in engineeringapplication, especially in high-end manufacturing equipment, precision instruments,machining tools and high precision national defense equipment. It is an importantworking face, demanding the precision higher and higher, and its machining precisiondirectly affects the performance of the products. But because of the complexity andparticularity of the spiral surface modeling, processing and testing is relativelydifficult, and it is hard to ensure machining precision, leading to long developmentcycle, high production cost and the low qualified rate. With the development ofmodern manufacturing technology, the virtual manufacturing technology offer a newkind of design and manufacture idea to manufacturing industry, greatly promoting thedevelopment of the manufacturing industry. However, along with the development ofvirtual manufacturing technology, virtual measuring technology is put forward to themachining accuracy prediction, it is the further improvement to virtual manufacturingtechnology. Therefore, this paper puts forward to construct virtual measuring systembased on the machining precision prediction for spiral surface workpieces, in order toshorten the development cycle, reduce processing cost, improve production efficiencyand processing precision.This paper mainly studies the following contents:(1) The parametric modeling of the3D spiral surface model is studied based on the"micro displacement matrix method". The3D spiral surface model is constructed withthe transverse profile line as tectonic line, according to the forming principle of thespiral surface. The "micro displacement matrix method" is put forward as the concreteconstruction method, and the3D spiral surface model is built with the technology ofVC++development platform and OpenGL graphics technology, providing the ideal3D entity model for the virtual testing system.(2) The mapping relationship between processing error and error sources and theadding method of error sources data are studied to the spiral surface based on the"improved method of weighted random number". It studies the process system which consists of machine, fixture, cutting tools and workpiece, and deeply analyzes eachpossible error source which influences machining precision of spiral surfaceworkpieces. It shows that the influence degree is different to different error sourceson the machining precision. So the "improved method of weighted random number"is put forward to deal with the mapping relationship between error sources andmachining precision, applying BP neural network to obtain the values of various errorsources to add weighted error data to the ideal3D model, providing a determinand3Dmodel for virtual measuring system.(3) Machining precision evaluation indexes of spiral surface and measurement planand error evaluation method of virtual measuring system are studied. The evaluationindexes are built up with the characteristic parameters which represent machiningprecision of spiral surface, that are the transverse profile line, spiral line, the averageradius of geometric shape, spiral angle, helical pitch and so on, after analyzing themethod of precision detection and error evaluation for the spiral surface workpiece.And through determining the design idea and function requirements of each modulein the virtual measuring system, the measurement plan and error evaluation methodswhich are applied to the virtual measuring system are studied.(4) The research on building virtual measuring system for machining precisionprediction of spiral surface workpieces. The virtual measuring system is built up torealize parametric building of3D model, real-time adding of error data, virtualmeasuring process, and result output based on object-oriented technology andmodularization design idea; it completes the function requirement of each modulethrough VC++development platform and OpenGL graphics library technology.(5) Experiment research for an instance machining of spiral surface workpiece.Experiment research could be carried out with cylindrical vertical milling cutterwhich is regarded as an example of spiral surface workpiece. The experimentalresults and the system measuring results are contrastively analyzed to verify theavailability and reliability of this system.