Kinematics Analysis And Simulation-based Investigation On Ultra-precision Turning-milling Of Optical Freeform Surfaces

Optical freeform surfaces are a special kind of complex curved surfaces with nonrotational symmetry and irregular shape.They are widely used in modern optoelectronic systems,various optical systems and various types of optical lenses.This thesis presents some theoretical research based on discrete points for surface reconstruction in machining of freeform optics,puts forward the surface reconstruction algorithm based on NURBS theory and another tool path planning algorithm based on this algorithm.Applying them to a certain type of ultra-precision turning-milling machine tool for optical freeform surface,carries out the kinematics analysis for this machine tool and the algorithm research for error compensation.Finally,verifying the response of the machine tool and the surface error of workpieces by simulation.Since the complex surface morphology of optical freeform surface is difficult to express in a unified mathematical expression,the optical freeform surface designed by general optical design software is usually given in a form of discrete data.In order to obtain accurate surface morphology from the discrete data,this thesis further presents a method based on non-uniform rational B spline interpolation theory for surface reconstruction,and transforms it into a reconstruction algorithm program based on numerical solution through reasonable methods.On the basis of the reconstructed surface,using the non-uniform rational B spline interpolation and derivative theory to transform the analytic solution process into a numerical solution based on the traditional equal residual height method.In view of the characteristics of the optical freeform surface involved in this thesis,carries out the optimal design and the research of the constant scallop-height algorithm based on NURBS theory,then completes the tool path planning in the processing of workpiece.This thesis undertakes independent kinematics analysis for the fly-cutter milling and the fast-tool turning,deducing the geometric position relation and relative motion relation of each axis in the machining process,distributing the motion quantity of each axis and completing the motion quantity algorithm.In addition,aim at the overcut phenomenon in fly-cutter milling process,proposing a compensation algorithm based on non-uniform rational B spline theory.And this thesis discusses the allowance distribution between the fly-cutter milling and the fast-tool turning,and complete the allowance distribution algorithms.By establishing the structural model of machine tools in SolidWorks,then importing it into Adams to construct the kinematics simulation model.Using the real optical data to reconstruct freeform surface by the proposed reconstruction algorithm,the solves the motion quantity distribution of the axis.Finally,Importing the data into Adams to do some simulation analysis to make sure the theory and algorithm in this thesis is correct through the surface shape error and the response analysis of each axis.