Research On Process Technology Of Aluminum-based Freeform Surface Optical Components

Free-form surface is a kind of optical elements with special surface structure.free-form surface has more degrees of freedom in design and can greatly improve the performance of the optical system compared with the traditional spherical surface and aspheric surface.It is difficult to manufacture monocrystalline silicon,glass and silicon carbide free-form surface mirrors because of their long processing cycle and difficult processing.The aluminum-based free-form surface mirror overcomes the shortcomings of other free-form surface mirrors and is easier to process on the basis of light weight,and it has a broad application prospect.At present,the single point diamond turning technology is mainly used to process the aluminum-based free-form surface,which has the advantage of one-time forming compared with the traditional polishing technology.In this paper,the servo turning technology of single-point diamond slow tool is studied,the influence of turning parameters on the surface quality of aluminum-based free-form surface is explored,the working procedure testing device is built,and the compensation machining is carried out combined with the test results and so can improve the surface shape accuracy.The single factor experimental method is used to study the influence of spindle speed,feed step and cutting depth on the turning roughness of aluminum-based free-form surface.On the basis of the better horizontal parameters obtained by the single factor experiment,the orthogonal experiment is carried out to find the best combination of horizontal parameters in the range of parameters.The optimal parameters are obtained as follows: spindle speed 240 rpm,feed step 0.007 mm,cutting depth 2 μm,and the optimal surface roughness Sa is 6.937 nm.The knife pattern data of single factor experiment and orthogonal experiment are analyzed,and the results show that there is a linear relationship between the residual amount of knife pattern and X-axis step.If the tool radius matches the appropriate X-axis step,the height and depth of the residual tool lines can be reduced.The study shows that the tool radius deviation is the main source of turning surface error of free surface.Combined with the turning path,according to the principle of generating the original data of the surface shape of the free-form surface and the turning point data of the lathe,this paper puts forward a method of using the contour datum as the detection of the machining process of the free-form surface to assist the compensation machining.According to the characteristics of turning point data,the program of specific point data extraction is designed,and the specific point curve in the test experiment is extracted successfully.Combined with the calibration principle of the workpiece in the installation process,the clamping part of the free-form surface is designed,and the process testing device is built.The compensation machining experiment of aspheric surface is carried out,and the deviation of machined aluminum-based aspheric surface is studied by orthogonal experiment,and the influence law of each parameter combination on the deviation of aspheric surface is obtained.Finally,the optimal parameter combination of aspheric compensation machining is obtained: spindle speed 200 rpm,feed step 0.005 mm,cutting depth 1.6 μm.The data points of the ideal contour reference curve and the detection contour reference curve of the free-form surface are processed,and the corresponding error curve is generated.The error is imported into Diffsys software,and the compensation machining experiment is carried out combined with the turning parameters of aspheric surface compensation machining.The peak-valley value evaluation method is used to calculate the error curve before and after compensation machining.The results show that the machining process detection method is suitable for free-form surface compensation machining at different rotational speeds,and the surface shape accuracy has been further improved.