Theoretical And Experimental Research On Free-form Surface Path Planning Of Ultra-precision Diamond Milling

Due to the high degree of freedom,freedom surfaces can effectively simplify the system structure and improve optical performance.At present,ultra-precision milling is one of the main methods to achieve their high-precision fabrication,and the surface quality of machined freeform surfaces can achieve nanometric roughness and sub-micrometer from accuracy.However,the curvatures of freeform surface are variable and thus leads to uneven surface residual and non-uniform surface quality.Hereby,this study investigates the influence of the curvatures and the gradients of freeform surface on the surface residuals during ultra-precision milling and innovatively proposes a path planning based on the equal residual area.The main contents are listed as follows:Firstly,two typical optical freeform surfaces,LED lens and virtual helmet reflex mirror,were adopted as the objects for ultra-precision milling.Correspondingly,a point-cloud mathematical model of the freeform lens was constructed by the non-imaging optical principle.A polynomial mathematical model of the freeform mirror was established based on imaging optical principle.Then,combined with the equal step arch,the relationship between the machining parameters(tool radius and step distance)and the surface residuals of freeform surfaces was analyzed in ultra-precision milling.The effect of the surface curvatures and the surface gradients on surface residuals was explored,and path planning with equal residual area was proposed for freeform surfaces to achieve their high-precision machining with uniform surface quality.Finally,by conducting the ultra-precision milling experiments for the typical freeform surfaces,the corresponding surface roughness parameters and the surface form accuracy were analyzed and a comparison with the traditional path planning was made.The results well verified the effectiveness of the proposed path planning since a uniform and consistent surface quality was achieved.This study focuses on the fabrication of freeform surfaces in ultra-precision milling.The relationship between the machining parameters and the surface residuals of freeform surfaces was revealed.For their high-quality manufacturing,a path planning was proposed based on equal residual area.This study is beneficial for the guidance of the high-quality fabrication of freeform surfaces.