Binghai Lv

Experimental study on aspheric surface machining using elastic deformation moulding method

A novel aspheric surface machining, elastic deformation moulding method is proposed. Based on the linear elasticity of brittle optical materials, the elastic deformation moulding method can convert complicate aspheric surface machining to simply flat surface machining. The basic principle of the new method is described, a concave parabolic mould made of micro-porous ceramic is designed and machined, and an elastic deformation moulding machining system based on vacuum absorption is built. A machining experiment is then carried out. After 45 min lapping and 90 min polishing, a parabolic surface with form accuracy less than P-V 1.8 μm (within the radius of 9 mm) and a smooth surface with roughness Ra 7 nm is obtained, and the reasons of the machining form error generation are analysed. Experimental results show that the proposed aspheric surface machining method can achieve high machining quality with high efficiency.

Analysis of the kinematic model for cylindrical parts in double-sided lapping process

The method of machining cylindrical parts with double-sided lapping through a planet mechanism is discussed in this paper, and the cylindrical parts trace equation is set up by using the coordinate transformation, then simulate the contour and distribution of the trace by using MATLAB. From this model, we found out that the trace of the double-sided lapping is a group of cycloids and the cycloids distribution scope and distribution state have a direct relationship with the drive ratio of fixture. It is found that the track curves are concentric circles with changing time, i.e. when m = 0.3 or m = 1, the inhomogeneity of track curves are increased with changing time when m = 2, The trace curves of lapping are dense and uniform when m = –2. Based on this, placing the cylindrical parts in the middle area of the cycloids when m = –2 is favourable to lapping uniformly.

Numerical and experimental study of thickness effect on deflection of glass plate in elastic deformation machining method

Elastic deformation machining is a fabrication method that uses the elastic deformation properties of materials to make a desired surface form. Coupled with plane lapping machining process, the fabrication method is suitable for machining large aspheric surfaces. In this method, the workpiece is deformed under load and the bottom side of the workpiece is lapped to a flat surface. When the load is released, the bottom surface of the workpiece will be shaped into an aspheric shape. However, the thickness of workpiece is changed in the lapping process while the load remains unchanged. Therefore, the form accuracy of workpiece will increase with desired form surface. The effect of vacuum pressure on deflection of glass plate which changed thickness in lapping process is predicted in this study based on the numerical finite element analysis (FEA) results to determine vacuum pressure values which correspond with changed thickness of workpiece in the experimental process. The study indicates that, the effect of ...

Influence of Lapping Residual Stress on Machining Precision of Elastic Deformation Molding Method

Elastic deformation molding method is a newly developed aspheric machining technology which can convert complex aspherical surface machining to simple flat surface machining. The residual stress induced in lapping process of elastic deformation molding method has significant influence on machining precision. In this paper, the influence of residual stress induced lapping process on machining accuracy is analyzed and discussed through experiment. An experiment with elimination of residual stress is carried out. The machining result shows that distortion amount has reduced form 2 μm to 0.8 μm, which means the residual stress can be effectively eliminated. A machining form accuracy of P-V 0.56 μm is obtained.