Rotary symmetric error (RSE) is a typical type of surface machining errors for precision components, related to the relative tool-workpiece movements adopted. A quick removal method of the workpiece surface RSE using a fluid jet polishing (FJP) process, in which the tool nozzle and workpiece move relatively as in an end-face turning process, is presented. Efficient improvement in the workpiece surface form accuracy was achieved using a relatively simple device. Two methods to extract the RSE from the measured surface error curves, i.e., the average and minimum methods, are introduced and compared. The influence of the local jet rotation radius on the removal function of FJP was investigated experimentally. The algorithm for solving the dwell time curve in two-dimensional FJP process was derived. Deterministic FJP experiments were conducted to remove the RSE by means of the end-face turning movement. Experimental results show that the proportion of the RSE to the overall surface error on most workpieces was reduced from >60% to <20%, whereas the volume of the nonrotary symmetric error (non-RSE) fluctuates slightly before and after the FJP process. Using the average RSE extraction method and combining it with the zero-phase filtering method to filter the dwell time can effectively reduce the frequency of residual circular error in the polishing surface and avoid increasing of power spectral density in the mid-high frequency after polishing.
During the deterministic processing, dwell time map is the precondition to achieve the high precision surface. It is very important to obtain V-like shape removal function for the dwell time computation when using the numerical iteration method. As one of the ultra-precision polishing method, Fluid jet polishing (FJP) has been used widely in optical fabrication. But the shape of removal function of existing vertical jet polishing is W like. So, eccentric rotation jet device was usually used to correct the shape of remove function from W-like to V-like shape. In this paper, we put forward a concept of rotary function, and its can take the place of eccentric rotary device to achieve faster solve of dwell time and make the equipment structure simplify. We also put forward the layer by layer dwell time computation method and efficiently avoid the convergence failure.
High efficiency machining of large precision optical surfaces is a challenging task for researchers and engineers worldwide. The higher form accuracy and lower subsurface damage helps to significantly reduce the cycle time for the following polishing process, save the cost of production, and provide a strong enabling technology to support the large telescope and laser energy fusion projects. In this paper, employing an Infeed Grinding (IG) mode with a rotary table and a cup wheel, a multi stage grinding process chain, as well as precision compensation technology, a Φ300mm diameter plano mirror is ground by the Schneider Surfacing Center SCG 600 that delivers a new level of quality and accuracy when grinding such large flats. Results show a PV form error of Pt<2 μm, the surface roughness Ra<30 nm and Rz<180 nm, with subsurface damage <20 μm, and a material removal rates of up to 383.2 mm3/s.