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The surface quality and subsurface damage (SSD) distribution achieved with a fine-grained grinding wheel under different depth-of-cut and cutting speed is experimentally studied. The ground surface roughness (SR) is investigated via white light interferometry and expressed in terms of four typical roughness values (PV, RMS, Rz, and Ra). The SSD is characterized by the magnetorheological finishing (MRF) spot method and transmission electron microscopy. The results show that brittle-ductile surfaces and ductile-like surfaces are generated during ultra-precision grinding. Largely due to plastic flow removal, fracture defects such as fractured pits and grinding streaks on the ground surface can be mitigated. Instead, a ductile-like surface covered with grinding streaks is found. When the depth-of-cut decreases from 4 to 1 μm, the SR and SSD depth decreases from PV 1.34 μm, Ra 15.23 nm, Rz 0.94 μm, RMS 22.24 nm, and SSD 6.1 μm to PV 0.51 μm, Ra 5.07 nm, Rz 0.24 μm, RMS 6.70 nm, and SSD 1.2 μm. In addition, when the cutting speed increases from 3.9 to 23.4 m/s, the SR and SSD depth decreases from PV 1.03 μm, Ra 15.01 nm, Rz 0.82 μm, RMS 21.43 nm, and SSD 5.6 μm to PV 0.12 μm, Ra 3.17 nm, Rz 0.07 μm, RMS 4.65 nm, and SSD 0.003 μm. Moreover, the material removal mechanism under different grinding parameters is revealed by calculating undeformed chip thickness, and the mechanism of surface morphology and subsurface crack produced in brittle-ductile mode is analyzed. A linear relationship between the SR and SSD depth is in accord with the formula SSD = 0.41Ra−0.68 for brittle-ductile surfaces. [ABSTRACT FROM AUTHOR]

Atmosphere plasma etching methods have been applied to the machining of optics. However, due to the high chemical stability and inertness of silicon carbide (SiC) ceramics, it seems difficult to improve the material removal rate (MRR) for conventional etching methods. We have found MRR will be significantly improved while arc forms between the inductively coupled plasma and SiC ceramic surface. This etching method is called arc-enhanced plasma machining (AEPM) technology. Arc-enhanced plasma (AEP) is represented as the secondary of a high-frequency transformer considering capacitive coupling in this paper. Radio frequency (RF) voltage in AEP is measured. The RF voltage of plasma is extremely high to form arc when plasma is close to the SiC ceramic surface. The measurement results of RF voltage at the metal-plasma interface show that the arc formation is related to the distance between source jet and workpiece ( D ). When D is small, a nonconductive layer of cooled argon forms over the workpiece surface, preventing arcing. Trenches are etched on SiC ceramic surface with different D , finding that the MRR is improved under the arcing action and the optimal D is obtained. [ABSTRACT FROM AUTHOR]

Unlike traditional machinery manufacturing generally using simple features of workpiece as the alignment reference, optical manufacturing, which prioritizes shape tolerances of the machining surface over position tolerances between workpiece geometry features, chooses the machining surface itself as the alignment reference. Thus, the manual alignment of workpiece in optical manufacturing could be very time-consuming when the machining surface is aspheric. Workpiece localization technology is able to automate the workpiece alignment and improve its efficiency. However, there are no relevant reports about application of this technology in the field of optical manufacturing. In this work, the workpiece localization problem for aspheric surface in magnetorheological finishing (MRF) is investigated from aspects of measurement and algorithm. The probe radius error is compensated by applying the polynomial fitting method. A new localization algorithm is proposed in order to improve the computational efficiency for the localization of aspheric surface. Simulation and experiment results verify the validity of the proposed methods. The accurate and efficient workpiece localization in MRF has been achieved and applied in real application which proves its practicability. [ABSTRACT FROM AUTHOR]

According to forming principle of line contact spherical generating by cup-shaped wheel, the sources of grinding error were analyzed, and a new method for error analysis and compensation was proposed in this paper. In a certain grinding condition, the grinding error caused by the pose errors between wheel and workpiece was simulated, the corresponding curve fitting of grinding error was carried out, and an appropriate parametric model was established. If the actual grinding error is known, the model can identify the corresponding pose error as well as compensate the grinding error. The simulation and experiment processes of compensation validate the efficient and workability of parametric model, and improve the grinding precision. [ABSTRACT FROM AUTHOR]

When fabricating optical cantilever parts with single-point diamond turning (SPDT) technique, chatter phenomenon happens and degenerates the surface quality. This paper studies the chatter phenomenon and proposes a scheme to solve the problem. A kind of viscoelastic material is presented as the auxiliary supporter under the vibration location of optical cantilever parts to suppress chatter. Mirror surfaces can be generated and surface shape can be maintained after uninstalling the supporter because of the special features of viscoelastic material which acts like solid to enhance the rigidity of the cantilevers when cutting forces act on it and acts like liquid to avoid distortion of the surface shape during setting and unsetting the supporter. The effect of the viscoelastic material is discussed by virtue of finite element simulation on the basis of elasticity theory. Cutting experiments are carried out and the cutting forces as well as the surface quality with and without viscoelastic supporter are compared. The results show that chatter is suppressed effectively by using viscoelastic supporter, and surface roughness average (Ra) of around 5 nm is obtained on the whole surface with no obvious distortion on machined surface shape. [ABSTRACT FROM AUTHOR]