Polycrystalline ZnSe ceramics, an extreme difficult to machine material due to the inherent nature low hardness, low fracture toughness, and high brittleness, has been wildly used in the laser and infrared optics manufacturing field. However, the surface defects are inclined to nucleation and propagation through conventional single point diamond turning, the hybrid technology micro-laser-assisted machining (μ-LAM) has been proposed to combine the laser-assisted machining and ultra-precision single point diamond turning, which demonstrated the potential in improving the machining efficiency and surface integrity. In the study, comparative experiments have been conducted to verify the feasibility of μ-LAM on ZnSe ceramics. Furthermore, orthogonal experiments have been carried out to investigate the effect of machining parameters and laser parameters on surface quality and the optimum parameters subjected to the μ-LAM of ZnSe ceramics.
Single crystal silicon (sc-Si) is a typical infrared optical material with good heat resistance and high infrared transmittance which is widely used in infrared optical systems , aerospace and other fields. However, due to the higher hardness and lower fracture toughness of this material, brittle fracture is very prone to occur during single-point diamond machining, resulting in poor surface finish and roughness. Hence, like ceramics, and composites, the machining of this alloy is considered as difficult-to-machining materials. Micro-laser-assisted machining (μ-LAM) method has become a promising solution in recent years to lessen cutting stress when materials that are considered difficult-to-machining, such as sc-Si and ZnSe are employed. This paper investigated the influence of input variables of μ-LAM on the machinability aspect of the sc-Si. The influence of cutting parameters on surface roughness in LAM is studied by orthogonal experiment, and optimal processing conditions are obtained. The second-order regression model of process parameters and surface roughness was established by response surface method. The results show that the change of cutting depth had little effect on surface roughness, the spindle speed and feed speed were main factors affecting the surface roughness. According to the 3D response surface, the interaction between different factors had a significant effect on surface roughness. The optimal combination of process conditions were a spindle speed of 4000rpm, a feed speed of 2mm/min and a cutting depth of 5μm.
Due to the hard and brittle nature for optical materials, such as single crystal silicon, sapphire and fused silica, it is still difficult to machine those materials directly. Laser assisted turning (LAT) is an advanced method for machining the optical materials, which improve the local cutting performance by softening the workpiece. It has been demonstrated the great potential in LAT process for improving the surface quality and reducing the cutting force. This study reviewed the recent application of LAT in these materials. The material removal mechanisms was also analyzed and summarized. According to the experimental results, the machining efficiency and tool life were significantly increased. Finally, the development trend of LAT is prospected.
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