Search Results (6)

Sapphire crystals, owing to their outstanding mechanical and optical properties, which are widely used in advanced optics, microelectronic devices, and medical instruments. The manufacturing precision of sapphire optical components critically affects the performance of advanced optical systems. However, the extremely high hardness and low fracture toughness of sapphire make it a typical hard-to-machine material, prone to brittle surface fractures and subsurface damage during material removal. Improving the machinability of sapphire remains a pressing challenge in advanced manufacturing. In this study, surface modification and enhanced ductility of C-plane sapphire were achieved via ion implantation, and the machinability of the modified sapphire was further improved through laser-assisted diamond machining (LADM). Monte Carlo simulations were employed to investigate the interaction mechanisms between incident ions and the target material. Based on the simulation results, phosphorus ion implantation experiments were conducted, and transmission electron microscopy observation was used to characterize the microstructural evolution of the modified layer, while the optical properties of the samples before and after modification were analyzed. Finally, groove cutting experiments verified the enhancement in ductile machinability of the modified sapphire under LADM. At a laser power of 16 W, the ductile–brittle transition depth of the modified sapphire increased to 450.67 nm, representing a 51.57% improvement over conventional cutting. The findings of this study provide valuable insights for improving the ductile machining performance of hard and brittle materials. Full article

Glass-ceramic optical components are extensively employed in advanced optical systems. The high-hardness and low-fracture toughness of glass-ceramics make it prone to cracks and subsurface damage during conventional cutting. The laser-assisted diamond cutting method can significantly improve the nano-cutting performance of glass-ceramics by locally heating and softening the material. However, its dynamic removal mechanisms remain unclear. The coupling mechanisms between the laser thermal field and the mechanical response of the material require further investigation. This study aims to reveal the dynamic removal mechanisms of glass-ceramics under laser-assisted nanoscale cutting conditions through numerical simulations and systematic experiments. It includes a systematic analysis of the effects of laser heating on chip morphology, temperature fields, stress fields, and cutting forces using a laser-assisted nano-cutting model. Additionally, through nanoscale taper cutting experiments, this study quantifies the enhancement effect of laser power on the critical depth of no observed surface cracks (NOSC). Finally, subsurface integrity results elucidate the mechanisms through which laser assistance inhibits crack propagation. The findings will provide theoretical support for optimizing laser-assisted cutting parameters and achieving high-quality machining of glass-ceramics. Full article

WC–Co cemented carbide has been widely used as machining tool material due to its good mechanical properties. Grinding is an important process in the manufacture of cemented carbide tools. When grinding tools, there are problems such as excessive grinding force, small chip space, and poor lubrication and cooling performance, which in turn contribute to surface defects such as burrs, burns, and even edge damage such as edge chipping. These problems constrain the use of carbide tools, so that the cutting force is unstable and the machining surface quality is poor when the tool is in service. In this paper, straight-line and wavy-texture patterns were designed and formed on the surface of WC–Co tools using a picosecond laser. Grinding experiments were conducted on the ablated tool using a resin-bonded diamond wheel, and surface morphology, roughness, grinding force, and cutting edge quality were evaluated. Finally, turning experiments were conducted to compare the cutting performance of the tools after conventional and laser-assisted grinding. The experimental results showed that the tools with wavy texture showed superior surface and cutting edge quality, with 53.7% and 51.2% reduction in normal and tangential grinding forces, respectively, and 66.6% maximum reduction in edge chipping for the wavy textured tools. Therefore, this study not only reveals the advantages of laser-assisted grinding in machining WC–Co cutting tools, but also provides a valuable theoretical basis for realizing high-efficiency and low-loss tool machining. Full article

Polycrystalline ZnS is a typical infrared optical material. It is widely used in advanced optical systems due to its excellent optical properties. The machining accuracy of polycrystalline ZnS optical elements must satisfy the requirements of high-performance system development. However, the soft and brittle nature of the material poses a challenge for high-quality and efficient machining. In recent years, in situ laser-assisted diamond cutting has been proven to be an effective method for ultra-precision cutting of brittle materials. In this study, the mechanism of in situ laser-assisted cutting on ultra-precision cutting machinability enhancement of ZnS was investigated. Firstly, the physical properties of ZnS were characterized by high-temperature nanoindentation experiments. The result revealed an increase in ductile machinability of ZnS due to plastic deformation and a decrease in microhardness and Young’s modulus at high temperatures. It provided a fundamental theory for the ductile–brittle transition of ZnS. Subsequently, a series of diamond-cutting experiments were carried out to study the removal mechanism of ZnS during in situ laser-assisted cutting. It was found that the mass damage initiation depth groove generated by in situ laser-assisted cutting increased by 57.99% compared to the groove generated by ordinary cutting. It was found that micron-sized pits were suppressed under in situ laser-assisted cutting. The main damage form of HIP-ZnS was changed from flake spalling and pits to radial cleavage cracks. Additionally, the laser can suppress the removal mode difference of different grain crystallographic and ensure the ductile region processing. Finally, planning cutting experiments were carried out to verify that a smooth and uniform surface with Sa of 3.607 nm was achieved at a laser power of 20 W, which was 73.58% better than normal cutting. The main components of roughness were grain boundary steps and submicron pit. This study provides a promising method for ultra-precision cutting of ZnS. Full article

The laser-assisted diamond turning (LADT) method can effectively improve the machinability of hard and brittle materials based on the laser heating effect, resulting in prolonged diamond tool life and better surface integrity. However, due to the incomplete absorption of laser beam energy within the workpiece cutting zone, simultaneous heating of the tool holder occurs, resulting in a structural thermal expansion that affects the workpiece form accuracy. In this article, the form accuracy of a LADT-machined workpiece was systematically studied. Accurate calculations of the tool shank and tool holder thermal fields and thermal expansion were performed using thermodynamic coupled finite element analysis. In addition, the LADT tool path was precisely pre-compensated by taking into account the structure expansion. The experimental results demonstrate that the form accuracy can be significantly improved with a pre-compensated tool path, which provides crucial technical support for achieving a high-precision finish on optical elements using the LADT method. Full article

In this study, silicon nitride milling experiments are carried out using Polycrystalline Diamond (PCD) end mill rods under unassisted, hybrid-assisted (combination of laser assisted and three axis ultrasound), and laser-assisted systems to examine the cutting performance and machined surface quality of different cutting tools. The best combination of process parameters for silicon nitride composites milling are obtained using the Taguchi method. The effects of spindle speed, radial depth of cut, and feed rate on surface roughness, cutting force, edge topography, and tool wear of silicon nitride surfaces are investigated. The results reveal that hybrid-assisted produces superior surface roughness, longer tool life, fewer machining defects, and lower cutting force than unassisted. Best results of triaxial ultrasonic-assisted combined with laser on cutting performance are achieved as the ultrasonic waves help to vibrate the cutting tool and workpiece simultaneously, which helps to effectively remove chips and lowers the cutting force. When compared to unassisted milling, laser-assisted and hybrid-assisted milling improve total average surface roughness by 42% and 66%, and total cutting forces by 26% and 46%, respectively. The best processing parameters obtained in this study are high spindle speed (12,000 rpm), low feed rate (500 mm/min), and low cutting depth (0.02 mm). Full article