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A novel approach of three-linear-axis ultra-precision grinding with wheel path generation, tool interference checking and profile compensation is proposed and systematically investigated for fabricating aspheric surfaces. The performance of the proposed techniques is evaluated by grinding an aspheric mould insert on bindless tungsten carbide. The experimental results demonstrate that the profile error can be reduced to 0.1 μm or a lower value in peak to valley (PV) after two compensation cycles. The on-machine measurement results show agreement with the off-machine measurement results when commercially available profilometers are employed. The study confirms the feasibility of the proposed wheel path determination method and the developed profile compensation approach. A mirror surface with roughness less than 8 nm in Sa is achieved.

With the widespread application of binderless tungsten carbide (WC) moulds, optical finish with ideal surface integrity is in great demand. Although Pre-heat laser assisted turning (Pre-LAT) is a potential method to achieve optical surface on hard and brittle materials, there is less investigation on the surface integrity, which needs to be studied for better understanding of Pre-LAT mechanism. In this article, the critical depth of no observed surface crack on binderless WC was experimentally studied with the laser pre-heat assistance. The subsurface damage is analyzed in detail, and the material removal mechanism during Pre-LAT is subsequently revealed.

Hard and brittle materials (HBMs) are promising materials for aerospace and astronomy applications, due to their excellent mechanical, optical, and chemical properties. However, they are difficult and costly to machine using conventional machining methods such as single point diamond turning. Laser assisted machining uses a focused laser beam to heat local areas of the workpiece and remove softened material from the ductile region, leaving high quality and crack-free surfaces. Over the past decades, the study of laser assisted machining of HBMs has been attracting progressively more interest from researchers in academia and industry. This paper serves as a state-of-the-art review with a particular focus on typical HBMs and their machining challenges; the mechanism of laser heating and thermal analysis; pre-heat and in-process-heat laser assisted machining methods; and optimizing the machining quality of laser assisted machining. The review also presents a perspective on future development trends for laser assisted machining technology.

This study proposes a novel surface modification method known as laser-assisted rolling, which aims to refine surface grains and enhance the machinability of brittle polycrystalline materials. This method establishes a foundation for achieving a crack-free and low-damage optical surface finish. Using binderless tungsten carbide as a case study, a systematic experimental investigation was carried out with a self-developed laser-assisted rolling system. The results show that the proposed method effectively refines surface grains by introducing dense defects. It also achieves a gradient grain size crystal structure and a residual compressive stress state without causing surface cracks. The formation and evolution mechanisms of the modified layer were comprehensively studied. Moreover, this novel method is expected to offer theoretical guidance for the surface modification of other brittle polycrystalline materials.

With the widespread application of various small aspheric optical components, high-precision manufacturing technology of forming molds is deeply demanded. However, the ultra-precision grinding technology of small-aperture aspheric mould is still undeveloped. An ultraprecision grinding technique called tilt axis grinding which is based on the grinding spindle is tilt with the axis of aspheric surface and profile error compensation of aspheric mould are studied. Through constructing geometric model of the tilt axis grinding, the tool path and the interference conditions were calculated. The form error was compensated with the data measured by profiler. An experimental test is conducted to grind an aspheric tungsten carbide mould of aperture 5 mm, and the profile accuracy is gradually improved from 0.652 μm to 89.3 nm in PV after two compensation cycles. The surface roughness is 10 nm in Ra.