No abstract

a b s t r a c tSingle point diamond turning (SPDT) is coupled with the micro-laser assisted machining (-LAM) technique to machine silicon (111). The -LAM system is used to preferentially heat and thermally soften the work piece material in contact with a diamond cutting tool. Cutting fluid, odorless mineral spirits (OMS), is used to decrease tool wear and improve the surface quality. An IR continuous wave (CW) fiber laser, wavelength of 1070 nm and max power of 100 W with a minimum beam diameter of 10 m, is used in this investigation. Various machining parameters such as laser power, cross feed rate and tool rake angle were experimented and the resultant surface finish was analyzed. Results show that an optical quality surface finish can be obtained using the -LAM technique.

& Quartz (fused silica) is one of the advanced engineered ceramic materials designed to operate in extreme environments. The mechanics of material removal in glass (Quartz) can be classified into two categories; brittle fracture and ductile plastic deformation. Good optical quality surfaces can be achieved by removing the material in a ductile manner. The strength, hardness and fracture toughness of the workpiece material are the governing factors that control the extent of brittle fracture. The main goal of the subject research is to improve the surface quality of Quartz to be used as an optic device (mirrors and windows) via single point diamond turning (SPDT). Sub-surface damage analysis was carried out on the machined sample using Scanning Acoustic Microscopy (SAcM). Surface roughness (R a ) values of less than 45 nm without sub surface damage were obtained. Tool wear was also investigated.

Silicon carbide (SiC) is one of the advanced engineered ceramics materials designed to operate in extreme environments. One of the main reasons for the choice of this material is due to its excellent electrical, mechanical and optical properties that benefit the semiconductor, MEMS and optoelectronic industry respectively. Manufacture of this material is extremely challenging due to its high hardness, brittle characteristics and poor machinability. Severe fracture can result when trying to machine SiC due to its low fracture toughness. However, from past experience it has been proven that ductile regime machining of silicon carbide is possible. The main goal of the subject research is to improve the surface quality of a chemically vapor deposited (CVD) polycrystalline SiC material to be used in an optics device such as a mirror. Besides improving the surface roughness of the material, the research also emphasized increasing the material removal rate (MRR) and minimizing the diamond tool wear. The surface quality was improved using a Single Point Diamond Turning (SPDT) machining operation from 1158nm to 88nm (Ra) and from 8.49μm to 0.53μm (Rz; peak-to-valley).

No abstract

The purpose of applying a laser beam in the micro-laser assisted machining (μ-LAM) process is to preferentially heat and thermally soften the surface layer of the work piece material (4H-SiC) at the interface with a diamond cutting tool. In the μ-LAM process the laser beam (1480 nm and 400 mW) is delivered to the work piece material through a transparent diamond cutting tool. Thus the cutting tool and the laser system are integrated and coupled; in contrast with other LAM processes where the cutting tool and laser are separate and distinct systems. Scratches were made on a 4H-SiC substrate using the μ-LAM process. The characteristics of the scratches, such as depth and width, are principally a function of the cutting tool geometry, applied forces, cutting speed, and laser heating. White light interferometer microscopy and Atomic Force Microscopy (AFM) techniques were used to measure the geometry (depth and width) of the scratches. Force analysis was carried out to evaluate the laser heating effect on the cutting forces and the measured depth of cut. The force analysis included an evaluation of the mechanical work, specific energy, and understanding the effect of laser heating on the cutting process. The scratch tests performed on 4H-SiC with the laser heating showed that there is a greater than 50% reduction in relative calculated hardness values of work piece material, resulting in a significant reduction in cutting forces.

No abstract

No abstract