Abstract: This study presents design of an ultra-precision wafer grinder which incorporates state-of-the-art automatic supervision and control system. The wafer grinder is characterized by wafer surface shape control, grinding forces and wafer thickness monitoring systems. The design provides a totally integrated solution to the ultra-precision grinder that is capable of grinding silicon wafers with surface roughness Ra<3 nm and total thickness variation<2µm/300mm.
Abstract: The CVD diamond/diamond-like carbon composite film is fabricated on the WC-Co substrate by depositing a layer of Diamond-like Carbon film on the surface of conventional Micro- or Nano-crystalline diamond film. The hot filament chemical vapor deposition (HFCVD) method and vacuum arc discharge with a graphite cathode are adopted respectively to deposit the MCD/NCD and DLC films. A variety of characterization techniques, including filed emission scanning electron microscope (FE-SEM) and Raman spectroscopy are employed to investigate the surface morphology and atomic bonding state of as-deposited MCD/DLC and NCD/DLC composite film. The results show that both MCD/DLC and NCD/DLC composite films present similar surface morphology with the MCD and NCD films, except for scattering a considerable amount of small-sized diamond crystallites among the grain boundary area. The atomic-bonding state of as-deposited MCD/DLC and NCD/DLC composite films is determined by the top-layered DLC film, which is mainly consisted of amorphous carbon phase and no discernible sp3 characteristic peak can be observed from their Raman spectrum. Furthermore, the tribological properties of as-deposited MCD/DLC and NCD/DLC composite films is examined using a ball-on-plate reciprocating friction tester under both dry sliding and water-lubricating conditions, comparing with conventional DLC, MCD and NCD films. Silicon nitride balls are used as counterpart materials. For the CVD diamond/DLC composite films, the self-lubricating effect of top-layered DLC film is beneficial for suppressing the initial friction peak, as well as shortening the run-in period. The average friction coefficients of MCD/DLC and NCD/DLC composite films during stable sliding period are 0.07 and 0.10 respectively in dry sliding; while under water-lubricating condition, they further decreases to 0.03 and 0.07.
Abstract: A rough ground fused silica surface can be ground in a ductile mode by ultra-precision grinding after repairing the surface and subsurface micro cracks (SSMC) by CO2 laser irradiation. In this paper, 2D finite element thermal analysis of unidirectional multi-pass laser irradiation on fused silica was conducted, and the simulation results were compared with the thermal analysis and experiments results of single pass laser irradiation. Thermal analysis results show that the SSMC on the ground fused silica can be repaired and surface roughness can be decreased simultaneously by unidirectinal laser raster scan with a power of 10.5 W, a scan velocity of 0.2 m/s and a scan spacing of 40 μm.
Abstract: The main source of heat generation during machining of carbon/epoxy composites is the friction among cutting tool, chip and workpiece. The friction coefficient between carbon/epoxy composites and a monocrystalline diamond under different temperatures was investigated. The results show that the friction coefficient between diamond and carbon/epoxy composites changes with the variation of temperature due to the change of properties of epoxy resin. The friction coefficient increases with the increasing temperature. However, when the temperature of workpiece was higher than the glass transition temperature of epoxy resin, the friction coefficient decreased.
Abstract: Localized ultra-high frequency induction brazing is proposed to deal with the thermal deformation problem of brazed diamond tools. In order to investigate the temperature field distribution, the simulation model of induction brazing for solving the temperature field is described through the FLUX 2D software. The experiment is carried out to verify the numerical simulation result. Good agreement is observed between experimental value and simulation result. The influence factors on temperature field are investigated by the simulation software. Ultra-high frequency induction brazing with diamond grits is carried out based on the conditions given by simulation results. Good bonding between the diamond grits and the filler alloy is observed and the width of the brazed region is less than 3 mm.
Abstract: Based on similarity principle, cutting modes of turning, milling, grinding etc are equivalent to three load forms of dot, line and face. And three different loads of dot, line and face are applied on the nano-ZrO2 workpiece by three different indenter models of dot, line and face. To one-dimensional ultrasonic vibration system, the influence is studied which is of different load forms and different load magnitudes on acoustic system characteristics of ultrasonic machining. The experimental results show that, the change of loads has little influence on the acoustic system parameters of ultrasonic machining when the load modes on the nano-ZrO2 workpiece are dot and line. And when the load mode is surface contact, the change of loads has significant influence on the acoustic system parameters of ultrasonic machining.
Abstract: The deformation of the spindle system is the main factor affecting the accuracy of ultra-high speed grinding. To calculate the deformation of ultra-high-speed grinding spindle system is required to consider not only the formation of structural deformation, but also the thermal deformation. Using the simulation method, oil temperature and grinding force are calculated in this paper. Based on these two factors, the thermal-mechanical deformation of the hybrid spindle system is analyzed and calculated with the method of FEM. the This article uses simulation methods, analysis and calculation of the oil film temperature rise and the grinding force caused by deformation of the liquid and hydrostatic spindle system factors. The methods presented in this paper can be used in digital design of various kinds of spindle systems, in order to improve the accuracy of the spindle system design.
Abstract: A cast iron/low carbon steel sandwich-structured bimetal fabricated through composite casting, followed by hot rolling and hot compression (40% reduction) in a vacuum, and water quenched using Gleeble 3500 thermomechanical simulator. The microstructure of a predominantly martensitic structure is transferred to a matrix with an amount of austenite. The measured results show that the macro-hardness is significantly lower due to the evolution of matrix. A considerable amount of secondary carbides were precipitated from the matrix. This study also shows that a significant difference in the value of coefficient of friction (COF) at the end when hot rolling (HR) was tested under three sets of sliding wear conditions, while those for hot rolling and heat treatment (HT) tends to be merged. An increased wear resistance of interfacial zone is expectable.
Abstract: The underlying data form of a wafer is a matrix of length (or height) measurements. In the presence of noise, evaluation parameters are normally biased. The expectation value such as peak-to-valley and GBIR (global backside ideal range) is systematically larger than the “true” value. Correction and compensation need a large population of measurements to analytically estimate both bias and the uncertainty. In this study, approach to obtain the true value is to extract a “true” profile by filtering noise from the measured data. In previous paper, the digital filter with wavelet transformation (WT) is proposed and efficiency to remove the noise, however, the method is introduced the pseudo-Gibbs effect. Then, we propose the digital filter with new algorithm of total variation (TV). In this paper, the new algorithm of TV is proposed and the digital filter by new TV indicate that data is filtered without the pseudo-Gibbs effect. The digital filters by WT and new TV are applied on the sample data of actual measurement system to investigate their performance of noise reduction.
Abstract: This paper introduces an automatic ultrasonic wall thickness measurement system, which adopts the way that the tube billet is partially immersed in the water during the measurement, applied in wall abrasive grinding of nuclear fuel encrust tube billet. Meanwhile, the main components of the measurement system, as well as their characters and functions, are addressed. What’s more, the analysis of the factors, which influencing the system stability and measuring reliability, are also conducted, coupling with the system stability and measuring reliability demonstration.