Papers by Author: Jing Ming Fan

Abstract: Abrasive jet machining is an efficient technology for the fabrication of three dimensional micro structures on brittle materials. In abrasive jet machining, the variation or fluctuation in the amount of abrasive supply has a significant effect on the quality of the machined structures. An image processing technique is employed in this study to study the abrasive flow rate variation, in which abrasive jet pictures are captured at different moments by a Particle Image Velocimetry technology and then processed using Labview Vision Assistant and MATLAB. It shows that the abrasive flow rate fluctuates with time under the jetting conditions considered. The abrasive flow from larger nozzles or at smaller air pressures shows more profound fluctuation. Although the abrasive flow fluctuation from smaller nozzles remains almost constant when the air pressure is changed, for larger nozzles, the magnitude of the fluctuation gradually decreases as the air pressure is increased.

Abstract: Abrasive air jet micro-machining is a new promising technology for processing brittle material. An experimental study of micro-channeling on quartz crystals using an abrasive air jet is presented. The effect of the processing parameters on the produced channel profile such as the channel width, depth and kerf taper angle is analyzed, along with the effect on the roughness of channel bottom surfaces. Plausible trends of the major process performance measures with respect to the process parameters have been revealed. These trends are useful in guiding the selection of process parameters in practice.

Abstract: Four uniform patterns include grid (GD), concentric circle (CC), spiral (SL) and uniformly random (UR) and one non-uniform (NUR) pattern of diamond grits are designed to fabricate mono-layer brazed diamond grinding tools. The grinding forces of five tools in the cut-in and the stable grinding processes are tested and compared. The results showed that NUR tool has the higher lateral and normal grinding forces than that of other uniformly tools in the cut-in and the stable grinding processes. GD owns the lower and smoother grinding forces than that of other tools in the cut-in process. In the stable grinding process the mean grinding forces of UR tool, namely F_LM and F_ZM, are higher than that of GD, CC and SL tools. And normally CC and SL tools own the lower grinding forces than that of GD tool, especially at the higher feeding speed.

Abstract: Simulation of the dynamic characteristics of micro abrasive water jet (MAWJ) is conducted using computation fluid dynamics (CFD) software Fluent 6.3 flow solver. The velocity distributions and particle behaviors of the free jet and impinging jet in and out of the nozzle are investigated under different input and boundary conditions. In the free jet simulation, a reduction in water pressure corresponds to more rapid decay of the jet velocity along the jet axis, whereas particle mass concentration has no influence on the jet velocity. In the impinging jet simulation, the effect of the impingement surface on the flow field increases with a decrease of the stand-off distance. The simulation results in this study provide the foundation for optimizing the nozzle structure and improving cutting efficiency and cutting performance of MAWJ.

Abstract: Micro abrasive water jet (MAWJ) machining is a new promising micro machining technology for brittle material. The rate of material removal is one of the most important parameter for abrasive processes. Predictive mathematical model for the material removal rate is presented for micro channel machining by micro abrasive water jet (MAWJ). A dimensional analysis technique is used to formulate the model. The validity and predictive capability of the models are assessed and verified by an experimental investigation when machining glasses. It shows that the predictions of the models are in good agreement with the experimental data.

Abstract: This paper presents a study of using an abrasive slurry jet for the machining of micro channels on brittle glasses. The machined surface morphology and channel dimensions are used to assess the technology. Surface morphology was found featuring with two types of wave patterns; one was along the channels with large wave lengths as a result of the jet deflection during the motion of nozzle, and the other was due to viscous flow that resulted in smooth surface eroded predominantly by ductile mode. The investigation showed that using higher jet pressure and higher particle concentration enables to create channels with higher depth, although these widened the channels and degraded the surface quality in some cases by inducing a larger number of pit fragments on the surface. With proper control of the operating parameters, this technology can be used for machining micro channels on brittle materials with high quality of surface finish.

Abstract: Micro drilling experiments of glass by Micro Abrasive Suspension Jets (MASJ) were carried out. The influence of the nozzle and compositions of slurry including the selection of abrasives, suspending agents and their concentrations on material removal, the depth and the diameter of the machined holes were investigated for glass drilling. Four processing stages are provided to describe the erosion profile characteristics. The suspension properties of slurry play an important role in MASJ machining. Five million molecular weight non-ionic polyacrylamide with concentration of 0.6% , white corundum abrasive and the longest length of the nozzle cylindercal zone can achieve lager material removal and better quality of hole in MASJ machining.

Abstract: Abrasive Suspension Jets (ASJ) is a new micro processing technique developed for micro processing of hard and brittle materials based on the traditional Abrasive Water Jet (AWJ). Based on drilling experiments of glass using MASJ technology, the dependence of material removal, the depth and the diameter of the machined holes on the process parameters, such as working pressure, processing time, standoff distance, incidence angle and concentration of abrasives were investigated. Experimental results show that the material removal is approximately proportional to working pressure, processing time and concentration of abrasives, except the standoff distance. It is founded that the processing time is the most remarkable influence factor on the material removal and the depth of the holes. But the working pressure doesn’t show obvious effects to the material removal and the depth of hole with lower pressure in MASJ. The increase of standoff distance will decrease the material removal and depth of hole, and the concentration of abrasives can improve a few of drilling ability. Further, it is founded that longer processing time and smaller standoff distance will achieve higher MASJ drilling efficiency and better quality of hole, with 90 degree jet incidence angle.

Abstract: Micro abrasive jet machining (MAJM) is a high effective economical technology for three dimensional micro structure fabrications of brittle materials. It is widely used in the fabrication of semiconductors, electronic devices, micro electro-mechanical systems (MEMS), optical-electronic and optical devices, and medical instruments. In this paper, based on the experimental study of MAJM for glass, the influences of the nozzle type/size and abrasive type on the material erosion rate and structure profile are analyzed. The results show that the rectangular nozzle can yield a more accurate and efficient machining performance due to reduced flux effect. By contrast, with round nozzle all the cross section profiles of the machined patterns show rounded V-type shape. The rectangular nozzle is able to produce geometry with flat shape. The machining area is almost independent of the abrasive hardness, and the erosion rate increases with the increase in the hardness of the abrasive grits. The nozzle geometry is of great importance for machining accuracy and the efficiency.