Key Engineering Materials Vols. 389-390

Abstract: In order to enhance the cooling performance, better understanding of the effects of coolant parameters is necessary. In this project, a total of five input parameters for actively cooled and activated cutting fluid were studied. An aerosol spectrometer was used to measure the particle size spatial distribution of the cooling mist in the fluid. Taguchi method was used in the design of experiments. It was found that the unit volume net specific particle counts exhibit the behavior of oscillation and attenuation of a second order dynamic system. Cooling mist particle spatial frequency ranges from 0.01269/μm to 2.5/μm, the weighted average size ranges from 0.3051μm to 3.714μm and the particle size difference for 99.8% count attenuation ranges from 0.5μm to 19.7μm. The order of importance of the input parameters was studied and the coolant concentration was found as the most important input parameter for the unit volume net particle counts.

Abstract: A truing technique that can be used to shape the tip of an electroformed diamond tool into a hemisphere and flatten diamond grains on the tool working surface at the same level as the bond face was developed. A polycrystalline diamond disk whose top surface roughened by electrical discharge machining was partially flattened by grinding was used as a truer. Diamond grains on the tool working surface were successfully flattened along the hemispherical tool profile when the grains mesh size of #1000 was employed. In addition, a grinding test using glasslike carbon as a work material revealed that a surface roughness of less than 50 nm Rz could be obtained in both cases when moving the tool on contour and scanning paths.

Abstract: The grinding performance of wheel remarkably decreases by the loading of wheel surface in dry grinding of hard carbon parts. In this report, we propose the removal method of loaded carbon chips in which an adhesive tape is removed with carbon chips after putting on a loaded wheel surface by an elastic roller with the setting load . The removal characteristics are experimentally investigated by analyzing the projecting height of abrasive grains, removal force of adhesive tape and so on. The removal method results in the enough projecting height of abrasive grain.

Abstract: Truing and dressing are essential processes of grinding wheel preparation. They make the wheel geometry true with respect to its rotational axis and its cutting surface sharp. These factors significantly influence the quality of the final profile and surface produced from the grinding process. Prediction of the optimum wheel surface for grinding, defined as one which produces an accurate profile and cuts most efficiently can greatly minimize the time to optimize grinding wheel performance. This paper describes virtual dressing and truing operations, takes under account vibration of the dressing apparatus and shows how to generate wheel surface replica under different conditions.

Abstract: High precision mold grinding technique to obtain mirror surface is required which realizes minimization or omission of final polishing by skilled workers. In the previous reports, ultrasonically diamond grinding experiments were carried out to confirm ultrasonically oscillation effect for die steel face grinding. Mirror surface was obtained successfully and little abrasive worn out was found. In the above technique, the cutting edge shape of a tool affects the ground surface resulting from transcription of cutting edge. In other words, cutting edge truncation of grinding tool is required to be smooth and glossy surface. This paper describes the cutting edge truncation of diamond electroplated tools which are used in ultrasonically assisted grinding. Experiments were carried out to confirm truncation effects on the ground surface and grinding force. It was confirmed that cutting edge truncation is effective method to obtain mirror surface and excessive truncation causes large grinding force and chattering.

Abstract: The erosion process in micro-machining of brittle glasses using a low pressure slurry jet is discussed. The process capability of the technique is assessed by examining the machined surface integrity in relation to fluid flow dynamics in micro-hole generations. The holes produced are characterised by a “W” shape in the cross section, while the surface morphology is distinguished by three zones associated with the fluid flow behaviour, i.e. a direct impact zone, a wavy zone and an accumulation zone. The surfaces appear to be smooth and without cracks, indicating a predominance of the ductile mode erosion process. With the increase of pressure, the erosion rates can be enhanced as a result of the expending of the accumulation zone while the outer diameter of the holes remains unchanged. This study shows that this technique can be used for micro-machining with high surface quality, and provides an essential understanding for further research in the avenue.

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: Abrasive jet precision finishing is a new machining method, which injects slurry of abrasive and liquid solvent to grinding zone under without feed condition. The machining is simulated by Finite Element Method (FEM) in the paper. Hydrodynamic pressure on modeling of wedge-like grinding zone between wheel and workpiece on abrasive jet finishing with wheel as restraint was established and simulation, based on Navier-Stokes and continuity equations. The liquid hydrodynamic pressure distributing principle and affecting factor were investigated. The relation hydronamic pressure with grinding wheel velocity was stimulated and verified experimentally. The experiment results show that the simulation results are agreement with experiment, so the simulation model can well forecast hydrodynamic pressure distribution at contact zone.

Abstract: This paper presents a new study on profit optimization of abrasive blasting systems. In the study, the effects of many parameters such as the air pressure, the initial nozzle diameter, the cost components and the nozzle wear on the profit rate were investigated. Based on the results of the optimization problem, regression models for determination of the optimal exchanged nozzle diameter in order to get the maximal profit rate were proposed. With “optimal diameter”, both the profit rate and the cleaning time can be reduced significantly.

Abstract: Thick films are needed in micro-electro-mechanical systems (MEMS) as insulation, piezoelectric and ferroelectric materials. To form the thick film, powder jet deposition (PJD) method has been proposed. In the PJD process, microparticles are sprayed out from nozzle under the conditions of room temperature and atmospheric pressure, and make a film on the substrate. We have developed a new jet mechanism of double-nozzle type, and reported its results previously [1]. In this study, we optimized the shape of the nozzle through investigating the influence of different dimensions and shape of the nozzle on the particles blasting velocity. As a result, it is found that nozzle diameter has a large affect on particles velocity.