Key Engineering Materials Vols. 375-376

Abstract: In order to figure out the temperature anywhere and anytime in the milling insert, based on the point heat source, and grounded on the experimental data, we established the mathematics model of heat density function and temperature field for milling insert with 3D complex groove under the irregular heat source, and has proved correctly to its special case with this mathematics model, thus established the theoretical foundation for groove optimizing and reconstruction of milling insert with 3D complex groove.

Abstract: Experiments of combining micro EDM with USM are carried out to enhance the machining ability and flexibility of the micro EDM, improve the machining state, and increase the productivity and aspect ratio of the micro holes. Basing on RC pulse power supply and workpiece vibration, the micro holes are drilled. The results of comparing experiments indicate that in the processes of both micro EDM without USM and micro EDM with USM, the machining velocity and the wear of the electrode increase with the increase of open voltage and loop capacitance. The experiment results of amplitude influencing on the machining process indicate that with the increase of ultrasonic amplitude, the machining velocity heightens and the aspect ratio of the micro holes augments; at the same time, however, the wear of the electrode and the extensive magnitude of the holes increase. Micro holes with some cross-section and accurate profile are drilled steadily.

Abstract: High frequency acoustic agitation is known to improve mass transport in conventional electroplating and electroforming. To better understand the effect of ultrasonic agitation on microelectroforms with high height-to-width aspect recessed microstructure features, electroforming of Ni from a nickel sulfamate type electrolyte under the influence of high frequency ultrasound (33KHz) at different level of power intensity from 2W/cm2 to 16W/cm2 was investigated experimentally in this paper, and then optimum operating parameters were determined basing on surface topography. A number of microelectroforming experiments assisted with acoustic agitation were further carried out to demonstrate and revise the optimum process parameters and further some metal microdevices were produced. Experimental results showed that fewer drawbacks in the microelectroforms, such as nubbles, pits, blunt-edges, and collapses were observed in the microcomponents when sonication power 12W/cm2~14W/cm2 was drawn on. Microelectroforming with ultrasonic irradiation at appropriate power intensity was characterized by better surface morphology and better uniform filling behavior.

Abstract: Nano-ceramics possessed ascendant mechanical property and physical characteristics contrast with traditional engineering ceramics, and its machining with ultrasonic assistance has been considered one of the most efficient methods. In the present paper a novel ultrasonic grinding vibration device has been developed and the theoretical model of grinding force has been created for ultrasonic vibration grinding. The influences of grinding parameters on grinding forces were tested with self-designd acoustic system based on local resonance. According to the test data, the effect of depth of cut and wheel velocity on the grinding force with/without ultrasonic assistance was analyzed. Both in common and ultrasonic grinding the normal grinding force and tangential grinding force descend against the wheel velocity, while ascend along with the depth of cut. In any case the grinding force in ultrasonic grinding was not more that that in common grinding.

Abstract: A new ultrasonic aided lapping technology was developed by combining lapping technology and ultrasonic machining technology. The appended special tangential ultrasonic vibration changes the material removal rate (MRR) characteristics. In order to clarify the influence of ultrasonic vibration, in this paper, the MRR models in ultrasonic aided single-point scratch were deduced based on indentation fracture theory. Through contrast scratching and lapping experiments, the MRR characteristics in ultrasonic aided lapping of engineering ceramics were presented. Research result shows that the MMR in ultrasonic aided lapping is larger than that in conventional lapping under the same conditions; with the increase of ultrasonic generator power and lapping pressure, the MMR in lapping increases correspondingly.

Abstract: Serials of ultrasonic face machining experiments were designed and carried out on glass materials with free abrasives. Two different kinds of ultrasonic machining, namely, non-rotary ultrasonic machining (NRUSM) with free abrasives and rotary ultrasonic machining (RUSM) with free abrasives were compared. Two systems were set up to in-process monitor the changes of static forces and frequency respectively. The effects of static force, spindle speed and amplitude of ultrasonic vibration on material removal rate (MRR) and surface roughness were analyzed. The surface of workpieces was also observed by a digital video microscope system. The experimental results indicated that, at the given conditions, there exists an optimal value of static force and amplitude of vibration to obtain the maximum MRR, and RUSM was found to be superior to NRUSM in the MRR, but inversely in surface roughness.

Abstract: Magnetorheological finishing (MRF) is a novel precision optical machining technology. Owing to its flexible finishing process, MRF can eliminate subsurface damage, smooth rms micro roughness and correct surface figure errors. The finishing process can be easily controlled by a computer. Through proper designing of numerical control, sphere and asphere optics can be machined by magnetorheological finishing with high quality. Optical sphere is machined using dwell time algorithm and surface shape 2 pt. PV has been improved from 0.17um to 0.07um.

Abstract: Transparent Nd:YAG ceramics which are very hard and brittle materials, are very difficult to be polished. There are many micro scratches or damages on the surface after mechanical polishing with Al2O3. In order to remove micro scratches or damages, chemical mechanical polishing (CMP) was adopted to manufacture Nd:YAG ceramics. In the polishing experiment, Pellon and Chemcloth pads were utilized for chemical mechanical polishing of Nd:YAG ceramics. Colloidal SiO2 was selected as the polishing slurry in two different polishing environments, acidity and alkalinity. The surface roughness was determined by using atomic force microscope. In this study, four polishing experimental combinations that each combination contains one of the two pads and one of the two polishing environments were carried out in the optimum polishing condition. Then the high quality surface of transparent Nd:YAG ceramics with the best surface roughness of < 0.2 nm RMS and few micro scratches or damages is obtained by adopting CMP process with Chemcloth pad and colloidal SiO2 in acidic condition.

Abstract: Silicon nitride ceramics materials have excellent properties such as small density, high rigidity, high Young's modulus, high wearability, good thermal stability and chemical stability, which make it become one of the most appropriate materials for rollers of high precision bearing. Chemical Mechanical Polishing (CMP) technology is employed to have an ultra-precision machining process for silicon nitride ceramics materials workpiece and the effects of workpiece surface roughness in different abrasive are discussed in this research. The XRD and SEM technology are used to take phase analysis and surface profile detection for the finishing workpiece polished with CeO2 abrasive. The chemical reaction mechanism and the material remove mechanism of silicon nitride ceramics materials in CMP process with CeO2 abrasive are both analysed and discussed in this paper. The research result shows that an extremely smooth surface of silicon nitride ceramics materials workpiece with roughness 5nm Ra is obtained after CMP process with polyurethane polishing pad and CeO2 abrasive.

Abstract: The polyimide polishing film is a kind of soft polishing films with polyimide substrate and abrasive cement. It isn't replaced by other grinding tool because of its acid resistance, alkali resistance, water-resistance, oil resistance, heat-resistance et al. The paper focuses on ascertaining the minimal substrate thickness of polishing film, selecting molding method and molding technology. Applying the skim coating processes, and using a self-made, film making device, a lab-level, making process of polyimide polishing film is developed, and the polyimide polishing films are made in a lab. Then, study the polishing films form and analyze the molding performances with scanning electron microscope, and get an effect rule of the consistency of polyamides adhesive and abrasive to polyimide polishing films form and the appropriate consistency of polyamides adhesive finally.