Advanced Materials Research Vols. 126-128

Abstract: This paper presents a new type of two 2-DOF Parallel 2PRR institution, with the unique advantages such as simple motion modeling and easy calculation of the positive and negative solution, operating a large space, simple structure and easy to control, etc. This parallel mechanism can not only be used for the development of glass cutting, grinding materials, milling, processing equipment, spare parts and other planes, but also can be used as a multi-DOF hybrid machine tool flat actuator parallel mechanism which can give full play the advantages of strong reconfiguration, with the main different combinations of auxiliary bodies and set up to meet the individual needs of the user reconfigurable manufacturing cell to be more complex parts processing and high-speed machining.

Abstract: This study presents the development of a drilling technique for an innovative tabletop drilling machine that combines micro-EDM with drilling to fabricate micro-holes in diamond-tool. The mechanisms designs of double V-shaped bearings and double spindles which provide a precision clamping and vertical alignment for diamond-tool and micro-tube are devised to enable to machine a co-centric micro-hole for micro-tool. A diamond-tool, made with copper-based sintered alloy, is drilled by using the developed technique of co-centric micro-hole EDM-drilling into a hollow shaft which can create equilibrium of drilling forces, prevent a drilling squeezing to be occurred and enable to offer a temporary storing space for drilling chips. Relative experiments including the determinations of drilling ratio and discharge capacitance are carried out via this established machine. Experimental results show that excellent geometric and dimensional accuracy of micro-holes on the diamond-tool can be achieved.

Abstract: As the high speed bearings, hybrid journal bearings are usually used in high and super high speed grinding machine spindle system. Since the bearing operates under high speed conditions, the excessive temperature rise of bearing is a key factor to lower the accuracy of the spindle system and limit the bearings working speed, so restrict the bearing applications. In this paper, the model of hybrid journal bearing is established to analyze the heat mechanism. In addition, the temperature field distribution for the certain hybrid journal bearing at high speed is studied by ANSYS considering the heat transfer characters between fluid and solid. The experiment of temperature for hybrid journal bearing system in super high speed grinding machine is also performed. The thermal properties and the measure for controlling temperature rise of such bearings are analyzed.

Abstract: Thin film solar cells are expected to play a key role in the next generation of photovoltaic devices, due to low costs and manufacturing advantages. Their functionality would be increased further if thin film solar panels were able to be machined efficiently without affecting the integrity of the nanoscale component layers. In this work, we investigated the effects of grinding and polishing processes on the integrity of solar panels. With the limited selection of grinding wheels and abrasive sizes, surface roughness and chipping were in the order of micrometers, while the use of diamond film polishing resulted in roughness in the order of nanometers with minimal damage to the layers.

Abstract: Microtechnologies have been vigorously developed recently. Micro products have been widely used in many fields, for instance, the sensors in electronic, medical, optical and automotive applications. Thermocouples, which are used for temperature measurement, are usually fabricated by utilizing the joining technology of argon arc welding. However, the weld bead is so big that the conductivity and repeatability of temperature signals would be degraded. Laser welding may fix the weld bead problem, but the cost of equipment is relatively high. This study is about butt-welding thin brass wire of 250 m by mean of micro discharge. At first a low temperature plasma torch is formed to ignited arc, then discharge happens to complete the welding. Argon is added at ambient atmosphere during the welding process. The joined interfaces and heat affect zone of the welding is examined by optical and scanning electronic microscopies. Tensile and hardness tests as well as the microscopy examination indicate that this technology is feasible for thin brass welding. The features of this technology include low cost, easy to maneuver, and applicable in industry. This CIMDW technology offer choice for the applications of micro discharge in the field of microtechnology.

Abstract: Micro electrical discharge machining (EDM) has the ability to drill micro holes with high accuracy in metallic materials. The aspect ratio of a micro hole generated by micro EDM is usually higher than those by other processes such as etching, mechanical drilling, and laser. However, it was found that the drilling speed of micro EDM slows down and even stops when the aspect ratio reaches a certain value. To understand this phenomenon, a theoretical model is proposed based on the fluid mechanics and surface tension. Experiments under different machining conditions are carried to verify this model. Experimental results agree with the theoretical values, which indicate the validity of the proposed model. The difference between the theoretical values and the real values might be caused by the debris and the temperature in the discharge gap, which are ignored in the model.

Abstract: This paper presents results of groove machining of potassium niobate nanosheets using an atomic force microscope (AFM). Groove machining operations are performed using recently developed diamond coating (DC) and super sharp silicon (sss) probes. The results obtained using these probes are compared to results obtained using a conventional silicon (Si) probe in order to examine the effects of the material type and the tip radius of the AFM probe on groove machining accuracy.

Abstract: The MEMS technology for various nano/micro devices often requires special facilities and complicated and multistage processes, thus the fabrication cost is extremely high. This research aimed to fabricate nanoscale basic structures on silicon substrates using nanoscratching, which can be potentially used to make nano/micro molds for nanoimprint lithography. In this study, various nano/micro-scale structures, such as groove and, single and multiple layer structures were generated on the silicon substrate using an atomic force microscope equipped with a sharp probe made of monocrystalline diamond. The nanoimprint experiment was also performed using the fabricated single-step mold and silicon-resin to fabricate single island structures.

Abstract: In this study, a 2-D model with dimensionless analysis was proposed by discussing the roles of the active material properties in high energy beam drilling. With the assumption of small Pelect number, quasi-steady transformation and scalar analysis in this model, several dimensionless parameters had been generalized. Among these parameters, the dimensionless material property , defined as evaporation latent heat to internal energy at melting point, was proven to be the key member; which not only significantly influenced the nonlinear variation inside the work piece, but also directly determined the penetration results whose behavior showed a resemblance to the distribution of exponential function in . Further more, the maximum efficiency had been successfully estimated, and the dramatic change of drilling characteristic during the transitional energy region was also reasonably simulated. When compared with the experimental results from Allmen [1], the present model with given copper properties showed an excellent agreement on material removal rate (their relative errors were not more than 15 ％.)

Abstract: A novel grinding approach of micro pyramid-structured surface is proposed by using a 60º V-tip of #600 diamond grinding wheel in CNC system. The research objective is to understand the micro grindability of various hard and brittle materials including quartz glass, silicon, SiC ceramics and WC alloy. First, a CNC mutual-wear truing approach was developed to sharpen the wheel V-tip; then, the wheel V-tip was employed to pattern the micro pyramidal array on workpiece surface along CNC tool paths; finally, the machined micro-structured surface and its form accuracy and aspect ratio were investigated. It is shown that this CNC mutual-wear truing approach can not only produce a V-shaped diamond grinding wheel, but also sharpen the diamond grain edges on the wheel V-tip. This wheel V-tip may be used to machine the micron-scale pyramid arrays on silicon, SiC ceramics and WC alloy surfaces with CNC level reticulated cross tool paths, the depth of cut of 1 m and on-machine V-tip form-truing process. Although the average form error of machined micro-structured surface is very small, its pyramidal tops and groove bottoms appear very large form errors, which are dominated by the wheel V-tip sharpness and the grinding conditions, respectively. This leads to a decrease in the aspect ratio by about 38%, 30% and 14% in contrast to the ideal one of 0.87 for silicon, SiC ceramics and WC alloy, respectively.