Papers by Keyword: Micro Machining

Abstract: Micromachining technology is a challenge in industrial production to meet the demand for components for machinery. In this research, a study of the best parameters was required to produce the best hole accuracy and the lowest burr formation in the inlet and exit holes using micro-drilling. The work-piece material and cutting tool used respectively was a brass plate with a thickness of 0.5 mm and a micro drill with a diameter of 0.2 mm commonly used for electronic PCBs. The quality of holes was measured and observed by using a stereomicroscope (optical equipment). This microscope can zoom up to 50x objects to facilitate measurement. The microscope was attached by using a digital camera type YW-200 so that the object of observation could be measured using a computer. The result shows that the largest deviation of hole diameter (0.217 mm) occurred at a spindle speed of 14,000 rpm with the lowest feed rate (5 mm/min). Meanwhile, the smallest deviation of hole diameter (0.202 mm) occurred at a spindle speed of 20,000 rpm with a maximum feed rate of 10 mm/min. The maximum burr height (0.050 mm) occurred at a spindle speed of 17,000 rpm and a feed rate of 10 mm/min. In addition, the minimum burr height (0.038 mm) occurred at a spindle speed of 14,000 rpm and a feed rate of 5 mm/min. Therefore, it can be concluded that the deviation of hole diameter was inversely proportional to the spindle speed, and the height of the burr formation was directly proportional to the feed rate.

Abstract: Micro milling is discussed to fabricate micro-scale structures on titanium alloy thin wires. A machine tool was developed to conduct the milling operations with improving the clamping stiffness. A 0.3 mm diameter wire inserted into polyurethane tubes was clamped on an R-shaped groove on the machine table. The cutting tests were conducted with or without the polyurethane tube support. The machining shapes, the surface finishes and the cutting forces were measured to verify the effect of the polyurethane tube and machine table clamping system on stability in the cutting process. The groove direction is out of the feed direction of the end mill without the polyurethane tube support. The micro grooves are machined properly with a fine surface in the feed direction with the support. The cutting forces change periodically with the cutting thickness and the rotation of the cutter in milling. Non-symmetric grooves are also machined with the developed clamping system.

Abstract: Guiding systems for precision manufacturing machines have to fulfil high demands. Low compliance and the absence of friction is required to achieve a high production accuracy. This article presents a novel active guiding system based on the combination of ultrasonic levitation and magnetic actuators. Firstly, the combined actuator and its working principles are described. Subsequently, the concept for an active, frictionless and medium-free guiding system is outlined. In addition to the free degree of freedom (DOF) in guiding direction, the other 5 DOF are adjustable in order to improve the guides positioning accuracy. The experimental validation of the concept is conducted with a simplified prototype, acting as a 3 DOF adjustable planar guide. Finally, measured compliance frequency responses demonstrate the performance of this novel active guiding concept.

Abstract: Micro grinding is a promising process to produce small scale structures in hard and brittle materials. Just like macro grinding processes, a high number of abrasive grits embedded on the grinding tools, are applied. This high number of grits results in low cutting forces on individuall grits and very small chip thicknesses, thus generating surfaces with a high quality. The manufacturing of the tools needed to produce such small structures is very challenging. In this paper, a method for the coating of micro pencil grinding tools (MPGTs) is proposed. MPGTs utilize coated superabrasive grits for micro machining hard and hardened materials. The MPGTs developed in the research presented here consist of a base body made of cemented carbide, abrasive grits made of cBN and a nickel bond. The experimental setup and the coating parameters needed to produce a 50-55 μm MPGT with 5-10 μm cBN grits nominal diameter is outlined. In addition, the tools are validated by machining a 500 μm long groove on a hardened 16MnCr5 workpiece.

Abstract: In this research a confocal chromatic point sensor was implemented in a desktop sized machine tool. The sensor was used to detect the surface in z-direction. Data from the machine control of the x- and y-axes is extracted and combined with the z- information of the sensor to directly scan surfaces. With the presented sensor, micro structures as small as 5 μm can be characterized. Based on the possibilities of this measuring system, face milling before the actual micro machining can be avoided by determining tilts and waviness of the workpiece. Also the effective tool diameter can be determined and compensated. After machining, the structure can be measured for quality control. Based on this measurement system, a micro machining process was developed broadening the potential for the use of desktop sized machine tools.

Abstract: The paper deals with the development and investigation of a novel, hybrid clamping technology for micro machining. This new technology was developed through a combination of the freezing and mechanical clamping. Then, its technical and economic characteristics, including achievable holding forces, clamping time, stiffness, accuracy, flexibility in terms of different workpiece and process parameters, etc. were determined by experiments. After that, they were compared with the corresponding characteristics of the conventional technologies. The results of this comparison allowed to draw a conclusion about the advantages and disadvantages of the developed hybrid clamping technology.

Abstract: Brittle materials like ceramics or glass can be machined by cutting with negative rake angles and by abrasive machining processes. Especially grinding allows for low surface roughness and high shape accuracy. Conventional path-controlled grinding processes may damage functional surfaces if brittle fracture occurs and may thus lead to lateral, radial and axial cracks. High grinding forces can be a reason for brittle fracture when grinding ceramic materials. A solution for this effect may be the application of force controlled grinding processes. In this paper adapted control algorithms were implemented for force controlled grinding and verified in grinding experiments. As an example, cylindrical grooves were ground with an injection moulded spherical grinding tool in alumina and zirconia ceramics. After grinding surface roughness, shape accuracy and process forces are analysed and discussed.

Abstract: Error compensation is a key to reach the geometric accuracies required for high precision machine tools. To prevent errors from affecting the machining process, compensation values for the feed axes can be used. However, conventional feed axes can only compensate deviations in their feed directions. By controlling its integrated hydraulic guiding system, the feed axis presented in this paper is capable of compensating errors in all other degrees of freedom as well. Using a specifically developed program, ideal parameters for the compensation of errors in a realistic 3D-axis-system were calculated. The axis’ characteristics were examined on a test rig for different types of controllers and compared to those parameters. It could be shown that the presented highly integrated hydraulic feed axis is capable of compensating typical errors resulting from such a 3D-setup.

Abstract: As the requirements of MEMS continuously increase, the micro ceramic structures are widely used due to their favorable material properties such as high strength, hardness and resistance to high temperature, wear and erosion. However, the sintered ceramic compact is hard to be machined as its high strength. On the other hand, the low strength of green ceramic body makes it difficult to guarantee the machining accuracy. In this paper, ceramic compacts are pre-sintered below the sintering temperature. Pre-sintered ceramic compacts have suitable strength and are easy to be machined. Simple ceramic micro structures are easily generated with micro tools fabricated on line by wire electrical discharge grinding method (WEDG). Extensive experiments are carried out to investigate the influence of the strength of pre-sintered ceramic compact on the tool wear. It was found that the best machining results are achieved under the conditions of using the tool with a semi-circle cross section, the tool rotation speed of 1500 rpm and the pre-sintered ceramic compact formed under the pressure of 150MPa within the range of experimental conditions in this study.

Abstract: The aim of this paper is to review the recent developments conducted by our groups for the achievement of 3C-SiC based heterostructures compatible for MEMS applications. It deals with different aspects, from the influence of the defects generated at the 3C-SiC/Si interface on the mechanical properties to the elaboration of new multilayered structures, required for specific applications like, for example, Atomic Force Microscopy.