Investigation of Gyroscopic Effect on the Stability of High Speed Micromilling via Bifurcation Analysis

Catastrophic tool failure due to the low flexural stiffness of the micro-tool is a major concern for micromanufacturing industries. This issue can be addressed using high rotational speed, but the gyroscopic couple becomes prominent at high rotational speeds for micro-tools affecting the dynamic stability of the process. This study uses the multiple degrees of freedom (MDOF) model of the cutting tool to investigate the gyroscopic effect in machining. Hopf bifurcation theory is used to understand the long-term dynamic behavior of the system. A numerical scheme based on the linear multistep method is used to solve the time-periodic delay differential equations. The stability limits have been predicted as a function of the spindle speed. Higher tool deflections occur at higher spindle speeds. Stability lobe diagram shows the conservative limits at high rotational speeds for the MDOF model. The predicted stability limits show good agreement with the experimental limits, especially at high rotational speeds.

Complex shaped micro-channels generation using tools fabricated by AWJ milling process

Fabrication of complex shape micro-channels is a major challenge for manufacturing industries. Currently in commercial applications, lithography and non-conventional machining processes like lasers, electro-discharge machining (EDM) and chemical etching are commonly used for fabrication of these channels. In the present work, a novel Abrasive water jet (AWJ) milling based tool fabrication strategy has been proposed and implemented to make micro-tools (die/ electrode). The path strategy for jet movement is considered in a manner to selectively remove metal from a piece of material such that the resulting three-dimensional features become the required die shape that can be used as tool for the texturing process. Micro-tool of complex shape as fabricated on hard material (EN 31) sheet of 12 mm thickness and its geometry were analysed by controlling the step over (SO) distance. Hydraulic control based hard press contact texturing setup was developed to analyse the performance of such fabricated tools. Experiments were conducted on soft materials like, PMMA, Copper, Brass, aluminium and Nylon. Taper along the depth of the channels was observed because of the taper of the tool during fabrication. During fabrication, width of the tool less than 200 μ m was found wavi in nature as there was not enough backing material present to bear the side wise jet pressure of impinging jet. Buckling on the tools was observed with tool height greater than 1 mm.

Experimental Study on Micro-Grinding of Ceramics for Micro-Structuring

In this study, micro-grinding was performed to investigate the machining characteristics of alumina and zirconia. The machining of ceramics remains highly challenging owing to their properties, such as high brittleness and wear resistance, which leads to a shorter tool life and high machining costs. Polycrystalline diamond (PCD) was selected as the tool material, as it is suitable for machining hard and brittle materials, and micro-electrical discharge machining (EDM) was used to fabricate PCD micro-tools. When using a resistor-capacitor generator circuit in micro-EDM, the discharging energy is related to the working capacitance, and by controlling the working capacitance, the different edge radii and the surface roughness of the tool can be easily achieved. The feed rate, depth of cut, and rotation speed were set as experimental parameters to investigate the grinding characteristics of the ceramics. During the experiment, the grinding force and roughness of the bottom surface were monitored, and the roughness of the machined surfaces was measured using a three-dimensional surface profiler. A working capacitance of 1000 pF was used to fabricate a tool with an edge radius of 3.5 µm. The lower radius of the tool edge resulted in a decrease of the cutting force by 50% at most and a surface roughness of 19 nm Ra.

Experimental Study on Fabrication of CVD Diamond Micro Milling Tool by Picosecond Pulsed Laser

Because of the many advantages of high-precision micromachining, picosecond pulsed lasers (PSPLs) can be used to process chemical-vapor-deposited diamonds (CVD-D). With the appropriate PSPL manufacturing technique, sharp and smooth edges of CVD-D micro tools can be generated. In this study, a PSPL is used to cut CVD-D. To optimize PSPL cutting, the effects of its parameters including fluence, pulse pitch, and wavelength on the cutting results were investigated. The results showed that the wavelength had the greatest impact on the sharpness of CVD-D. With PSPL cutting, sharp cutting edges, and smooth fabricated surfaces of the CVD-D, micro tools were achieved. Finally, the fabrication of CVD-D micro milling tools and micro milling experiments were also demonstrated.

Effect of tool rotation on the fabrication of micro-tool by electrochemical micromachining

Electrochemical micromachining (EMM) uses anodic dissolution in the range of microns to remove material. Complex shapes that are difficult to machine on hard materials can be fabricated easily with the help of EMM without any stresses on the workpiece surface and no tool wear. Fabrication of microfeatures on microdevices is a critical issue in modern technologies. For the fabrication of microfeatures, precise micro-tools have to be fabricated. In this present study, EMM milling is used for the fabrication of micro-tools. For this, an EMM setup has been designed. Tungsten carbide tools with an initial diameter of 520 µm have been selected and are electrochemically machined to reduce their diameter. The tool and workpiece are connected as anode and cathode, respectively. The electrolyte solution used for this investigation is sodium nitrate. A comparative analysis of the effect of tool rotation over both machining accuracy and surface finish has been performed.

An experimental investigation on tool wear behaviour of uncoated and coated micro-tools in micro-milling of graphene-reinforced polymer nanocomposites

Nanomaterials such as graphene have been added to various matrices to enhance mechanical, thermal and electrical properties for various applications requiring intricate designs at the micro-scale. At this scale, mechanical micro-machining is utilised as post-processing to achieve high surface quality and dimensional accuracy while still maintaining high productivity. Therefore, in this study, the machinability of polymer nanocomposites in micro-scale (micro-machinability) is investigated. Graphene (0.3 wt%)-reinforced epoxy nanocomposites were fabricated using traditional solution mixing and moulding. The samples were then subjected to micro-milling at various cutting speeds using three different micro-tools, including uncoated, diamond and diamond-like carbon (DLC) tools. Mechanical and thermal properties of nanocomposite were also used to support the discussions. The result indicates that the DLC-coated tool shows better performance than the other tools for less tool wear, improved surface quality and less cutting forces.

Investigation of Operational Characteristics of Mechatronic Systems in Industry 4.0

This work presents the results of an analysis of the main expected potential problems that may occur in the implementation of the Industry 4.0 reform. It is proved that the pace and level of development of this reform will largely be determined by the effectiveness of the used mechatronic systems. It has also been established that as a result of systematic miniaturization of the nodes of radio-electronic equipment and microelectronic equipment and microelectronic technology, the main problem of these reforms and the implementation of complex technological processes is instrumental support, especially cutting micro-tools. Therefore, the examples of these micro-tools show methods for improving their performance characteristics.