Micro Machine Tool Research Articles

Influence of Additive Manufactured Stainless Steel Tool Electrode on Machinability of Beta Titanium Alloy

Additive manufacturing technology provides a gateway to completely new horizons for producing a wide range of components, such as manufacturing, medicine, aerospace, automotive, and space explorations, especially in non-conventional manufacturing processes. The present study analyzes the influence of the additive manufactured tool in electrochemical micromachining (ECMM) on machining beta titanium alloy. The influence of different machining parameters, such as applied voltage, electrolytic concentration, and duty ratio on material removal rate (MRR), overcut, and circularity was also analyzed. It was inferred that the additive manufactured tool can produce better circularity and overcut than a bare tool due to its higher corrosion resistance and localization effect. The additive manufactured tool can remove more material owing to its strong atomic bond of metals and higher electrical conductivity.

Simulation-Based and Experimental Investigation of Micro End Mills with Wiper Geometry.

One of the major advantages of micromachining is the high achievable surface quality at highly flexible capabilities in terms of the machining of workpieces with complex geometric properties. Unfortunately, finishing operations often result in extensive process times due to the dependency of the resulting surface topography on the cutting parameter, e.g., the feed per tooth, fz. To overcome this dependency, special tool shapes, called wipers, have proven themselves in the field of turning. This paper presents the transfer of such tool shapes to solid carbide milling tools for micromachining. In this context, a material removal simulation (MRS) was used to investigate promising wiper geometries for micro end mills (d = 1 mm). Through experimental validation of the results, the surface topography, the resulting process forces, and tendencies in the residual stress state were investigated, machining the hot work tool steel (AISI H11). The surface-related results show a high agreement and thus the potential of MRS for tool development. Deviations from the experimental data for large wipers could be attributed to the non-modeled tool deflections, friction, and plastic deformations. Furthermore, a slight geometry-dependent increase in cutting forces and compressive stresses were observed, while a significant reduction in roughness up to 84% and favorable topography conditions were achieved by adjusting wipers and cutting parameters.

Design of a Miniature Bi-Directional Non-Back Drivable Mechanism with High Retaining Torque

Ensure the safe operation of a mechanical system that involves motion is essential; some traditional ways to achieve this goal are mechanical devices such as breaks or clutches. This paper presents the design, manufacturing, and test of a bi-directional non-back-drivable mechanism for its application in miniature mechanical systems, like prostheses, robotics, or micro-machine tools. The bi-directional non-back-drivable mechanism operates as a locking device, limiting the torque transmission from the output into the input axle. Application of Design for X methods served to identified and prevent the main drawbacks of the mechanisms used for locking tasks, namely wear and backlash, to make the novel mechanism less sensitive to such factors, keeping high transmission performance in a tight space and with minimum parts. The presented set of design equations and selection graphs are for ABS plastic. A unified approach for the design of the bi-directional non-back-drivable mechanism is presented. The final section of the paper is devoted to the manufacturing and test of a sample of the mechanism.

Large-area femtosecond laser milling of silicon employing trench analysis

A femtosecond laser is a powerful tool for micromachining of silicon. In this work, large-area laser ablation of crystalline silicon is comprehensively studied using a laser source of pulse width 300 fs at two wavelengths of 343 nm and 1030 nm. We develop a unique approach to gain insight into the laser milling process by means of detailed analysis of trenches. Laser scribed trenches and milled areas are characterized using optical profilometry to extract dimensional and roughness parameters with accuracy and repeatability. In a first step, multiple measures of the trench including the average depth, the volume of recast material, the average longitudinal profile roughness, the inner trench width and the volume removal rate are studied. This allows for delineation of ablation regimes and associated characteristics allowing to determine the impact of fluence and repetition rate on laser milling. In a second step, additional factors of debris formation and material redeposition that come into play during laser milling are further elucidated. These results are utilized for processing large-area (up to few mm2) with milling depths up to 200 µm to enable the fabrication of cavities with low surface roughness at high removal rates of up to 6.9 µm3 µs−1. Finally, laser processing in combination with XeF2 etching is applied on SOI-CMOS technology in the fabrication of radio-frequency (RF) functions standing on suspended membranes. Performance is considerably improved on different functions like RF switch (23 dB improvement in 2nd harmonic), inductors (near doubling of Q-factor) and LNA (noise figure improvement of 0.1 dB) demonstrating the applicability of milling to radio-frequency applications.

Design and Accuracy Analysis of a Micromachine Tool with a Co-Planar Driving Mechanism

Due to the requirements of manufacturing miniaturized high-tech products, micromachining with micromachine tools has come to be regarded as an important technology. The main goal of this study is to build up the key technologies, including optimal structure and configuration design, synchronous driving control, analysis of optimal accuracy, in order to develop a low-cost and high-accuracy micromachine tool with a multi-degrees of freedom (DOF) platform with a co-plane synchronous driving mechanism. Due to the advantages of such a mechanism, the machine is able to possess a high feed resolution and high accuracy without the use of expensive drive components and high-end CNC controllers. Because of the no pile-up structure, the machine has less movement inertia effect, as well as the merits of light weight, high stiffness, and increased stability. Furthermore, the machine has more DOF, resulting in a better cutting performance than that of 3-DOF machine tools. To better understand the characteristics of major error sources of the machine in order to further enhance its accuracy, hybrid error analysis, kinematics analysis, and a volumetric error model were conducted. Finally, a prototype of the designed micromachine tool was built, and cutting experiments for accuracy calibration and verification were carried out using this machine. The results showed that the machine was able to effectively execute 4-DOF microcutting with positioning accuracy of 800 nm.

Investigation of machining parameters of super hardened tool in micro electrical discharge machining

Micro Electrical Discharging phenomenon is an important machining method adapted at micro level. The process parameters like current, voltage, pulse on time & capacitance are heavily influencing for material removal rate and electrode wear rate in this micro Machining. So to achieve higher material removal rate and minimum electrode wear rate we need to optimize the process parameters of micro EDM like current, voltage, pulse on time & capacitance. In this research work, EN 24 STEEL is used as a work piece and three types of electrodes normal brass tool, cryogenically treated tool and coated tool are used as a tool for micro Machining. Taguchi technique is used as optimization tool to optimize the parameters in this research. Multi response optimization technique topsis is also used to optimize the Micro- EDM parameters.

Sub-Picosecond Micromachining of Monocrystalline Silicon for Solar Cell Manufacturing

In this study a prototype sub-picosecond laser was investigated for cutting and scribing of silicon wafers. The Yb:KYW laser used for this investigation, unlike ultrashort systems used previously, generates pulses of 650 fs, i.e., between the pico and femtosecond range. The laser was placed in a micromachining setup, involving a galvo scanner and a telecentric lens. A study of the influence of the processing parameters on the crater width, depth, and quality of machining was carried out. The optimal parameters were found to be 343 nm, 200 kHz, 7 mm/s, and 15 pattern repetitions. The experiments were performed using samples of a silicon wafer of 210-µm thickness. The experimental results show that the sub-picosecond laser can be a promising and competitive tool for solar cell micromachining. In comparison to the commercially available ultrashort pulse laser systems, we find the sub-picosecond laser to be a more cost efficient and reliable source, than a femtosecond one. In addition, the prototype Yb:KYW design offers some unique parameters, such as repetition rate in the range of 100–400 kHz, UV wavelength or obtainable laser fluence close to the silicon ablation thresholds.

Application of femtosecond laser micromachining in silicon carbide deep etching for fabricating sensitive diaphragm of high temperature pressure sensor

Pressure sensors that can work over 500 ℃ are widely needed in aerospace and petrochemical fields, while silicon based high temperature pressure sensors are difficult to survive such high temperature. Silicon carbide (SiC) shows better mechanical and electrical properties than silicon, which is a feasible candidate to replace silicon for manufacturing high temperature pressure sensor that can work over 500 ℃. However, because of the ultra-high hardness and excellent chemical inertness of SiC, it is difficult to pattern structures on SiC wafer by common etching methods, especially deep etching. Femtosecond laser (fs-laser) is a practicable tool for SiC micromachining as reported in many literatures, but few of them concerns on SiC deep etching in fabricating high temperature pressure sensor’s sensitive diaphragm. In this paper, blind holes with diameter of 1200 μm and depth of 270 μm were fabricated on a 350 μm-thick 4H-SiC wafer by fs-laser, which forms an 80 μm-thick membrane as sensitive diaphragm for pressure sensor. Experiments were conducted to study shape deviation, machining accuracy, edge morphology, sidewall steepness as well as surface roughness of the machined structure. Testing results show that the size errors of machined blind holes are 2.02 % in diameter and 0.38 % in depth, the sidewall steepness is good with an inclination angle of 1.7°, and surface of the sensitive diaphragm is smooth with an average roughness of 320 nm. However, elliptical shape and over etching happens to the fabricated sensitive diaphragm because of inappropriate laser scanning mode, uneven energy distribution and laser irradiation delay. Generally, research shows that fs-laser micromachining is a feasible method for SiC deep etching in fabricating sensitive diaphragm of high temperature pressure sensor.

Low-Power, Multimodal Laser Micromachining of Materials for Applications in sub-5 µm Shadow Masks and sub-10 µm Interdigitated Electrodes (IDEs) Fabrication.

Laser micromachining is a direct write microfabrication technology that has several advantages over traditional micro/nanofabrication techniques. In this paper, we present a comprehensive characterization of a QuikLaze 50ST2 multimodal laser micromachining tool by determining the ablation characteristics of six (6) different materials and demonstrating two applications. Both the thermodynamic theoretical and experimental ablation characteristics of stainless steel (SS) and aluminum are examined at 1064 nm, silicon and polydimethylsiloxane (PDMS) at 532 nm, and Kapton® and polyethylene terephthalate at 355 nm. We found that the experimental data aligned well with the theoretical analysis. Additionally, two applications of this multimodal laser micromachining technology are demonstrated: shadow masking down to approximately 1.5 µm feature sizes and interdigitated electrode (IDE) fabrication down to 7 µm electrode gap width.

Enhanced Positioning Algorithm Using a Single Image in an LCD-Camera System by Mesh Elements’ Recalculation and Angle Error Orientation

In this article, we present a method to position the tool in a micromachine system based on a camera-LCD screen positioning system that also provides information about angular deviations of the tool axis during its running. Both position and angular deviations are obtained by reducing a matrix of LEDs in the image to a single rectangle in the conical perspective that is treated by a photogrammetry method. This method computes the coordinates and orientation of the camera with respect to the fixed screen coordinate system. The used image consists of 5 × 5 lit LEDs, which are analyzed by the algorithm to determine a rectangle with known dimensions. The coordinates of the vertices of the rectangle in space are obtained by an inverse perspective computation from the image. The method presents a good approximation of the central point of the rectangle and provides the inclination of the workpiece with respect to the LCD screen reference system of coordinates. A test of the method is designed with the assistance of a Coordinate Measurement Machine (CMM) to check the accuracy of the positioning method. The performed test delivers a good accuracy in the position measurement of the designed method. A high dispersion in the angular deviation is detected, although the orientation of the inclination is appropriate in almost every case. This is due to the small values of the angles that makes the trigonometric function approximations very erratic. This method is a good starting point for the compensation of angular deviation in vision based micromachine tools, which is the principal source of errors in these operations and represents the main volume in the cost of machine elements’ parts.

PRECISION MICROMACHINING OF METALS BY CUBR LASER

The ability to laser machine materials with high resolution and high throughput is critical in advanced manufacturing for a vast array of applications, from photovoltaic cells to bio-compatible micro-components. Copper bromide (CuBr) lasers with their excellent beam quality promised noticeable advantages and improvements in high precision and material processing at the microscale. The application of the CuBr laser as a precision tool for micromachining of different metals has been demonstrated. That good performance was a result of the combination of high power visible radiation, short pulses, and close to the diffraction-limited laser beam divergence with high-speed galvo scanner beam steering.

Green micromachining of ceramics using tungsten carbide micro-endmills

This paper presents an experimental analysis on micromachining of green-state silicon carbide (SiC) and aluminum nitride (AlN) using uncoated tungsten carbide (WC) micro-endmills. Although the unique properties of ceramics make them ideal materials for many applications involving micro-scale features, the industrial adaptation of ceramics at the micro-scale has been hindered due to the lack of viable ceramic micro-manufacturing techniques. Green micromachining (GMM), where micro-scale features are created by micromachining green-state ceramics that contain ceramic particles and a polymer binder, offers a potential solution for this problem by affording tremendous improvements in micromachinability with respect to sintered ceramics. After the completion of GMM, the green parts are debound and sintered to obtain the final component with the desired micro-scale features. In this work, we evaluated GMM characteristics of powder-injection molded green-state SiC and AlN to correlate process conditions and green-material compositions with the micromachining forces, quality, and tool wear. An experimental study that involves full immersion micromilling tests with 254 μm diameter micro-endmills at different cutting speeds and feed rates is conducted. For each of the two materials, two binder states (with and without wax) and two powder states (with micro particles only, or with both micro- and nano-particles) are investigated. Green micromachining forces, specific energies and the resulting surface roughness are analyzed quantitatively. A qualitative analysis of burr formation and channel quality, as well as a preliminary study on micro-tool wear are also performed. Both the machining conditions and the material compositions are seen to have a strong effect on micromachinability of green-state ceramics. Overall, we conclude that GMM can be a viable ceramic micro-manufacturing strategy if favorable (or optimal) micromachining and material parameters are identified through the presented (or a similar) micromachinability study.

Micro-Machining of Nano-Polymer Composites Reinforced with Graphene and Nano-Clay Fillers

Following a comprehensive review of nanocomposite materials and their machinability, this paper details experimental results from the micro-slotting of two different nanocomposites reinforced with graphene platelets and nanoclay fillers as opposed to their base material matrix. The evaluation includes the quality of machined surfaces characterised by SEM, cutting forces monitored using force dynamometry, and surface roughness measured using both contact and non-contact techniques. The evaluation included four filler percentages by weight between 0.1 and 1% in addition to 0% with the plain matrix material. The effect of feed rate is also evaluated at 3 levels (10, 20 and 30 μm/rev) with cutting speed at 4 levels (15.7, 31.4, 62.8 and 94.2 m/min). Dry cutting experiments were performed on an ultra-precision desktop micro-machine tool. Uncoated tungsten carbide end mills 1 mm in dimeter were used in all tests. Surface roughness increased gradually with feed rate while cutting speed had no effect. Ra values ranged from 0.1 – 0.35 μm. Common increases in cutting forces with either feed rate or cutting speed were observed. Forces in general were higher for the material reinforced with 0.3–0.5% nanofiller. Negligible tool wear occurred following the cutting of 140 slots of 100 μm depth (removing 182 mm3 of the material).

Experimental Validation of the Transmission Line Model Via Impedance Spectroscopy of an Ordered Array on Porous Carbon Electrode

In this paper, the interface of a porous substrate with an arranged and well-defined geometry is investigated for the impedance response with different electrolytes by using the well known electrochemical technique of Electrochemical Impedance Spectroscopy (EIS). Based on De Levie's Transmission Line Model (TLM) for porous electrodes a modification has been done in the model by incorporating the CPE behavior to reflect the non-ideal behaviour for real electrodes at low frequencies. The geometry used to validate the proposed model was fabricated from a smooth Glassy carbon electrode (GCE) surface to correlate the EIS response to that obtained by the model. The desired array was obtained by using laser micromachining tool on a glassy carbon substrate with a goal to study the influence of different electrolytes, varying electrolyte concentrations, the morphological features of pore- depth and radii of pore as well as different pore shapes. The outcomes of the experiments carried out on the in-house setup are compared with the MATLAB simulated results of the impedance. The transition from resistive to capacitive behavior is found to be shifted to lower frequency side and TLM behavior at high frequencies is more apparent as the concentration is increased. For the same concentration, different electrolytes are found to behave differently due to varying conductivity and ion sizes. In all the experiments carried out the impedance response showed CPE (constant phase element) behavior at the low frequency end while for high frequencies the nature/appearance of TLM behavior is found to be dependent on the pore depth to radius ratio. In addition the concept of time constant is also dealt with which exhibits differences for different geometries of the pores on glassy carbon. The results suggest that the GC electrode engaged here could provide a tractable model for studying electrochemical impedance behavior of porous electrodes without using any surface area analysis or pore volume analysis technique. Keywords: Transmission Line Model, Glassy carbon, EIS, MATLAB

Photoionization and trans-to-cis isomerization of β-cyclodextrin-encapsulated azobenzene induced by two-color two-laser-pulse excitation

Azobenzene (1) and the complex resulting from the incorporation of 1 with cyclodextrin (1/CD) are attractive for light-driven applications such as micromachining and chemical biology tools. The highly sensitive photoresponse of 1 is crucial for light-driven applications containing both 1 and 1/CD to reach their full potential. In this study, we investigated the photoionization and trans-to-cis isomerization of 1/CD induced by one- and two-color two-laser pulse excitation. Photoionization of 1/CD, which was induced by stepwise two-photon absorption, was observed using laser pulse excitation at 266nm. Additionally, simultaneous irradiation with 266 and 532nm laser pulses increased the trans-to-cis isomerization yield (Υt→c) by 27%. It was concluded that the increase in Υt→c was caused by the occurrence of trans-to-cis isomerization in the higher-energy singlet state (Sn), which was reached by S1→Sn transition induced by laser pulse excitation at 532nm. The results of this study are potentially applicable in light-driven applications such as micromachining and chemical biology tools.

Sensing, smart and sustainable product development (S3 product) reference framework

Enterprises must become ‘sensing, smart and sustainable (S3)’ to face global challenges related to local, national and global market dynamics. Therefore, reconceptualisation and redesign in these enterprises must accommodate emergent technologies, new practices and strategies. In this sense, enterprises have used new product development as a strategy for remaining competitive in the marketplace; thus, they can provide a new generation of products offering solutions to contemporary social problems and responding to changing consumer demands. These new-generation products are mostly technology-based and consider sustainable objectives. In this context, concepts such as sensing, smart and sustainable products (S3 products) have emerged to satisfy different social requirements. Therefore, this work focuses on providing a reference framework that presents a systematic process for the development of S3 products. This reference framework is based on the integrated product, process and manufacturing system development reference model. The main objective of this work is to fill the gap vis-à-vis the current lack of design roadmaps that permit the development of this new generation of products in S3 enterprises. The development of a reconfigurable micro-machine tool is presented as that of an S3 product.

Influence of Radar Targets on the Accuracy of FMCW Radar Distance Measurements

Distance measurement tasks in micromachine tools need to be performed with micrometer accuracy. For such tasks, frequency-modulated continuous-wave (FMCW) radars with a combination of frequency and phase evaluations are a good choice. However, the accuracy cannot be indefinitely increased as there are constraints on the target size and placement imposed by the limited space inside micromachines. This paper investigates the influence of target geometry and position on the accuracy of its range estimation using a W-band FMCW radar with a bandwidth of 25 GHz. A relation between target geometry and accuracy is established through the Cramer–Rao lower bound (CRLB). Based on the measurements of different targets, an optimal shape and size is proposed, which provides an average accuracy in the single digit micrometer range. Furthermore, the influence of different bandwidths on the accuracy is investigated. It is also demonstrated how the CRLB can be used to optimize the size of a target, when a certain accuracy is needed. In addition, antenna field regions are analyzed for suitable target placements. Finally, the radar system is implemented in a machine tool and measurements with accuracies in the micrometer range are carried out.

Automation of tool path generation in multi-process micromachine tool for micromachining of prismatic and rotational parts

ABSTRACTComputer numerical control (CNC) code generation is an inimitable activity of a Computer-aided manufacturing (CAM) system. Tool path formulation is considered as a machine-dependent activity, and expertise is essential to make attuned for a specific micromachine tool. This paper describes research for retrofitting of a multi-process micromachine tool for automatic CNC code generation for 2.5D micromachining. Micro turning, micro drilling and micro end milling processes are all considered. The proposed system comprises of three main elements: (i) part feature extraction through an extensible mark-up language (XML) schema, (ii) manufacturing logic formulation and CNC code generation by means of mathematical logic and (iii) online integration. XML-based feature extraction ensures trouble-free integration with the decision-making system. Automation of CNC code generation eliminates the need of human expertise, avoids compatibility issues and minimises program creation time. The developed system integrated with the micromachine tool through communication interface for real-time micromachining. The proposed system is intended for 2.5D machining of miniature and micro parts with external step, hole and slot features. The developed system performance has been validated through case study implementations.

Simulation and experiment of femtosecond laser polishing quartz material

ABSTRACTFemtosecond laser is ideal tool for micro-machining of hard and brittle materials, such as quartz material. The basis of experiments on femtosecond laser polishing quartz shown that, when other process parameters were the same, the greater the scanning offset distance, the more obvious ravines in polished surface, the more rough bottom surface. Using MATLAB construct a mathematical model to explain the formation mechanism of roughness. Modeling indicated the parameter of femtosecond polishing should maximize the use of smaller laser energy, recycling roughness mathematical model to select the appropriate offset distance.

High power, ultrashort pulse control through a multi-core fiber for ablation.

Ultrashort pulse ablation has become a useful tool for micromachining and biomedical surgical applications. Implementation of ultrashort pulse ablation in confined spaces has been limited by endoscopic delivery and focusing of a high peak power pulse. Here we demonstrate ultrashort pulse ablation through a thin multi-core fiber (MCF) using wavefront shaping, which allows for focusing and scanning the pulse without requiring distal end optics and enables a smaller ablation tool. The intensity necessary for ablation is significantly higher than for multiphoton imaging. We show that the ultimate limitations of the MCF based ablation are the nonlinear effects induced by the pulse in the MCFs cores. We characterize and compare the performance of two devices utilizing a different number of cores and demonstrate ultrashort pulse ablation on a thin film of gold.