Explore the vast range of titles available.

Aerostatic bearings are widely used in ultra-precision manufacturing equipment as a crucial support component. However, turbulent vortices in the recess can induce micro-vibration of the aerostatic bearing, which can severely affect stability. To further suppress the formation of turbulent vortices and reduce the micro-vibration, an aerostatic bearing with a square micro-hole arrayed restrictor (SMAR) was designed and the influences of structural parameters of the SMAR on its static and dynamic performance were investigated using numerical simulations and experiments. The transient flow characteristics of aerostatic bearings with different numbers and spacing of micro-holes were studied using 3D large eddy simulation (LES), and the formation mechanism of turbulent vortices and the law of turbulent interaction between adjacent micro-holes were analyzed. The static performance and micro-vibration of the aerostatic bearing were measured experimentally to verify the effectiveness of the SMAR. The results show that the formation of turbulent vortices and micro-vibrations can be effectively reduced by the optimized design of the SMAR, while the static performance of the bearing is basically unchanged. The micro-vibration decreases rapidly with the number of micro-holes ranging from 1 to 36 and remains steady with the number of micro-holes ranging from 36 to 100. The micro-vibration decreases rapidly with the spacing of micro-holes ranging from 2 dn to 8 dn and remains steady with the spacing of micro-holes ranging from 8 dn to 10 dn. This study contributes to further understanding the mechanism of turbulent vortex formation in aerostatic bearings with a SMAR.

This paper presents a system that can be used for micro-hole measurement; the system comprises an optical fiber stylus that is 5 µm in diameter. The stylus deflects when it comes into contact with the measured surface; this deflection is measured optically. In this study, the design parameters of the optical system are determined using a ray-tracing method, and a prototype of the probing system is fabricated to verify ray-tracing simulation results; furthermore, the performance of the system is evaluated experimentally. The results show that the design parameters of this system can be determined using ray-tracing; the resolution of the measurement system using this shaft was approximately 3 nm, and the practicality of this system was confirmed by measuring the shape of a micro-hole 100 µm in diameter and 475 µm in depth.

This work is an experimental investigation and multi-response optimization of micro-electrical discharge machining (µEDM) of carbon-Kevlar hybrid composite (CKHC). Based on the chosen input factors namely voltage (V), EDM feed (EF) and tool speed (TS), the experimental runs were fixed as per Taguchi’s L9 orthogonal array. Single and multi-response optimization were carried out using Taguchi and technique for order of preference by similarity to ideal solution (TOPSIS). The responses selected for the study were machining time (MT) and degree of circularity (DOC). The Taguchi analysis identified the optimal input parameter values for minimal MT as a V of 180 volts, EF of 2 μm/sec, and TS of 1000 rpm. The corresponding values for the maximum DOC were 120 volts, 2 μm/sec, and 1000 rpm. Analysis of variance (ANOVA) revealed that voltage significantly affects the variation in MT. However, the DOC is mostly affected by the change in TS. The optimal values of V, EF, and TS obtained from TOPSIS were 150 volts, 4 μm/sec, and 1000 rpm. An improvement of 0.757881 in the preferred solution for optimal settings was confirmed from the analysis. Images from scanning electron microscopy (SEM) confirmed the overcut of the machined micro-holes.

Laser processing has emerged as a pivotal technique for micro-hole fabrication owing to its exceptional efficiency and absence of tool wear. Nevertheless, certain imperfections persist in laser drilling. Consequently, this study presents a comprehensive analysis of the impact of laser processing parameters, methods, and physical field-assisted techniques on the quality and efficiency of laser drilling based on the characteristics desired for micro-holes. The findings reveal that selecting an appropriate laser wavelength and pulse width, coupled with meticulous adjustments to laser power, repetition frequency, and defocusing amount can enhance either processing efficiency or micro-holes quality; however, optimizing both aspects simultaneously remains challenging. By refining scanning strategies and implementing pulsed joint secondary repair approaches, heat accumulation is minimized while micro-holes quality is optimized; nevertheless, ensuring high processing efficiency poses difficulties. Ultrasonic assisted laser drilling enhances processing efficiency by facilitating the expulsion of molten materials, while magnetic field-assisted laser drilling improves processing efficiency by mitigating the attenuation of the laser caused by plasma clouds. Both techniques contribute to enhancing the quality of hole walls through their stirring effect. Water-based ultrasonic/magnetic field-assisted laser perforation combines heat dissipation and secondary flushing effects with ultrasonic/magnetic field assistance, resulting in superior micro-hole formation. Magnetic field-ultrasonic assisted laser perforation synergistically combines both effects. Furthermore, this study distinguishes between the promoting and inhibiting effects of rotating and static magnetic fields on molten metal flow, elucidating the impact of ultrasound and magnetic fields on molten metal from a melt dynamics perspective. Finally, we summarize the influence of each optimization method on micro-hole quality characteristics and processing efficiency while providing insights into future development trends.

The high-frequency and high-speed printed circuit board (PCB) with lower transmission loss, higher heat resistance, and better processability play increasing significant roles in mobile communication technology. However, because the materials and micro drilling process of high-frequency and high-speed PCB are very different from the traditional printed board, there are still many of key techniques to be explored in the future study. In this paper, the characteristics of high-frequency and high-speed PCB were presented. Researches concerning the design and wear ability of micro drill, the analysis of micro drilling force and temperature, and the quality of micro holes were reviewed. Finally, several key techniques and challenges regarding materials and micro drilling were suggested.

In micro-electrical discharge machining (micro-EDM) using the non-hollow circular cross-section tool electrode with the side flushing technique, when the aspect ratio of machined micro-hole is expected to be further increased, the discharge debris expelling speed and the working fluid renewal efficiency are weakened, which hinders the improvement of machining efficiency and accuracy with increased machining depth. In order to reveal the flow behavior of the working fluid in the micro-EDM gap, so as to realize the high-precision and high-efficiency machining of micro-hole with high aspect ratio, a three-phase flow simulation model of fluid, bubble, and debris is established in Fluent under the ideal assumption that the spark discharges occur continuously to generate high-pressure bubbles. The simulation results show that when the boundary condition of the flushing pressure at the side gap entrance is set to 0, the pressure wave emitted when the high-pressure bubble expands, which is formed by the instantaneous gasification of the working fluid between electrodes under high temperature, is the source of pneumatic force that drives the working fluid flow at the micron scale. Affected by the gap flow channel structure and the viscous resistance from inner wall, the flow velocity direction of the fluid dragging the discharge debris to rise up and expel will change, forming a dynamic alternation process of flowing into and out of the side machining gap entry. As the machining depth increases, due to the energy attenuation of the pressure wave propagating from the bottom gap to the side gap entrance, the expelling speed of the discharge debris decreases exponentially at the side gap entrance, resulting in the reduced machining efficiency and accuracy. However, when the simulated bubble generation frequency is increased to the megahertz level, the expelling efficiency of debris has a step-like improvement. The continuous and high-frequency generation of high-pressure bubbles can maintain a high pressure gradient in the bottom gap, and the discharge debris is able to continuously move upward without falling back to accumulate in the bottom gap, which is beneficial to the stable and smooth machining process, realizing the high-precision and high-efficiency machining of micro-hole with high aspect ratio.

Electrochemical machining is widely used in biomedical, aerospace, automotive, and other fields. The development of electrochemical machining (ECM) is restricted by many factors such as the difficulty of preparing micro-electrode, large machined gap and serious stray corrosion. In this paper, we present a method to fabricate micro-holes by combining micro-graphite electrode with hollow structure. Firstly, a sealed graphite electrode was proposed to guarantee that the sediment can be fully removed by the flowing electrolyte. Then, the effect of machined parameters such as the pulse frequency, machined voltage, electrode feeding speed, and electrolyte concentration on machining quality was studied. By optimizing the machined parameters, the minimum value of micro-hole taper with 0.07 could be obtained. To improve the shape precision of workpiece, this paper designed the hollow structure inside the electrode. With the increasing of the pulse frequency, the machining accuracy of micro-holes increased. The results suggested that the pulse frequency of 100 kHz, the machined voltage of 18 V, the feeding speed of 1 µm/s, and electrolyte concentration of 5% were more suitable for micro-holes machining with ECM.

In the micro-EDM blind-hole machining of Cf-ZrB2-SiC ceramics, defects such as bottom surface protrusion and machining fillets are often encountered. The implementation of an electrode-assisted oscillating device has proven effective in improving machining outcomes. To unravel the fundamental reasons behind the optimization enabled by this auxiliary oscillating device, this paper presents fluid simulation research, providing a quantitative comparison of the differences in machining gap flow field characteristics and debris motion behaviors under conditions with and without the assistance of the oscillating device. Firstly, this paper briefly describes the characteristics of Cf-ZrB2-SiC discharge products and flow field deficiencies during conventional machining and introduces the working principle of electrode-assisted oscillation devices to establish the background and objectives of the simulation study. Subsequently, this research established simulation models for both conventional machining and oscillating machining based on actual processing conditions. CFD numerical simulations were conducted to compare flow field differences between conditions with and without auxiliary machining devices. The results demonstrate that, compared to conventional machining, electrode oscillation not only increases the maximum velocity of the working fluid by nearly 32% but also provides a larger debris accommodation space, effectively preventing secondary discharge. Regarding debris agglomeration, oscillating machining resolves the low-velocity zone issues present in conventional modes, increasing debris velocity from 0 mm/s to 7.5 mm/s and ensuring continuous debris motion. Furthermore, the DPM was used to analyze particle distribution and motion velocities, confirming that vortex effects form within the hole under oscillating conditions. These vortices effectively draw bottom debris outward, preventing local accumulation. Finally, from the perspective of debris distribution, the formation mechanisms of micro-hole morphology and the tool electrode wear patterns were explained.

This study investigated the mechanism of UVAD using numerical and analytical techniques. Silicon wafers possess challenging cutting properties due to their inherent brittleness and susceptibility to cracking along specific crystal orientation. Hence, non-traditional cutting methods like UVAD hold promise for precision micro-hole drilling in silicon wafers. In order to comprehend the mechanism of UVAD, the numerical technique utilized a direct brittle micro-cracking model within a 2D finite element (FE) method. This facilitated a comparative analysis between conventional drilling (CD) and UVAD, with a specific focus on understanding the micro-cracking mechanisms during the mechanical process. This study examined primarily the cutting force, micro-fracture analysis, and cutting energy. The numerical technique effectively predicted micro-cracks within the brittle regime, a task that is challenging to accomplish using analytical methods alone. In parallel, an analytical technique was developed to predict brittle-ductile transition (BDT) lines by analyzing the thrust force and specific cutting energy (SCE), combined with the numerical technique. Various feed rates per revolution were tested to validate the analytical force predictions. The analytical results demonstrate that the force profile corresponds to the transient cutting depth, while the numerical results indicated that the direct brittle micro-cracking model effectively demonstrated the fracture mechanisms, particularly at greater depths of cut. The SCE graph can predict the formation of a ductile regime on the cutting surface of the drilled micro-hole, although predicting micro-fractures on the side edges of the drilled micro-holes remains challenging. Additionally, UVAD demonstrated a reduction in micro-fractures on the sides of drilled micro-holes, particularly at very low feed rates per revolution.

In this paper, water jet-guided laser (WJGL) drilling of Cf/SiC composites was employed and the effects of the processing parameters on the depth and quality of the micro-holes were systematically investigated. Firstly, the depth measurement showed that the increase in processing time and power density led to a significant improvement in micro-hole drilling depth. However, the enhancement of the water jet speed resulted in a pronounced decrease in the depth due to the phenomenon of water splashing. In contrast, the scanning speed, path overlap ratio, pulse frequency, and helium pressure exhibited less effect on the micro-hole depth. Secondly, the microstructural analysis revealed that the increase in power density resulted in the deformation and fracture of the carbon fibers, while the augmentation in water jet speed reduced the thermal defects. Finally, based on the optimization of the processing parameters, a micro-hole of exceptional quality was achieved, with a depth-to-diameter ratio of 8.03 and a sidewall taper of 0.72°. This study can provide valuable guidance for WJGL micro-hole drilling of Cf/SiC composites.