Micro-hole Process Research Articles

Investigation of continuous wave/coaxial waterjet-assisted laser combined machining of micro holes in GH3536

A two-step combined processing technique, combining a continuous-wave laser with a waterjet-assisted nanosecond laser, has been introduced to enhance the quality and efficiency of laser micro-hole processing for nickel-based superalloys. Initially, a through-hole was created using a continuous-wave laser, followed by hole refinement with a coaxial waterjet-assisted nanosecond laser. In the first step, orthogonal testing methods were employed to investigate the impact of various parameters, including power, duty ratio, frequency, defocusing amount, and processing time, on the entrance and exit apertures, as well as the hole taper. Through the analysis of variance (ANOVA) method, the optimal parameter combination A2B1C4D3E1 was identified, achieving the minimal hole taper. This combination comprised a power level of 80 %, a duty ratio of 15 %, a frequency of 400 Hz, a defocusing amount of 2 mm, and a processing time of 10 ms. In the second step, a comparison was made between scanning and trepan drilling machining methods. The results unequivocally demonstrated that scanning drilling achieves superior entrance and exit morphologies. Furthermore, the effect of water jet velocity on the morphology of micropores was thoroughly analyzed. The voltage range of the water pump was adjusted from 10 V to 24 V, revealing that a voltage of 20 V produced the smallest hole taper. The scanning filling diameter was accurately preset according to the preformed hole aperture as well as the thickness of the recast layer. Finally, after coaxial waterjet-assisted laser precision machining, the inner wall of the hole is free of cracks, and the recast layer and oxide layer are effectively minimized. The initial hole prefabrication with the continuous-wave laser took merely 0.01 s, and the subsequent fine-tuning with the coaxial waterjet-assisted laser took 2 min and 25 s.

Applying punching without die to micro-hole array processing

Aluminum alloy (Al6061) sheet micro-hole processing is extensively used in smartphones, tablet PC, and smart wearable devices. The micro-hole processing is commonly performed using laser, micro drilling, micropunching, micro discharge, and chemical etching technologies. Micro-punching technology is characterized by precision and rapid processing, but the precision positioning of the punch head and lower die is one of the major difficulties in micro-hole punching, especially in manufacturing array micro-holes. This study used punching without die technology. This technology uses an array punch head to punch the lower die holes on the base, then performs array micro-hole punching. The experimental results show that a micro-hole array with 37 micro-holes were successfully manufactured and can be reproduced many times. Tapered array micro-holes with a high aspect ratio can be manufactured using this punching without die technology; the micro-hole depth can be 260 μm, the inlet diameter is 116 μm, and the outlet diameter is 25 μm. This study has successfully developed the feasibility of array micro-hole punching technology.

Developments, challenges and future trends in advanced sustainable machining technologies for preparing array micro-holes.

The use of array micro-holes is becoming increasingly prevalent across a range of industries, including the aerospace, automotive, electronics, medical and chemical industries. The utilization of advanced sustainable machining technologies offers distinctive advantages and is pivotal for the sustainable manufacture of array micro-holes. This paper examines the sustainable machining techniques commonly employed in the production of array micro-holes, including electrical discharge machining, laser machining, electrochemical machining and composite machining technologies. The paper begins with an elaboration of the processing principles and characteristics of multiple non-traditional machining techniques. The performance indicators of the most commonly used processing technologies in industrial production are summarized from seven perspectives. Six significant avenues for the advancement of sustainable manufacturing technology for array micro-holes have been identified and categorized. This article provides a summary and evaluation of the previous relevant literature, with the aim of offering guidance for the development of array micro-hole processing technologies.

A novel EDM method using longitudinal-torsional ultrasonic vibration (LTV) electrodes to improve machining performance for micro-holes

This study proposes a new EDM method using longitudinal-torsional ultrasonic vibration (LTV) electrodes for micro-hole machining to address the problems of debris removal and difficult working fluid exchange in micro-hole processing, which can enhance the micro-hole machining performance. A 38.9 kHz ultrasonic vibration transducer is developed for LTV electrodes, and the fluid distribution in the micro-holes gap is simulated when LTV electrodes were used to process micro-hole. The effect of ultrasonic amplitude on flow rate and debris removal efficiency is discussed. A study is conducted to analyze the morphogenesis of the electrode extremity and the micro-hole inlet/outlet at different amplitudes. This study finds that applying appropriate ultrasonic amplitude (2–4μm longitudinal amplitude, 0.2–0.35μm torsional amplitude) to the electrode effectively reduces the electrode tip and corner wear and the flanging burr of the micro-hole inlet/outlet. Compared EDM micro-hole machining with the rotating electrode only, the material removal rate (MRR) is increased by nearly two times with the simultaneous application of 4 μm longitudinal ultrasonic amplitude and 0.35μm torsional ultrasonic amplitude to the electrode, and reduction of electrode wear and micro-hole taper by approximately 60% and 80% respectively.

Experimental investigation and optimization of modification during backside-water-assisted laser drilling using flowing water

Backside-water-assisted laser drilling (BWALD) is a laser drilling process in which the workpiece is partially submerged in water. The backside of the workpiece is surrounded by water, and its upside directly contacts the air. In this study, flowing water was used to solve the problem where the generated air bubbles and debris prevent water from penetrating the through-hole and achieve the fabrication of micro-holes with high aspect ratios via BWALD. Moreover, a two-step micro-hole processing strategy was proposed to divide the BWALD into punching-through and modification steps. The modification process is the key to improve the machining performance, but involves numerous processing parameters. So, the effects of modification parameters (pulse energy, modification speed, frequency and number of modifications) on the responses of the micro-hole diameters and roundness were investigated during BWALD using flowing water on the basis of the response surface methodology (RSM). To achieve the optimal combination of parameters for a given situation, the regression models for the inlet diameter, outlet diameter, inlet roundness and outlet roundness of the modified micro-holes were developed. The adequacies of the developed models were subsequently verified by the analysis of variance (ANOVA) method. Finally, the well-rounded micro-hole with an inlet diameter of 105.62 μm and an outlet diameter of 96.65 μm which taper was only 0.21° was obtained with the optimum modification parameters: pulse energy of 15.9 μJ, frequency of 52.9 kHz, modification speed of 4.7 mm/s and number of modifications of 313.

Study of Gas Film Characteristics in Electrochemical Discharge Machining and Their Effects on Discharge Energy Distribution.

Glass is a hard and brittle insulating material that is widely used in optics, biomedicine, and microelectromechanical systems. The electrochemical discharge process, which involves an effective microfabrication technology for insulating hard and brittle materials, can be used to perform effective microstructural processing on glass. The gas film is the most important medium in this process, and its quality is an important factor in the formation of good surface microstructures. This study focuses on the gas film properties and their influence on the discharge energy distribution. In this study, a complete factorial design of experiments (DOE) was used, with three factors and three levels of voltage, duty cycle, and frequency as the influencing factors and gas film thickness as the response for the experimental study, to obtain the best combination of process parameters that would result in the best gas film quality. In addition, experiments and simulations of microhole processing on two types of glass, quartz glass and K9 optical glass, were conducted for the first time to characterize the discharge energy distribution of the gas film based on the radial overcut, depth-to-diameter ratio, and roundness error, and to analyze the gas film characteristics and their effects on the discharge energy distribution. The experimental results demonstrated the optimal combination of process parameters, at a voltage of 50 V, a frequency of 20 kHz and a duty cycle of 80%, that achieved a better gas film quality and a more uniform discharge energy distribution. A thin and stable gas film with a thickness of 189 μm was obtained with the optimal combination of parameters, which was 149 μm less than the extreme combination of parameters (60 V, 25 kHz, 60%). These studies resulted in an 81 μm reduction in radial overcut, a roundness error reduced by 14, and a 49% increase in the depth-shallow ratio for a microhole machined on quartz glass.

Optimization of Femtosecond Laser Drilling Process for DD6 Single Crystal Alloy

In this paper, we explore the optimal combination of femtosecond laser drilling parameters for micro-hole processing on DD6 single-crystal high-temperature alloy and analyze the significance of parameter variations on the microstructure characteristics of the holes. The L25(56) orthogonal test was performed by controlling six parameters during femtosecond laser ring processing: average power; overlap rate; defocus rate; feed amount; gas pressure; and end position. The significance of the influence of the factors was analyzed by ANOVA, and the parameters were optimized by genetic algorithm. Scanning electron microscopy was performed on the micropores and the salient features of the pores were analyzed. Finally, we calculated the extreme differences and conducted single-factor effect analysis. We conclude that the defocus rate has the most significant level on the hole drilling by femtosecond laser ring processing for DD6 single crystal high-temperature alloy; and the effect of the end position is smaller than others. The optimized parameters are power 6.73 W; overlap 99%, defocus 0 mm; pressure 0.2 MPa; feed 0.02 mm, and end −0.4 mm.

Study on the mechanism affecting the quality of micro-hole in ultrasonic-assisted drilling of high-speed circuit boards

High-speed circuit boards are created to meet the high-speed signal transmission requirements of 5G communication technology, but the non-polar resins, flat glass fibers, and multiple and hard fillers used for this purpose have posed new challenges to their micro-hole processing. The quality of micro-hole has always been a decisive factor in board performance. Therefore, this paper aims at proposing a new processing method for improving the micro-hole drilling quality of high-speed circuit boards. By establishing an ultrasonic-assisted drilling tool motion model, analyzing the changes in drilling method, material deformation, chip breakage, and chip removal during ultrasonic-assisted drilling of printed circuit boards, the influence mechanism on micro-hole quality during ultrasound-assisted drilling is studied prudently. Besides, an experimental platform for ultrasonic-assisted drilling is designed and built, and single-factor experiments for verification of ultrasonic effects, optimization of drilling parameters, and orthogonal experiments for ultrasonic-assisted drilling of high-speed circuit boards are conducted on this platform. The experimental results show that the loading of ultrasonic vibration has made an obvious improvement on several machining defects including hole wall roughness, entrance burr, and nail head in micro-hole drilling of high-speed circuit boards. In addition, the influence order of each processing parameter and a better combination of them are discovered, which provides a theoretical research basis and instructions for the improvement of micro-hole quality of high-speed circuit boards.

Analyses of Burr and Exit Thrust Force of Ultrasonic-Assisted Micro-Drilling

With the development trend of miniaturization of product production, ultrasonic assisted micro-drilling technology (UAMD) is more widely used in micro-hole processing due to its unique advantages. In this paper, the effect of 20 kHz harmonic vibration on the exit burr of micro-hole during UAMD has been studied. Based on the self-designed micro-hole drilling cell, a series of experiments have been carried out on the typical difficult-to-process material 30CrNiMo8. The experimental results show that compared with the conventional micro-drilling (CMD), the burr of the hole is well suppressed in the UAMD process, and the height of the burr is reduced by about 27.3 %. The manufactured micro-hole exit burr is relatively neat. While in CMD, the exit burr is deformed greatly, the fracture is obvious, and the exit thrust force is generally larger than that in UAMD.

Research on Microhole Processing Technology Based on the Femtosecond-Laser Spiral Trepanning Method

Microholes have crucial applications in aerospace, the automotive industry, and other industries. In this study, the microhole processing technology based on the femtosecond-laser spiral trepanning method was investigated. By adjusting the spiral scanning path, laser power distribution, and defocusing amount to control laser energy distribution, an inverted cone hole, straight hole, and normal cone hole were obtained finally. The morphology and element of the microhole were investigated by scanning electron microscopy (SEM) equipped with energy-dispersive X-ray spectroscopy (EDX). The experimental results of the femtosecond-laser spiral trepanning method could achieve fewer impurities. Finally, the formation mechanisms of different microholes are explained in detail. The method is simpler and more efficient than the traditional microhole processing technology. The femtosecond-laser spiral trepanning method with controllable hole roundness, accuracy, and taper has important practical significance in microhole processing.

Positioning and navigation system based on machine vision intended for laser-electrochemical micro-hole processing

In order to improve efficiency and quality of micro-hole processing, a laser-electrochemical micro-hole processing is applied to the micro-hole processing of aero engine blade, i.e., laser drilling and electrochemical machining are performed. However, when electrode wire is inserted into micro-hole, due to the positioning error, it can collide with blade, which could result in short circuit or electrode wire damage. Hitherto, the positioning of electrode wire and micro-hole was achieved by artificial observation, but its efficiency is low, especially for micro-holes with small diameter. Namely, a large amount of asymmetric micro-holes is produced due to the low-accuracy positioning by artificial observation; therefore, machining accuracy and consistency of micro-hole cannot be guaranteed. In this study, a positioning and navigation system based on machine vision is applied for the first time to the laser-electrochemical micro-hole processing. The proposed system is based on parallel installation of camera and electrode wire. A novel hand-eye calibration method, wherein rotation angle and translation vector are calibrated step by step, is proposed for the case when electrode wire is beyond the view area of camera. The tree traversal binary image boundary tracking algorithm is adopted to image processing. The data stem definition is proposed to detect micro-hole edge with burrs. Before electrochemical machining, the micro-hole image is captured by camera that is navigated to the micro-hole top, and then, the captured image is processed in order to get the coordinates of micro-hole center, which enables navigation of electrode wire to the micro-hole center; thus, the accurate positioning and navigation of micro-hole are achieved.

マイクロニードルアレイを用いた高品位・高能率マイクロ穴加工技術の開発（第4報）

マイクロニードルアレイを用いた高品位・高能率マイクロ穴加工技術の開発（第4報）

Vibration Drilling the 0Cr18Ni9Ti Stainless Steel Micro-Hole

Austenite 0Cr18Ni9Ti stainless steel is one of difficult-to-cut materials. It has poor dilling process, especially for micro-hole machining. The main reasons are the tiny drill, poor rigidity, easy to deviation. Moreover, the chip is difficult to discharge, so the drilling force is increased and the drill bit is easy to break, or even it is impossible for micro-hole drilling. In this paper, the vibration drilling process is adopted. The vibration drilling 0Cr18Ni9Ti stainless steel micro-hole process mechanism is researched. The stainless steel micro-hole drilling experiments are conducted. The results show that the vibration drilling can be a better solution for 0Cr18Ni9Ti stainless steel micro-hole processing.

Research on Vibration Drilling 1Cr18Ni9Ti Stainless Steel Micro-Hole

The austenite 1Cr18Ni9Ti stainless steel is one of difficult-to-cut materials. It has poor dilling process, especially for micro-hole machining. The main reasons are the tiny drill, poor rigidity, easy to deviation. Moreover, the chip is difficult to discharge, so the drilling force is increased and the drill bit is easy to break, or even it is impossible for micro-hole drilling. In this paper, the vibration drilling process is adopted. The vibration drilling 1Cr18Ni9Ti stainless steel micro-hole process mechanism is researched. The stainless steel micro-hole drilling experiments are conducted. The results show that the vibration drilling can be a better solution for 1Cr18Ni9Ti stainless steel micro-hole processing.

マイクロニードルアレイを用いた高品位・高能率マイクロ穴加工技術の開発（第3報）

マイクロニードルアレイを用いた高品位・高能率マイクロ穴加工技術の開発（第3報）

Finite Element Simulation for Micro-Hole Processing with Millisecond Laser

In this paper, ANSYS, a finite element analysis software is used to simulate the change of temperature field in micro-hole processing with millisecond laser, which determines the diameter and depth of the hole drilled. The relationship between processing parameters and the hole size is plotted, so as to achieve size control of a micro-hole processing. Compared with experimental results, simulation is effective for laser processing of micro-hole and can be referenced to choose the best processing parameters.

Finite Element Simulation for Micro-Hole Processing with Millisecond Laser

In this paper, ANSYS, a finite element analysis software is used to simulate the change of temperature field in micro-hole processing with millisecond laser, which determines the diameter and depth of the hole drilled. The relationship between processing parameters and the hole size is plotted, so as to achieve size control of a micro-hole processing. Compared with experimental results, simulation is effective for laser processing of micro-hole and can be referenced to choose the best processing parameters.

E-Beam Processing Technology and the Application in Micro-Hole Process

It is very difficult ot process the micro-deep hole, especially the hole made of hard guilder alloy, heat resisting alloy by classical machine method. The E-beam processes which make use of the high energy of e-beam can manufacture lots of micro-deep hole and abnormal shaped hole constituted of hard-transformed materials. The process of high-efficiency and high-definition can be obtained by selecting processing-parameters correctly and reasonably.

マイクロニードルアレイを用いた高品位・高能率マイクロ穴加工技術の開発（第１報）

マイクロニードルアレイを用いた高品位・高能率マイクロ穴加工技術の開発（第１報）

マイクロニードルアレイを用いた高品位・高能率マイクロ穴加工技術の開発（第2報）

マイクロニードルアレイを用いた高品位・高能率マイクロ穴加工技術の開発（第2報）