Micro-hole Drilling Research Articles

EDM-Grinding composite machining and drilling of polycrystalline diamond tool

ABSTRACT Polycrystalline diamond (PCD) is widely used for micro tools due to its high hardness and wear resistance. However, micro PCD tools face challenges in machining with high accuracy and efficiency. Therefore, electrical discharge machining grinding (EDM-grinding) composite machining was proposed. The effects of pulse discharge parameters on surface quality and microhole drilling performance of PCD tool were investigated. The results show that the surface roughness of helix flute and flank face of the fabricated PCD tool were 0.125 µm and 0.158 µm, respectively, as well as the inner wall roughness achieved 0.331 µm after drilling of microhole. The average current displayed a greater effect on the machining quality of PCD tools, with tool breakage in excessive average current. The preferred pulse discharge parameters were determined as an open-circuit voltage of 95 V, an average current of 1400 mA, a pulse width of 400 ns, and a pulse interval of 2000 ns.

Study of micro-hole pecking drilling process for high volume fraction SiCp/Al7075 composites

Study of micro-hole pecking drilling process for high volume fraction SiCp/Al7075 composites

Experimental Investigation of Water Jet-Guided Laser Micro-Hole Drilling of Cf/SiC Composites.

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.

Novel Approach to Color‐Neutral Transparent Solar Cells: An Organic‐Si Hybrid Achieved by Laser Microhole Drilling

AbstractTransparent solar cells (TSCs) hold promise for applications in building‐integrated photovoltaics (BIPVs) and vehicles. However, existing TSCs often have compromised color neutrality and efficiency because of the distinctive colors arising from their photoactive materials. The study proposes a novel fabrication method for TSCs based on Si wafers with the average visible transmittance (AVT) controlled by creating a microhole pattern through a combination of nanosecond laser drilling and subsequent wet etching. Through this ambient‐air process, organic–Si hybrid TSCs are successfully realized by integrating an organic PEDOT:PSS layer onto this structure with a neutral color. The power conversion efficiency (PCE) is adjusted by the fraction of the perforated region, and it attained 6.20% at 30% AVT, 5.37% at 40% AVT, and 4.67% at 50% AVT. In this hybrid TSC approach, the CIE color coordinates are closely aligned with the neutral‐color points (0, 0), resulting in color rendering index (CRI) values exceeding 99. The strategy represents a significant step toward the development of efficient color‐neutral TSCs for transparent solar applications.

Process in laser drilling of deep microholes without taper on metal materials

Process in laser drilling of deep microholes without taper on metal materials

Electrochemical micromachining on nickel and nickel-based superalloys with two-tone sinusoidal signal

Electrochemical micromachining is an emerging technology in the machining field. This method offers several advantages such as exceptional surface quality, minimal cathode depletion, and a high elimination rate. Often, an ultrashort pulse power supply is employed in electrochemical micromachining to address over-machining in non-processing areas. While reducing the pulse duration can enhance processing accuracy, its high cost and impracticality for regular production limit its development. This paper presents the use of a Two-tone sinusoidal signal as an alternative to ultrashort pulse in electrochemical micromachining. We investigated the mechanism behind the reduced machining gap with this signal. By drilling micro-holes in the nickel sheet to optimize parameters such as voltage, fundamental frequency, and harmonic order. Using the Taguchi optimization method, we studied the impact of these control variables on the micromachining process during micro-hole drilling. The study also focused on fabricating micro-structures using the best processing parameters. Our results showed that using the optimized parameters greatly enhanced processing accuracy. Moreover, we found that high machining accuracy could be achieved when working on hard-to-cut super alloy plates.

Scheduling Optimization of Printed Circuit Board Micro-Hole Drilling Production Line Based on Complex Events

The interdependence between the scheduling method and the production efficiency of a micro-hole drilling production line for printed circuit boards (PCBs) holds significant importance, necessitating the optimization of such a production line’s scheduling. Consequently, this research paper presents a scheduling optimization approach for the micro-hole drilling production line of a PCB, utilizing complex events as its foundation. Initially, a complex event model was constructed to establish correlations among extensive production line data. Subsequently, the typical complex events associated with the micro-hole drilling production line of a PCB were defined, thereby enabling the all-around monitoring of the operation state of such a production line. Furthermore, this study presents the establishment of a production scheduling model for PCB micro-hole drilling. With the goal of minimizing the maximum completion time, the catastrophe genetic algorithm was used to solve the initial scheduling scheme of the printed circuit board micro-hole drilling production line. The reliability and effectiveness of the catastrophe genetic algorithm in solving the hybrid-driven production scheduling problem of complex events were verified. Dynamic scheduling was performed when three complex events occurred in the production line: emergency order insertion, abnormal equipment operation, and tool failure. The scheduling optimization rate after identifying the emergency insertion event could reach 25.1%. The scheduling optimization rate of the production equipment operation event was related to the specific failure time of the equipment. The scheduling optimization rate after identifying the tool failure event could reach 25%. Rescheduling immediately after identifying the tool failure event could exert no effect on the initial scheduling process. It was proven that the identification and rescheduling of complex events can improve the production efficiency of a PCB micro-hole drilling production line.

An analysis to enhance the machining performance of micro-EDM for drilling of blind micro-hole using ANN

An analysis to enhance the machining performance of micro-EDM for drilling of blind micro-hole using ANN

A Comprehensive Review of Fishbone Well Applications in Conventional and Renewable Energy Systems in the Path towards Net Zero

Fishbone drilling (FbD) involves drilling multiple micro-holes branching out in various directions from the primary vertical or deviated wellbore. FbD is similar to multilateral micro-hole drilling and can be employed to boost hydrocarbon production in naturally fractured formations or during refracturing operations by connecting existing natural fractures. Key design elements in fishbones include determining the number, length, and spacing between the branches, and the angle at which the branches deviate from the main borehole. Fishbone wells have emerged as a promising technology for improving well performance and reducing environmental impact. In this paper, we present a comprehensive review of the different applications of fishbone wells in conventional and renewable energy systems. We discuss the potential of fishbone wells for enhanced oil and gas recovery, as well as their application in unconventional resources such as coal bed methane. Moreover, we examine the feasibility of fishbone wells in renewable energy systems, such as geothermal energy and carbon capture, utilization, and storage (CCUS). We highlight the various benefits of fishbone wells, including reduced carbon footprint, enhanced efficiency, and increased sustainability. Finally, we discuss the challenges and limitations associated with fishbone wells in different energy systems. This review provides a comprehensive overview of the potential and challenges of fishbone wells in reducing carbon footprint and improving well performance in a wide range of energy systems.

Self-adaptive micro-hole breakout detection in the electrochemical discharge drilling process based on CNN-BiLSTM

Electrochemical discharge machining (ECDM) is an effective and promising technology for the micro-hole drilling of hard and brittle insulating materials such as glass, quartz and ceramics. Hole exit quality is an important part of through-hole machining quality in ECDM. The hole exit quality is influenced by two different machining states before and after the hole breakout. Therefore, it is necessary to identify hole breakout occurrence to provide a basis for achieving a machining strategy that matches the changing machining state and thus improves the hole exit quality. However, currently, there is no effective method to detect the hole breakout in the ECDM of micro-holes. In this paper, a self-adaptive micro-hole breakout detection method based on CNN- BiLSTM was proposed. The hole breakout detection can be expressed as a binary classification problem according to the analysis of the current signals collected before and after the hole breakout. The sufficiency of the raw current signal information was discussed. A CNN-BiLSTM model was established to detect hole breakout using the current signals as the training dataset. The CNN-BiLSTM model showed better performance compared to CNN, LSTM, BiLSTM and CNN-LSTM by comprehensive considering of accuracy, F1 score, AUC value, training time, predict time, breakout detection results and Dunn test results. Furthermore, the length of current signals used for each single detection and the threshold value used for breakout detection were discussed. An optimal threshold value was calculated, and the delay of detection was within 66 ms. The proposed method was successfully applied to the hole breakout detection in the through-hole drilling experiments and the success rate was 100 %. The hole exit area just after breakout were measured and compared to the hole exit area after hole completion, the average ratios of the former to the latter were 11.69 %, 27.29 %, 38.43 % and 44.41 % for the voltage of 39 V, 41 V, 43 V and 45 V respectively.

Investigation on Thermal Barrier Coating Damages for Ultrafast Laser Drilling of Cooling Holes.

To mitigate the challenges pertaining to coating damage and processing defects arising from the utilization of ultrafast laser drilling for microhole creation in thermal barrier coatings (TBCs), thereby exerting substantial influence on the long-term durability of these microholes, the investigation proposes a comprehensive methodology. It encompasses the design of a two-factor four-level full factorial experiment and the execution of experimental research on picosecond laser drilling of TBC microholes. By meticulously analyzing the morphology of the microholes and the coating interface, the damage mechanisms associated with picosecond laser drilling of TBC microholes, as well as the influence of laser process parameters on coating damage, are revealed. The findings reveal that the optimal microhole entrance quality and the lowest roughness along the hole perimeter are attained at a laser power of 12 W and a scanning speed of 320 mm/s. Moreover, at a laser power of 30 W and a scanning speed of 320 mm/s, the minimal crack length on the blunt angle side of the hole and the highest machining quality are observed.

Mechanism investigation of micro-drill fracture in PCB large aspect ratio micro-hole drilling

Mechanism investigation of micro-drill fracture in PCB large aspect ratio micro-hole drilling

Simulation Research on Variable Parameter Drilling of Glass Fiber Reinforced Composite / Copper Foil Laminates

Micro-holes play an important role in interconnecting different signal layers of printed circuit boards(PCBs), and their surface quality is critical to signal transmission performance. As an important parameter, drilling force affecting the quality of micro-holes, but its distribution is difficult to obtain because the size of micro-holes is tiny and the drilling process is usually in a semi-closed state. Therefore, simulation of the micro-hole drilling process is studied by Abaqus in this paper. The material of printed circuit board can be regarded as laminated material composed of glass fiber composite and copper foil. The whole simulation process is the simulation of alternating drilling of the two materials. Via simulation, the influence of different drill parameters and processing parameters on the output drilling stress, axial force and drilling quality is obtained, and the results are consistent with the experimental results in the literature. This simulation method can be used as a supplement to the experiment and can provide guidance for the drilling process of printed circuit boards.

Inlet Hole Shape Analysis Depending on the Focus Conditions for Electron Beam Micro-hole Drilling

Inlet Hole Shape Analysis Depending on the Focus Conditions for Electron Beam Micro-hole Drilling

On the performance analysis of micro-hole drilling using magnetic field-assisted electrochemical spark machining

On the performance analysis of micro-hole drilling using magnetic field-assisted electrochemical spark machining

A Micro EDM-based experimental study of surface texture on stainless steel 316 micro machined holes

In Micro-EDM, micro-electro erosion makes it possible to machine micro-holes on stainless steels in a most economical way being conductive towards both thermal energy as well as electrical energy. This article focuses on a new technique to refine the surface texture of stainless steel grade 316 by utilizing the multi-diameter electrode. This procedure involves two processing steps that are completed sequentially on the same machine tool using a common electrode. As a first step, the micro-hole is drilled by micro-electrode using the front of the constant voltage multi-diameter electrode and pulse times. Later, the large diameter portion of the multidiameter electrode is used to improve the surface quality of the micro-hole by maintaining the same voltages and pulse durations. The characteristics of the surface texture of micro holes were measured using a Transmission Electron Microscope (TEM). The results suggest that employing a multi-diameter electrode at given voltage and pulse durations without modifying the drilling time improves surface quality. It demonstrates that this innovative technology is feasible and beneficial in the field of stainless steel 316 micro-hole drilling.

Investigation of precession laser machining of microholes in aerospace material

Sidewall tapering is one of the main limitations in ultrashort pulse (USP) laser machining and is associated with the beam shape and self-limiting effect. Laser processing with a precession beam is a potential solution to overcome this limitation. A study into the effects of precession parameters on the taper angle in microhole drilling of a nickel alloy is reported in this paper. The effects of three key precession parameters, i.e., incident angle, relative distance between the focuses of the precession and individual beams, and scanning speed, have been investigated in detail. Experiments were performed to drill through holes with aspect ratios up to 20:1 and diameters ranging from 100 to 500 μm over 0.6–2 mm thick nickel alloy substrates. Experiment results showed that all the considered parameters/factors were significant and affected the hole tapering in different ways. In addition, there were important interaction effects between two of the factors, i.e., incident angle and focus position, in some cases. The optimal parameters to minimize the tapering effect are suggested, and the mechanism is discussed in detail. The precession laser machining showed clear advantages in overcoming the limitations to associated with conventional USP laser machining. Fabricating microholes with high geometrical accuracy, i.e., with straight side walls and zero taper angles, is feasible with the use of a precession beam. The results clearly show the potential of precession laser processing and the capabilities that the technology can offer for a range of laser micromachining applications in different industries, such as microelectronics, automotive, and aerospace.

Applications of Underbalanced Fishbone Drilling for Improved Recovery and Reduced Carbon Footprint in Unconventional Plays

Fishbone Drilling (FbD) consists of drilling several micro-holes in different directions from the main vertical or deviated wellbore. Similar to multilateral micro-hole drilling, FbD may be used to enhance hydrocarbon production in naturally fractured formations or in refracturing operations by interconnecting the existing natural fractures. When combined with underbalanced drilling using a coiled tubing rig, FbD enhances the production further by easing the natural flow of the hydrocarbon from the reservoir to the wellbore. The design aspects of the Fishbones include determining the number, length, distance between the branches, and the angle of sidetracking of the branches from the main borehole. In addition, the design of efficient drill string components to suit the FbD conditions are another important design aspect in FbD technology development. Examples of this include a high-performance small, diameter downhole motor and the use of High Voltage Pulsed Discharge (HVPD) plasma shock waves at different pulse frequencies and wave pressures to impose shear forces on the formation to break it more easily. This paper will present a comprehensive review of the FbD technology, including some of its current applications and design aspects. The possibility of using FbD in conjunction with hydraulic fracturing to boost production by creating a network of connected fractures will be discussed, and some of its technical and economic benefits and challenges will be compared

Optimization of CO<sub>2</sub> Laser Parameters for Hole Micro Drilling of PMMA: An Experimental and Theoretical Study

Motivated by a desire to improve hole quality during drilling Polymethyl methacrylate (PMMA) samples using a continuous CO2 laser. This research presents a theoretical and experimental investigation to optimize input parameters of laser drilling such as laser power and exposure time for different thicknesses 1-3 (mm). Hole quality characteristics such as depth, inlet diameter, and heat affected zone (HAZ) were considered process results and examined with a microscope. Design Expert software has been used to get a detailed understanding of a laser drilling process owing to the confluence of multiple factors that impacts the results. depending on the Box Behnken Design (BBD) of tests software; 17 experiments were applied to explore the effect of laser factors on the micro-hole drilling process. Statistical analysis technique (ANOVA) was used to study the influence of laser drilling process factors including power, exposure time of different thicknesses on HAZ, depth, and entrance diameter. Quadratic regression models were employed to model the processing of many hole variables. Experiments were optimized using the defined goal model as a function to get the optimal hole. The data received were confirmed using verification tests, and a considerable increase in hole quality was realized. The proposed technique is perfect for reducing the HAZ and entrance hole diameter for the ideal depth hole. The laser parameters were changed in different combinations of 2-6 (W) power and 0.1- 0.3 (s) exposure duration, on the various thickness. The obtained values indicated that raising the drilling parameters increases the depth, entrance diameter, and HAZ. The sample thickness has a great impact on hole characteristics; increasing the sample thickness reduces the inlet diameter, and heat-affected zone (HAZ); increasing the thickness leads to an increase in hole depth. The results showed that the highest depth of 1mm thick was 0.99(mm) with 437(µm) diameter and 85(µm) HAZ. 1.9(mm) depth with 435(µm) diameter and 32(µm) HAZ was obtained at 4.99(W) and 0.1(s) on 2(mm) thickness. while as in 3(mm) thick, depth is equal to 2.8(mm), 472(µm) diameter, and 20(µm) HAZ was attained. COMSOL Multiphysics 5.6 software was used to apply virtual experiments and obtain the ideal conditions from the parameters' combination that improves the quality of the hole, which is the main goal of this research. Which is in good agreement with the test results. The findings and procedure of this research have not been presented elsewhere.

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.