Micro-hole Drilling Process Research Articles

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

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.

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.

Experimental and numerical studies of electrolyte concentration effect in electrochemical discharge based micro-drilling

Electrochemical discharge based micro-drilling (ECDD) is a hybrid machining process that involves the thermal heating of the sparks and etching action of the electrolyte for material removal mechanism. The concentration of the electrolyte plays a vital role in determining the material removal rate (MRR) during the micro-hole drilling process since a higher depth is desired. Despite numerous experimental studies, the reporting of numerical studies concerning the effect of electrolyte concentration on MRR is still scarce. The present article focuses on the development of a finite element based thermal model for studying the MRR of glass material concerning electrolyte concentration. The model is validated using previously reported as well as present experimental studies. MRR is observed to be in fair agreement with the experimental MRR. Results revealed that the MRR improves with the increase in electrolyte concentration due to the increase in the imported heat flux over the work material. MRR improvement is the combined result of an increase in thermal energy as well as an increase in hydroxide (OH) ions that further enhances the chemical etching action. The present study successfully demonstrates the application of numerical aspects for analyzing the MRR in the ECDD process concerning electrolyte concentration.

Numerical and experimental investigations to analyze the micro-hole drilling process in spark-assisted chemical engraving (SACE)

With the increased utilization of glass in micro-electromechanical systems (MEMS) applications, need is generated to produce micro-features on glass with excellent surface quality, i.e., better hole circularity and less thermal cracks. Spark-assisted chemical engraving (SACE) has proven to be an emerging and reliable technology for micro-machining of glass that includes local joule heating of the work material for its removal. However, some problems need to be covered in the micro-hole drilling process such as low machining depth, low aspect ratio, high thermal cracks, and an increase in machining time with the increase in depth. Moreover, few finite element modeling (FEM) studies have been reported to analyze the material removal aspects in SACE. This present study developed the FEM-based thermal model to analyze the material removal rate (MRR) and investigated the different machining conditions to improve the micro-hole drilling process in SACE. Improvement in depth and aspect ratio can be achieved by using a different tool’s shape which variably enhances the flow of electrolytes and thereby increases the formation rate of gas film. Pointed and cylindrical tools were used for micro-drilling operations. MRR, hole entrance diameter, machining depth, aspect ratio, thermal cracks, and machining time were observed under different machining conditions. FEM study revealed that MRR improves with the increase in both the applied voltage and electrolyte concentration. The MRR was predicted by utilizing the plots of temperature distributions and was found in accordance with the experimental results of MRR. The experimental study concluded that the pointed tool produced micro-holes with a higher machining depth and aspect ratio at an improved machining rate, while the cylindrical tool produced micro-holes with a smaller number of thermal cracks and better circularity.

Multi-Response Optimization of ECDM Parameters for Silica (Quartz) Using Grey Relational Analysis

Electrochemical discharge machining (ECDM) has successfully demonstrated the micro-machining of pioneering engineering materials, regardless of their properties such as glass, quartz, silicon nitride ceramics, composites, etc. Yet numerous intrinsic challenges are there that should be addressed during the micro-hole drilling process with ECDM such as low material removal rate (MRR), high area of the heat-affected zone (HAZ), high hole tapering (HT), high radial overcut (ROC) and circularity error (CE). However, the determination of the input parameters’ optimum level for multi-response parameters is still a strenuous work. This present study investigates the machining performance of the ECDM process during the machining of silica (Quartz) through establishing the optimum combination of the level of the parameters for multi-response parameters. MRR, HAZ, HT, ROC, and CE were picked as response parameters. Experiments were performed in consonance with Taguchi’s L9 orthogonal array and response measurements were analyzed through Grey Relational Analysis (GRA) to identify the optimum levels of input process parameters for their combined fusion i.e. maximum MRR, minimum HAZ, minimum HT, minimum ROC, and minimum CE. Results exhibited that electrolyte concentration (wt.%) is the utmost governing input parameter followed by applied voltage (V) and inter-electrode gap ((IEG), mm) for controlling the multi-response parameters simultaneously. GRA optimized parameters were determined as 35 V, 15 wt.%, and 25 mm with 68.34% contribution only from the electrolyte concentration. Based on experimental investigation, micro-holes were successfully drilled on Silica (quartz) material with the success of the utilized method to assess the machining performance of the electrochemical discharge machining process.

Characteristics of micro-hole formation during fibre laser drilling of aerospace superalloy

High aspect ratio micro-holes are nowadays increasingly used in various applications including aerospace, medical and automotive. This research investigates the characteristic of quasi-CW fibre laser micro-hole drilling (∼100 μm) of nickel superalloy using experimentation and numerical modelling. Micro-holes of diameter around 100 μm was drilled using percussion technique over a 2 mm thick nickel superalloy material. The main investigation focuses on understanding the micro-hole formation during the laser interaction with the material. Finite element modelling tool and high-speed imaging camera had been used to assist in understanding the basic-fundamentals of micro-hole formation during the millisecond laser drilling process. During the micro-hole drilling process, irrespective of the laser parameters, the melt ejections start after around 80 μs, and the total melt ejection duration depends on laser energy and pulse duration. The experimental results showed that it takes 15 ms to drill a micro-hole of diameter around 100 μm using a laser pulse duration of 0.1 ms, laser pulse energy of 1 J and 15 number of percussion pulses.

Chip Discharge Performance of Micro-Hole Drilling through a Glass Plate using an Electroplated Diamond Tool with Different Drill Bits

This research aims to identify a high-quality, efficient, and low-cost micro-hole drilling process through glass plates that employs an electroplated diamond tool with different drill bits. Three different drill bits were tested to determine how varying the chip discharge volume influences chip discharge performance, which is an important factor that affects the effectiveness of the drilling process. The chip discharge performance of each electroplated diamond tool was experimentally investigated by observing the drilling quality and the number of the drilled holes. From the experimental results, it was found that the drilled chips could not discharge smoothly when the drill bit possesses a small chip discharge volume, leading to the drill bit breaking, which thus limits the number of drilled holes. Furthermore, the changes in thrust force and the crack size were high, and there were also cracks on the drilled glass plate. However, drilling with a drill bit that possesses a larger chip discharge volume resulted in excellent chip discharge performance and increased the number of drilled holes. This type of drill bit is effective in drilling holes through glass plates, with minimum hole defects and no issues associated with chips clogging the hole during drilling.

Effect of machining parameter on femtosecond laser drilling processing on SiC/SiC composites

Due to the unique properties of femtosecond laser in precision machining, femtosecond laser was utilized for irradiation on SiC/SiC composites. Effects of different processing parameters, including the spot overlap ratio, helical line overlap ratio, laser processing power, as well as processing steps, were discussed in detail. The results indicated that the parameters above had significant effect on machining of SiC/SiC composites. The surface morphology and geometry of the micro-holes were investigated under different parameters, and the corresponding formation mechanism was discussed in detail. It was believed that both the spot and helical line overlap ratio had great effect on the quality of the micro-holes and would be responsible to the depth of micro-holes. Besides, it is indicated that the higher processing power will lead to a better quality of surface morphology and machining results. In micro-hole drilling process, debris and fragments were observed within the micro-holes, and XPS analysis showed that there existed Si-O bonds and Si-C bonds, indicating that the oxidation during processing was incomplete. In addition, the effect of feeding speeds on geometry and depth of the micro-holes were discussed as well.

Effect of different parameters on machining of SiC/SiC composites via pico-second laser

Pico-second laser plays an important role in modern machining technology, especially in machining high hardness materials. In this article, pico-second laser was utilized for irradiation on SiC/SiC composites, and effects of different processing parameters including the machining modes and laser power were discussed in detail. The results indicated that the machining modes and laser power had great effect on machining of SiC/SiC composites. Different types of surface morphology and structure were observed under helical line scanning and single ring line scanning, and the analysis of their formulation was discussed in detail. It was believed that the machining modes would be responsible to the different shapes of machining results at the same parameters. The processing power shall also influence the surface morphology and quality of machining results. In micro-hole drilling process, large amount of debris and fragments were observed within the micro-holes, and XPS analysis showed that there existed Si–O bonds and Si–C bonds, indicating that the oxidation during processing was incomplete. Other surface morphology, such as pores and pits were discussed as well.

Experimental characterization of a micro-hole drilling process with short micro-second pulses by a CW single-mode fiber laser

Laser ablation with pulse durations in a few microseconds is a viable solution for micro-hole drilling applications which require large material removal rate (MRR) with moderate hole quality. However, the body of work regarding short microsecond laser drilling/ablation is small. The objective of this paper is to experimentally characterize this short micro-second laser micro-hole drilling technique using a 300W, CW, single-mode fiber laser. This CW fiber laser is controlled to produce modulated pulses from 1μs to 8μs and these modulated laser pulses have a unique profile which contains an initial spike with a peak power of 1500W for 1μs, followed by the steady state power of 300W. Because of its excellent beam quality, the laser beam produced by this fiber laser can be focused to a small spot size of 10μm to achieve very high power density up to 1.9GW/cm2. With one single laser pulse at approximately 1μs, a blind hole of 167μm in depth and 23μm in opening diameter can be created in a stainless substrate. The experimental characterization of this micro-hole drilling process includes laser control, laser beam characterization, hole formation, photodiode measurements of the vapor intensity, high-speed photography of vapor/plasma formation, and spectroscopic measurements of plasma. The results show that, due to very high irradiance of the fiber laser beam, the absorbed energy not only is sufficient to melt and vaporize the material, but also is able to dissociate vapor into intense plasma at temperatures over 16,000K. The hole drilling mechanism by this short microsecond laser ablation is due to a combination of adiabatic evaporation and ejection of fine droplets.

Process Anatomy for High Aspect Ratio Micro-Hole Drilling with Short Micro-Second Pulses Using a CW Single-Mode Fiber

The objective of this paper is to establish a detailed process anatomy of a micro-hole drilling process using a CW single-mode 300 W fiber laser with short micro-second pulses. For the drilling process with a one micro-second laser pulse, the process started with drastic evaporation and concluded with melt ejection approximately 150 micro-seconds later. It was concluded that two distinct hole drilling mechanisms occurred, one as adiabatic evaporation by the high power initial spike of the laser beam and one as melt ejection by the low power laser energy deposition. The drilling process time line was established based on the measurements by several in-process sensors, such as photodiodes, a high-speed camera, and a spectrometer. The theoretical modeling zoomed in the early stage of the process to investigate the hole formation which could not be observed experimentally. Both experimental and theoretical results were then compared to determine the laser-material interaction mechanisms among three media involved in the process: laser, material, and vapour/plasma. Finally, a series of temporal anatomy diagrams, denoted as process anatomy, were presented to describe the entire drilling process, including process temperature, laser energy deposition, hole formation, and material removal mechanisms.

FEA of Micro-Hole Drilling in Stainless Steel Based on DEFORM-3D

In order to better understand the micro-hole cutting processes in stainless steel, the cutting process of 1Cr18Ni9Ti stainless steel was modeled and simulated by FEA (Finite Element Analysis) based on DEFORM-3D software. The influence of rotation speed and feed speed on the thrust force and torque of 1Cr18Ni9Ti stainless steel were analyzed. Meanwhile, the comparisons of simulated results and theoretical calculation results were taken into consideration. It is found that the simulation data from DEFORM-3D agreed well with the theoretical calculation results. It confirms that the results of simulation based on DEFORM-3D have a high level of reliability. The findings of the present study provide a new way to systematically investigate the stainless steel micro-hole drilling process.

Modeling and Experimental Investigation of Jet Electrolytic Drilling

Jet Electrolytic Drilling (JED) is a micro-hole drilling process, which employs a jet of electrolyte for anodic dissolution of workpiece material and does not require entry of a nozzle into the machined hole. JED has been used for drilling small holes in aerospace, electronic, and micro-mechanics. One of the most significant problems on JED is the precise control and parameters optimization of the process. This paper established a two-dimension mathematical model for JED to describe the shape of the drilled hole. The model was validated by comparison of simulation and experimental result. JED experiments were performed on 0.6mm thickness stainless steel sheets with different parameters including nozzle diameter and operating voltage. It is found that JED is suitable for drilling micro-holes with diameter less than 1mm and the operating voltage should better be more than 120V.