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We investigate the elongated modifications resulting from a Bessel beam-shaped femtosecond laser in fused silica under three different operation modes, i.e., the single-pulse, MHz-burst, and GHz-burst regimes. The single-pulse and MHz-burst regimes show rather similar behavior in glass, featuring elongated and slightly tapered modifications. Subsequent etching with Potassium Hydroxide exhibits an etching rate and selectivity of up to 606 μ m/h and 2103:1 in single-pulse operation and up to 322 μ m/h and 2230:1 in the MHz-burst regime, respectively. Interestingly, in the GHz-burst mode, modification by a single burst of 50 pulses forms a taper-free hole without any etching. This constitutes a significant result paving the way for chemical-free, on-the-fly drilling of high aspect-ratio holes in glass. [ABSTRACT FROM AUTHOR]

The rising applications of hybrid composites demand the best manufacturing quality solutions. This article uses a newly developed hybrid composite material of carbon, basalt and Kevlar-29 woven fibres manufactured for laser drilling operation for its characterization and optimization using a golden jackal optimizer. The Nd: YAG laser parameters used are lamp current (LC), pulse width (PW), stand-off distance (SoD) and compressed air pressure (CAP). The responses considered for this work are hole taper angle (HT) and average overcut (AvgOC). The experimental set was designed through the Box–Behnken design. Optimization has been carried out using the Golden Jackal optimizer. Optimized responses are theoretically obtained and validated with the confirmation experiment as LC = 220 A, PW = 3 ms, SoD = 1.1 mm and CAP = 12 kg/cm2. Whereas predicted and experimental values of HT and AvgOC are recorded as 0.113° and 0.125° and 0.066 and 0.098 mm, respectively. The confirmatory experiment yielded a good agreement with the predicted responses. [ABSTRACT FROM AUTHOR]

Drilling cooling holes on the turbine blade is essential for enhancing aero engine performance and to protect it from elevated temperature. So, the objective of this work is to produce micro holes on the thermal barrier coated titanium alloy using a femtosecond laser. An in-depth experimental investigation has been carried out to understand the influence of femtosecond laser parameters, circular and zig-zag scanning modes on geometrical characteristics and surface integrity of the micro holes. It is inferred that better hole circularity and less taper angle are observed for circular scanning method at laser energy density (LED) of 2.04 J/cm2, pulse repetition rate (PRR) of 20 kHz, and scanning speed of 300 mm/s. The surface finish and hole quality are also improved by this method, although at higher LED and PRR the inner hole wall surface degrades because of flaws including microcracks, re-solidified material, and micropores. When compared to circular scanning, the zig-zag scanning strategy reduces the drilling time by 51.87%. Conical spike with micro protrusion and micro trench type microstructure, is noticed for the zig-zag path. In contrast, micropores with micro protrusion type microstructures are obtained for concentric path with minimal surface flaws. [ABSTRACT FROM AUTHOR]

Abstract\nHighlightsThis research investigates the fatigue behavior of multi-row film cooling holes produced by lasers with diverse pulse widths amid intricate thermal environments. Through laser drilling experiments, conjugate heat transfer simulations, and crystal plasticity finite element analyses, it explores the interplay of temperature and stress fields among multiple holes in these structures, and factors influencing fatigue damage and its severity. Additionally, it anticipates the fatigue fracture paths of multi-row film cooling hole structures. Findings reveal that while the drilling process and aerodynamic parameters significantly impact cooling effectiveness, their influence on cooling distribution is negligible. Fatigue damage distribution is shaped by structural imperfections from different processes, stress field interference among multiple holes, and material property alterations due to temperature changes. The extent of damage is primarily dictated by roundness errors resulting from the drilling process, with taper playing a minor role. Nonetheless, stress interference among multiple holes notably exacerbates stress concentration at the interference zone, leading to increased damage levels in film cooling holes crafted by picosecond lasers with minimal roundness errors. Moreover, in complex thermal environments, fatigue fracture paths of multi-row film cooling holes migrate and evolve contingent on temperature-induced shifts in material properties.Through laser drilling experiments, conjugate heat transfer simulation, and finite element analysis of crystal plasticity, an innovative combination of drilling process, real flow field, temperature field, and hole arrangement under actual working conditions was achieved. The fatigue behavior of multi-row film cooling holes manufactured by lasers with different pulse widths under complex temperature fields were analyzed.Explored the fatigue damage factors of multi-row film cooling holes manufactured by lasers with different pulse widths under complex temperature fields, revealing the influence of the thermo-mechanical coupling mechanism on the fatigue behavior of the film cooling holes.Analyzed the interference between temperature field and structural field, and predicted the fatigue fracture paths of multi-row film cooling holes manufactured by lasers with different pulse widths under complex temperature fields. [ABSTRACT FROM AUTHOR]

Carbon fiber-reinforced polymer (CFRP), known for its light weight, high strength, and corrosion-resistant properties, is extensively used in the lightweight design of satellite components, the optimization of electronic device casings, and the processing of high-performance composite materials in the defense sector. This study employs picosecond laser drilling technology for the precision machining of CFRP, demonstrating its advantages over traditional mechanical drilling and other unconventional methods in significantly reducing the heat-affected zone (HAZ) and enhancing hole wall quality. The optimization of laser power, scanning speed, and fill times via response surface methodology (RSM) significantly reduced the hole wall taper to 4.160° and confined the HAZ to within 18.577 μm, thereby enhancing machining precision. The actual test results show that the deviations in the hole taper and HAZ width were 5.0% and 2.2%, respectively, further verifying the effectiveness of the optimization method. This technique not only improves processing quality but also offers significant industrial application value in the machining of materials for related high-tech fields. [ABSTRACT FROM AUTHOR]

In recent years, fiber-reinforced plastics (FRPs) materials like glass fiber-reinforced plastic (GFRP) and carbon fiber-reinforced plastic (CFRP) are next-generation polymer-based composite materials tailored for lightweight engineering applications in aerospace, marine, chemical, and automotive industries. Applying inclined holes in GFRP material is essentially used in producing robotic parts, microelectronics components, wind turbine blades, etc. The bending actuators and microhinges of microrobots constructed from CFRP materials also require inclined holes. Laser percussion drilling techniques produce a high aspect ratio of high-resolution inclined holes. The geometrical deviation of the laser-drilled hole is usually evaluated in terms of hole circularity and hole taper. No literature is available for inclined hole drilling of the above two types of FRPs using infrared (IR) laser. In this paper, the thickness of each FRP is taken as 1, 3 and 5 mm, respectively. The one-parameter-at-a-time (OPAT) method was used to analyze the individual effects of laser input parameters, such as pulse current, pulse width, assist gas pressure, workpiece thickness, and incidence angle, on output performance characteristics of hole circularity at top (THC), bottom (BHC), and taper (TH) during laser percussion-inclined drilling with millisecond (ms) pulsed Nd: YAG. Pulse current of 200–225A or 275–300A does not affect THC at a zero-degree angle of incidence. A greater pulse current (300 A) is produced during inclined drilling at 100∘ and 200∘. SEM/EDX investigation reveals hole surface and material composition. [ABSTRACT FROM AUTHOR]

Laser drilling cooling holes into turbine components is well established in industries. However, there are drawbacks related to setting and maintaining the appropriate manufacturing conditions, which can be formulated as an inverse problem. The inverse solution of a physical model describing long-pulse laser drilling of sheet metal is learned through an artificial algorithm. The trained feed-forward neural network predicts process parameters of desirable production outcomes. Here, the trained network predicts beam radius and pulse power to drill through getting a hole with specified conicity. The hyperparameters of the neural network are trained using algorithmic differentiation. Using a physical model improves the solvability of the inverse problem, since all trials during training belong to the applicable range of laser drilling and improves the training procedure going in a physically informed direction. [ABSTRACT FROM AUTHOR]

The main objective of this work is to provide a basic understanding of the mechanisms and locations of defect formation during percussion laser drilling of microholes using ultrashort pulses. Through the application of high-speed synchrotron X-ray imaging, we have been able to observe the dynamic formation and evolution of these defects in real-time. Our findings indicate that the initial deviations in the borehole geometry are highly dependent on the applied laser fluence. Specifically, while higher peak fluences facilitate deeper drilling, there exists a critical threshold beyond which the position of these deviations begins to decrease as the fluence increases. This behavior can be partially predicted within a certain fluence range using an existing theoretical model, which our experimental observations have tested and validated. Consequently, this research not only advances our understanding of defect formation in laser drilling but also provides a predictive framework for optimizing drilling parameters to minimize defects and enhance borehole quality. [ABSTRACT FROM AUTHOR]

The application of laser in the drilling and perforation of oil wells can achieve great benefits such as reduced drilling costs and time with a higher rate of penetration (ROP) and elimination of casing necessity in oil and gas well drilling. This paper presents an original experimental investigation of Laser cutting through Hashma sandstone (a common quarry rock in Egypt) to develop a good understanding of the laser cutting process in sandstone. Five blocks of Hashma sandstone with dimensions of 35 cm × 35 cm × 10 cm were utilized to study the effects of the various parameters involved in the lasing (cutting) process in order to evaluate the cutting process through sandstone, investigate the effect of laser parameters on the process and the cutting mechanisms. The experimental results showed that the laser drilling can provide lower specific energy (SE) compared to conventional drilling methods, revealed the effect of various laser and rock parameters (such as beam power, intensity, duration, sample size, and orientation) on the cutting process, and demonstrated the laser cutting mechanisms through sandstone such as thermal spallation and melting mechanisms. Several parameters must be optimized for an optimum laser cutting process with the lowest SE, such as using the optimum beam power, beam duration (or Lasig time), and beam mode (continuous or pulsed). The optimum parameters may change from one case to another and depend on the overall interactions among the various variables such as thermal dissipation rate and purging system efficiency.

Interactions between light and matter during short-pulse water-jet guided laser materials processing are highly nonlinear, and acutely sensitive to laser machining parameters. Traditionally, the physical simulation calculation methods based on laser, water and composite materials are complicated. This work combines neural networks and physical simulation models in the understanding of laser drilling of composite materials. Neural networks are used to predict SiC/SiC composites laser drilling results by using processing parameters (average power, scanning speed, and filling spacing) as input parameters, optimal combinations of processing parameters based on the neural network are identified, and the effectiveness of the learned knowledge is validated using a physical simulation model. The results show that the neural network can identify the nonlinear effect of processing parameters on machining quality with the MAE of 0.054 and the RMSE of 0.067. The physical simulation model could explain why this nonlinear effect exists. This method can be applied to a wide range of fields. In the face of unknown material and physical processing processes, the approach of combining neural networks and physical simulation models has the potential to significantly reduce the optimization time and deepen the understanding of laser processing. [ABSTRACT FROM AUTHOR]

A limited understanding regarding the underlying dynamics and mechanisms of material removal during continuous wave laser drilling has presented significant challenges in achieving precision and process control. To address this, we employed high-fidelity, in situ synchrotron x-ray imaging to reveal previously unknown material behaviors during continuous wave laser drilling with power modulation. Our findings highlight that high-aspect ratio drill holes are achieved when the laser modulation frequency falls within the range of 8–12 kHz, provided that the laser average power and modulation amplitude levels meet the specified limits. Under these conditions, we identified a material removal mechanism driven by incremental accumulation of recoil pressure that gradually pushes material upward from deep within the substrate to the surface. This mechanism manifested as a low-frequency fluctuation in the vapor depression depth, resulting in periodic instances of material ejection. Furthermore, our study underscores that rapid expansion of the melt pool and the widening of the drill hole opening can impede effective material removal by redirecting energy from material ejection to increasing the melt pool size. This investigation contributes essential insights into the subsurface dynamics involved in the drilling of high-aspect ratio holes, furthering our fundamental understanding of this intricate process. [ABSTRACT FROM AUTHOR]

A newly developed and hand layup hybrid FRP of Basalt, Glass and Kevlar-29 was considered for the characterisation of Nd: YAG laser drilling and optimisation using stochastic methods. Laser current (LC), pulse width (PW), stand-off distance (SoD), and compressed air pressure (CAP) were the laser parameters. The Box-Behnken designed laser drilling experiments were completed to characterise through hole taper angle and average overcut. The grey relational grade (GRG) of the responses was considered for optimisation using a genetic algorithm (GA), teaching learning-based optimisation (TLBO) and golden jackal optimisation (GJO). The predicted optimum setting was LC of 180 A, SoD of 1 mm and CAP of 8 kg/cm2. The GA & TLBO and GJO predicted PW of 3 ms with GRG of 0.9948 and 2.625 ms with GRG of 0.9203, respectively. The experimental verification of the predicted conditions acknowledges the predicted values of the responses with acceptable errors. [ABSTRACT FROM AUTHOR]

This research investigates the complex temperature distribution and fatigue behavior of single film-cooling holes manufactured by lasers with different pulse widths in a real flow field. The aerodynamic and heat transfer characteristics of film-cooling holes manufactured using lasers with different pulse widths were analyzed through laser drilling experiments, conjugate heat transfer simulations, and crystal plasticity finite element methods. The study investigated the relationship between changes in the geometric accuracy of the film-cooling holes and the corresponding flow and temperature fields during the film-cooling process. Additionally, the effects of temperature and structural variations on the stress around the holes in a flat plate composed of the second-generation nickel-based single-crystal superalloy DD6 in real flow and temperature fields were studied. The coupling effect of the temperature and stress fields around the holes on the fatigue behavior of the film-cooling holes was examined, and the fatigue damage mechanism of film-cooling holes in complex temperature fields was analyzed. It was found that changes in the blowing ratio do not affect the temperature and stress distributions around the holes but only alter the temperature peak. An increase in the temperature peak results in a decrease in the stress peak. Additionally, the fatigue damage of single film-cooling holes is determined by both the structural defects of the holes and the changes in material behavior due to the temperature around the holes, with the structural influence being more significant. [ABSTRACT FROM AUTHOR]

An essential consideration for metal-polymer applications is that the sound joining of these materials is challenging due to a significant surface energy differential in different structural characteristics between polymer and metal. However, the joining methods have some drawbacks, such as low-reliability joints, long curing time, stress concentration, and polymer degradation. A new novel metal-polymer hybrid joining technique is proposed in this work to overcome these issues and cost perspectives, manufacturing, and overcoming the problem of PVC degradation due to heat generation of other joining methods. In this study, we managed to join PVC to AA5053 sheets using a cold joining technique based on extruding PVC through a conical hole of an aluminum specimen using a punching tool. Experiments consisted of three parameters (the hole diameter, plunging depth, and radius of the punch), with four levels for each parameter. The experiments were designed, and mechanical characterizations of the joints were optimized using the design of the experiment's method. The hole diameter was the effective parameter on the mechanical characterizations and dimensions of the extruded PVC. Increasing the diameter of the AA5053 sheet increased the maximum diameter of the extruded PVC, shear force, and pull-out force of the joints and decreased the shear stress of the joints. We obtained a maximum shear strength of 106.15 MPa, which is ~3 times higher than the tensile strength of PVC (37 MPa). [ABSTRACT FROM AUTHOR]

Minimizing the drilling-induced damage on the walls and sub-surfaces of the drilled holes is a challenging but demanding task, especially on hard-to-machine materials such as CFRP/Ti-6Al-4 V stacks. In general, these stacks are highly preferred in aerospace structural applications. This paper analyzes the surface integrity of the drilled CFRP holes when they are stacked above the Ti-6Al-4 V alloy, by incorporating the laser-based marking of micro-textures on the flank and rake faces of the drill, which enables the micro-pool lubrication between the cutting-edges and work material. Comparative experimentations were conducted under MQL conditions. Considering the flank face micro-grooved drill, consistently lower thrust forces were observed across the entire range of cutting speeds and feeds, achieving reductions of up to 17 to 20%. Furthermore, the tool life study was performed, which reveals a substantial 26% enhancement in tool life with the flank face grooved drill, emphasizing its significant advantages for enhanced machining performance. [ABSTRACT FROM AUTHOR]

Laser drilling is widely used for fabricating holes in the semiconductor industry due to high throughput and a small heat-affected zone. However, it produces varying depths owing to uncertain external conditions and requires live control at the rate of a few tens of kHz to handle the fast material removal rate. Optical coherent tomography is capable of in situ acquiring a raw interferogram at a high rate (>80 kHz), but the depth extraction is slow due to the involved heavy Fast Fourier Transform (FFT). To address this, an efficient depth-tracking algorithm is proposed to save the FFT. It searches the depth in the raw interferogram locally with a known last depth given the two truths that only one depth exists and the adjacent depths do not change significantly. The proposed algorithm was proven to expedite the measuring rate six times with sub-pixel tracking precision. To further secure the rate against the interrupting of the system, the tracking process is parallelly implemented in a field-programmable gate array. The closed-loop control tests were conducted on probe cards with depth variations introduced by offsetting laser focus. The proposed method maintained a uniform depth, with variations reduced by 80% compared to traditional methods. [ABSTRACT FROM AUTHOR]

The process of casing the wellbore in oil and gas drilling consumes a significant amount of time and economic resources. High-energy laser rock fracturing, as an efficient and cost-effective new approach, holds the potential to create a glass-like casing by irradiating the rocks as an alternative to traditional casing. The mechanism behind the vitrification of rocks using laser irradiation, a key factor in achieving glassified casings, remains to be studied. This paper, based on experiments involving scanning sandstone with a line laser, investigates the mechanism of rock vitrification using numerical simulations and X-ray diffractometers. The results demonstrate that the sandstone surface is transformed into glass after laser scanning, with multiple scans and the application of high-speed airflow helping to reduce the formation of bubbles and other phenomena. Furthermore, the speed of laser scanning showed a negative correlation with the laser ablation depth, glass thickness, temperature diffusion rate, and temperature gradient. Based on these findings, a groundbreaking method is proposed for creating high-quality glass by moving the laser to scan the rocks multiple times, offering insights for research into laser-manufactured wellbore casings. Furthermore, this approach holds promising prospects for enhancing and embellishing the exterior of structures and for in situ environmental modifications on planetary surfaces and beyond. [ABSTRACT FROM AUTHOR]

The water-assisted laser trepanning method has been proven to improve the quality of laser drilling; however, the effect of water temperature on this process is currently unclear. In order to investigate the influence of water temperature on the quality of holes produced via water-assisted laser trepanning in superalloys, this study used the controlled variable method to investigate the effects of three water temperatures—low temperature (2 °C), normal temperature (20 °C), and high temperature (70 °C)—on the following factors: spatter, hole diameter, taper angle, hole sidewall morphology, and recast layer. The results show that the spatter around the hole reduced, the hole entrance/exit diameter increased, and the roughness of the hole's sidewall decreased with an increase in single-pulse energy. However, the effect of single-pulse energy on the recast layer was not obvious. As the temperature of the water increased, the hole entrance/exit diameter increased, and the roughness of the hole's sidewall decreased. When the single-pulse energy was 1.0–1.9 J, using a lower water temperature produced a hole with a smaller taper angle. Compared with a water temperature of 20 °C, the movement of the melt film on the hole's sidewall accelerated when the water temperature was 70 °C; as a result, more molten material could be removed from the hole, resulting in a decrease in the thickness of the recast layer. However, when the water temperature was 2 °C, the heat-affected zone and the thickness of the recast layer decreased more significantly. The results of this study provide technical support for the optimization of water-assisted laser drilling. [ABSTRACT FROM AUTHOR]

This document discusses the determination of residual stress in aluminum alloy aerospace components using the blind hole drilling method and optical interferometric measurements. The study presents experimental procedures and uncertainty analysis for measuring residual stresses in materials. The results show that the method provides accurate and reliable results with a low level of uncertainty. The document also provides a list of references related to the measurement of residual stresses, discussing various methods and their applications in different fields. [Extracted from the article]

Copyright of Journal of Drainage & Irrigation Machinery Engineering / Paiguan Jixie Gongcheng Xuebao is the property of Editorial Department of Drainage & Irrigation Machinery Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Metallic structures produced with laser powder bed fusion (LPBF) additive manufacturing method (AM) frequently contain microscopic porosity defects, with typical approximate size distribution from one to 100 microns. Presence of such defects could lead to premature failure of the structure. In principle, structural integrity assessment of LPBF metals can be accomplished with nondestructive evaluation (NDE). Pulsed infrared thermography (PIT) is a non-contact, one-sided NDE method that allows for imaging of internal defects in arbitrary size and shape metallic structures using heat transfer. PIT imaging is performed using compact instrumentation consisting of a flash lamp for deposition of a heat pulse, and a fast frame infrared (IR) camera for measuring surface temperature transients. However, limitations of imaging resolution with PIT include blurring due to heat diffusion, sensitivity limit of the IR camera. We demonstrate enhancement of PIT imaging capability with unsupervised learning (UL), which enables PIT microscopy of subsurface defects in high strength corrosion resistant stainless steel 316 alloy. PIT images were processed with UL spatial–temporal separation-based clustering segmentation (STSCS) algorithm, refined by morphology image processing methods to enhance visibility of defects. The STSCS algorithm starts with wavelet decomposition to spatially de-noise thermograms, followed by UL principal component analysis (PCA), fine-tuning optimization, and neural learning-based independent component analysis (ICA) algorithms to temporally compress de-noised thermograms. The compressed thermograms were further processed with UL-based graph thresholding K-means clustering algorithm for defects segmentation. The STSCS algorithm also includes online learning feature for efficient re-training of the model with new data. For this study, metallic specimens with calibrated microscopic flat bottom hole defects, with diameters in the range from 203 to 76 µm, were produced using electro discharge machining (EDM) drilling. While the raw thermograms do not show any material defects, using STSCS algorithm to process PIT images reveals defects as small as 101 µm in diameter. To the best of our knowledge, this is the smallest reported size of a sub-surface defect in a metal imaged with PIT, which demonstrates the PIT capability of detecting defects in the size range relevant to quality control requirements of LPBF-printed high-strength metals. [ABSTRACT FROM AUTHOR]

Frequently orthopedic surgeries require mechanical drilling processes especially for inserted biodegradable screws or removing small bone lesions. However mechanical drilling techniques induce large number of forces as well as have substantially lower material removal rates resulting in prolong healing times. This study focuses on analyzing the impact of quasi-continuous laser drilling on the bone's surface as well as optimizing the drilling conditions to achieve high material removal rates. An ex-vivo study was conducted on the cortical region of desiccated bovine bone. The laser-based drilling on the bovine bine specimens was conducted in an argon atmosphere using a number of laser pulses ranging from 100 to 15,000. The morphology of the resulting laser drilled cavities was characterized using Energy dispersive Spectroscopy (EDS) and the width and depth of the drills were measured using a laser based Profilometer. Data from the profilometer was then used to calculate material removal rates. At last, the material removal rates and laser processing parameters were used to develop a statistical model based on Design of Experiments (DOE) approach to predict the optimal laser drilling parameters. The main outcome of the study based on the laser drilled cavities was that as the number of laser pulses increases, the depth and diameter of the cavities progressively increase. However, the material removal rates revealed a decrease in value at a point between 4000 and 6000 laser pulses. Therefore, based on the sequential sum of square method, a polynomial curve to the 6th power was fit to the experimental data. The predicted equation of the curve had a p-value of 0.0010 indicating statistical significance and predicted the maximum material removal rate to be 32.10 mm3/s with 95%CI [28.3,35.9] which was associated with the optimum number of laser pulses of 4820. Whereas the experimental verification of bone drilling with 4820 laser pulses yielded a material removal rate of 33.37 mm3/s. Therefore, this study found that the carbonized layer formed due to laser processing had a decreased carbon content and helped in increasing the material removal rate. Then using the experimental data, a polymetric equation to the sixth power was developed which predicted the optimized material removal rate to occur at 4820 pulses. [ABSTRACT FROM AUTHOR]

The aim of this work was to investigate the impact of nanosecond pulse laser drilling on the quality of carbon fiber reinforced polymer (CFRP). The effects of laser parameters, including laser power, scan speed, pulse width and laser frequency on micro-hole quality and the thermal damage generated during the drilling process were analyzed. 0.4 mm diameter micro-holes were drilling using a 1064 nm fiber laser, using univariate and orthogonal experimental method. The results indicate that pumping at the entrance leads to a significant increase in hole diameter and heat-affected zone (HAZ) width at both the entrance and exit, as laser power, pulse width and frequency increase, and scanning speed decrease. The width of the HAZ at the exit is dependent on whether the energy reaches the carbon fiber ablation threshold. The holes were tapered and the hole taper was closely related to the change in laser parameters at the entrance and exit of the hole. A taper of approximately 0.3 was achieved with a combination of 99 W, 50 mm/s, 13 ns and 1500 kHz. The experiments indicate that laser power and pulse width are crucial factors that affect the quality of micro-hole processing. However, nanosecond laser drilling can result in thermal damage defects, including striations, micro-cracks, delamination, voids and surface fiber 'fish scale' peeling. [ABSTRACT FROM AUTHOR]

Transparent 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. [ABSTRACT FROM AUTHOR]

The laser drilling of carbon steel is always suffered from the formation of slag, the presence of cutting burrs, the generation of a significant quantity of spatter, and the incomplete penetration of the substrate. In order to avoid these defects formed during the laser drilling of carbon steel, the COMSOL multi-physics simulation method was used to model and optimize the laser drilling process. Considering the splash evolution of the material during the complex drilling process, the transient evolution of the temperature field, the flow of the molten fluid, the geometrical changes, and the absorption of the laser energy during the laser drilling process were investigated. The simulated borehole dimensions are consistent with the experimental results. The process parameters have a great influence on the fluid flow pattern and material slag splashing. The laser power has a significant effect on the laser processing compared with the process parameters. With the increase in laser power and the decrease in laser heat source radius, the time required for perforation is reduced, the flow of melt is accelerated, the perforation efficiency is increased, and the hole wall is smoother, but the degree of spattering is greater. The optimized process parameters were obtained: laser heat source radius of 0.3 mm, laser power of 3000 W. These findings can help reduce the machining defects in carbon steel with excellent mechanical properties by optimizing the laser drilling processing parameters. [ABSTRACT FROM AUTHOR]

Lithium‐ion batteries inherently suffer from a target conflict between a high energy density and a high power density. The creation of microscopic holes in the electrodes alleviates the trade‐off by facilitating lithium‐ion diffusion. This study presents a novel concept for electrode structuring called structure calendering, combining mechanical embossing (MEC) and calendering. It is compared to the widely investigated laser ablation (LAS) process by structuring graphite anodes and examining their geometrical, mechanical, and electrochemical properties. It is shown that structure calendering results in wider and deeper holes of higher reproducibility than laser structuring. As a consequence of the different hole‐creation mechanisms, laser structuring induces a surface elevation around the holes while clogged pores are observed in the lateral walls of mechanically structured holes. In pull‐off tests, no pronounced impact of electrode structuring on the mechanical electrode properties is discerned. Structuring of electrodes using both methods yields significantly reduced electrode tortuosities and enhanced discharge rate performances. From a production engineering perspective, structure calendering has advantages over laser structuring in terms of material loss, processing rate, and investment costs, while the latter offers higher flexibility, precision, and presumably lower maintenance efforts. In conclusion, structure calendering represents an attractive process alternative to laser structuring. [ABSTRACT FROM AUTHOR]

The restoration of critical-size load-bearing bone defects calls for the application of bioactive scaffolds that are regenerative, osteoconductive, and demonstrate mechanical strength comparable with natural bone. Novel hydroxyapatite (HAp) scaffolds sourced and fabricated through the biomorphic transformation of rattan wood (GreenBone-GB) were laser-drilled (LD) with parallel and lateral sub-millimetre channels, which enhanced the overall porosity for promoting the flow of cells and fluids throughout the scaffolds. The compositional analysis of the LD scaffolds confirmed the presence of the Ca5(PO4)3OH and Ca3(PO4)2 phases, with no evidence of drilling contamination. Water jet laser drilling enhanced the interconnecting porosity of the morphogenic scaffolds by 22.5 %, without obstructing the intrinsic uniaxial fibrous structure inherited from rattan wood. Across eight varied drilled patterns, the resulting scaffolds preserved the structural integrity and exhibited compressive strength ranging from 6.74 ± 1.25 to 10.18 ± 0.43 MPa, while the Vickers Hardness was comparable with natural bone. Cell viability assessments confirmed that the LD scaffolds exhibited no toxicity and presented >90 % cell viability. We demonstrate that laser drilling effectively enhanced the pore volume for improved osteoconductivity via cell migration in the bio-morphogenic GB-structure. Since the GB scaffolds are CE-marked products, laser drilling for pore surface engineering could provide improved scaffolds for clinical use.

One of the effective ways to achieve drilling of Carbon fiber reinforced polymer (CFRP) materials is to use short pulse lasers. However, the existing cutting thermal damage, such as the heat-affected zone (HAZ), can weaken the CFRP mechanical properties. In this paper, a heterogeneous mesoscopic model of transient distribution of short pulse laser ablation heat flow is built to fully explore the formation and extension mechanism of thermal damage. The significant difference in laser interaction thermal effects between fibers and resin leads to the formation of HAZ with exposed fibers. The interface effect exists in the ablation process, which aggravates the matrix damage. The ablation of carbon fibers occurs within the duration of a single laser pulse, and the degree of ablation depends on the pulse energy. Under the coupling of the thermal conduction effect along the fiber axis and the thermal accumulation effect between pulses, the matrix damage extends significantly during the cooling stage. Large pulse repetition frequency increases heat accumulation between pulses and increases matrix damage. There is a new erosion mechanism in that the thermal accumulation behavior leads to the falling off of fragmented carbon fiber filaments. The accuracy of the model was verified through different pulse ablation tests, and the average error of ablation morphology is 11.28%. [ABSTRACT FROM AUTHOR]

The fact is that hundreds of holes are drilled in the assembly process of furniture sets, so intelligent drilling is a key element in maximizing efficiency. Increasing the feed rate or the cutting speed in materials characterized by a higher machinability index is necessary. Smart drilling, that is, the real-time adjustment of the cutting parameters, requires the evolution of cutting process variables. In addition, it is necessary to control and adjust the processing parameters in real time. Machinability is one of the most important technological properties in the machining process, enabling the determination of the material's susceptibility to machining. One of the machinability indicators is the unit cutting resistance. This article proposes a method of material identification using the short-time Fourier transform in order to automatically adjust cutting parameters during drilling based on force signals, cutting torque and acceleration signals. In the tests, four types of wood-based materials were used as the processed material: medium-density fiberboard, chipboard, plywood board and high-pressure laminate. Holes with a diameter of 10 mm were drilled in the test materials, with variable feed rate, cutting speed and thickness of cutting layer. An innovative method for determining the value of unit cutting resistance was proposed. The results obtained were used to determine the machinability index. Based on the test results, it was shown that both the selected signal measures in the time and frequency domains and the unit cutting resistance are constant for a given material of a workpiece and do not depend on the drilling process parameters. In this article, the methodology is proposed, which can be used as an intelligent technique to support the drilling process to detect the material being machined using data from sensors installed on the machine tool. The work proposes the fundamentals for material identification based on the analysis of force signals and the magnitude of force derivatives. The proposed methodology shows effectiveness, which proves that it can be used in intelligent drilling processes. Hybrid wood-based material structures consisting of different materials are becoming more and more common in building structures for strength, economic and environmental reasons. Due to the difference in the machinability of interconnected materials, cutting parameters must be optimized in real time during machining. Currently, with the rapid development of Industry 4.0, the on-line identification of parameters is becoming necessary to improve the process flow in industrial reality. The proposed methodology can be used as an intelligent technique to support the drilling process in order to detect the material being processed using data from sensors installed on the machine tool. [ABSTRACT FROM AUTHOR]

In this paper, water jet-guided laser (WJGL) drilling of C f / 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 C f / SiC composites. [ABSTRACT FROM AUTHOR]

In this contribution, we present novel results on top-down drilling in silicon, the most important semiconductor material, focusing specifically on the influence of the laser parameters. We compare the holes obtained with repetitive single pulses, as well as in different MHz- and GHz-burst regimes. The deepest holes were obtained in GHz-burst mode, where we achieved holes of almost 1 mm depth and 35 µm diameter, which corresponds to an aspect ratio of 27, which is higher than the ones reported so far in the literature, to the best of our knowledge. In addition, we study the influence of the energy repartition within the burst in GHz-burst mode. [ABSTRACT FROM AUTHOR]

The laser beam mode affects the power density distribution on the irradiated target, directly influencing the product quality in laser processing, especially the hole quality in laser drilling. The Gaussian beam shape, Mexican-Hat beam shape, Double-Hump beam shape, and Top-Hat beam shape are four typical laser beam modes used as a laser heat source and introduced into our proficient laser-drilling model, which involves complex physical phenomena such as heat and mass transfer, solid/liquid/gas phase changes, and two-phase flow. Simulations were conducted on an aluminum target, and the accuracy was verified using experimental data. The results of the simulations for the fundamental understanding of this laser–material interaction are presented in this paper; in particular, the hole shape, including the depth–diameter ratio and the angle of the cone, as well as spatter phenomena and, thus, the formed recast layer, are compared and analyzed in detail in this paper. This study can provide a reference for the optimization of the laser-drilling process, especially the selection of laser beam mode. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The use of static solution-assisted laser drilling can effectively improve hole roundness, decrease taper angle, and reduce recast layer thickness and hole wall slag adhesion. However, the enormous energy of the laser will evaporate the solution to form a suspension droplet and reduce the quality and efficiency of laser drilling. To deal with this defect, the mist-blowing method was used to reduce the influence of droplets on the taper angle and recast layer. In this work, the effect of wind speed on drilling quality was examined, and laser drilling in air, water, and NaCl solution was carried out to analyse the effect of solution composition on hole wall morphology. The results showed that a speed fan with a proper wind speed that disperses the droplets formed in the processing area can significantly reduce the refraction and scattering of the laser, and the taper angle and roundness of the drilling hole were also reduced by 15.6% and improved by 2.4%, respectively, under the wind speed of 2 m/s. The hole wall morphology showed a thicker recast layer and cracking in air, while it was thinner in water and there was little or no layer in the NaCl solution in the same current. When drilling in NaCl, the taper angle and roundness of the drilling hole were reduced by 4.13% and improved by 2.11%, respectively, compared to water. Due to the mechanical effect of the laser in the NaCl solution, the impact force on the material was much greater than that in water. The solution cavitation effect, generated by the absorption of laser energy, caused an explosive impact on the molten material adhered to the surface of the hole wall. Above all, drilling in the NaCl solution with a current of 200 A and a wind speed of 2 m/s was the optimal condition for obtaining the best processing quality. [ABSTRACT FROM AUTHOR]

Traditional coiled tubing radial drilling with the same diameter cannot support deep and ultra-deep wells for high-pressure hydraulic jet drilling due to small diameter and sizeable hydraulic loss over long distances. The novel downhole movable pipe radial hydraulic drilling technique extracts a small diameter high-pressure injection pipe from the (tubing pipe) oil pipe and then drills it horizontally into the formation to form a radial hole. Dynamic sealing is the core of this technology, which achieves high-pressure fluid sealing while ensuring the injection pipe smoothly slides out of the oil pipe. A sealing tool is designed between the tubing and the injection pipe to prevent the leakage of high-pressure fluid. In this paper, the finite element model of the sealing tool was established, and the deformation and stress of the sealing tool under different interference and fluid pressure were simulated and analyzed. The relationship between stress distribution and contact pressure under the corresponding conditions was obtained. The results show that the von Mises stress increases significantly with the increase in fluid pressure under certain interference conditions. When the fluid pressure was 35 MPa, 52 MPa, and 70 MPa, the maximum von Mises stress was 29.65 MPa, 30.87 MPa, and 32.47 MPa, respectively, within a reasonable range. The stress peak area changes simultaneously, indicating that the possible damage location changes with the fluid pressure change. The maximum contact pressure between the sealing ring and the smooth rod increases with interference and fluid pressure, which always meets the sealing conditions. A laboratory test bench was built to test the high-pressure sealing performance of the sealing tool. Combined with the simulation data and test results, the downhole continuous rod dynamic sealing tool was modified to provide theoretical guidance for practical application. [ABSTRACT FROM AUTHOR]

Introduction: In the actual engineering operation, there are some components facing high frequency friction, which have high damage rate and poor direct replacement benefit. In order to achieve sustainable resource utilization and more effective component remanufacturing, research was conducted on the cladding layer of friction components. Methods: Based on the idea of remanufacturing, taking 42CrMo as the raw material of engine piston pin hole, laser cladding technology and ultrasonic rolling technology are used to prepare the cladding layers of Fe, Ni and Co three different substrates. Results and Discussion: The experimental results showed that the Co based cladding layer with ultrasonic rolling technology performed best. The surface roughness reduced by 1.02 µm, only 0.14 µm. The microhardness increased by 101.39%, with 795.38 HV. The friction coefficient was 0.051. The friction rate at high temperature decreased by 85.71%, and it was 1.2%. The friction at high temperature was reduced by 79.24%, with 0.9%. Conclusion: Co based cladding layer combined with ultrasonic rolling technology shows the best performance, which can effectively realize the remanufacturing of engine piston pin hole, providing technical reference and data support for the remanufacturing process of high-frequency friction components. [ABSTRACT FROM AUTHOR]

Flexible hole-shape control during ultrafast laser micro-drilling requires in-depth understanding of the processing dynamics, which remains a challenge. We use an in-situ imaging method to visualize the dynamic evolution of hole shape during the ultrafast laser drilling of metals. The direct visualization of the hole shaping dynamics shows that the laser beams are transmitted towards the hole bottom with polarization-dependent reflections on the hole wall. There exists a depth threshold from which the reflected laser beams start to dominate the hole shape under all conditions, and the depth threshold is jointly determined by the pulse energy and polarization of the laser, the trepanning radius, and the material. Due to the polarization-dependent beam reflections, the hole shape evolves uniformly under circularly polarized laser, whereas in the case of linearly polarized laser, two distinct shape evolution patterns are observed on the sections parallel and perpendicular to the polarization direction. These results provide fresh understanding on hole shaping dynamics, and the proposed in-situ imaging method is a powerful platform for the in-depth research of laser drilling process. • Dynamic evolution of hole shape was visualized in situ for laser metal drilling. • Polarization-dependent, beam reflection-regulated hole shaping dynamics revealed. • There exists a depth threshold for the reflected beams start to dominate hole shape. [ABSTRACT FROM AUTHOR]

A hollow core fiber (HCF) is spliced with a single-mode fiber, and then, the end face of the HCF is etched to form a microsphere interferometer for measuring gas pressure and environmental temperature. The total length of each microsphere is less than 200 μm. We fabricated two such structures and used femtosecond laser pulses to drill micro-holes on the HCF walls of both structures. One of the structures is directly used to measure air pressure, achieving a sensitivity of up to 2.857 nm/MPa while being almost insensitive to temperature. This structure is capable of assessing pressure down to 3.4 kPa within the range of 0–0.5 MPa. Another structure is filled with thermally sensitive material dimethyl silicone oil through a micro-hole, and then, it is sealed with AB adhesive to form a harmonic Vernier effect temperature sensor, with a sensitivity of up to −5.16 nm/°C. This structure is capable of assessing temperature down to 0.38 °C within the range of 30–60 °C. Additionally, the sensors have good repeatability and stability and compact structure and simple manufacturing and can be used as a sensing probe for monitoring gas pressure and temperature under extreme environments. [ABSTRACT FROM AUTHOR]

Although grinding is a widely employed method for hard and brittle materials, drilling microholes requires the use of an ultrasmall-diameter grinding wheel that is difficult to fabricate and breaks easily when grinding force is applied, resulting in a high tool cost. To solve this problem, cemented WC micropins were fabricated by electrical discharge machining, and microholes were drilled using them as micro-grinding tools with the assistance of ultrasonic oscillation. The micropin tools can be employed in grinding because the convex parts of the electrical discharge craters formed on their surfaces serve as cutting edges of abrasive grains in grinding wheels. To clarify the drilling conditions necessary for ultrasmall-diameter tools to drill holes with a diameter less than 5 µm, the relationships between drilling conditions and drilling characteristics were investigated. The drilling conditions included the tool rotation speed, tool feed speed, ultrasonic oscillation amplitude, and use of grinding fluid. The drilling characteristics included the hole diameter and grinding force evolution. The investigation showed that a high tool rotation speed prevented the increase in the grinding force because of the faster grinding speed. A low tool feed speed was favorable to lower grinding force. At a high tool feed speed, most likely, the tool was fed before the workpiece material was sufficiently removed, thereby exhibiting a large grinding force. The ultrasonic oscillation amplitude had no noticeable effect on the grinding force. The hole diameter was not affected by the tool rotation speed, tool feed speed, or ultrasonic oscillation amplitude. Although the use of grinding fluid reduced the grinding force, the hole diameter increased, probably because enhanced lubrication caused the tool to slip on the workpiece surface at the beginning of drilling, resulting in an increased rotational runout. Under the favorable conditions obtained, a hole of 3.2 µm in diameter was successfully drilled in crown glass. [ABSTRACT FROM AUTHOR]

We investigate the elongated modifications resulting from a Bessel beam-shaped femtosecond laser in fused silica under three different operation modes, i.e., the single-pulse, MHz-burst, and GHz-burst regimes. The single-pulse and MHz-burst regimes show rather similar behavior in glass, featuring elongated and slightly tapered modifications. Subsequent etching with Potassium Hydroxide exhibits an etching rate and selectivity of up to 606 μm/h and 2103:1 in single-pulse operation and up to 322 μm/h and 2230:1 in the MHz-burst regime, respectively. Interestingly, in the GHz-burst mode, modification by a single burst of 50 pulses forms a taper-free hole without any etching. This constitutes a significant result paving the way for chemical-free, on-the-fly drilling of high aspect-ratio holes in glass.

In order to find the optimal expansion effect of a new curing expansion material so that it can better meet the requirements of the efficient sealing of drilled holes, the expansion and creep characteristics of the new curing expansion material were studied. Based on the creep results of graded loading, the Kelvin–Volgt model was selected to analyze its mechanical parameters, and a new "concentric ring" reinforcement sealing method was proposed. Numerical simulation was employed to analyze and discuss the reinforcement radius and depth of the "protective wall rock hole ring" in the "concentric ring" model, and on-site application experiments were carried out in a soft coal seam. The results show that the "concentric ring" reinforcement sealing method can effectively solve the problems of easy collapse and stress concentration instability in the sealing section of soft coal seams, ensuring long-term and efficient sealing of gas extraction boreholes in soft coal seams. When the diameter of the extraction drilling hole is 100 mm, the optimal reinforcement radius for the "protective wall rock hole ring" is 0.16–0.18 m. A reasonable reinforcement depth of the "protective wall rock hole ring" for drilling in soft coal seams is about 0.8–1 times the width of the roadway. In the on-site application process, experimental boreholes using "concentric ring" reinforcement sealing technology did not show any collapse phenomena, and the volume fraction of extracted gas remained above 30% for the first 30 days. Moreover, the gas volume fraction on the 30th and 60th days was 2.5 times and more than 3 times that of bag sealing boreholes using expanded cement, further proving that the sealing quality of boreholes using "concentric ring" reinforcement sealing is higher. [ABSTRACT FROM AUTHOR]

In drilling small holes with diameters of 1 mm or less, minute clogging and twining of chips or the adhesion of the workpiece material can become factors in causing breakages of the drill bit; moreover, it can be difficult to identify the machining state. Acoustic emission (AE) sensing is a nondestructive inspection technique that measures the elastic-stress waves that are generated when a material is deformed and fractured. AE sensing permits highly sensitive measurements to be made without changing the rigidity of the experimental system, unlike force sensing of cutting resistance, etc. In the present study, attempts were made to identify the machining state and tool wear, and to predict abnormalities in small-diameter drilling by using the change in the frequency of AE signal waveforms arising from deformation and fracture. It was shown that it is possible to predict the breakage of the drill bit by detecting high-frequency AE signals at about 1 MHz, caused by the adhesion of the workpiece material. In addition, a correlation map of the AE frequency spectrum for identifying the machining state in a drilling operation is suggested. [ABSTRACT FROM AUTHOR]

Laser drilling is not only widely used in a variety of materials but also commonly applied to diverse industrial fields. Due to the fast processing speed, the monitoring of the laser drilling process has always been a challenge. Some studies have been conducted to measure the signal of laser-induced plasma in the laser percussion drilling process by applying an external electric field to monitor the laser percussion drilling process in real-time. Using the laser-induced plasma signal for monitoring purposes, the relationship model between the measured plasma signal and the hole size achieved with laser percussion drilling has not been established. Once the relationship model is determined, the plasma signal can be used to predict the size of the laser drilled hole dimensions in real-time, and further realize a closed-loop control of the laser processing for a higher control technology. For this reason, we conducted a series of laser percussion drilling experiments with a fibre laser on 304 stainless steel and established a model by curve fitting with the laser percussion drilled hole sizes and the plasma signals in various laser processing parameters. [ABSTRACT FROM AUTHOR]

The circularity of the drilled hole at the top and bottom surfaces of the plate, as well as the taper angle of the drilled hole, are important characteristics in drilling that have a significant impact on the quality of a drilled hole. In this present study the laser trepanning drilling process is carried out on 7 mm thick glazed ceramic tiles using a fibre laser. The study investigates the effects of laser process parameters; namely, laser power, scanning speed, frequency and number of trepanning passes on the hole diameter at the top and bottom surfaces of the ceramic tile, the circularity of the hole at the top and bottom surface and the taper angle of the drilled hole. The effects of gas pressure and hole diameter on the hole characteristics are also investigated. It is observed that the circularity of the hole at the top surface increases with an increase in laser power, gas pressure, and hole diameter, whereas the circularity of the hole at the bottom surface decreases with an increase in laser power and scanning speed. It is also observed that the taper angle of the drilled hole increases with an increase in laser power, gas pressure and hole diameter. It is seen that the hole diameters on the top surface of the plate do not get much affected when the trepanning passes are increased. [ABSTRACT FROM AUTHOR]

This article presents the results of an experimental study on the effect of the selection of kinematic system for the drilling process on the cylindricity deviation, roundness deviation, diameter error and surface roughness of holes in brass alloy. Three different kinematic systems based on the dependence of the direction of rotation of the workpiece and the drill bit were used. The drill bit was mounted in an axially driven holder that allowed it to be put into motion. Cutting tests were conducted at three different spindle speeds and three different feed rates per revolution (27 tests in total). A static ANOVA analysis was used to evaluate the effect of each input parameter on each output parameter. The results of this work have practical applications in machining. The following input parameters of the drilling process should be used to obtain the smallest values of each output parameter: for CYL, n = 4775 rpm, fn = 0.14 mm/rev and KIN III; for RON, n = 4775 rpm, fn = 0.1 or 0.12 mm/rev and KIN II; for DE, n = 3979 rpm, fn = 0.1 mm/rev and KIN I; and for Rz, n = 4775 rpm, fn = 0.1 mm/rev and KIN II. This research work also used Grey Relational Analysis with which input parameter optimization was derived. The optimal drilling parameters are spindle speeds of 4775 rpm, a feed per revolution of 0.1 mm/rev and the use of the first kinematic system. This paper also includes equations for predicting each parameter that describes the dimensional and shape accuracy and roughness of the hole surface. Using the first kinematic system reduced the roughness of the hole surface by as much as 58%. The correct selection of kinematic system improved its dimensional accuracy by 15%. On the other hand, the roundness deviation of the hole improved by 33% and the cylindricity deviation of the hole by 6%. [ABSTRACT FROM AUTHOR]