Hole Taper Research Articles

Mechanical effect of taper position in abutment hole and screw taper angles on implant system and peri-implant tissue: a finite element analysis

Purpose The study aimed to investigate the mechanical effects of the taper position in the abutment hole and the screw taper angles on the implant system and peri-implant tissue using finite element analysis. Methods Four taper positions (L1, L2, L3, L4) in the abutment hole were established using 3D software and five screw taper angles (30°, 60°, 90°, 120°, 180°) were set. Result Taper position significantly affects the stresses in the implant system. The 30° and 180° angles (L4 position) showed less stress than other angles. Conclusion Elevated taper position and reasonable taper angle are beneficial in reducing the stress in the implant system.

Review of high-precision femtosecond laser materials processing for fabricating microstructures: Effects of laser parameters on processing quality, ablation efficiency, and microhole shape

Femtosecond lasers are promising tools for achieving high-precision processing of thin materials without causing any thermal surface damage and bulk distortion. However, thermal damage can occur even with ultrashort laser pulses. This is because of high electron penetration depth and heat accumulation at high fluence and high repetition rate. Nanoparticle redeposition can be dramatically altered with variation in repetition rate. The symmetry of microholes and ablation efficiency vary with laser polarization. The laser wavelength affects the ablation efficiency and surface roughness. Therefore, understanding these laser–matter interactions that depend on the laser parameters is essential for high-precision laser processing. This article reviews laser–matter interactions in the 64FeNi alloy, as well as analytical models for designing the desired hole size and taper angles. This can help establish strategies for creating various high-precision microstructures using femtosecond lasers.

Variable frequency selective structure (CFRP/Cu/CFRP) micro blind hole laser high-quality drilling method guided by acoustic emission technology

The laminated structure of carbon fiber reinforced plastic (CFRP)-Cu-CFRP is an important structure for aerospace radome. The blind holes manufacturing is core process, but there are technological challenges in achieving the exposure of a 10 μm thick copper foil at the bottom of the blind hole. The exact position of the 10 μm thick copper foil within the material’s internal space is unknown, and the uneven heat accumulation and conduction can easily cause burning and damage to the ultra-thin copper foil. To date, there is no publicly accessible literature that documents the execution of this specific process. In this paper, novel variable inner diameter spiral scanning guided by Cu-CFRP interface accurately extracted using cosine similarity (CS) algorithm is proposed to obtain a blind hole with near-zero ablation damage. The similarity of acoustic emission signals generated by laser interaction with Cu and CFRP, as well as thermal accumulation and conduction behavior under different scanning radius, are described. The high-quality blind holes have been successfully drilled, with a large area copper foil exposed at the bottom, while the surface of the copper foil remaining intact without any damage or heat affected zone. Compared with traditional drilling method, the average exposed copper foil area at the bottom of the blind holes is increased by 238.4 % (from 0.464 mm2 to 1.570 mm2). And the average taper of blind hole is reduced by 41.7 % (from 0.470 to 0.274). This method can effectively increase the area of exposed copper foil and reduces the taper of blind holes, improve the welding strength and conductivity of wires in aerospace radomes, thereby enhancing the stealth performance and operational reliability of fighter jets.

Geometry accuracy control in abrasive water jet taper hole machining of ultra‐thick carbon fiber‐reinforced polymer (CFRP) laminates

AbstractThe primary factors affecting the geometric accuracy of abrasive water jet (AWJ) machining of ultra‐thick carbon fiber‐reinforced polymer (CFRP) laminates are the cutting front drag and kerf width deviation caused by energy dissipation. Firstly, this study comprehensively analyzes the influence of the coupling relationship between cutting front drag and kerf width deviation on the geometric accuracy of hole machining. Secondly, a gradient distribution theory for jet traverse speed with cutting depth is proposed for taper hole machining characteristics. Finally, a general geometric error model applicable to both straight and taper hole machining of ultra‐thick CFRP laminates using AWJ is established, along with a geometric error compensation method. A series of experiments validate the accuracy of the proposed geometric error model and compensation method. The novelty of this research lies in unifying the geometric error models for straight and taper hole machining of ultra‐thick CFRP laminates by considering the gradient distribution of jet traverse speed. The proposed error compensation method reduces the high degree of freedom required for machine tools. This study provides a general geometric error model and compensation strategy for AWJ hole machining of ultra‐thick CFRP laminates, which has significant engineering value for achieving 3D controllable AWJ machining of complex ultra‐thick CFRP components.Highlights The high geometric precision taper holes machining technique is a necessary prerequisite for achieving precise machining of complex trajectories in ultra‐thick CFRP with abrasive water jet. The influence of the coupling relationship between cutting front drag and kerf taper on the geometric accuracy of hole processing is comprehensively analyzed. A model considering the gradient distribution of traverse speed during taper holes machining was established, and a geometric error model considering this gradient distribution of traverse speed was developed. A taper holes machining geometric error compensation method with high engineering applicability was proposed. Geometric error prediction experiments and error compensation experiments were conducted, and the results proved the accuracy of the geometric error model and error compensation method.

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

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

Investigations on the interaction of laser parameters for efficient microdrilling of NiTiV smart alloy system

Ni–Ti shape memory alloys (SMAs) are popular in current research due to their usefulness and mechanical properties. At different temperatures, Ni–Ti alloys transition from austenite to martensite. To restore high-temperature memory in nickel-titanium SMAs, vanadium (V) is added as an alloying element. For Ni–Ti-based SMAs, the fiber laser is one of the best machining procedures for bio-implants, actuators, and aircraft engine parts. Using a Box–Behnken design to experiment with laser power, nozzle distance, cutting speed, and frequency, this study examines fiber laser micro-drilled Ni50Ti48V2 SM alloy material removal and hole taper angle. By increasing power (P), frequency (F), and cutting speed (C S ), Ni50Ti48V2 alloy material removal rate (MRR) increased by 75.79%. The hole taper angle (HTA) dropped 75.33% when cutting speed, laser power and frequency decreased. Lowering cutting speed and laser power increases micro-hole circularity and reduces HTA. Upon surface topographical inspection, debris and molten materials were found on the drilled surface. The flow of nitrogen gas caused materials to diffuse on the Ni50Ti48V2 alloy’s entry and exit surfaces, changing surface roughness. High parameters influence surface roughness, HTA, and circularity due to nitrogen gas flow. The material’s DSC and XRD tests confirmed its suitability for biomedical microhole production.

Experimental analysis and multi-criteria optimization of process parameters in microwave drilling of kenaf-reinforced polypropylene composites

The present work utilizes the CNC-controlled microwave drilling technique to produce the holes in kenaf-reinforced polypropylene composites. The influence of microwave power and feed rate on the hole characteristics, namely, circularity, overcut, taper angle, and surface roughness was investigated. Stereo microscopic images of the hole entrance and exit were used to evaluate the circularity, overcut and taper angle. Optical profilometer was used to acquire the surface roughness of drilled holes. The TOPSIS, GRA, and MOORA multi-criteria decision making techniques were implemented to optimize the microwave drilling process parameters. The 180 W of microwave power and 145 mm/min of the feed rate were the optimum process parameters to yield the best quality holes in kenaf-reinforced polypropylene composites.

Impact of process parameters in drilling of glass epoxy composite with clam shell and cenosphere filler: A comparative analysis

Drilling is one of the secondary machining techniques most frequently utilised when Glass Fibre Reinforced Polymer (GFRP) materials are assembled into a structure. The present work examines the drilling GFRPs and analyses hole quality based on the different traditional parameters: feed rate, spindle speed, and drill tool diameter. However, the hybridization of glass fiber- reinforced polymers (GRPs) by incorporating fillers as secondary reinforcement in the present piece of research has introduced new challenges for hole drilling and achieving the desired surface finishes. The delamination at the hole entrance and exit, considering the drill diameter of the HSS twist drill (6, 8, 10 mm), feed rate (0.04, 0.08, 0.12 mm/rev), cutting speed (1000, 1200, 1400 rpm), and filler content (0, 10, 20 wt.%) in GFRP, are the major factors are considered. The fillers used are clamshell powder and cenosphere, which are marine waste and thermal power plant waste, respectively. The present paper aims to study the effect of these fillers on the drilling-induced damages to the holes in terms of delamination factor, surface roughness, and dimensional accuracy of the hole (taper error, circularity error) of GFRPs. The most widely preferred Taguchi experimental design has been used for optimising the process parameters to obtain minimum delamination, surface roughness, and hole error. The study also aims to develop a correlation between feed rate, cutting velocity, drill diameter, and filler content with the delamination factor, surface roughness, taper error, and circularity error in a GFRP material. The observed results show that clamshells filled GFRP shows lower delamination, surface roughness, circularity error, and taper error compared to cenosphere filled GFRP composites under the same process parameters. It indicates the positive impact of the fillers in the drilling of GFRP, where the main objective is to reduce drilling-induced defects.

Detecting Cracks on Plates Using Reflections of Fundamental Symmetric and Anti-symmetric Lamb Waves from Defect

Introduction: Ultrasonic Lamb waves can achieve long-range inspection on plate-like structures and can even detect unreachable cracks and defects. There are multiple modes under a certain generation frequency with most of them dispersive. Method: The dispersion curves of Lamb wave in a steel plate were given by numerical calculation. A 2-D finite element (FE) model of a steel plate was promoted. The fundamental symmetric and antisymmetric Lamb waves were generated by uploading symmetrical and anti-symmetrical displacements on one side of the plane. The wave reflects when it comes across the defect and the edge of the plate. Mode conversion will occur after the asymmetrical discontinuities of the structure. Result: The theoretical and numerical results of the values of group velocities of S0 and A0 in a steel plate show well agreement. The maximum amplitude of the converted A0 wave from the interaction of the incident S0 wave with the cracks was observed. The amplitude will first rise then fall under any depth of the defects. The relationship between the defect reflection and the length as well as the depth of defects were simulated based on the FE model. Phase reversion and phase delay were discovered by controlling the defect size changing in one dimension. The reflection coefficient increases linearly with the defect length while the depth is constant, as well as the defect depth while the length is constant. method: Using finite element (FE) method to simulate Lamb wave motion in a plate, as well as experiments on steel plates with artificial defects. Conclusion: Experiments on steel plates with artificial defects including thorough holes and tapered holes were carried out using ISONICA STAR. The results also show that when the defect size changes in one dimension such as the thorough holes, the reflection coefficient increases linearly correspondingly. However, the testing results of the taper holes were inconsistent with the regulation as the size increases in both the length and the depth. result: The values of group velocities were calculated by time-of-flight method to identify specific modes. The results were calibrated and showed well agreement with theoretical data. Mode conversion will appear when the wave comes across asymmetric discontinuities of the structure.

A novel numerical modeling of microsecond laser beam percussion micro-drilling of Hastelloy X: experimental validation and multi-objective optimization

The paper investigates the characteristics of the laser beam percussion micro-drilling (LBPMD) process in aerospace nickel-based superalloy Hastelloy X using microsecond pulses. The quality of the drilled hole is crucial in laser beam micromachining, and selecting appropriate process parameters significantly impacts the hole’s quality. The objective is to achieve predefined hole dimensions with minimal taper angles. Additionally, the study focuses on the alteration of pulse width, which is a combination of laser pulse frequency and duty cycle. Laser power (P), duty cycle % (D), focal plane position (FPP), and laser frequency (f) are considered input parameters, while geometric features such as inlet and outlet diameters, hole taper angle, and inlet circularity are examined as process responses. ANOVA is employed to establish significant relationships between process parameters and response variations based on experimental tests. Creating a precise simulation model that accurately accounts for the moving boundary of the target material’s receding surface is a crucial and challenging task in formulating the laser heat conduction problem. It is necessary to simultaneously capture the material’s dynamic front movement and update the boundary conditions of the laser source. To model the micro-drilled hole with LBPMD, the UMESHMOTION and DFLUX subroutines, along with the arbitrary Lagrangian-Eulerian (ALE) adaptive remesh algorithm in the Abaqus™ software, are utilized. Notably, no previous numerical study has predicted the geometry of micro-drilled holes using this technique. The proposed procedure is validated through the predictions of inlet and outlet hole diameters. Special emphasis is placed on the validation of models. Consequently, the numerical model and statistical model are compared as well as the need to define model applicability. The study demonstrates that all input parameters significantly influence the inlet hole diameter, while the pulse width notably affects the taper angle and circularity. The interaction between high laser frequency and low duty cycle results in reduced pulse duration. Multi-objective optimization is performed to determine the optimal process parameter settings for desired quality characteristics, considering minimum hole taper angle, precise inlet diameter, and maximum inlet circularity of the hole as optimization criteria. The findings show that with the optimized predicted results obtained from the optimal input variables, a composite desirability of 92% can be achieved.

Machining efficiency and geometrical accuracy on micro-EDM drilling of titanium alloy

ABSTRACT In the current study, micro-electric discharge drilling (µEDD) is conducted on a titanium grade 2 alloy using a tungsten carbide (WC) tool electrode of 496 µm diameter. Capacitance, voltage, and feed rate are selected as machining variables to conduct the experiments based on the full factorial experimental design method. Overcut, material removal rate (MRR), circularity, and hole taper are considered as performance measures. Furthermore, overall evaluation criteria (OEC) is utilized for multiple-objective optimization by allotting varying and equal weight percentages to each response measure. The results of OECs are compared with a revolutionary heuristic multi-objective genetic algorithm (MOGA), resulting in a similar optimal parametric combination and close response measures are obtained. Micrographic investigation demonstrates that at lower capacitance and voltage levels, there is less burr formation, recast layer, and circularity error. Moreover, FESEM and EDS analyses are employed to investigate the machined surface topology and elemental composition respectively.

The Effects of Etchant on via Hole Taper Angle and Selectivity in Selective Laser Etching.

This research focuses on the manufacturing of a glass interposer that has gone through glass via (TGV) connection holes. Glass has unique properties that make it suitable for 3D integrated circuit (IC) interposers, which include low permittivity, high transparency, and adjustable thermal expansion coefficient. To date, various studies have suggested numerous techniques to generate holes in glass. In this study, we adopt the selective laser etching (SLE) technique. SLE consists of two processes: local modification via an ultrashort pulsed laser and chemical etching. In our previous study, we found that the process speed can be enhanced by changing the local modification method. For further enhancement in the process speed, in this study, we focus on the chemical etching process. In particular, we try to find a proper etchant for TGV formation. Here, four different etchants (HF, KOH, NaOH, and NH4F) are compared in order to improve the etching speed. For a quantitative comparison, we adopt the concept of selectivity. The results show that NH4F has the highest selectivity; therefore, we can tentatively claim that it is a promising candidate etchant for generating TGV. In addition, we also observe a taper angle variation according to the etchant used. The results show that the taper angle of the hole is dependent on the concentration of the etchant as well as the etchant itself. These results may be applicable to various industrial fields that aim to adjust the taper angle of holes.

Optimization of AWJ parameters for improved material removal and hole geometry in drilling of Glass Fiber/Aluminum mesh epoxy hybrid composites

AbstractThis study explores the application of abrasive waterjet drilling (AWJD) for varied patterns of GF/Al mesh hybrid composites (neat glass NG, AG: Al in the exterior surface, and GA: Al in the center). Key parameters such as jet pressure (P), standoff distance (S), and traverse speed (V) are systematically varied, influencing material removal rate (MRR), hole taper ratio (), and roundness error (). Employing a Taguchi approach with an L9 design. It was indicated that the optimal conditions for maximum MRR are (P: 150 MPa, S: 2 mm, and V: 900 mm/min). V and S are the main influential parameters on and . Gray relational analysis (GRA) is employed for simultaneous optimization, enhancing drilling performance. The optimal parameters P of 150 MPa, S of 2 mm, and V of 300 mm/min are determined. Validation trials confirm the effectiveness of the determined parameters. A robust multiple regression equation is formulated, providing a predictive model that aligns closely with experimental observations.Highlights The hybrid composites were drilled via a nontraditional process. The attributes of the hole geometry and the material removal impacts were studied. Operation parameters were optimized to improve MRR, , and . A multiple regression model and a confirmation test were performed and validated.

Experimental investigation in sustainable electric discharge drilling of Inconel alloy using grey-based fuzzy logic approach

In the present era of manufacturing, sustainable processes are preferred for healthy and ecofriendly environment. To avoid the environmental pollutants and hazardous fumes during the drilling of Inconel-718 alloy, electrical discharge drilling (EDD) process has been used with deionized water as a dielectric medium in the present study. The process performance in terms of metal removal rate (MRR) and hole taper has been controlled by using four process variables such as discharge current, pulseduration, pulse interval and dielectric flushing pressure. The experiments were designed with the help of Box Behnken design (BBD) technique and further, the experimental results have been analyzed to optimize the process performance by using the grey-based fuzzy logic approach. The application of optimization approach has improved the MRR by 62.6% and hole taper is reduced by 20.23%. The parametric study has been carried out to examine the process behaviour with the variation of variables and pulse duration is found as most significant parameter for the study.

Understanding factors affecting the process efficiency, quality and carbon emission in laser drilling of CFRP composite via tailored sequence multiple-ring scanning

Carbon fibre reinforced polymer (CFRP) is increasingly being used in the aerospace, marine, and land transport due to its lightweight, corrosion resistance, and high strength. However, hole drilling during assembly remains challenging due to extensive tool wear and delamination. Laser processing, typically used for drilling and machining, often produces heat effects or is low in efficiency if ultrashort pulse lasers are used. Here, we report an optimised result for a tailored sequence multiple-ring scanning laser drilling method that significantly improves the process efficiency (up to 800 %) by using a continuous wave high power fibre laser operating in pulse mode. Factors such as ring numbers, ring spacing (hatch distance), laser power, and pulse frequency are investigated using statistical design of experiments, and their interactions and effects on process efficiency, carbon emissions, heat-affected zone size, and hole taper are evaluated. The work shows that process efficiency can be significantly increased as the number of rings increases. This is counter-intuitive and would be useful for industrial applications. Using nitrogen as the assist gas results in significantly lower unit process carbon emissions than using argon. The mechanisms behind this efficiency improvement are discussed.

Tunable simultaneous Bayesian optimization of hole taper and processing time in QCW laser drilling

Laser drilling (LD) finds extensive applications in the manufacturing industry, and the improvement of LD quality has been actively pursued by researchers and engineers. However, the large number of tunable processing parameters makes the optimization of LD extremely difficult. In this study, we introduce an innovative approach by applying Bayesian optimization (BO) to tackle the long-standing challenge of multi-dimensional optimization in the field of LD. Moreover, the drilling efficiency was integrated into the optimization objective, representing a crucial metric for practical manufacturing that has frequently been overlooked. As a proof-of-principle demonstration, the drilled-hole taper and processing time were simultaneously optimized relative to four processing parameters in quasi-continuous-wave laser spiral drilling of stainless steel. Results reveal that BO can effectively and efficiently optimize the LD process in a four-dimensional parameter space. Furthermore, we show that the balance between drilling quality and efficiency can be tuned by customizing the objective function. By employing a quality-oriented objective function, the hole taper was significantly improved from 4.3° to 0.8° within just 20 iterations. Meanwhile, with an efficiency-oriented objective function, the processing time was reduced from 13.5 s to 1.6 s. The physical mechanisms underlying how different parameters influenced the drilling process were also discussed. The results in this study reveal the power of BO in multi-dimensional optimization of LD, and the methodology can readily be applied to other laser machining applications.

Parametric optimization of hole taper control in ultraviolet nanosecond laser micro-drilling of copper foil

While hole taper is inevitably formed in the laser micro-drilling of through micro-holes, the formation propensity is largely determined by the interaction between laser processing parameters. In the present work, we perform numerical simulations and experiments to investigate the ultraviolet nanosecond laser micro-drilling of 1 mm diameter through micro-holes on copper foil with a thickness of 280 μm, with an emphasis on the coupled influence of laser processing parameters on both the hole taper and circularity. Firstly, the characteristics of formed micro-hole quality are experimentally characterized, and the formation mechanisms of hole taper are further revealed by finite element simulations of multi-pulse laser ablation. Then, the relational degree of individual laser processing parameters in determining the hole taper and circularity is discovered by experimental investigation based on the gray relational analysis model. Finally, the coupled effect between significant parameters of laser power and repeat scanning number on the hole taper and circularity is further investigated by utilizing the response surface methodology, which derives the optimum laser processing parameters for manufacturing 1 mm diameter through micro-hole with a taper degree of 2.556° and a circularity of 0.992 on the copper foil.

Femtosecond laser drill high modulus CFRP multidirectional laminates with a segmented arc-based concentric scanning method

High modulus carbon fiber reinforced plastic multidirectional laminates (HM-CFRP-MDL) are widely employed in the aerospace industry as crucial structural materials for satellites, rockets, and aircraft. However, it is difficult for the femtosecond laser to drill holes on HM-CFRP-MDL with the traditional concentric scanning method (CSM). To improve drilling quality and precision, this study proposes a segmented arc-based concentric scanning method (SAB-CSM) and investigates the interaction mechanisms between femtosecond lasers and CFRP. By adopting the proposed scanning method with optimized parameters, the overall average HAZ width can be decreased to 10 μm in different regions on the surface of the drilled hole, the hole taper can be reduced significantly, and the consistency across different layers can be improved. Compared to CSM, the HAZ width can be decreased by 40.8 % (12.597 μm to 7.464 μm) and 50.3 % (15.585 μm to 7.748 μm) in the regions where the angles between fiber direction and scanning direction are 45° and 90° respectively, and the taper can be reduced by 34.5 % (0.084 to 0.055). Moreover, the SAB-CSM approach effectively decreases quality discrepancies between different layers, and substantially reduces those defects which results in smooth and uniform hole walls, facilitating synergistic removal of multidirectional carbon fibers and resin matrix.

Effects of water temperature on femtosecond laser layered-ring trepanning in superalloy with water-based assistance

The effects of the water temperature on the hole quality in water-assisted femtosecond laser layered-ring trepanning on superalloys were studied. The effects of the laser pulse repetition rate on the hole entrance/exit diameters, taper angle, and hole sidewall morphology and roughness at different water temperatures were compared and analyzed. The results show that at a water temperature of 70 ℃, the diameter of the hole entrance decreased, while that of the hole exit increased, compared with those at 20 ℃. Both the hole entrance and exit diameters decreased at 2 ℃. The hole taper angle was the largest when the water temperature was 20 ℃, followed by 2 ℃, and was the smallest at 70 ℃. When the laser pulse repetition rate was 300 kHz, the hole taper angle at 70 ℃ decreased by 43.6 % compared with that at 20 ℃. As the water temperature increased, the roughness of each part of the hole sidewall decreased. When the pulse repetition rate was 200 kHz, the quality of the hole sidewall improved under water-based assistance conditions, while the hole quality improved at a water temperature of 70 ℃, compared with drilling in air. As the water temperature increased, the water was more likely to evaporate, resulting in an increase in the amount of bubbles. As more bubbles moved upward, the water flow increased. The debris and materials generated by laser drilling were more effectively removed, thereby improving the drilling efficiency. The use of a higher water temperature was beneficial to obtain holes with smaller taper angles and a higher sidewall quality. The experimental results provide a reference for optimizing water-assisted femtosecond laser drilling. This methodology can be applied to the aerospace and semiconductor industries.

FLUID CHARACTERISTICS AND POLISHING EXPERIMENT OF INCLINED HOLE ARRAY USING ABRASIVE WATER FLOW

Inclined hole arrays on superalloys have important applications in aeroengines. However, defects occur during fabrication of inclined holes using thermal drilling methods, i.e. electrical discharge drilling (EDD), including a recast layer and microcracks on the hole wall. Therefore, abrasive water flow polishing (AWFP) of a superalloy inclined hole array machined via EDD was investigated in this study. Two types of specimens were designed: a hole array of identical size and a hole array with an identical inclination angle. The fluid simulation revealed that the fluid velocity and pressure on the lower edge of the inclined hole were significantly higher than those on the upper edge when the fluid flowed forward. The fluid characteristics exhibited opposite trends when backward flow was implemented. Time-division bidirectional flow can effectively compensate for flow field nonuniformity and improve material removal consistency during polishing. The experimental results show that for inclined holes with identical inclination angles, the size expansion decreases with an increase in the hole diameter owing to the lower fluid velocity and material removal volume in the relatively larger holes. Consequently, surface roughness Ra increases with hole size. For inclined holes with identical diameters, the size expansions of the entrance and exit approach the same level; whereas, Ra decreased with an increase in the inclination angle. The hole taper slightly reduced in all cases. Using garnet abrasives with 1300 mesh size, 1.5 wt.% abrasive concentration, and 3 MPa fluid pressure, the surface roughness Ra of target holes was reduced from pre-polishing [Formula: see text] 5.0 [Formula: see text]m to approximately post-polishing 1.0 [Formula: see text]m. The recast layer on the hole wall caused by EDD was completely removed.