Major aerospace projects such as deep space exploration, manned spaceflight, and Earth observation have strict requirements for large-scale, long-term service, and functionally integrated space equipment. Extravehicular additive manufacturing of large-scale space components provides a promising route to overcoming the payload and fairing-envelope constraints of current launch modes and enhancing the on-orbit service capabilities of future space systems. This perspective intends to clarify the advantages and disadvantages of space extreme force/heat/radiation environments on materials/structures/processes, and to break through the structure/performance control and integrated verification of large-scale components during on-orbit additive manufacturing, which are the core scientific, technological, and engineering application challenges currently faced by space additive manufacturing. This perspective attempts to explore the following scientific issues associated with space additive manufacturing, including establishing a material-structure integrated design and manufacturing theory for large-scale space components, constructing principles and methods for on-orbit additive manufacturing, and building ground simulation and equivalent verification methods for space additive manufacturing. These studies have strategic significance for exploring the endless scientific frontiers of space manufacturing and enhancing aerospace manufacturing capabilities.
High-speed laser-based directed energy deposition (DED-LB) is increasingly pursued for efficient repair and manufacturing of high-value metallic components, yet its process window remains limited by unstable powder capture, melt-track discontinuity and defect formation. Existing studies have mainly interpreted these instabilities through melt-pool thermal history and empirical parameter optimization, while powder delivery is commonly treated as a passive mass-input boundary. To address the lack of a generalizable physical basis for powder transport and deposition-mode transition in high-speed DED-LB, this study combines controlled moving-nozzle and rotating-substrate experiments with high-speed imaging, powder-cloud statistics and computational fluid dynamics (CFD) modelling. We identify scanning-induced powder–gas entrainment as an active transport mechanism that reconfigures the powder stream before particles enter the melt pool. Increasing scanning speed generates a co-moving carrier-gas flow, breaks the symmetry of powder delivery and shifts the powder convergence region upward from the melt-pool capture zone. Under an unchanged optical focal position, the convergence centroid increases from 2.438 mm to 2.812 mm, producing a powder-mediated defocus state that spatially decouples laser–powder interaction from melt-pool capture. This spatial decoupling changes particle residence time and thermal history in the laser beam, thereby triggering a transition from conventional melt-pool capture deposition to in-flight droplet deposition. The droplet-dominated regime modifies melt-pool thermal conditions, defect formation, solidification response and local mechanical properties of the deposited C22 alloy. This work establishes a mechanism-level framework linking powder–gas entrainment, powder-field reconfiguration and deposition-mode transition, providing a physical basis for controlling powder–laser–melt-pool coupling in high-speed DED-LB.
Conventional layer-by-layer manufacturing approaches using uniform energy inputs generate homogeneous microstructures, which intrinsically restrict their sensitivity and linearity for mechanical sensing, particularly within the low-pressure range. This study introduces a rapid (within just 5 min) and flexible acoustically directed manufacturing strategy, referred to as directed acoustic construction (DAC), for producing microstructures with spatially graded properties. The DAC mechanism is based on acoustic cavitation generated by ultrasonic mechanical vibrations. Cavitation bubble collapse releases localized energy that promotes curing through acoustic chemical polymerization initiated by cavitation-derived radicals, while the accompanying microjets transport and deposit the cured units onto the substrate. The incorporation of diamond particles enhances acoustic scattering and diffraction, leading to coherent superposition, thereby strengthening cavitation and acoustic chemical effects, and expediting curing. By regulating the ultrasonic energy, the internal polymerization and cross-linking networks in selected local regions of diamond/PDMS composites can be modulated during curing. As a result, pillar, hemispherical, and conical array microstructures are fabricated, each exhibiting a lateral gradient in elastic modulus. These gradient features allow the microstructure to reach a high sensitivity of 51.49 kPa−1 (0–2 kPa), which is 58.43% greater than that of homogeneous microstructures. The fabricated sensor can detect weak physiological signals (e.g., pulse, swallowing, and respiration) and mechanical vibrations. The DAC strategy allows one-step modulation of local mechanical properties within microstructures, thereby overcoming the uniform-deposition limitation of layer-by-layer methods. This approach provides new route for functional devices, such as sensors, metamaterials, and bioinspired structures that require site-specific property modulation.
Simultaneous double-sided friction stir welding (SDS-FSW) improves through-thickness thermo-mechanical symmetry in medium- and thick-section structures, yet internal defects often form near the mid-thickness rather than at the weld root, while the origin of this defect-sensitive region and the condition separating stable consolidation from defect initiation remain unclear. To address this issue, a coupled thermo-mechanical-material transport model incorporating a ploughing-enhanced interfacial friction formulation was established by integrating Eulerian–Lagrangian modelling with tracer-particle analysis. The results show that temperature modulates local resistance to material flow, equivalent plastic strain characterises accumulated deformation, and tracer trajectories resolve material delivery and refill-path connectivity. The shoulders provide the dominant inward and downward material supply, whereas the pins mainly induce localized recirculation, creating an intrinsic transport bottleneck at the shoulder–pin transition. A local loss of refill continuity produces an isolated void; persistence of the interruption along the welding direction produces a tunnel, while its extension towards the free surface results in a groove. Based on this mechanism, plunge-depth regulation and pin-thread optimisation were proposed as complementary defect-suppression strategies. In the respective suppression trials, a plunge depth of 0.15 mm and a coarse-thread pin effectively suppressed visible defects and yielded ultimate tensile strength improvements of at least 4.0%. These findings establish a physical basis for process-window design, tool-geometry optimisation, and defect control in SDS-FSW.
Shape memory alloys (SMAs) exhibit exceptional functional properties, but their service performance depends strongly on surface integrity and the stability of martensitic transformation. Traditional low-speed wire electrical discharge machining (WEDM-LS) inherently produces a thick recast layer (RL), high residual tensile stress, and surface microstructural damage, thereby degrading functional performance and service reliability. To overcome these limitations, an ultrasonic vibration and magnetic field assisted hybrid wire electrical discharge and electrochemical machining process (USV-MF assisted hybrid WEDM-ECM) was proposed to improve the surface integrity and functional performance of SMAs. To quantitatively predict microstructural evolution across multiple length scales, a cross-scale framework was established by integrating finite element, crystal plasticity finite element, and multilevel cellular automaton (FE-CPFE-MCA) models. Systematic analyses were performed in conjunction with a multi-gradient closed-loop characterization of material characteristics under different processing conditions, spanning macroscopic surface morphology, microstructural evolution, and dislocation behavior. On this basis, novel phenomenological behavior induced by multi-physics was identified, and the evolution pathways of microstructure and functional performance during treatment were elucidated in terms of the underlying mechanisms. The results indicated that performance enhancement was primarily attributed to RL thinning, improved reversibility of martensitic transformation, and the formation of gradient structures. The high reliability of the cross-scale predictions was further validated by in situ EBSD. This study provides a theoretical foundation for the high-quality fabrication and performance control of thin-walled, micrometer-scale precision components manufactured from SMAs and other phase transformation-sensitive metals, with particular applicability to precision medical implants.
Achieving precise geometric control in the forming of complex ultrathin-walled components remains a persistent challenge due to the intricate coordination of multi-process parameters. Critically, the underlying mapping mechanism between geometric evolution and failure initiation has not been fully elucidated. This study proposed a novel analytical framework that quantitatively reveals the nonlinear coupling effects of process parameters on geometric evolution and defect transitions in ring hydroforming. Combining finite element simulations and experiments, the deformation behavior at each stage of the ring hydroforming process was analyzed. Obvious wall thinning was observed during the pre-bulging and feeding-bulging stages. The pressure and displacement exhibited a coupling effect on the geometric shape, the inappropriate loading paths of them may lead to geometric defects such as insufficient height or material accumulation. Based on the mechanical analysis through static equilibrium relationships, the geometric contour evolution characterization models that mathematically characterize the cross-sectional shape transition from circular to elliptical to U-shaped profiles were established, which were utilized to quantify the interrelations among process parameters and cross-sectional shape changes. Furthermore, by integrating critical constraints including minimum plastic deformation pressure, maximum burst pressure, geometric folding and excessive thinning, a 3D "displacement-bulging height-pressure" parameter-defect mapping space was constructed to visually analyze intrinsic relationship. Displacement and pressure exert a non-linear coupled influence on geometric evolution and defect formation. Specifically, an increase in pre-bulging pressure diminishes the driving efficacy of axial displacement on bulging height, explicitly resulting in a contraction of the parameter-defect mapping space. As the cross-sectional profile evolves, the dominant failure mechanism shifts from excessive thinning to either bursting or geometric folding, with the transition point determined by component geometry and loading history. The M-shaped ring, triple-peak ring and multi-wave corrugated flattened tube were successfully manufactured under loading paths designed within the contracted mapping space. Comparative analysis of experimental, simulation and geometric model results regarding cross-sectional profile evolution and wall thinning distributions further validates the mechanistic insights and demonstrates the framework's potential for guiding high-precision forming of complex ultrathinwalled components.
Laminated sheet metal parts comprise two or more substrate sheet metals to leverage the respective performance advantages, yielding superior overall performance with wider application prospects compared to single-layer parts. However, traditional manufacturing methods for sequentially bonding and forming extend development cycle time with poor part performance. In the present work, a novel hybrid manufacturing method synchronizing incremental sheet forming with friction stir additive manufacturing for laminated sheet metal parts is proposed. Through experiments, microstructural characterization and mechanical testing, the influence of process parameters on the mechanical properties and microstructure of heterogeneous materials are investigated. Inspired by biological structure, multiple heterogeneous structures are introduced to enhance the mechanical properties and bonding performance, including dual-gradient grain and bimodal grain structures in material matrix and interlocking corrugated texture at the Steel/Al interface. The dual-gradient grain structure from surface to interior of steel matrix reflects a transition from grain refinement to dynamic recrystallisation. The coarse grains in bimodal structure of aluminum matrix underwent severe plastic deformation with significant precipitation behavior and the ultrafine grains exhibit recrystallisation behavior along with numerous stacking faults. It is also found that the average misorientation value in the corrugated interface is markedly higher than those in material matrix, along with abundant dislocations and twin structures within interfacial compound layer. Both yield strength and shearing strength of laminated sheet materials significantly increase with rising pre-strain and interface corrugation, reaching 437 MPa and 112 MPa at a pre-strain of 0.30 and corrugated amplitude of 10 mu m, respectively and encompassing those of laminated materials by conventional processes reported. This work reveals a fundamental mechanism that heterostructure-induced stress partitioning contributes to the synergistic enhancement of mechanical property and interfacial bonding, with the contribution rate of back stress reaching 76% of yield stress. Finally, case studies demonstrate the proposed process realizes integrated forming-bondingadditive manufacturing of laminated sheet metal parts with short cycle time, enabling the in-situ engineering of multi-scale heterogeneous structures to simultaneously improve strength and bonding performances.
The efficient and accurate fabrication of large-area periodic nanostructure arrays is of great significance for numerous applications, yet it remains a substantial challenge. An enhanced nanoimprinting technique is presented that utilizes a structured indenter with constant-force modulation to achieve large-area patterning of nanostructured arrays on metallic surfaces. FIB-fabricated nanostructured indenters with three different tip spacings were employed for constant-load nanoimprinting of single-crystal copper along three different orientations. First, an elastic-plastic contact mechanics model is developed to predict multi-tip nanoimprint depths under a constant normal load. The model accounts for inter-tip interactions and material crystal orientation, and its accuracy and robustness are validated experimentally and against existing models. Second, compared with a single-tip indentation, multi-tip indentation exhibits a coupled load-depth response: the required load is lower than the sum of the single-tip elastic loads but higher than the sum of the plastic loads. Plastic events occur without pop-in, and unloading shows greater elastic recovery. Subsequently, at a small spacing ratio (K = 1.25), strong tip-tip interference results in a substantial overlap between plastic zones and stress fields. This, in turn, intensifies confined plastic flow, elevates strain gradients, and promotes the formation of pile-up and grain boundaries. The transition in plastic interference from strong (K = 1.25) to weak (K = 1.5) and negligible (K = 2) was analyzed by varying the tip spacing ratio (K). Moreover, crystallographic orientation appreciably modifies the depth response and surface morphology. The (110) surface exhibited the maximum imprint depth, reflecting orientation-dependent slip activity combined with tip interference. These results offer crucial insights into the nanoimprinting mechanisms of single-crystal metals and provide a solid theoretical foundation for the precise fabrication of high-quality nanostructure arrays.
Flexible solar cells, featured by lightweight and bendable properties, have emerged as the ideal material for next-generation spacecraft power systems. Solar cells are joined via interconnectors to form solar cell arrays, where joining quality determines system reliability and lifespan. However, conventional parallel gap resistance welding, a standard method for rigid solar cells, often leads to weak joints and cell damage when applied to flexible solar cells. Both the joining quality and cell damage are essentially governed by the thermo-mechanical synergistic action. However, the underlying mechanisms by which this action impacts interfacial joining and cell damage remain poorly understood. Without a sound theoretical basis, process development is severely restricted. This study first systematically elucidated the joining and cell damage mechanisms in parallel gap resistance welding of flexible solar cell-interconnector. Results indicated that the parallel gap resistance welding relied on instantaneous solid-state interdiffusion, requiring a peak temperature of similar to 700 degrees C to achieve atomic bonding and minimize interfacial defects (micro-voids and micro-gaps). Nevertheless, the high temperature induced softening and compressive deformation of the polyimide substrate in the weld zone, causing stress concentration and cracking in the semiconductor. Additionally, the thermal effect accelerated the GaAsIn-Au interdiffusion, forming Au-In liquid at the weld center; this liquid migrated outward and solidified, resulting in semiconductor-substrate debonding. Based on these findings, a parallel gap resistance soldering method was proposed. A single-micron Au-Ge alloy layer was plated on the interconnector as a solder layer to lower the required joining temperature and suppress the formation of brittle intermetallic compounds that degrade long-term reliability in space environments. Meanwhile, localized pulsed heating generated by the parallel gap resistance welder was utilized to achieve reliable interfacial joining with minimized thermo-mechanical impact. The joining mechanism was transformed from solid-state interdiffusion to liquid-solid interdiffusion coupled with epitaxial growth. This approach not only eliminated interfacial defects but also reduced the critical joining temperature to similar to 395 degrees C, effectively avoiding cell damage including cracking and debonding. Compared to parallel gap resistance welding, parallel gap resistance soldering achieved an similar to 11-fold increase in joint peel peak load and expanded the welding window by 200%. This work provides an innovative strategy for achieving intermetallic-free, defect-free and damage-free interconnection of flexible solar cells, and promotes the advancement of micro-joining technology for components sensitive to thermo-mechanical action and requiring long-term service in extreme environments.
The demand for full-spatial-frequency, nanometer-precision machining of complex freeform surfaces across various materials has been rapidly increasing in fields such as extreme ultraviolet (EUV) optics, large synchrotron-radiation facilities, astronomy, and precision metrology. Compared with conventional contact machining, non-contact jet-based processes have attracted wide attention from their high processing flexibility and damage-free characteristics. Among them, atmospheric-pressure plasma chemical vaporization machining (AP-PCVM) has been widely applied for ultra-precision figuring of optical components, benefiting from its chamber-free operation and high etching efficiency. To enhance figuring accuracy in the low-spatial-frequency region, PCVM employs a small-diameter plasma jet to achieve higher spatial resolution; however, such configurations often cause surface roughness deterioration in the high-spatial-frequency region. The underlying mechanism remains unclear and severely limits its further advancement and applications. In this study, the mechanism behind surface roughness deterioration was clarified by combining experimental analysis with CFD simulation. It was found that a small-diameter jet intensifies the near-surface shear layer, triggering KelvinHelmholtz (K-H) instabilities that continuously generate vortices which rapidly evolve into unsteady threedimensional structures. The resulting sweep, lateral refresh, and ejection regions locally enhance the convective-diffusive mass transfer of species toward and away from the surface, causing meso-to-micro-scale nonuniformity in material removal, and ultimate surface roughness deterioration. Multi-dimensional surface characterizations further confirmed that this deterioration originates from vortex-shaped etch pits, validating the proposed mechanism. Based on the revealed vortex-induced mechanism, suppressing the vortex strength and occurrence frequency effectively mitigates vortex-induced roughness deterioration of PCVM, providing a mechanism-driven optimization pathway for small-diameter jet figuring process design.
To address multi-dimensional geometric deviations in extruded profiled thin-walled hollow members, which are challenging to correct using traditional processes, this study proposes an axial hydro-extrusion method based on a novel stress-transformation mechanism for synchronous control of multi-dimensional deviations. Unlike traditional tensile-based forming, this process induces global plastic extrusion deformation through axial feeding under internal pressure, transforming non-uniform axial, circumferential, and shear stresses into a nearly uniform and predominantly compressive stress state. This shift eliminates stress gradients, thereby controlling deviations in different dimensions and enabling synchronous outer contour correction of the hollow member. First, the effect of stiffeners on wrinkling and shape accuracy of the outer contour of the hollow member in axial hydro-extrusion is analysed, establishing a critical instability internal pressure model. Next, stress states generated by different geometric deviations during fitting die deformation and their changes during axial extrusion are investigated through theoretical and simulation methods, clarifying the reasons for deviation changes in different dimensions. Additionally, a critical extrusion displacement model incorporating work hardening is developed to quantify the stress transformation process and analyse the effects of initial deviations on critical extrusion displacements. Finally, a specialised axial hydro-extrusion forming platform is designed for single-cavity and multi-cavity hollow members with various deviations, achieving over 95% reduction in dimensional deviations. This study provides a new strategy for solving the problem of multi-dimensional geometric deviation synchronisation control in complex thin-walled hollow members.
High-precision finishing of hard-brittle materials requires the simultaneous control of submicrometer form and nanometer-scale roughness, ideally with high yield and low consumable usage. Noncontact beam-based processes such as laser machining can avoid tool wear, reduce reliance on contact consumables, and relax tool-access constraints. However, deterministic finishing at the waviness and roughness scales remains difficult when the effective material-removal response varies with local absorption, near-surface state, and accumulated irradiation. Conventional laser finishing approaches are typically performed either in open loop or with between-cycle corrections based on offline surface metrology and an assumed stationary removal function, and are therefore vulnerable to such uncertainty. Here, this study examines whether deterministic surface-quality control in laser finishing can be achieved by using in-process surface metrology and feedback, without relying on a precisely calibrated removal function. To this end, we propose an on-machine interferometric feedback framework in which white-light interferometry (WLI) defines a virtual reference surface, a residual height map is computed after each iteration, and irradiation sites are replanned to selectively remove protrusions. Implemented with femtosecond-pulse ablation, the closed loop achieved convergent reductions in both the residual metric and the surface roughness during planarization of single-crystal diamond (SCD). In two experiments on chemical-vapor-deposition-grown SCD, the areal roughness Sa decreased from 82.6 to 23.1 nm and from 129 to 44.3 nm, with the minimum-roughness states reached after seven to eight iterations. The roughness-improvement ratio Delta S-a/Delta z reached 0.493 to 0.900, which is one to two orders of magnitude higher than values reported for representative open-loop laser-polishing processes. Loop-to-loop scatter in removed volume and single-point tests on rough and smooth surfaces showed that the effective material-removal response is topography dependent, explaining why iterative replanning from measured residuals is beneficial. Post-machining roughness measured by WLI agreed with measurements obtained by atomic force microscopy, supporting quantitative in-process evaluation under evolving surface-optics conditions. The attainable roughness was ultimately bounded by two coupled mechanisms: irradiation-induced loss of fringe visibility in WLI and residual laser-induced periodic surface structures. These results establish adaptive replanning as a measurement-driven route to deterministic, high-yield, noncontact laser polishing under non-stationary material removal.
The six-degree-of-freedom series structure of robots has brought a series of advantages such as excellent processing flexibility, large working space, and in-situ processing. In recent years, it has seen significant development and is gradually being applied across multiple critical fields. However, the manufacturing demands for large components pose significant challenges to robotic machining efficiency and quality. The inherent drawbacks of the six-degree-of-freedom serial structure—insufficient dynamic rigidity, low static stiffness, and significant pose-dependent stiffness variation of the robot body—have increasingly emerged. The machining dynamics issues caused by the robot body compliance need to be given priority attention. On the other hand, as the part of the robotic milling system that directly contacts the workpiece, the tool section is also of great significance to conduct research and analysis on the machining dynamics issues caused by its compliance. Therefore, the robotic milling system is a multi-source compliant system, influenced by multiple compliant components simultaneously, and even at relatively high tooth passing frequencies, the robot body compliance is still excited. Discussing and comparing the characteristics and distinctions of research focusing on different compliant components in terms of dynamic characteristics, machining stability, and chatter suppression, for further in-depth exploration of robotic machining dynamics, forming a theoretical framework of machining dynamics with the distinctive robotic characteristics has significant guiding significance. However, there is still a lack of detailed, specific and clear reviews on robotic machining dynamics centered on the multi-source compliance characteristics of robots. Therefore, this review will comprehensively summarize and review the related research on dynamic characteristics, stability and chatter suppression in the field of robotic machining dynamics from a new perspective of multi-source compliance. Concurrently, it will summarize existing challenges in robotic machining dynamics research while outlining future development directions.
The fundamental challenge in modeling thermally induced deformations in advanced manufacturing lies in resolving the trade-off between black-box data-driven approaches and physical interpretability. While high predictive accuracy is essential, stringent transparency is equally required to ensure industrial reliability. To bridge this critical gap, this paper introduces a generalized, physics-informed interpretable modeling framework driven by the Dynamic Temporal Kolmogorov-Arnold Network (DT-KAN). We apply this methodology to the characterization, prediction, and real-time compensation of six-degree-of-freedom (6-DOF) thermal errors in precision CNC machine tools. These errors remain a persistent challenge in novel coaxial dual-lead feed drive systems due to complex macro-micro thermo-mechanical coupling. The proposed DT-KAN synergizes explicit physics-based temporal feature engineering with a learnable activation function architecture. Unlike standard multi-layer perceptrons (MLPs), the network replaces fixed weights with learnable B-splines on its edges. This structural shift enables the autonomous extraction of high-fidelity functional mappings while preserving the physical inductive biases associated with thermal superposition. Under rigorous cross-validation with unseen operating conditions, the DT-KAN achieved a coefficient of determination (R2) of 0.958 and a root mean square error (RMSE) of 0.91 & micro;rad, significantly outperforming benchmark models in both accuracy and parameter efficiency. Beyond exceptional predictive performance, the model offers superior interpretability by autonomously decoupling underlying physical mechanisms. It explicitly identifies cumulative heat as the driver of thermal memory, and thermal gradients as the source of dynamic hysteresis. Finally, the industrial viability of the framework was validated through a closed-loop, real-time compensation system on a dual-drive grinding center. The proposed method reduced the maximum volumetric error from 31.6 & micro;m to 5.2 & micro;m (an 83.5% improvement), effectively restoring the system to its cold-state accuracy. Practical precision grinding trials of linear guide sliders further confirmed that this approach ensures process stability and zero-defect rates under thermally unstable conditions. These findings highlight the immense potential of interpretable modeling as a pathway to transparent and reliable thermal error compensation in modern manufacturing.
To address the dilemma between high-defect susceptibility of fusion-based additive manufacturing (AM) and the process-interruption sensitivity of solid-state AM for the high-strength AA7075 alloys, this study reports a hybrid manufacturing technology. It applies cyclic interlayer friction stir processing (C-IFSP) during laser directed energy deposition (LDED). The fundamental advancement lies in establishing a thermomechanical strategy that couples defect elimination and microstructural heterogeneity control, enabling in-situ architectural design of grain size and precipitate distributions across multiple length scales. Two contrasting C-IFSP strategies, unidirectional (UC-IFSP) and reciprocating (RC-IFSP), were systematically investigated. Both eliminated LDED-entrapped pores (porosity reduced by similar to 4 and similar to 7 orders of magnitude, respectively), but divergent thermomechanical transients yielded markedly different heterostructures: UC-IFSP produced laminated ultrafine/fine-grained layers along the build direction, whereas RC-IFSP established a bimodal grain structure with additional transverse heterogeneity. Consequently, RC-IFSP achieved synergetic enhancement of strength and ductility in the transverse direction while reducing strength anisotropy by 21.7%, reconstituting the strengthening mechanism from nanoprecipitate-dominated (wrought plate) to a synergistic strengthening of precipitate, dislocation, fine-grain, and heterogeneous deformation. This work establishes a pathway for defect-free, hierarchically controlled AM of high-strength Al alloys through spatially programmed thermomechanical processing.
Aluminium nitride high-temperature co-fired ceramic (AlN HTCC) is a promising substrate material for electronic packaging, and the fabrication of microchannel arrays on its backside can significantly enhance its heat dissipation performance. However, the high hardness and brittleness of AlN present considerable challenges in the machining of microstructures. Therefore, this study proposes a hydrochloric film-assisted laser processing (HFALP) technique. Initially, a systematic analysis was conducted on the multi-factor energy attenuation mechanism of laser beams. Based on this, a temperature distribution model capable of accurately predicting the line-etching morphology was developed. Furthermore, through transient observations, flow field simulations, and comparative experiments under different liquid phases, this study reveals, for the first time, the intrinsic relationship between the cavitation bubble dynamic behaviour, laser, and liquid layer. This leads to the clarification of two material removal mechanisms, tunnel channel ablation and cavitation ablation, induced by multi-mechanism synergy within the ternary system of “laser-reactive medium-thermally-active material”. Finally, narrow microgrooves with an aspect ratio of 8.6:1 were successfully fabricated on AlN by coupling the two ablation mechanisms. Compared with laser chemical milling, HFALP improved the machining depth, mean deviation of the contour, and processing efficiency by 41.24%, 30.11%, and 3845.2%, respectively, and achieved stable fabrication of microchannel array structures with a profile deviation of only 0.1%. This study not only provides a reliable process for the thermal management application of AlN but also, through successful validation on other reactive materials, establishes a universal theoretical framework for “reactive medium-assisted laser processing”. This offers reusable technical pathways and mechanistic support for efficient and high-quality machining of various thermally-active materials.
This paper presents an electromagnetic active workpiece holder (EAWH) and demonstrates its feasibility for both rough-and finish-milling operations. While most research on active workpiece holders (AWHs) relies on piezoelectric stack actuators due to their compact size and high internal stiffness, their stroke is limited, and heavy-duty operation often requires large motions and high-voltage driving, which can introduce additional design challenges for an AWH system. Electromagnetic actuators (EMAs) can provide large compensatory strokes and robust high-force actuation with simple drives, but their lack of inherent stiffness has kept prior EMA-based AWHs mostly in low-force applications. To address this gap, we propose a reluctance-actuator-based EAWH that combines large stroke with high force capacity. With a stroke exceeding +/- 100 mu m and a maximum force of 3812 N in both the X and Y directions, the proposed EAWH effectively compensates for large-amplitude tool vibrations while withstanding high cutting forces during rough-milling. Rough-milling experiments show that the EAWH suppresses unstable chatter and doubles the chatter-free cutting depth compared with the uncompensated case. For finish-milling, we propose a compensation strategy targeting the forced vibrations induced by the spindle bearing retainer, and experiments demonstrate that the undesired surface marks are eliminated, reducing the surface roughness by up to 46.5%. Overall, the results demonstrate that the EAWH and the proposed strategies can support modern machining centers that integrate high-throughput roughing and surface-finish improvement under finishing conditions within a single platform.
Through-mask electrochemical discharge machining (TM-ECDM) is developed to create micro-scale features on non-conductive materials. In this method, a metal mask is used as a tool electrode to induce electrochemical discharges on unmasked regions of workpiece. The discharges induce heating, which activates localised chemical etching. A workpiece-electrolyte interfacial gas layer model, consisting of an inner non-ionised bubble layer and outer discharge layer, is established. The mechanisms governing discharge localisation within the gas layer are clarified through simulation. Reducing the pattern width increases the gas layer thickness, altering the spatial distribution of discharges. Reduced mask thickness and accelerated bubble detachment, such as in cylindrical geometries, promote discharges closer to the machining surface. The distance of the discharge layer from the workpiece surface strongly influences the machining process. A thermal transport model describing heat transfer from the discharge layer to the machining surface across the inner non-ionised bubble layer is proposed, revealing the resulting surface temperature distribution. Experiments confirm that TM-ECDM proceeds via a chemically dominated etching mechanism, achieving a maximum vertical etching rate of 12 mu m/min. The machined single-crystal quartz exhibits only an similar to 20 nm amorphous subsurface layer, indicating near-damagefree processing. Additionally, very low surface roughness (Ra <35 nm) can be achieved. These findings reveal a new electrochemical discharge-regulation mechanism and establish a novel through-mask strategy for structuring insulating materials.
