Additive Subtractive Manufacturing Research Articles

Integrated laser alloying-grinding for additive-subtractive manufacturing of Ti6Al4V surface with B4C coating

Integrated laser alloying-grinding for additive-subtractive manufacturing of Ti6Al4V surface with B4C coating

Research Progress in Shape-Control Methods for Wire-Arc-Directed Energy Deposition.

Wire-arc-directed energy deposition (WA-DED) stands out as a highly efficient and adaptable technology for near-net-shaped metal manufacturing, with promising application prospects. However, the shape control capability of this technology is relatively underdeveloped, necessitating further refinement. This review summarizes the latest advancements in the shape control of WA-DED technology, covering four pivotal areas: the regulation of various process parameters, optimization of the deposition paths, control through auxiliary energy and mechanical fields, and synergy between additive and subtractive manufacturing approaches. Firstly, this review delves into the influence of deposition current, travel speed, wire feed speed and other parameters on the forming accuracy of additively manufactured parts. This section introduces control strategies such as heat input and dissipation management, torch orientation adjustment, droplet behavior regulation, and inter-layer temperature optimization. Secondly, various types of overlap models and techniques for designing overall deposition paths, which are essential for achieving desired part geometries, are summarized. Next, auxiliary fields for shape and property control, including magnetic field, ultrasonic field, and mechanical field, are discussed. Finally, the application of milling as a subtractive post-process is discussed, and the state-of-the-art integrated additive-subtractive manufacturing method is introduced. This comprehensive review is designed to provide valuable insights for researchers who are committed to addressing the forming defects associated with this process.

Influence of the Cooling Temperature on the Surface Quality in Integrated Additive and Subtractive Manufacturing of Aluminum Alloy.

The surface quality of parts processed by laser additive manufacturing, especially laser-based directed energy deposition (LDED), makes it difficult to meet actual use requirements. In addition, defects generated during the long-term additive manufacturing process need to be removed in time. Therefore, laser additive and subtractive manufacturing is of great significance for additive manufacturing. The main difference between laser additive-subtractive manufacturing and pure subtraction is that a cooling temperature is required due to the laser process. Therefore, this work studies the temperature variation regularity during LDED and the milling processes, as well as the surface roughness, cross-sectional microstructure, and tool wear under different cooling temperatures for milling. The results show that there is a "turning point temperature" in LDED, and the value of the turning point temperature gradually increases with heat accumulation, which affects the initial temperature of the subtractive manufacturing. When subtracting, a high initial temperature improves surface quality and reduces tool wear, but an excessively high temperature will cause the aluminum alloy to adhere to the tool. Then, the smear metal is difficult to effectively remove, deteriorates the milling quality, and aggravates tool wear. It is found that the higher the cooling temperature generated, the wider the thermally insulated shear band. The insulated shear band may affect the quality of the additive and subtractive manufacturing. Finally, it is determined that the milling temperature of aluminum alloy in this work condition is about 100 °C.

Developing a hybrid-built pre-hardened alloy steel for injection moulding tools using the laser powder bed fusion process

Hybrid additive-subtractive manufacturing has been adopted as a cost-effective alternative for manufacturing plastic injection moulding tools with conformal-cooled inserts created by fusing powder and wrought material. This article reports the development of a hybrid power-wrought pre-hardened alloy steel to supplement the current material choice for fabricating injection mould inserts using this advanced manufacturing strategy. In this study, MS1 (maraging 300) steel powder was additively deposited onto pre-machined wrought Nimax steel to form a hybrid alloy material. The mechanical and microstructural properties of the fusion-bonded interface were examined. Microstructural observation revealed a 280 μm thick interfacial region consisting of a homogenous mixing of powder and substrate materials. As a result of solid solution strengthening within the region, tensile tests established robust powder-substrate bonding with tensile ruptures occurring well away from the interface. The as-built hybrid-alloy steel possessed excellent mechanical properties, with 1200 MPa in ultimate tensile strength, 12.4 % in elongation at fracture and 39 HRC (Nimax)/42 HRC (MS1) in hardness. The overall results suggested that hybrid MS1-wrought Nimax steel is a suitable pre-hardened material for manufacturing durable and high-performance injection mould inserts as part of a cost-effective hybrid additive-subtractive manufacturing strategy.

Hybrid additive-subtractive manufacturing of high-density copper-based flexible transparent circuits based on side-etch process

High-density flexible transparent circuits (FTCs) are widely used in 5G/6G flexible transparent antennas, wearable devices, flexible transparent electronics and other fields. However, the rapid iteration and upgrading of electronic circuits present significant challenges to the manufacturing of both high-density and high-precision circuits (especially copper-based circuits) at room temperature, in an efficient and flexible manner. Here, we employ the side-etching phenomenon, which is typically avoided, to propose a novel method for hybrid additive-subtractive fabricating high-density copper-based FTCs that combines electric field-driven (EFD) microjet printing and wet etching technology. Firstly, the customized photoresist mask was flexibly printed on the copper-clad flexible substrate by EFD microjet printing, and then the copper circuit with less than the mask resolution was obtained by the side etching process of the wet etching process. By optimizing process parameters and precisely controlling the speed of the side etching stage during the etching process, the manufacturing of high-precision copper-based FTCs with a minimum line width of 2.4 μm and a minimum pitch of 4 μm was achieved. The typical sample is manufactured with a resistivity of 4 × 10−6 Ω·cm, a sheet resistance of 3.58 Ω/sq at a transmittance of up to 87.65 % (including the substrate), and it exhibits excellent mechanical stability. The prepared high-density flexible transparent interdigital electrode has excellent sensitivity, and can detect the concentration change of dilute H2SO4 solution at a minimum of 1 nmol/L at a frequency of 100–10,000 Hz. This method provides a new solution for the fabrication of copper-based FTCs at room temperature with high efficiency and low cost, and shows a good prospect for industrial application.

Enhancing surface quality and tool life in SLM-machined components with Dual-MQL approach

Selective laser melting (SLM) can produce complex metal components with high densities, thereby surpassing the limitations of traditional machining methods. However, achieving accurate dimensions, geometries, and acceptable surface states in parts fabricated through SLM remains a concern as they often fall short compared to traditionally machined components. As a solution, a hybrid additive-subtractive manufacturing (HASM) method was developed to effectively utilize the advantages of both techniques. In this study, SLM-made 316 L stainless steel was machined under distinct cooling conditions to investigate the effects of roughness and tool wear. After a thorough investigation, the dual-MQL strategy was evaluated and compared with dry and MQL cutting strategies. The findings showed that the dual-MQL condition led to a significant reduction in flank wear by 54–56% and 29–34%, respectively, associated with dry and MQL cutting techniques, making it a highly promising key for machining SLM-made steel components. Machine learning techniques are potential tools for prediction and classification capabilities in machining processes. For milling SLM-made 316 L SS, multilayer perceptron (MLP) proved to be the most effective prediction model and for classification MLP and Random forest performed better.

The influence of deformation affected region on microstructure and mechanical property of 316L fabricated by hybrid additive-subtractive manufacturing

The hybrid of additive manufacturing and subtractive manufacturing is promising in producing high-quality and high-accuracy parts made of hard-to-machine metallic materials with complex geometries. However, few studies have been conducted to analyze the influence of responses from subtractive manufacturing, especially the plastic deformation region induced by mechanical cutting, on the following additive manufacturing processes. This paper comprehensively investigates the impact of finishing milling on the mechanical properties and quality of 316L fabricated by hybrid additive-subtractive manufacturing. The whole manufacturing process consisted of a two-stage micro selective laser melting μSLM process with three scanning speeds and one finishing milling process. Typical machining responses including phase, cutting force, surface roughness at different manufacturing stages were analyzed; the mechanisms of how the deformation-affected region induced in subtractive manufacturing process affects the microstructure, hardness, and mechanical properties after the second-stage additive manufacturing were explored. Fine grains were formed after the second-stage μSLM in the connected region, because of the lower G/R ratio and the higher G × R value, whereas the hardness in this region was lower than the bulk material consisting of coarse grains, caused by the thermal softening effect induced in mechanical cutting. The elongation rate was increased due to the existence of the grain-boundary-rich connected region.

Investigation of coatings with in-situ TiX reinforcements fabricated by additive-subtractive manufacturing: Hardness, microstructure and machinability

Wear resistance is essential for the long lifespan of critical components such as turbine blades in aircraft engines. Coatings reinforced by hard particles provide a highly effective means to enhance the anti-friction characteristics of these vital parts. Additive manufacturing presents a promising alternative for the fabrication of particle reinforced coatings. Nonetheless, it remains crucial to employ finishing processes on additively-manufactured parts to meet stringent quality and dimensional precision requirements before assembly. In this study, new findings on the additive-subtractive manufacturing of the coatings reinforced by in-situ TiC, TiB and TiB2 was comprehensively analyzed. The coupled influence of the fraction of WC and the laser power on the quality and properties of the coatings were explored, and the machinability of the coatings were evaluated via the finish milling. It was found that the fraction of WC was dominant on the morphology, phases, hardness, and microstructure of the laser-clad coatings; the difference in the properties of the coatings caused variance on the cutting force, surface quality and work hardening of the machined surface.

A Study of the Microstructure and Mechanical and Electrochemical Properties of CoCrFeNi High-Entropy Alloys Additive-Manufactured Using Laser Metal Deposition

This work demonstrates the successful additive manufacturing of an in situ-alloyed CoCrFeNi HEA with a single phase (FCC) structure via the laser metal deposition (LMD) technique. In this work, bulk specimens of the CoCrFeNi high entropy alloy (HEA) of size 15 mm × 15 mm × 45 mm were additive-manufactured (AMed). An H320-type additive-subtractive manufacturing all-in-one system with a 2 kW fiber laser with a coaxial nozzle head integrated in a five-axis CNC machine was used. The effect of varying laser powers (1000 W, 1300 W, and 1600 W) on the microstructure and mechanical and electrochemical properties of the AMed HEA specimens was investigated. The AMed specimens were analyzed for their microstructure, elemental distributions, microhardness, and mechanical and electrochemical properties. An increase in the laser power led to a non-uniform cooling rate and non-steady solidification rates of the molten area during the AM process. As a result, the crystal constant decreased, and the microhardness fluctuated within a narrow range across the specimen. Among the three laser powers, the AMed CoCrFeNi HEA at 1300 W had the optimal mechanical properties and the best electrochemical behavior in 3.5 wt.% NaCl solution.

Comparative environmental impact assessment of additive-subtractive manufacturing processes for Inconel 625: A life cycle analysis

This paper presents a life cycle assessment (LCA) approach to compare the environmental impacts of additive-subtractive manufacturing processes for Inconel 625. The LCA follows a cradle-to-gate methodology and employs the Eco-chain Mobius Software, in accordance with ISO 14044 standards. The chosen LCA model enables industries to develop sustainable production techniques by evaluating 18 environmental variables' potential effects on human health, ecosystems, and resource availability. The LCA adopts the midpoint(H) approach from ReCiPe 2016 to comprehensively assess the environmental impacts. In the first case study, a plate is created using the Wire Arc Additive Manufacturing (WAAM) method, followed by post-processing through drilling in both wet and dry environments. The dry condition results in a remarkable 24.23% reduction in environmental impact when the LCA is applied to the entire process, making it the most sustainable choice. In the second case study, a hollow cylinder is manufactured using the WAAM technique, and post-processing is conducted using turning processes under cryogenic, dry, and electrostatic minimum quantity lubrication (EMQL) conditions. The dry environment yields a 16.4% lower impact on the environment, establishing it as the most sustainable choice. Overall, the results from both case studies demonstrate that utilizing WAAM technology in a dry environment leads to the most sustainable manufacturing procedure for Inconel 625. This comparative analysis provides valuable insights to support the development of environmentally friendly production techniques in the manufacturing industry.

4D Additive-Subtractive Manufacturing of Shape Memory Ceramics.

The development of high-temperature structural materials, such as ceramics, is limited by their extremely high melting points and the difficulty in building complicated architectures. Four-dimensional (4D) printing helps enhance the geometrical flexibility of ceramics. However, ceramic 4D printing systems are limited by the separate processes for shape and material transformations, low accuracy of morphing systems, low resolution of ceramic structures, and their time-intensive nature. Here, a paradigm for a one-step shape/material transformation, high-2D/3D/4D-precision, high-efficiency, and scalable 4D additive-subtractive manufacturing of shape memory ceramics is developed. Original/reverse and global/local multimode shape memory capabilities are achieved using macroscale SiOC-based ceramic materials. The uniformly deposited Al2 O3 -rich layer on the printed SiOC-based ceramic lattice structures results in an unusually high flame ablation performance of the complex-shaped ceramics. The proposed framework is expected to broaden the applications of high-temperature structural materials in the aerospace, electronics, biomedical, and art fields.

Multi-indicator evaluation and material selection of hybrid additive-subtractive manufacturing to repair automobile panel dies and molds

Multi-indicator evaluation and material selection of hybrid additive-subtractive manufacturing to repair automobile panel dies and molds

Friction property and milling machinability of Ni60 cladding layer in hybrid additive-subtractive manufacturing

Hybrid additive-subtractive manufacturing (HASM) is an advanced technology for parts repairing. However, the complex process and difficult to machine characteristics of cladding formed materials limit its applications. The microstructure, friction property, and milling machinability of the single-pass laser cladding layer (LCL) are investigated using laser cladding and milling experiments. The results show that Ni60-based LCL has a good forming quality on the Cr12MoV die steel. The average micro-hardness of LCL is 1.38 times that of substrate and the wear mechanism is mainly the mixture of oxidation wear and abrasive wear. Furthermore, the results of multi-zone milling experiment show that the saw-tooth chips have been appeared at the milling speed of 75.4 m/min. On the other hand, the results of single-zone milling experiment show that the middle zone has the lowest average value of and fluctuate of milling force, and has the best machined surface quality. Moreover, the micro-hardness after milling in the middle zone can reach to 57 HRC, and its wear resistance is 20.93 % better than that of substrate. Therefore, the middle zone of LCL has the best machinability, and the subsequent processing is eager to be carried out in this zone. A guiding concept of cladding parameters selection is proposed based on the machinability and machining position. It is of great significant to improve the machining efficiency and machining quality of HASM process.

A framework for hybrid manufacturing cost minimization and preform design

This paper describes preform design optimization in hybrid additive-subtractive manufacturing. In hybrid manufacturing, the question of what form and what geometry the additive preform should take has largely been a matter of intuition and experience, or trial and error. The choice of a more optimal preform depends on the target parameters, such as stiffness, cost, or lead time. We demonstrate a framework for preform optimization using static stiffness, and then the combined cost of additive and subtractive manufacturing, while respecting stable cutting conditions for the tool-part combination. The procedure is illustrated by comparing three preform geometries for a thin wall.

Effects of Different Process Strategies on Surface Quality and Mechanical Properties of 316L Stainless Steel Fabricated via Hybrid Additive-Subtractive Manufacturing

Effects of Different Process Strategies on Surface Quality and Mechanical Properties of 316L Stainless Steel Fabricated via Hybrid Additive-Subtractive Manufacturing

Effect of Porosity on Tool Wear During Micromilling of Additively Manufactured Titanium Alloy

Abstract Porosity is a major quality issue in additively manufactured (AM) materials due to improper selection of raw material or process parameters. While porosity is kept to a minimum for structural applications, parts with intentional (engineered) porosity find applications in prosthetics, sound dampeners, mufflers, catalytic converters, electrodes, heat exchangers, filters, etc. During postprocessing of additive manufactured components using secondary machining to obtain required dimensional tolerance and/or surface quality, part porosity could lead to fluctuating cutting forces and reduced tool life. The machinability of the porous AM material is poor compared to the homogenous wrought material due to the intermittent cutting and anisotropy of AM materials. This paper investigates the tool wear progression and underlying mechanisms in relation to the porosity of AM material during their machining. Micromilling experiments are carried out on AM Ti6Al4V alloy with different porosity levels. Insights into tool-workpiece interaction during micromachining are obtained in cases where pore sizes could be comparable to the cutting tool diameter. Findings of this research could be helpful in developing efficient hybrid additive-subtractive manufacturing technologies with improved tool life and reduced costs.

Energy consumption modeling of additive-subtractive hybrid manufacturing based on cladding head moving state and deposition efficiency

Energy consumption modeling of additive-subtractive hybrid manufacturing based on cladding head moving state and deposition efficiency

Feature extraction and process planning of integrated hybrid additive-subtractive system for remanufacturing.

Discussion regarding hybrid manufacturing has dominated research in recent years. By synergistically integrating additive and subtractive manufacturing within a single workstation, the relative benefits of each manufacturing strategy are leveraged. The ability to add, remove feature flexibly enables remanufacturing end-of-life components into a "new" part with new features and functionalities. However, in the remanufacturing context, the process planning for hybrid additive-subtractive manufacturing is still an unsolved research topic. In general, a hybrid remanufacturing process is signified by an alternating sequence of additive and subtractive operations that alternatively add and remove materials on a used part, which results in a non-unique process planning. For determining an optimal sequence for hybrid remanufacturing, a quantitative evolution mechanism is demanded. Moreover, the constraints in process planning are required to be considered. For example, the collision avoidance between the workpiece and the material-dispensing nozzle is one of the most critical limitations that affect the alternating sequence. To fill the gap, automated feature extraction and cost-driven process planning method for hybrid remanufacturing are proposed in this paper. The feature extraction, developed under the level set framework, can extract optimal and collision-free additive-subtractive features. Then, the hybrid process planning task is formulated into an integer programming model with cost estimations. A case study is conducted, and the results confirm the correctness and effectiveness of the proposed method.

Towards rapid, in situ characterization for materials-on-demand manufacturing

Recent hybrid additive-subtractive manufacturing platforms can usher a materials-on-demand manufacturing paradigm where the materials, along with geometry and surface morphology, are designed to meet the functionality. While in situ measurement systems have advanced to monitor geometric and morphological variations, microstructure and phase characterization methods remain slow, impeding this vision. Towards addressing this issue, we present an approach to characterize the material concurrently during fabrication by associating in situ sensor measurements with the microstructures. Analysis of sensor data from machining of 316L steel suggests that the microstructural variations under different process parameters can be predicted in real time with 93% accuracy.

Topology optimization of continuum structures under hybrid additive-subtractive manufacturing constraints

Additive manufacturing (AM) makes it possible to fabricate complicated parts that are otherwise difficult to manufacture by subtractive machining. However, such parts often require temporary support material to prevent the component from collapsing or warping during fabrication. The support material results in increased material consumption, manufacturing time, and clean-up costs. The surface precision and dimensional accuracy of the workpieces from AM are far from the engineering requirement due to layer upon layer manufacturing. Subtractive machining (SM), by contrast, can fabricate parts to satisfy the requirements of surface precision and dimensional accuracy. Nevertheless, the components need to be relatively uncomplicated for subtractive manufacturing. Thus, hybrid additive-subtractive manufacturing (HASM) is gaining increasing attention in order to take advantages of both processes. There is little research on the topological design methodology for this hybrid manufacturing technology. To address this issue, a method based on geometry approach for topology optimization of continuum structure is proposed in this paper. Both additive manufacturing and subtractive machining constraints are simultaneously considered in each topology optimization iteration. The topology optimization is performed by the bi-directional evolutionary structural optimization (BESO) method. The effectiveness of the proposed method is demonstrated by several 3D compliance minimization problems.