Subtractive Manufacturing Research Articles

Measuring thermomechanical response of large-format printed polymer composite structures via digital image correlation

Large-format additive manufacturing (LFAM) is a branch of additive manufacturing (AM) research with the ability to create large structures typically measuring several meters in scale. LFAM is advantageous for tooling applications, not only because it offers the ability to create complex geometries not easily made using subtractive manufacturing processes, but the cost savings of pelletized feedstock used by these systems result in larger parts printed at faster speeds than traditional AM systems. Fiber reinforced polymer (FRP) is a commonly used feedstock material in LFAM structures because it reduces the distortion experienced during printing. However, FRP introduces highly anisotropic thermomechanical properties and contributes to a nonhomogeneous microstructure that can result in critical distortion of dimensions during tooling. Measuring the global thermomechanical response of LFAM structures requires a more representative method that accounts for not only anisotropic properties but also the nonhomogeneous nature of the final part. This is where traditional techniques to measure thermomechanical response, such as thermomechanical analysis (TMA), fall short as they assume homogeneity. This study evaluated the coefficient of thermal expansion (CTE) of LFAM structures as measured by TMA as compared to a novel digital image correlation oven (DIC Oven) system. The LFAM structures were made from 20 % by weight carbon fiber reinforced acrylonitrile butadiene styrene (CF-ABS). TMA measurements showed significant variations in CTE across a single LFAM bead, confirming the need for a global technique that captures overall thermomechanical response. The CTE values measured using the DIC Oven compared well to average TMA values obtained from localized measurements across the sample. The DIC Oven was also used to quantify the effects of different layer orientations on thermomechanical properties, which cannot be easily captured using TMA. A predictive model was also developed by using localized TMA values across an LFAM bead to predict the overall thermomechanical response of an LFAM structure.

The Second Laser Revolution in Chemistry: Emerging Laser Technologies for Precise Fabrication of Multifunctional Nanomaterials and Nanostructures

AbstractThe use of photons to directly or indirectly drive chemical reactions has revolutionized the field of nanomaterial synthesis resulting in appearance of new sustainable laser chemistry methods for manufacturing of micro‐ and nanostructures. The incident laser radiation triggers a complex interplay between the chemical and physical processes at the interface between the solid surface and the liquid or gas environment. In such a multi‐parameter system, the precise control over the resulting nanostructures is not possible without deep understanding of both environment‐affected chemical and physical processes. The present review intends to provide detailed systematization of these processes surveying both well‐established and emerging laser technologies for production of advanced nanostructures and nanomaterials. Both gases and liquids are considered as potential reacting environments affecting the fabrication process, while subtractive and additive manufacturing methods are analyzed. Finally, the prospects and emerging applications of such technologies are discussed.

Surface integrity improvement of the ground surface of Inconel 718 fabricated by forging and additive manufacturing using a robotic rotational burnishing method

Given that the surface acts as the primary interface with the surrounding environment, the surface integrity of a component significantly influences its operational effectiveness. In the aerospace industry, materials like Inconel 718 are often utilized for their high-temperature strength despite their poor thermal conductivity and machinability, resulting in inferior surface integrity during grinding procedures. This research proposes an innovative robotic rotational burnishing method that leverages self-generated heat to aid in the post-grinding burnishing process, eliminating the need for an external heat source. The surface integrity achieved through this method undergoes a comprehensive evaluation, encompassing surface topological features, microstructure, and mechanical properties, and is compared with surfaces treated by grinding and slide burnishing. The findings demonstrate that during the rotational burnishing process, the friction between the high-speed rotating burnishing tip and the workpiece surface induces circumferential flow of the surface material, thereby enhancing surface anisotropy. Additionally, this process generates significant heat, further encouraging plastic deformation of the material surface under high burnishing forces. As a result, the surface acquires a compressive residual stress exceeding 1000 MPa and develops a microhardness-strengthened layer with a thickness exceeding 500 μm. Both forging and additive manufacturing techniques for preparing Inconel 718 raw materials yield consistent outcomes. This study not only achieves a fusion of additive, subtractive, and equivalent manufacturing but also validates the applicability of the proposed robotic rotational burnishing method in enhancing surface integrity across materials manufactured by various techniques.

Screen-Printable Iontronic Pressure Sensor with Thermal Expansion Microspheres for Pulse Monitoring.

Constructing microstructures to improve the sensitivity of flexible pressure sensors is an effective approach. However, the preparation of microstructures usually involves inverted molds or subtractive manufacturing methods, which are difficult in large-scale (e.g., in screen printing) preparation. To solve this problem, we introduced thermally expandable microspheres for screen printing to fabricate flexible sensors. Thermally expandable microspheres can be constructed into microstructures by simple heating after printing, which simplifies the microstructure fabrication step. In addition, the added microspheres can also be used as ionic liquid reservoir materials to further increase the capacitance change and improve the sensitivity. The prepared sensors exhibited superior performance, including ultrahigh sensitivity (Smax = 49999.5 kPa-1) and wide detection range (0-350 kPa). Even after 30,000 cycles at a high pressure of 300 kPa and a low pressure of 30 kPa, the sensor showed minimal signal degradation, demonstrating long-term cycling stability. In order to verify the practical potential of the sensors, we performed human radial artery beat detection experiments using these sensors. The variations in the intensity of the 3D radial artery pulse wave can be observed very clearly, which is important for human health monitoring. The above demonstrates that our strategy can provide an effective approach for the large-scale preparation of high-performance flexible pressure sensors.

High‐Precision Materials Printer for Fast Prototyping of Electronic Devices Based on 2D Materials

AbstractThere is an increasing interest in printed electronics driven principally by flexible and wearable applications. The interest stems from the ability to fabricate electronic devices, such as Field Effect Transistors (FET), more efficiently in terms of materials use and cost‐effectively than traditional lithographic techniques. Challenges persist in achieving high resolution and accuracy in defining device geometry. In the study, a high‐resolution materials printer able to achieve resolutions in the micron range, surpassing the capabilities of commercially available printers is successfully designed and fabricated. The printer incorporates an all‐in‐one printing system, comprising Inkjet and a Dip Pen Nanolithography (DPN) technique, enabling both additive and subtractive manufacturing at the microscale. The experiments demonstrate the successful fabrication of FETs based on 2D materials (2DMs), with micrometric channel lengths exhibiting a high degree of controllability and repeatability, even when contacting limited channel regions as micrometer‐sized molybdenum disulfide (MoS2) flakes. Electrical characterizations of the fabricated devices underscore the significant technological advancements achieved by the prototypes.

Advanced constraint programming formulations for additive manufacturing machine scheduling problems

In comparison with traditional subtractive manufacturing techniques, additive manufacturing (AM) enables fabricating complex parts through a layer-by-layer process. AM makes it possible to produce one-piece and lightweight functional products, which are traditionally made from several parts. This paper introduces constraint programming (CP) models to minimise makespan in single, parallel identical and parallel unrelated AM machine scheduling environments for selective laser melting. Alternative CP formulations are explored to improve efficiency. The proposed CP model significantly benefits from the introduction of interval variables to replace binary assignment variables, and pre-definitions to narrow the search space, resulting in increased search performance. A computational study has been conducted to compare the performance of our proposed CP model with both a mixed-integer programming and a genetic algorithm from existing literature, evaluating improvements made to its search capability. Computational results indicate that the proposed CP model can obtain high-quality solutions in a timely manner even for several large-size instances.

Comparison of Additive and Subtractive Manufacturing for Fixed Dental Restorations: A Systematic Review and Meta-Analysis

Comparison of Additive and Subtractive Manufacturing for Fixed Dental Restorations: A Systematic Review and Meta-Analysis

Multi-layer cutting path planning for composite enclosed cavity in additive and subtractive hybrid manufacturing

Additive and subtractive hybrid manufacturing (ASHM) refers to the hybrid manufacturing process where in-situ subtractive machining (SM) is introduced during additive manufacturing (AM). Its process characteristics dictate the necessity of planning multi-layer cutting paths in ASHM. Currently, the slice-based planning method cannot plan multi-axis cutting paths, and the machining accuracy is difficult to directly control. Meanwhile, the manual layering planning method is inefficient when dealing with complex models. Consequently, this paper presents an innovative automatic planning method for multi-layer, multi-axis, interference-free cutting paths with controllable precision in ASHM of composite enclosed cavity parts. To enhance the ASHM efficiency, criteria for the recognition of hybrid machining features (HMFs) have been defined to identify HMFs within the model. The identification of interference planes during cavity conversion has been achieved, and these interference planes are then utilized as the conversion planes for the ASHM process. Furthermore, a boundary-guided method is employed to automatically plan the overall cutting path for HMFs. According to the G-code standard, the overall cutting paths are then output to the corresponding cutting path file within the height interval of the conversion planes. Through practical machining, it has been demonstrated that the proposed method can significantly enhance the efficiency and automation of the data preparation process in ASHM, while also improving the surface quality and dimensional accuracy of the AM part.

Single-Cell Synchro-Subtractive-Additive Nanoscale Surgery with Femtosecond Lasers.

Herein, an in situ "synchro-subtractive-additive" technique of femtosecond laser single-cell surgery (FLSS) is presented to address the inadequacies of existing surgical methods for single-cell manipulation. This process is enabled by synchronized nanoscale three-dimensional (3D) subtractive and additive manufacturing with ultrahigh precision on various parts of the cells, in that the precise removal and modification of a single-cell structure are realized by nonthermal ablation, with synchronously ultrafast solidification of the specially designed hydrogel by two photopolymerizations. FLSS is a minimally invasive technique with a post-operative survival rate of 70% and stable proliferation. It opens avenues for bottom-up synthetic biology, offering new methods for artificially synthesizing organelle-like 3D structures and modifying the physiological activities of cells.

Bridging Nature and Technology: A Perspective on Role of Machine Learning in Bioinspired Ceramics

Nature has long inspired scientific and engineering advancements, particularly in the development of bioinspired ceramics. However, replicating nature's intricate structures through subtractive manufacturing techniques remains a significant challenge due to the limitations of precise and controlled material removal while maintaining structural integrity and complexity. This perspective article explores the transformative potential of machine learning (ML), particularly advancements in generative artificial intelligence (generative adversarial networks, transformer models) and multimodal learning, in accelerating the discovery of high‐performance bioinspired ceramics. ML offers an avenue to optimize material behavior beyond the constraints of traditional experimental methods. Recent advancements have shown ML's effectiveness in predicting mechanical properties and refining material designs, often surpassing conventional approaches. ML excels at identifying complex relationships even with incomplete data during training. The integration of cutting‐edge experimental data, cross‐scale simulations, and ML facilitates high‐fidelity multiscale modeling for predicting intricate phenomena like crack propagation paths in bioinspired ceramic structures. This article emphasizes the significant potential of ML to propel the field of bioinspired ceramics forward, paving the way for the discovery of ceramics with superior and tailored properties.

The effect of thermomechanical aging on the fracture resistance of additively and subtractively manufactured polyetheretherketone abutments

ObjectivesTo evaluate the fracture resistance (FR) of polyetheretherketone (PEEK) abutments produced by additive and subtractive methods compared to milled zirconia abutments. MethodsCustom abutments were designed on Ti-base abutments and produced from three different materials, namely additively manufactured PEEK (PEEK-AM), subtractively manufactured PEEK (PEEK-SM), and zirconia (N = 60). PEEK-AM abutments were printed using PEEK filaments (VESTAKEEP®i4 3DF-T, Evonik Industries AG) on a M150 Medical 3D Printer (ORION AM) by fused filament fabrication (FFF). All surface treatments were carried out according to the manufacturer's instructions. All abutments were cemented on Ti-bases with hybrid abutment cement and then restored with milled zirconia crowns. Each subgroup was divided into non-aged and aged subgroups (n = 10). The aged groups were subjected to thermomechanical aging (49 N, 5–55 °C, 1.2 million cycles). FR tests were performed by using an universal testing machine. Data were statistically analyzed with one-way and two-way ANOVA and t-test. ResultsThe survival rate of the specimens after aging was determined as 100%. It was found that both the material and aging had a significant effect on the FR (p<.001). There was a statistical difference among the fracture values of the groups (p<.001). In both the aged and non-aged groups, PEEK-AM showed the statistically lowest FR, while the highest FR was seen in the zirconia group, which was significantly higher than the PEEK-SM (p<.001). ConclusionHybrid abutments were successfully manufactured, and extrusion-based processed PEEK seems to be a good alternative to subtractive processed PEEK. However, since subtractive manufacturing still appears to be superior, further developments in additive manufacturing are needed to further improve the quality of 3D-printed PEEK parts, especially in terms of accuracy and bonding between adjacent layers. Clinical SignificanceAdditively manufactured PEEK abutments have the potential to be an alternative for implant-supported restorations in the posterior region.

Healthy and diabetic primary human osteoblasts exhibit varying phenotypic profiles in high and low glucose environments on 3D-printed titanium surfaces.

The revolution of orthopedic implant manufacturing is being driven by 3D printing of titanium implants for large bony defects such as those caused by diabetic Charcot arthropathy. Unlike traditional subtractive manufacturing of orthopedic implants, 3D printing fuses titanium powder layer-by-layer, creating a unique surface roughness that could potentially enhance osseointegration. However, the metabolic impairments caused by diabetes, including negative alterations of bone metabolism, can lead to nonunion and decreased osseointegration with traditionally manufactured orthopedic implants. This study aimed to characterize the response of both healthy and diabetic primary human osteoblasts cultured on a medical-grade 3D-printed titanium surface under high and low glucose conditions. Bone samples were obtained from six patients, three with Type 2 Diabetes Mellitus and three without. Primary osteoblasts were isolated and cultured on 3D-printed titanium discs in high (4.5 g/L D-glucose) and low glucose (1 g/L D-Glucose) media. Cellular morphology, matrix deposition, and mineralization were assessed using scanning electron microscopy and alizarin red staining. Alkaline phosphatase activity and L-lactate concentration was measured in vitro to assess functional osteoblastic activity and cellular metabolism. Osteogenic gene expression of BGLAP, COL1A1, and BMP7 was analyzed using reverse-transcription quantitative polymerase chain reaction. Diabetic osteoblasts were nonresponsive to variations in glucose levels compared to their healthy counterparts. Alkaline phosphatase activity, L-lactate production, mineral deposition, and osteogenic gene expression remained unchanged in diabetic osteoblasts under both glucose conditions. In contrast, healthy osteoblasts exhibited enhanced functional responsiveness in a high glucose environment and showed a significant increase in osteogenic gene expression of BGLAP, COL1A1, and BMP7 (p<.05). Our findings suggest that diabetic osteoblasts exhibit impaired responsiveness to variations in glucose concentrations, emphasizing potential osteoblast dysfunction in diabetes. This could have implications for post-surgery glucose management strategies in patients with diabetes. Despite the potential benefits of 3D printing for orthopedic implants, particularly for diabetic Charcot collapse, our results call for further research to optimize these interventions for improved patient outcomes.

From macro to micro: Bioinspired designs for tougher ceramics

Ceramic materials, while strong, often lack flexibility and energy absorption. Inspired by tough natural structures like nacre, toughening strategies have shown significant potential in ceramic materials. This study investigates the static and cyclic flexural properties (i.e., energy absorption, stiffness, and strength) of the bioinspired ceramic-polymer composites, particularly concerning the influence of macro and micro patterns. Using a subtractive manufacturing platform enabled by ultra-short pulsed picosecond lasers, we engrave a range of macro and micro patterns onto alumina tiles, mimicking natural armor designs. The composites are then fabricated by stacking laser-engraved tiles with an interlayer of Surlyn®, a commercial monomer. The results demonstrate that the static/cyclic performance and toughening mechanisms are closely linked to the lasered bioinspired surface patterns and stacking sequence. Specific macro architectures and stacking sequences led to significantly increased energy absorption (up to 85%) through mechanisms like crack deflection and plastic deformation of the soft phase. Micro patterns, on the other hand, improved the ceramic's strength (up to 140%) by influencing how the materials interact at the interface. This research not only advances our understanding of bioinspired armor but also paves the way for a new generation of ceramic composites with superior properties, targeting applications in defense (aerospace and vehicle armor) and personal protective equipment (PPE).

Sandwich structures with TPMS core and printed circuit board faces

Sandwich structures are widely used in the aerospace industries due to their mechanical properties that give them high energy absorption, low density, and high mechanical strength. These structures are composed of two faces interspersed by a core that can have various geometric configurations. One of the most widely used geometric cells are honeycomb structures, highly used in structural applications since the early 20th century. However, new geometric core configurations, as well as alternative materials and manufacturing processes, are being studied for space applications. Triply Periodic Minimal Surfaces (TPMS) are lattice structures composed of periodic surface structures in three independent directions. Among the available models, the most notable TPMS structures are Schwartz-type, Diamond-type, and Gyroid-type. Since the structures are too complex to be manufactured by subtractive manufacturing, additive manufacturing is excellent, being able to produce complex structures much faster and easier. One of the most common types of 3D printing is Fused Deposition Modeling (FDM), which is based on the fusion and deposition of various materials, such as thermoplastic materials. To save space and improve the mechanical strength of Cubesats, sandwich structures are being produced using printed circuit boards (PCB) of electrical and electronic components as outer faces. These faces are called laminates and are made of thermosetting materials such as fiberglass and epoxy resin, composites, or ceramic materials. The objective of this paper is to produce sandwich panels, with a core based on the TPMS architecture. They will be printed in thermoplastic material with laminated faces used in printed circuit boards. A numerical analysis using the finite element method was performed and its testing according to ASTM C393, furthermore, this paper aims to realize an optimized TPMS core with mass distribution based on the stress profile and compare them.

Polyetherimide in 3D printing: Pioneering non-metallic solutions for personalized orthopedic and traumatology hip prosthetics

Currently, Total Hip Replacement (THR) hip prosthetics are typically made from metallic materials using subtractive manufacturing, and they are not personalized. These materials, with higher densities than trabecular bone, can cause microfractures due to fatigue cycles. This study aims to demonstrate the feasibility of using Polyetherimide (PEI) as a rigid thermoplastic in additive manufacturing, offering a viable alternative for patient-specific prostheses in humans or pets. The starting point was a commercial prosthesis, a similar replica was 3D modelled, and test specimens were printed using ULTEM 1010 material. The PEI prosthesis meets outlined standards and offers an alternative for young, lightweight patients, and various pets. It does so by adapting to specific the patient's anatomical needs. Fatigue life was found to be the limiting factor, as the 392 N applied prosthesis, exceeded the million cycles limitation set for this study, prompting us to focus on the prosthesis' use on children, or small pets.

Fabrication of a Low-Cost Fused Filament Fabrication-based 3D Printer and Investigation of the Effect of Process Parameters on Mechanical Properties of 3D-Printed Samples

Additive Manufacturing (AM) techniques add material layer-by-layer to fabricate parts or products, compared to subtractive manufacturing processes, where the material is removed to obtain the final product. The most common method among AM techniques is fused filament fabrication (FFF), which uses filament material to print objects into end products. The present study's aims include designing and fabricating a custom FFF-based 3D printer and investigating the effects of three process parameters on the tensile properties of the 3D-printed samples. Initially, the 3D printer was successfully fabricated. The locally fabricated 3D printer uses Marlin Firmware 2.0 as programming code to control different functionalities of the printing processes. After fabrication and calibration, the printer 3D-printed a few samples successfully. Moreover, a design of experiments plan was formulated to print tensile specimens based on the levels of the process parameters. Tensile testing was performed, and the analysis of variance (ANOVA) confirmed that the process parameters significantly affected the tensile strength. The effects of the process parameters were then analyzed, along with the defect formation and microstructure analysis. Finally, optimum parameters for printing PLA parts with better tensile properties were figured out for the designed 3D printer.

Additively manufactured microstrip patch antennas in flat, curved, and embedded configurations

Microstrip patch antennas (MPAs) are compact and easy-to-fabricate antennas, widely used in long-distance communications. MPAs are commonly fabricated using subtractive methods such as photolithographic etching of metals previously deposited using sputtering or evaporation. Despite being an established technique, subtractive manufacturing requires various process steps and generates material waste. Additive manufacturing (AM) techniques instead allow optimal use of material, besides enabling rapid prototyping. AM methods are thus especially interesting for the fabrication of electronic components such as MPAs. AM methods include both 2D and 3D techniques, which can also be combined to embed components within 3D-printed enclosures, protecting them from hazards and/or developing haptic interfaces. In this work, we exploit the combination of 2D and 3D printing AM techniques to realize three MPA configurations: flat, curved (at 45∘), and embedded. First, the MPAs were designed and simulated at 2.3 GHz with a −16.25 dB S 11 value. Then, the MPA dielectric substrate was 3D-printed using polylactic acid via fused deposition modeling, while the antenna material (conductive silver ink) was deposited using three different AM methods: screen printing, water transfer, and syringe-based injection. The fabricated MPAs were fully operational between 2.2–2.4 GHz, with the flat MPA having a higher S 11 peak value compared to the curved and embedded MPAs. Development of such AM MPAs in various configurations demonstrated in this work can enable rapid development of long-range antennas for novel applications in e.g. aerospace and Internet of Things sectors.

Bridging additive and subtractive manufacturing

AbstractAdditive manufacturing with laser powder‐bed fusion (PBF‐LB/M) can generate complex metal parts with a high degree of design freedom, which are already being used in various industries. However, the PBF‐LB/M process faces some limitations in achievable surface quality and feature size. To address these challenges, we have developed a novel hybrid manufacturing approach that combines additive manufacturing via PBF‐LB/M with subtractive manufacturing via ultrafast laser machining. By alternating between additive and subtractive processes, it is possible to not only mitigate the limitations of each process but also to introduce new functionality. This synergistic combination enables the creation of parts with superior surface finishes and deep and narrow internal features that are not possible with a single method alone.

Beam shaping to tackle laser powder bed fusion challenges

AbstractAdditive manufacturing (AM), a term synonymous with the future of fabrication, has revolutionized industries by offering unparalleled flexibility in design and production. At the heart of this transformative technology is laser‐based powder bed fusion of metals (PBF‐LB/M), the process with the highest geometrical resolution having the largest market share (86 %, Wohlers) amongst all AM processes. By selectively melting and fusing powder material layer by layer with a laser, PBF‐LB/M enables the creation of complex and high‐strength components, previously unthinkable with traditional subtractive manufacturing methods.

Extending the Digital Twin Ecosystem: A real-time Digital Twin of a LinuxCNC-controlled subtractive manufacturing machine

This research paper describes the design and implementation of a real-time data-driven Digital Twin Ecosystem (DTE) for a LinuxCNC-controlled subtractive manufacturing computer numerical control (CNC) machine. The DTE architecture integrates real-time data acquisition, processing, and synchronization with the physical CNC machine. Our architecture adopts and extends the methodology presented in previous work and utilizes two components, namely the data Acquisition, Processing, and Distribution Component (APDC), and the Virtual Representation Component (VRC), which is developed using the Unity real-time development platform. The DTE accurately models the CNC machine’s behavior under various operating conditions. The DTE is verified and validated through testing and experimentation, particularly focusing on response time, sequencing accuracy, and seamless integration. The DTE offers two modes of operation: the online mode allows for real-time process replication, ideal for process monitoring and remote management, while the offline mode supports asynchronous G-code simulation, enabling what-if analysis and exploration of process variables. In this work, we utilize the offline mode for predictive collision detection. Using the DTE, stakeholders could make informed decisions, optimize machining processes, and ensure cost-effective operations. This research contributes to the advancement of Digital Twin technology, particularly in CNC machining, fostering innovation in the manufacturing sector and promoting the development of practical, efficient, and reliable cyber–physical industrial systems, enhancing operational capabilities and productivity.