Advanced permanent magnet generator topologies using multimaterial shape optimization and 3D printing

Multimaterial (MM) 3D printing shows great potential for application in metamaterials, flexible electronics, biomedical devices and robots, since it can seamlessly integrate distinctive materials into one printed structure. Among numerous MM 3D printing technologies, digital light processing (DLP) MM 3D printing is compatible with a wide range of materials from hydrogels to ceramics, and can print MM 3D structures with high resolution, high complexity and fast speed. This paper introduces the fundamental mechanisms of DLP 3D printing, and reviews the recent advances of DLP MM 3D printing technologies with emphasis on material switching methods and material contamination issues. It also summarizes a number of typical examples of DLP MM 3D printing systems developed in the past decade, and introduces their system structures, working principles, material switching methods, residual resin removal methods, printing steps, as well as the representative structures and applications. Finally, we provide perspectives on the directions of the further development of DLP MM 3D printing technology.

NdFeB (Neodymium magnets) rare earth permanent magnet is an advanced magnetic material characterized by a high energy product and excellent magnetic performance, which has broad application prospects. With the rapid development of 3D printing technology, its application in the research and fabrication of rare earth permanent magnet materials has become a research hotspot. This paper reviews the latest research developments of rare earth permanent magnet NdFeB materials in 3D printing. It introduces the basic properties and applications of rare earth permanent magnet materials and highlights the main challenge these materials faced, which is how do we improve their solid content. Additionally, the advantages and challenges of 3D printing technology in preparing rare earth permanent materials are analyzed in this paper. By comparing the variations in magnet properties of ferrite and rare permanent magnet materials with increasing temperature, it is found that the latter have relatively poor magnetic stability at high temperatures. Based on these points, the paper summarizes optimization methods of the current 3D printing process for rare earth permanent magnet materials. Finally, the paper discusses the development prospects of rare earth permanent magnet materials in 3D printing, as well as problems need to be solved and future research directions.

Multiscale and multimaterial three-dimensional (3D) printing is new frontier in additive manufacturing (AM). It has shown great potential to implement the simultaneous and full control for fabricated object including external geometry, internal architecture, functional surface, material composition and ratio as well as gradient distribution, feature size ranging from nano-, micro-, to macro-scale, embedded components and electrocircuit, etc. Furthermore, it has the ability to construct the heterogeneous and hierarchical structured object with tailored properties and multiple functionalities which cannot be achieved through the existing technologies. That paves the way and may result in great breakthrough in various applications, e.g., functional tissue and organ, functionally graded (FG) material/structure, wearable devices, soft robot, functionally embedded electronics, metamaterial, multifunctionality product, etc. However, very few of the established AM processes have now the capability to implement the multimaterial and multiscale 3D printing. This paper presented a single nozzle-based multiscale and multimaterial 3D printing process by integrating the electrohydrodynamic jet printing and the active mixing multimaterial nozzle. The proposed AM technology has the capability to create multifunctional heterogeneously structured objects with control of the macroscale external geometry and microscale internal structures as well as functional surface features, particularly, the potential to dynamically mix, grade, and vary the ratios of different materials. An active mixing nozzle, as a core functional component of the 3D printer, is systematically investigated by combining with the theoretical analysis, numerical simulation, and experimental verification. The study aims at exploring a feasible solution to implement the multiscale and multimaterial 3D printing at low cost.

There is growing interest in voxelated matter that is designed and fabricated voxel by voxel1-4. Currently, inkjet-based three-dimensional (3D) printing is the only widely adopted method that is capable of creating 3D voxelated materials with high precision1-4, but the physics of droplet formation requires the use of low-viscosity inks to ensure successful printing5. By contrast, direct ink writing, an extrusion-based 3D printing method, is capable of patterning a much broader range of materials6-13. However, it is difficult to generate multimaterial voxelated matter by extruding monolithic cylindrical filaments in a layer-by-layer manner. Here we report the design and fabrication of voxelated soft matter using multimaterial multinozzle 3D (MM3D) printing, in which the composition, function and structure of the materials are programmed at the voxel scale. Our MM3D printheads exploit the diode-like behaviour that arises when multiple viscoelastic materials converge at a junction to enable seamless, high-frequency switching between up to eight different materials to create voxels with a volume approaching that of the nozzle diameter cubed. As exemplars, we fabricate a Miura origami pattern14 and a millipede-like soft robot that locomotes by co-printing multiple epoxy and silicone elastomer inks of stiffness varying by several orders of magnitude. Our method substantially broadens the palette of voxelated materials that can be designed and manufactured in complex motifs.

For years the way of producing a flow profile for Inspection Chambers and Manholes could be divided into 3 methods: Injection moulding, Roto moulding and Hand assembling. For the standard orientations, for example straight through and cross, the IM profile integrated with a base is by far the best option. But for nonstandard configurations; different orientations, inlet heights and inlet sizes, the only option is to hand weld them together from injection moulded parts, pipes and plates. This is a time- consuming way of producing with high production cost and often aesthetic-wise of a challenging level. This is not necessary anymore after the introduction of 3D printing as a new production method for flow profiles in chambers and manholes. 3D printing is in many industries an accepted production method which can produce parts of high quality and high accuracy. The printing systems have faced a huge development in the last 10 years and prints are often close to perfection. The only disadvantage of these printing systems is the maximum size of the print. But since the introduction of 3D robot printing, products with a diameter of 1 meter can be printed without any problem. 3D robot printers were up to recently, used for prototypes, one- off products and art objects. Now a production area is created on which multiple products can be produced in a row without human interference. The most common materials used for 3D printing are ABS and PLA. These materials have good adhesion, almost no shrinkage and a good appearance. Unfortunately, these materials are not common in our industry. We need PP, PE or PVC. While our manholes and inspection chambers are from PP, we also need PP flow profiles. The advantage of using a 3D robot printer is that it uses granulates instead of filaments or special powder. This makes the material cost part almost equal to injection moulding. Another advantage is also that recycled material can be used. Own scrap can be used but also waste from other markets. The main reason that flows profiles are ideal for 3D printing is that nonstandard flow profiles are very labour-intensive. So, 3D printing really helps out here. Besides that, there is a lot of freedom in design. This helps to design in such a way, that the final profile is hydraulically optimal. This prevents the overflowing of manholes during heavy rain showers. Of course, these products should fulfil all requirements of the EN13598-2. Even though major development steps have been made in 3D printing during the last 5 years, 3D robot printing is still in the exploring phase and we find many hurdles on our way. This paper will show how our industry can use 3D printing and what are the pros and cons.

Low-cost 3D desktop printing, although still in its infancy, is rapidly maturing, with a wide range of applications. With its ease of production and affordability, it has led to development of a global maker culture, with the design and manufacture of artefacts by individuals as a collaborative & creative hobbyist practice. This has enabled mass customization of goods with the potential to disrupt conventional manufacturing, giving more people access to traditionally expensive products like prosthetics and medical devices [1], as is the case with e-NABLE, a global community providing open source prosthetics for people with upper limb deficiencies. However one of the major barriers to proliferation of 3D printing as a major manufacturing method is the limitation of compatible materials for use with the technology [2]. This places constraints on the design approach, as well as the complexity & functionality of artefacts that can be produced with 3D printing as compared to traditional manufacturing methods. As a result, devices like the e-NABLE Raptor Reloaded prosthetic hand, which is designed specifically to be produced via a single extruder FDM desktop 3D printer, have limited functionality as compared to conventional prosthetics, leading to low active use and prosthesis abandonment [3]. However, with the advent of multi-material desktop 3D printing, and increasing availability of a broader range of compatible materials (of varying characteristics) [2], there is scope for improving capabilities of low-cost prosthetics through the creation of more sophisticated multi-material functional integrated devices. This work documents the exploration of potential applications of multi-material 3D printing to improve production, capabilities and usability of low-cost open source prosthetics. Various material combinations were initially studied and functional enhancements for current 3D printed prosthetics were prototyped using key material combinations identified. Further, a user-centered design approach was utilized to develop a novel multi-material anthropomorphic prosthetic hand ‘ex_machina’ based on a modular platform architecture, to demonstrate the scope for reduced build complexity and improved dexterity & functional customization enabled by dual extrusion FDM desktop 3D printing. A full prototype was built & tested with a lead user, and results analyzed to determine scope for optimization.

Additive manufacturing (AM) via 3-D printing technologies have become a frontier in materials research, including its application in the development and recycling of permanent magnets1,2. The increasing criticality in availability of the rare earth minerals in magnets present a demanding challenge to the losses from conventional or subtractive manufacturing. AM allows for a minimal waste production and re-utilization of recovered rare earths in the magnet processing. In-situ alignment during 3D printing of magnetic materials has opened new horizons for manufacturing of complex permanent magnets3,4. The introduction of functionalized magnetic 3D printing (Fig. 1a) as an AM process yields several unique advantages including rapid prototyping of multi-directionally aligned magnetic systems, and reduced energy requirement due to the elimination of post-production alignment3.In this work, we have developed a mechanism to align magnetic materials using fused filament 3D printer with a novel magnetic field source architecture (Fig. 1b). The work addresses opportunities to integrate magnetic field into 3D printing process to enable printing, and alignment of anisotropic permanent magnets, without requiring further processing. The principle behind the analysis is rotation of magnetic particles in a molten matrix under low magnetic field. The alignment architecture was designed and optimized for weight and applied field.An in-depth finite element modeling and CAD was performed followed by prototyping of the magnetic field source (Fig. 1c-d). Several electromagnetic core models were developed using finite element modeling to obtain a field strength of > 1 T with a magnetic material in the nozzle. The electromagnetic simulations were coupled with thermal analysis to obtain realistic transient thermal profiles. Design modifications were incorporated to improve the thermal performance of the models without compromising the electromagnetic output. The results predict models that could be operated over prolonged durations (> 10 hours) at less than the rated temperature (80 oC) and at the rated current (5 A), while producing field strength of > 1 T. As a future prospective, the model would be implemented as a prototype to be incorporated with the 3D printer.Magnetization vs. field measurements of extruded and printed Sm-Co (15 vol.%) in PLA and Nd-Fe-B/Sm-Fe-N composite (65 vol.%) in Nylon-12, prepared with and without magnetic field, confirmed alignment of magnetic particles (Fig. 2a-b). Field vs. alignment and printer temperature vs. alignment analyses were performed to understand the effects of process variables on the degree of alignment of the samples.Finally, a multiphysics model was developed, that couples fluid dynamics and electromagnetic interactions, to predict the degree of alignment (DoA) of a polymer bonded magnet printed under applied field. The model predicts the flow of magnetic particles in a viscous fluid through a nozzle under applied magnetic field. A particle-fluid interactive flow simulation was performed to model the flow regime of molten bonded magnet. The interactions between the drag, inertial, and magnetophoretic forces were analyzed to predict the particle trajectory. A torque balance was performed between the drag torque, magnetic torque on particles from the applied field, and torque from particle-particle interactions. The analysis was used to predict the degree of rotation of magnetic particles during printing. The simulated DoA of 0.68 compares well with the experimentally obtained for 65 vol.% NdFeB+SmFeN in Nylon-12. For 15 vol.% Sm-Co in PLA, the simulated DoA of 0.86 also compared well with 0.83 obtained experimentally (Fig.2c-d). This process can be used for any permanent magnet composition or hybrid magnets and presents a benchmark for application of this technology in industrial and commercial applications.This work is supported by the Critical Materials Institute (CMI), an Energy Innovation Hub funded by the U.S. Department of Energy (DOE), Office of Energy Efficiency and Renewable Energy, Advanced Manufacturing Office. Ames Laboratory is operated for the U.S. Department of Energy by Iowa State University of Science and Technology under Contract No. DE-AC02-07CH11358. **

Direct-ink-writing 3D-printed bioelectronics

Permanent magnet synchronous motors (PMSMs) are a key part of the current hybrid electric vehicle (HEV) drive system, and the sophisticated performance such as small size, high power density, and high efficiency is required to the PMSMs in the HEV drive system. Therefore, rare earth permanent magnet is generally employed in the PMSMs in order to satisfy those demands. However, rare earth materials contained in the rare earth permanent magnet have several concerns caused by uneven distribution, because the rare earth materials such as neodymium and dysprosium depend on China for 90% or more of the world share. Accordingly, the rare earth materials have the undeniable possibility of sudden rise of price or reinforcement of export restriction. On the other hand, the HEVs tend to be promoted rapidly because of growing concern about environmental problems. Therefore, it is very important to develop rare-earth-free motors for the next generation HEV drive system. This paper proposes a ferrite permanent magnet axial gap motor without the rare earth materials for the HEVs. In addition, the proposed motor structure and the analytical results with the 3D-FEA are introduced.

Introduction: The non-renewable nature of rare-earth materials and their increasing demand have led to rising prices for rare-earth Permanent Magnet (PM) materials, thereby increasing the manufacturing costs of the corresponding motors. Reducing reliance on rare-earth materials while ensuring the operating performance of motors has attracted significant research attention, resulting in fewer rare-earth permanent magnet synchronous motors emerging in this context. This paper introduces a less rare-earth Permanent Magnet Synchronous Motor (PMSM) with a novel rotor permanent magnet structure, which has been designed, analyzed, and optimized. The primary feature of this motor is the stepped structure of the rotor, composed of neodymium iron boron, which enhances overall performance. Methods: The proposed motor is designed, simulated and analyzed by using the finite element analysis method using ANSYS Maxwell electromagnetic simulation software. Results: By improving the shape of the rotor neodymium-iron-boron permanent magnets, the motor offers the advantages of low cogging torque, low harmonic reverse Electromotive Force (EMF) at no load, and a more sinusoidal air-gap flux density waveform. This paper provides effective verification through simulation analysis. Discussion: The optimisation results of the motor are analysed in terms of rotor permanent magnet shape, main stage NdFeB angle, air gap length, NdFeB material, and number of motor coil turns. Conclusion: The proposed motor not only reduces the cogging torque and no-load back EMF harmonics, but it also makes the air gap flux density waveform closer to sinusoidal by optimizing the rotor structure while achieving the rated load torque requirement.

Introduction: Three-dimensional (3D) printing has transformed dentistry by enhancing precision, efficiency, and reducing material waste in prosthesis manufacturing. The objective of this study is to evaluates (3D) printing effectiveness and operational parameters by assessing technology used, workflow efficiency, patient outcomes and complications in dental procedures, focusing on its clinical applicability and impact on patient care. Methods: A systematic literature review was done for articles from 2015 to 2024. A systematic search of multiple databases, including PubMed and Google Scholar, yielded 3785 studies, which were narrowed to 15 studies that focused on 3D printing technology in multi-part dental prostheses. Results: The 3D-printed material was compared with conventional rapid prototyping material, and good strength characteristics of the prostheses were achieved. 3D-printed prostheses' long-term performance depends on constantly developing techniques and technologies. 3D-printed prosthesis accuracy was relatively high, but patient throughput, complexity, and limited precision needed to be more satisfactory. Literature reviews, randomized controlled trials, single-centre clinical trials, and in vitro and observational studies were also included in this study. Conclusions: Although limitations about material properties, production costs, and accuracy still exist, the prospects of 3D printing for clinical application in dental prosthetics are very encouraging. Enhanced digital workflows have positively impacted patient engagement, yet additional research is needed to improve such practices in the clinic for maximal patient satisfaction

3D printing has become a powerful technique in electrochemistry for fabricating electrodes, thanks to readily available conductive nanocomposite filaments, such as those based on carbon fillers (i.e., carbon nanotubes (CNTs) or carbon black (CB)) within an insulating polymeric matrix like polylactic acid (PLA). Inspired by inorganic heterostructures that enhance the functional characteristics of nanomaterials, we fabricated hetero-layered 3D printed devices based on carbon allotropes using a layer-by-layer assembly approach. The heterolayers were customised through the alternate integration of different carbon allotrope filaments via a multi-material 3D printing technique, allowing for a time-effective method to enhance electrochemical performance. As a first demonstration of applicability, CNT/PLA and CB/PLA filaments were utilised to construct ordered hetero-layered carbon-based electrodes. This contrasts with conventional methods where various carbon species are mixed in the same composite-based filament used for building electrochemical devices. Multi-material 3D-printed carbon electrodes exhibit improved electrochemical performance in energy conversion (e.g., hydrogen evolution reaction or HER) and sensing applications (e.g., ascorbic acid detection) compared to single-material electrodes. This work paves the way for manufacturing advanced 3D-printed heterolayered electrodes with enhanced electrochemical activity through multi-material 3D printing technology.

Flux switching generators with permanent magnets (PMs) on the stator is a good alternative to traditional synchronous generators for gearless wind turbines. This paper is dedicated to the comparison of the 3-phase rare-earth and ferrite PM flux switching generators considered in gearless wind generator application (332 rpm, 1784 W). The machines are designed and optimized using the Nelder–Mead algorithm coupled with 2D FEM model. The objective function is built taking into account the following objectives: the average efficiency of the generators over the wind turbine profile, the required power of the AC–DC converter, the quantity of the magnets and the torque ripple. It is found that the ferrite PM flux switching generator can be an attractive alternative to the rare-earth one. The averaged efficiency of the generator with ferrite PM is higher by 4.1% than that of the rare-earth one. The active power of the ferrite generator is also higher in a wide range of powers. Although the mass of the ferrite PM generator is 2.4 times higher, the costs of the generators are approximately similar since the rare-earth magnets are much more expensive than ferrite ones.

As symbolized in many logos, mechanical gears have significant impact on daily life and industrial modern society. By fully utilizing the mechanical gears and gearboxes, torque and speed can be properly varied for various applications. However, they inevitably suffer from the demerits of annoying noise, contact friction and regular maintenance. Magnetic gears are considered as one of the most promising candidate for the traditional mechanical gears because they offer the advantages of physical isolation, maintenance free, silent operation and inherent overload protection. However, a direct replacement of mechanical gears by magnetic gears cannot solve the problems aroused by the mechanical gearboxes. Namely, the gear ratio of magnetic gears cannot be adjusted whereas the gear ratio of mechanical gears can be flexibly varied via the gearboxes for different load requirements.
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\nIt is well known that the renaissance of magnetic gears mainly attributes to the invention of rare-earth permanent magnet (PM) materials which take the definite advantages of high energy and flux density. Although the rare-earth PM materials such as neodymium-iron-born (NdFeB) and samarium-cobalt (SmCo) are widely adopted for magnetic gears, there is an increasing concern on the price and supply of the rare-earth elements. Particularly, the use of non-rare-earth aluminum- nickel-cobalt (Alnico) PM material takes the merit of high Curie temperature which is very acceptable for industrial application. Also, by purposely employing the low coercivity of the Alnico PM material, the memory machines perform controllable magnetization to flexibly vary the air-gap flux density, hence achieving the wide constant-power speed range.
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\nThe purpose of this thesis is to design a new type of magnetic variable gear by combining the concept of magnetic gear and the concept of memory machine. Firstly, the background information and the development of flux-controllable PMs are introduced. Secondly, the previous research worked on magnetic gears is presented. Next, the cost-effectiveness comparison between rare-earth PMs and non-rare-earth PMs is sufficiently conducted. After that, a new magnetic gear with multiple controllable gear ratios is proposed, with emphasis on mathematical deduction of the design principle and operation principle. By using finite element analysis, the electromagnetic performances of proposed magnetic variable gear at different gear ratios are investigated. Then design optimization of coaxial magnetic variable gear is conducted and analyzed. Two kinds of methods aiming to increase the torque capability and reduce the torque ripple are discussed. Furthermore, the concept of coaxial magnetic variable gear is extended to the axial-field counterpart. The electromagnetic performances of proposed axial-field MVG is investigated by finite element method. Furthermore, two kinds of industrial applications of coaxial magnetic gears, including wind power system and hybrid propulsion system, are investigated. Finally, a prototype is built up for the verification of the gear ratio changing concept. Hence the corresponding validities are further verified by experimental results.

We present development of multi-material Fused deposition modeling (FDM) 3D printer. Most of the FDM type of 3d printers are able to print plastics such as ABS, PLA and Nylon in a single run. In order to overcome this problem, we have developed an affordable multi-material 3D printer that can print an object with a different kind of soft and hard material in a single run. The combination of printing soft and hard materials in a single run will open the doors to various applications such as soft robotics, actuators and sensors. One of the main printing materials for this printer is the conductive based soft filament made by our laboratory "Soft & Wet Matter Engineering Laboratory", along with other different soft filament and hard plastic filament to create a fully functional, multi-material printer to print objects in a single printing run with greater diversity and lower cost than any other single material printer. We have developed a single screw-based extruder 3D printer extruder type 3D printer that can print both soft and hard materials. Instead of using a filament to 3D print objects, we have used pellets of different materials, including carbon-based conductive composites. Such type of single screw base extruder 3D printer will be a new addition to the additive manufacturing process.