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Functionality and design of mechanical springs are simple and limited due to manufacturing constraints of conventional fabrication methods being used for making helical and wave springs. In recent era, design for additive manufacturing has proven its great worth to design and manufacture optimal, complex as well as intricate structures with better mechanical and lightweigting properties. This study aims to investigate the mechanical behavior of functionally gradient wave springs as a function of variation in thickness and morphology of each wave. Functionally gradient wave springs incorporated with different morphology and cross-sections including circular, rectangular and combination of both were designed and printed by keeping mass and height constant to investigate their mechanical properties. Loading–unloading experimentation was conducted within the elastic range (90% of compressible distance) in order to study energy absorption/loss, load-bearing capacity and stiffness of all designs. The experimental results were validated by finite element anaylsis (FEA) by providing the identical boundary conditions of experimental setup. The results revealed that the stiffness of wave spring having rectangular cross-section is increased significantly, while energy absorption is almost 90% increased due to circular cross-section of waves. Overall, the design with combination of round and rectangular cross-sectional waves has better stiffness and energy absorption properties. For further investigation of mechanical properties due to variation in cross-section of waves, more designs including semi-circular and filleted waves were designed, and FEA of those showed that 786 N of load-bearing capacity is achieved in the wave spring having semicircular cross-section of waves which is double than the wave spring having variable circular cross-section of waves.

Springs are mechanical devices which are used quite extensively in different industries and mechanisms. Traditionally, springs have been manufactured by wrapping a hot wire around a rotating mandrel. This process has certain limitations because it is difficult to vary the spring parameters such as pitch and wire diameter. However, through the use of AM processes, with the complexity-for-free approach, it is possible to design and manufacture springs with variable spring parameters. Furthermore, it is also possible to create springs with multiple helices as opposed to traditional springs with a single helix. In this study, 32 springs with different numbers of helices, variable pitch profiles, variable wire diameters, and constant mass were designed. The springs were manufactured for experimental validation using HP MJF 520, which is a hybrid AM process. The stiffness of these springs was calculated analytically, through FEA, and experimentally validated. It was observed that increasing the number of helices in a spring leads to an increase in the stiffness of the spring. Furthermore, springs with variable pitch profiles and variable wire diameters have greater stiffness as compared to springs with constant parameters. However, with the increase in stiffness, the fatigue life of the springs decreases exponentially. Improvement in the stiffness of the springs without increasing the mass and therefore cost can lead to new and improved designs. These springs show great potential for industries where weight is an important consideration, such as aerospace and automotive. As these springs have a higher stiffness for the same mass, they can lead to designs with a light weight, and lower package volumes.

Cellular biomaterials with highly controlled microstructures are auspicious materials for medical orthopedics applications either as scaffold or implants due to their capability of encouraging better osseointegration and cell proliferation. This work focuses on the design and optimization of the hip implant by introducing a cellular structure into a solid implant to allow bone tissue ingrowth and reduce stress shielding. The cellular hip implant is incorporated with vintiles lattice topologies having different strut thickness and unit cell sizes to achieve the requirements of bone ingrowth and biomechanical mimic strength. All four optimized cellular hip implants with different unit cell size and porosity were manufactured via selective laser melting (SLM) using the Ti6Al4V material. To predict the mechanical property of hip cellular implant, finite element analysis (FEA) was employed and optimization methods were used for improving the mechanical performance of the hip cellular implant. To evaluate the reduction in stiffness of hip cellular implants, experimental tests were performed based on ISO 7206-4(2010) under static loading conditions. The experimental and simulation force-displacement results show that the optimized cellular hip implant has 62% lower stiffness than its solid counterpart. Moreover, the cellular hip implant was 50% lower in weight than the solid implant. Finally, the result of this study shows that the cellular implants with porosity of 56% and 58% have the potential to be used in orthopedic and prosthetic applications to improve osseointegration.

The mechanical properties such as energy absorption, crushing behavior, and strength-to-weight ratio of graded density structures are significantly better when compared with uniform density counterparts. Graded density structures have been widely investigated due to recent developments in additive manufacturing (AM) technology, which can easily manufacture complex geometries. The study explores the significance of variable-dimension helical spring (VDS) to be used in shoe midsole to improve the stiffness, energy absorption, and energy return. Two novel shoe midsoles are designed using the variable-dimension helical springs and their performance was compared with a third shoe midsole designed using uniform-dimension helical spring (UDS). Variable-dimension shoe midsoles were designed according to the actual pressure distribution applied by the human foot on the midsole. The Multijet fusion AM process was employed for the fabrication of all shoe midsole samples. It is revealed that despite the same mass and bounding box, variable-dimension midsoles have significantly improved mechanical properties compared to uniform-dimension midsole. It is found that the VDS midsole has sixfolds higher force-bearing capacity, and has a lower permanent material setting phenomena when compared to UDS midsole. Moreover, a higher (45%) distortion was found in the UDS midsole after the loading-unloading experiment when compared to the VDS midsole (24%) distortion. A further comparison of the VDS midsole was carried out with the commercially available wave spring-based midsole. Despite about 2-fold higher weight of the wave spring–based midsole, the VDS polymer midsole has higher mechanical properties found in terms of flexibility and force-bearing capacity. Finally, it is concluded that the VDS structure of the midsole can enhance the mechanical properties such as force-bearing capacity, flexibility, and stability with a higher strength-to-weight ratio. This study also proves the feasibility of design and AM of customer-specific shoe midsole.

3D printing techniques have great potential in the direct fabrication of microfluidic and many kinds of molds, such as dental and jewelry models. However, the resolution, surface roughness, and critical dimension uniformity of 3D printing objects are still a challenge for improvement. In this article, we proposed a 405nm light emitting diode (LED) backlight module based on stacks of structured films, and the full width half maximum (FWHM) of the angular distribution of this module is reduced to less than ± 15°. Compared with the commercial lens array optical module, the ten points intensity uniformity of an 8.9” build area is improved from 56% to 80%. Moreover, we found that the surface roughness and the sharpness of the edge of the printing objects are also obviously improved by our novel quasi-collimated LED backlight module. These features give us a promising way for the application of microfluidics and micro-optics components in the future.

Design for additive manufacturing (DfAM) enables the design and fabrication of intricate but application-based functionally optimized geometries by reducing the manufacturing time. It also gave unlimited design freedom to alter any specific parameter and re-generate the design with improved mechanical properties. However, designing a complex and application-specific component needs comprehensive knowledge of drawing, intended usage, high expertise, and command on designing software with ample time. Mechanical springs e.g., wave springs of uniform/complex shaped designs consume a lot of manual hard work. A new design tool is developed for constructing wave springs of different morphologies with uniform or varying design parameters or the combination of both by successfully controlling the number of waves per coil, coil diameter, geometric shape, thickness/width of the strip, the diameter of the wire, wave height, overlap between coils, etc. In this methodology, a graphical user interface (GUI) was developed in which the user can select the type of wave spring which can be either uniform, functional gradient, or hybrid along with every parameter with the geometric as well as dimensional variation is defined through Python code. The code is directly run in Autodesk Fusion 360 software which is used to transform that code into a 3D model with all defined features and can be saved in different formats which can be directly printed. Several designs of uniform and functionally graded/hybrid as well as complex shaped wave springs were successfully designed and manufactured by fused deposition modeling (FDM), stereolithography (SLA), and powder bed fusion (MJF) technology with different materials which resulted in a good surface finish, smooth printability, and less dimensional variation. In addition to that, this method can prove its versatility to design complex wave springs for research as well as for industrial usage as per load requirements without having in-depth design expertise and spending much less time.

The mechanical properties of lattice structure are affected by the properties of the parent material, the relative density, and the topology of the unit cell. In many applications, the goal is to have a lightweight and stiff structure. Increase in stiffness can be achieved by increasing relative density but this also increases the mass. The second method to enhance the mechanical properties is by tailoring the topology of the unit cell. This method has an advantage over the previous method as it results in an increase in stiffness without any increase in mass of the structure. Periodic lattice structures can be designed for multiple constraints such as optimization of stiffness and energy absorption. Presence of sharp corners and edges causes stress concentrations which lead to lower energy absorption efficiency. This can be rectified by adding fillets. In this paper, two methods are shown to increase the stiffness and the specific energy absorption efficiency of the lattice structures without increasing the mass or relative density. Improvement in mechanical properties can be achieved by addition of fillets at the edges and by placing beams parallel to the loading direction. These improvements were applied to two lattice structures: Kelvin and Octet truss. Multi-jet fusion additive manufacturing was used to fabricate the samples for performing uniaxial compression testing. The results show a marked improvement in stiffness and energy absorption efficiency in the structures which incorporate fillets and vertical beams in the unit cells. Stiffness of Kelvin was improved by 32% by adding fillets and 70% by adding crossbars. The energy absorption efficiency was increased by 50% in Kelvin by adding fillets. Furthermore, the post-yield behavior and failure mechanism were also changed due to the addition of these elements.

Recent advances in additive manufacturing (AM) have made the direct manufacturing of intricate shapes such as metamaterials and complex geometries easier, more efficient, faster, and optimally functional, as compared with the manufacturing of simple solid blocks. In this study, the authors conducted experimental investigations and simulations on the energy absorption, stiffness, and deflection of various variable dimension helical springs fabricated by a recently developed high-speed AM technology, namely, the multijet fusion (MJF) system. The variable dimension helical springs were designed by defining various parameters such as the pitch, diameter of the spring wire and spring coil, and total height of the spring. For comparison, the total masses, bounding boxes, and total heights of all samples were kept constant. The results show that the variable parameters (e.g., shape) significantly affect the properties of helical springs; therefore, the stiffness and deformation can be controlled by varying them for a particular application. Furthermore, in designing variable dimension helical springs, nonlinear force–displacement behaviors and stiffness, along with reductions in weight and maximum stresses, can be obtained. Finally, it was concluded that by optimally defining the above parameters, a spring with an ideal geometry can be designed, thereby realizing comfort, stability, and reliability, along with other application-specific benefits (e.g., lightweight).

Cellular structures are promising applicants for additive manufacturing (AM), due to their best capabilities over solid ones such as high strength-to-weight ratio, having porosity, and light in weight. New vintile cellular structures and with the existing five different cellular structures namely cubic, tetrahedron, hexagon, octagon, and rhombic dodecahedron were designed and the effect of unit size, lattice topology, porosity, and optimization of cellular structures on the mechanical properties were discussed in this study. Eighty-four samples with different cell sizes, lattice topologies, and porosities were printed using VisiJet M3 Crystal material on Projet 3510 HDMax 3D printer. Then, electro-optical microscopic is used to determine the pore size. Based on predesigned cellular structures, finite element analysis (FEA) and experimental work were performed to estimate and evaluate the mechanical properties of cellular structures. Results shown that the cellular structure with vintile lattice topology performs less stress and less deformation than the other cellular structures. The experiment results were in good conformance with the result obtained from simulation. This study is not only limited to cellular structure design for biomedical applications but also compared the mechanical performance of uniform density and variable density cellular structures. Both non-optimized and optimized vintile cellular structures is finally tested with FEA and experiments have been carried out on samples fabricated by material jetting, and both results have shown that the optimized cellular structure had much less stress and lower deformation than the non-optimized cellular structure.

Functionally graded lattice structures have attracted much attention in engineering due to their excellent mechanical performance resulting from their optimized and application-specific properties. These structures are inspired by nature and are important for a lightweight yet efficient and optimal functionality. They have enhanced mechanical properties over the uniform density counterparts because of their graded design, making them preferable for many applications. Several studies were carried out to investigate the mechanical properties of graded density lattice structures subjected to different types of loadings mainly related to tensile, compression, and fatigue responses. In applications related to biomedical, automotive, and aerospace sectors, dynamic bending and rotational stresses are critical load components. Therefore, the study of torsional properties of functionally gradient lattice structures will contribute to a better implementation of lattice structures in several sectors. In this study, several functionally gradient triply periodic minimal surfaces structures and strut-based lattice structures were designed in cylindrical shapes having 40% relative density. The HP Multi Jet Fusion 4200 3D printer was used to fabricate all specimens for the experimental study. A torsional experiment until the failure of each structure was conducted to investigate properties of the lattice structures such as torsional stiffness, energy absorption, and failure characteristics. The results showed that the stiffness and energy absorption of structures can be improved by an effective material distribution that corresponds to the stress concentration due to torsional load. The TPMS based functionally gradient design showed a 35% increase in torsional stiffness and 15% increase in the ultimate shear strength compared to their uniform counterparts. In addition, results also revealed that an effective material distribution affects the failure mechanism of the lattice structures and delays the plastic deformation, increasing their resistance to torsional loads.

Cellular structures are made up of an interconnected network of plates, struts, or small unit cells and acquire many unique benefits such as, high strength-to-weight ratio, excellent energy absorption, and minimizing material requirements. When compared with the complicated conventional processes, additive manufacturing (AM) technology is capable of fabricating geometries in almost all types of shapes, even with the small cellular structures inside, by adding material layer-by-layer directly from the digital data file. All major industries have been exploiting the benefits of cellular structures due to their prevalence over a wide range of research fields. To date, there are a few state-of-the-art reviews compiled focusing on a specific area of lattice structures, but many aspects still need to be reviewed. Therefore, this paper aims to provide a comprehensive review of the various lattice morphologies, design, and the AM of the cellular structures. Furthermore, the superior properties of the additively fabricated structure, as well as the applications and challenges, are presented. The conducted review has identified the significant limitations and gaps in the existing literature and has highlighted the areas that need further research in the design, optimization, characteristics, and applications, and the AM of the cellular structures. This review would provide a more precise understanding and the state-of-the-art of AM with the cellular structures for engineers and researchers in both academia and industrial applications.

The primary concern of the Industry 4.0 is the direct digital manufacturing of customized products on demand at high production speed, high accuracy with functional material property. Although the unique capabilities of existing additive manufacturing technologies make it suitable for direct digital manufacturing, there are numerous limitations which include low printing speed, less accuracy and repeatability, and a limited selection of materials for a particular application. Therefore, a high-speed additive manufacturing approach is proposed in this paper, that is capable of achieving high speed of production, high accuracy, and surface finish, and functional material property. For better understanding, authors describe those additive manufacturing technologies that are capable of achieving the aforementioned characteristics. For validation, samples of various dimensions were 3D printed on a selective laser sintering and a high-speed multijet fusion 3D printer. The results were compared in the context of printing speed, surface roughness (Ra), and hardness of printed parts. Results revealed that the multijet fusion process is significantly faster than its counterpart while sacrificing Ra to some extent but the hardness of printed parts is not changed significantly. The selective laser sintering-printed samples had a 15% lower Ra compared with multijet fusion samples. The results also revealed that the multijet fusion process might be able to print composite/multi-materials; however, more research needs to be done.

Lattice structures possess many superior properties over solid materials and conventional structures. Application-oriented lattice structure designs have become a choice in many industries, such as aerospace, automotive applications, construction, biomedical applications, and footwear. However, numerical and empirical analyses are required to predict mechanical behavior under different boundary conditions. In this article, a novel surface-based structure named O-surface structure is designed and inspired by existing Triply Periodic Minimal Surface morphologies in a particular sea urchin structure. For comparison, both structures were designed with two different height configurations and investigated for mechanical performance in terms of compression, local buckling, global buckling, and post-buckling behavior. Both simulation and experimental methods were carried out to reveal these aforementioned properties of samples fabricated by multi jet fusion technology. The sea urchin structure exhibited better mechanical strength than its counterpart, with the same relative density almost two-folds higher in the compressive response. However, the O-surface structure recorded more excellent energy absorption and flexible behavior under compression. Additionally, the compression behavior of the O-surface structure was progressive from top to bottom. In contrast, the sea urchin structure was collapsed randomly due to originated cracks from unit cells’ centers with local buckling effects. Moreover, the buckling direction of structures in long columns was also affected by keeping the relative density constant. Finally, based on specific strength, the O-surface structure exhibited 16-folds higher specific strength than the sea urchin structure.

In the Personal Computer (PC) industry, systems with updated configurations, components, and new technologies are introduced to the market each year. Resource arrangement and the prediction of market requirements for products are common challenges in each development phase of these products. Technologies such as Artificial Intelligence (AI), the Internet of Things (IoT), and cloud services influence the PC industry, and product strategies must be examined to fit the requirements of the market. Common designs and market predictions can influence product line resource arrangements, and 5G applications are causing an increasing demand for 5G-enabled products in the market. However, PC systems based on PCI Express, NVMe, USB, and TPM have been introduced into the market with more secure solutions, and common designs and predictable market demand can provide more reliable strategies for navigating these issues. The research reported here is based on the serial bus system, which should simplify protocol transition between PCI Express, CXL, USB 4, and NVMe. Serial bus behavior should also influence performance and power consumption. Product strategies could be based on securing demand with power and performance in AI, the IoT, cloud storage, and high-performance computing. Based on performance and power requirements, application layer devices can use PCIe-based systems to provide secure solutions to extend 5G system reliability.

This paper presents a novel optical encoder, M-encoder, which can be used within high-precision metrology systems based on the technology of customized prism and homodyne detection. The M-encoder is an exposed encoder measuring reflective glass and metal scale, which is targeting the biggest area of the encoder market, 20 µm pitch, and has a resolution under 100 nm. The error of 23 nm for 100 mm traveling distance has been measured. The applied technology has successfully improved alignment tolerances, in which the tolerance of installation achieved to ± 0.5 ∘ , ± 0.5 ∘ , and ± 1 ∘ for pitch, yaw, and roll angle, respectively. The accuracy of results has been verified by comparing them with one of the commercial encoders and also by using an HP interferometer. The results show the resolution and accuracy can be compatible with the market products. In addition, a new method of grating calibration has been described based on the Littrow configuration, and the pitch of the fabricated scale by a femtosecond laser has been measured with the accuracy of 2 nm.

In biomedical engineering, the medical orthopedic is a speedily developing multidisciplinary research area to rebuild implants...

Cellular materials with very highly regulated micro-architectures are promising applicant materials for orthopedic medical uses while requiring implants or substituting for bone due to their ability to promote increased cell proliferation and osseointegration. This study focuses on the design of an acetabular cup (AC) cellular implant which was built using a vintiles cellular structure with an internal porosity of 56&ndash, 87.9% and internal pore dimensions in the range of 600&ndash, 1200 &mu, m. The AC implant was then optimized for improving mechanical performance to reduce stress shielding by adjusting the porosity to produce stiffness (elastic modulus) to match with the bone, and allowing for bone cell ingrowth. The optimized and non-optimized AC cellular implant was fabricated using the SLM additive manufacturing process. Simulation (finite element analysis, FEA) was carried out and all cellular implants are finally tested under static loading conditions. The result showed that on the finite element model of an optimized implant, cellular has shown 69% higher stiffness than non-optimized. It has been confirmed by experimental work shown that the optimized cellular implant has a 71% higher ultimate compressive strength than the non-optimized counterpart. Finally, we developed an AC implant with mechanical performance adequately close to that of human bone.

The properties of lattice structure are influenced by cell morphology, cell size, relative density and tessellations. In this study, the concept of tessellation has been evaluated for structural and functional properties of additively manufactured lattice structures using PA-12 material. The tessellation design of unit lattice cell is inspired by arrangement of atoms in crystal structures. The strategy of mimicking these different arrangements at atomic level to generate mesoscale cellular structures is termed as ‘Atomic Tessellation’. In the current study, arrangement of metallic crystal structures: BCC, FCC and HCP were compared with conventional periodically tessellated SC structure using sea-urchin unit cell for mechanical, energy absorption and structural behaviour properties. The tessellated lattice structures were printed with hybrid AM technology using HP-MJF 4200. The significant effect of tessellations was observed during compression testing of printed samples in terms of their stress-strain behaviour. Lattice structures such as SC, BCC, FCC and HCP_90 shows ‘degradation-prone deformation behaviour’ which is similar to stretch dominated behaviour in structural elements (thin struts and thin walls). On the other hand, HCP tessellation (HCP_0) converts ‘degradation-prone deformation behaviour’ into ‘progressive deformation behaviour’ that is similar to bending dominated behaviour in structural elements. Moreover, significant effects of tessellations were also observed in load bearing and energy absorption properties. Although the study has attempted to introduce the design concept of atomic tessellations from structural point of view, further studies are required to strengthen tessellation based design principles for obtaining different structural and functional properties.

Wave springs have better properties than helical springs in terms of load bearing capacity, mass, energy absorption efficiency, and stiffness. Currently, available wave springs have waves that do not merge with each other (non-contact) with uniform shape and dimensions, manufactured by traditional manufacturing processes using customized machines in which forming, twisting, and cutting processes take place simultaneously. This study aims to design and manufacture wave springs with waves that merge with each other by additive manufacturing (AM). Variable-dimension wave springs are complex in design and can only be manufactured by AM owing to its design freedom, but they have much higher performance in load bearing, stiffness, energy absorption, and energy release compared to both uniform-dimension and uniformly shaped wave springs. To accomplish wave springs manufactured by AM, ten different wave springs were designed and manufactured with variable and uniform dimensions, using a HP MultiJet Fusion printer, by keeping the mass and height of each design constant. Compression tests were carried out for up to ten cycles to study and compare the load bearing capacity, energy absorption, stiffness, and energy loss for all designs. The results showed that the stiffness of the spring increased in the contact wave springs, which ultimately led to more energy absorption in these designs. The taper-wave spring was the best among all designs for load bearing, and it had the highest energy loss capacity, which was validated by finite element analysis of each design.