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The class of models that can be represented by STL files is larger than the class of models that can be printed using additive manufacturing technologies. Stated differently, there exist well-formed STL files that cannot be printed. This paper aims to formalize such a gap and describe a fully automatic procedure to turn any such file into a printable model.

Based on well-established concepts from combinatorial topology, this paper provide an unambiguous description of all the mathematical entities involved in the modeling-printing pipeline. Specifically, this paper formally defines the conditions that an STL file must satisfy to be printable, and, based on these, an as-exact-as-possible repairing algorithm is designed.

It has been found that, to cope with all the possible triangle configurations, the algorithm must distinguish between triangles that bind solid parts and triangles that constitute zero-thickness sheets. Only the former set can be fixed without distortion.

Owing to the specific approach used that tracks the so-called “outer hull,” models with inner cavities cannot be treated.

Thanks to this new method, the shift from a 3D model to a printed prototype is faster, easier and more reliable.

The availability of this easily accessible model preparation tool has the potential to foster a wider diffusion of home-made 3D printing in non-professional communities.

Previous methods that are guaranteed to fix all the possible configurations provide only approximate solutions with an unnecessary distortion. Conversely, this procedure is as exact as possible, meaning that no visible distortion is introduced unless it is strictly imposed by limitations of the printing device. Thanks to such unprecedented flexibility and accuracy, this algorithm is expected to significantly simplify the modeling-printing process, in particular within the continuously emerging non-professional “maker” communities.

Support structures are often needed in additive manufacturing (AM) to print overhangs. However, they are the extra materials that must be removed afterwards. When the supports have many contacts to the model or are even enclosed inside some concavities, removing them is very challenging and has a risk of damaging the part. Therefore, the purpose of this paper is to develop a new type of tree-support, named Escaping Tree-Support (ET-Sup), which tries to build all the supports onto the build plate to minimize the number of contact points.

The methodology is to first classify the support points into three categories: clear, obstructed and enclosed. A clear point has nothing between it and the build plate; an obstructed point is not clear, but there exists a path for it to reach the build plate; and an enclosed point has no way to reach the build plate. With this classification, the path for the obstructed points to come clear can be found through linking them to the clear points. All the operations are performed efficiently with the help of a ray representation.

The method is tested on different overhang features, including a lattice ball and a mushroom shape with a concave cap. All the supports generated for the examples can find their way to the build plate, which looks like they are escaping from the model. The computation time is around one second for these cases.

This is the first time truly realizing this “escaping” property in the generation of tree-like support structures. With this ET-Sup, it is expected that the AM industries can reduce the manufacturing lead time and save much labor work in post-processing.

The purpose of this paper is to describe a novel design workflow for the digital fabrication of custom-made orthoses (CMIO). It is intended to provide an easier process for clinical practitioners and orthotic technicians alike. It further functions to reduce the dependency of the operators’ abilities and skills.

The technical assessment covers low-cost three-dimensional (3D) scanning, free computer-aided design (CAD) software, and desktop 3D printing and acetone vapour finishing. To analyse its viability, a cost comparison was carried out between the proposed workflow and the traditional CMIO manufacture method.

The results show that the proposed workflow is a technically feasible and cost-effective solution to improve upon the traditional process of design and manufacture of custom-made static trapeziometacarpal (TMC) orthoses. Further studies are needed for ensuring a clinically feasible approach and for estimating the efficacy of the method for the recovery process in patients.

The feasibility of the process increases the impact of the study, as the great accessibility to this type of 3D printers makes the digital fabrication method easier to be adopted by operators.

Although some research has been conducted on digital fabrication of CMIO, few studies have investigated the use of desktop 3D printing in any systematic way. This study provides a first step in the exploration of a new design workflow using low-cost digital fabrication tools combined with non-manual finishing.

There are over 40 million amputees globally with more than 185,000 Americans losing their limbs every year. For most of the world, prosthetic devices remain too expensive and uncomfortable. This paper aims to outline advancements made by a multidisciplinary research group, interested in advancing the restoration of human motion through accessible lower limb prostheses.

Customization, comfort and functionality are the most important metrics reported by prosthetists and patients. The work of this paper presents the design and manufacturing of a custom made, cost-effective and functional three-dimensional (3D) printed transtibial prosthesis monocoque design. The design of the prosthesis integrates 3D imaging, modelling and optimization techniques coupled with additive manufacturing.

The successful fabrication of a functional monocoque prosthesis through 3D printing indicates the workflow may be a solution to the worldwide accessibility crisis. The digital workflow developed in this work offers great potential for providing prosthetic devices to rural communities, which lack access to skilled prosthetic physicians. The authors found that using the workflow together with 3D printing, this study can create custom monocoque prostheses (Figure 16). These prostheses are comfortable, functional and properly aligned. In comparison with traditional prosthetic devices, the authors slowered the average cost, weight and time of production by 95%, 55% and 95%, respectively.

This novel digital design and manufacturing workflow has the potential to democratize and globally proliferate access to prosthetic devices, which restore the patient’s mobility, quality of life and health. LIMBER’s toolbox can reach places where proper prosthetic and orthotic care is not available. The digital workflow reduces the cost of making custom devices by an order of magnitude, enabling broader reach, faster access and improved comfort. This is particularly important for children who grow quickly and need new devices every few months or years, timely access is both physically and psychologically important.

In this manuscript, the authors show the application of digital design techniques for fabricating prosthetic devices. The proposed workflow implements several advantageous changes and, most importantly, digitally blends the three components of a transtibial prosthesis into a single, 3D printable monocoque device. The development of a novel unibody transtibial device that is properly aligned and adjusted digitally, greatly reduces the number of visits an amputee must make to a clinic to have a certified prosthetist adjust and modify their prosthesis. The authors believe this novel workflow has the potential to ease the worldwide accessibility crisis for prostheses.

This paper aims to present a new methodology to optimize the support generation within the fused deposition modeling process.

Different methods of support generation exist, but they are limited with regards to complex parts. This paper proposes a method dedicated to support generation, integrated into CAD software. The objective is to minimize the volume of support and its impact on a part’s surface finish. Two case studies illustrate the methodology. The support generation is based on an octree’s discretization of the part.

The method represents a first solid step in the support optimization for a reasonable calculation time. It has the advantage of being virtually automatic. The only tasks to be performed by the designer are to place the part to be studied with respect to the CAD reference and to give the ratio between the desired support volume and the maximum volume of support.

In the case studies, a low gain in manufacturing time was observed. This is explained by the honeycomb structure of the support generated by a common slicing software, whereas the proposed method uses a “full” structure. It would be interesting to study the feasibility of an optimized support, with a honeycomb structure but with a preservation of the surface which is in contact with the part.

This solution best fits the needs of the designer and manufacturer already taking advantage of existing solutions. It is adaptable to any part if the withdrawal of support is taken into account. It also allows the designer to validate the generation of support throughout the CAD without breaking the digital chain.

The purpose of this paper is to design a lightweight tree-shaped internal support structure for fused deposition modeling (FDM) three-dimensional (3D) printed shell models.

A hybrid of an improved particle swarm optimization (PSO) and greedy strategy is proposed to address the topology optimization of the tree-shaped support structures, where the improved PSO is different from traditional PSO by integrating the best component of different particles into the global best particle. In addition, different from FEM-based methods, the growing of tree branches is based on a large set of FDM 3D printing experiments.

The proposed improved PSO and its combination with a greedy strategy is effective in reducing the volume of the tree-shaped support structures. Through comparison experiments, it is shown that the results of the proposed method outperform the results of recent works.

The proposed approach requires the derivation of the function of the yield length of a branch in terms of a set of critical parameters (printing speed, layer thickness, materials, etc.), which is to be used in growing the tree branches. This process requires a large number of printing experiments. To speed up this process, the users can print a dozen of branches on a single build platform. Thereafter, the users can always use the function for the fabrication of the 3D models.

The proposed approach is useful for the designers and manufacturers to save materials and printing time in fabricating the shell models using the FDM technique; although the target is to minimize the volume of internal support structures, it is also applicable to the exterior support structures, and it can be adapted to the design of the tree-shaped support structures for other AM techniques such as SLA and SLM.

In the mining industry, a run-of-mine (ROM) stockpile is a temporary storage unit, but it is also widely accepted as an effective method to reduce the short-term variations of ore grade. However, tracing ore grade at ROM stockpiles accurately using most current fleet management systems is challenging, due to insufficient information available in real time. This study aims to build a three-dimensional (3D) model for ROM stockpiles continuously based on fine-grained grade information through integrating data from a number of ore grade tracking sources.

Following a literature review, a framework for a new stockpile management system is proposed. In this system, near real-time high-resolution 3D ROM stockpile models are created based on dump/load locations measured from global positioning system sensors. Each stockpile model contains a group of layers which are separated by different qualities.

Acquiring the geometric shapes of all the layers in a stockpile and cuts made by front wheel loaders provides a better understanding about the quality and quality distribution within a stockpile when it is stacked/reclaimed. Such a ROM stockpile model can provide information on predicating ore blend quality with high accuracy and high efficiency. Furthermore, a 3D stockyard model created based on such ROM stockpile models can help organisations optimise material flow and reduce the cost.

The modelling algorithm is evaluated using a laboratory scaled stockpile at this stage. The authors expect to scan a real stockpile and create a reference model from it. Meanwhile, the geometric model cannot represent slump or collapse during reclaiming faithfully. Therefore, the model is expected to be reconcile monthly using laser scanning data.

The proposed model is currently translated to the operations at OZ Minerals. The use of such model will reduce the handling costs and improve the efficiency of existing grade management systems in the mining industry.

This study provides a solution to build a near real-time high-resolution multi-layered 3D stockpile model through using currently available information and resources. Such novel and low-cost stockpile model will improve the production rates with good output product quality control.

The purpose of the paper was to present a specific case study of how 3D printing was introduced in the chest wall construction process of a specific patient with unique medical condition. A life-size 3D model of the patient’s chest wall was 3D printed for pre-surgical planning. The intent was to eliminate the need for operative exposure to map the pathological area. The model was used for preoperative visualization and formation of a 1-mm thick titanium plate implant, which was placed in the patient during chest wall reconstructive surgery. The purpose of the surgery was to relive debilitating chronic pain due to right scapular entrapment.

The patient was born with a twisted spine. Over time, it progressed to severe and debilitating scoliosis, which required the use of a thoracic brace. Computerized tomography (CT) data were converted to a 3D printed model. The model was used to size and form a 1-mm thick titanium plate implant. It was also used to determine the ideal location for placement of the plate during thoracotomy preoperatively.

The surgery, aided by the model, was successful and resulted in a significantly smaller incision. The techniques reduced invasiveness and enabled the doctors to conduct the procedure efficiently and decreased surgery time. The patient experienced relief of the chronic debilitating pain and no longer need the thoracic brace.

The 3D model facilitated pre-operative planning and modeling of the implant. It also enabled accurate incision locations of the thoracotomy site and placement of the implant. Although chest wall reconstruction surgeries have been undertaken, this paper documents a specific case study of chest wall construction fora specific patient with unique pathological conditions.

The purpose of this study is the generation of a thorough generic heart model optimized for direct 3D printing with silicone elastomers.

The base of the model design is segmentation of CT data, followed by a generic adaption and a constructive enhancement. The model is 3D printed with silicone. An evaluation of the physical model gives indications about its benefits and weaknesses.

The results show the feasibility of a generic design while maintaining anatomical correctness and the benefit of the generic approach to quickly derive a multiplicity of healthy and pathological versions from one single model. The material properties of the silicone model are sufficient for simulation, but the results of the evaluation indicate possible improvements, as for most anatomical features, the used silicone is too hard and too stretchable.

Previous developments mostly focus on patient-specific heart models. In contrast, this study sets out to explore the possibility and benefits of a generic approach. Standardized validated models would allow comparability in surgical simulation.

Breast cancer is the most diagnosed type of cancer in the world, and mastectomies to remove tumors are still common. An external breast prosthesis (EBP) can be used to minimize the asymmetry, due to the ablation. Some governments do not cover costs of that assistive technology, and women end up using socks and fabric pockets filled with seeds, to simulate the volume lost in the surgery. This study aims to offer to those women a decent solution, ergonomic, but still affordable.

The authors interviewed 20 mastectomized Brazilian women, listened to their relate and 3D scanned them, to give rise to personalized external lightweight breast prostheses. The authors used free software for computer-aided design and computer-aided manufacturing, and low-cost 3D printers. From the strategy of bespoke products, this study generalized the method, to conceive mass customized prostheses, in a compromise solution that reduces personalization, conserving the best features of design.

This study achieved a method to manufacture ergonomic, bespoke external breast prostheses, using low-cost technology. Previous literature made them using expensive scanners, software and printers.

The authors validated this method during pandemic, which restricted the number of patients the authors could have access to. This impacted authors’ possibility to work on matching the color of the final product and real skin. The authors understood, though, that precision of color, in the final product, is challenging, because of the peculiar aspects of human skin.

Using the method the authors proposed, personalized external breast prostheses can be manufactured using low-cost resources, democratizing better quality of life for more breast cancer survivors.