From 3D Models to 3D Prints: an Overview of the Processing Pipeline

Due to the wide diffusion of 3D printing technologies, geometric algorithms for Additive Manufacturing are being invented at an impressive speed. Each single step, in particular along the Process Planning pipeline, can now count on dozens of methods that prepare the 3D model for fabrication, while analysing and optimizing geometry and machine instructions for various objectives. This report provides a classification of this huge state of the art, and elicits the relation between each single algorithm and a list of desirable objectives during Process Planning. The objectives themselves are listed and discussed, along with possible needs for tradeoffs. Additive Manufacturing technologies are broadly categorized to explicitly relate classes of devices and supported features. Finally, this report offers an analysis of the state of the art while discussing open and challenging problems from both an academic and an industrial perspective.Comment: European Union (EU); Horizon 2020; H2020-FoF-2015; RIA - Research and Innovation action; Grant agreement N. 68044

Multi Objective Optimisation of Build Orientation for Rapid Prototyping with Fused Deposition Modeling (FDM)

The ability to select the optimal orientation of build up is one of the critical factors since it affects the part surface quality, accuracy, build time and part cost. Various factors to be considered in optimisation of build orientation for FDM are build material, support material, build up time, surface roughness and total cost. Experiments were carried out and results are analysed for varying build orientation for primitive geometries like cylinder. An appropriate weighting factor has been considered for various objective functions depending on the specific requirement of the part while carrying out multi-objective optimisation. These analyses will help process engineers to decide proper build orientation.Mechanical Engineerin

Design and Implementation of Asymptotically Optimal Mesh Slicing Algorithms Using Parallel Processing

Mesh slicing is the process of taking a three dimensional model and reducing it to 2.5 dimensional layers that together create a layered representation of the model. The process is used in layered additive manufacturing, three dimensional voxelization, and other similar problems in computational geometry. The slicing process is computationally expensive, and the time required to slice an object can inhibit the viability of layered manufacturing in some industries. We designed and developed a fast implementation of the slicing process, called Sunder, that uses new asymptotically optimal algorithms and takes advantage of parallel processing platforms. To our knowledge, no other slicing implementation leverages massive parallel execution hardware, such as graphics processing units (GPUs), leaving significant potential for improvement. Furthermore, no published set of slicing algorithms completes all three major steps in the slicing process (preprocessing, slicing, and contour assembly) in linear time complexity, which our design achieves. Therefore, our implementation improves the current state of the art in mesh slicing

Superconducting electromagnetic launch system for civil aircraft

This paper considers the feasibility of different superconducting technologies for electromagnetic launch (EML) to assist civil aircraft take-off. EML has the potential of reducing the required runway length by increasing aircraft acceleration. Expensive airport extensions to face constant air traffic growth could be avoided by allowing large aircraft to operate from short runways at small airports. The new system positively affects total aircraft noise and exhaust emissions near airports and improves overall aircraft efficiency through reducing engine design constraints. Superconducting Linear Synchronous Motors (SCLSMs) can be exploited to deliver the required take-off thrust with electromagnetic performance that cannot be easily achieved by conventional electrical machines. The sizing procedure of a SCLSM able to launch A320 in weight is presented. Electromagnetic and thermal aspects of the machine are taken into account including the modelling of ac losses in superconductors and thermal insulation. The metallic high temperature superconductor (HTS) magnesium diboride (MgB2) is used and operated at 20 K, the boiling temperature of liquid hydrogen. With modern manufacturing technology, multifilament MgB2 wires appear to be the most cost-effective solution for this application. Finally the impact of the cryocooler efficiency on the machine performance is evaluated

Paclitaxel Drug Elution from a Biodegradable Stent

Recently, drug-eluting stents have become a common treatment for coronary heart disease. These stents are usually loaded with a drug that prevents restenosis. Unfortunately, there are risks associated with the placement of these metallic structures in the body. Stent thrombosis is one such problem, and can lead to restenosis despite the presence of drug. Advances in biomaterials have led to the development of biodegradable stents, which can reduce the risks associated with stents. However, since it is a relatively new technology, it is not known to what degree the biodegradability affects the drug releasing properties of the stent. We hope to characterize these effects and to determine if the biodegradability reduces the efficacy of the stent when compared to normal non-degradable stents. To accomplish this, we modeled a stent that diminished in size over time using COMSOL Multiphysics, and monitored the drug concentration in the nearby tissue. We established that our model was a viable predictor of actual stent behavior by comparing our simulated results with previous studies. We were then able to determine the optimal initial loading stent concentration of our modeled drug, paclitaxel, to ensure therapeutic levels in the tissue. Lastly, we found that drug concentrations in the tissue were not substantially different between the degradable and non-degradable models. This affirms the effectiveness of using biodegradable stents, showing them as a viable alternative to traditional metal stents

Verification of a mathematical model for layered T-beams

CER73-74MLK-MEC-JRG-JB-EGT-MDV28.March 1974.Includes bibliographical references.An experimental program and the verification of a mathematical model for layered T-beams, developed assuming small deflection theory and including effects of interlayer slip, are described in this report. This research is a part of an overall program to develop a verified analysis procedure for wood joist floor systems. After a description of the construction and load-testing of 14 two-and three-layered T-beams, a brief discussion on the mechanical properties of the materials used is given. The deflections observed in the loading tests are then compared with the predicted deflections given by the mathematical model, which used a finite element solution technique. These comparisons for the fourteen T-beams, including two and three-layered systems, formed the primary basis for the verification of the mathematical model. Test results provided by a manufacturer of joist systems were also compared to the mathematical model. Good agreement between the observed and theoretical values were obtained for all tests. These favorable results show the validity of this general layered beam theory