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-Axis Planning System (MAPS) for Hybrid Laser Metal Deposition Processes

This paper summarizes the research and development of a Multi-Axis Planning System (MAPS) for hybrid laser metal deposition processes. The project goal is to enable the current direct metal deposition systems to fully control and utilize multi-axis capability to make complex parts. MAPS allows fully automated process planning for multi-axis layered manufacturing to control direct metal deposition machines for automated fabrication. Such a capability will lead to dramatic reductions in lead time and manufacturing costs for high-value, low-volume components with high performance material. The overall approach, slicing algorithm, machine simulation for planning validation, and the planning results will be presented

Multi axis slicing for rapid prototyping

With multi-axis capability, direct laser deposition process can produce a metal part without the usage of support structures. In order to fully utilize such a capability, a slicing method for multi-axis metal deposition process is discussed. Using the geometry information of adjacent layers, the slicing direction and layer thickness can be changed as needed. A hierarchy structure is designed to manage the topological information which is used to determine the slicing sequence. The parallel slicing process is studied to build hollow type structure. With such a character, the hole like feature can be deposited directly to save the required machining operation and material cost, which improves the efficiency of the metal deposition process. Combined with direct 3D layer deposition technique, the multi-axis slicing method is implemented --Abstract, page iii

Digital Fabrication of Multi-Material Objects for Biomedical Applications

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Digital fabrication of multi-material biomedical objects

This paper describes a multi-material virtual prototyping (MMVP) system for modelling and digital fabrication of discrete and functionally graded multi-material objects for biomedical applications. The MMVP system consists of a DMMVP module, an FGMVP module and a virtual reality (VR) simulation module. The DMMVP module is used to model discrete multi-material (DMM) objects, while the FGMVP module is for functionally graded multi-material (FGM) objects. The VR simulation module integrates these two modules to perform digital fabrication of multi-material objects, which can be subsequently visualized and analysed in a virtual environment to optimize MMLM processes for fabrication of product prototypes. Using the MMVP system, two biomedical objects, including a DMM human spine and an FGM intervertebral disc spacer are modelled and digitally fabricated for visualization and analysis in a VR environment. These studies show that the MMVP system is a practical tool for modelling, visualization, and subsequent fabrication of biomedical objects of discrete and functionally graded multi-materials for biomedical applications. The system may be adapted to control MMLM machines with appropriate hardware for physical fabrication of biomedical objects.postprin

Designing for Additive Manufacturing - Product and Process Driven Design for Metals and Polymers

Additive Manufacturing (AM) has broken through to common awareness and to wider industrial utilization in the past decade. The advance of this young technology is still rapid. In spoken language additive manufacturing is referred as 3D printing for plastic material and additive manufacturing is left as an umbrella term for other materials i.e. metallic materials and ceramics. As the utilization of AM becomes more widespread, the design for additive manufacturing becomes more crucial as well as its standardization. Additive manufacturing provides new set of rules with different design freedom in comparison with subtractive manufacturing methods. This is thought to empower product driven designs. However, in the AM methods there are process driven variables that limit the designs functions to what could be manufactured. There are often extra steps after production to finalize the design. Topology optimization utilizes product driven design where material is only where it is needed to be. The design is computed without taking into account any manufacturing constrains and only the design in the final application stage is achieved. Topology optimization algorithm is explored in detail for two algorithms. Then these algorithms are compared in case study I to gain better understanding of the algorithms functions. Case study I consists of 2D and 3D algorithms where a 3D level set method algorithm was written for this purpose. The concept of designing for additive manufacturing is examined for polymeric materials in case study II with a help of topology optimization design software tailored for additive manufacturing market. The parts are manufactured with different AM methods, examined and results are explained. The results show an interesting effect of anisotropy and the manufacture methods effect in the part mechanical properties. On the other hand, process driven design and its concepts important as the manufacturing method dictates, what can and should be done economically. Metal AM process constraints are explored in case study III through accuracy studies in metal additive manufacturing at laser powder bed fusion (LPBF) technology. Accuracy and surface studies are concluded to gain a better understanding of the process and manufacturability of metal parts. The gain knowledge is explaned and examples are shown how these are utilized to make metal parts with tailored properties and with minimal post processing needs

Modeling of selective laser sintering/ selective laser melting

Selective laser sintering and selective laser melting are powder based additive manufacturing (AM) process that can rapidly manufacture parts with comparable mechanical properties to conventional manufacturing methods directly from digital files. However, the processing recipe development and design optimization of AM parts are often based on trial and error which erodes the benefit of AM. Modeling is a powerful tool to enable faster development cycle by significantly reducing the experimental efforts. In this paper we discussed the current status of selective laser sintering/melting modeling, in which the laser and powder interaction was studied to understand and predict the process and the properties of fabricated parts. A review of the current approach as well as future directions are presented

Thermophysical Phenomena in Metal Additive Manufacturing by Selective Laser Melting: Fundamentals, Modeling, Simulation and Experimentation

Among the many additive manufacturing (AM) processes for metallic materials, selective laser melting (SLM) is arguably the most versatile in terms of its potential to realize complex geometries along with tailored microstructure. However, the complexity of the SLM process, and the need for predictive relation of powder and process parameters to the part properties, demands further development of computational and experimental methods. This review addresses the fundamental physical phenomena of SLM, with a special emphasis on the associated thermal behavior. Simulation and experimental methods are discussed according to three primary categories. First, macroscopic approaches aim to answer questions at the component level and consider for example the determination of residual stresses or dimensional distortion effects prevalent in SLM. Second, mesoscopic approaches focus on the detection of defects such as excessive surface roughness, residual porosity or inclusions that occur at the mesoscopic length scale of individual powder particles. Third, microscopic approaches investigate the metallurgical microstructure evolution resulting from the high temperature gradients and extreme heating and cooling rates induced by the SLM process. Consideration of physical phenomena on all of these three length scales is mandatory to establish the understanding needed to realize high part quality in many applications, and to fully exploit the potential of SLM and related metal AM processes

Process parameter optimization for direct metal laser sintering (DMLS)

Ph.DDOCTOR OF PHILOSOPH