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-Direction Layered Deposition: An Overview of Process Planning Methodologies

Layered Manufacturing (LM) techniques build a part by adding thin layers of material. In many LM processes overhangs require the deposition of sacrificial supports resulting in an increase in the build time, wastage of material and costly post-processing. This has led to the development of LM systems which can deposit material along multiple directions and eliminate the need for supports. We survey the configurations of available multi-direction deposition systems. An overview of the process planning challenges is presented. Literature on process planning methodologies is reviewed.Mechanical Engineerin

Investigation into adaptive slicing methodologies for additive manufacturing

Adaptive slicing is a methodology used to optimise the trade-off between build-time reduction and geometric accuracy improvement in additive manufacturing (AM). It works by varying decreasing layer thickness in sections of high curvature. However, current adaptive slicing methodologies all face the difficulty of adjusting layer thickness precisely according to the variations of the model’s geometry, thereby limiting the geometric accuracy improvement. This thesis tackles this difficulty by indicating the geometric variations of the model by evaluating the ratio of the volume of each sliced layer’s geometric deviation to the volume of its corresponding region in the digital model. This indication is accomplished because all the topological information of the corresponding region is considered in assessing the geometric deviation (volume) between each sliced layer and its corresponding region. Through having this precise indication to modify each layer thickness, this thesis aims to develop an adaptive slicing that can mitigate geometric inaccuracies (e.g. staircase effect and dimensional deviation) while balancing the build time. This slicing is evaluated using six different test models, compared with three current slicing methodologies (voxelisation-based, cusp height-based, and uniform slicing), and validated through computation and manufacturing. These validations all demonstrate that volume deviation-based slicing optimises the trade-off between build-time reduction and geometric accuracy improvement better than the other existing slicing methodologies. For example, it can reduce the build time by nearly half compared to other existing slicing methodologies assuming a similar degree of printed parts’ geometric accuracy. The improved trade-off optimised by volume deviation-based slicing can directly benefit the AM applications in the aerospace and medical industries. This is because current research has shown geometric inaccuracies are the primary cause of reducing energy efficiency (e.g. turbine blade and wind tunnel testing models) and having failed implants (e.g. hip and cranial implants, dental prostheses). In addition to improving the geometric accuracy of AM-constructed parts, volume deviation-based slicing may also be incorporated with non-planar layer slicing. Non-planar layer slicing is designed to mitigate the mechanical anisotropy of printed parts by using curved-sliced layers. By integrating volume deviation-based slicing with non-planar layer slicing, the thickness of each curved-sliced layer can be adjusted according to the model’s geometric variations and, therefore, has a possibility of reducing the geometric inaccuracies and mechanical anisotropy simultaneously.Open Acces

Process planning for robotic wire ARC additive manufacturing

Robotic Wire Arc Additive Manufacturing (WAAM) refers to a class of additive manufacturing processes that builds parts from 3D CAD models by joining materials layerupon- layer, as opposed to conventional subtractive manufacturing technologies. Over the past half century, a significant amount of work has been done to develop the capability to produce parts from weld deposits through the additive approach. However, a fully automated CAD-topart additive manufacturing (AM) system that incorporates an arc welding process has yet to be developed. The missing link is an automated process planning methodology that can generate robotic welding paths directly from CAD models based on various process models. The development of such a highly integrated process planning method for WAAM is the focus of this thesis

Comparing Slicing Technologies for Digital Light Processing Printing

In additive manufacturing (AM), slicing is a crucial step in process planning to convert a computer-aided design (CAD) model to a machine-specific format. Digital light processing (DLP) printing is an important AM process that has a good surface finish, high accuracy, and fabrication speed and is widely applied in many dental and engineering industries. However, as DLP uses images for fabrication different from other toolpath-based processes, its process planning is understudied. Therefore, the main goal of this paper is to study and compare the slicing technologies for DLP printing. Three slicing technologies are compared: contour, voxelization, and ray-tracing

Design of a Customized Multi-Directional Layered Deposition System Based on Part Geometry

Multi-Direction Layered Deposition (MDLD) reduces the need for supports by depositing on a part along multiple directions. This requires the design of a new mechanism to reorient the part, such that the deposition head can approach from different orientations. We present a customized compliant parallel kinematic machine design configured to deposit a set of part geometries. Relationships between the process planning for the MDLD of a part geometry and considerations in the design of the customized machine mechanism are illustrated. MDLD process planning is based on progressive part decomposition and kinematic machine design uses dual number algebra and screw theory.Mechanical Engineerin

Applications of Additive Manufacturing for Norwegian Oil and Gas Industries

The additive manufacturing or 3D printing (3DP) technologies have undergone exponential expansion, particularly in the previous couple of decades. Additive manufacturing technologies have paved the way for easy component manufacturing in large-scale and high-performance businesses. The introduction of desktop 3D printers has established 3DP as a reliable technique for generating prototypes and direct parts from CAD files. This technology is employed in an industrial setting for a range of purposes, including the invention and manufacture of customized and task-specific tools. This thesis looks at the benefits and drawbacks of deploying a 3D printer on an offshore facility to encourage on-site part manufacture, save operating costs, and reduce downtime. The thesis proposes ways for speeding and simplifying the creation of customized products. The approaches utilized were aimed to discover flaws and opportunities in offshore platforms' 3D printing processes. It also includes a comparative examination of production procedures, which will aid in decision-making. Furthermore, the technical structure of the proposed method would outline a path for developing prototype designs and tools to address identified difficulties. The proposed ideas and produced technologies could have a positive impact on the oil and gas industries' operations. The thesis also goes over the equipment needed for post-processing printed parts, as well as their availability on offshore platforms. The reliability issues associated with 3D printed parts are also addressed, which will improve RAMS analysis of printed parts

A Framework for Hybrid Manufacturing in Robotic Cells

Compared to other additive technologies, Wire and Arc Additive Manufacturing (WAAM) offers high deposition rates, flexibility and a larger build volume as well as reduction of material waste. WAAM can be combined with a subtractive technology in hybrid robotic cells to further increase the application scope, thus producing products with improved surface finish where needed. However, there are some open issues that limit this process. So, the main goal of this paper is to review current research developments and provide a framework aimed at manufacturing parts by hybrid cells. A procedure is defined which moves from the evaluation of the designed shapes, their analysis to identify a proper manufacturing sequence until the elaboration of the instructions for the cell automaton controllers. Main WAAM issues are outlined to identify main research directions, and a test case is presented to highlight the process phase

Optimization and visualization of rapid prototyping process parameters.

The optimal selection of rapid prototyping (RP) process parameters is a great concern to RP designers. When dealing with this problem, different build objectives have to be taken into consideration. Using virtual rapid prototyping (VRP) systems as a visualization tool to verify the optimally selected process parameters will assist designers in taking critical decisions regarding modeling of prototypes. This will lead to substantial improvements in part accuracy using minimal number of iterations, and no physical fabrication until confident enough to do so. The purpose of this thesis is to demonstrate that virtual validation of optimally selected process parameters can significantly reduce time and effort spent on traditional RP experimentation. To achieve the goal of this thesis, a multi-objective optimization technique is proposed and a model is generated taking into consideration different build objectives, which are surface roughness, support structure volume, build time and dimensional accuracy. The multi-objective method used is the weighted sum method, where a single utility function has been formulated, which combines all the objective functions together. The orders of magnitudes have been normalized, and finally weights have been assigned for each objective function in order to create the general formulation. (Abstract shortened by UMI.)Dept. of Industrial and Manufacturing Systems Engineering. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis2004 .E47. Source: Masters Abstracts International, Volume: 43-03, page: 0959. Adviser: Waguih ElMaraghy. Thesis (M.A.Sc.)--University of Windsor (Canada), 2004

The investigation of a method to generate conformal lattice structures for additive manufacturing

Additive manufacturing (AM) allows a geometric complexity in products not seen in conventional manufacturing. This geometric freedom facilitates the design and fabrication of conformal hierarchical structures. Entire parts or regions of a part can be populated with lattice structure, designed to exhibit properties that differ from the solid material used in fabrication. Current computer aided design (CAD) software used to design products is not suitable for the generation of lattice structure models. Although conceptually simple, the memory requirements to store a virtual CAD model of a lattice structure are prohibitively high. Conventional CAD software defines geometry through boundary representation (B-rep); shapes are described by the connectivity of faces, edges and vertices. While useful for representing accurate models of complex shape, the sheer quantity of individual surfaces required to represent each of the relatively simple individual struts that comprise a lattice structure ensure that memory limitations are soon reached. Additionally, the conventional data flow from CAD to manufactured part is arduous, involving several conversions between file formats. As well as a lengthy process, each conversion risks the generation of geometric errors that must be fixed before manufacture. A method was developed to specifically generate large arrays of lattice structures, based on a general voxel modelling method identified in the literature review. The method is much less sensitive to geometric complexity than conventional methods and thus facilitates the design of considerably more complex structures. The ability to grade structure designs across regions of a part (termed functional grading ) was also investigated, as well as a method to retain connectivity between boundary struts of a conformal structure. In addition, the method streamlines the data flow from design to manufacture: earlier steps of the data conversion process are bypassed entirely. The effect of the modelling method on surface roughness of parts produced was investigated, as voxel models define boundaries with discrete, stepped blocks. It was concluded that the effect of this stepping on surface roughness was minimal. This thesis concludes with suggestions for further work to improve the efficiency, capability and usability of the conformal structure method developed in this work