Rapid prototyping systems have advanced significantly with respect to material capabilities, fabrication speed, and surface quality. However, build jobs are still manually activated one at a time. The result is non-productive machine time whenever an operator is not at hand to make a job changeover. A low-cost auxiliary system, named Continuous Layered Manufacturing (CLM), has been developed to automatically load and unload the FDM 1600 rapid prototyping system (Stratasys, Inc.). The modifications made to the FDM 1600 system are minimal. The door to the FDM 1600 build chamber is removed, and the .SML build files that are used to drive the FDM 1600 are modified at both ends to facilitate synchronized operation between the two systems. The CLM system is capable of running three consecutive build jobs without operator intervention. As long as an operator removes finished build jobs, and adds new build trays before at most every three build jobs, the FDM can operate near indefinitely. The impact of the CLM system on the productivity of the FDM 1600 rapid prototyping system is demonstrated by the expected reduction from the customary eight weeks down to a future three and one-half weeks required to complete the typical forty build jobs during a semester in the course ME 4644 Introduction to Rapid Prototyping at Virginia Tech.
xerography, layered manufacturing, electrophotographic printing, laser printing, electrostatic printing, personal fabrication, three dimensional printing, personal fabricator, electrophotography, three dimensional laser printing, rapid prototyping, solid freeform fabrication, toner, dry toner, and santa claus machine
A machine capable of making 'anything' has always existed in the realm of science fiction. The advent of the Rapid Prototyping machines partially fulfilled the realization of a personal fabricator by breaking the boundaries on the geometric form that could be realized through a machine in a single set up. The proliferation of the rapid prototyping machines into the industry and finally for domestic use, has been hampered by their costs, size and process limitations. The current trends in the Rapid Prototyping industry has been to develop machines capable of manufacturing parts in functionally graded materials. In order to achieve this, there is a need to develop means to precisely deposit a controlled combination of materials within the volume of a part. Electrophotography has been used for decades for monochrome and multicolor dry toner printing. The application of electrophotography for the generation of 3D parts through layered manufacturing has been left mostly unexplored. This thesis suggests guidelines for the development of an electrophotography based rapid prototyping process that would be cost effective in comparison with current commercial rapid prototyping technologies, as well as have the capability of depositing multiple materials. The initial research involved attempts to adapt a commercial electrophotographic printer to print in 3D. Later, experiments were conducted to indigenously build an electrophotography based layered manufacturing system. The research involved the development of transmission systems, development of power supplies to facilitate electrostatic charging, testing of polygon mirror based laser-scanning system, development of fusing and pressing station and experiments with multiple materials. Though a electrophotography based rapid prototyping machine was not realized at the end of this research, substantial evidence was generated to validate future research towards the development of such a system. Future work would involve the development of a completely automated system. Upon the completion of this system, further research could be carried out in the fields of personal fabrication, micro Rapid Prototyping, materials with directional properties, bio and materials, direct write technologies for printing circuits and functionally graded materials.
The purpose of this research is to analyze the layer development and fusing process of a new rapid prototyping process. The new rapid prototyping process is 3D laser printing, and this process is under development by researchers at the Department of Industrial Engineering at North Carolina State University. The 3D laser printing process uses principles of electrophotography (laser printing) for layer development. The layer fusing process is achieved by temperature-pressure fusing. A fiberglass reinforced Teflon sheet is to be used as a transfer medium for the layers. The effectiveness of the layer development and fusing process are evaluated via experimentation. A material testing station was developed to simulate the 3D laser printing process, and the specimens' produced were evaluated for their creep rate and uniform fusing characteristics during the temperature-pressure fusing process. The mass-to-area ratio of the layers developed by a laser printer was evaluated for their suitability for 3D laser printing. The effectiveness of Teflon as a transfer medium was compared with paper in a laser printer. The experiments performed indicate that electrophotography can be used as an effective layer development tool, Teflon can be used as an effective receiving medium for ransferring toner for layer development, and temperature-pressure fusing is capable of producing fused layers for producing parts using 3D laser printing.
direct metal fabrication, rapid prototyping, electron beam melting, lattice materials, tunable materials, lunar regolith, mesh structures, and layered manufacturing
Layered manufacturing has for long been used for the fabrication of non-functional parts using polymer-based processes. Developments in laser beam and electron beam welding technologies and their adoption to layered manufacturing has made it possible to fabricate high-density functional parts in metal irrespective of the level of complexity. The Electron Beam Melting (EBM) process by Arcam AB is one such layered manufacturing process that utilizes a focused electron beam to process metal powder, layer by layer, in a vacuum environment. Research conducted as part of this body of work, looks into the development of both bulk materials in the form of metal alloys and ceramic metal-matrix composites as well as the development of tunable mechanical & thermal metamaterials. Simulation models to approximate electron beam melting were suggested using commercial finite element analysis packages. A framework was developed based on the finite difference method to simulate layered manufacturing using Arcam ABÃ¢â‚¬â„¢s electron beam melting process. The outputs from the simulation data could be used for the better understanding the local melting, grain evolution, composition and internal stresses within a freeform-fabricated metal parts.
Mechanics, STL Modification, Vertex Translation Algorithm (VTA), STL Facet Isolation, GD and T Errors, Chord Error, and Layered Manufacturing
Layered Manufacturing machines use the Stereolithography (STL) file to build parts by various Rapid Prototyping and Rapid Manufacturing processes. When a curved surface is converted from a CAD file to STL, it results in a geometrical distortion. Parts manufactured with this file, may not satisfy Geometric Dimensioning and Tolerance (GD and T) requirements due to approximated geometry. Current algorithms built in CAD packages have export options to globally reduce this distortion which leads to an increase in the file size and pre-processing time.An innovative approach to locally reduce the GD and T errors at feature level is presented in this research. The algorithm presented in this work performs virtual manufacturing, inspection and STL modification iteratively, on a feature STL file until the specified GD and T parameter on the feature surface is satisfied. The approach, termed as the Vertex Translation Algorithm (VTA), compares STL surface to the NURBS design surface, while computing the chord error at multiple points on the STL facets. The point on design surface with largest chord error is selected as the new vertex and new facets are generated. The algorithm ensures selective and localized modification of STL file, and satisfies the GD and T requirements. Facets corresponding to a feature surface are isolated from the main part STL with a novel Facet Isolation Algorithm. The modified feature STL is stitched back to the main STL after modification. This algorithm ensures selective and localized STL modification, to produce a part with required GD and T specifications. In this research chord error, profile error, cylindricity and surface roughness have been evaluated on test parts and an improvement in values has been observed with each modification.