In recent years rapid prototyping technology has been implemented in many spheres of industry, particularly the field of product development. Existing process provide the capability to rapidly produce a tangible solid part, directly from three dimensional CAD data, from a range of nonmetallic materials. In many situations the desired end product of a development cycle is a metallic object, whether a component or a tool. The development of a system capable of the direct manufacture of fully dense, metal parts is therefore seen as an important landmark in the evolution of rapid prototyping technology. A unique experimental project has been carried out to investigate the potential of laser surface cladding by pneumatic powder delivery to form the basis for such a process. A layered manufacturing part building strategy is proposed, in which laser cladding is used to deposit the near net shape of each layer. Conventional machining techniques are then used to trim each layer to the exact dimensions specified by the CAD data. A multi-kilowatt carbon dioxide laser was integrated with a four axis machine tool to create an opto-mechanical workstation on which to perform the process. A detailed study of the effects of cladding process parameters on the geometry of the deposited metal was carried out and quantitative relationships derived. These relationships are used to select process parameters appropriate to the geometry of the deposition required. A numerical method to fully describe the deposited clad geometry was developed in order that efficient cutter paths could be generated for the back machining cycle. These relationships are also used to determine the minimum size of deposited bead from which the required layer section may be machined, in order to optimise process efficiency. The application of the technique to the generation of a variety of simple geometries was investigated and the potential problems identified. A preliminary investigation into the process accuracy is made, relating specifically to the predictability of the geometry of multiple layer depositions and the distortion of parts as subsequent layers are deposited. The limits of geometrical complexity possible with the current apparatus, and the unsatisfactory build times involved, suggest that the most attractive application of this technique is as part of a hybrid process, adding a novel additive dimension to existing automated fabrication techniques.

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. / Master of Science

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Today's commercial rapid prototyping systems (i.e., solid freeform fabrication, layered manufacturing) rely on human intervention to load and unload build jobs. Hence, jobs are processed subject to both the machine's and the operator's schedules. In particular, first-in-first-out (FIFO) queuing of such systems will result in machine idle time whenever a build job has been completed and an operator is not available to unload that build job and start up the next one. These machine idle times can significantly affect the system throughput, and, hence, the effective cost rate. This thesis addresses this problem by rearranging the job queue to minimizing the machine idle time, subject to the machine's and operator's schedules. This is achieved by employing a general branch-and-bound search method, that, for efficiency, reduces the search space by identifying contiguous sequences and avoiding reshuffling of those sequences during the branching procedure. The effectiveness of this job scheduling optimization has been demonstrated using a sequence of 30 jobs extracted from the usage log for the FDM 1600 rapid prototyping system in the Department of Mechanical Engineering at Virginia Tech. / Master of Science

Rapid prototyping is a relativity new technology and is based on layered manufacturing which has similarities to the method an ordinary desktop paper printer works. This research is to obtain a better understanding on how to use computer graphics software, in this particular case Autodesk Maya, to create a model. The goal is to understand how to create a suitable mesh of a 3D model for use with a 3D printer and produce a printed model that is equivalent to the CAD software 3D model. This specific topic has not been scientifically documented which has resulted in an actual 3D model.

3D printing applications have achieved increased success as an additive manufacturing (AM) process. Micro-structure of mechanical/biological materials present design challenges owing to the resolution of 3D printers and material properties/composition. Biological materials are complex in structure and composition. Efforts have been made by 3D printer manufacturers to provide materials with varying physical, mechanical and chemical properties, to handle simple to complex applications. As 3D printing is finding more medical applications, we expect future uses in areas such as hip replacement - where smoothness of the femoral head is important to reduce friction that can cause a lot of pain to a patient. The issue of print resolution plays a vital role due to staircase effect. In some practical applications where 3D printing is intended to produce replacement parts with joints with movable parts, low resolution printing results in fused joints when the joint clearance is intended to be very small. Various 3D printers are capable of print resolutions of up to 600dpi (dots per inch) as quoted in their datasheets. Although the above quoted level of detail can satisfy the micro-structure needs of a large set of biological/mechanical models under investigation, it is important to include the ability of a 3D slicing application to check that the printer can properly produce the feature with the smallest detail in a model. A way to perform this check would be the physical measurement of printed parts and comparison to expected results. Our work includes a method for using ray casting to detect features in the 3D CAD models whose sizes are below the minimum allowed by the printer resolution. The resolution validation method is tested using a few simple and complex 3D models. Our proposed method serves two purposes: (a) to assist CAD model designers in developing models whose printability is assured. This is achieved by warning or preventing the designer when they are about to perform shape operations that will lead to regions/features with sizes lower than that of the printer resolution; (b) to validate slicing outputs before generation of G-Codes to identify regions/features with sizes lower than the printer resolution.