A tool-path generation strategy for wire and arc additive manufacturing

This paper presents an algorithm to automatically generate optimal tool-paths for the wire and arc additive manufacturing (WAAM) process for a large class of geometries. The algorithm firstly decomposes 2D geometries into a set of convex polygons based on a divide-and-conquer strategy. Then, for each convex polygon, an optimal scan direction is identified and a continuous tool-path is generated using a combination of zigzag and contour pattern strategies. Finally, all individual sub-paths are connected to form a closed curve. This tool-path generation strategy fulfils the design requirements of WAAM, including simple implementation, a minimized number of starting-stopping points, and high surface accuracy. Compared with the existing hybrid method, the proposed path planning strategy shows better surface accuracy through experiments on a general 3D component

Optimal field coverage path planning on 2D and 3D surfaces

With the rapid adoption of automatic guidance systems, automated path planning has great potential to further optimize field operations. Field operations should be done in a manner that minimizes time, travel over field surfaces and is coordinated with specific field operations, machine characteristics and topographical features of arable lands. To reach this goal, intelligent coverage path planning algorithm is key. This dissertation documents our innovative research in optimal field coverage path planning on both 2D and 3D surfaces. To determine the full coverage pattern of a given 2D planar field by using boustrophedon paths, it is necessary to know whether to and how to decompose a field into sub-regions and how to determine the travel direction within each sub-region. A geometric model was developed to represent this coverage path planning problem, and a path planning algorithm was developed based on this geometric model. The search mechanism of the algorithm was guided by a customized cost function resulting from the analysis of different headland turning types and implemented with a divide-and-conquer strategy. The complexity of the algorithm was analyzed, and methods for reducing the computational time were discussed. Field examples with complexity ranging from a simple convex shape to an irregular polygonal shape that has multiple obstacles within its interior were tested with this algorithm. The results were compared with other reported approaches or farmers\u27 actual driving patterns. These results indicated the proposed algorithm was effective in producing optimal field decomposition and coverage path direction in each sub-region. In real world, a great proportion of farms have rolling terrains, which have considerable influences to the design of coverage paths. Coverage path planning in 3D space has a great potential to further optimize field operations. To design optimal coverage paths on 3D terrain surfaces, there were five important steps: terrain modeling and representation, topography impacts analysis, terrain decomposition and classification, coverage cost analysis and the development of optimal path searching algorithm. Each of the topics was investigated in this dissertation research. The developed algorithms and methods were successfully implemented in software and tested with practical 3D terrain farm fields with various topographical features. Each field was decomposed into sub-regions based on terrain features. An optimal seed curve was found for each sub-region and parallel coverage paths were generated by offsetting the seed curve sideways until the whole sub-region was completely covered. Compared with the 2D planning results, the experimental results of 3D coverage path planning showed its superiority in reducing both headland turning cost and soil erosion cost

Modelling and path planning for additive manufacturing of continuous fiber composites

Material-extrusion based Additive Manufacturing (AM) is one of the leading (AM) technologies, which produces three-dimensional (3D) parts by extrusion of molten thermoplastic polymers layer by layer. However, its applications are limited due to the low strength and stiffness of the parts produced by this technology. One of the ways to improve the mechanical properties of the parts is to use a reinforced thermoplastic polymer with a filler such as chopped or continuous fibers. The resulting additively manufactured continuous fiber reinforced thermoplastic (CFRTP) composites could have superior mechanical properties and hence can be used in high-performance applications such as for aerospace and automotive industries. This thesis is divided into two sections. The first section is related to the modeling of additively manufactured continuous fiber composites for evaluation of the mechanical properties. The current studies for evaluating the mechanical properties of additively manufactured CFRTP composites are based on experimental results. Therefore, there is very limited study available to determine and optimize the process parameters. In this section, a finite element based study is presented to determine the effect of process parameters such as nozzle diameter, layer thickness, volume fraction and infill percentage on elastic properties of additively manufactured CFRTP composite structures. The second section presents the development of a continuous path planning algorithm for additive manufacturing of continuous fiber composites. The existing path planning algorithms used in material extrusion-based processes cause discontinuities in the material deposition if complex shapes are manufactured. Moreover, they cannot be used for continuous fiber composite printing, since the use of continuous fiber as a reinforcement requires continuous deposition of material throughout the printing process. In this thesis, a novel path planning algorithm has been developed to generate continuous deposition path for 3D printing of continuous fiber composites. The algorithm has been implemented for various complex geometries to generate continues deposition paths for the designed complex parts. The research conducted in this thesis can expand to the additive manufacturing of CFRTP composites with various reinforcing materials. The developed continuous path planning algorithm can be coupled with the optimized process parameters obtained from modeling results to produce v highly complex shape functional composite parts that could replace the conventional metal parts and processes by providing light-weight solutions for various industrial applications

Surface Partitioning in Automated CAD-Guided Tool Planning for Additive Manufacturing

Additive manufacturing processes such as spray coating, spray painting and rapid tooling are important steps in many products' life cycle. Robotic manipulators are widely adopted to carry out these processes. If done by human operators, the tool planning for these applications is usually time-consuming and the generated tool plans are prone to inaccuracy and errors. This research develops a fully-automated, CAD-guided tool planning system which eliminates the human involvement. Meanwhile, this system can generate optimized tool plans in the sense of robot motion performance. The critical part of this tool planning system is the partitioning of part surfaces into multiple easy-tohandle patches. In this paper, a decomposition-based approach is developed, which models the surface partitioning problem in geometric domain as an integer programming problem in algebraic domain. Experimental tests and evaluation carried out on automotive parts validate this new approach.Link_to_subscribed_fulltex