Rapid prototyping (RP) processes, classified as “time compression technologies”, are tools for realising physical models in short time and competitive costs. RP provides designers with the tools to rapidly generate an initial prototype directly from a CAD model. The weak points are the poor mechanical strength and the low surface finish of the produced parts. The Fused Deposition Modelling (FDM) RP process produces prototype parts out of ABS plastic: the model is exported to the RP machine software using the stereolithography (STL) format. The STL format is supported by most CAD systems and it reduces the part geometry to a polygonal 3D mesh, so that the part loses some resolution and the original geometry model is approximated with tolerances depending on the part orientation during the manufacturing process. The FDM process produces parts with unique characteristics that can be improved by an accurate choice of the main deposition (xy) plane. Dimensional tolerances may be better controlled on directions parallel to the xy plane; this has some implications on the proper choice of the part placemen. Also surface roughness can be controlled through a proper orientation of the part on the FDM machine. Furthermore it is necessary to take care of deposition orientation because of the resulting anisotropy of the mechanical strength. This paper presents a powerful tool to optimise the component desired features by acting on the part orientation during the FDM process. The optimization takes into account the employed support structure, the time employed for the deposition and the superficial roughness that can be reached by using, as design variables, the Euler angles of the body axes with respect to the FDM machine reference system. A Genetic Algorithm is used to perform the optimization. Two cases are considered: minimization of (i) the specific surface roughness or (ii) machine time needed to complete the part. Some examples are presented, concerning the realisation of parts having complex shape for a wind tunnel model.
Optimising Fused Deposition Modelling / Bagassi S.; Francia D.; Persiani F.. - ELETTRONICO. - (2009). (Intervento presentato al convegno Congreso Internacional Conjunto XXI Ingegraf - XVII ADM tenutosi a Lugo (Spain) nel 10-12 June 2009).
Optimising Fused Deposition Modelling
BAGASSI, SARA;FRANCIA, DANIELA;PERSIANI, FRANCO
2009
Abstract
Rapid prototyping (RP) processes, classified as “time compression technologies”, are tools for realising physical models in short time and competitive costs. RP provides designers with the tools to rapidly generate an initial prototype directly from a CAD model. The weak points are the poor mechanical strength and the low surface finish of the produced parts. The Fused Deposition Modelling (FDM) RP process produces prototype parts out of ABS plastic: the model is exported to the RP machine software using the stereolithography (STL) format. The STL format is supported by most CAD systems and it reduces the part geometry to a polygonal 3D mesh, so that the part loses some resolution and the original geometry model is approximated with tolerances depending on the part orientation during the manufacturing process. The FDM process produces parts with unique characteristics that can be improved by an accurate choice of the main deposition (xy) plane. Dimensional tolerances may be better controlled on directions parallel to the xy plane; this has some implications on the proper choice of the part placemen. Also surface roughness can be controlled through a proper orientation of the part on the FDM machine. Furthermore it is necessary to take care of deposition orientation because of the resulting anisotropy of the mechanical strength. This paper presents a powerful tool to optimise the component desired features by acting on the part orientation during the FDM process. The optimization takes into account the employed support structure, the time employed for the deposition and the superficial roughness that can be reached by using, as design variables, the Euler angles of the body axes with respect to the FDM machine reference system. A Genetic Algorithm is used to perform the optimization. Two cases are considered: minimization of (i) the specific surface roughness or (ii) machine time needed to complete the part. Some examples are presented, concerning the realisation of parts having complex shape for a wind tunnel model.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
