Rapid prototyping (RP) techniques are being increasingly used to manufacture injection molding and die casting core and cavity sets, known as tools, and for other tooling‐related parts, such as EDM electrodes. This paper presents a STL‐based finish machining technique for tools and parts made using RP techniques in order to achieve the tight tolerance and surface finish requirements necessary for tooling applications. Rotate, scale, translate and offset algorithms are used to pre‐process the 3D model prior to its manufacture. A machining strategy of adaptive raster milling of the surface, plus hole drilling and sharp edge contour machining, is developed to finish the parts and tools after fabrication using RP. Finally, a benchmark part was designed and fabricated using the above‐mentioned strategies and the results show the effectiveness of the developed software.
Purpose This paper presents a unique method to recognize circular holes from 3D models in the STL format. The topological information generated by this method enables identification of holes and tool path generation for holes which should be drilled rather than milled. Design/methodology/approach A method based on a set of developed algorithms is used to identify closed loops from a STL model, identify which closed loops correspond to cylindrical holes, find hole orientations, locations and diameters, and calculate the depth for the recognized holes. The developed procedure and algorithms have been implemented in Visual C++ to illustrate the efficacy of the method. Findings The implementation results showed that the developed algorithms can successfully recognize circular holes of differing sizes on both simple and complex surfaces, and in any orientation. Tool paths can thus be generated from STL models to more efficiently and accurately machine circular holes. Research limitations/implications The developed method requires that at least one simple closed loop exist for each potential hole. Originality/value A new and unique hole recognition method for use with STL models was developed. This method is useful for accurately and efficiently machining parts with circular holes from STL models as well as finish machining near‐net shape parts with circular holes created using rapid prototyping.
This paper presents a new 3D offset method for modifying CAD model data in the STL format. In this method, vertices, instead of facets, are offset. The magnitude and direction of each vertex offset is calculated using the weighted sum of the normals of the facets that are connected to each vertex. To facilitate the vertex offset calculation, topological information is generated from the collection of unordered triangular facets making up the STL file. A straightforward algorithm is used to calculate the vertex offset using the adjoining facet normals, as identified from the topological information. This newly developed technique can successfully generate inward or outward offsets for STL models. As with any offset methodology, this technique has benefits and drawbacks, which will be discussed in this paper. Finally, conclusions will be made regarding the applicability of the developed methodology.
Past research has shown that a composite material made up of zirconium diboride and copper (ZykronTM) when used as an electrode for electrical discharge machining (EDM) is superior to traditional EDM electrode materials. The Rapid Manufacturing Center at the University of Rhode Island is investigating the creation of geometrically complex Zyrkon electrodes using Selective Laser Sintering. The research approach and some details about Zyrkon will be explored in this paper, while the most recent developments of this research will be presented at the conference.
Purpose This paper presents an offset‐based tool path generation method for STL format three‐dimensional (3D) models. The created tool‐paths can be effectively used to near‐net‐shaped parts, in particular those created using rapid prototyping. Design/methodology/approach The STL model is first offset by the distance of the selected cutter radius using a unique 3D offset method. The intersections between the top facing triangles of the offset model and tool‐path drive planes are calculated. The intersection line segments are sorted, trimmed and linked to generate continuous top envelope curves, which represent interference‐free tool paths. Findings The developed offset‐based algorithm can rapidly and successfully generate interference‐free tool paths as continuous lines, instead of a collection of discrete tool location points. The strategy of using adaptive step‐over distances based on local geometrical information can significantly increase machining efficiency. Research limitations/implications The current tool path generation method only works for ball‐end mills. The entire surface of the STL model is treated as a single composite surface to be machined using raster milling. To improve machining efficiency, an automatic surface splitting algorithm could be developed to divide the model into several regions based on the characteristics of a group of triangular facets, and then machine these identified regions using different strategies and cutters. Originality/value The offset‐based tool‐path generation algorithm from STL models is a unique and novel development, which is useful in the rapid prototyping and computer‐aided machining areas.
As the key part of energy power equipment of turbine, aircraft engines and so on, blade has high requirement on profile accuracy and surface quality. The abrasive belt polishing technology can ensure the profile accuracy and higher surface quality of the blade surface, and improve the blade processing efficiency. In this paper, the abrasive belt polishing process was analyzed by simulating single abrasive grain belt polishing process. The model of abrasive belt grain was constructed. The plastic finite element method was used to simulate the single abrasive grain polishing process. The simulation processing was determined according to the characteristics of blade abrasive belt polishing. The polishing process under different polishing parameters was simulated, and the variation curves of polishing forces of single abrasive grain under different polishing parameters were obtained. Based on the developed hybrid polishing mach ine tool for blade finishing, a testing system for abrasive belt polishing force was built. Through polishing experiments, the influence rule of polishing parameters on the polishing force of abrasive belt is obtained, and the correctness of the simulation is verified by the consistency of the rule.
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