Visualization Tools for Design Support in SFF 437

When considering the use of SFF, there are many questions a designer might ask. What model orientation should be used, will the model have adequate aesthetic and functional properties, is the STL file suitable for transfer to the SFF machine? These questions could be answered by a comprehensive design support system for SFF. This paper addresses a number of components for such a system that can be met through the use of visualization tools. These include: 1. Visualization of surface roughness 2. Visualization of characteristic features (e.g. surface macro-texture) 3. Visual simulation of fabrication Example applications of these tools are presented together with a status review of their implementation to date. It is envisaged that these tools will be incorporated into an already existing network-based preprocessor used for visualization, repair and slicing of STL files. The direction of future work is also discussed which will include the visual representation of functionally graded materials (connected with FEM results).Mechanical Engineerin

Computer-aided design of surface macro-textures for three dimensional printing

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1996.Includes bibliographical references (leaves 138-144by Haeseong Jee.Ph.D

Slicing STEP-based CAD Models for CAD/RP Interface

SFF technologies have an ability of creating a physical part directly .•. from its computer model by. adding material on a layer by layer basis. One of the problems lies in their current file fonnat for CAD data exchange. Current method using the de facto industry standard STL have at times resulted in problems such< as accuracy, redundancy, and integrity in its representing CAD models. In this paper we propose a method of slicing and editing STEP...based. RP models for the new data transfer paradigm between CAD systems and RPsystems using STEPMechanical Engineerin

3D Welding and Milling for Direct Prototyping of Metallic Parts

Welding has been used for the direct fabrication of metallic prototypes and prototype tools by several research institutes. Since welding alone is not able to deliver the accuracy and the surface quality needed for prototype tools, especially for injection molds, a combination with conventional machining is necessary. In this paper, welding and 5-axis milling are combined together for the direct fabrication of metallic parts. For welding, conventional CO2 arc welding is used. Test parts with conformal cooling channels an~ undercuts demonstrate the technological potential ofthis process combination for rapid tooling applications.Mechanical Engineerin

Surface Texture by 3D Printing

Three Dimensional Printing is a solid freeform fabrication process which creates parts directly from a computer model by depositing in layers. Each layer is created by depositing powder and selectively joining the powder with binder applied by a modulated ink-jet printhead. This paper explores the application of 3D Printing to the manufacture of surface textures, where the geometric freedom of 3D Printing is used to create repetitive millimeter and sub-millimeter surface structures with overhangs and undercuts. A related aspect of the work concerns the development of computer representations of these complex structures. In one investigation, a "mushroom field" surface texture was modeled and printed. Each mushroom consists of a cylinder with a ball on top. These features are printed in a hexagonal array with each feature parallel to the local surface normal of a complex curved surface. In another investigation, textures were printed into ceramic molds. The textures were transferred to metal (tin-lead, CoCr) castings as positive surface features with overhangs and undercuts and typical dimensions of 700 x 350 x 350Jlm. The application ofsuch cast textures to bone flXation in orthopaedic implants is discussed.Mechanical Engineerin

Robust fixture layout design for a product family assembled in a multistage reconfigurable line

Reconfigurable assembly systems enable a family of products to be assembled in a single system by adjusting and reconfiguring fixtures according to each product. The sharing of fixtures among different products impacts their robustness to fixture variation due to trade offs in fixture design (to allow the accommodation of the family in the single system) and to frequent reconfigurations. This paper proposes a methodology to achieve robustness of the fixture layout design through an optimal distribution of the locators in a multistation assembly system for a product family. This objective is accomplished by (1) the use of a multistation assembly process model for the product family, and (2) minimizing the combined sensitivity of the products to fixture variation. The optimization considers the feasibility of the locator layout by taking into account the constraints imposed by the different products and the processes (assembly sequence, data scheme, and reconfigurable tools' workspace). A case study where three products are assembled in four stations is presented. The sensitivity of the optimal layout was benchmarked against the ones obtained using dedicated assembly lines for each product. This comparison demonstrates that the proposed approach does not significantly sacrifice robustness while allowing the assembly of all products in a single reconfigurable line

IMECE2005-81651 TOLERANCE ANALYSIS CONSIDERING WELD DISTORTION BY USE OF PREGENERATED DATABASE

ABSTRACT A general and efficient methodology has been developed to analyze dimensional variations of an assembly, taking into account of the weld distortion. Weld distortion is generally probabilistic because of the random nature of welding parameters such as the welding speed, maximum welding temperature, ambient temperature, etc. The methodology is illustrated by a very simple example of two perpendicular plates fillet-welded to each other. Two steps comprise the methodology: establishment of a weld-distortion database, and tolerance analysis using the database. To establish the database, thermo-elasto-plastic finite element analyses are conducted to compute the weld distortion for all combinations of discrete values of major welding parameters. In the second step of tolerance analysis, the weld distortion retrieved from the database is used in addition to the dimensional tolerances of the parts. As a result of such an analysis, sensitivities of the assembly&apos;s dimensional variations to the part tolerances and weld distortion are obtained, which can be help improve the dimensional quality of the assembly