Search Results

Mechanical assemblies are subject to dimensional and functional constraints in order that they fit and function properly at higher level assemblies. Their final tolerated dimensions, which must comply with the cited constraints, are composed by the chain dimensioning of the tolerated dimensions of their components. Therefore, the tolerances of each individual component play an important role on the fit and functional requirements in a product and must be properly specified for this intent. However, the origin for each part dimensioning - the datum referencing - is of vital importance for the correct tolerance accumulation of the assembly components.

The Market demand for even better quality products with regard to important features, like greater reliability and reduced noise, requires the specification of stringent dimensional and form design tolerances. This trend is leading designers to specify closer fits between mechanical components, with consequent impact in the product manufacturing costs. As assemblies are composed by several components subject to specific individual tolerances, a recurring problem raised in all mechanical design is the one of specifying components tolerances what are both feasible concerning the cost competent production processes regarding different suppliers and comply, when considered along the chain dimensioning, with the final accumulated tolerance required for the assembly. In this work this matter is addressed and an optimization solution is proposed.

The adequate dimensioning and specification of tolerances in the design phase of a product is of fundamental importance for a successful integration among several processes related in its production: design, process planning and manufacturing. This work describes some current concerns regarding interpretation of location tolerances and application of concurrent engineering between suppliers and customers in the design phase of a product and proposes a procedure to attempt dealing with these issues. The concepts of functional features specification between connected components and chain dimensioning along an assembly are both addressed.

This work deals with the problem of minimizing the waste of space of a placement of a set of two-dimensional objects inside a two-dimensional container. We address this problem with a heuristic approach based on simulated annealing, which is a probabilistic heuristic inspired on the physico-chemical processes that take place during the recrystalisation of a metal. We avoid the traditional “external penalisation” approach by applying the Minkowski sum algorithm from computational geometry to determinate collision-free regions inside the container to place an item. This gives a more universal character to the proposed algorithm, as external penalisation relies on arbitrary parameters that affect greatly the performance of the optimisation algorithm. Our algorithm is suited to non-convex items and non-convex containers, and it can be easily adapted to related problems, such as minimizing the dimensions of the container.

The objective of this paper is to show how viable is the use of solar energy, which is accomplished by the optimal utilisation of energy in a solar racing vehicle, which is in turn achieved by optimising its energy management via racing strategy. Simulated Annealing is an optimisation process that is suited for large, multivariable, combinatorial optimisation problems such as this one: finding an optimal racing strategy, using the best way possible the energy converted by the photovoltaic panel. Based on instantaneous inputs, Simulated Annealing calculates the instantaneous velocity that allows the vehicle to proceed as fast as possible.

Based on a 3D model generated in a CAD system, a rapid prototyping system can manufacture a prototype in few hours. The most common techniques for rapid prototyping use materials like resins and polymers. The difference between the material of the manufactured prototype and the real piece makes the realization of some tests with the prototype almost impossible, such as analysis of mechanical and chemical resistance. This work proposes a technique to make a prototype by machining it using a 3D machine. The great part of the industrial machining can be realized using 2½D machining. Some authors proposed methods to machine the sculptured surfaces in a 2½D machining; however, the surface finishing, depending of the application, is not so good. We proposed an algorithm capable of generating the toolpath for a 3D machining to attend this demand.

Solid Modeling and Geometric Modeling are fields of research that grew separately. However, the technological necessity is pressuring in a direction such that both technologies are going to fuse in only one. In this paper we discuss how this fusion can be possible. The basic concepts are the same; however, the geometrical information (curves and surfaces) will be understood as an attribute of the topological primitives (face, edge and vertex). Through this approach it will be possible to have a polyhedral representation when necessary (for example, visualization and mass property calculation algorithms) and to have the curved representation when necessary. It was noticed that the solid represented according curved representation spends less memory.