Multi-criteria retrieval of CAD assembly models

Being able to reuse existing design knowledge is of major interest to help designers during the creation of new products. This is true at the level of the parts and even more at the level of the assemblies of multiple parts. Meaningful information and knowledge can be extracted from existing geometric models and associated data and metadata, as well as from the processes followed to define them. This paper proposes a method to characterize and structure CAD assembly models to enable the retrieving of similar models from a database. A framework has been devised for the retrieval of globally and/or partially similar assembly models according to multiple user-specified search criteria. It is based on an assembly descriptor, called the Enriched Assembly Model, which is an attributed graph that encodes all the required data automatically extracted from the geometry and structure of the CAD models. The data are organized in four layers: structural, assembly interface, shape and statistic layers. Starting from a real CAD model or from an abstract query model, the algorithm retrieves models from the database by solving a matching problem. The matching between two assembly models is translated into the problem of finding a sub-isomorphism between two EAMs. The layered organization of the EAM allows partially defined queries, which can be further refined. The effectiveness of the proposed approach is illustrated with results obtained from the developed software prototype

A 3D CAD assembly benchmark

Evaluating the effectiveness of the systems for the retrieval of 3D assembly models is not trivial. CAD assembly models can be considered similar according to different criteria and at different levels (i.e. globally or partially). Indeed, besides the shape criterion, CAD assembly models have further characteristic elements, such as the mutual position of parts, or the type of connecting joint. Thus, when retrieving 3D models, these characteristics can match in the entire model (globally) or just in local subparts (partially). The available 3D model repositories do not include complex CAD assembly models and, generally, they are suitable to evaluate one characteristic at a time and neglecting important properties in the evaluation of assembly similarity. In this paper, we present a benchmark for the evaluation of content-retrieval systems of 3D assembly models. A crucial feature of this benchmark regards its ability to consider the various aspects characterizing the models of mechanical assemblies

Using a Smart Recognition Framework for the Automated Transfer of Structural Whole Engine Models

The development of adequate simulation models from geometric CAD assemblies is one of the most important tasks in early design phases. With this step requiring a lot of manual effort, the desire for a process efficiency improvement via an automated solution rises. In order to derive information about the assembly to build Finite-Element (FE) models, various different steps have to be taken which require visual assessment and engineering evaluation, knowledge and judgement. The approach described in this research mimics the engineer's logic and way of thinking to automate these steps. Thereof, the recognition of entities plays a fundamental role for further processing. To achieve the desired recognition, methods have been developed to retrieve criteria like form, function, context and positioning from the available geometry data. The developed recognition framework supports and provides a component categorization so that specifically optimized process chains for each category can be implemented, depicting a more robust and reasonable overall process