Reusability and Flexibility in Parametric Surface-based Models: A Review of Modelling Strategies (original) (raw)
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Parametric CAD modeling: An analysis of strategies for design reusability
Computer-Aided Design, 2016
CAD model quality in parametric design scenarios largely determines the level of flexibility and adaptability of a 3D model (how easy it is to alter the geometry) as well as its reusability (the ability to use existing geometry in other contexts and applications). In the context of mechanical CAD systems, the nature of the feature-based parametric modeling paradigm, which is based on parent-child interdependencies between features, allows a wide selection of approaches for creating a specific model. Despite the virtually unlimited range of possible strategies for modeling a part, only a small number of them can guarantee an appropriate internal structure which results in a truly reusable CAD model. In this paper, we present an analysis of formal CAD modeling strategies and best practices for history-based parametric design: Delphi's horizontal modeling, explicit reference modeling, and resilient modeling. Aspects considered in our study include the rationale to avoid the creation of unnecessary feature interdependencies, the sequence and selection criteria for those features, and the effects of parent/child relations on model alteration. We provide a comparative evaluation of these strategies in the form of a series of experiments using three industrial CAD models with different levels of complexity. We analyze the internal structure of the models and compare their robustness and flexibility when the geometry is modified. The results reveal significant advantages of formal modeling methodologies, particularly resilient techniques, over non-structured approaches as well as the unexpected problems of the horizontal strategy in numerous modeling situations.
CAD'20, 2020
Recent years have witnessed growing demands on product specifications as a result of increasing competition in worldwide markets. This puts pressure on companies to develop higher quality products with greater speed. Consequently, the work volume and the number of elements affecting the design process increases, alongside decreased working time. Existing CAD systems, which are based on parametric associative technology, have become indispensable tools to face this challenge. Today, these platforms are frequently used in design projects [17], because they help in the creation of parametric 3D models, collaboration between employees and work-teams, management of the entire product life-cycle, thus reducing time to launch. During part design, there are many possible modelling procedures in the solution space to generate any one part. Although the desired geometry is generated, not all models are reusable because the degree of reusability of the model depends on the procedure determined by the original designer [2]. Therefore, not all 3D models meet the designer's original expectations. In view of this, as reviewed by Cheng and Ma [5], the robustness and reusability of 3D models is key during downstream engineering activities, such as manufacturing, engineering analysis, and optimisation. To obtain fully parametrised and adaptive products during the product design phases, the overall strategy, modelling methods, established procedures and approaches are key considerations. For this reason, companies often create internal design guides [3] for the effective representation and communication of design intent between designers [4]. Part of this process involves collecting good modelling practices and reducing/simplifying the possible number of procedures for their implementation. Thus, the need for a modelling methodology becomes clear. Bodein et al. [1] analysed CAD systems in the automotive sector and defined five principal aspects for an efficient CAD strategy: to reduce design time in all design phases (conceptual, preliminary or detailed), to reuse existing CAD models and geometry, automatisation of routine design tasks based on knowledge-based engineering (KBE) applications, to enhance collaboration between designers, and to improve the general quality of CAD models. In addition, Bodein et al. [1] propose a road-map with five phases-namely, standardisation, methodology, generic modelling, expert rules and automation-to improve CAD efficiency. During a review of the literature, we identified that reusability in modelling methodologies is a neglected topic. Only one study was identified, that of Camba et al. [3], in which modelling methodologies were analysed and compared. Specifically, Camba et al. [3] analyse the three solid modelling methods. This study concludes why certain methods are easier to edit and contain fewer errors in 3D model regeneration. Nevertheless, the basis of CAD systems is classical solid-state or surface modelling [3],[4]. On the contrary, we have not identified any studies on surface modelling that provide a similar comparison to that of Camba et al. [3]. Such a comparison would help CAD designers identify which modelling methodology provides the greatest flexibility and reusability with regards to surface-based models.
International Journal of Technology and Design Education
In order to be reusable, history-based feature-based parametric CAD models must reliably allow for modifications while maintaining their original design intent. In this paper, we demonstrate that relations that fix the location of geometric entities relative to the reference system produce inflexible profiles that reduce model reusability. We present the results of an experiment where novice students and expert CAD users performed a series of modifications in different versions of the same 2D profile, each defined with an increasingly higher number of fix geometric constraints. Results show that the amount of fix constraints in a 2D profile correlates with the time required to complete reusability tasks, i.e., the higher the number of fix constraints in a 2D profile, the less flexible and adaptable the profile becomes to changes. In addition, a pilot software tool to automatically track this type of constraints was developed and tested. Results suggest that the detection of fix constraint overuse may result in a new metric to assess poor quality models with low reusability. The tool provides immediate feedback for preventing high semantic level quality errors, and assistance to CAD users. Finally, suggestions are introduced on how to convert fix constraints in 2D profiles into a negative metric of 3D model quality.
Functional surfaces as initial product design concept in 3D-CAD-Systems
2017
Finding an initial shape design for innovative product concepts is one of the most challenging and most creative parts in product design processes. To support design engineers during that particular phase, knowledge based design automation tools can be used. This paper proposes an enhancement of existing design methodologies in terms of initial shape design of innovative product concepts.The presented approach consolidates PLM and parametric 3D CAD technologies into one integrated method. A concept of parametric working surfaces as an institutionalized feature embedding product lifecycle knowledge is described and briefly demonstrated with a software example. The approach intends to support the product designer with additional information from different company departments as well as giving the designer a tool to explicitly declare the design intent of its design concept in the very early phase of geometric shape definition.
Flexible and robust CAD models for design automation
Advanced Engineering Informatics, 2012
This paper explores novel methodologies for enabling Multidisciplinary Design Optimization (MDO) of complex engineering products. To realize MDO, Knowledge Based Engineering (KBE) is adopted with the aim of achieving design reuse and automation. The aim of the ongoing research at Linköping University is to shift from manual modeling of disposable geometries to Computer Aided Design (CAD) automation by introducing generic high level geometry templates. Instead of repeatedly modeling similar instances of objects, engineers should be able to create more general models that can represent entire classes of objects. The proposed methodology enables utilization of commercial design tools, hence taking industrial feasibility into consideration. The concept of High Level CAD templates (HLCt) will be proposed and discussed as the building blocks of flexible and robust CAD models, which in turn enables high fidelity geometry in the MDO loop. Furthermore, quantification of the terms flexibility and robustness are presented, providing a means to measure the quality of the geometry models. Finally, application examples are presented in which the outlined framework is evaluated. The applications have been chosen from three ongoing research projects aimed at automating the design of transport aircraft, industrial robots, and micro air vehicles.
A Constraint Redundancy Elimination Strategy to Improve Design Reuse in Parametric Modeling
Computers in Industry, 2021
Strategies for design reuse play a fundamental role in the development of products that change and evolve over time. Design changes often involve modifications in the geometry of parts and assemblies, which are driven by changes in the digital representation of the product, i.e. the procedural and parametric CAD model. Consequently, constraint redundancies in the twodimensional profiles that build the parametric model can significantly hinder alterability and reusability. This paper argues that constraint redundancy conditions are not solely a computational problem but a more complex issue that involves the interaction with the sketch throughout the modeling process and the modeling scheme used to convey a specific design intent. We analyze a representative group of 3D MCAD systems and the interaction with their corresponding geometric kernels and Geometric Constraint Solvers (GCS) to determine how constraint redundancy is managed at the profile level. Next, we report the results of a series of experiments to evaluate the influence of redundant constraints on model editing and reusability tasks and describe the development of a new software tool for identifying and parsing constraint redundancy conditions. We conclude that constraint redundancy in profiles significantly and unnecessarily compromises model conciseness, robustness, and the overall model quality, which negatively affects user productivity and downstream processes. The implications of constraint redundancy conditions for CAD training are emphasized. Our experiments also demonstrate the value of our parsing tool to assist users in maximizing model reuse (by removing redundancies) and the communication of design intent (by proposing an optimal set of non-redundant constraints), but further development is necessary to use it as a practical tool for engineering analysis.
Creating Complex CAD Models with Freeform Surfaces
Springer tracts in mechanical engineering, 2018
Using a combination of surfaces and their transformations, one advantage of surface modelling is the ability to be able to create such CAD geometries that would not be possible only by combining the basic features of solid modelling. Using the example of a mass-market product-a hand blender-a number of procedures for working with surfaces are presented that can lead to a final target shape. Choosing a particular step depends on the functional and technical views, as well as the mathematical rules of CAD surface modelling. The choice of the model is not random, as modelling end products for mass-market products belongs to the most demanding design tasks, as it requires fulfilling a variety of working and design functions, many compromises, a great deal of experience and work, all at the same time. Here, it is important to understand the logical, mathematical properties of curves, surfaces and operations for working with them. Thus, this chapter brings the theory from the first chapter of this book into practice.
Function Model Based Generation of CAD Model Variants
CAD'20, 2020
A product is an artefact which fulls a specic function. However, most design automation (DA) approaches wich are used to generate multiple alternative design concepts focus on the generation of CAD models. These neglect to represent the functional aspects of the product, and are furthermore deemed too rigid for the introductino of novel solutions. Pure function modellingappraoches on the other hand provides methods such as design rationale representation, introduction of novel solutions or instantiation of combinatorial alternative concepts, but the resulting models are insucient for analysis. To alleviate this, a design space exploration (DSE) approach which couples function modelling and CAD is presented. The approachlinks the product's design rationale modelled in enhanced functionmeans (EF-M) to a DA approach via the here introduced object model for function and geometry (OMFG). The resulting method is able to automatically generate CAD models of alternative concepts based on combinations of alternative design solutions dened in the function model. The approach is presented through a case study of an aircraft engine component. Sixteen dierent concepts are generated based on four functions with alternative solutions. In an initial computation of the eort to generate all alternative concepts, the DA aspect of the approach's eort pays o as soon as ve functions have two or more alternative solutions. Beyond the benet of ecient instantiation of CAD models of alternative product concepts, the approach promises to provide the design rationale behind each concept, and thereby a more systematic way of exploring and evaluating alternative design concepts.
Functional modeling in parametric CAD systems
2004
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