Parametric Computer-aided Design Model Research Articles

An adaptive B-spline representation of topology optimization design for Additive Manufacturing

Topology optimization is a renowned structural optimization approach used to compute the optimal topology for the enhancement of structural performance. It has been in common practice in different engineering fields such as automobile and aerospace. However, there still exist gaps between topology optimization and its engineering operations, which considerably impedes topology optimization’s applications. One of these gaps is how to make (especially finite element-based) topology optimization results machine-readable, which means, how to transform these into computer-aided design (CAD) models, which are ready-to-use models for manufacturing. In the proposed work the authors adopted a unique methodology that plugs the gap between topology optimization and manufacturing. This methodology seamlessly integrates the structural analysis tool, boundary description tool and standard CAD geometry representation; equipped with the Hausdorff distance approach for 3D printing/additive manufacturing of optimal structures. Initially, we extract the skeleton of the optimal design (in the form of a points cloud) using the level set method, followed by an interpolation technique with shape preservation property, the extracted skeleton is made dense. Incorporating the shape and curvature information of the data set, an adaptive B-spline approximation is devised for fitting a smooth curve through the points cloud. This approach interprets topology optimization results as a parametric CAD model with minimum possible control points and minimum approximation error. The CAD-based optimal designs are then used for additive manufacturing. The numerical results exhibit in detail the validity and accuracy of the proposed method.

A decision-support method for multi-parameter editing of parametric CAD models

Parametric modeling is a computer-aided design (CAD) paradigm where a design can be created by defining geometric constraints with parameters. In design change as well as design optimization, the design is often edited by modifying the values of relevant parameters. Without guidance on allowable parameter ranges that can guarantee the intrinsic solvability of the geometric constraint system, the user could assign improper values to the model’s parameters, which would further lead to a failure in model updating. However, current commercial CAD systems provide little support on such guidance. Existing methods, though able to compute allowable ranges for individual parameters, face difficulties in handling multi-parameter situations. To solve this problem, a systematic method is proposed, supporting decision-making in multi-parameter model editing by computing allowable parameter ranges. In the method, a set of variable parameters from the geometric constraint system are first selected by the user; these variable parameters are to be sequentially edited within several editing operations. Before each editing operation, 1D allowable ranges of the variable parameters are computed. By editing parameter values within the provided ranges, the solvability of the geometric constraint system can be guaranteed. The effectiveness and efficiency of the proposed approach is verified by several experimental results.

A reverse engineering approach for modeling of barely visible impact damage by combining results of non-destructive testing and numerical simulations

An evaluation of the structural residual life for composite elements affected by low-velocity impact loading is a challenging task due to the uncertainty of an influence of the resulting damage on the mechanical properties of a structure, which cannot be truly assessed without destructive testing. To overcome this deficiency, an approach based on reverse engineering was developed. Within this approach the results of non-destructive testing (NDT) are considered, namely the results of X-ray computed tomography as well as ultrasonic testing in B- and C-scan modes, for an evaluation of the geometrical properties of damage as well as the results of numerical simulations of impact testing of the composite were used to support the experimental results. Based on the obtained results, the generic shapes of barely visible impact damage (BVID) in composite structures were determined, and based on the generic shapes and the obtained relations between the damage extent and the impact energy, a parametric computer-aided design models were developed. The obtained models allow predicting the structural response, including the estimation of the residual life of composite structures in finite element simulation environments.

3D CAD model reconstruction and fast prototyping of rotational parts: a reverse engineering approach

PurposeThis paper aims to present a reverse engineering (RE) approach for three-dimensional (3D) model reconstruction and fast prototyping (FP) of broken chess pieces.Design/methodology/approachA case study involving a broken chess piece was selected to demonstrate the effectiveness of the proposed unconventional RE approach. Initially, a laser 3D scanner was used to acquire a (non-uniform rational B-spline) surface model of the object, which was then processed to develop a parametric computer aided design (CAD) model combined with geometric design and tolerancing (GD&T) technique for evaluation and then for FP of the part using a computer numerical controlled (CNC) machine.FindingsThe effectiveness of the proposed approach for reconstruction and FP of rotational parts was ascertained through a sample part. The study demonstrates non-contact data acquisition technologies such as 3D laser scanners together with RE systems can support to capture the entire part geometry that was broken/worn and developed quickly through the application of computer aided manufacturing principles and a CNC machine. The results indicate that design communication, customer involvement and FP can be efficiently accomplished by means of an integrated RE workflow combined with rapid product development tools and techniques.Originality/valueThis research established a RE approach for the acquisition of broken/worn part data and the development of parametric CAD models. Then, the developed 3D CAD model was inspected for accuracy by means of the GD&T approach and rapidly developed using a CNC machine. Further, the proposed RE led FP approach can provide solutions to similar industrial situations wherein agility in the product design and development process is necessary to produce physical samples and functional replacement parts for aging systems in a short turnaround time.

Novi metod za karakterizaciju parametarske rešetkaste strukture

Engineering designers often adapt their design structure to the needs of functional requirements independently of the capacity of the designed technical system to offer innovative capacities. Based on the notion of contradiction brought from TRIZ theory (Russian acronym for theory of inventive problem solving), we have developed an approach to reversely build a parametric intelligent structure potentially solving a wide range of inventive problematic situations. The proposed structure relies on an elastic buckling instability. A parametric CAD (Computer-Aided Design) model of the structure was carried out and its behavior is studied with finite element analysis (FEA), driven by a design of experiments (DoE). In this article, a specific method of characterization and multi-objective optimization of the structure is offered. Our objective is to bring a method to allow an engineering designer to solve rapidly and inventively his contradictory requirement in adapting it to the industrial application sought for.

Topologically robust CAD model generation for structural optimisation

Computer-aided design (CAD) models play a crucial role in the design, manufacturing and maintenance of products. Therefore, the mesh-based finite element descriptions common in structural optimisation must be first translated into CAD models. Currently, this can at best be performed semi-manually. We propose a fully automated and topologically accurate approach to synthesise a structurally-sound parametric CAD model from topology optimised finite element models. Our solution is to first convert the topology optimised structure into a spatial frame structure and then to regenerate it in a CAD system using standard constructive solid geometry (CSG) operations. The obtained parametric CAD models are compact, that is, have as few as possible geometric parameters, which makes them ideal for editing and further processing within a CAD system. The critical task of converting the topology optimised structure into an optimal spatial frame structure is accomplished in several steps. We first generate from the topology optimised voxel model a one-voxel-wide voxel chain model using a topology-preserving skeletonisation algorithm from digital topology. The weighted undirected graph defined by the voxel chain model yields a spatial frame structure after processing it with standard graph algorithms. Subsequently, we optimise the cross-sections and layout of the frame members to recover its optimality, which may have been compromised during the conversion process. At last, we generate the obtained frame structure in a CAD system by repeatedly combining primitive solids, like cylinders and spheres, using boolean operations. The resulting solid model is a boundary representation (B-Rep) consisting of trimmed non-uniform rational B-spline (NURBS) curves and surfaces.

Additively manufactured textiles and parametric modelling by generative algorithms in orthopaedic applications

PurposeThe purpose of this paper is to implement a new process aimed at the design and production of orthopaedic devices fully manufacturable by additive manufacturing (AM). In this context, the use of generative algorithms for parametric modelling of additively manufactured textiles (AMTs) also has been investigated, and new modelling solutions have been proposed.Design/methodology/approachA new method for the design of customised elbow orthoses has been implemented. In particular, to better customise the elbow orthosis, a generative algorithm for parametric modelling and creation of a flexible structure, typical of an AMT, has been developed.FindingsTo test the developed modelling algorithm, a case study based on the design and production of an elbow orthosis made by selective laser sintering was investigated. The obtained results have demonstrated that the implemented algorithm overcomes many drawbacks typical of the traditional computer aided design (CAD) modelling approaches. The parametric CAD model of the orthosis obtained through the new approach is characterised by a flexible structure with no deformations or mismatches and has been effectively used to produce the prototype through AM technologies.Originality/valueThe obtained results present innovative elements of originality in the CAD modelling sector, which can contribute to solving problems related to modelling for AM in different application fields.

In Silico Optimization of Femoral Fixator Position and Configuration by Parametric CAD Model.

Structural analysis, based on the finite element method, and structural optimization, can help surgery planning or decrease the probability of fixator failure during bone healing. Structural optimization implies the creation of many finite element model instances, usually built using a computer-aided design (CAD) model of the bone-fixator assembly. The three most important features of such CAD models are: parameterization, robustness and bidirectional associativity with finite elements (FE) models. Their significance increases with the increase in the complexity of the modeled fixator. The aim of this study was to define an automated procedure for the configuration and placement of fixators used in the treatment of long bone fractures. Automated and robust positioning of the selfdynamisable internal fixator on the femur was achieved and sensitivity analysis of fixator stress on the change of major design parameters was performed. The application of the proposed methodology is considered to be beneficial in the preparation of CAD models for automated structural optimization procedures used in long bone fixation.

A Realization Method for Transforming a Topology Optimization Design into Additive Manufacturing Structures

Topology optimization is a powerful design approach that is used to determine the optimal topology in order to obtain the desired functional performance. It has been widely used to improve structural performance in engineering fields such as in the aerospace and automobile industries. However, some gaps still exist between topology optimization and engineering application, which significantly hinder the application of topology optimization. One of these gaps is how to interpret topology results, especially those obtained using the density framework, into parametric computer-aided design (CAD) models that are ready for subsequent shape optimization and manufacturing. In this paper, a new method for interpreting topology optimization results into stereolithography (STL) models and parametric CAD models is proposed. First, we extract the skeleton of the topology optimization result in order to ensure shape preservation and use a filtering method to ensure characteristics preservation. After this process, the distribution of the nodes in the boundary of the topology optimization result is denser, which will benefit the subsequent curve fitting. Using the curvature and the derivative of curvature of the uniform B-spline curve, an adaptive B-spline fitting method is proposed in order to obtain a parametric CAD model with the fewest control points meeting the requirement of the fitting error. A case study is presented to provide a detailed description of the proposed method, and two more examples are shown to demonstrate the validity and versatility of the proposed method.

Functional design and optimisation of parametric CAD models in a knowledge-based PLM environment

The main purpose of this paper is to present our approach to automatically generating optimised 3D Computer-aided Design (CAD) models into which all the known expert design rules are integrated, by changing only functional requirements for the same product architecture. Through the requirement specifications integrated into our ACSP Product Lifecycle Management (PLM) system (functional and product architecture parameters), we are able to generate and automatically draft/produce/test/validate/optimise a parametric product architecture and its geometric skeleton, using a commercial CAD software program. A knowledge-based engineering software program, using constraint propagation with a first-order inference engine, and a multiobjective optimisation solver are used as an interface between the PLM system and the CAD software.

A Method for Automatic Generation of Parametric Computer Aided Design Models in a Mold Base e-Catalog System

Reusing existing design models and utilizing an e-Catalog for components are required for faster product development. For the acceleration, an e-Catalog should provide parametric computer aided design (CAD) models, since parametric information is necessary for configuration design. There are difficulties, however, in building a parametric library of all the necessary combinations using a CAD system, because there are too many component combinations for each product. To overcome this problem, we propose a table parametric method to generate parametric CAD models automatically, and describe its details.