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Recent advancements in means of data collection and utilization have stepped forward to the realization of model-based definition approaches in product and production development processes. This realization is further facilitated by the presentation of open-source standards for model-based definition including STEP AP 242 and QIF 3.0. As a result, engineers are empowered with a significant amount of data to improve the development processes, particularly the tolerancing and metrology processes. This paper evaluates the opportunities enabled in the era of tolerance analyses, particularly computer-aided tolerance analyses by model-based design approaches particularly through the utilization of STEP AP 242 and QIF 3.0 standards. The main breakthrough in these standards is the semantic representation of tolerancing data in the models. However, the existing methods of modeling and analyzing tolerance information are diverse and not all these methods can utilize the new standards in the same manner. The potential usages of the new standards in different tolerance modeling techniques are reviewed. Furthermore, the research gaps and wishes for further improvements in the tolerance analysis era through model-based definition are discussed. [ABSTRACT FROM AUTHOR]

Traditional computer aided tolerancing method could not accomplish the tolerancing and variation simulation well in composite assembly. The paper presents a clamping force integrated computer aided tolerancing method for composite assembly. The stochastic variations and the stackup of variations are affected by clamping forces. The clamping force modified probability distribution is used to represent the modification based on the verified FEA model of the composite assembly. The clamping forces are coordinated based on the main deformation mode extracted by the principal component analysis to satisfy the coaxial tolerance requirements of the composite assembly. The assembly of an aircraft composite elevator is considered to illustrate the computational aspects of the proposed methods. The computer aided tolerancing method involving clamping forces outlined in the paper is found to be effective for composite assembly. [ABSTRACT FROM AUTHOR]

Consideration of form errors involves real machining features in tolerance modeling but increases uncertainties in functional requirement estimation, when tackling the trade-off between the cost and precision performance. In this paper, a statistical tolerance allocation method is presented to solve this problem. First of all, a top-down stepwise designing procedure is designed for complex products, and a combination of Jacobian matrix and Skin Model Shapes is applied in modeling the mechanical joints. Then, rigid assembly simulations of point-based surfaces are further advanced to provide an accurate estimation of the assembly state, through considering physical constraints and termination conditions. A mini-batch gradient descent method and a backtracking strategy are also proposed to promote computational efficiency. Finally, a deep Q-network is implemented in optimal computation after characterizing the systematic state, action domain, and reward function. The general tolerance scheme is then achieved using the trained Q-network. The results of 6 experiments each with 200 samples show the proposed method is capable of assessing tolerance schemes with 35.2% and 47.2% lower manufacturing costs and 16.7% and 28.3% higher precision maintenance on average than conventional particle swarm optimization and Monte Carlo method respectively. [ABSTRACT FROM AUTHOR]

Dimensional and geometric tolerances affect both the cost and the functionality of a given product. Finding the acceptable trade-off between the two is among the common engineering tasks. Thus, many tolerance analysis methods are developed to help engineers and assist in the decision-making process. In this article, the authors have assessed four tolerance analysis methods by applying them to the open-loop assembly. The results obtained by the tolerance chart (worst-case) method, Monte-Carlo simulation, vector-loop analysis, and the Unified Jacobian-torsor model were analysed and compared. Additionally, the overview and application guidelines are included for each of the methods, aiming to help both researchers and practitioners. The results have confirmed that there are significant variations in the outputs across the observed methods, implying the need for informed method selection. [ABSTRACT FROM AUTHOR]

Abstract In the aeronautic field, the required accuracy of finished parts is difficult to achieve with the best value for money. It is necessary to simulate the impact of manufacturing deviations in order to verify that the manufacturing process meets the requirements in spite of dispersions in each phase. With support of research works from LURPA ENS Cachan University Paris-Sud and software engineering from DPS, Safran Aircraft Engines has developed a Manufacturing Computer Aided Tolerancing Software that aims to automatize the manufacturing specification transfer and optimize the manufacturing tolerances. This software uses input from the model based definition and from the tolerancing analysis performed by ANATOLE 3D (software edited by AIRBUS and DPS). [ABSTRACT FROM AUTHOR]

More and more research works on assembly tolerance simulation is considering not only orientation and position deviations, but also form errors. In this paper, we describe a process to generate skin model shapes, i.e. 3D models with form error, from the CAD model of a part. We study several different methods used for generating discrete models with defects, and these methods are applied to an identical CAD model to point out their differences. The work will be of benefit for choosing and applying of these different generation approaches, and for automating the generation of skin model shapes. [ABSTRACT FROM AUTHOR]

Non-rigid components assembly simulation requires complex and difficult modelling tasks. This paper presents how ANATOLEFLEX solution can support user to take into account assembly sequence, joint with defaults, composite or metallic material properties, form default from manufacturing processes, and contact modelling in order to build a full and realistic assembly simulation. An implementation of this solution is presented on a representative aeronautical structural assembly use case with simulation results analysis. This use case illustration leads to conclusions on future industrial applications of realistic assembly simulations such as tolerance analysis or gap maps estimation for shimming processes. [ABSTRACT FROM AUTHOR]

When talking about a large batch production of a certain mechanical product it generally comes along with specific requirements in terms of dimensional management to guarantee a consistently high product quality ensuring that customer requirements are met. Therefore, this contribution is about the effect that the elasticity of the observed assembly has on the formation of the limiting positions of the considered key product characteristics arising from tolerance analysis. On the example of an automotive door assembly a developed approach based on existing methodologies is explained in detail containing CAT and FEM simulations. [ABSTRACT FROM AUTHOR]

The recent attempt in Geometrical Product Specification to change from dimensional to geometrical tolerancing leads to a stronger focus on datum systems. Two aspects on the requirements for these and their effects on each other will therefore be discussed in this paper. A new approach to develop a functional datum system in the early stages of the methodical design process that is derived from the functional interaction of the indeterminate workpiece geometry within the outlined assembly group will be explained. It will also show current research results to overcome the gaps in ISO 5459 about extraction and association requirements for the verification process. [ABSTRACT FROM AUTHOR]

A simulation of tolerance analysis in assemblies using Sigmund Computer Aided Tolerancing (CAT) software is validated through the example of an automobile locking device. Simulation with CAT, applying criteria on both the statistical distribution and the rivet pin position in the hole used in the example, will allow us to predict the functional dimension tolerances in these assemblies with greater accuracy in the preliminary design phase. These tolerances will subsequently define the manufacturing specifications. The statistical distribution, in the example, that best fits the overall set of tolerances, is the triangular distribution followed by the normal distribution; the position of the rivet pin axis in its hole is off-centre by 53 % with regard to its maximum value. [ABSTRACT FROM AUTHOR]

One of the most common uses for Computer Aided Tolerancing (CAT) in the passenger car industry is body design, which universalized, consists of non-rigid assembly processes. There are a number of theoretical approaches to model the joining behavior of assemblies with elastic FEM approaches combined with statistical computation. On the other hand the rising complexity of today's body-in-white production chain makes simplifications inevitable when fast results for tolerance optimization are required. Multiple use-cases representing different scenarios are analyzed. The scenarios vary in the stiffness of the involved components, the joining environment and the general geometrical set-up. Comparing mass production measurement data with simulation output reveals the limits of CAT simulations in certain cases. One of those cases is where so-called geo-stations improve the dimensional output quality of assemblies compared to the single parts. To account for this phenomenon an adaptive approach to model geo-stations in different ways is presented, i.e. as an entity either provoking an additional influence of deviation or supplying geometrical correction. A matrix is used to suggest the appropriate kind of modeling depending on the deduced parameters. [ABSTRACT FROM AUTHOR]

Abstract: Geometric deviations are inevitably observable on manufactured workpieces and have huge influences on the quality and function of mechanical products. Therefore, many activities in geometric variations management have to be performed to ensure the product function despite the presence of these deviations. Dimensional and Geometrical Product Specification and Verification (GPS) are standards for the description of workpieces. Their lately revision grounds on GeoSpelling, which is a univocal language for geometric product specification and verification and aims at providing a common understanding of geometric specifications in design, manufacturing, and inspection. The Skin Model concept is a basic concept within GeoSpelling and is an abstract model of the physical interface between a workpiece and its environment. In contrast to this understanding, established models for computer-aided modelling and engineering simulations make severe assumptions about the workpiece surface. Therefore, this paper deals with operationalizing the Skin Model concept in discrete geometry for the use in geometric variations management. For this purpose, Skin Model Shapes, which are particular Skin Model representatives from a simulation perspective, are generated. In this regard, a Skin Model Shape is a specific outcome of the conceptual Skin Model and comprises deviations from manufacturing and assembly. The process for generating Skin Model Shapes is split into a prediction and an observation stage with respect to the available information and knowledge about expected geometric deviations. Moreover, applications for these Skin Model Shapes in the context of mechanical engineering are given. [Copyright &y& Elsevier]

The present paper deals with the manufacturing process of a railway carriage. In the first part of the paper, the authors focus on a “virtual railway factory” that uses a very innovative assembly cycle, if compared to the traditional manufacturing processes in the railway field. The case study refers to a railway carriage consisting of four modules, that are singularly set up of furnishings and other systems in dedicated workplaces. On one hand, the virtual simulation has highlighted several critical aspects to be improved, in order to achieve a greater feasibility and to reduce time and cost. On the other hand, the designers have been able to evaluate the movements of the parts and the assembly sequences of the components, by considering each geometric, functional and technological constraint and also some safety requirements. The second part of the paper deals with the simulation of the assembling operations and the analysis of tolerance chains, which have been performed through a Computer Aided Tolerancing system. In particular, the precision requirements have been also evaluated and we have compared the accumulation of dimensional and geometric deviations when using both rivets and traditional welds to fasten the modules. [ABSTRACT FROM AUTHOR]

We present in this paper an optimization algorithm based in Taguchi gradient method for statistical synthesis of tolerances, adapted to be integrated in Computer Aided Tolerancing systems. Because the analysis and the synthesis of the dimensional and geometrical tolerances are two significant tools in the simulation of the product life cycle, the algorithm for optimisation of the tolerances and calculation of performances criteria such as loss of quality, costs total function of acceptance, were developed and implemented under Matlab™. The precision and the simplicity of this algorithm compared to others (finite differences, soft-computing) were highlighted using a comparative study on a published assembly case. [ABSTRACT FROM AUTHOR]