Assembly sequence influence on geometric deviations propagation of compliant parts (original) (raw)
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Variation Analysis of Compliant Assemblies: A Comparative Study of a Multi-Station Assembly
Predicting the final shape variation of single and multi-station assemblies of compliant parts is a strategic topic especially in automotive and aeronautic industries for the wide-spread presence of sheetmetal assembly processes. The high flexibility of compliant parts causes wide final shape variations during the assembly process. Therefore, it is strategic to analyze different assembly configurations at the beginning of the design phase. Starting from the recent methodology proposed by the same authors in a previous paper to do tolerance/variation analysis of compliant assemblies in single- and multi-station configurations, the developed MATLAB-based tool, called SVA-FEA (Statistical Variation Analysis & Finite Element Analysis), is here briefly illustrated. SVA-FEA allows to pre-process FE models, imported from MSC.Patran® or HyperMesh®, defining input deviations and output variables, and including contacts between parts. Then, the results obtained with a linearization process by...
Variation Analysis of Compliant Assemblies: a comparative study of a single-station assembly
Predicting the final shape variation of single and multi-station assemblies of compliant parts is a strategic topic especially in automotive and aeronautic industries for the wide-spread presence of sheetmetal assembly processes. The high flexibility of compliant parts causes wide final shape variations during the assembly process. Therefore, it is strategic to analyze different assembly configurations at the beginning of the design phase. Starting from the recent methodology proposed by the same authors in a previous paper to do tolerance/variation analysis of compliant assemblies in single- and multi-station configurations, the developed MATLAB-based tool, called SVA-FEA (Statistical Variation Analysis & Finite Element Analysis), is here briefly illustrated. SVA-FEA allows to pre-process FE models, imported from MSC.Patran® or HyperMesh®, defining input deviations and output variables, and including contacts between parts. Then, the results obtained with a linearization process by...
The International Journal of Advanced Manufacturing Technology, 2020
One of the most critical tasks within the scope of Design for Manufacturing (DfM) is to define the set of Geometrical Product Specifications (GPS) in the 3D model or in the engineering drawing that ensures the functionality and the interchangeability of parts, as well as the intended functional performance of an assembly. Several methodologies have been proposed for the optimal designation of such specifications; however, the majority of them do not effectively take into account the deformations that are inevitably induced during assembly and operation for the vast majority of mechanical components. Motivated by the widely accepted tolerancing practice for sheet metal parts in the automotive industry, where the distinction between free state and constrained state is considered, the paper investigates the influence of the deformations induced during assembly and operation on GPS. The effect of part stiffness in the resultant functional GPS of the assembly/component is explored, through CAD surfacing and non-linear numerical finite element analysis tools including the contact problem. The current stage of development of a novel, performance-based methodology for the GD&T design procedure is presented. The methodology is applied on a realworld mechanical assembly that is derived from tolerance stack up-related literature. This study illustrated is that for an unpredictably wide range of mechanical components the default, free-state GPS scheme should only be assigned after rigorous analysis of their compliance behaviour. The proposed approach will lead to deduce the correlation between production cost and performance through a further development in future study.
Including geometric feature variations in tolerance analysis of mechanical assemblies
IIE transactions, 1996
Geometric feature variations are the result of variations in the shape, orientation or location of part features as defined in ANSI Y14.5M-1982 tolerance standard [ANSI 1982]. When such feature variations occur on the mating surfaces between components of an assembly, they affect the variation of the completed assembly. The geometric feature variations accumulate statistically and propagate kinematically in a similar manner to the dimensional variations of the components in the assembly.
Procedia Manufacturing
Mathematical models for tolerance representation are used to assess how the geometrical variation of a specific component feature propagates along the assembly, so that tolerance analysis in assemblies can be carried out using a specific tolerance propagation method. Several methods for tolerance analysis have been proposed in the literature, being some of them implemented in CAD systems. All these methods require modelling the geometrical variations of the component surfaces: parametric models, variational models, DoF models, etc. One of the most commonly used models is the DoF model, which is employed in a number of tolerance analysis methods: Small Displacement Torsor (SDT), Technologically and Topologically Related Surfaces (TTRS), Matrix Transformation, Unified Jacobian-Torsor model. However, none of the DoF-based tolerance analysis methods incorporates the effect of form deviations. Among the non DoF-based methods, there are two that include form tolerances: the Vector Loop or Kinematic method and the Tolerance Map (T-Map) model, although the latter is still under development. In this work, a proposal to incorporate form deviations into the matrix transformation method for tolerance analysis in assemblies is developed using a geometrical variation model based on the DoF model. The proposal is evaluated applying it to a 2D case study with components that only have flat surfaces, but the proposal can be extrapolated to 3D cases.
Integration of tolerances in the mechanical product process: Assembly with defects modelling
2013
a. Mechanical Engineering Laboratory, National Engineering School of Monastir, Monastir University, Av. Ibn Eljazzar, 5019 Monastir, Tunisia. a, b. LIPPS, ETS, 1100, Notre-Dame Ouest, Montreal, H3C1K3, Quebec, Canada. Borhen.louhichi@etsmtl.ca, abdelmajid.benamara@enim.rnu.tn Abstract: The part and assembly requirements are specified by the tolerances. In the Digital Mock-Up (DMU), the product is designed on nominal configuration and the tolerances are formally allocated to the CAD model. Thus, the impacts of the tolerance stack-up on the advanced phase of the product design (Dynamic computation, F.E Analysis...) are neglected. The DMU improvement requires the tolerance integration in CAD model. A developed model allows obtaining the components with defects according to dimensional and geometrical tolerances specified in the nominal model. In CAD model, the assembly of the components with dimensional and geometrical defects requires the updating of the assembly mating constraints. T...
Sheet metal parts are widespread used in the assembly of product such as automotive and airframes bodies. This paper presents how Dimensional Engineering (DE) process and the simulation-based tolerance analysis used in the development process of the assembly tolerance analysis. Focusing on the sheet metal component, which should be treated as non-rigid part, compliant assembly analyzing is adopted in the simulation process. Deviations of the components due to the tolerance between pin locator and hole and the locator layout scheme are defined as the key point characteristics (KPCs) during the optimization process. Inspection data incorporated close-loop optimizing approaches is applied to the final deviation estimation in simulation. Dimensional engineering software solution, 3DCS, is used as the analyzing tool in the case study
Integrated Tolerance and Fixture Layout Design for Compliant Sheet Metal Assemblies
Applied Sciences
Part tolerances and fixture layouts are two pivotal factors in the geometrical quality of a compliant assembly. The independent design and optimization of these factors for compliant assemblies have been thoroughly studied. However, this paper presents the dependency of these factors and, consequently, the demand for an integrated design of them. A method is developed in order to address this issue by utilizing compliant variation simulation tools and evolutionary optimization algorithms. Thereby, integrated and non-integrated optimization of the tolerances and fixture layouts are conducted for an industrial sample case. The objective of this optimization is defined as minimizing the production cost while fulfilling the geometrical requirements. The results evidence the superiority of the integrated approach to the non-integrated in terms of the production cost and geometrical quality of the assemblies.
International Journal of Advanced Manufacturing Technology, 2010
In this paper, a general methodology to do tolerance analysis of rigid assemblies is proposed. Firstly, tolerance specification sets, according to GD&T or ISO specifications, are translated into variational features by using 4 × 4 homogenous transformation matrices. In particular, planar and cylindrical features are considered. Then, once all variational features are modeled, assembly constraints among parts are introduced. To solve assembly constraints, an assembly transformation matrix is evaluated. By using point, line, and plane entities and their combinations, kinematic joints are modeled. A numerical procedure is proposed to solve fully and over-constrained assemblies. The best-fit alignment among variational mating features is performed by using optimization algorithms. The proposed method for tolerance analysis of rigid part assemblies allows to simulate different assembly sequences. Finally, in order to show the effectiveness of the proposed methodology, three case studies are described and analyzed.