Andrea Corrado

Geometric tolerance analysis through Jacobian model for rigid assemblies with translational deviations

Purpose – The purpose of this paper is to carry out a tolerance analysis with geometric tolerances by means of the Jacobian model. Tolerance analysis is an important task to design and to manufacture high-precision mechanical assemblies; it has received considerable attention by the literature. The Jacobian model is one of the methods proposed by the literature for tolerance analysis. The Jacobian model cannot deal with geometric tolerances for mechanical assemblies. The geometric tolerances may not be neglected for assemblies, as they significantly influence their functional requirements. Design/methodology/approach – This paper presents how it is possible to deal with geometric tolerances when a tolerance analysis is carried out by means of a Jacobian model for a 2D and 3D assemblies for which the geometric tolerances applied to the components involve only translational deviations. The three proposed approaches modify the expression of the stack-up function to overcome the shortage of Jacobian model tha...

Assembly design in aeronautic field: From assembly jigs to tolerance analysis

Tolerance analysis represents the best way to solve assembly problems in order to improve the quality and to reduce the costs. It is a critical step to design and to build a product such as an aircraft and its importance is grown up in the past years. This work presents a method for the tolerance analysis of an assembly involving free-form surfaces with large dimensions. The assembly is a tail beam, a structural component of an aircraft that is constituted by five parts of large dimensions. The influence of the tolerances applied to the five components of the tail beam on the value of the gap at the interfaces among the parts has been deeply investigated. A set of control points have been distributed on the free-form surfaces of the tail beam; its number and its distribution have been opportunely designed. Moreover, the influence of the tolerances on the other requirements of the tail beam connected with the motion drive has been studied. Tolerance analysis has involved the choice of the assembly tools and sequence too. The assembly jigs are mated with the assembly components through pins that are inserted into tooling holes located on the assembly components. The fit conditions have been modeled and the tolerances of the tooling hole have been opportunely chosen. Each tolerance of the tail beam components has been modeled by means of a probability density function. Monte Carlo approach has been used to obtain the statistical distribution of the assembly requirements, once dimensions and geometry of the tail beam components have been perturbed inside the tolerance ranges. Monte Carlo simulation has been carried out by a well-known computer-aided tolerance software, eM-Tolmate of UGS®.

A variational model for 3D tolerance analysis with manufacturing signature and operating conditions

Purpose The purpose of this work is to present a variational model able to deal with form tolerances and assembly conditions. The variational model is one of the methods proposed in literature for tolerance analysis, but it cannot deal with form tolerances and assembly conditions that may influence the functional requirements of mechanical assemblies. Design/methodology/approach This work shows how to manage the actual surfaces generated by the manufacturing process and the operating conditions inside the variational model that has been modified to integrate the manufacturing signature left on the surfaces of the parts and the operating conditions that arise during an actual assembly, such as gravity and friction. Moreover, a geometrical model was developed to numerically simulate what happens in a real assembly process and to give a reference value. Findings The new variational model was applied to a three-dimensional case study. The obtained results were compared to those of the geometrical model and to those of the variational model to validate the new model and to show the improvements. Research limitations/implications The proposed approach may be extended to other models of literature. However, its limitation is that it is able to deal with a sphere–plane contact. Practical implications Tolerance analysis is a valid tool to foresee geometric interferences among the components of an assembly before getting the physical assembly. It involves a decrease in the manufacturing costs. Originality/value The main contributions of the study are the insertion of a systematic pattern characterizing the features manufactured by a process, assembly operating conditions and development of a geometrical model to reproduce what happens in a real assembly process.

Computer-Aided Techniques for Geometry Assurance

Geometry assurance can be described as a number of activities, all contributing to minimize the effect of geometrical variation in a final product. This work aims to introduce a new type of comparison between a computer-aided technique for geometry assurance and some models proposed by the literature. In particular, the aim of this work is to solve, through a computer-aided technique, some case studies that were already solved by different methods of the literature. The different case studies that have been introduced and solved in this paper aim to highlight the potentialities and the limits in using a computer-aided technique for geometry assurance. Because this type of comparison is not present in the literature yet, this work wants to place the emphasis on the fact that till now there is not a unique approach to solve problems of geometry assurance and no approach can be defined as better than another, in terms of results.

Tolerance analysis supports tolerance assignment: The industrial case study of skillet

Thisworkpresentsamethodtosupportproductdesign,sinceitshowshowtousetogethertolerance assignmentandanalysisforchoosingamongdifferentsetoftolerancesassignedtothesameproduct.It startsfromtoleranceassignmentthatproducesdifferentsetsoftolerancesfortheproductcomponents whichareallacceptablefromafunctionalpointofview.Ittranslateseachassignedsetoftolerances intooneormoregroupsoftolerancesthatarerecognizedbythesoftwareusedfortoleranceanalysis. Therefore,thesoftwarefortoleranceanalysisisappliedtoeachgroupoftolerancesbymeansofa MonteCarlosimulationapproach.Finally, theobtainedresultsareintersectedorcompoundedto obtainthetrendofproductfunctionalrequirementsthatallowstoidentifythebestsetoftolerances assignedtotheproductcomponents.Thedevelopedmethodwasappliedtoaskillet,aplatformof anindustrialplantthatismadeoffivepartsconnectedbyscrews.Theobtainedresultsshowhowthe developednewmethodisavalidtooltosupportdesignforindustrialapplication. KEywoRdS Computer Aided Tolerancing, Monte Carlo Simulation, Skillet, Tolerance Analysis, Tolerance Assignment