Computer-aided Tolerance Analysis Research Articles

STEP AP 242 file-based automatic tolerance analysis of mechanical assembly using unified Jacobian Torsor Model and direct linearization method

ABSTRACT This work presents the approach and algorithms to develop a smart computer-aided tolerance analysis system that is capable of performing Unified Jacobian Torsor Model (UJTM) and Direct Linearization Method (DLM) based deterministic tolerance analysis on mechanical assemblies using the STEP AP 242 file data generated from the assembly 3D CAD model. The smart tolerance analysis system tested on two different CAD packages can automatically extract the B-rep data, tolerance data from the STEP AP 242 file and find the mating surface information to perform the tolerance analysis. The location of the STEP AP 242 file is given as the input into the developed smart system, and the final output is the deterministic variation in the functional requirement and the plot showing the percentage contribution of tolerance to the variation in functional requirement of the mechanical assembly. The capability of the developed smart system is validated against the two mechanical assembly case studies, and the results computed by the developed system are an exact match with the tolerance values calculated manually.

Interoperability of CAD geometry and product manufacturing information for computer integrated manufacturing

ABSTRACT Model-Based 3D engineering has gained wide popularity in recent times for various Computer-Aided Engineering applications, bypassing the need for 2D drawings, thereby creating an efficient digital thread, reducing development time and improving the product quality. With the use of model-based definition, most data required to design, analyze and manufacture aproduct is stored in digital format. The primary focus of the paper is to create aseamless digital thread for exchanging data from anative CAD file to astandard data format like ISO STEP AP242 and vice versa, which enables smart manufacturing by attaching product manufacturing information. Prior to STEP AP242, the only successful translation among CAD systems was for the boundary representation with very little or no manufacturing data. These standards will not be enough unless defined in amachine-readable format and are equipped with tools that can read/write from these data structures. The method presented enhances the neutral data format ‘Constraint Tolerance Feature (CTF) Graph’ to ‘Augmented Constraint Tolerance (aCTF) Graph’, which holds additional information required for manufacturing. This paper discusses the elements needed during CAD data exchange, for multiple CAE applications like Computer-Aided Tolerance Analysis, Computer-Aided Manufacturing, etc., and discusses the implementation of required translators.

Tolerance analysis of assemblies with sculptured components in composites materials: comparison between an analytical method and a simulation approach

PurposeThe purpose of this paper is to compare two different tools for tolerance analysis. Tolerance analysis is an important task to design and manufacture high-precision mechanical assemblies; it has received considerable attention in the literature. Many are the tools required to carry out a tolerance analysis, and may be divided into two categories: the analytical models and the statistical software packages. No comparison exists in the literature among these two categories.Design/methodology/approachThis work presents a comparison between two different approaches to tolerance analysis: an analytical method, the variational model, and a statistical software, eM-Tolmate. The comparison has been developed on the same aeronautical case study that constitutes an actual product.FindingsThe proposed approach has been applied to an aeronautical case study. The results of the case study show how, when 2D tolerance analysis problems need to be solved, the two adopted tools give the same results. When the complexity of the tolerance analysis problems increases, the statistical software becomes the only choice to use. The new findings of the present paper are related to the fact that computer-aided tolerance analysis software packages remain the only choice to approach actual complex industrial products despite the extensive development of theoretical research.Research limitations/implicationsThis paper deals with a unique case study. However, the two adopted approaches and the obtained results are general, that is, they may be applied to any assembly.Practical implicationsTolerance analysis is a valid tool to foresee geometric interferences among the components of an assembly, before getting the physical assembly. It involves a decrease of the manufacturing costs.Originality/valueMany are the tools for tolerance analysis, such as different analytical models and different commercial software packages. Some are the comparisons among the different tools in the literature, but they are not exhaustive. Therefore, when a user has to solve an assembly problem to foresee the geometric interferences during the design stage, he/she does not know what to choose. The original contribution of the paper is to address the user’s choice through a comparison between an analytical model and a statistical software to solve the tolerance analysis problems of an actual aeronautical assembly.

A new computer-aided tolerance analysis and optimization framework for assembling processes using DP-SDT theory

Tolerance analysis is frequently used in predicting the product quality and balancing the design tolerances in mechanical assemblies. Generally, the tolerance analysis procedure is rather complex and cumbersome, and the existing computer-aided tolerance analysis methods are insufficient in dealing with some assembly information and user-defined quality requirements. This paper presents a new comprehensive tolerance analysis and optimization framework using deviation propagation and small displacement torsor (DP-SDT) theory. In this framework, four modules are designed to model the tolerances, analyze the assembly processes, predict the product quality, and optimize the tolerances respectively. Comparing with the existing methods, this framework can better support the complex assembly information like 3D dimensional tolerances, geometric dimensioning and tolerancing (GD&Ts), different tolerance zones, geometric information, assembly sequence, and various kinds of locating modes. And more practical quality requirements besides the distance precisions can be analyzed. The framework is a helpful supplement in tolerance analysis field. An application prototype using the framework has been developed for SolidWorks, and a tolerance optimization example of lathe saddle is provided to verify the performance of the framework.

A Quantitative Comparison of Tolerance Analysis Approaches for Rigid Mechanical Assemblies

Tolerance analysis is a key tool to predict the consequences of geometric variations on product quality. During the last decades, various approaches for the computer-aided tolerance analysis have been proposed, where each of them has specific advantages and disadvantages. In this contribution, three tolerance analysis approaches, namely tolerance stacks, vector loops, and the tolerance analysis based on the Small Displacement Torsor are quantitatively compared with the tolerance analysis based on Skin Model Shapes considering a typical case study. The novelty of the contribution lies in the profound assessment of these approaches and their results.

Tolerance Analysis with eM-TolMate

This article presents a review of a commercial computer-aided tolerance analysis tool, eM-TolMate, which is embedded in four major CAD systems (Catia [1], UG [2], Pro/E [3], SDRC [4]). eM-TolMate combines the Monte Carlo statistical simulation techniques with an internal tolerance management system and identifies the key characteristics (i.e. dimensions/clearances of interest) of nominal component models that are critical to proper assembly. Features and tolerances are directly created in CAD models and both single component or multi component analyses are available. For assemblies, eM-TolMate offers the capability to apply user-defined assembling rules or to automatically detect mating conditions. Actual features are varied within the specified tolerance range, and standard or user-defined statistical distributions are used in simulation runs to determine variations of key characteristics. It also offers the capability to rank tolerances based on contribution to the variation, so the user can identify where tolerances need to be tightened or can be loosened. eM-TolMate [5] represents a useful tool in tolerance analysis of mechanical assemblies.

Computer aided tolerance analysis for improved process control

This paper describes a case study where tolerance analysis techniques were used to analyze the cause of poor product performance and determine new specifications and process settings. Both 1D and 3D Monte-Carlo simulation analyses are described. A procedure for compensatory tolerancing is presented and demonstrated as a method of determining the appropriate tolerances once the product is in full-scale production.

Man-machine communication in computer-aided tolerance analysis of electronic circuits

In this paper the communication characteristics of a software system, designed to perform the on-line statistical analysis of electronic circuits on a multiprogrammed computer connected with a satellite graphics system, are described. A data structure which provides a systematic and flexible way of storing and manipulating all network information items is presented. The problem of connecting the central computer to the satellite processor is studied and a partition of data structure between the two computers is proposed.