Jean-Yves Dantan

Improved algorithm for tolerance allocation based on Monte Carlo simulation and discrete optimization

The allocation of design and manufacturing tolerances has a significant effect on both manufacturing cost and quality. This paper considers nonlinearly constrained tolerance allocation problems. The purpose is to minimize the ratio between the sum of the manufacturing costs (tolerances costs) and the risk (probability of the respect of geometrical requirements). The techniques of Monte Carlo simulation and genetic algorithm are adopted to solve these problems. As the simplest and the popular method for non-linear statistical tolerance analysis, the Monte Carlo simulation is introduced into the frame. Moreover, in order to make the frame efficient, the genetic algorithm is improved according to the features of the Monte Carlo simulation. An illustrative example (hyperstatic mechanism) is given to demonstrate the efficiency of the proposed approach.

Tolerance synthesis: quantifier notion and virtual boundary

Abstract The purpose of functional tolerancing process is to define the geometrical specifications of parts ensuring functional requirements. For automotive and aircraft industries, the tolerance synthesis has become an important issue in product design process. Indeed, designers need methods and rules to determine the tolerances. To define rules, a mathematical formulation of tolerance synthesis is detailed. This mathematical formulation of tolerance synthesis simulates the influences of geometrical deviations on the geometrical behavior of the mechanism, and integrates the quantifier notion (existential quantifier ‘there exists’ and universal quantifier ‘for all’). It takes into account not only the influence of geometrical deviations but also the influence of the types of contacts on the geometrical behavior of the mechanism; these physical phenomena are modeled by convex hulls (compatibility hull, interface hull and functional hull) which are defined in parametric space. With this description by convex hulls, a mathematical expression of the admissible deviations of parts integrates the quantifier notion. This notion translates the concept that a functional requirement must be respected in at least one acceptable configuration of gaps (existential quantifier there exists), or that a functional requirement must be respected in all acceptable configurations of gaps (universal quantifier for all). With this approach, some rules are formalized to determine the modifier (maximum material condition or minimum material condition) function from the type of quantifier. These rules have been performed with success in French automotive industries.

Integrated Tolerancing Process for conceptual design

Abstract For car and aircraft industries, the management of geometrical variations has become an important issue in product design process and concurrent engineering. Indeed, designers need to manage dimensional and geometrical tolerances and to know information that contributed to their determination. The goal here is to put tolerancing in a concurrent engineering context. There are important questions that would need to be looked upon: How to integrate the tolerance synthesis in the design process? How to ensure the transition from function to geometrical specifications on parts? How to keep traceability of tolerances during the design process? Few answers exist today in academic works and there are few supports in CAD systems. Therefore, to build a coherent data model taken into account tolerances, we describe in this paper a multi-level approach that enables a tolerancing process integrated with conceptual design. The first level integrates information relating to functional aspects of an assembly. The second describes the structure of the assembly, and concerns the integration of functional needs and technological solutions. The last level translates functional requirements into geometrical requirements between/or on parts of the products, and provides the geometrical specifications on each part satisfying the geometrical requirements. This multi-level architecture is represented as an object oriented data model based on UML (Unified Modelling Language) that enable data management for functional tolerancing in design and keeping traces when querying about data.

An intuitionistic fuzzy grey model for selection problems with an application to the inspection planning in manufacturing firms

Abstract Most of complex selection problems in real-life applications are considered under multiple conflicting attributes for manufacturing firms. The appropriate selection plays an important role in the firm׳s performance from the tactical and operational viewpoints. The classical methods for the selection problems in manufacturing firms are inadequate to deal with uncertainties, including insufficiency in information availability and the imprecise or vague nature in experts׳ judgments and preferences. To overcome these difficulties, this paper introduces a novel distance-based decision model for the multi-attributes analysis by considering the concepts of intuitionistic fuzzy sets (IFSs), grey relations and compromise ratio approaches. A weighting method for the attributes is first developed based on a generalized version of the entropy and IFSs along with experts׳ judgments. Then, a new grey relational analysis is introduced to analyze the extent of connections between two potential scenarios by an intuitionistic fuzzy distance measurement. Finally, a new intuitionistic fuzzy compromise ratio index to prioritize the scenarios is proposed by considering the weight of the strategy for the maximum group utility in intuitionistic fuzzy grey environment. The feasibility and practicability of the proposed distance-based decision model is illustrated in detail, and it is implemented in a real case study to the inspection planning for the oil pump housing from Renault automobile manufacturing.

Mathematical modelling of a robust inspection process plan: Taguchi and Monte Carlo methods

This study develops a new optimisation framework for process inspection planning of a manufacturing system with multiple quality characteristics, in which the proposed framework is based on a mixed-integer mathematical programming (MILP) model. Due to the stochastic nature of production processes and since their production processes are sensitive to manufacturing variations; a proportion of products do not conform the design specifications. A common source of these variations is maladjustment of each operation that leads to a higher number of scraps. Therefore, uncertainty in maladjustment is taken into account in this study. A twofold decision is made on the subject that which quality characteristic needs what kind of inspection, and the time this inspection should be performed. To cope with the introduced uncertainty, two robust optimisation methods are developed based on Taguchi and Monte Carlo methods. Furthermore, a genetic algorithm is applied to the problem to obtain near-optimal solutions. To validate the proposed model and solution approach, several numerical experiments are done on a real industrial case. Finally, the conclusion is provided.

Assembly specification by Gauge with Internal Mobilities (GIM)—A specification semantics deduced from tolerance synthesis

Abstract Currently, standards such as ISO 1101 are used for the geometrical specification of mechanical parts. However, these standards are not sufficient to express exact functional requirements, even for assembly. The objective of this paper is to determine what to express exactly for assembly, that is, create the necessary specification semantics. A tolerance synthesis model is developed based on variational geometry. The model takes into account not only manufacturing deviations and gaps, but also the assembly process and nature of contacts between parts. The specification semantics is deduced from this tolerance synthesis. This semantics is based on virtual gauges, which are composed of an interface with the part and of a structure. The main contribution on the virtual gauge is the concept of internal mobilities allowing displacements between different entities of the gauge. This gauge takes also in account the nature of the contact between parts.

Tolerance analysis — Form defects modeling and simulation by modal decomposition and optimization☆

Abstract Tolerance analysis aims on checking whether specified tolerances enable functional and assembly requirements. The tolerance analysis approaches discussed in literature are generally assumed without the consideration of parts’ form defects. This paper presents a new model to consider the form defects in an assembly simulation. A Metric Modal Decomposition (MMD) method is henceforth, developed to model the form defects of various parts in a mechanism. The assemblies including form defects are further assessed using mathematical optimization. The optimization involves two models of surfaces: real model and difference surface-base method, and introduces the concept of signed distance. The optimization algorithms are then compared in terms of time consumption and accuracy. To illustrate the methods and their respective applications, a simplified over-constrained industrial mechanism in three dimensions is also used as a case study.

Set based robust design of mechanical systems using the quantifier constraint satisfaction algorithm

Embodiment design is an important phase of the design process where the initial design parameters and their feasible solution spaces with design configurations are decided for the design problem. This article presents a new approach of embodiment design space exploration of the product based on set based design with integration of robustness for the mechanical systems. The approach presented addresses the initial design phase of the mechanical systems design and provides a three step approach based on a formal expression syntax, transformation and evaluation engine and a computational algorithm for performing a domain search for sets of robust solutions for the product designs by taking into the account the variations and uncertainties related to the manufacturing process and material. The approach is based on the design domain exploration and reduction techniques. This is achieved by the utilization and integration of existential and universal quantifiers from the quantifier constraint satisfaction problem (QCSP) for the expression of the parameters and variables related to the product design and robustness. The quantifier notion has been used to develop the consistency check for the existence of a design solution and existence of a robust design solution. In order to compute the developed quantifier approach, an algorithm based on the transformation of the quantifier with interval arithmetic has also been developed. In order to demonstrate the capability of the developed approach, this article includes three examples of mechanical systems from earlier research works that apply the quantifier model and the resolution algorithm to successfully explore the design domain for robust solutions while taking into account different types of variations such as variations in mechanical/material properties, manufacturing variations or variations in geometric dimensions which may be of continuous or discrete type.

Formal Language for GeoSpelling

In order to tackle the ambiguities of Geometrical Product Specification (GPS), GeoSpelling language has been developed to express the semantics of specifications. A detailed syntax of GeoSpelling is proposed in this paper. A specification is defined as a sequence of operations on the skin model. The syntax is based on instructions used in computer programming language: call to functions and flow control by condition and loop. In GeoSpelling, the call to functions corresponds to the declaration of operations; loops make it possible to manage a set of features with rigor and conditions to select features from a set.

Design for human safety in manufacturing systems: applications of design theories, methodologies, tools and techniques

ABSTRACT During recent decades, there has been growing awareness of human safety in the design process. The purpose of this paper is to review the literature on design for human safety (DfHS) in manufacturing systems. To this end, a process for systematically reviewing DfHS studies was used. The authors focused in particular on the applications of design theories and methodologies (DTM) and design tools and techniques (DTT) to analyse and identify work situations in order to improve human safety in manufacturing system design. The authors also tried to identify the design phases in which these DTM and DTT could be applied. This research review covered papers published between 1980 and 2015, and combined seven groups of terms: DfHS, design, safety, DTM, DTT, risk and working situation. A critical analysis was also performed in view to defining a research agenda and the most prominent key actions capable of pointing out paths for future research.