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1

Total inertial tolerancing, a new way to drive production

Pillet M., Denimal D., Pairel E., Samper S.

Journal of Machine Engineering

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2009

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Vol. 9, No. 3

17--28

EN

Inertial tolerancing is a new concept of tolerancing which has done a first standardization in France (NF XP E 04-008 (2009). The paper presents a generalization of the inertial tolerancing: total inertia. The goal of total inertial tolerancing is to use the information include in the numeric description of the product. The Total inertial tolerancing defined "consistent functional subset" and different coordinate systems. For each of these subsets, we defined the maximum variability accepted (maximum inertia) from digital target. Inertia is the mean square deviation of the differences between the actual part and the target, measured in accordance with normal to the surface. Each functional subset will be identified by different colors. The purpose of the production is to produce parts with the least variability compared to the numerical shape. The production problem can be represented by two vectors: The vector of the deviations from the target on all measured points, and the vector of the control factors. Thereof, the question is: What is the value to apply on each corrector to minimize the vector of deviations? A reply is given by the total inertial tolerancing of which the link between the maximum inertia and the production is strong. Thus, the problem consists into compute the pseudo-inverse matrix of the relation between the deviation and impact vectors. This pseudo-inverse matrix allows minimizing the least squares deviation, in other words, minimizing the inertia. In this paper, we will present an example of inertial tolerancing specification of a complex part and we will show how to adjust a production with its new approach.

2

Optimisation of a stamping process by a design of experiment linked to a modal analysis of geometric defects

Ledoux Y., Samper S., Favreliere H., Formosa F., Pairel E., Arrieux R.

Archives of Civil and Mechanical Engineering

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2006

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Vol. 6, no 1

5-17

EN

The aim of this work was to present a method that gives an optimized set of values for the process parameters in order to obtain stamped parts with the fewest defects. The springback, influenced by process parameters is one of the sources of defects. The process is simulated by the finite element method. A design of experiments is used to compute the mathematical model and to minimize the trials number. The defects are characterized by a set of modal shapes. A defect criterion is calculated from this decomposition. Then an optimization is made by minimizing of this criterion in order to obtain the best process parameters. An example is shown in order to explain the method.

PL

Celem pracy jest optymalizacja procesu kształtowania wytłoczek ze względu na możliwość eliminacji skutków sprężystych odkształceń powrotnych. Zastosowanie planowania eksperymentu (MES) jako eksperymentu wirtualnego oraz analizy modalnej w celu oceny kształtu wytłoczki umożliwiają wyznaczenie parametrów tłoczenia zapewniających dużą dokładność kształtu wytłoczki.

3

Correction of geometrical defects of stamping parts by numerical simulation and design of experiment

Pairel E., Ledoux Y., Arrieux R., Tabourot L., Incandela O.

Archives of Civil and Mechanical Engineering

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2004

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Vol. 4, no 4

75-86

EN

A method of correction and optimization of stamping processes is proposed. The experiment design and finite element methods are interfaced. This is applied in a part showing large springback. After determining some important process parameters that effect springback, a fractional factorial experiment design is built and the corresponding numerical simulations are carried out. This enabled us to obtain deformed meshes which were post-processed in order to measure a virtual part geometry. Linear mathematical relations between the part geometry and process parameters are established which allows determining their interactions and their influence on the geometrical shape of parts. Finally those mathematical relations were necessary for establishing correct values of the process parameters which lead to the expected geometry of parts.

PL

Zaproponowano metodę korekcji i optymalizacji procesów tłoczenia. Aby określić sprężynowanie wyrobów charakteryzujących się dużymi odkształceniami, zastosowano sprzężoną metodę planowania eksperymentu i metodę elementów skończonych. Określono istotne parametry wpływające na sprężynowanie, a następnie zastosowano analizę czynnikową i odpowiednie symulacje numeryczne. Wyniki w postaci zdeformowanych siatek zostały użyte do określenia wirtualnej geometrii wyrobów. Określono zależności liniowe pomiędzy geometrią wyrobu i parametrami procesu, które umożliwiły ustalenie ich wpływu i wzajemnego oddziaływania na kształt geometryczny wyrobów. Te zależności pozwoliły ustalić poprawne wartości parametrów procesu umożliwiające otrzymanie wyrobów o oczekiwanej geometrii.