Expert View

Design of Deformable Tools for Sheet Metal Forming

[+] Author and Article Information
Lorenzo Iorio

Area 5,
Piacenza 29122, Italy
e-mail: lorenzo.iorio@musp.it

Luca Pagani

School of Computing and Engineering,
University of Huddersfield,
Huddersfield HD13DH, United Kingdom
e-mail: l.pagani@hud.ac.uk

Matteo Strano

Dipartimento di Meccanica,
Politecnico di Milano,
Milan 20133, Italy
e-mail: matteo.strano@polimi.it

Michele Monno

Dipartimento di Meccanica,
Politecnico di Milano,
Milan 20133, Italy
e-mail: michele.monno@polimi.it

Manuscript received September 30, 2015; final manuscript received June 14, 2016; published online July 28, 2016. Assoc. Editor: Rajiv Malhotra.

J. Manuf. Sci. Eng 138(9), 094701 (Jul 28, 2016) (10 pages) Paper No: MANU-15-1502; doi: 10.1115/1.4034006 History: Received September 30, 2015; Revised June 14, 2016

Traditionally, industrial sheet metal forming technologies use rigid metallic tools to plastically deform the blanks. In order to reduce the tooling costs, rubber or flexible tools can be used together with one rigid (metallic) die or punch, in order to enforce a predictable and repeatable geometry of the stamped parts. If the complete tooling setup is built with deformable tools, the final part quality and geometry are hardly predictable and only a prototypal production is generally possible. The aim of this paper is to present the development of an automatic tool design procedure, based on the explicit FEM simulation of a stamping process, coupled to a geometrical tool compensation algorithm. The FEM simulation model has been first validated by comparing the experiments done at different levels of the process parameters. After the experimental validation of the FEM model, a compensation algorithm has been implemented for reducing the error between the simulated component and the designed one. The tooling setup is made of machined thermoset polyurethane (PUR) punch, die, and blank holder, for the deep drawing of an aluminum part. With respect to conventional steel dies, the plastic tools used in the test case are significantly more economic. The proposed procedure is iterative. It allows, already after the first iteration, to reduce the geometrical deviation between the actual stamped part and the designed geometry. This methodology represents one step toward the transformation of the investigated process from a prototyping technique into an industrial process for small and medium batch sizes.

Copyright © 2016 by ASME
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Fig. 1

Materials comparison price versus coarse machining energy—data coming from CES EDUPACK 2015

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Fig. 2

Geometry of the test case used for developing the optimization algorithm

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Fig. 3

Flexible tooling setup

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Fig. 4

(a) Stamping tools mounted on the press, punch, and blank holder are visible; (b) the stamped component made with the initial geometry of the tools

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Fig. 5

Force profiles versus die stroke

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Fig. 6

Scheme of the simulation setup at the beginning of the simulation

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Fig. 7

Schemes of the nodes and elements with boundary conditions applied

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Fig. 8

Fracture localization—experiment 4

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Fig. 9

Forming limit diagram of the experiment 4 simulation

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Fig. 10

Errors between fem and experimental profile for experiments 3 and 10

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Fig. 11

Experimental versus FEM errors; experimental versus designed profile deviations

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Fig. 12

Comparison between simulated (a) and measured (b) engineering major strain maps, simulated (c) and measured (d) engineering minor strain maps

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Fig. 13

Computation of the new tool nodes

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Fig. 14

Flow chart of the tool compensation algorithm

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Fig. 15

δ-plot before compensation; isometric and top views, units in (mm)

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Fig. 16

Strain concentrations on the tools after the stamping simulation with noncompensated tools

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Fig. 17

Deviations between designed and optimized components after one iteration

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Fig. 18

Norm of deviation vector versus iteration




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