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Research Papers

Tool Load Sensitivity Against Multidimensional Process Influences in Microblanking of Copper Foils With Silicon Punches

[+] Author and Article Information
Sven Hildering

Institute of Manufacturing Technology,
Friedrich-Alexander-Universität
Erlangen-Nürnberg,
Egerlandstraße 13,
Erlangen 91058, Germany
e-mail: sven.hildering@fau.de

Markus Michalski

Institute of Manufacturing Technology,
Friedrich-Alexander-Universität
Erlangen-Nürnberg,
Egerlandstraße 13,
Erlangen 91058, Germany
e-mail: markus.michalski@fau.de

Ulf Engel

Mem. ASME
Institute of Manufacturing Technology,
Friedrich-Alexander-Universität
Erlangen-Nürnberg,
Egerlandstraße 13,
Erlangen 91058, Germany
e-mail: ulf.engel@fau.de

Marion Merklein

Institute of Manufacturing Technology,
Friedrich-Alexander-Universität
Erlangen-Nürnberg,
Egerlandstraße 13,
Erlangen 91058, Germany
e-mail: marion.merklein@fau.de

Manuscript received November 13, 2015; final manuscript received April 17, 2016; published online June 20, 2016. Assoc. Editor: Rajiv Malhotra.

J. Manuf. Sci. Eng 138(9), 091004 (Jun 20, 2016) (9 pages) Paper No: MANU-15-1570; doi: 10.1115/1.4033522 History: Received November 13, 2015; Revised April 17, 2016

The continuous trend toward miniaturization of metallic microparts of high quality at low costs results in the need of appropriate production methods. Mechanical manufacturing processes like forming and blanking meet these demands. One major challenge for the application of them are the so-called size effects. Especially, the downsizing of the required manufacturing tools and adequate positioning cause higher effort with increasing miniaturization. One promising approach for downsizing of tools is the transfer of knowledge from microsystems technology. This study shows the process behavior of etched silicon punches in microblanking operations. For the application as tool material especially, the brittle material behavior and sensitivity against tensile stresses have to be considered. These mechanical loads favor wear in form of cracks and breaks at the cutting edge of the punch and thus decreasing tool life. In a special test rig these wear phenomena were observed in microblanking of copper foils. Although, high positioning accuracy between tools and workpiece can be assured within this test rig, scatter of tool life is observable. Therefore, a finite element (FE) analysis of the tool load in the microblanking process with special respect to tensile stresses was performed. Within the 3D FE model multidimensional positioning errors like tilting between punch and die were integrated. Their influence on the tool load in form of increasing tensile stresses is evaluated with respect to the type and magnitude of positioning error and verified by experimental results concerning wear. Furthermore, the effect of small outbreaks at the cutting edge on the process behavior and tool load is analyzed.

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Figures

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Fig. 1

Silicon punch for microblanking

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Fig. 2

Test rig for microblanking of thin metal foils

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Fig. 3

Die positioning system

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Fig. 4

Workpiece geometry of copper foils

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Fig. 5

Tool wear at silicon punches

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Fig. 6

Cause-and-effect diagram for tool fracture in microblanking

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Fig. 7

Schematic illustration of 3D FE model (a) and punch mesh refinement (b)

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Fig. 8

True stress true strain curve for investigated copper foil

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Fig. 9

Methodology for numerical analysis of tool load

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Fig. 10

Comparison of sheared edge and punch forces in simulation and experiment

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Fig. 11

Maximum tensile stresses in the silicon punch at different stroke distances

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Fig. 12

Stress distribution in the silicon punch at different punch stroke distances

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Fig. 13

Possible multidimensional positioning errors in microblanking

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Fig. 14

Maximum tensile stresses for lateral misalignment

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Fig. 15

Maximum tensile stresses for punch rotation along vertical punch axis

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Fig. 16

Maximum tensile stresses for tilting error along the cutting edge

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Fig. 17

Stress distribution at different punch stroke positions for tilting error β

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Fig. 18

Maximum tensile stresses for tilting error perpendicular to the cutting edge

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Fig. 19

Stress distribution at different punch stroke positions for tilting error ϑ

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Fig. 20

Typical dimensions of outbreaks at the cutting edge and integration into FE model

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Fig. 21

Maximum tensile stresses for different outbreak types at the silicon punch

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Fig. 22

Maximum tensile stresses for different process influences

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Fig. 23

Characteristic positions of maximum tensile stresses for different influences

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Fig. 24

Verification of numerical tool load results by wear behavior in experiment

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