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Research Papers

Automatic 3D Spiral Toolpath Generation for Single Point Incremental Forming

[+] Author and Article Information
Rajiv Malhotra

Department of Mechanical Engineering, Northwestern University, Evanston, IL 60201; Indian Institute of Technology Kanpur, Kanpur 208016, Indiamalhotrarajiv2013@northwestern.edu

N. V. Reddy

Department of Mechanical Engineering, Indian Institute of Technology Kanpur, Kanpur 208016, Indianvr@iitk.ac.in

Jian Cao

Department of Mechanical Engineering, Northwestern University, Evanston, IL 60201; Shanghai Jiao Tong University, Shanghai 200240, Chinajcao@northwestern.edu

J. Manuf. Sci. Eng 132(6), 061003 (Oct 19, 2010) (10 pages) doi:10.1115/1.4002544 History: Received June 09, 2009; Revised August 01, 2010; Published October 19, 2010; Online October 19, 2010

Incremental forming (IF) of sheet metal is emerging as a useful flexible manufacturing process for forming customized shapes, some of which may not be formable using conventional techniques due to limitations of tooling or forming limit. In IF, the toolpath has a significant impact on the geometric accuracy, surface finish, and forming time of the formed component. Toolpath generation techniques used until date are based on commercial CAM packages (Skjoedt, 2007, “Creating 3D Spiral Tool Paths for Single Point Incremental Forming,” Key Eng. Mater., 344, pp. 583–590; Verbert, 2007, “Feature Based Approach for Increasing the Accuracy of the SPIF Process,” Key Eng. Mater., 344, pp. 527–534) and do not allow the generation of 3D spiral toolpaths for freeform components with constraints on both surface finish and geometric accuracy while simultaneously minimizing forming time. This work exploits the similarities between incremental forming and layered manufacturing to develop a methodology for automatic generation of 3D spiral single point incremental forming toolpaths for forming symmetric and asymmetric components, considering specified constraints on desired geometric accuracy and maximum specified scallop height while reducing the forming time. To test the developed methodology, the scallop heights of components formed using the developed methodology are measured and compared with the maximum permissible scallop heights specified. Furthermore, the geometric accuracy and forming time of the components formed using the developed methodology and by the toolpaths generated using commercial CAM software are compared. It is shown that the toolpaths generated using the developed methodology form components with better or similar geometric accuracy as compared with that generated by commercial CAM packages and with scallop heights lesser than the maximum permissible scallop height specified by the user. At the same time, the developed methodology also reduces the forming time as compared with commercial CAM toolpaths. This methodology can handle symmetric as well as asymmetric shapes and is a critical step toward automation of the toolpath generation for incremental forming.

Copyright © 2010 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

(a) CAD model of component and (b) contour toolpath

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Figure 2

Points generated on the contour toolpath

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Figure 3

3D spiral toolpath generated from contour toolpath

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Figure 4

Schematic of volumetric error calculation

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Figure 5

Schematic of scallop heights calculation

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Figure 6

Flowchart showing slice insertion methodology used

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Figure 7

(a) Part to be formed, (b) contour path generated without adaptive slicing, and (c) contour path generated with adaptive slicing

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Figure 8

Schematic illustrating adaptive slicing for 3D spiral toolpath generation

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Figure 9

Component consisting of planar surfaces

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Figure 10

Schematic showing the difference between trapezoidal and rectangular built edges

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Figure 11

Schematic of tool radius compensation

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Figure 12

(a) CAD model of the pyramid formed to examine the surface finish and (b) schematic of the incremental forming setup used

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Figure 18

Comparison of cross-sectional profiles between CAD component and components formed using developed methodology (adaptive slicing) and commercial CAM software

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Figure 19

Freeform components formed using toolpath from (a) CAM (30 slices), (b) CAM (40 slices), (c) CAM (50 slices), and (d) developed methodology

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Figure 20

Components formed using 3D spiral toolpaths generated by the developed methodology

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Figure 13

(a) Isometric view and (b) side view of freeform component formed to examine the geometric accuracy and forming time

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Figure 14

Comparison between scallop heights, measured, calculated from code, and maximum specified (10 μm) for (a) 20 deg pyramid, (b) 40 deg pyramid, and (c) 60 deg pyramid, each formed with three different tool sizes

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Figure 15

Comparison between scallop heights, measured, calculated from code, and maximum specified (50 μm) for (a) 20 deg pyramid, (b) 40 deg pyramid, and (c) 60 deg pyramid, each formed with three different tool sizes

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Figure 16

Comparison between scallop heights, measured, calculated from code, and maximum specified (10 μm) for (a) 4mm tool, (b) 6 mm tool, and (c) 8 mm tool for all three pyramidal components

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Figure 17

Comparison between scallop heights, measured, calculated from code, and maximum specified (50 μm) for (a) 4mm tool, (b) 6 mm tool, and (c) 8 mm tool for all three pyramidal components

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