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Research Papers

Deflection Compensations for Tool Path to Enhance Accuracy During Double-Sided Incremental Forming

[+] Author and Article Information
Lingam Rakesh

Department of Mechanical and
Aerospace Engineering,
Indian Institute of Technology Hyderabad,
Kandi,
Sangareddy 502285, Telangana, India
e-mail: Me13p1009@iith.ac.in

Srivastava Amit

Department of Mechanical Engineering,
Indian Institute of Technology Kanpur,
Kanpur 208016, Uttar Pradesh, India
e-mail: amitigcar@gmail.com

N. V. Reddy

Department of Mechanical and
Aerospace Engineering,
Indian Institute of Technology Hyderabad,
Kandi,
Sangareddy 502285, Telangana, India
e-mail: nvr@iith.ac.in

1Corresponding author.

Manuscript received November 15, 2015; final manuscript received June 13, 2016; published online July 19, 2016. Assoc. Editor: Rajiv Malhotra.

J. Manuf. Sci. Eng 138(9), 091008 (Jul 19, 2016) (11 pages) Paper No: MANU-15-1582; doi: 10.1115/1.4033956 History: Received November 15, 2015; Revised June 13, 2016

Incremental sheet forming (ISF) is a flexible sheet metal forming process that enables forming of complex three-dimensional components by successive local deformations without using component-specific tooling. ISF is also regarded as a die-less manufacturing process in the absence of part-specific die. Geometric accuracy of formed components is inferior to that of their conventional counterparts. In single-point incremental forming (SPIF), the simplest variant of ISF, bending near component opening region is unavoidable due to lack of support. The bending in the component opening region can be reduced to a larger extent by another variant of ISF, namely, double-sided incremental forming (DSIF) in which a moving tool is used to support the sheet locally at the deformation zone. However, the overall geometry of formed components still has unacceptable deviation from the desired geometry. Experimental observation and literature indicate that the supporting tool loses contact with the sheet after forming certain depth. This work demonstrates a methodology to enhance geometric accuracy of formed components by compensating for tool and sheet deflections due to forming forces. Forming forces necessary to predict compensations are obtained using force equilibrium method along with thickness calculation methodology developed using overlap of deformation zone that occurs during forming (instead of using sine law). A number of examples are presented to show that the proposed methodology works for a variety of geometries (axisymmetric, varying wall angle, free-forms, features above and below initial sheet plane, and multiple features). Results indicate that there is significant improvement in accuracy of the components produced using compensated tool paths using DSIF, and support tool maintains contact with sheet throughout the forming process.

Copyright © 2016 by ASME
Topics: Deflection , Geometry
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References

Figures

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Fig. 1

Schematic of tool configurations during DSIF: (a) aligned configuration and (b) normal configuration

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Fig. 2

Effect of component design on formed geometry in normal configuration: (a) tool over traversal when fillet is not used and (b) no tool over traversal when fillet is used

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Fig. 3

Forces acting on the forming tool during SPIF: (a) force exerted by tool and (b) forces on tool

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Fig. 4

Contact area approximation to predict forming force

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Fig. 5

Schematic of parameters used for sheet deflection calculation

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Fig. 6

Illustration of sheet behavior during one contour movement of tool: (a) diagonally opposite positions of tool in a contour, (b) component profile when tool is at position A, and (c) component profile when tool is at position B

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Fig. 7

Schematic showing compensation methodologies: (a) schematic of tool radius and sheet thickness compensation, (b) schematic of tool and sheet deflection compensation, (c) tool radius compensated path, and (d) deflection compensated path

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Fig. 8

(a) Custom-built DSIF machine and (b) load cell mounting for force measurement

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Fig. 9

Conical component in the absence of fillets: (a) formed component (DSIF-N) and (b) profile comparison

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Fig. 10

Forces, profile, and thickness comparisons of 60 deg wall angle conical component formed with and without compensated tool path (Δz = 0.3 mm, forming and support tool diameter = 10 mm, t0 = 0.88 mm, and Al 5052-O sheet): (a) component geometry, (b) component formed without compensation, (c) component formed with compensation, (d) measured and predicted forces, (e) profile comparison, (f) thickness comparison, (g) error in profile, and (h) thickness difference

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Fig. 11

Profile and thickness comparisons of varying wall angle components formed with and without compensated tool path (Δz = 0.2 mm, forming and support tool diameter = 10 mm, t0 = 0.88 mm, and Al 5052-O sheet): (a) component geometry, (b) component formed without compensation, (c) component formed with compensation, (d) profile comparison, (e) thickness variation, (f) profile deviation, and (g) thickness difference

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Fig. 12

Profile and thickness comparison of parabolic component formed with and without compensated tool path (Δz = 0.2 mm, forming and support tool diameter = 10 mm, t0 = 0.88 mm, and Al 5052-O sheet): (a) component geometry, (b) component formed without compensation, (c) component formed with compensation, (d) profile comparison, (e) thickness variation, (f) profile deviation, and (g) thickness difference

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Fig. 13

Profile and thickness comparison of component with features above and below the initial plane of the sheet (Δz = 0.2 mm, forming and support tool diameter = 8 mm, t0 = 0.88 mm, and Al 5052-O sheet): (a) component geometry, (b) component formed without compensation, (c) component formed with compensation, (d) profile comparison along AA, (e) profile comparison along BB, (f) error along AA, (g) error along BB, (h) thickness variation along AA, and (i) thickness difference along AA

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Fig. 14

Free-form with inclined base and a feature on it (Δz = 0.2 mm, forming and support tool diameter = 8 mm, t0 = 0.88 mm, and Al 5052-O sheet): (a) component geometry, (b) component before trimming, (c) component after trimming, (d) profile comparison along AA, (e) profile comparison along BB, (f) error along AA, (g) error along BB, (h) thickness comparison along AA, and (i) thickness difference along AA

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Fig. 15

Pyramidal shape with features on its walls: (a) geometry and measuring sections and (b) formed component

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Fig. 16

Profile comparison and error plots of pyramidal shape with features on its walls: (a) profile comparison along AA, (b) profile deviation along AA, (c) profile comparison along BB, and (d) profile deviation along BB

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