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Research Papers

Surface and Shape Deposition Manufacturing for the Fabrication of a Curved Surface Gripper

[+] Author and Article Information
Srinivasan A. Suresh

Department of Mechanical Engineering,
Stanford University,
Stanford, CA 94305
e-mail: sasuresh@stanford.edu

David L. Christensen

Department of Mechanical Engineering,
Stanford University,
Stanford, CA 94305
e-mail: davidc10@stanford.edu

Elliot W. Hawkes

Department of Mechanical Engineering,
Stanford University,
Stanford, CA 94305
e-mail: ewhawkes@stanford.edu

Mark Cutkosky

Department of Mechanical Engineering,
Stanford University,
Stanford, CA 94305
e-mail: cutkosky@stanford.edu

Manuscript received August 14, 2014; final manuscript received December 23, 2014; published online February 27, 2015. Assoc. Editor: Aaron M. Dollar.

J. Mechanisms Robotics 7(2), 021005 (May 01, 2015) (7 pages) Paper No: JMR-14-1212; doi: 10.1115/1.4029492 History: Received August 14, 2014; Revised December 23, 2014; Online February 27, 2015

Biological systems such as the gecko are complex, involving a wide variety of materials and length scales. Bio-inspired robotic systems seek to emulate this complexity, leading to manufacturing challenges. A new design for a membrane-based gripper for curved surfaces requires the inclusion of microscale features, macroscale structural elements, electrically patterned thin films, and both soft and hard materials. Surface and shape deposition manufacturing (S2DM) is introduced as a process that can create parts with multiple materials, as well as integrated thin films and microtextures. It combines SDM techniques, laser cutting and patterning, and a new texturing technique, surface microsculpting. The process allows for precise registration of sequential additive/subtractive manufacturing steps. S2DM is demonstrated with the manufacture of a gripper that picks up common objects using a gecko-inspired adhesive. The process can be extended to other integrated robotic components that benefit from the integration of textures, thin films, and multiple materials.

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References

Figures

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Fig. 1

Schematic of curved surface gripper showing components and forces. Load is supported by shear forces in the adhesive membrane; normal forces at the adhesive pads are negligible.

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Fig. 2

Gripper picking up common objects: football is gripped along the long curvature (r ≈ 23 cm); coffee mug is grasped obliquely (r ≈ 8 cm); and apple presents strong curvature in two directions (r ≈ 7 cm)

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Fig. 3

Process flow for manufacture of a curved surface gripper by S2DM. In this case, the process involves three parallel flows—SμS (M1–M5), in which the surface texture mold is manufactured; laser patterning/cutting (F1–F4), where the electrically active film is cut to shape and then patterned for desired properties; and traditional SDM (S1–S6), involving machining, casting, and addition of prefabricated components. Nominally additive and subtractive steps are labeled with plus/minus signs.

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Fig. 4

Coordinate system and illustration of sculpted surfaces. λ is the angle of the blade centerline with respect to the mold surface, β is the blade half angle, and θ is the local angle of the blade trajectory from the mold surface. 1, 2, and 4 are variations on direct cut and direct formed surfaces; 3a has an indirect formed surface, modified by machining 3b.

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Fig. 5

Microscope images showing shapes created with SμS: (a) wide features, (b) narrow features, (c) shapes with convex curves, (d) differentiated neighbor shapes, (e) hierarchical shapes, and (f) macroscale variation. Material is Dow Corning Sylgard 170.

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Fig. 6

Adhesive wedges cast on 25 μm film; total film thickness is 75 μm backing plus 50 μm texture features. Sample is from a patch of adhesives approximately 2.5 cm square; backing thickness was uniform throughout to within ±10 μm. Wedges are Sylgard 170, film is Kapton.

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Fig. 7

Demonstration of a patterned film electrostatically adhering to an acrylic plate. Applied voltage across the two interdigitated electrodes is 3 kV.

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Fig. 8

Response curve of a patterned film sensor. Film is etched copper clad Kapton, total area 12 cm2. Sensor was tested by covering with a glass slide and varying the area of contact.

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