Deformable Sheet Metal Fixturing: Principles, Algorithms, and Simulations

Cai, Wayne; Hu, S. Jack; Yuan, Jinwei

doi:10.1115/1.2831031

Cited by 239 publications

(129 citation statements)

References 8 publications

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“…They use a remeshing algorithm, but do not address properties specific to sheet-metal parts such as buckling. Cai et al describe an N-2-1 fixturing principle in [5]. This is used instead of the conventional 3-2-1 principle to reduce deformation of sheet-metal parts.…”

Section: Related Workmentioning

confidence: 99%

“…They use an FEM of the part to model the deformation, and determine fixture locations by optimizing an objective that is a function of the deformations at the mesh nodes. Our Phase II is modeled on their approach, which is extended by [5] and [24]. Rearick et al [24] design a fixture for a sheet-metal part by using an objective function that is a weighted sum of the norm of the deformation and the number of fixtures in the objective function.…”

Section: Related Workmentioning

confidence: 99%

See 1 more Smart Citation

Unilateral Fixtures for Sheet-Metal Parts With Holes

Gopalakrishnan

Goldberg

Bone

et al. 2004

IEEE Trans. Automat. Sci. Eng.

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Abstract-In this paper, we introduce unilateral fixtures, a new class of fixtures for sheet-metal parts with holes. These fixtures use cylindrical jaws with conical grooves that facilitate part alignment; each jaw provides the equivalent of four point contacts. The fixtures are unilateral in the sense that their actuating mechanisms are restricted to one side/surface of the part, facilitating access to the other side/surface for assembly or inspection. We present a two-phase algorithm for computing unilateral fixtures. Phase I is a geometric algorithm that assumes the part is rigid and applies two-dimensional (2-D) and three-dimensional (3-D) kinematic analysis of form closure to identify all candidate locations for pairs of primary jaws. We prove three new grasp properties for 2-D and 3-D grips at concave vertices and define a scale-invariant quality metric based on the sensitivity of part orientation to infinitesimal relaxation of jaw position. Phase II uses a finite element method to compute part deformation and to arrange secondary contacts at part edges and interior surfaces. For a given sheet-metal part, given as a 2-D surface embedded in 3-D with edges, concavities and mesh nodes, Phase I takes ( + 4 3 log 1 3 + log ) time to compute a list of pairs of primary jaws ranked by quality. Phase II computes the location of secondary contacts in ( 3 ) time.Note to Practitioners-This paper was motivated by the problem of holding sheet-metal parts for automobile bodies but it also applies to other sheet-metal components that have cut or stamped holes. Existing approaches to fixturing such parts generally have contacting mechanisms on both sides of the sheet that restrict access for welding or inspection. This paper suggests a new approach using pairs of grooved cylinders, activated from only one side of the part (hence "unilateral"). These cylinders mate with opposing corners of holes in the sheet and push apart to hold the sheet in tension, thus acting as both locators and clamps. In this paper, we mathematically characterize the mechanics and conditions for a unilateral fixture to hold a given part. We then show how such fixtures can be efficiently computed; this can allow a computer-aided design (CAD) system (with finite element capability) to automatically generate and propose unilateral fixtures for a given part. Preliminary physical experiments suggest that this approach is feasible but it has not yet been incorporated into a CAD system nor Manuscript

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Section: Related Workmentioning

confidence: 99%

Section: Related Workmentioning

confidence: 99%

Unilateral Fixtures for Sheet-Metal Parts With Holes

Gopalakrishnan

Goldberg

Bone

et al. 2004

IEEE Trans. Automat. Sci. Eng.

View full text Add to dashboard Cite

show abstract

“…In order to not only determine the spatial location but also constrain the excessive deformation of sheet metal part, Cai et al proposed the "N-2-1" (N 3) locating principle for sheet metal fixture design and at the same time pointed out that the "N-2-1" locating principle was more suitable for sheet metal part than "3-2-1" principle [1]. Hence, one of the keys is to find the minimum number of locators their optimal positions to keep the sheet metal part under the allowable maximum deformation and reduce the maximum sheet metal deformation as greatly as possible in fixture design based on the "N-2-1" locating principle.…”

Section: Introductionmentioning

confidence: 99%

Determination of the Number of Fixture Locating Points for Sheet Metal By Grey Model

et al. 2017

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Abstract. In the process of the traditional fixture design for sheet metal part based on the "N-2-1" locating principle, the number of fixture locating points is determined by trial and error or the experience of the designer. To that end, a new design method based on grey theory is proposed to determine the number of sheet metal fixture locating points in this paper. Firstly, the training sample set is generated by Latin hypercube sampling (LHS) and finite element analysis (FEA). Secondly, the GM(1, 1) grey model is constructed based on the established training sample set to approximate the mapping relationship between the number of fixture locating points and the concerned sheet metal maximum deformation. Thirdly, the final number of fixture locating points for sheet metal can be inversely calculated under the allowable maximum deformation. Finally, a sheet metal case is conducted and the results indicate that the proposed approach is effective and efficient in determining the number of fixture locating points for sheet metal.

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“…Although research devoted to fixture design and optimization is extensive [1,2,14,15], it invariably assumes passive fixtures and static planning conditions. Recently, the problem of active fixture design is attracting increased attention, e.g., studying changing conditions due to moving loads [16].…”

Section: Introductionmentioning

confidence: 99%

“…A fixture is a device for locating, constraining, and adequately supporting a deformable workpiece during a manufacturing operation [1][2][3]. Components made of thin metallic or composite sheets are ubiquitous in automotive and aircraft manufacturing.…”

Section: Introductionmentioning

confidence: 99%

Task planning for cooperating self-reconfigurable mobile fixtures

Kasprzak

Zlatanov

Szynkiewicz

et al. 2013

Int J Adv Manuf Technol

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The work solves the problem of task and motion planning of a self-reconfigurable fixture system. A feasible solution is a key requirement for the viability of such systems, which have raised hopes of overcoming the deficiencies that more traditional fixtures are recognized to have in the dynamic conditions of modern manufacturing, with its increasing emphasis on flexibility, adaptability, and automation. The paper proposes an application-independent approach for the generation of a time-relevant action plan for the locomotion, reconfiguration, and positioning of two or more mobile robotic fixtures. The fixture agents need to provide local support for a large workpiece during machining. The path-planning problem is converted into a constraint satisfaction problem (CSP). The proposed approach is called Triple-CSP, as it applies an incremental state search to solve three hierarchical path-planning tasks for the three components of each mobile fixture agent: a supporting head, a mobile base, and a parallel manipulator. A final time-related trajectory (time scaling of actions) for the agents' entire task execution is obtained. Thus, the planner takes into account all the relevant physical, geometrical, and time-related constraints.

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Deformable Sheet Metal Fixturing: Principles, Algorithms, and Simulations

Cited by 239 publications

References 8 publications

Unilateral Fixtures for Sheet-Metal Parts With Holes

Unilateral Fixtures for Sheet-Metal Parts With Holes

Determination of the Number of Fixture Locating Points for Sheet Metal By Grey Model

Task planning for cooperating self-reconfigurable mobile fixtures

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