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Research Papers

An Ontology for the Autonomous Reconfiguration of a Flexible Fixture Device

[+] Author and Article Information
Thomas Gmeiner

Virtual Product Development Group,
Institute of Product Development,
Technische Universität München,
Boltzmannstr. 15, 85748 Garching, Germany
e-mail: thomas.gmeiner@pe.mw.tum.de

Kristina Shea

Engineering Design and Computing Laboratory,
Department of Mechanical and Process Engineering, ETH Zurich,
8092, Zurich, Switzerland
e-mail: kshea@ethz.ch

Single-acting vises have one fixed anvil and one moveable slide as opposed to centric or double-acting vises where both jaws are moved simultaneously.

Modular fixtures are fixture systems assembled from modular components, such as locators, pins, and clamps that are mounted on special platforms with slot or hole-patterns. Due to their modular structure these fixtures are very flexible but also labor intensive in assembly and cost intensive in acquisition.

The link between setup planning and fixture design is not part of this paper. However, some core concepts from the field of setup planning, like the concept Active Surface, are necessary for fixture planning. These are already considered in the FIXON ontology and will be reused.

Contributed by the Computers and Information Division of ASME for publication in the JOURNAL OF COMPUTING AND INFORMATION SCIENCE IN ENGINEERING. Manuscript received April 25, 2012; final manuscript received January 31, 2013; published online April 22, 2013. Assoc. Editor: Bahram Ravani.

J. Comput. Inf. Sci. Eng 13(2), 021003 (Apr 22, 2013) (11 pages) Paper No: JCISE-12-1067; doi: 10.1115/1.4023587 History: Received April 25, 2012; Revised January 31, 2013

The need for reconfigurable manufacturing systems has long been recognized as a key factor to gain the necessary flexibility for economical production of small batch sizes. Automation of the reconfiguration processes is a challenge both on the hardware and the software level. Addressing this issue in the field of fixture design, a new reconfigurable fixture device for a CNC milling machine has been developed. The developed vise contains interchangeable and customizable jaws enabling the secure fixture of a variety of workpiece geometries. To enable automated reconfiguration, a reasoning system is needed that can determine feasible fixture configurations based on the given workpiece and part as well as the available fixture components. In this paper, an ontology for representing fixture design and reconfiguration knowledge for vise-type flexible fixtures is presented. The ontology builds on and extends an existing ontology for modular fixture design. The creation of the ontology is based on a systematic building methodology, going from informal to formal concept definitions in a middle-out approach. The core concepts and relations of the ontology are presented and the ontology is validated both on the informal and on the formal level by its ability to find feasible fixture configurations, i.e., appropriate vise jaw pairs to fix example workpieces. The ontology can represent type-specific fixture designs in an unambiguous way and can hence serve as a basis for the development of applications needed to create an autonomous fixture design system.

FIGURES IN THIS ARTICLE
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Copyright © 2013 by ASME
Topics: Design , Ontologies
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Figures

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Fig. 3

Ontology purpose: Represent domain knowledge and serve as basis for a computer-aided fixture design system that allows for autonomous fixture reconfiguration

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Fig. 2

Ontology building methodology, combination of meta process [31] and practical methods [20,32]

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Fig. 1

CAD model of FMS with CNC mill and lathe, conveyor system, handling robots and storage (top) and CAD model of the automatically reconfigurable vise (bottom)

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Fig. 6

Concept diagram of the core concepts and relations of the fixture design ontology

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Fig. 4

Example of an informal competency question with decomposition and rationale

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Fig. 5

Informal concept hierarchy of the class jaw

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Fig. 9

ID-based query created in Protégé and resulting instances of feasible jaws

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Fig. 7

Shape-based queries created in Protégé and resulting instances of feasible jaws

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Fig. 8

Dimension-based queries created in Protégé and resulting instances of feasible jaws

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