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Design Innovation Paper

Experimental and Numerical Study of a Fixturing System for Complex Geometry and Low Stiffness Components

[+] Author and Article Information
Andrés A. Gameros

Rolls-Royce Manufacturing and
On-Wing University Technology Centre,
The University of Nottingham,
C31 Coates Building,
Nottingham NG7 2RD, UK;
School of Engineering and Sciences,
Tecnológico de Monterrey,
Monterrey CP64849, México
e-mail: andres.gameros@nottingham.ac.uk

Dragos Axinte

Rolls-Royce Manufacturing and
On-Wing University Technology Centre,
The University of Nottingham,
Coates Building, Room A63,
University Park,
Nottingham NG7 2RD, UK
e-mail: dragos.axinte@nottingham.ac.uk

Héctor R. Siller

School of Engineering and Sciences,
Tecnológico de Monterrey,
Ave. Eugenio Garza Sada 2501 Sur.,
Monterrey CP64849, NL, México
e-mail: hector.siller@itesm.mx

Stewart Lowth

Rolls-Royce Manufacturing and
On-Wing University Technology Centre,
The University of Nottingham,
Coates Building, Room A37b,
University Park,
Nottingham NG7 2RD, UK
e-mail: stewart.lowth@nottingham.ac.uk

Peter Winton

Rolls-Royce Plc,
PO Box 31, Mail Code GMC-1,
Derby DE24 8BJ, UK
e-mail: peter.winton@rolls-royce.com

Manuscript received January 4, 2016; final manuscript received August 5, 2016; published online November 10, 2016. Assoc. Editor: Z. J. Pei.

J. Manuf. Sci. Eng 139(4), 045001 (Nov 10, 2016) (12 pages) Paper No: MANU-16-1004; doi: 10.1115/1.4034623 History: Received January 04, 2016; Revised August 05, 2016

The production of freeform components is challenging, not only from the point of view of process optimization but also when it comes to the selection and design of the fixturing systems. Currently, most commercially available fixturing systems are difficult to conform to geometrically complex components; while the systems that manage to provide industrially feasible solutions (such as encapsulation techniques) present several limitations (e.g., high complexity, limited reliability, and risk of elastic deformation of the part). In this context, the present work proposes a simple, yet efficient, concept of a fixture capable of holding complex components through the use of compliant/deformable diaphragm elements. The fundaments of this innovative system (i.e., freeform diaphragm-based fixturing system) have been simulated through an experimentally validated finite-element (FE) model, with results showing a good agreement between numerical and measured data (displacement average error ϵav = 4.04%). The main interactions of the system with a workpiece (e.g., contact area and clamping force) have been numerically and experimentally studied, confirming the system's capacity to generate distributed clamping forces in excess of 1000 N. Based on the modeling activities, an advanced prototype for holding a “generic” freeform component was developed. Using this prototype, a repeatability study then showed the capacity of the system to deterministically position and hold complex geometries. Finally, the proposed fixturing system was thoroughly evaluated under demanding machining conditions (i.e., grinding), and the results showed the ability of the fixture to maintain small part displacement (dx < 10 μm) when high cutting forces are applied (Max. FR = 1021.24 N). Design limitations were observed during the grinding experiments, and the lineaments are presented in order to develop improved further prototypes. Overall, the proposed fixturing approach proved to be a novel and attractive industrial solution for the challenges of locating/holding complex components during manufacture.

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References

Figures

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Fig. 1

Evolution of fixturing systems

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Fig. 10

Validation results for contact area at maximum pressure (pa = 0.8 MPa) and different clearance Δc in terms of: measured by pressure films (a) and FE simulations (b)

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Fig. 8

Schematics of the setup for the validation of contact area (a), clamping force (b), and experimental setup for force measurement (c)

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Fig. 9

FE and experimental results for contact area (a) and clamping force (b) at the workpiece/fixture interface (Δc = 0.2 mm)

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Fig. 2

The fixturing system core concept before (a) and during clamping (b). Isometric view of a freeform diaphragm-based fixture (c) with a rigid wall for location (d).

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Fig. 3

Dimensions of half-box prototype with a single straight diaphragm showing the probing points for validation of initial FE simulations and direction of view from the internal section (I.V., section A-A)

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Fig. 4

Displacements (a) and stress distribution—von Mises—(b) as seen from the internal section I.V. for unconstrained diaphragm of the half-box prototype (actuation pressure pa = 0.8 MPa)

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Fig. 5

Schematic of DIC system (a) and experimental setup (b) for FE validation of unconstrained diaphragm of the half-box prototype

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Fig. 6

FE results versus digital image correlation (DIC) measurements at point P1 for deformation in Z axis (a) and principal stresses (b)

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Fig. 7

Schematic of workpiece—diaphragm interaction before (a) and after (b) actuating pressure is applied into half-box fixture (b)

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Fig. 11

FE results for the total Fc (a) and maximum σVM (b) at different Δc

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Fig. 12

Advanced full-box prototype (a) and its main dimensions (b)

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Fig. 13

Displacement (a) and von Mises stress (b) results for FE model of diaphragm area

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Fig. 14

Measurement planes—T, M, B—(a) and experimental setup (b) for FE validation of deformations of the full-box prototype

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Fig. 15

Reconstructed CMM measurements (a) and FE validation for displacement at bottom plane (b)

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Fig. 16

Schematic of location plate (a), assembly of the system with special part (b) and datum planes and references for CMM measurements (c)

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Fig. 17

Set up for VIPER grinding trials (a) and description of full-box prototype positions: CP1 (b) and CP2 (c)

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