Research Papers

Modeling and Analysis of an Active Reconfigurable Fixturing Device Using a Bed of Pins Lowered on a Moving Platen

[+] Author and Article Information
Daniel Walczyk

Department of Mechanical, Aerospace and Nuclear Engineering, Rensselaer Polytechnic Institute, 110 8th Street, Troy, NY 12180-3590walczd@rpi.edu

Chris Munro

 Creare Inc., P.O. Box 71, Hanover, NH 03755

The rationale for choosing a dc solenoid to stop pin motion is discussed in Sec. 3.

It should be noted that such a scissor-type mechanism would not be used for more advanced prototypes because the vertical motion of the platen is not linearly related to motor speed through the complete range of motion.

J. Manuf. Sci. Eng 131(2), 021009 (Mar 27, 2009) (12 pages) doi:10.1115/1.3090882 History: Received November 26, 2007; Revised December 28, 2008; Published March 27, 2009

A reconfigurable fixturing device (RFD) is a computer-controlled reconfigurable bed-of-pins used for holding a compliant workpiece during manufacturing operations. A new RFD design, based on controlled clamping of loose pins descending on a position-controlled platen, is much simpler in design and is estimated to be significantly less expensive to make than commercially available machines. A RFD prototype with a 5×5 matrix of pins that can be individually clamped using custom-designed solenoids was prototyped to demonstrate the technology. A solenoid, which is considered the best method for clamping RFD pins, has not been used before in either commercial devices or prototypes discussed in the literature. Design models that predict stopping time and distance of pins clamped with a solenoid have also been developed along with a single pin experimental setup instrumented with linear encoders for model validation. The RFD prototype successfully demonstrated controlled clamping of the matrix of pins in either manual or computer-controlled mode. Another useful result was the validation of models for estimating solenoid force as a function of position, time for the solenoid plunger to impact the pin once energized, and distance the vertically descending pin drops before and immediately after impact by the plunger. Experimental data show that the models can accurately predict pin positioning performance with a solenoid as long as friction within the device is included. Since this RFD concept has been fully demonstrated by the prototype device, the next step in development will be a commercial machine. As such, the models for pin positioning can be used to predict shape accuracy of a particular RFD design and solenoid combination.

Copyright © 2009 by American Society of Mechanical Engineers
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Figure 6

12 V guardian electric solenoid

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Figure 7

Cross-sectional view of components comprising a RFD clamping solenoid

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Figure 8

Labeled cross-sectional view of a solenoid showing magnetic flux path (not to scale)

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Figure 9

Schematic and free body diagram of a solenoid plunger used to stop a descending RFD pin

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Figure 10

Free body diagram of a descending pin contacted by a solenoid plunger

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Figure 11

(a) Computer aided design (CAD) model and (b) prototype of the pin test rig, (c) close-up view of the solenoid clamping section, and (d) test rig mounted in a UTM

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Figure 12

Solenoid switching circuit

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Figure 13

Solenoid force versus air gap

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Figure 14

Plot of displacement versus time for Scenario 1

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Figure 15

Plot of displacement versus time for Scenario 2

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Figure 16

Plot of displacement versus time for Scenario 3 and models with and without friction

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Figure 1

(a) Continuous, (b) modular, and (c) reconfigurable support systems used for fixturing compliant parts during secondary manufacturing operations

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Figure 5

Schematic of solenoid-based pin stopping device

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Figure 4

Schematic of the RFD locking plate assembly

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Figure 3

(a) dc solenoid clamps connected to pin aperture plates and (b) fully-functional RFD proof-of-concept prototype



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