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

Abstract

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.