Publications

Title Real-Time Control of Powder Towpreg Production Using Embedded Processing and Machine Vision
Source Proc. 50th Intl. SAMPE Symp. and Exhib.
Year 2005
Author(s) Allred, R. E.; Wesson, S. P.; Babow, D. A.
Abstract We described previously a production facility for manufacturing powder towpreg (R. E. Allred, S. P. Wesson, and D. A. Babow, "Powder Impregnation Studies for High Temperature Towpregs,” SAMPE J, 40 (6), 40 2004). The system consisted of a payout tensioner, a powder curtain, sintering furnaces, and windup motors. Important goals for subsequent development were to increase productivity by raising the line velocity from 6 m/min to 36 m/min, add additional tows, and to optimize uniformity of polymer loading along the length of each tow. A four-creel HE-2002A tensioner now provides accurate maintenance of line tensions ranging from 20 g to 100 g at line velocities ranging from 3.2 m/min to 36 m/min. Our system now has a proven production capacity of 11 kg/hr of carbon fiber/epoxy towpreg using 12K tows. Tows emerging from the tensioner pulleys are 0.6 cm wide, and are spread to 3.2 cm using an air knife. Spread tows are backlit with a red LED lightbox, imaged at 1 Hz with a Basler A601 CCD camera, and the images are processed with a National Instruments 1454 Compact Vision System (CVS) to provide the tow width and the area percentage of voids in the tow caused by false twists. These parameters are sent by network connection to a cFP-2020 real-time processor from National Instruments. The cFP-2020 processor is integrated with banks of analog inputs, analog outputs, relays and digital outputs that control all the machinery on the towpreg line. All of the analytical instrumentation on the towpreg line is monitored by the cFP-2020 using serial and network connections. Code for both the 1454 CVS and cFP-2020 embedded processors are written in LabVIEW 7.1 Real-time from National Instruments. We found that low-frequency variation in polymer loading on the tow, as measured with an inline Compton backscatter gauge, is predicted by changes in tow width and void area as the tow enters the powder curtain. This measurement will form the basis for closed loop, real-time control of polymer loading using PID or fuzzy logic algorithms that will further improve towpreg quality.
Keywords Prepreg Materials, Processing/Fabrication Equipment, Quality Assurance (QA)/Quality Control (QC), towpreg, sintering, tow, powder, polymer

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