PRESSURE DISTRIBUTION EVALUATION OF DIFFERENT FILLING METHODS FOR DEPOSITION OF POWDERS IN DIES: MEASUREMENT AND MODELING
Open Access
- Author:
- Sayyar Roudsari, Saed
- Graduate Program:
- Agricultural and Biological Engineering
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- September 04, 2007
- Committee Members:
- Virendra Puri, Committee Chair/Co-Chair
Ali Demirci, Committee Member
Paul Heinz Heinemann, Committee Member
Ali Borhan, Committee Member - Keywords:
- Uniformity evaluation
Powder Mechanics
Powder deposition
Mathematical Modeling - Abstract:
- The aim of this research was to measure, analyze, and model the pressure distribution characteristics of powder deposition into rectangular and circular shallow dies using four filling methods. The feed shoe, the rotational rainy, the point feed, and the pneumatic filling methods were used to investigate the deposition characteristics into shallow dies. In order to evaluate the pressure distribution during filling of shallow dies, factors influencing powder deposition were studied. The factors included particle size and shape, particle size distribution, feed shoe speed, and tube cross-section (in case of feed shoe filling) and deposition rates (in case of rotational rainy, point feed, and pneumatic filling). A battery powder mixture (BPM) and microcrystalline cellulose (Avicel PH102) with median size of 84 and 600 , respectively, were used to fill a shallow rectangular die 32 30 mm and 6.5 mm deep and a shallow circular die 35 mm in diameter and 6.5 mm deep. The second generation of pressure deposition tester (PDT-II) with circular and square feed shoe tube cross-sections was used to measure the two powders’ pressure distribution characteristics. An innovative rotational rainy filling device was designed and fabricated. This versatile device can be used to measure filling characteristics at different rotational speeds (1-10 rpm) for various powders. The point feed (funnel fill) method with a funnel of 30 mm inlet diameter and 4.2 mm outlet diameter opening was used to fill the rectangular and circular shallow dies. The pneumatic filling method was designed and fabricated to fill the die using air as the conveying medium in a rectangular cross-section tube. The pneumatic filling device was limited to using only the BPM powder, since the Avicel powder generated substantial quantity of airborne dust during the test. Symmetry analysis, variance metrics, and uniformity analysis were used to quantify the deposition characteristics. The results showed that: 1) filled contour plot analysis was the most reliable method for measuring deposition characteristics; 2) for all filling methods, the circular die generated higher uniformity compared to rectangular die; 3) the rainy filling method generated the best uniformity of pressure distribution compared with the other three filling methods (average of 77% uniformity); 4) the point feed method and feed shoe filling method were the second and third best filling methods with the average uniformity of 64% and 55%, respectively; 5) the pneumatic filling method was not a suitable method to fill the die (21% uniformity of pressure distribution); 6) the average filling period for feed shoe, rotational rainy, and point feed were 8 second, 15 second, and 40 second, respectively; 7) higher stress was generated inside the rectangular die than in the circular die; 8) for rotational rainy fill and the point feed, deposition rates did not substantially influence the uniformity of pressure distribution inside the die; 9) feed shoe speed highly influenced the uniformity of pressure distribution inside the die; 10) the feed shoe tube cross-section did not influence the pressure distribution; 11) for feed shoe filling method, the areas of high pressure values (> 60 dm, where dm=decimeter equivalent of pressure) were less than 5% of the total area for both rectangular and circular dies; 12) most particle accumulation was observed in forward region of the die due to leveling process; 13) die geometry highly influenced the uniformity of pressure distribution; 14) the leveling procedure (removing surcharge powder) markedly increased non-uniformity within the die (approximately 20%); 15) the overall rate equation for all three filling methods was: , where h is equivalent height, F(t) is a function of time, and are coefficients ; 16) the root mean square error (RMSE) for feed shoe, rotational rainy, and point feed were 0.16 dm, 0.44 dm, and 0.32 dm; respectively; whereas the average relative difference (ARD) values were 7%, 16%, and 11%, respectively.