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FBP Hot Dang Plastic Encasement
The fall 2008 Engineering 215 design class was commissioned by the Full Belly Project to modify the design of the Universal Nut Sheller (UNS). The UNS greatly increases the efficiency of shelling nuts in impoverished areas throughout the world. This simple device not only saves hours of painstaking labor, but also increases the viability of the nut as a cash crop. Team JAKS was assigned the task of redesigning the process by which the mold for the UNS is created so that it can be made entirely in Haiti using only local materials and labor. Currently, the mold is made from fiberglass in the United States using an expensive process. The hope of the Executive Director of the Full Belly Project, Jeff Rose, was that we could use H.D.P.E. for the mold in the form of plastic bags that are littered in excess throughout Haiti. Localizing this process to Haiti will not only decrease the cost tremendously and make the UNS more available to rural areas, but also encourage a stronger sense of self sustainability in Haiti.
Specifications for acquiring the desired thickness, or finding a process to incorporate into crocheting or traditional weaving to produce the thickness that the current mold has, is highly desirable.
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Technical specifications including a schematic (CAD, pictures of the device).
- Step 1 - Collection of Plastic Bags
- The plastic bags can be collected from rubbish piles and waterways wherever they are discarded. A system for collection may be set up where people can deposit the used bags in a central location for easy collection. This will keep the bags free from rips and holes and eliminate or reduce the need for washing.
- Step 2 - Washing and Drying of Plastic Bags
- If the plastic bags are soiled, they need to be washed using a mild detergent like dish soap, and rinsed. Once clean, the bags can be hung on clotheslines to dry, or just shaken to remove excess water. The bags do not need to be completely dry because the remaining water will evaporate during the rest of the process.
- Step 3 - Creating the Plastic Yarn
- In this step, a ball of plastic yarn is made in order to crochet the desired piece. First, a single bag is laid flat and folded in half lengthwise twice.
- Strips are cut perpendicular to the fold in a width of 1.5 inches.
- These strips are actually “rings” of plastic bag that can be looped together, making the plastic yarn.
- This yarn is then rolled into a ball to fold and flatten the yarn into an easily workable ribbon.
- Step 4 - Crocheting the Form
- Now the yarn can be crocheted into the shape of the finished piece. To do this, a multitude of crochet stitches may be employed depending on the desired shape. For the prototype, the desired shape is a bowl. The form is started with a circle made slightly larger than the circumference of the bowl, then the sides of the bowl are built up with stitches until the piece is loosely the shape of the bowl and covers it completely.
- Step 5 - Fusing the Plastic Form
- To fuse and harden the crocheted form, the ceramic bowl is placed in the oven at 350 degrees F for about 20 minutes. The ceramic bowl is removed from the oven and using a hot pad, the crocheted form is placed over the hot ceramic bowl to fuse the inside, while an iron is used to fuse the outside. The iron should be set at about 350 degrees F also, and pressure applied to fuse and harden the crocheted piece into a thick plastic bowl. The fused piece should be cooled to the touch.
Concrete can now be poured into the Hot Dang Plastic Encasement using another plastic bag as a liner.
Final Design Specifications
The best way to achieve a mold in the dimensions needed for the UNS is to have ceramic pieces made to be used for the hot inner forms. This could be done by using the current fiberglass molds to pour the ceramic into. This would produce ceramic forms for the outer and inner molds and the rotor just slightly smaller than the current UNS mold. These ceramic forms should be glazed to prevent the recycled HDPE from sticking to the forms, and these forms can be used to create several molds for the UNS. When the crocheted pieces are fused and hardened, they will be the same dimensions as the current UNS mold and no design adjustments will be required to produce a concrete UNS of the same size as the one now in production.
For the large main piece, each “face” of the mold can be produced separately. These pieces can then be joined with the plastic yarn using several overlapping looping stitches to reinforce the corners of the mold. When the crocheted pieces are completely assembled into the UNS mold components, they are ready to be fused.
The ceramic pieces can be heated in a large oven or over a fire to about 350 degrees F. Just as described in the prototype section, each crocheted piece is placed over its mold and a coal iron can be used to fuse the outside while the hot ceramic piece fuses the inside. After the pieces are cooled, they can be used to produce the UNS with the same procedure as is currently used.
- Make a prototype to the exact scale of the existing Universal Nut Sheller
- Make a ceramic negative for the crocheted plastic
- Integrate sewing, weaving, and/or crocheting devices into the formation of the mold
Haiti is located in between the Caribbean Sea and the Atlantic Ocean, just West of the Dominican Republic. The country is approximately the size of the Maryland, and is comprised mostly of rural slums. It is one of the least developed and most impoverished countries in the Western Hemisphere and because of this, the majority of Haitians live without access to clean water, sanitation, or garbage collection. (CIA World Fact Book, 2008) The pollution has become extensive, and many organizations are attempting to eradicate the problem through various forms of recycling. (UMM EWB, 2008)
1. “2006 United States National Post-consumer Plastics Bottle Recycling Report” <http://www.americanchemistry.com/s_plastics/sec_content.asp?CID=1593&did=7094> (November 28, 2008.)
2. “Embassy of Haiti in Washington, D.C. – Haiti – Yesterday and Today” <http://www.haiti.org/official_documents/la_presidence/Rene_preval/Haitiyesday.htm> (Nov. 28, 2008)
3. “Lesson Plans for the HDPE Recycling Process” <http://www.americanchemistry.com/s_plastics/hands_on_plastics/pdf/hdpeslideshow.pdf> (September 30, 2008.)
4. “One World Projects – Basketry – fair trade baskets woven in Rwanda, Nicaragua, Guatemala, Haiti, and more.” <http://www.oneworldprojects.com/products/haiti_main.shtml> (November 28, 2008)
5. 2005 Chemistry – Polyethylene “Chemistry Encyclopedia <http://www.chemistrydaily.com/chemistry/Polyethylene>
6. Anderson Consulting Service. May 2005. 7 Nov. 2008 <http://www.andersonconsultingservice.com/>.
7. Central Intelligence Agency. “Haiti” World Factbook. <https://www.cia.gov/library/publications/the-world-factbook/geos/ha.html>(Sept. 29, 2008)
8. Chang R. (2001), “General Chemistry: The Essential Concepts” , McGraw-Hill, 1221 Ave of the Americas, New York, NY, Chemical Bonding II: Molecular Geometry and Hybridization of Atomic Orbitals, (292-293)
9. Cook, Steven (2000) “Material Safety Data Sheet.” www.nt.gov.au/nreta/environment/assessment/register/pointceylon/pdf/ Appendices/appendix5.pdf (Oct. 1, 2008)
10. Corneliussen, Roger D. (2002) “Properties; High Density Polyethylene.” <http://www.maropolymeronline.com/Properties/HDPE%20Prop.asp#Melting%20Temperature> (October 2, 2008.)
11. Dearle, D.A. (1970). “Heats and Pressures. Plastic Molding Technique, Chemical Publishing Co.,Inc. , USA, 208-330.
12. Dynalab Corp. “Plastic Properties of High Density Polyethylene (HDPE)” http://www.dynalabcorp.com/technical_info_hd_polyethylene.asp
13. Encyclopedia Britannica1 (2008). “Hydrocarbon:: Polymerization” <http://www.britannica.com/EBchecked/topic/463684/plastic> (Oct. 30, 2008).
14. Encyclopedia Britannica¬¬2 (2008). “Plastic” <http://www.britannica.com/EBchecked/topic/463684/plastic> (Oct. 30, 2008).
15. Engineers Without Boarders, University of Minnesota Chapter. (1999-2008). “EWB-UMN Recycling Project” <http://www.tc.umn.edu/~ewb/projects_haiti.php>, (Sept. 29, 2008).
16. Full Belly Project. 7 Nov. 2008 <http://www.fullbellyproject.org/>.
17. General Electric Company. (2002). “Injection Molding Design Guidelines” GE Engineering Thermoplastics,<http://www.polymerhouse.com/datasheets/GE_Thermo%20Plastic%20%20DesignGuide_%5B1%5D.pdf> (Sept. 30, 2008).
18. Gingery, Vince. “Plastic Injection Molding Machine” Lindsay Books. 2006. 7 Nov. 2008 <http://www.lindsaybks.com/dgjp/djgbk/inject/index.html>.
19. Harper, Charles A. (1996). “Handbook of Plastics, Elastomers, and Composites.” McGraw-Hill, New York. 11.21-24.
20. Harper, Charles A. Modern Plastics Handbook. Blacklick, OH, USA: McGraw-Hill Professional Publishing, 2000. ttp://site.ebrary.com/lib/hsulib/ 10152805&ppg=56
21. J. Eng. Mater. Technol. -- October 2006 -- Volume 128, Issue 4, 572 (7 pages) Modeling Viscoelastic and Viscoplastic Behavior of High Density Polyethylene (HDPE) DOI:10.1115/1.2345449
22. Jolly, Frank. Personal Interview. 13 Nov. 2008.
23. Malcolm P. Stevens “Chemistry of Industrial Polymers“ Encyclopedia Britannica. 2008.
24. Milione S., Cuomo C., and Grassi A. (2006), “Ethylene polymerization catalyzed by group 4 metal complexes of tridentate heteroscorpionate ligands ” Topics in Catalysis, 40 (1-4), 163-172.
25. Miller, C. “High Density Polyethylene.” Waste Age, v. 38 no. 4 (April 2007) p. 124
26. Njeru,Jeremia, “The urban political ecology of plastic bag waste problem in Nairobi”, Kenya, GeoforumVolume 37, Issue 6, , November 2006, Pages 1046-1058.
27. Pribble, Wayne I. (1978) “Basic Mold Types and Features.” Plastics Mold Engineering Handbook. J. Harry DuBois, ed., Van Nostrand Reinhold Co. New Your, 18-60.
28. Vasile, Cornelia. Practical Guide to Polyethylene. Shawbury, Shropshire, GBR: Rapra Technology Limited, 2005. p 6.http://site.ebrary.com/lib/hsulib/ 10212598&ppg=14, 25