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P14415: System Design Review

P14415: System Design Review. Patrick Morabito John Wilson Michael Coffey Nathan Conklin Samuel Svintozelsky. Agenda. Background and Recap Information Why Plastic? Benchmarking: Products and Processes Concept Generation Concept Selection Process Selected Designs Risk Assessment

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P14415: System Design Review

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  1. P14415: System Design Review Patrick Morabito John Wilson Michael Coffey Nathan Conklin Samuel Svintozelsky

  2. Agenda • Background and Recap Information • Why Plastic? • Benchmarking: Products and Processes • Concept Generation • Concept Selection Process • Selected Designs • Risk Assessment • Test Plan • Moving Forward • Plastics Selection

  3. Background Information Inadequate sanitation is a major cause of preventable illnesses in children around the world. According to UNICEF, diarrhea alone causes over 1.6 million deaths in children under 5. These illnesses can easily be prevented by improving sanitation. However, cost is a major barrier limiting the adoption of sanitation in Haiti. Peter Morgan’s Arborloo is a simple latrine built over a small pit, which when filled is then moved to a new pit location. The old, filled pit then has vegetation planted on top of it, such as a fruit tree.

  4. Recap of Problem Statement •Current State •Difficult to adopt in rural areas due to high cost and transportation difficulties •Desired State •A low cost, portable, easy to assemble, and aesthetically pleasing arborloo base that can be financed in parts •Project Goals •Analyze the current arborloo design to find opportunities to incorporate plastic •Help improve sanitation in Haiti •Constraints •System must be financeable in parts •Design must incorporate plastic •Design must be compliant with the skills and tools available to the intended population

  5. Project Requirements

  6. Current Arborloo Pros: Relatively Inexpensive Strong Concept has been introduced in many parts of the world Cons: Heavy Not aesthetically pleasing Not portable Short life cycle Requires skilled labor Long installation time

  7. Why Plastic? • Lightweight • Ability to incorporating waste material • Durable • Many existing products to benchmark • Many choices for manufacturing • Used in many composites • Recyclable • May use existing products for manufacturing

  8. Benchmarking - Plastic Lumber Product Features • Low maintenance • Long life expectancy • Various lengths • No rotting • No splintering • No painting or staining • Cuts, drills and secures just like wood • Available in multiple profiles • Available in more than 10 colors • Textured surfaces • Continuous piece construction • Environmentally friendly • Resistant to marine borers, termites, fungus, salt and oils

  9. Benchmarking - Blow Molded Tables 48” round blow molded table can support roughly 490 lbs (likely much higher without steel legs) at a cost of $125.10 (likely less without steel frame) for quantities of 10+

  10. Benchmarking - Material Coatings Material Coatings: • Hydrophobic - Neverwet • Antimicrobial - Abloy Active Pros: • Enables cleanability Cons: • Cost • Coating lifetime

  11. Benchmarking- Processes Xanthos, Marino. Functional Fillers for Plastics. Weinheim: Wiley-VCH, 2010

  12. Manufacturing Process-Blow Molding • Air forces the heat softened material to take the shape of the mold being used • Pros: • Well suited for low and high production rates • Tooling is less expensive than injection molding • Various size applications, small bottles to 3000L containers • Cons: • Limited control of wall thickness • Produces excess waste that requires secondary removal processes • High start up costs

  13. Manufacturing Process-Vacuum Forming • A sheet of plastic is heated and then stretched onto or into a single-surface mold. A vacuum is then applied between the surface and the plastic sheet, holding the plastic to the mold. • Pros: • Molds can be very inexpensive • Simple operation • Time efficient • Possible to create own vacuum forming machine from household items • Cons: • Intricacy of parts is limited • Limited control over wall thickness • Overheating can cause material failure

  14. Manufacturing Process-Plastic Casting • A mold is filled with a liquid plastic, which then hardens to take the shape of the mold. • Pros: • Low cost • Low skill level needed • Cons: • Poor finish conditions • Requires close process control and monitoring • Risk of not equally filling mold cavity • Lower quality material properties

  15. Manufacturing Processes - Rotational Molding • Loading a measured quantity of polymer into the mold. • Heating the mold in an oven while it rotates, until all the polymer has melted and adhered to the mold wall. • The hollow part should be rotated through two or more axes, rotating at different speeds. • Cooling the mold, usually by fan. • Removal of the part. • Pros: • Experiment with wall thickness • Eliminates Fabrication costs • Add prefinished pieces to mold • Cons: • Expensive mold • Cooling of mold required • Low rotational speeds make getting to detailed areas difficult • Large shrinkage

  16. Manufacturing Processes - Injection Molding • Granular plastic is fed by gravity from a hopper into a heated barrel. • The granules are slowly moved forward by a screw-type plunger • The plastic is forced into a heated chamber, where it is melted. • As the plunger advances, the melted plastic is forced through a nozzle that rests against the mold, allowing it to enter the mold cavity through a gate and runner system. • The mold remains cold so the plastic solidifies almost as soon as the mold is filled. • Pros: • Tight tolerances • May have detailed design • Low cost after tooling is paid for • Cooling not required • Cons: • Expensive to create mold • limitations to size • Low flexibility with changes

  17. Manufacturing Processes - Hybrid / Existing • Use existing products to Fabricate a new product • Pros: • Many existing products to choose from • Inspires creativity • Positive for environment if using discarded products • low cost for material • Cons: • High fabrication expense • Low aesthetics • Finding resources • Limited by existing dimensions • Secondary processes required

  18. Functional Decomposition

  19. Functional Decomposition

  20. Functional Decomposition

  21. System Architecture

  22. Morphological Chart

  23. Morphological Chart cont.

  24. Morphological Chart cont.

  25. Functional Decomp → Morph Chart → Concept Gen. Concept Generation Engineering Specs →

  26. Pugh Chart - Datum 1

  27. Pugh Chart - Datum 2

  28. Pugh Chart - Datum 3

  29. Concept Selection

  30. Design #1 Pros: • Uses local materials • Structural support fill material • Possible secondary material integration with plastic casting/forming • Variable weight • Reduced material volume • Separable components • Modularity and opportunity for upgrades possible with lid • Financeable in parts Cons: • Inconsistency in filler materials • Lid attachment methods required • Fatigue at attachment points

  31. Design #2 Pros: • Simplistic design • Uses local materials • Weather resistant • Deck Like frame aesthetically pleasing • Modular design allows for easy repairs and replacement purchases • Stimulates local economy Cons: • Inconsistency in material quality • Cleanability • Need secondary support design to hold pieces together • Possible requirement for secondary manufacturing/cutting operations in Haiti

  32. Engineering Analysis - Designs 1 & 2 Assumptions: • Worst case scenario analysis for simply supported beam between two rigid supports. • Point force acting in center of base • Constant beam properties • 2D stress analysis

  33. Engineering Analysis - Designs 1 & 2 1 inch thick slab of polypropylene. Tensile strength of 32 MPa (matweb.com) Shigley’s mechanical engineering design / Richard G. Budynas, J. Keith Nisbett. —9th ed. p. cm. — (McGraw-Hill series in mechanical engineering)

  34. Design #3 Pros: • Load distributing shape • Can be a seat • Lip can be seated below ground slightly • Simple vacuum forming operation Cons: • Single piece (probably) • Not financeable in parts • Attachment to base necessary (if base is required)

  35. Design #4 Pros: • Load distributing shape • Can be a seat • Separable parts • Financeable in parts • Multiple identical pieces • Possible ability to injection mold or vacuum form small individual pieces. Cons: • Part attachment methods required • Fatigue at attachment points • Cleanability • Transportation of 4 pieces required • Need all 4 pieces to be functional product Sub-Concept 1 Sub-Concept 2

  36. Risk Assessment - Technical Risks

  37. Risk Assessment - Project Risks

  38. Risk Assessment - Team Risks

  39. Test Plan - Part 1

  40. Test Plan - Part 2

  41. Gantt Chart

  42. Constraints • Accelerated time line • Corrective Action: Work over winter break • Limited ability to test plastic additives • Corrective Action: Seek assistance from manufacturing companies • Limited Budget - Molds are quite expensive • Corrective Action: Create a temporary mold

  43. Moving Forward • Continue benchmarking • Materials • Manufacturing Processes • Existing Products • Create sub-system design • Begin model building • work with Industrial Design and Sculpture departments • Continue updating test plan • Perform more in-depth engineering analysis

  44. Plastics: Amorphous vs. Semicrystalline Thermoplastics AmorphousSemicrystalline Pros: Pros: Good formability Good chemical resistance Bond well with adhesives Good fatigue resistance Formable over wide temperature range Good wear resistance Durable/Load bearing Cons: Cons: Poor Chemical resistance High melting point Poor fatigue and stress properties Poor formability Poor wear resistance Poor bonding properties

  45. Plastics SOME considerations... • Acetal • HDPE (High Density Polyethylene) • PEEK (Poly-ether-ether-ketone) • PET(Polyethylene terephthalate) • Polypropylene • PPS (Polyphenylene sulfide) • PBT(Polybutylene terephthalate) • PETG (Amorphous copolyester) • UHMW-PE (Ultra high molecular weight polyethylene) • Polycarbonate Polycarbonate PEEK http://www.curbellplastics.com/engineering-plastics

  46. Plastic additives - Sisal fiber with bioresins - Coconut Shell Powder - Glass reinforced polymers - UV Stabilizers - Antimicrobials (silver ions used in cell phones, copper) - Carbon/glass fibers - Talc (stiffens thermoplastics, most commonly used for polypropylene) - Nut shells - Xanthos, Marino. Functional Fillers for Plastics. Weinheim: Wiley-VCH, 2010

  47. Questions and Feedback Questions?

  48. Sources • http://www.abloy.com/en/abloy/abloycom/Products-MPC/?groupId=1330&productId=822 (<-----picture) • http://www.neverwet.com/index.php(<-----picture) • http://www.curbellplastics.com/engineering-plastics • Shigley’s mechanical engineering design / Richard G. Budynas, J. Keith Nisbett. —9th ed. p. cm. — (McGraw-Hill series in mechanical engineering) • Xanthos, Marino. Functional Fillers for Plastics. Weinheim: Wiley-VCH, 2010

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