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Forming & Shaping of Plastics

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					Introduction to Manufacturing Engineering
ME1802


 Forming & Shaping of Plastics




                            SWMAIS   Department of Mechanical Engineering   1
         What Are We Going to Learn?
          What is Plastic?
          What are the types of Plastics?
          How the Plastics are made?
          What are the applications of Plastics?
          How to make Plastic products?




SWMAIS                               Department of Mechanical Engineering   2
         Plastics in General Use




SWMAIS                        Department of Mechanical Engineering   3
         Applications of Plastics
           Automobile bodies & components
           Electronic & electrical products
           Food, beverage, pharmaceutical containers
           Office equipment & appliances
           Sporting good
           Toys
           Furniture
           Housings & covering for many equipments



SWMAIS                                Department of Mechanical Engineering   4
             What are the Plastics Used
             in Different Applications?

          PE                  PS
          PVC                 PTFE
          PP                  ABS
          PET




SWMAIS                             Department of Mechanical Engineering   5
         What is Plastic?
          Produced by chemically modifying natural
           substances or synthesized from inorganic &
           organic raw materials
          Long chain Poly “mers”
          Polymerisation of Monomers




SWMAIS                              Department of Mechanical Engineering   6
             Additive Agent in Plastics

 Fillers                    Stabilisers
 Plasticizer                Antioxidants
 Lubricant                  Flame retardants
 Colouring agents




    SWMAIS                         Department of Mechanical Engineering   7
           Polymerisation


          Addition          Condensation




SWMAIS                         Department of Mechanical Engineering   8
         Why We Use Plastics?
          Corrosion resistance
          Resistance to chemicals
          Ease of manufacturing to complex shapes
          High strength-to-weight ratio
          Low thermal & electrical conductivity
          Surface finish
          Variety of optical properties



SWMAIS                           Department of Mechanical Engineering   9
         Structures of Plastics




SWMAIS                            Department of Mechanical Engineering   10
         Catagorisation of Plastics
           Thermosets
           Elastomers
           Thermoplastics




SWMAIS                        Department of Mechanical Engineering   11
         Thermosets




SWMAIS                Department of Mechanical Engineering   12
         Thermoplastics




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         Elastomers




SWMAIS                Department of Mechanical Engineering   14
                Mechanical Properties of Plastics
         TABLE 7.1
                                                           Elongation       Poisson’s
         Material                    UTS (MPa)   E (GPa)      (%)            ratio ()
         ABS                            28–55    1.4–2.8      75–5              —
         ABS, reinforced                 100        7.5        —               0.35
         Acetal                         55–70    1.4–3.5     75–25              —
         Acetal, reinforced              135        10         —            0.35–0.40
         Acrylic                        40–75    1.4–3.5      50–5              —
         Cellulosic                     10–48    0.4–1.4     100–5              —
         Epoxy                         35–140     3.5–17      10–1              —
         Epoxy, reinforced            70–1400     21–52        4–2              —
         Fluorocarbon                   7–48      0.7–2     300–100         0.46–0.48
         Nylon                          55–83    1.4–2.8     200–60         0.32–0.40
         Nylon, reinforced             70–210      2–10       10–1              —
         Phenolic                       28–70     2.8–21       2–0              —
         Polycarbonate                  55–70     2.5–3      125–10            0.38
         Polycarbonate, reinforced       110         6         6–4              —
         Polyester                       55          2       300–5             0.38
         Polyester, reinforced        110–160     8.3–12       3–1              —
         Polyethylene                   7–40     0.1–1.4    1000–15            0.46
         Polypropylene                  20–35    0.7–1.2     500–10             —
         Polypropylene, reinforced     40–100     3.5–6        4–2              —
         Polystyrene                    14–83     1.4–4       60–1             0.35
         Polyvinyl chloride             7–55     0.014–4     450–40             —
SWMAIS                                                     Department of Mechanical Engineering   15
         Making of various
         synthetic polymers




SWMAIS                        Department of Mechanical Engineering   16
         Factors Effecting
         Behavior of Plastics




SWMAIS                          Department of Mechanical Engineering   17
              General Recommendations
               for Plastic Products
 TABLE 7.3
 Design requirement                         Applications                                Plastics
 Mechanical strength          Gears, cams, rollers, valves, fan blades,     Acetal, nylon, phenolic,
                              impellers, pistons                            polycarbonate
 Functional and decorative    Handles, knobs, camera and battery            ABS, acrylic, cellulosic,
                              cases, trim moldings, pipe fittings           phenolic, polyethylene,
                                                                            polypropylene, polystyrene,
                                                                            polyvinyl chloride
 Housings and hollow shapes   Power tools, pumps, housings, sport           ABS, cellulosic, phenolic,
                              helmets, telephone cases                      polycarbonate, polyethylene,
                                                                            polypropylene, polystyrene
 Functional and transparent   Lenses, goggles, safety glazing, signs,       Acrylic, polycarbonate,
                              food-processing equipment, laboratory         polystyrene, polysulfone
                              hardware
 Wear resistance              Gears, wear strips and liners, bearings,      Acetal, nylon, phenolic,
                              bushings, roller-skate wheels                 polyimide, polyurethane,
                                                                            ultrahigh molecular weight
                                                                            polyethylene


SWMAIS                                                                    Department of Mechanical Engineering   18
Processing of Plastics




                 Department of Mechanical Engineering   19
         Introduction to
         Plastic Processing
           Can be molded, cast, formed, machined, &
            joined
           Complex shapes with ease of
            manufacturing
           Melt & cure at low temperatures
           Properties depends on the method of
            manufacture, & processing parameters
           Available as pellets, powder, sheet, plate,
            film, rod, & tubing
SWMAIS                              Department of Mechanical Engineering   20
 Forming & Shaping processes




SWMAIS                  Department of Mechanical Engineering   21
         Extrusion




SWMAIS               Department of Mechanical Engineering   22
         Extrusion of Thin Sheets




SWMAIS                       Department of Mechanical Engineering   23
         Extrusion of Thin Sheets




SWMAIS                       Department of Mechanical Engineering   24
         Injection Moulding
          Process all types of plastics
          Frictional heating
          Types of split dies:
              Cold-runner two plate – simplest
              Cold-runner three plate – separate runner system
              Hot-runner – heated runner system
          Typical injection moulded products:
          cups, containers, housings, tool handles, knobs,
            electrical & communication components


SWMAIS                                     Department of Mechanical Engineering   25
         Methods of Injection




SWMAIS                      Department of Mechanical Engineering   26
SWMAIS   Department of Mechanical Engineering   27
         Multi Component
         Injection Moulding




             A 2.2-MN (250-ton) injection-moulding machine



SWMAIS                                          Department of Mechanical Engineering   28
         Reaction Injection Moulding




SWMAIS                       Department of Mechanical Engineering   29
         Structural Foam
         Injection Moulding




SWMAIS                        Department of Mechanical Engineering   30
         Blow Moulding




SWMAIS                   Department of Mechanical Engineering   31
         Blow Moulding




SWMAIS                   Department of Mechanical Engineering   32
         Blow Moulding




SWMAIS                   Department of Mechanical Engineering   33
         Extrusion Blow Moulding




SWMAIS                      Department of Mechanical Engineering   34
         Injection Blow Moulding




SWMAIS                      Department of Mechanical Engineering   35
         Thermoforming




          Various thermoforming processes for thermoplastic sheet



SWMAIS                                             Department of Mechanical Engineering   36
         Rotational Moulding




SWMAIS                         Department of Mechanical Engineering   37
         Rotational Moulding Process




SWMAIS                      Department of Mechanical Engineering   38
 Compression Moulding




SWMAIS                  Department of Mechanical Engineering   39
         Transfer Moulding




SWMAIS                       Department of Mechanical Engineering   40
         Casting
          Conventional  Casting
          Centrifugal Casting
          Potting or Encapsulation
          Foam Moulding




SWMAIS                           Department of Mechanical Engineering   41
         Plastic Casting Processes




SWMAIS                        Department of Mechanical Engineering   42
 Comparative Costs and Production
 Volumes for Processing of Plastics
 TABLE 18.2
                                                                    Typical production volume, number of parts
                         Equipment Production Tooling
                                                                            2        3      4      5      6       7
                         capital cost     rate         cost       10     10       10     10     10     10      10
 Machining                 Medium       Medium         Low
 Compression molding         High       Medium         High
 Transfer molding            High       Medium         High
 Injection molding           High         High         High
 Extrusion                 Medium         High         Low         *
 Rotational molding          Low          Low          Low
 Blow molding              Medium       Medium      Medium
 Thermoforming               Low          Low          Low
 Casting                     Low        Very low       Low
 Forging                     High         Low       Medium
 Foam molding                High       Medium      Medium
 Source: After R.L.E. Brown, Design and Manufacture of Plastic Parts. Copyright (c) 1980 by John Wiley & Sons, Inc.
 Reprinted by permission of John Wiley & Sons, Inc.
 *Continuous process.

SWMAIS                                                                      Department of Mechanical Engineering      43

				
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posted:8/13/2011
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