SHAPING PROCESSES FOR PLASTICS SME Video - Plastic Processes Plastic Blow Molding (vts_12) Properties of Polymer Melts Extrusion Sheet, Film and Spinning Coating Processes Injection Molding In-class Assignment ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e

Two Types of Plastics Thermoplastics Chemical structure unchanged during heating Polymer melt - high viscosity & viscoelasticity Thermosets Curing process during heating Cross‑linking of molecular structure Once cured, they cannot be remelted Plastic molding is a net shape process Less energy is required than for metals Strength‑to‑weight ratios are competitive ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e

Viscosity Relationships ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e

Viscoelasticity - Die Swell Example Extruded polymer "remembers" its previous shape Die swell, a manifestation of viscoelasticity in polymer melts ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e

Extruder for Thermoplastics & Elastomers Extruder Barrel: Electric heaters melt feedstock Application: Door and window moldings ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e

Extrusion Die for Solid Cross Section (a) Die cross section to obtain (b) Square extruded profile ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e

Extrusion Die for Hollow Shapes ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e

Extrusion Die for Coating Wire cross‑section of die for coating of electrical wire ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e

Injection Molding Machine A large (3000 ton capacity) injection molding machine (Photo courtesy of Cincinnati Milacron). Polymer is heated and forced into a mold cavity Net shape Typical cycle time 10 to 30 sec Mold may contain multiple cavities ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e

Injection Molding Machine Diagram of an injection molding machine, reciprocating screw type (some mechanical details are simplified) ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e

Injection Molding Cycle ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e

Two-Plate Mold (b) open (a) closed Mold has two cavities Comment on shrinkage ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e

Another option: Hot‑Runner Molds Three-Plate Mold (b) open (a) closed Mold has two cavities Another option: Hot‑Runner Molds ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e

Toggle Clamps and Hydraulic Clamps ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e

SME Video ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e

In-class Assignment 1 of 2 In casting experiments performed using a certain alloy and type of sand mold, it took 155 sec for a cube‑shaped casting to solidify. The cube was 50 mm on a side. (a) Determine the value of the mold constant in Chvorinov’s Rule (b) If the same alloy and mold type were used, find the total solidification time for a cylindrical casting in which the diameter = 30 mm and length = 50 mm. ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e

In-class Assignment 2 of 2 A sand core located inside a mold cavity has a volume of 157.0 in3. It is used in the casting of a cast iron pump housing. Determine the buoyancy force that will tend to lift the core during pouring. Sand core density = 0.058 lb/in3 Cast iron density = 0.260 lb/in3 ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e

Test 1 Review Discussion 100 multiple choice 2 problems with calculations similar to in-class examples 2 challenge problems with calculations similar to in-class assignments Manufacturing economics problems will not be on the test ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e

Manufacturing Economics ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e

Time Permitting Content ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e

Defects in Extrusion Melt fracture caused by turbulent flow Velocity profile of melt through die opening can lead to defects Bambooing ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e

Sheet and Film: Slit Die Extrusion Application: product wrapping material, grocery bags and garbage bags ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e

Blown-film, Calendering & Spinning Blown‑film process for high production of thin tubular film Sheet out of rubber or rubbery thermoplastics (plasticized PVC) Melt spinning of continuous filaments ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e

Planar Coating Process Roll method Doctor-blade method ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e

Alternative Injection Molding Machine Designs Screw preplasticizer Plunger type ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e

Reaction Injection Molding (RIM) Application: bumpers and fenders RIM polyurethane parts possess a foam internal structure surrounded by a dense outer skin ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e

Compression Molding Molding compound available in several forms: powders or pellets, liquid, or preform compressed and cured ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e

Transfer Molding Pot transfer molding Plunger transfer molding ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e

Extrusion Blow Molding (1) extrusion of parison (2) parison is pinched (3) the tube is inflated ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e

Other Blow Molding Processes Injection blow molding: Stretch blow molding: Polyethylene terephthalate (PET) Very low permeability Strengthened by stretch blow molding ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e

Rotational Molding ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e

Vacuum Thermoforming ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e

Thermoforming Pressure thermoforming: Vacuum thermoforming: ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e

Mechanical thermoforming Vacuum thermoforming Application: boat hulls and shower stalls Mechanical thermoforming ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e

Polymer Foam Polymer‑and‑gas mixture Porous or cellular structure Polystyrene (Styrofoam, a trademark) Polyurethane ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e

Extruder Relationships Typical Pressure Gradient in an Extruder Extruder and Die Characteristic ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing 3/e