Slide-Set-11-Injection-Molding

Slide-Set-11-Injection-Molding - Slide Set 11Injection...

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Unformatted text preview: Slide Set 11Injection Molding Operations Injection Dr. Anthony Brennan University of Florida Department of Materials Science & Department Engineering Engineering EMA 4161C - Polymer Physical Properties 1 Learning Objectives Learning • Injection Molding Injection Equipment Equipment • Injection Molding Injection Cycles Cycles • Injection Molding • Injection Molding Ma – Orientation – Properties • • Mold Designs Troubleshooting EMA 4161C - Polymer Physical Properties 2 Machine and Process Cycles Machine EMA 4161C - Polymer Physical Properties 3 Injection molding machine Injection EMA 4161C - Polymer Physical Properties 4 EMA 4161C - Polymer Physical Properties EMA 5 4 Cycles of Injection Molding Cycles • Filling Phase – “Plasticated” plastic Filling pumped into mold pumped • Packing Phase – Pressure applied to Packing induce compaction and solidification in mold mold • Cooling and Plasticating Phase – Cooling Solidification of plastic completed, plastic continually “melted/plasticated” plastic • Part ejection – mold separates and part Part ejected ejected EMA 4161C - Polymer Physical Properties 6 Filling Phase • “Plasticated” plastic pumped Plasticated” into mold into • Pressure flow output EMA 4161C - Polymer Physical Properties 7 Packing Phase • Pressure applied to induce Pressure compaction and solidification in mold mold • Stress relaxation, cooling effects Stress on solidification and shrinkage on EMA 4161C - Polymer Physical Properties 8 Cooling and Plasticating Phase • Solidification of plastic Solidification completed, plastic continually “melted/plasticated” “melted/plasticated” EMA 4161C - Polymer Physical Properties 9 Part ejection • Mold separates and part Mold ejected ejected • HDT defines solidification HDT necessary for part removal necessary EMA 4161C - Polymer Physical Properties 10 Morphology of molded parts Morphology Transcrystalline, Spherulitic zones EMA 4161C - Polymer Physical Properties 11 Influence of Processing on Morphology – Filling Phase Morphology • Consider the Consider influence of shear on the orientation of plastic during mold filling operation. operation. EMA 4161C - Polymer Physical Properties 12 Influence of Processing on Morphology – Packing Phase Morphology • Crystallization Crystallization nucleated on surface of mold – transcrystalline zone zone • High density, rapid High growth, Regime 2 & 3 (Hoffman) (Hoffman) • Center cools Center slower than surface surface • Spherulites in Spherulites center center EMA 4161C - Polymer Physical Properties 13 Influence of Processing on Morphology – Cooling Phase of PP Morphology MOLD Temperature 175° C Melt Temp 210° C 245° C 15°C 75 °C • Time at Time temperature temperature • Cooling rate • Correlation to Correlation growth rates of crystals crystals • Effect on Effect mechanical properties. properties. EMA 4161C - Polymer Physical Properties 14 Part shrinkage and strength as a function of process function EMA 4161C - Polymer Physical Properties 15 Characterization of Molded Parts – Effect of Anisotropy Effect • PMMA – amorphous • Birefringence – Birefringence absolute difference between RI in parallel and perpendicular perpendicular • Correlate with Correlate toughness – Griffiths crack energy crack • Correlate with Correlate Shrinkage in a disk as a function of ram speed (injection speed) for PS speed) EMA 4161C - Polymer Physical Properties 16 Characterization of Molded Parts – Shrinkage Shrinkage • PS – PS amorphous amorphous • Longitudinal Longitudinal shrinkage versus melt temperature from surface to center center • Transverse Transverse (thickness) shrinkage shrinkage EMA 4161C - Polymer Physical Properties 17 Characterization of Molded Parts – Effect of Ram Speed Effect • GPS – amorphous • Orientation as a Orientation function of Ram speed: Mold T = 50°C 50 • Change in film Change (part) thickness: Mold T = 25°C Mold EMA 4161C - Polymer Physical Properties 18 Tensile strength as a function of orientation orientation • GPS – GPS amorphous, glass filled PS filled • Parallel – high Parallel orientation in machine direction machine • Perpendicular Perpendicular transverse transverse EMA 4161C - Polymer Physical Properties 19 Notched Izod strength as a function of orientation function • GPS – GPS amorphous, glass filled PS filled • Parallel – high Parallel orientation in machine direction machine • Perpendicular – Perpendicular transverse transverse • Elimination of Elimination orientation orientation EMA 4161C - Polymer Physical Properties 20 Shrinkage for various plastics Shrinkage • PMMA - amorphous • LDPE, PP, Acetal, LDPE, Nylon – crystalline or semi-crystallline or • Shrinkage due to Shrinkage crystallization crystallization • CTE effects relative CTE to phase transition temperatures temperatures EMA 4161C - Polymer Physical Properties 21 Processing effects on shrinkage Processing • PMMA - amorphous • LDPE, PP, Acetal, LDPE, Nylon – crystalline or semi-crystallline or • Shrinkage due to Shrinkage crystallization crystallization • CTE effects relative CTE to phase transition temperatures temperatures EMA 4161C - Polymer Physical Properties 22 Processing effects on shrinkage Processing • Effects of Effects orientation correlated with Shrinkage as a function of ram speed and melt temperatures temperatures EMA 4161C - Polymer Physical Properties 23 Processing effects on shrinkage Processing • Shrinkage as a Shrinkage function of part thickness thickness • Influence of Influence mold temp on shrinkage in MD and TD and • Consider Consider differences in part thicknesses thicknesses EMA 4161C - Polymer Physical Properties 24 Normal Stresses – Die Swell Do Die Swell in Parison is Die given by: given D1 B1 = D1 / Do L1 Die Swell in Parison Die Wall thickness is given by: by: Do D2 B2 = H1 / H o L2 07/17/11 07/17/11 EMA 4666C - Polymer Processing Copyright EMA Protected Protected 25 Mold designs Mold EMA 4161C - Polymer Physical Properties 26 EMA 4161C - Polymer Physical Properties EMA 27 EMA 4161C - Polymer Physical Properties EMA 28 EMA 4161C - Polymer Physical Properties EMA 29 EMA 4161C - Polymer Physical Properties EMA 30 EMA 4161C - Polymer Physical Properties EMA 31 Sprue/runner designs Sprue/runner EMA 4161C - Polymer Physical Properties 32 EMA 4161C - Polymer Physical Properties EMA 33 EMA 4161C - Polymer Physical Properties EMA 34 EMA 4161C - Polymer Physical Properties EMA 35 EMA 4161C - Polymer Physical Properties EMA 36 EMA 4161C - Polymer Physical Properties EMA 37 EMA 4161C - Polymer Physical Properties EMA 38 Mold designs Mold EMA 4161C - Polymer Physical Properties 39 EMA 4161C - Polymer Physical Properties EMA 40 EMA 4161C - Polymer Physical Properties EMA 41 EMA 4161C - Polymer Physical Properties EMA 42 EMA 4161C - Polymer Physical Properties EMA 43 EMA 4161C - Polymer Physical Properties EMA 44 EMA 4161C - Polymer Physical Properties EMA 45 EMA 4161C - Polymer Physical Properties EMA 46 EMA 4161C - Polymer Physical Properties EMA 47 EMA 4161C - Polymer Physical Properties EMA 48 EMA 4161C - Polymer Physical Properties EMA 49 Summary • Four primary phases of injection Four molding process. molding • Output is a function of Cp, dT, mass, Output Pressure Pressure • Runner design varies from cold to hot Runner systems systems • Part geometry critical for mold flow Part control control • Key factor analysis required 50 50 References • Introduction to Physical Polymer Science, 4th Edition, Lesley H. Sperling, Wiley Interscience (2006) ISBN 13 978Lesley 0-471-70606-9 • Principles of Polymer Chemistry, P.J. Flory (1953) Cornell Principles University Press, Inc., New York. University • The Physics of Polymers, Gert Strobl (1996) SpringerVerlag, New York. • Some figures were reproduced from: Polymer Processing Some Fundamentals, Tim A. Osswald (1998), Hanser/Gardner Publications, Cincinnati, OH. Publications, • Figures were reproduced from Polymer Physics, (1996) Figures Ulf Gedde, Chapman & Hall, New York. Ulf 51 51 ...
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This note was uploaded on 07/17/2011 for the course EMA 4161c taught by Professor Staf during the Fall '10 term at University of Florida.

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