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Compression molding

Compression molding. Presented by: Chandra Shekhar Thakur 2008 AMD 2927. Introduction . Molding is the forming process .

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Compression molding

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  1. Compression molding Presented by: Chandra ShekharThakur 2008 AMD 2927

  2. Introduction • Molding isthe forming process . • Compression molding process is followed by two step first one preheating and pressurizing • Compression molding is generally used for thermosetting plastic.

  3. History Initially plastic molding compound known as Florence compound. Its inventor, Alfred Critchlow, founded the Pro Corporation, Florence MA in 1847. Pro is said to be the first plastics molding company. Hand made mold for hand held mirror (c.1870) Image courtesy http://course1.winona.edu

  4. Trimming flash from Ekco radio cabinets (c.1934). Large scale compression molding press (c.1935). Image courtesy http://course1.winona.edu

  5. Process Description Image courtesy http://course1.winona.edu

  6. Stages in Compression molding cycle Image courtesy http://course1.winona.edu

  7. Parameters 1.The quantity of charge(molding material)put into the mold  2.Pressure of the molding process • Range of pressure 2000-3000 psi(13.8-20.7 MPa) [4] 3.Mold temperature • Temperature range 300ºF to 375ºF (149⁰C- 191⁰C)[4]. 4.Cure time variables. • The period required to harden thermosetting material to partial and complete polymerization is called cure time [4].

  8. Mold Image courtesy http://course1.winona.edu Press

  9. Types of compression molding Sheet molding compound(SMC) • Placing a reinforcement, such as a glass mat, between sandwiching layers of a thermoplastic Bulk molding compound(BMC) • Billet is used with efficiently placed and distributed long reinforcement

  10. Advantages • Lowest cost • More uniform density • Uniform shrinkage due to uniform flow • Improved impact strength due to no degradation of fibers during flow • Dimensional accuracy • Internal stress and warping are minimized

  11. Disadvantages • Curing time large • Uneven parting lines present • scrap cannot be reprocessed. Applications & products • Dinnerware • Buttons • Knobs • Appliance Housings • Radio Cases • Automotive exterior panels especially for commercial vehicles • ash trays & electrical parts

  12. Materials used in this process • Thermosetting polymers: • Fiber reinforced composite C)Thrmoplastic: • Ultra High Molecular Weight Polyethylene (UHMWPE) • Long Fiber reinforced Thermoplastics

  13. Material properties affected by the process • Density • Strength • Anisotropic property(fiber orientation) Fiber orientation induced by the material flow in the mold. Image courtesy [7] • Shrinkage and wrapage

  14. References 1 http://bsu.edu/web/jebutcher/compression_molding.htm 2 http://plastics.inwiki.org/compression_molding 3 Manufacturing Process forEngineering Materials, By SeropeKalpakjian & Steven R.Schmid, 4 Plastics Products Design Handbook   By Edward Miller, Society of Plastics Engineers • http://ticona.com/home/tech/processing/compression_molding 6 http://substech.com/compression_molding 7. http://madisongroup.com/publications/cae.pdf

  15. Thank you

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