Nov 27 Plastics - Coursepack ME 250 Processing of Plastics...

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ME 250 Nov 27, 2007 Processing of Plastics Coursepack Section: 13.6 (Injection molding) 13.6.1 – 13.6.5 Section: 13.8 (Blow molding) 13.8.1, 13.8.2 Sections: 13.9 (Thermoforming) 13.10 (Casting-one para) 13.12 (Design issues) Plastics industry Plastics industry contributed $341Billion to the U.S. economy (1.1M jobs) Ranks amongst the top manufacturing industries Plastics play an indispensable role in variety of markets including packaging, construction, home goods, electronics, etc. Advantage of Plastics Almost unlimited variety of part geometries Plastic molding is a net shape process – Further shaping is not needed Less energy is required than for metals due to much lower processing temperatures – Handling of product is simplified during production because of lower temperatures Painting or plating is usually not required Comparing engineering materials + ++ + + +++ joining no + + +++ + +++ Ceramics + ++ +++ +++ recycle + +++ +++ + coloring no + +++ + Polymers Yes/no some + +++ Composites no +++ +++ +++ Glass +++ + +++ ++ Metals conductor? corrosion resistance forming strength/ weight material from Oct 25 lecture Compared to metals Low strength and stiffness – Plastics are not as strong or stiff as metals – Strength-to-weight ratios for some plastics are competitive with metals in certain applications
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