Chapter12_Shpg+Rmgb

Chapter12_Shpg+Rmgb - Chapter 12 Shaping, Forming and...

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Chapter 12 Shaping, Forming and Material emoval Removal
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anufacturing Manufacturing • Definition: manufacturing, in its broadest sense, is the process of converting raw materials into product – Design of the product – Selection of the raw material – The sequence of processes through which the product will be manufactured • Typical manufacturing methods include – Casting – Forming (Powder Metallurgy and Forging) and Shaping – Machining – Joining – Finishing spection, assembly if required, and testing typically follow Inspection, assembly if required, and testing typically follow
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Recommended Reading • Callister p. 565-569, 471-484 ERO3700 course pack: p. 336- 94, 312- AERO3700 course pack: p. 336 394, 312 335, 425- 454
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Shaping of Plastics Shaping of Ceramics Shaping Metals Material Removal
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haping Plastics Shaping Plastics hermoplastic rming temperatures Thermoplastic - forming temperatures are relatively low and can be reformed hermosets uring occurs during the • Thermosets - curing occurs during the process, need higher temperatures and nger time longer time • Callister, p. 565-569
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jection Molding for Thermoplastics Injection Molding for Thermoplastics • Granular or powder material is fed into a heated cylinder or barrel. reciprocating screw moves the material toward the A reciprocating screw moves the material toward the die, material softens at same time. • Plasticized material (viscous liquid) accumulates at the die entrance. • Once accumulated, the correct amount of material is injected into the die. • Injection pressure of 30 – 100 MPa minimizes cooling shrinkage and reduces porosities.
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Advantages and Disadvantages Advantages High quality, high production rate elatively low labour cost Disadvantages High capital cost of machines lose process control is Relatively low labour cost Good surface finish Highly automated Intricate parts can be made Close process control is needed
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Thermoforming of Thermoplastics • Uses thermoplastics in sheet or film form reform) ostly for R&D (preform) – mostly for R&D • Heat + pressure with shaped mold teps • Steps – Sheet is heated to the sag point (< Tmelt) – Sheet is placed over mold – Vacuum is applied – Weight of sheet may be enough or force may be eeded in high curvature areas Sheet is pulled needed in high curvature areas. Sheet is pulled down against mold – Mold is at room temperature so part cools quickly
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Thermoforming of Thermoplastics ooling is inexpensive Tooling is inexpensive, often made of Al alloys uality concerns Quality concerns – Tearing – Non-uniform wall thickness – Improperly filled molds – Poor surface detail
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ompression Molding sually used for thermosets Compression Molding Usually used for thermosets • Resin is loaded in a heated mold with ne or more cavities one or more cavities • One side of the mold is forced down on the resin. Pressure is applied. Liquid resin fills cavities • Continued heating completes cross- linking
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Compression Molding Advantages
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Chapter12_Shpg+Rmgb - Chapter 12 Shaping, Forming and...

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