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Introduction to Manufacturing. Chapter 14: Forging. Forging. Metal-forming process in which the workpiece is shaped by compressive forces applied through various dies and tools. Forging. Cold Forging
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Introduction to Manufacturing Chapter 14: Forging
Forging • Metal-forming process in which the workpiece is shaped by compressive forces applied through various dies and tools. Engr 241-R1
Forging • Cold Forging • Requires greater forces and workpiece materials must have sufficient ductility at room temperature; good surface finish and dimensional accuracy. • Hot Forging • Requires smaller forces, not as good finish or dimensional accuracy; usually require additional machining. Engr 241-R1
Forging • Forgeability • Capability of a material to undergo deformation without cracking. • Forging is a discrete (individual) parts process • Forging is a near net shape process Engr 241-R1
Open-Die Forging • (upsetting or flat-die forging) • Simplest forging process. • Solid workpiece is set between two flat dies and reduced (height) through compression. • Barreling (outward bowing of material) minimized with the use of lubricants. Engr 241-R1
Cogging: • Drawing out • Operation where the thickness of a bar is reduced by successive forging steps at certain intervals. • Typical for parts such as I-beams which must be pre-shaped before rolling Engr 241-R1
Impression-Die Forging • Work piece forms in between shape of die cavities (impressions). • Flash: material which flows out from dies (frictional resistance causes material to fill the inside of the die cavity). Engr 241-R1
Impression-Die Forging (Cont.) • blank (part which has been cropped or cut from bar stock). • blocking (rough shaping with dies). • finishing (using impression dies, forging the final part shape). • trimming (removing the flash). Engr 241-R1
Closed-Die Forging • flashless forging (flash does not form). • workpiece completely fills the die cavity. Volume of material is precise. • Precision Forging: near-net-shape, net-shape forging – (volume control – gears, connecting rods) • Coining: pressures five to six times the strength of material. Engr 241-R1
Related Forging Operations • Heading • upsetting operation, usually performed at the end of a round rod or wire to produce a large cross section (bolts, rivets); warm, cold, or hot process. (Fig. 14.11) • Piercing • indenting, without breaking, the surface of a workpiece with a punch to produce a cavity or an impression (pressure is usually 3-5 times the strength of material). (Fig. 14.12) Engr 241-R1
Related Forging Operations • Hubbing • pressing a hardened punch into the surface of a block of metal to produce a cavity (create dies for tools, tableware, etc.). • Roll Forging • the cross section of a bar is reduced or shaped by passing it through a pair of rolls with shaped grooves (leaf springs, hand tools). (discrete parts) Engr 241-R1
Related Forging Operations • Skew Rolling • similar to roll forging • Ball bearing production • Orbital Forging • upper die moves along an orbital path above the part which is also spinning. Engr 241-R1
Related Forging Operations • Incremental Forging • process where a blank is forged into a shape in several small steps (the die penetrates the blank at different depths across the surface). Similar to cogging. • Isothermal Forging • Hot die forging Engr 241-R1
Related Forging Operations • Rotary Swaging • Radial Forging (circular shaped parts) • Use reciprocating dies controlled by a cam • Tube swaging • Mandrel and dies Engr 241-R1
Forging Machines • Presses • hydraulic • mechanical • screw • Hammers • gravity drop • power drop • Counterblow (two hammers) • high-energy-rate Machines (pneumatic) Engr 241-R1