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 Hot 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 Forging is a discrete (individual) parts process 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 Hammers hydraulic mechanical screw gravity drop power drop Counterblow (two hammers) high-energy-rate Machines (pneumatic) Engr 241-R1