Introduction to Manufacturing Chapter 14 Forging Engr 241

Introduction to Manufacturing Chapter 14: Forging Engr 241 -R 1

Forging • Metal-forming process in which the workpiece is shaped by compressive forces applied through various dies and tools. Engr 241 -R 1 1

Example – Blacksmith Hammer and anvil Engr 241 -R 1 2

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 -R 1 3

controlled – parts have good strength • Landing gear • Jet engine shafts • Bolts • Connecting rods • Hand tools Engr 241 -R 1 4

Forging classified cold or hot Engr 241 -R 1 5

Cold Forging • Requires greater forces and workpiece materials must have sufficient ductility at room temperature; good surface finish and dimensional accuracy. Engr 241 -R 1 6

Hot Forging • Requires smaller forces, not as good finish or dimensional accuracy; usually require additional machining. Engr 241 -R 1 7

Open-Die Forging Upsetting or flat-die forging • Simplest forging process. • Solid workpiece is set between two flat dies and reduced (height) through compression. • Engr 241 -R 1 8

Barreling outward bowing of material • Two causes • 1. ) by friction at die-work piece interface • minimized by use of lubricants. • Engr 241 -R 1 9

Barreling (2) by hot work piece between cold dies • Material cools at die interface and resists deformation • Engr 241 -R 1 10

Cogging: Drawing out • Operation where 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 -R 1 11

Fullering • Distribute material away from die Engr 241 -R 1 12

Edging • Gather material into die Engr 241 -R 1 13

Impression-Die Forging • Work piece takes shape of die cavities (impressions). • Flash: material which flows out from dies (frictional resistance from cooling flash causes material to fill the inside of the die cavity). Engr 241 -R 1 14

Closed-Die Forging • • Also called precision forging flashless forging (flash does not form). workpiece completely fills the die cavity. Volume of material is precise. Economical - eliminates trimming flash Engr 241 -R 1 15

Closed die forging (cont. ) Greater forces to obtain fine detail • Al and magnesium good because malleable • Less material wasted • Gears, connecting rods, etc. • Engr 241 -R 1 16

Coining: Another closed die process • Produces fine details • No lubricants used – can be trapped in die cavities – don’t compress • pressures five to six times the strength of material. • Engr 241 -R 1 17

Related Forging Operations Engr 241 -R 1 18

(1) Heading • • upsetting operation, usually performed at the end of a round rod or wire to produce a large cross section heads of bolts, screws nails, rivets, etc. Engr 241 -R 1 19

(2) Piercing • indenting, without breaking, the surface of a workpiece with a punch to produce a cavity or an impression Engr 241 -R 1 20

(4) 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 -R 1 21

(5) Skew Rolling similar to roll forging • Ball bearing production • Engr 241 -R 1 22

(6) Orbital Forging • upper die moves along an orbital path above the part which is also spinning. Engr 241 -R 1 23

(7) 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. Engr 241 -R 1 24

(8) Isothermal Forging Hot die forging • Dies heated to same temp as workpiece • Good for complex parts with dimensional accuracy • Engr 241 -R 1 25

Forging die design • Most important rule in die design • • Work piece material must flow in direction of least resistance Machining allowance used Engr 241 -R 1 26

Die inserts Separate sections • Reduce cost of making dies • Engr 241 -R 1 27

Die lubricants Slow rate of cooling • Improve metal flow • Serve as parting agent • Not for coining – precision forging • Engr 241 -R 1 28

Forging Machines Engr 241 -R 1 29

Presses Hydraulic • Mechanical • Screw • Engr 241 -R 1 30

Hammers Gravity drop – free falling ram • Power drop – stroke accelerated by steam, air, or hydraulic • Engr 241 -R 1 31

Hammers (cont. ) Counterblow (two hammers simultaneously approach each other • High-energy-rate machines - ram accelerated by high pressure – part forged in one blow • Engr 241 -R 1 32