Metal forming Flashcards
what are the basikc deformation processes for metal
rolling
forging
extrusion
drawing
what temperature is cold working preformed at
Ambient tempurature
what are the advantages of cold working
greater accuracy
close tolerances
better surface finish
higher strength and hardess
grain flow allows desirable directional properites
no heating equired
may eliminate secondary operations
disadvantages of cold working
high force/power required
starting workpeice must be free of scale/dirt
ductility/strain hardening limit amout of forming that can be completed
anneling may be required for further deformation
at what tempuratures is hot working preformed
above the recrystaization tempurature
what is the recrystalization tempurature
typically 50% of melting pointy in kelvin scale
a tempuratre where no strain hardening occurs and new grains areformed with mmo strain
what are the advantages of hot working
shape can be altered significantly
low force/power required
metals that cant handle cold work can be hot worked
strength properties are generally non directional
no work hardening occurs
disadvanages of hot working
lower dimensional accuracy
high energy required
work surface has oxidation/scale
poor surface finish
shorter tool life
at what tempuratures is warm working preformed
preformed above the amdient tempuare but below the recrystalization
what are the advantages of warm working
lower force/power then cold working
more intricate geometry possible
need for anneling may be reduced/eliminated
what is rolling
a processes in which the thicknessb of the work is reduced by compressive forces
most rolling is hpot rolling due to the large amount of deformation required
cold rolling can be preformed in the final stages of rolling
what is forging
a deformation processes in which the the work is pressed between 2 dies
forging facts
most forging is preformed hot
cold forging is used for certian products
what is the difference between a forge hammer an a forging press
forging hammer uses impact loads
forging press applies gradual pressure
what are the 3 types of forging operations
open die forging
impression die forging
flashless forging
what is open die forging
material is compressed between 2 flat dies
allows material to flow out in the x direction
creates simple shapes
what is impression die forging
preformed with dies that contain negive of desired shape
flash is formed as the metal nears its final position
impresson die forging facts
several steps required
not capable of close tolerances
seprate cavities required for each step
advantages of forging over maching
highe production rates
conservation of metal
greater part strength
favorable grain orrientation
what is flashless forging
metal being foorced into a completly enclosed die caviity
no flash is formed
what is important when it comes to flashless forging
material volume must equal die cavity volume
what is coining
special application of flashless forging
fine details are impressed onto top and bottom surfaces of workpeice
what is upset forging
a cylindrical workpeice decreases in length but increases in diameter
what is a common use of upset forging
forming heads on nails/bolts
what is extrusion in metals
material is forced to flow through a die opening with the the cross section shape the same as the die opening
what are the 3 types of metal extrusion
direct
indirect
impact
what is direct extrusion
the material is fored through the die opening by the ram
what is the main problem with direct extrusion
the significant amount of friction between the material and the walls of the container
what is indirect extrusion
the die is mounted on a. hollow ram and ram forces the material into the ram
hot extrusion advantages
reduces ram force
increases ram speed
reduces grain flow characteristics
what is impact extrusion
ram impacts the part at a high speed for a shot distanceas
what is drawing
similar to extrusion but the metal is pulled through a die
what are the 3 types of drawing
wire
bar
tube
what are the advantages of drawing
close dimensional control
good surface finish
improved strength and hardness
economical for mas production
what are the advantages of sheet metalworking
good dimensional accuracy
good surface finish
high strenghth
relitivly low cost with mass production
what are the 4 types of sheet metalworking
cutting
bending
drawing
other forming
what are the 4 types of cutting
shearing
blanking
punching
laser
what are the 3 stages of cutting
plastic deformatiobn
penetration
fracturwe
what is shearing
a sheet metal cutting operation along a straight line between 2 cutting edges
what is blanking
cutting sheet metal along a closed outline where the fallen peice is desired peice
what is the peice that is cut out dring blanking called
blank
what is punching
similar to blanking but the peice cut is scrap
what is cut off
seperating part with no excess waste
what is parting
seperating a part with excess waste
what is peircing
a punching operation in which a hole is cut out
what is slotting
simillar to periceing but a rectangular hole is cut
what uis notching
cutting a portion of metal from the edge of the sheet
what i ssemi notching
cutting a portion from inside the sheet
what is trimming
a cutting operation to remove excess metal from an established shape
what is shaving
shearing opration wth very small clearences
what is perforating
simeltanious punching operation
what is laser cutting
cutting using a highly cioncentrated beam of light
what is v bending
a punch looking like a v presses in to make a v shape
what is edge bending
pressure is held to part of the peice while the rest is bent with pressure being added
what are th esteps od the bending process
bend allowance
bending force
spring back
what is the neutral axis
a theoretical lime that stays the same during the bend
what is spring back
the elastic energy in the metal wanting to move back to original flat shape
what are 2 ways to comensate for spring back
overbending
bottoming
what some bending operations
hemming
seaming
curling
what is the drawing process for sheet metal
pressure is applied evenly on the blanka press add more force to bring the peice down into a hole to create the shape
hwat are sone common defects n drawn parts
wrinkling at flange
wrinking at wall
tearing
earing
surface scratches
what is reverse drawing
a secondary drawing process where part is flipped over
what is emosing
creates rassed letters or ridges
what is lacing
a combination of cutting and bending
what is the guerin process
uses a think rubber pad to form sheet over block
what are some advantages of the Guerin process
low tool kcost
form block can be made out of alot of different products
rubber pad can be used on may different peices
process attractive in small quantity production
what is the disadvantage of the guerin process
onlly relivily low forces can be applied
whatv is hydroforming
similar to the Guerin process but the rubber pad is switched o wiyh hydraloc fluid
what are the advantages of hydroformin
good for high production
setup can be used more then once
deeper draws can be achieved
uniform pressure creates uniform wall tickness and prevents thickness
what is the disadvanteage of hydroforming
relitivly high tool cost
what is strectch forming
metal stretched and symoltaniously bent
what is roll bending
large metal sheets are formed into curved sections using rollers
what is roll formming
continuios bending in which opposing rules produce long sections
what is spinning
a method in which the material is clamped and rotated in which it is gradually shaped around a mandrel
