Metal Plastic forming Flashcards
DMM1: manufacture Deck 2
What are the three types of bulk forming?
Rolling , forging, extrusion(drawing)
What are the three types of sheet froming
Bending, pressing(e.g. shearing and punching) ,deep drawing(e.g. spinning)
Describe the rolling process
rollers are used to put pressure on a long billet of metal to reduce its cross sectional area and to change its shape
What is the difference between hot and cold rolling?
in hot rolling the billet is heated to be more complient but causes recystalization and the introduction of impurities which makes cold rolled metal stonger with a better finish
describe profile rolling
a series of rollers with differnt shapes are used to change the cross section of a linear billet into a specific shape
Describe ring rolling
a series of rollers expenda a small thick ring into a larger diameter with a smaller thickness and desired cross section
Describe extrusion forming
Extrusion involves forcing a metal billet through a die to produce a
continuous length with a consistent cross-section
When can extrusion be used?
batch production of simple cross sectioned parts made of ductile materials
What is the difference between forward, reverse and combination extrusion forming?
Forward: metal billet is forced through an die to form a part
Reverse: billet is forced into a solid die cause it be pushed backwards up out of the die
combinational pushes metals in both directions
Describe Drawing
A metal billet is pulled through a die with a tensile load to create the desired cross section
Describe closed die forging (5 stages)
1.Preform: a rough shape of the overall dimensions is made so the billet fits in the dies
2.First Impression: The primary metal movements creating simple shapes with large radii
3.Second Impression: Subsequent impressions refine the details of the
forging.
4.Final Impression: Excess material, , is squeezed out fromthe gaps between the top and bottom dies.
5.Trimming: flash is sheared off
What are draft angles?
Angles built into the design of a part so that it can easily be removed from a die or mould
What are the three types of presses used in forging?
Drop/falling hammer: energy of a falling pressure provides force
Hydraulic: high pressure is used to force the press
Screw press: rotating shaft with a piston provides force, energy is stored in flywheels
How is forging force determined?
F=nAY
F= force
n = factor from 2 -> 10 dependant of shape complexity
A = plan area of the forging including flash
Y = flow stress at the preheat temperature
Describe Open Die Forging
Hammer and anvil used to deform a hot billet of metal into the desired shape
