Forming Flashcards
What are the 4 different kinds of Bulk Deformation?
1) Forging
2) Rolling
3) Extrusion
4) Drawing
Advantages to Bulk Deformation
- No need to handle molten metal
- Very little material waste (if any)
Disadvantages to Bulk Deformation
- High forces required
- Machines and tooling is expensive (but is good for large production of parts)
What is Forging (definition)
Deformation is done with compressive forces applied through dies
What are the 5 different kinds of Forging?
1) Open Die
2) Closed die
3) Impression
4) Isothermal
5) Incremental
What is Open die forging?
Taking a cylindrical work piece and place it between 2 flat dies and press to reduce height
What is ideal deformation for Open die Forging
(homogenous deformation)
- volume remains constant
- reduction of height = increase in diameter
What happens in real life practice during Open die Forging
(Barreling)
- Caused by friction between material and die
- Can also be caused by thermal gradient between hot piece and cold die
What is Impression Die Forging
Workpiece acquires the shape of the die cavity while being deformed between 2 closed dies
Why is the flash gap important in Impression Die Forging
Because high pressure is generated in the filling of the cavity and it allows excess material to come out of the cavity
What is Closed die Forging
Workpice is completely surrounded by the dies
What could be a problem with Closed die Forging?
- Undersized volume of material won’t fill the cavity completely
- Oversized volume of material caused die failure and jamming
What is Isothermal Forging
The dies are heated up to the same temp as the hot workpiece
Advantages and Disadvantages to Isothermal Forging
Advantages:
- Materials flow easier within the die cavities
- no need to cool the parts
- complex parts with good dimensional accuracy can be made
Disadvantages:
-EXPENSIVE AS FUCKK
What is Incremental Forging?
When the blank is formed through several small steps
Compared to conventional forging, Incremental Forging…
- Requires much lower forces
- Is a quieter operation
- Similar parts can be forges using the same dies
Coining
Slug is shaped in a completely closed cavity
- high pressure (5-6 x flow stress) used to produce fine detail with no lubricants
Heading
Upsetting is performed at the end of a rod to produce a shape with a larger cross section
- Highly automated
- Can buckle if Length -> Diameter ratio is too high
Piercing (punching holes)
Punch with a specific shape indents the workpiece and creates a shaped cavity or impression
Piercing Force depends on
- cross sectional area of the punch
- flow stress of the material
- tip geometry
- friction at the surfaces
Hubbing
a hardened punch with particular geometry is pressed into a work piece to produce a cavity shallower than piercing
Cogging (drawing out)
Thickness of a bar is reduced by successive steps
ex) incremental forging
Fullering and Edging
Used to distribute material to a specific region of the workpiece prior to forging
Fullering - material is distributed away from an area
Edging - material is gatherd in a localized area
Roll Forging
Cross sectional area of a bar is reduced or altered in a shape by passing through a pair of grooved rolls
Skew Rolling
Similar to rolling, but used to make ball bearings
Name the 5 defects that could happen during bulk deformation
1) Cracking
2) Laps
3) Cold Shuts
4) Warping
5) Improper formed sections & dead zones
Cracking?
Excess stress or uneven distribution of it
Caused by
- poorly designed forging die
- excess material in the workpiece
- high thermal gradient between piece and die
Laps
Buckling of the part
Caused by
- too little material in the workpiece
Cold Shuts
Metal Flowing at different temperatures meet (don’t combine smoothly)
- indicated problem in the mold design with metal flow
Warping
Thinner sections cool faster than rest of forging
Improper formed sections & dead zones
- too little metal in the workspace
- flawed forging die design (incorrect material distribution)
Forging independent variables
- Material
- Starting geometry
- Lubrication
- Speed of deformation
- Amount of deformation
Forging dependent variables
- Force and power
- Exit temperature
- Dimensional precision
