What is Sheet Metal Forming?
Definition: Sheet metal forming is a type of forming process in which the shaping of metal sheet is carried out without changing its mass, volume, or material composition.
Sheet metal forming is a special case of metal forming where the thickness of material is smaller than other dimensions (like length, width, etc) of the material.
In sheet metal forming, the thickness of the material can vary from very thin to somewhat thick. If the thickness of material is extremely thin, then it is called foil or leaf, and if the thickness of material is more than 6 mm, then it is considered a plate.
Having said that, let’s now discuss the different types of sheet metal forming process.
Types of sheet metal forming process
There are 3 different types of sheet metal forming process that are widely used in manufacturing industries.
Let’s see each of these sheet metal forming process one by one.
Sheet metal bending is a metal forming process in which a force is applied to a sheet metal piece, which ultimately causes it to bend at an angle to form a desired shape.
As shown in the above diagram, the deformation of sheet metal takes place in one direction. The sequence of different operations are performed to bend a sheet metal into a complex part.
Bending of sheet metal is used to form shapes like seams, corrugations, flanges, etc. The advantage of bending is that it provides stiffness to a material by increasing its moment of inertia.
The sheet metal bending is done on small parts (for example small brackets) as well as it is done on large components (like large enclosure).
In sheet metal forming, there are few terms used for the bending process. Let’s see these terms one by one.
- Bend line: Bend line is the straight line on the sheet metal surface that defines the start of bend and the end of level flange.
- Outside mold line: It is a line where the outside surfaces of the two flanges would meet.
- Flange length: The distance between the edge of the flange to the bend line is termed as flange length.
- Mold line distance: It is a distance between the end of the flange and the outside flange line.
- Setback: It is a distance between the outside mold line and either of the bend lines.
- Bend axis: Bend axis is the straight line around which the sheet metal is bent.
- Bend radius: Bend radius is the distance between the bend axis and the inner surface of the sheet metal.
- Bend length: Bend length is the length of the bend that is measured along the bend axis.
- Bend angle: The angle formed between the two flanges is called bend angle.
- Bevel angle: The complementary angle to the bend angle is known as bevel angle.
Sheet metal drawing is a metal forming operation in which the metal blank is stretched into a desired shape by the mechanical action of a punch.
The punch pushes the sheet metal blank downward and forces it into a die cavity which ultimately forms a shape of the desired part.
During the sheet metal drawing operation, the tensile forces cause the sheet metal blank to plastically deform into a cup shaped part.
For drawing operation, the ductile metals like brass, copper, aluminum and mild steel show good drawability even at room temperature.
Examples of sheet metal drawing are;
- Fuel tank of vehicle
- Soft drinks cans
- Kitchen sink
- Metal boxes and enclosure
- Spray/perfume bottle
- Kitchen utensils
- Metal sleeve
For detailed information on metal drawing, you should visit this main article: What is metal drawing? (What are its 3 types?)
Squeezing in sheet metal is a forming process in which the sheet metal is compressed with a high force such that it can flow through the entire cavity in the die.
Squeezing process is mostly suitable for ductile metals only.
Squeezing process includes sizing, coining, riveting, etc.
- Sizing: Sizing is a type of squeezing process in which the thickness of the sheet metal is reduced by application of compressive forces.
- Coining: Coining is a squeezing process which is used to manufacture coins by pressing a sheet metal between two dies (or between die and punch) having the impression of a coin.