What is Metal Drawing?
Definition: Metal drawing is a cold working process which is used to produce wires, rods, tubes, and other sections by pulling the metal through a die in order to reduce it to a desired shape and size.
Metal drawing is similar to metal extrusion, but the only difference is that the metal is pulled in the drawing process, while the metal is pressurized in an extrusion process.
In manufacturing, metal drawing process is used to manufacture parts of different cross sections like circular, square, rectangular as well as other cross sections can be produced using suitable metal drawing dies.
Hot and cold drawing, both can be done based on different applications. In the hot drawing process, the metal is first heated before its drawing operation, while in cold drawing, the metal is drawn at room temperature.
Having said that, let’s now discuss the types of drawing process in manufacturing.
Types of drawing process
There are mainly 3 types of metal drawing process in manufacturing.
Let me give you a few important insights regarding all these types of drawing process.
#1) Wire or Rod drawing
What is Wire Drawing?
Wire drawing (or bar drawing) is a bulk deformation operation of metals in which the cross section of the wire (or rod or bar) is reduced by pulling it through a die opening.
When the pulling of wire is done, the pressure is set up on the wire and its plastic deformation takes place which reduces its diameter.
The inner surface of the die is lubricated by using proper lubricant which reduces the friction during wire drawing.
In the beginning of the wire drawing operation, the end of the wire is first reduced and it is made into a point shape to insert it through the die opening.
This reduction of thickness at the end of wire is done by either hammering, rolling, filing or swaging operation.
This end is gripped with the help of a gripper and then its pulling is carried out.
There are basically 2 types of wire drawing techniques.
- Hot wire drawing: Hot wire drawing is generally used for drawing the wires which have higher thickness.
By heating the metal at higher temperature, they can be drawn with less force.
By hot wire drawing, the crystals are refined in the metal and the work-hardening of the metal does not take place.
- Cold wire drawing: The cold wire drawing is a wire drawing operation which is carried out at room temperature.
For most of the wire drawing operations, the cold wire drawing operation is preferred.
This is suitable for thin wires, as it requires less pulling forces.
By cold wire drawing, the material gets work-hardened and wires with good surface finish are obtained.
For more information on wire drawing, you can refer to the main article: What is Wire Drawing? (Its Types, Applications and More)
#2) Tube drawing
What is Tube Drawing?
Tube drawing (also known as tube sinking) is a metalworking technique in which the size of larger diameter tube is reduced to a smaller diameter by drawing a tube through a die.
High quality tubes with precise dimensions and good surface finish can be manufactured by using tube drawing.
In the beginning of the tube sinking process, one end is collapsed and fed through the die.
This end is clamped with the travelling carriage and the carriage is moved away from the die by hydraulic or mechanical means.
In tube sinking process, the lubricant is used to reduce the friction between the metal and the die.
The die material should be strong enough to resist the temperature and pressure of the metal.
So the dies used in tube drawing are made up of alloy steel or more often it is made of tungsten carbide.
There are mainly 5 types of tube drawing operations.
- Tube sinking
- Rod drawing
- Fixed plug drawing
- Floating plug drawing
- Tethered plug drawing
For understanding these tube drawing processes, I suggest you to refer its main article: What is Tube Drawing? (And what are its types?)
#3) Sheet metal drawing
What is sheet metal drawing?
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.
Generally, if the drawn part has depth more than its diameter, then it is referred to as a deep drawing.
The parts drawn by using a deep drawing process can have different cross sections like straight cross section, tapered cross section as well as cylindrical and rectangular parts can be drawn.
For deep drawing operation, the ductile metals like brass, copper, aluminum and mild steel show good drawability even at room temperature.
Few examples of sheet metal drawing are listed below.
- Soft drinks cans
- Kitchen sink
- Kitchen utensils
- Spray/perfume bottle
- Fuel tank of vehicle
- Metal sleeve
- Metal boxes and enclosure
For detailed information on sheet metal drawing, you should visit this main article: What is sheet metal drawing? (Explained with examples)