Stamping in Automobile Manufacturing: Deep Interpretation

Cars are called “machines that change the world”.

Because the automobile industry has a strong industrial correlation, it is regarded as an important symbol of a country’s economic development level.

The automobile has four major processes.

The stamping process, as the top priority of the four processes, is also the first of the four processes.

What is stamping?

Stamping is a forming and processing method of applying an external force to plate, strip, pipe and profile by press and die to produce plastic deformation or separation, so as to obtain the workpiece (stamping part) with the required shape and size.

Stamping and forging belong to plastic processing (or pressure processing), collectively known as forging.

The billets for stamping are mainly hot-rolled and cold-rolled steel plates and strips. 60 ~ 70% of the steel in the world is the plate, most of which is made into finished products by stamping.

What is stamping

The automobile body, chassis, oil tank, radiator sheet, boiler drum, container shell, iron core, and silicon steel sheet of motor and electrical appliances are all stamped.

There are also a large number of stamping parts in instruments, household appliances, bicycles, office machinery, household utensils, and other products.

Stamping characteristics

1) Stamping is a processing method with high production efficiency and low material consumption.

The stamping process is applicable to the production of large quantities of parts and products, which is convenient to realize mechanization and automation and has high production efficiency.

2) The operation process is convenient and does not require the operator to have a high level of skill.

3) The stamped parts generally do not need to be machined and have high dimensional accuracy.

4) Stamping parts have good interchangeability. The stability of stamping processing is good. The same batch of stamping parts can be used interchangeably without affecting assembly and product performance.

5) Because the stamping parts are made of plates, their surface quality is good, which provides convenient conditions for subsequent surface treatment processes (such as electroplating and painting).

6) Stamping can obtain parts with high strength, high stiffness and lightweight.

7) The cost of stamping parts produced in batch by die is low.

8) Stamping can produce complex parts that are difficult to be processed by other metal processing methods.

Stamping process

Mechanical steering system takes the driver’s physical strength as the steering power source, in which all mechanical transmission structures are mechanical.

Mechanical steering system consists of steering control mechanism, steering gear and steering transmission mechanism.

Stamping process

A. Separation process

The sheet metal is separated along a certain contour line under the action of external force to obtain finished and semi-finished products with certain shape, size and cutting section quality.

Separation condition: the stress inside the deformed material exceeds the strength limit σb.


Use a die to cut along the closed curve, and the blanking part is a part. It is used to manufacture flat parts of various shapes.


Use the die to cut along the closed curve, and the blanking part is waste. There are positive punching, side punching, hanging punching and other forms.


Trim the edges of formed parts neatly or cut into a certain shape.


The separation is produced by punching along the unclosed curve with a die.

When the left and right parts are formed together, the separation process is used more.

B. Forming process

The blank produces plastic deformation without fracture to obtain finished and semi-finished products with certain shape and size.

Forming condition: yield strength σ S < internal stress of material < strength limit σ b。


The blank is formed into various open hollow parts.


The edges of sheet metal or semi-finished products are formed into vertical edges according to a certain curvature along a certain curve.


A forming method used to improve the dimensional accuracy of formed parts or obtain small fillet radius.

Hole turning

Make vertical edges on pre-punched plates or semi-finished products or non punched plates.


Bending the sheet metal into various shapes along a straight line can process parts with extremely complex shapes.

Forming process

Flow chart of the stamping process

Flow chart of the stamping process

Stamping die

Mold is known as “the driving force of entering a rich society” in Japan and “the emperor of metal processing industry” in Germany.

The level of mold design and manufacturing technology is one of the important symbols to measure the level of a country’s product manufacturing.

Mold classification

According to the working principle, it can be divided into:

Basic structure of die

Stamping dies are usually composed of upper and lower dies (male and female dies)

Basic structure of die

Composition: 1 working part, 2 guide, 3 positioning, 4 limit, 5 elastic element, 6 lifting and turnover

Stamping equipment

1. Press machine

1) According to the bed structure, the press can be divided into open press and closed press

Press machine

The open press is open on three sides, the bed is C-shaped, and the rigidity is poor. It is generally used for small presses;

The front and rear sides of the closed press are open, the bed is closed, and the rigidity is good. It is generally used for large and medium-sized presses.

2) Press can be divided into the mechanical press and hydraulic press according to the type of driving slider force

Type Equipment name Working principle Characteristic
Mechanical press Friction press The friction disc and flywheel contact each other and transmit power, and work with the help of the relative motion principle of screw and nut. The structure is simple. When overloaded, it will only cause the sliding between the flywheel and the friction disc without damaging the parts, but the flywheel rim is worn greatly and the productivity is low. It is suitable for stamping of small and medium-sized parts, especially for stamping processes such as correction, stamping and forming.
Crank press The crank connecting rod mechanism can be divided into open type and closed type. High productivity, suitable for all kinds of stamping processing
Hydraulic press Hydraulic press Based on Pascal principle, water or oil is used as the working medium and static pressure transmission is used to make the sliding block move up and down. High pressure and static pressure, but low productivity. It is suitable for deep drawing, extrusion and other forming processes

2. Uncoiling line

Uncoiling line

3. Plate shears

Plate shears are mainly used to cut straight edges of metal plates of various sizes.

The transmission forms are mechanical and hydraulic.

Stamping material

Stamping material is an important factor affecting part quality and die life.

At present, stamping materials include not only low carbon steel, but also stainless steel, aluminum and aluminum alloy, copper and copper alloy.

Steel plate is the most widely used raw material in automobile stamping.

At present, with the requirements of body lightweight, new materials such as high-strength steel plate and sandwich steel plate are increasingly used in automobile body.

1. Steel plate performance requirements

1) It has good mechanical properties and large deformation capacity.

The mechanical properties of metal materials refer to tensile strength, yield strength, elongation, hardness and plastic strain ratio.

  • High plastic strain ratio R (anisotropic property)
  • High work hardening index n value;
  • High elongation δ;
  • Low yield ratio( σ s/ σ b);
  • Low aging index.

2) Good surface quality

The steel plate surface shall be free of obvious defects such as scabs, cracks, inclusions and scratches.

The inner panel of the vehicle body is allowed to have defects that do not affect the formability and paint adhesion, such as small bubbles, small scratches, small roll marks, slight scratches and slight oxidation color;

The outer plate shall meet the quality level of FD (O5), that is, the better one of the two sides shall not have any defects, that is, it shall not affect the appearance quality after painting or electroplating, and the other side shall meet the requirements of FB (O3).

2. Steel plate classification

1) Divided by thickness:

Thick plate (more than 4mm), medium plate (3-4mm) and thin plate (less than 3mm). The stamping parts of the automobile body are mainly thin plates.

2) According to rolling status:

Hot rolled steel plate and cold rolled steel plate.

Hot rolling is to soften the alloy at a temperature higher than the recrystallization temperature and then press the material into a thin sheet or billet cross-section with a pressure roller to deform the material, but the physical properties of the material do not change.

The toughness and surface flatness of hot rolled plates are poor and the price is low. Hot rolling is rough and can’t roll very thin steel.

Cold rolling is the process of further rolling the material with a roller at a temperature lower than the alloy recrystallization temperature for the material that has gone through the hot rolling, pitting and oxidation processes, so as to make the material recrystallize.

After repeated cold pressing recrystallization annealing cold pressing (repeated 2 ~ 3 times), the metal in the material changes at the molecular level (recrystallization) and the physical properties of the formed alloy change.

Therefore, it has good surface quality, high finish, high dimensional accuracy, and the performance and organization of the product can meet some special application requirements.

Cold-rolled steel plates mainly include: cold-rolled carbon steel plates, cold-rolled low-carbon steel plates, cold-rolled steel plates for stamping, high-strength cold-rolled steel plates, etc.

Cold-rolled carbon steel sheet

Grade Application
SPCC General use
SPCD For stamping
SPCE, SPCEN For deep stamping

S is the abbreviation of steel, P is the abbreviation of plate, the third letter C is the abbreviation of cold, and N indicates that non-timeliness needs to be guaranteed.

Cold-rolled low carbon steel sheet

Grade Application
DC01 General use
DC03 For stamping
DC04 For deep stamping
DC05 For special deep stamping
DC06 For super deep stamping

Inspection tool

Inspection fixture is a piece of special inspection equipment used to measure and evaluate the dimensional quality of parts.

In automobile manufacturing, whether for large stamping parts, interior trim parts and welding sub-assemblies with complex spatial geometry or for simple small stamping parts and interior trim parts, special inspection tools are often used as the main inspection means to control the product quality between processes.

The inspection tool has the advantages of being fast, accurate, intuitive and convenient, especially suitable for the needs of mass production.

The inspection tool usually consists of three parts:

① Skeleton and base part;

② Type part;

③ Functional parts (functional parts include: quick chuck, locating pin, detection pin, movable clearance slider, measuring table, profile card, etc.).

Inspection tool

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