The different complexity of the geometric structure of forgings determines that the die forging process and die design are obviously different, and it is a necessary prerequisite to make clear the structural type of forgings for process design. General forgings are divided into three categories in the industry, and each category is further subdivided into three groups and nine groups.

Class I —— Forgings (mostly circular/rotary, square or similar in shape) with the main shaft standing in the die cavity and similar in two dimensions in the horizontal direction. The upsetting process is usually used for die forging of this kind of forgings. According to the different molding difficulty, it is subdivided into three groups.

I- 1 group: forgings formed by upsetting and light pressing, such as gears with little change in the height of hub and rim.

Group I-2: Forgings formed by extrusion, slight upsetting and extrusion, press-in and upsetting, such as universal joint forks and cross shafts.

Group I-3: Forgings formed by composite extrusion, such as hub shafts.

Class Ⅱ —— Straight long shaft forgings with the main shaft in the die cavity and long one-dimensional dimension in the horizontal direction. According to the different cross-sectional area of vertical spindle, it is subdivided into three groups.

Group II- 1 (the ratio of the maximum cross-sectional area to the minimum cross-sectional area) has little difference in the cross-sectional area of the vertical spindle, while Group II-2 (the ratio of the maximum cross-sectional area to the minimum cross-sectional area >: 1.6, which requires other equipment to blank in advance) forgings, such as connecting rods.

For group II-3 forgings with forked ends (one end or both ends), besides determining whether it is necessary to blank according to the above two groups, it is also necessary to reasonably design pre-forging steps, such as casing forks.

The first and second types of forgings generally adopt plane or symmetrical surface parting, and the asymmetrical surface parting increases the complexity of forgings.

Class Ⅲ-Forgings with the main shaft bent in the die cavity. According to the spindle trend, it is subdivided into 3 groups.

The spindle of group ⅲ- 1 bends in the vertical plane (the parting surface is a gently undulating surface or has a drop), but the plan view is straight and long (similar to class ⅱ), so it is generally unnecessary to design special bending steps to form forgings.

For group III-2 forgings, the main shaft is bent in the horizontal plane (the parting surface is generally flat), and the bending step must be arranged for forming.

Spatial bending of Ⅲ-3 group forgings and spindle (asymmetric surface parting).

There are also two or three types of forgings with high structural characteristics and complexity, such as most automobile steering knuckle forgings.