Group II-1 forgings with little difference in cross-sectional area perpendicular to the main axis (the ratio of maximum cross-sectional area to minimum cross-sectional area is less than 1.6, and other equipment can not be used for blank making).
Group II-2 forgings with large difference in cross-sectional area of vertical main axis (the ratio of maximum cross-sectional area to minimum cross-sectional area is > 1.6, and other equipment is required for blank making in front), such as connecting rod, etc.
For forgings with fork / branch shape at the end (one or both ends) of group II-3, in addition to determining whether blank making is required according to the above two groups, pre forging steps must be reasonably designed, such as casing fork, etc.
Class I and II forgings are generally plane parting or symmetrical surface parting, and asymmetric surface parting increases the complexity of forgings.
Class III(metal forging parts) - Forgings with tortuous main axis and lying in the die bore. It is subdivided into 3 groups according to the main axis trend.
Group III-1 main axis is bent in the vertical plane (the parting surface is a gently undulating curved surface or with drop), but the plan is a straight long axis shape (similar to class II). Generally, forgings can be formed without designing special bending steps.
Group III-2 forgings whose main axis is bent in the horizontal plane (the parting surface is generally plane) and can only be formed by arranging bending steps.
Group III - 3 forgings whose main axis is space bending (asymmetric surface parting).
There are also forgings with two or three types of structural features and higher complexity, such as most automobile steering knuckle forgings.(metal forging parts)