Forging process size design and process selection are carried out at the same time, therefore, in the design of process size should pay attention to the following points:
(1) Follow the law of constant volume, the design process size must conform to the key points of each process; After a certain process, the volume before the process is equal to the total volume after the process. The so-called total volume refers to the volume of the semi-finished products obtained in the forging process and the volume of the material loss occurring in the process.
(2) It is necessary to estimate the change of some size of billet in the process of deformation in each process, and keep enough shrinkage and insurance amount to avoid the size out of tolerance. For example, punching will reduce the gross bad height, and the height of billet will increase when reaming.
(3) The size of the semi-finished product obtained in one process should enable the next process to proceed smoothly. For example, after pulling long upsetting, can not pull too long, otherwise forging upsetting will be unstable bending.

(4) when forming parts, it is necessary to ensure that each part of the forging has enough volume.
(5) When forging with multiple fires, the possibility of heating in the middle of each fire should be considered, such as considering the process size, the middle fire, whether the semi-finished products can be placed in the furnace face for heating and other issues.
(6) Enough last forgings must be corrected to make the forging surface smooth and the length and size appropriate.
For long shaft forgings when the length direction size is very accurate, it must be estimated that the length size will be slightly extended when dressing.
For shaft forgings in the cutting head to comply with the provisions.