The feed line height of the material is the height from the bolster plate surface to the movement position of the material, as is shown in Fig. 1. This may also be referred to as "feed level" or "path line". In the case of a press die for carrying out automatic forming using a material feeding device, it is necessary to make both the die height and the feed line height match with the press machine.

The feed line height of a press die is shown in Fig. 2. This is the distance from the top surface of the bolster plate (bottom surface of the die holder) to the position to which the material has been lifted up from the die surface.

The feed line height of a press die is shown in Fig. 2. This is the distance from the top surface of the bolster plate (bottom surface of the die holder) to the position to which the material has been lifted up from the die surface.

Lifting up occurs unavoidably in the forming of products that includes forming operations such as bending, etc. The forming of the product is done after pressing the material down from the lifted up state down to the die surface. At this time, if the amount of lift is large the inclination of the material becomes large causing defects in forming. At the time of designing the die care should be taken to ensure that the amount of lift is as small as possible.

If the amount of lift has become large unavoidably, the position of the feed line height of the press machine is set to the position of about half the amount of lift. By doing so, the material tilts slightly upward at the time of feeding the material. At the time of forming the product, the material is pressed down by the top die, the material that has tilted upward first becomes flat (when equal to the feed line height of the press machine), and then starts tilting downward from that state and comes into contact with the die surface. Compared to the normal setting of the feed line height, it is possible to make the tilt small of the material during product forming, and it is also possible to reduce defects in forming.