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#103 Fundamentals of Press Die Structure Design (12) Relationship Between a Lifter and its Hole

Category : Die Design
November25, 2011

Lifters (including stock guide lifters) are parts used for maintaining the level of the work to be formed from the surface of the die. These are parts that are always used in combination with a spring and a screw plug. Therefore, it is easy to use if the relationship with the hole of the set of the lifter body, the spring, and the screw plug is properly adjusted.

Fig. 1 is an example showing the relationship between the lifter and the hole. This is explained below.
With respect to the shaft (D) of the lifter, the dimension of the hole (D1) is set so that there is not too much play between them. If there is too much play between the shaft and the hole, the shaft shakes and holding of the work to be formed becomes unstable. If the play is too small, the movement of the lifter becomes bad due to the penetration of very small debris. The lifter should be made to move smoothly even if there is some shaking.

Regarding the relationship between the head dimension (A) and the screw plug dimension (SW), the screw plug has been selected so that the diameter (D2) of the tap bottom hole for the screw plug is as close to the dimension A as possible. The spring (SP) has been selected to be of a size that is as close to the dimension A as possible.

For reference, the key point in using a lifter is in the method of selecting the spring. The lifter is a weak spring that can lift up the work to be formed. In addition, very often the amount of deflection of the lifter is also very large. If the spring is selected according to these conditions, very often the spring will be one with a large deflection. If the lifter is used with these conditions, the lifter does not stop immediately when it returns downward, but very frequently carries out a damping movement. If a damping movement is made the supporting of the work to be formed becomes unstable and can cause problems in press forming. The selection of the spring should be made so that its the supporting force is weak and so that the spring is strong enough to eliminate any damping movement.

[Fig. 1] Relationship between a lifter and its hole

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