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#036 Basics of Die Structure (18) Structure of Drawing Dies: First Drawing Dies for Downward Drawing

Category : Drawing and Forming Work
April 9, 2010

This is a structure in which a knock out is incorporated in a die of the drawing and dropping type structure with movable wrinkle suppressor. This structure is shown in Fig. 1

Fig. 1

This structure can be used for both drawing of cylindrical shapes with flanges and drawing of cylindrical shapes without flanges from blanks. In addition, since the forming is done while gripping the material between the punch and the knock out, the flatness of the bottom of the drawing object is quite good. The knock out has the two functions of pressing down the material and of ejecting the product.

The drawback of this structure is that it is not suitable for deep drawing. The reason for this is that there is some restriction on the length of the spring that can be incorporated. Considering the top die, the punch becomes longer in proportional to the depth of drawing. At the same time, it is necessary to make even the spring for the wrinkle suppressor longer. If the length of the spring is determined from the amount of deflection of the spring, a longer space than the punch may be required, and hence the top die becomes large thereby it becomes difficult or impossible to realize the structure because of the balance relationship with the bottom die or because of the die height,

The same can be said of the knock out spring of the bottom die.

Because of the spring space, this is a structure that is used frequently for relatively shallow drawing operations.

When this die is seen from the point of view of press operations, this structure cannot be said to have ease of operation. In specific terms, the material is inserted in the positioning plate in the lower die. The drawing is done when the upper die comes down. Although the formed product is ejected from the die in the condition in which it is gripped between the knock out and the wrinkle suppressor of the top die, since the product is being pressed down by the wrinkle suppressor, the product will remain on the die. This product is removed by the operator and the next material is inserted inside the die. Since the operator will have to carry out the two operations of inserting the material into the die and of taking out the product from inside the die, the efficiency of operation goes down compared to merely inserting the material inside the die which is then drawn and dropped.

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