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#035 Basics of Die Structure (17) Structure of Drawing Dies: First Drawing Dies for Drawing and Dropping

Category : Drawing and Forming Work
April 2, 2010

The most important parts of a die for drawing are the punch, the die, and the wrinkle suppressor. When drawing a cylindrical shape without a flange from a blank, a die of the drawing and dropping structure such as the one shown in Fig. 1 is used. The material to be formed is placed on the positioning plate, and after that material is drawn by the punch, the product is made to pass through the die and fall down. Even the die structure is simple and easy to prepare, and the die structure can be said to be one offering efficient press operation. The drawback is that the bottom part gets bent and it is difficult to make it flat.


The wrinkle suppressor in cylindrical drawing is used for the purpose of preventing the generation of wrinkles because of the material getting buckled due to the compression in the circumferential direction during drawing of the blank. The generation of wrinkles can be known roughly from the value of the material thickness divided into the diameter of the blank (expressed as a % value, and called the relative plate thickness). When the relative plate thickness is 3 or more with the drawing ratio (m) being about 0.6, it is possible to draw even without a wrinkle suppressor. As is shown in Fig. 2, the structure of the die can also be much simpler.


The purpose of the wrinkle suppressor is to suppress the buckling of the material. It is sufficient to prepare a gap so that the material to be drawn can move, and also wrinkles are not formed, and hence there is also a die structure using a fixed stripper as shown in Fig. 3.


Although this structure is easy to prepare compared to the structure of Fig. 1 using a spring, it is difficult to carry out manual press operation. This is used for simple type die for small volume production when used for manual operations. For mass production, the suitable structure is one in which automatic forming is done using a pusher feeder (an apparatus that carries out automatic forming by inserting into the die one sheet at a time from a pile of blanks that are pushed out by a plate shaped part carrying out reciprocating movement). Since quite a large force acts on the wrinkle suppressor, it will get warped if it is too thin. It is necessary to design it with a slightly larger thickness.

Although movable type wrinkle suppressors are very common, depending on the conditions, it may not even be necessary. The structure of a die should not be determined shortsightedly and in haste, but should be determined checking even the forming conditions and the method of working, etc.

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