JPH0761507B2 - Forming method using a drawing die - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention (Industrial field of application) The present invention is based on a drawing die for drawing a metal plate and forming a punched portion on the metal plate at the same time as a positioning reference in a subsequent step. The present invention relates to improvement of a molding method.

(Prior Art) For example, a recess is generally formed on the bottom of an inner box of a microwave oven for the purpose of efficiently irradiating microwaves on food, and a table for placing food on the recess is provided above the recess. To be done. The inner box of this microwave oven is formed by bending a metal plate material.Before the metal plate material for the inner box is bent, the recess is drawn into a portion corresponding to the bottom of the inner box. There is.

The drawn metal plate material is then subjected to edge cutting processing for cutting the peripheral edge. This edging needs to be performed by accurately positioning the metal plate material.Therefore, a positioning notch is formed in the metal plate material when the recess is drawn, and this cutout is used as a reference when edging. The metal plate is positioned.

However, depending on the drawing process, the material flows toward the drawn part, so that the entire metal plate material is pulled toward the drawn part. Then, due to the influence of this pulling force, the portion where the positioning notch is punched is pulled toward the drawing side and is displaced from the regular position. The amount of this deviation varies depending on the size and depth of the recess, but it is usually about 0.2 to 0.3 mm. If the position of the positioning notch shifts in this way, the position of the edge cut shifts,
The positional relationship between the concave portion and the table is incorrect.

(Problems to be Solved by the Invention) As described above, the conventional drawing method has a problem that the position of the positioning punching portion is deviated and the subsequent processing cannot be performed at the regular position.

The present invention has been made in view of the above circumstances, and an object thereof is to form a punching portion for positioning at the time of drawing, in which the position of the punching portion does not deviate from the regular position. To provide a molding method according to the present invention.

[Structure of the Invention] (Means for Solving the Problems) The forming method using the drawing die of the present invention is different from the drawing punch and die for drawing a metal plate material and the drawn part of the metal plate material. First, by means of a drawing die having a step bending punch and a die forming a step bending portion that is recessed with a step in the part, and a punch punch and a die forming a positioning punching portion in the step bending portion, first the metal plate material is obtained. It is characterized in that a stepped bent portion is formed in the step, and thereafter, the metal plate material is drawn and a punched portion is formed in the step bent portion.

(Operation) According to the forming method of the present invention, the stepped portion is first formed in the metal plate material, and then the drawing processing is performed. During this drawing, each part of the metal plate material tends to be pulled toward the drawn part, but the tensile force acting on the step bending part is received by the punch and die for the step bending part.
Therefore, the step-bent portion and the punched-out portion formed in the step-bent portion are not displaced.

(Embodiment) An embodiment in which the present invention is applied to the case of forming an inner box of a microwave oven will be described below with reference to FIGS. 1 to 6.

First, in FIG. 4 showing a drawing die, 1 is a punch holder mounted on a bed 2 of a press via a spacer 3, and a drawing punch 4 is fixed to the center of the upper surface of the punch holder. A blank holder 6 having a hole 5 in which the aperture punch 4 is inserted and arranged is supported by the punch holder 1 via a guide lever 7 so as to be vertically movable. The guide bar 7 of the blank holder 6 is supported by a cushion base 8 arranged below the punch holder 1, and the cushion base 8 is elastically supported by a die cushion 9 composed of an air tank of the press. . The blank holder 6 elastically supported by the die cushion 9 in this way has a substantially rectangular shape, and is bent at two corners of one side along the longitudinal direction thereof as shown in FIG. Forming die 10 is formed. The step bending die 10 is formed in a step surface shape having an arcuate vertical wall surface 10a cut substantially vertically from the upper surface of the blank holder 6.
Then, the bottom portion of the step bending die 10 is formed by notching a corner portion of the bottom portion in a substantially L shape and forming the cutting edge 11a at the notched upper edge thereof. Is configured as.

On the other hand, 12 is a die holder attached to a ram 13 of the press, and a drawing die 14 is fixed to the lower surface of the die holder.
Further, the die holder 12 is provided with a step bending punch 15 at a position corresponding to the step bending die 10 so as to be vertically movable via a guide pin 16, and at a position corresponding to the punching die 11. A punch 17 for punching is fixed to this. Reference numeral 18 is a compression spring that biases the step bending punch 15 downward.

Next, the procedure for drawing the inner box forming metal plate material 19 of the microwave oven by drawing with the drawing die configured as described above will be described. The metal plate material 19 is placed on the blank holder 6 as shown in FIG. 4, and the ram 13 of the press is lowered in this state. Then, the step-bending punch 15 first comes into contact with the two corners of the metal plate material 19, and the corners are stepped as shown in FIG.
Forming 20. Next, punching punch 17 is a punching die
In cooperation with 11, the tip corner portion of the bottom of the step bending portion 20 is punched as shown in FIG. 3 to form a rectangular punching portion 21 for positioning as shown in FIG.

The step bending portion 20 is formed on the metal plate material 19 as described above,
When the punched portion 21 is formed on the stepped bent portion 20, the drawing die 14 then strongly presses the metal plate material 19 against the blank holder 6 while resisting the elastic force of the die cushion 9. Move it down. Then, the drawing punch 4 comes to project relatively upward from the hole 5 of the blank holder 6, and the cooperation of the drawing punch 4 and the drawing die 14 causes the metal plate material 19 to be shown in FIG. As shown, the substantially rectangular recess 22 is formed by drawing.

During the drawing of the recess 22, the metal plate material 19 is
It behaves like being pulled toward the formation site of. However, since the step bending portion 20 is already formed on the metal plate material 19 and the step bending portion 20 is strongly pressed between the step bending die 10 and the punch 15, the tension acting on the step bending portion 20 is increased. The force is received by the vertical wall surface 10a of the step bending die 10. Therefore, the material of the step-bending portion 20 does not behave as if it flows toward the draw-formed portion, and therefore the defect that the punching portion 21 formed in the step-bending portion 20 is displaced does not occur.

Now, after the recess 22 is formed by drawing in the metal plate material 19 as described above, the ram 13 rises. By the rise of this ram 13,
The step bending punch 15 is moved downward by the spring force of the compression spring 18 to remove the metal plate material 19 from the drawing die 14, and the blank holder 6 is moved upward by the elastic force of the die cushion 9 to move the metal plate material. The 19 is removed from the aperture punch 4 and thus everything is returned to its original state.

As described above, according to this embodiment, since the material flows toward the drawn portion during drawing, the metal plate material 19
Even if there is a situation in which the whole is pulled toward the narrowed portion, the positioning punching portion 21 is excluded from the flow of such a material by the step bending portion 20 and is kept from sliding. Therefore, when cutting the peripheral edge of the metal plate material 19 in a later step, the metal plate material 19 can be set at a regular position with reference to the punched portion 21, and the edge can be cut accurately. The metal plate material 19 is finally bent into a substantially U-shape as shown in FIG. 6 to form a bottom plate and left and right side plates of the inner box of the microwave oven.

Next, FIG. 7 shows another embodiment of the present invention. The difference from the above-mentioned one embodiment is that the stepped bent portion 23 is formed to be elongated at both side edges along the longitudinal direction of the metal plate material 19. is there. In this way, the stepped bent portion 23 functions as a so-called grip beat, and when the recess 22 is formed by drawing, it is possible to prevent the occurrence of “wrinkles” that are likely to occur at the corners of the recess 22.

In each of the above embodiments, the punching portion for positioning is a notch, but it may be a hole. Further, the present invention is not limited to the case of forming the concave portion at the bottom of the inner box of the microwave oven, but can be widely applied to the case of forming a metal plate material and can be widely applied.

[Effects of the Invention] As described above, according to the forming method of the drawing die of the present invention, the step bending portion that is recessed with a step is formed in the metal plate material,
After that, the metal plate material is formed by drawing, and the punching portion for positioning is formed in the step bending portion. Therefore, even if the material flows toward the drawing portion during drawing, Since the bent portion is excluded from the flow of the material by the step bending punch and the die, the step bent portion is not displaced, and therefore the positioning punching portion formed in the step bent portion is also removed. Since there is no displacement, the metal plate material can be accurately positioned with reference to the punched portion during post-processing.

[Brief description of drawings]

1 to 6 show an embodiment of the present invention. FIG. 1 is a vertical sectional view of a drawing die shown in a state during drawing processing.
The figure is a perspective view of the main part, Fig. 3 is an enlarged vertical cross-sectional view showing the processed state of the main part, Fig. 4 is a vertical cross-sectional view of the drawing die shown in the state before the processing, and Fig. 5 is the metal after the drawing process. FIG. 6 is a perspective view of the plate material, FIG. 6 is a perspective view of the metal plate material after bending, and FIG. 7 is a view corresponding to FIG. 5 showing another embodiment of the present invention. In the figure, 4 is a punch for punching, 6 is a blank holder, 8 is a cushion base, 9 is a die cushion, 10 is a die for step bending, 11 is a die for punching, 14 is a die for drawing, and 15 is a punch for step bending. 17 is a punch for punching, 19 is a metal plate material, 20 is a stepped portion, 21 is a punched portion, 22 is a concave portion, and 23 is a stepped portion.

Claims (1)

[Claims] 1. A punching die and a die for drawing a metal plate material, and a step bending punch and a die for forming a step bending portion which is recessed with a step in a portion different from the drawn portion of the metal plate material, With a drawing die having a punching punch and a die for forming a punching portion for positioning in the stepped bent portion, first, a stepped bent portion is formed in the metal plate material, and thereafter, the metal plate material is drawn and a step is formed. A forming method using a drawing die, characterized in that a punching portion for positioning is formed in the bent portion.