JP2021159918A - Press molding method - Google Patents

Abstract

To prevent a molding failure such as a crack or wrinkle on a molding.SOLUTION: A press molding method includes a preliminary molding step of molding part of a blank 17 before a punch 11 comes into contact with the blank 17.SELECTED DRAWING: Figure 8

Description

The present invention relates to a press molding method.

For example, a metal panel part in an automobile body is formed into a predetermined shape by subjecting a blank material to press molding such as drawing. The press forming equipment (die) used for drawing is a die on the movable side, a punch on the fixed side, and a blank holder (upper blank holder and lower blank holder) for holding the end of the blank material. (See, for example, Patent Document 1).

In order to form a blank material by the above press forming apparatus, first, the die located above the blank material and the upper blank holder are lowered in a state where the blank material is in contact with the punch and the lower blank holder. As a result, the entire circumference of the end portion of the blank material is sandwiched between the upper blank holder and the lower blank holder.

When the die and each blank holder are further lowered, the die and the punch are fitted. As the die, punch, and fitting progress, the blank material is stretched and formed into a predetermined shape.

Japanese Unexamined Patent Publication No. 2012-71338

In the conventional press molding method, local cracks and wrinkles occur when a molded product having a complicated cross section and a large drawing depth is manufactured, such as a backdoor inner panel. It becomes a problem.

Therefore, it is a technical subject of the present invention to prevent the occurrence of molding defects such as cracks and wrinkles in the molded product.

The present invention is for solving the above-mentioned problems, and in a press molding method for producing a molded product by press-molding a blank material held by a blank holder with a die and a punch, the punch is the blank material. It is characterized by including a pre-molding step of molding a part of the blank material before contacting the blank material.

According to such a configuration, a part of the blank material formed by the preforming step tends to flow between the die and the punch during the subsequent forming of the blank material by the die and the punch. This makes it possible to prevent the occurrence of molding defects such as cracks and wrinkles in the molded product.

In the present invention, the die may have a premolded surface for molding the part of the blank material before the punch comes into contact with the blank material in the preforming step. This makes it possible to manufacture a molded product without adding molding equipment for executing the pre-molding process.

According to the present invention, it is possible to prevent the occurrence of molding defects such as cracks and wrinkles in the molded product.

It is a top view of a molded product. It is sectional drawing which concerns on the line of sight of the arrow II-II of FIG. It is sectional drawing of the press molding apparatus. It is sectional drawing of the press molding apparatus. It is sectional drawing of the press molding apparatus in one step of a press molding method. It is sectional drawing of the press molding apparatus in the preforming process of a press molding method. It is sectional drawing of the press molding apparatus in the preforming process of a press molding method. It is sectional drawing of the press molding apparatus in the preforming process of a press molding method. It is sectional drawing of the press molding apparatus in one step of a press molding method. It is sectional drawing of the press molding apparatus in one step of a press molding method.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. 1 to 10 show an embodiment of the press molding method according to the present invention.

FIG. 1 illustrates an intermediate molded product of a backdoor inner panel used for an automobile body as a molded product molded by this method. The molded product 1 is formed by drawing a flat plate-shaped blank material. The molded product 1 has a product unit 2 and parts to be removed (surplus thickness) 3a and 3b separated from the product unit 2.

The product part 2 is a part that becomes a backdoor inner panel by cutting off the parts 3a and 3b to be removed. The planned removal portions 3a and 3b include a first scheduled removal portion 3a and a second scheduled removal portion 3b. The first planned removal portion 3a is formed on the outer peripheral portion of the molded product 1. The second planned removal portion 3b is formed inside the molded product 1. The second planned removal portion 3b is a portion to be removed from the molded product 1 in order to form a window hole in which the window glass is mounted in the back door.

As shown in FIG. 2, the product part 2 has the first molded part 4 and the first molded part 4 in this order from the outside (first scheduled removal part 3a side) to the inside (second removal planned part 3b side) of the molded product 1. It has a second molded portion 5 and a third molded portion 6. In addition, the product part 2 includes a seal part 7 formed between the first molded part 4 and the second molded part 5 and which can be waterproofed, and the second molded part 5 and the third molded part. It has a recess 8 (groove) formed between the portion 6 and the portion 6.

As shown in FIG. 2, the first planned removal portion 3a includes a molded portion 9 that is molded (preformed) by a press molding apparatus described later.

3 and 4 show a press molding apparatus (die) used in this method. The press forming apparatus includes a die 10 on the movable side, a punch 11 on the fixed side, and blank holders 12 and 13 for holding the blank material.

The die 10 is arranged above the punch 11 so as to be able to move up and down. The die 10 has a concave shape as a whole and a main molding surface 14 for molding the product portion 2 of the molded product 1, and a convex shape and a molding portion 9 of the first planned removal portion 3a. It has a premolded surface 15.

As shown in FIG. 4, the main molding surface 14 of the die 10 includes a first molding surface 14a for molding the first molding portion 4 of the product part 2 in the molded product 1 and a second molding of the product part 2. It has a second molding surface 14b for molding the portion 5, a third molding surface 14c for molding the third molding portion 6 of the product portion 2, and a concave surface 14d corresponding to the recess 8 of the product portion 2. ..

The preformed surface 15 of the die 10 is located on the outside of the main forming surface 14 (on the outer blank holder 12 side). The preformed surface 15 is formed in a curved surface shape that is continuously connected to the main molded surface 14. The preformed surface 15 is a surface that comes into contact with the blank material before the punch 11 comes into contact with the blank material.

The punch 11 has a molding surface 16 which is formed to be convex as a whole. The forming surface 16 is formed between the first forming surface 16a that engages between the first forming surface 14a of the die 10 and the preforming surface 15 and the first forming surface 14a and the second forming surface 14b of the die 10. A second molded surface 16b to be engaged and a third molded surface 16c for forming a recess 8 of the product portion 2 in the molded product 1 are provided.

The blank holders 12 and 13 include an outer blank holder 12 and an inner blank holder 13. The outer blank holder 12 includes an upper blank holder 12a that contacts one surface (upper surface) of the blank material and a lower blank holder 12b that contacts the other surface (lower surface) of the blank material 17. The inner blank holder 13 is composed of only a lower blank holder that contacts the other surface (lower surface) of the blank material.

Hereinafter, a method (press molding method) for manufacturing a molded product 1 from a blank material by using the press molding apparatus having the above configuration will be described.

In this method, first, as shown in FIG. 5, the outer peripheral portion (end portion) of the blank material 17 is held by the outer blank holder 12. The outer peripheral portion of the blank material 17 is sandwiched between the upper blank holder 12a and the lower blank holder 12b of the outer blank holder 12. In this state, the die 10, the punch 11, and the inner blank holder 13 are not in contact with the blank material 17.

Next, the preforming surface 15 of the die 10 executes a preforming step on the blank material 17. The preforming step is performed before the punch 11 comes into contact with the blank material 17.

As shown in FIG. 6, in the preforming step, the die 10 is lowered and its preforming surface 15 comes into contact with a part of the upper surface of the blank material 17. Specifically, the preformed surface 15 of the die 10 presses a part of the blank material 17 at a position inside the outer blank holder 12 and outside the forming surface 16 of the punch 11. After that, as shown in FIG. 7, the inner blank holder 13 rises and comes into contact with the lower surface of the blank material 17.

As a result, as shown in FIG. 8, the blank material 17 is formed with a protrusion 18 projecting downward (toward the punch 11 side). In this state, the molding surface 16 of the punch 11 is not in contact with the blank material 17. As shown in FIG. 9, the preforming step is completed when the protruding portion 18 is formed to have a predetermined protruding dimension.

Next, the main molding step on the blank material 17 is executed by the main molding surface 14 of the die 10 and the molding surface 16 of the punch 11.

In the main molding step, the die 10 is further lowered after the pre-molding step. Each of the blank holders 12 and 13 lowers the blank material 17 as the die 10 lowers. In this molding step, as shown in FIG. 9, the first molding surface 14a of the die 10 first contacts the blank material 17. In this state, the molding surface 16 of the punch 11 is not in contact with the blank material 17.

As shown in FIG. 10, when the die 10 and the blank holders 12 and 13 are further lowered, the third forming surface 16c of the punch 11 comes into contact with the blank material 17. The blank material 17 is stretched by being pressed against the third forming surface 16c of the punch 11. In this case, the protrusion 18 formed by the preformed surface 15 of the punch 11 flows inward (the third formed surface 16c side of the punch 11) while being plastically deformed.

Further, the outer peripheral portion of the blank material 17 held by the outer blank holder 12 is between the die 10 and the punch 11 according to the progress of molding by the main molding surface 14 of the die 10 and the molding surface 16 of the punch 11. Flow toward.

When the die 10 and the blank holders 12 and 13 are further lowered, the third forming surface 14c of the die 10 comes into contact with the blank material 17 (see FIG. 10). After that, the second forming surface 14b of the die 10, the first forming surface 16a of the punch 11, and the second forming surface 16b come into contact with the blank material 17. When the die 10 reaches the bottom dead center, the main molding process is completed.

As a result, the molded product 1 including the product part 2 and the parts to be removed 3a and 3b is formed. After the completion of this molding step, the protrusion 18 becomes the molding portion 9 of the first planned removal portion 3a and remains in the molded product 1. The parts 3a and 3b to be removed from the molded product 1 are cut from the molded product 1 by a subsequent trimming step.

According to the press molding method according to the present embodiment described above, by forming the protrusion 18 on the blank material 17 in the preforming step, a part of the blank material 17 including the protrusion 18 is formed in the main molding step. It becomes easy to flow inward (between the main forming surface 14 of the die 10 and the forming surface 16 of the punch 11).

As a result, in the main molding step, molding defects such as cracks and wrinkles are less likely to occur in the blank material 17 formed by the main molding surface 14 of the die 10 and the molding surface 16 of the punch 11. Moreover, since the amount of the blank material 17 that flows between the main molding surface 14 of the die 10 and the molding surface 16 of the punch 11 can be reduced as much as possible, the yield of the molded product 1 can be improved. ..

Further, the protrusion 18 (molded portion 9 of the first planned removal portion 3a) formed on a part of the blank material 17 by the preforming step protrudes in the direction opposite to the direction of the recess in the recess 8 of the molded product 1. ing. Therefore, it is possible to secure a large drawing depth dimension D (see FIG. 2) of the molded product 1 according to the amount of protrusion of the protruding portion 18.

Further, by executing the preforming step on the preforming surface 15 provided on the die 10, it is not necessary to separately add molding equipment for performing the preforming step. This makes it possible to manufacture a high-quality molded product 1 while suppressing the equipment cost.

The present invention is not limited to the configuration of the above embodiment, nor is it limited to the above-mentioned effects. The present invention can be modified in various ways without departing from the gist of the present invention.

In the above embodiment, the backdoor inner panel is illustrated as the molded product 1, but the present invention is not limited to this configuration and can be applied to the production of various molded products.

1 Molded product 10 Die 11 Punch 12 Outer blank holder 15 Preformed surface 17 Blank material

Claims (2)

In a press molding method for producing a molded product by press molding a blank material held by a blank holder with a die and a punch.
A press molding method comprising a preforming step of molding a part of the blank material before the punch comes into contact with the blank material. The press molding method according to claim 1, wherein the die has a premolding surface for molding the part of the blank material before the punch comes into contact with the blank material in the preforming step.

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