JPH01299717A - Draw press die for square cylindrical product - Google Patents

Abstract

PURPOSE:To prevent wrinkle formation by arranging plural draw beads laid at each corner part of a blank holder plane nearly in parallel with the straight lines combining the central point of a curved line part at the corner part with the center of curvature of the curved line part or so that the straight lines are held. CONSTITUTION:Draw beads 8 are formed on a blank holder plane 3 of a lower die and a blank holder plane 5 of an upper die, the beads on the press surface 5 of the upper die protrude, the beads on the press surface 3 of the lower die take the shape of a groove and they face each other. The interval between these beads when they come most near and face each other is equal to the plate thickness. At each corner part 13 of the blank holder planes 3, 5, two draw beads 8 are arranged at an equal interval in parallel with and at both sides of the straight line combining the central point X of the curved line part 11 of a drawing profile 9 with the center O of curvature. The draw bead 8 is set from the straight line part 10 at a specified angle. Each point of the raw material W of the corner part 13 flows into a recessed part 2 nearly in parallel with the draw beads of arrow marks C. A member of a straight side part 12 performs a shrinkage flange forming converging into a certain point. In this way, wrinkles, cracks at corner parts are prevented from being formed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a drawing press mold for rectangular tube products used for drawing, for example, a body part of a vehicle.

[Conventional technology]

Generally, in a drawing press die, the outer periphery of the material is pressed and held between the material pressing surface of the lower mold and the material pressing surface of the material pressing member of the upper mold, and in this state, the punch is pressed against the material to form the drawing. is configured to do so. During this drawing process, the punch moves downward toward the inside of the drawing profile (
To be more precise, the material flows in (toward the goo cavity).

In order to control the flow of the material as desired, it is common practice to provide a squeeze bead around the entire circumference or part of the material holding surface.

For example, when trying to obtain a rectangular cylindrical product P having a drawing shape as shown in FIG. A drawing bead 8 may be provided parallel to the straight portion 10 (
Reference nibless molding difficult handbook [Supervised by Seita Yoshida, S
62.3.20 issue) P, 326 Figure 7, 44). This is because the amount of material flowing into the material located at the right side part 12 during drawing is larger than that located at the corner part 13 of the material holding surface 3. This is because it is necessary to provide greater resistance to material inflow.

[Problem to be solved by the invention]

However, in such conventional examples, although the flow rate of the material can be controlled by the drawing bead, the direction in which the material flows cannot be controlled, resulting in molding defects and limitations in the shapes that can be molded. An example is given below to explain this.

As shown in FIG. 9, in the right side part 12 of the material holding surface 3, the material inflow direction is parallel at each point as shown by the arrow a. (hereinafter referred to as parallel flange forming).

In such cases, the material does not flow in one direction, so
Although wrinkles and cracks do not occur, at the corner part 13 of the material holding surface 3 (indicated by hatching for convenience of explanation), each point on the material located at the corner part 13 has a bulge as shown by the arrow. This results in shrinkage flange forming in which the profile 90 flows toward the center of curvature O of the curved portion 11. For this reason, when the blank holding force was small, the materials located at the corner portions 13 of the material pressing surface 3 overlapped and wrinkles S were generated, as shown in FIG.

Moreover, when this wrinkle eventually flows into the side wall of the lower die, it is stretched to fill the gap in the thick bone between the punch and the lower die. However, when the drawing depth is large, the amount of movement of the material located at the corner is as large as that at the right side, and if this gap becomes clogged due to overlapping wrinkles of the material, the material will flow in. If the amount is insufficient, cracks T will occur as shown in FIG.

In addition, when the blank hold force is appropriate, wrinkles do not occur in the material located at the corner portion 13, but since the material is concentrated at the corner portion, an inflow resistance force is generated due to deformation of the material itself located at the corner portion 13. . Therefore, the inflow resistance force of the corner part increases compared to the right side part, so the lower mold side wall part of the corner part or the punch shoulder R of the corner part increases.
This makes it easier for cracks to occur.

Therefore, there are limits in terms of countermeasures against cracking and in terms of the drawing depth that can be formed, and the current drawing beads are not sufficient.

In this way, when the material holding surface consists of a right side part and a corner part, the main cause of wrinkles and cracks in the material located at the corner part is that the material at the corner part shrinks during drawing and flange forming. This is thought to be due to the fact that

Therefore, in order to reduce the wrinkles and cracks that conventionally occur at corners and expand the forming limit, the present invention replaces the shrinkage flange forming that occurs at the corners with parallel flange forming where each point of the material flows approximately parallel to each other. The challenge is to change.

[Means to solve the problem]

In order to solve the above problems, the drawing press die for rectangular tube products of the present invention is provided with a plurality of drawing beads at the corners of the material pressing surface, and each drawing bead is arranged between the center point of the curved part of the corner part and the curved line. It is characterized by being arranged substantially parallel to and sandwiching the straight line connecting the center of curvature of the part.

[Effect]

In this way, during drawing, the material shrinks and a straight line connects the center point of the curved part of the drawing profile and the center of curvature of the curved part at the material holding surface corresponding to the part where flange forming is performed, that is, at the corner of the material holding surface. By arranging the drawing beads approximately parallel to the straight line and sandwiching this straight line, the material at the corner sandwiched between the drawing beads arranged approximately parallel to each other is arranged so that each point of the material flows approximately in parallel. As a result, parts that were conventionally shrink-flange formed are now subjected to neither stretch-flange forming nor shrink-flange forming, so-called parallel flange forming.

For this reason, when the blank hold force is small as in the past, the materials no longer gather and overlap.
Wrinkles can be prevented. Furthermore, as a result, cracks caused by the material getting stuck between the lower mold and the punch when it flows into the lower mold recess can be prevented.

On the other hand, the case where the blank hold force is appropriate will be explained below in terms of the transition of stress generated in the material W during drawing.

FIG. 4 shows the changes in stress in the conventional molding method and the present molding method described in the section on conventional technology. The dotted line indicates the conventional method, and the maximum stress σ occurs in the material located at the corner of the material pressing surface due to shrinkage flange forming. When the maximum value σ of this stress reaches the tensile strength σ0 of the material, cracking occurs. On the other hand, the present molding method is as shown by the solid line. In general, the drawing profile length of the right side part is longer than that of the corner part, that is, the shrinkage flange ratio is smaller, so the stress B° applied to the material located at the right side part where shrinkage flange formation occurs is a value smaller than the stress C' applied to the material located at the corner portion. As a result, the tensile strength of the material σ. It can be seen that this molding method is less prone to cracking than the conventional molding method because the difference between the maximum value σ2 of the stress generated in the material located at the right side increases. Further, contrary to the conventional method, the material located at the corner part flows in parallel and the stress C° becomes constant, making it difficult for wrinkles and cracks to occur.

As can be seen from the stress transition graph in FIG. 4, it can be seen that this molding method can reduce the maximum value of stress compared to the conventional method, making cracks less likely to occur.

〔Example〕

Hereinafter, one embodiment of the present invention will be described with reference to FIGS. 1 to 3.

FIG. 1 shows a drawing press mold 1 according to an embodiment of the present invention. A surface 3 is formed. The material holding member 4 is provided above the lower mold 1 so as to be able to rise and fall freely by a drive means (not shown), and its lower surface serves as an upper mold material pressing surface 5 and cooperates with the lower mold material pressing surface 3 to clamp the outer periphery of the material W. do. The punch 6 is provided above the lower mold 14 so as to be movable up and down by a drive means (not shown), and can pass through an open lower portion formed in the center of the material holding member 4 and sink into the recess 2 of the lower mold l.

On the lower mold material pressing surface 3 and the upper mold material pressing surface 5, a throttle and a dome 8 are formed to appropriately control the flow of material into the recess 2 during drawing forming. Regarding the shape of the drawing bead 8, the drawing bead on the upper mold material pressing surface 5 has a raised shape, and the drawing bead on the lower mold material pressing surface 3 has a groove shape. When they come close, they face each other. The distance between the raised drawing bead and the grooved drawing bead when they were closest to each other was exactly the same as the thickness of the plate. In this embodiment, the aperture bead 8 is provided as shown in FIG. That is, the material pressing surface 3.5
Two aperture beads 8 are arranged at each corner portion 13 of the aperture profile 9 in parallel with a straight line connecting the center point X of the curved portion 11 and the center of curvature 0, and at equal intervals across the straight line. .

The shape of the drawing profile 9 is bilaterally symmetrical, and in order to equalize the material inflow conditions at the four corners 13 of the material holding surface 3.5, the drawing bead 8 is formed at an angle of 135'' from the straight part 10 of the drawing profile 9. I set it accordingly.

By adopting the above configuration, the material holding surface 3.5
The inflow of the material at the corner portion 13 can be made into parallel inflow by the following action.

The material W is placed on the lower mold l, then the material pressing member 4 descends, and after pressing and holding the material W between the lower mold material pressing surface 3 and the upper mold material pressing surface 5, the punch 6 descends. Then, drawing and forming will be performed.

During this drawing process, the workpiece W held between the workpiece holding surfaces 3.5 is drawn into the recess 2 by the processing force of the punch 6, but the workpiece W held by the workpiece holding surfaces 3.5 is drawn into the recess 2. Since the bead 8 is arranged so as to be parallel to the straight line connecting the center point X of the curved portion 11 of the aperture profile 9 and the center of curvature O, the part sandwiched between these two parallel aperture beads 8 Each point of the material flows approximately parallel to the drawing bead 8. This is because the material is difficult to flow in a direction perpendicular to the direction in which the drawing beads 8 are arranged, and also because the material is pulled substantially parallel to the direction in which the drawing beads 8 are arranged. As a result, as shown in the third figure, each point on the material W1 corresponding to the corner portion 13 of the material holding surface 3 is sandwiched between two parallel drawing beads 8. As shown by arrow C, it flows into the recess 2 approximately parallel to the aperture bead 8 . Further, the material corresponding to the right side portion 12 of the material holding surface 3.5 is subjected to shrinkage flange forming in which each point of the material flows convergently in a certain negative direction. However, in this case,
Since the shrinkage flange ratio is small, it does not cause wrinkles or cracks.

In other words, in the conventional drawing bead arrangement shown in FIG.
As shown in the figure, shrinkage flange forming was performed at the corner portion 13 and parallel flange forming was performed at the right side portion 12.
By adopting the drawing bead arrangement of the present invention, shrinkage flange formation is performed at the right side portion 12 and parallel flange formation is performed at the corner portion 13, contrary to the conventional method.

In this example, drawing was performed under the following forming conditions, but the drawn product had wrinkles and
No cracking was observed.

Blank hold pressure crab 120 ton Drawing depth: 1
03m Steel plate for nibless forming Thickness 1,511 Radius of curvature of curved part of drawing profile: 80fl Length of straight part of drawing profile 1-10101mlt →720 TsuruIn addition, in this example, a drawing bead in the direction parallel to the drawing profile is not provided. However, as shown in Figure 5,
It may be provided as appropriate to suppress material flow as in the past.

Further, when applied to a forming method in which a locally movable punch restrains the material instead of a drawing bead during forming, the yield of the -layer material improves. This is because wrinkles and cracks are less likely to occur at the corner portions, and material inflow can be controlled at the local punch side wall portions.

Furthermore, in this example, the raised parts constituting the two parallel drawing beads were both provided on the upper mold, and the groove-like parts opposing these were both provided on the lower mold. As shown, the drawing bead may be formed by providing one protuberance on the upper die and the other on the lower die at different levels.

〔Effect of the invention〕

In this way, a plurality of drawing beads are provided at the corners of the material pressing surface, and these drawing beads are arranged parallel to and sandwiching the straight line connecting the center point of the drawing profile curved part and the center of curvature. As a result, each point of the corner material flows into the lower mold groove parallel to the drawing bead during the drawing process. For this reason, the corner material does not gather at one point and overlap as in the past, and wrinkles can be prevented.

Further, as a result, when the material flows into the lower mold recess, it is not caught by the mold, no large tensile force is applied to the material, and cracking can also be prevented.

[Brief explanation of the drawing]

Fig. 1 is a perspective view of a drawing press mold showing an embodiment of the present invention; Fig. 2 is a partially enlarged view of Fig. 1; Fig. 3 shows the direction of inflow of the material during forming in the present invention. FIG. 4 is a stress-stroke diagram in the conventional method and the present invention. FIG. 5 is a perspective view of another embodiment of the present invention, showing only the corner portion. FIG. 6 is a diagram of the present invention. FIG. 7 is a perspective view showing a drawn product; FIG. 8 is a perspective view of a drawing press mold showing a conventional drawing bead arrangement; FIG. 9 The figure is a schematic diagram showing the inflow direction of the material during forming in the conventional example, and Fig. 10 is a perspective view of a drawn product showing the occurrence of wrinkles and cracks in the conventional example. -Drawing press die 12---Right side part 14---Lower mold 2---Concave part 3.5---One material pressing surface 4------ Material holding member 6 - Punch 7 - = - Opening 8 - Drawing bead 9 - Drawing profile lO - Straight section 11 - - - - Curved portion 13 - Corner part 0 - 1111 Center of curvature X - 1 - Center point Applicant Toyota Motor Corporation Figure 3 Figure 1 A: Tensile strength of material B : Jutota Rikooshi 1 and the response car that deals with the unsealed JiL Kōlko C: Karasu force generated in the material of the corner part B°: Hata Bogata 5 friends The stress and force C' that occurs in the material of the right side part at 3L': The stress and force that occurs in the material of the right side part (Figure 7, Figure 8)

Claims (1)

[Claims] In the drawing press mold for rectangular tube products having a drawing profile consisting of a curved part and a straight part, the drawing press mold for a rectangular tube product has a drawing profile consisting of a curved part and a straight part, in which the material is held between the material pressing surface of the lower die and the material pressing surface of the material pressing member, and then drawn by a punch. A plurality of drawing beads are provided at the corners of the material pressing surface, and the drawing beads are
A drawing press mold for a rectangular tube product, characterized in that it is arranged substantially parallel to and sandwiching the straight line connecting the center point of the curved part of the corner part and the center of curvature of the curved part.