JPH03297521A - Drawing die - Google Patents

Abstract

PURPOSE:To generate unbending and to inhibit wrinkles from generating by normally and preliminarily drawing a blank through the approach of the 1st to the 2nd die and pulling a preliminary drawn part formed by preliminary drawing into the side of a normal drawing die with the advance of the normal drawing. CONSTITUTION:There is provided a 1st die having a normal drawing punch 42 to draw a flat blank 26 and a preliminary drawing die 34 equipped integrally on its outside. There is provided a 2nd die having a normal drawing die 30 wherein approach to the 1st die or separation from it can be performed and the blank is drawn normally in cooperation with this normal drawing punch 42 and a preliminary drawing punch 28 equipped integrally on its outside. The blank is drawn normally and preliminarily by the approach of the 1st to the 2nd die and the preliminary drawn part formed by the preliminary drawing is pulled into the side of the normal drawing die 30 with the advance of the normal drawing. In this time, unbending is generated in the preliminary drawn part, pulling force is given to the blank and wrinkles are inhibited from generating. In this manner, a blank holder member is not required and the construction of the die can be simplified.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a drawing die for forming flanged molded products, and in particular to wrinkle suppression.

BACKGROUND OF THE INVENTION When a flat material is drawn to form a flanged molded product, wrinkles may occur. When drawing is applied, the outer periphery of the material generally contracts, but some parts of the material do not shrink completely, resulting in wrinkles. Therefore, the material is held down by a wrinkle suppressing member and a tensile force is applied to the material to prevent the occurrence of wrinkles. but,
The wrinkle suppressing member must be movable relative to the punch or die that performs the squeezing, and must be biased in one direction by an elastic member or hydraulic cylinder, which can avoid making the mold structure complicated and expensive. I can't get it.

Therefore, an inexpensive drawing die is proposed in JP-A-1-72919. This drawing die has an upper die and a lower die, the upper die is provided with a punch, a presser pin is provided on the outside of the punch, and the lower die is provided with a die that works with the punch to draw the material. . During drawing, as the second mold descends, the part of the material placed on the lower mold outside the opening edge of the die is bent downward by the presser pin, and the second mold is further lowered to remove the punch and die. When the material is drawn, the part of the material bent by the holding pin is drawn into the die. At this time, the material bends and unbends before and after the edge of the die opening, which provides resistance to the drawing of the material into the die and applies tensile force, causing the material to be drawn into the die. The occurrence of wrinkles is avoided.

Problems to be Solved by the Invention However, in this drawing die, the presser pins only partially hold down the material, and the resistance to drawing the material is uneven, and when relatively deep drawing is performed, the resistance increases. There was a problem that the anti-wrinkle effect was insufficient.

An object of the present invention is to provide a simple and inexpensive drawing die that can effectively avoid the occurrence of wrinkles during drawing.

Means for Solving the Problems In order to solve the above problems, the drawing die of the present invention has the following features:
) A first type having a wood drawing punch for drawing a flat material, and a preliminary drawing die integrally provided on the outside of the main pattern punch; (b) the first type; A die for making a real pattern that can be approached and moved away from the material and working together with a punch for making a real pattern to apply a real pattern to the material, and a die for preliminary drawing that is integrally provided on the outside of the die for making a real pattern. a second die having a preliminary drawing punch for jointly performing preliminary drawing on the outer periphery of the material and forming a preliminary drawing part extending in the approach/separation direction; The shape and dimensions of the pre-drawing punch and the die form a pre-drawing part at the latest by the middle stage of the main pattern, and the length of the preliminary drawing part becomes shorter as the main pattern progresses. It is characterized by being set according to the shape and dimensions.

Note that the term "outer periphery of the material" as used herein does not necessarily mean the entire outer periphery, but also includes a part of the outer periphery.

Also, ``the intermediate stage of Honmonri'' means an intermediate stage from the start of Honmonri to its completion, and does not necessarily mean the middle stage. Rather, it is often desirable to start the process relatively close to the beginning.

Furthermore, the shape and dimensions of the punch and die for the main pattern and the punch and die for the preliminary drawing may be such that the preliminary drawing part remains when the main pattern is completed, or the shape and dimensions are such that the preliminary drawing part remains at the time of completion of the main pattern, or the shape and size are such that the preliminary drawing part remains when the main pattern is completed. Good effect as a shape and size that eliminates the preliminary drawing part in the front In the drawing die constructed as described above, the main pattern and preliminary drawing are applied to the material by the proximity of the first die and the second die, and the preliminary drawing part is removed. The preliminary drawing portion formed by the drawing is drawn toward the main pattern die side as the main pattern advances. At this time, the pre-squeezed portion is bent back and tensile force is applied to the material, thereby suppressing the generation of wrinkles.

Effects of the Invention As described above, according to the drawing die of the present invention, a preliminary drawing section is provided to prevent wrinkles from being caused by bending and unbending the section, but the punch and die for preliminary drawing each have a main pattern. The mold is integrated with the die and punch, requiring fewer parts compared to the conventional case where a separate wrinkle suppressing member is provided, simplifying the structure of the mold and reducing costs. be able to.

Further, the pre-squeezed portion can be formed in the entire part of the material where tensile force needs to be applied, so that the tensile force can be evenly applied to the part where wrinkles occur, and there is no shortage of wrinkle suppressing force.

Embodiments Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

FIG. 6 shows a flanged molded product 0 formed using a drawing die according to an embodiment of the present invention. This molded product 10 has a shape in which a flange 14 extends outward from the opening periphery of a container-shaped main body 12. The bottom surface of the main body 12 has a shape in which four corner portions of a rectangle are each rounded into an arc shape, and the side surface thereof includes a partial cylindrical portion. Hereinafter, the portion of the main body 12 that does not include the partial cylindrical portion will be referred to as the straight side portion 16, and the portions on both sides of the right side portion 16 that include two partial cylindrical portions will be referred to as the partial cylindrical portion 18.

A drawing die for forming this molded product 10 will be explained.

As shown in FIG. 1, the drawing die includes an upper die 2 as a second die.
2 and a lower mold 24 as a first mold, the molded product 10 is formed by drawing a metal flat material 26 (hereinafter referred to as the material 26).

The upper die 22 is raised and lowered by the ram of the press.

A preliminary drawing punch 28 is formed in the upper die 22 so as to extend downward. The cross-sectional shape of the preliminary drawing punch 28 perpendicular to the center line is substantially similar to the bottom surface of the main body 12 of the molded product 1o, and its dimensions are larger than the outer shape of the flange 14. On the inside of the preliminary drawing punch 28, a main pattern die 30 is formed. The two dimensions of the cross section perpendicular to the center line of the main pattern die 30 are the same as the bottom surface of the main body 12.

The lower die 24 is fixedly attached to the press bolster. A preliminary drawing die 34 is formed in the lower die 24 at a position facing the preliminary drawing punch 28 . The two dimensions of the cross section perpendicular to the center line of the pre-drawing die 34 are larger than the pre-drawing punch 28 by approximately the thickness of the material 26, and as shown in FIGS. 4 and 5, its opening Slanted surfaces 38 are formed at two locations on the end including an arcuate portion and a short straight portion. Wrinkles are more likely to occur on the parts of the material that are bent into an arc shape, but on the inclined surface 3
8, the part of the material 26 closer to the outer edge is supported by the preliminary drawing die 34, so that the area of the part outside the supporting position is reduced, and the part closer to the outer edge is restrained to prevent wrinkles from forming. It is designed to suppress.

The inclination angle θ of the inclined surface 38 and the overlap distance f between the material 26 and the upper surface of the preliminary drawing die 34 are set to a size that allows drawing to be performed while avoiding the generation of wrinkles, as will be described later.

On the bottom of the preliminary drawing die 34, there is a punch 42 for making the main pattern.
is formed. The two dimensions of the cross section perpendicular to the center line of the main pattern punch 42 are the same as the two dimensions of the inside shape of the main body 12, and its upper surface is located below the upper surface of the preliminary drawing die 34.

When drawing the material 26 using the drawing die configured as described above to form the molded product 10, the material 26 is placed on the lower mold 24 with the upper mold 22 at the upper end position. Then, when the upper mold 22 is lowered, the preliminary drawing punch 28 works together with the preliminary drawing die 34 to remove the material 26.
Perform preliminary drawing. As a result, the material 26 becomes a pre-squeezed product 52 in which a pre-squeezed portion 50 extends upward from the outer periphery of the bottom portion 48 that is substantially similar to the bottom surface of the main body 12, as shown in FIG. Thereafter, as the upper die 22 is further lowered, the bottom part 48 of the preliminary drawn product 52 comes into contact with the upper surface of the punch 42 for the main pattern, and the punch 4 for the main pattern
2 and the main crest die 3o work together to apply the main crest. At this time, the bottom part 48 of the pre-drawn product 52 is squeezed, and the pre-drawn part 50 is drawn toward the main pattern punch 42, causing bending and unbending. The bent part at the boundary between the bottom part 48 and the preliminary drawing part 5° is bent back, and the preliminary drawing part 50 sandwiched between the preliminary drawing punch 28 and the preliminary drawing die 34 is newly bent. Bending and unbending occur at the same time, providing resistance to the drawing of the pre-drawn completed product 52 toward the punch 42 for final marking, and tensile force is applied to the material 52. Therefore, although the arc-shaped portion of the material 52 is naturally prone to wrinkles during drawing, by applying a tensile force, it is restricted from being pulled into the space between the punch 42 for marking the main pattern and the die 30, and the shape of the molded product 10 is restricted. The material flows to the parts that require a large amount of material for molding, and the molded product 10 is molded without wrinkles or cracks due to lack of material. When the main pattern is completed, as shown in FIG. 3, the preliminary drawn portion 50 is eliminated and the flange 14 is formed. As is clear from the above description, in this embodiment, the punch 42 and die 30 for the main pattern and the punch 28 and the die 3 for the preliminary drawing are used.
4, the preliminary drawing is completed before the main pattern starts, the length of the preliminary drawing section 50 becomes shorter as the main pattern progresses, and the preliminary drawing section 50 is closed just before the main pattern is completed. The size is set so that the aperture portion 50 is eliminated.

Further, the lap margin f when the material 26 is placed on the preliminary drawing die 34 and the inclination angle θ of the inclined surface 38 formed at the open end of the preliminary drawing die 34 are set as follows. FIG. 7 shows the results of an experiment in which the presence or absence of wrinkles on the flange was investigated when a flat circular material was formed into a flanged cylinder. As is clear from the results of this experiment,
The cone drawing rate (the drawing rate when a circular material with a diameter D is reduced to a diameter d) varies depending on the size of the material, but the value obtained by dividing the wrap allowance f by the material thickness t is between 1 and 4. The parts can be molded without creases.

Therefore, the wrap distance f may be selected to a size that allows the flange to be formed without wrinkles, but the wrap distance f varies depending on the inclination angle θ of the inclined surface 38.

The experimental results shown in FIG. 7 were obtained by changing the bevel angle θ to four types, and it is sufficient to select the wrap margin f and the inclination angle θ to a size that allows the material to be formed without wrinkles.

Further, from the experimental results shown in FIG. 7, it can be seen that in the vicinity of f/L = 3, the flange can be formed without wrinkles up to a cone drawing ratio of 0.67. And, as shown in Figure 4,
If preliminary drawing is performed at a cone drawing ratio of 0967, and further drawing is performed at a drawing ratio of 0.76 (the drawing ratio -d, /a2, d2 is the inner diameter when the main body 12 of the molded product 10 is circular), The final reduction ratio a2/D=dl/Dxdz/dl is 0.
It will be 51. This drawing rate is the limit drawing rate (0.50~0.
53), and the drawing die of this example allows the material to be drawn well.

In addition, the material 26 is bent back by bending at the shoulder part of the preliminary drawing punch 28 (outer peripheral edge of the preliminary drawing punch 28).
The stress added to 1 2 is calculated according to the following equation.

σg=(1+e〃φ') ・t/4 p d ・a.

However, μ: coefficient of friction φ,: angle L of wrapping the material 26 around the preliminary drawing punch 28: thickness pd of the material 26: L/2+rd (rd is the size of the radius) σ
0: Tensile strength of material 26, where μm0.15, φ, -π/2, t = 1.6
mm, ty d =8.8n+m (r d =8m
m), rye = 38 kg/mm2, 6 R
= 3.92 kg/mm2.

Further, when using a conventional wrinkle suppressing member and applying a wrinkle suppressing force by sandwiching the outer circumferential portion of the material together with a die to prevent wrinkles from occurring, the stress added to the material 26 is calculated according to the following equation.

σI-;μP/2Lt However, P: Wrinkle holding force L: Product length where P-20ton, L=1000mm, t=
If the cylinder is 1.6, σ is -0.94 kg/mm2. Therefore, rather than pressing the material 26 using a wrinkle suppressing member, it is possible to apply a greater pulling resistance to the material 26 by forming the pre-drawn portion 50 and causing the material 26 to bend back, thereby effectively suppressing the generation of wrinkles. This can be avoided.

Furthermore, if the molded product 10 is formed by subjecting the material 26 to preliminary drawing and final marking in this manner, deformation resistance can be kept low. FIG. 8 shows the deformation resistance during molding of the material 26. The deformation resistance is mainly caused by contraction of the outer peripheral portion of the material 26 as the drawing progresses. Therefore, first, when the preliminary drawn portion 50 is formed, the deformation resistance increases,
The deformation resistance remains constant until the formation of the preliminary drawn portion 50 is completed and the bottom portion 48 comes into contact with the punch 42 for the final pattern.

Then, after the bottom portion 48 comes into contact with the punch 42,
The deformation resistance increases again when the actual warping starts. However, since the material 26 has been pre-drawn in advance, the deformation resistance is kept almost constant while the pre-drawn part 50 is drawn in, and the rounded end of the outer periphery of the tip of the punch 42 The breaking strength does not exceed the breaking strength of , and eventually decreases.

Do not carry out preliminary drawing. <When molding the molded product 10 using a conventional type of wrinkle suppressing member, the deformation resistance may exceed the above-mentioned breaking strength and breakage of the material may occur, as shown by the two-dot chain line. However, with the drawing die of this embodiment, such a problem does not occur, and an inexpensive material 26 can be used.

Furthermore, in the drawing die of this embodiment, there is no need to provide a wrinkle suppressing member unlike the conventional drawing die, and the die size can be reduced, and it can be used together with the die used in other processes in the transfer press of the reservation type. This makes it possible to reduce the device cost by 1. Also,
The flexibility of the reservation line increases, making it easier to handle the load in the event of mold failure.

In addition, in the drawing die of the above embodiment, the punch 42 for forming the main pattern is located below the die 34 for preliminary drawing in the lower die 24, and the forming of the main pattern is performed after the completion of the preliminary drawing. The punch for embroidery is made to protrude above the preliminary drawing die to start the embroidery first, and the preliminary embroidery is completed before the embroidery progresses to the intermediate stage, and the embroidery progresses. The pre-drawn portion may be bent and unbended accordingly.

Further, in the above embodiment, the right side portions 16 of the main body 12 of the molded product 10 have the same width in the longitudinal direction and the same height, but in the present invention, the widths and heights are the same. It can also be applied to drawing dies for forming different molded products. For example, it can be applied to a drawing die for forming a saddle-shaped part whose distance from the flange becomes shorter at the center in the longitudinal direction of the main body, or a cylindrical part whose distance from the flange becomes longer at the center in the longitudinal direction.

In addition, the present invention can be implemented with various modifications and improvements based on the knowledge of those skilled in the art without departing from the scope of the claims.

[Brief explanation of the drawing]

FIG. 1 is a front sectional view showing the main parts of a drawing die which is an embodiment of the present invention. FIG. 2 is a front sectional view showing a state in which preliminary drawing has been completed in the drawing die 5 6 , and FIG. 3 is a front sectional view showing a state in which the main pattern has been completed. FIG. 4 is a front sectional view of the lower die constituting the drawing die, and is a sectional view taken along line IV-IV in FIG. FIG. 5 is a perspective view of the lower die. FIG. 6 is a perspective view showing a molded product formed by the drawing die. FIG. 7 is a graph showing experimental results on the occurrence of wrinkles when forming a flanged cylinder. FIG. 8 is a graph showing the deformation resistance of the material that occurs during drawing with the drawing die in comparison with the conventional one. 22: Upper mold 26: Flat material 30: Die for main pattern 42: Punch for main pattern 24: Lower mold 28: Punch for preliminary drawing 34: Die for preliminary drawing

Claims (1)

[Scope of Claims] A first type having a punch for applying a drawing to a flat material, and a die for preliminary drawing provided integrally on the outside of the punch for forming a main pattern; A die for making a bookmark is provided so as to be able to approach and separate from the die, and works together with the punch for making a bookmark to apply a bookmark to the material, and a die for making a bookmark is provided integrally on the outside of the die for making a bookmark. ,
a second die having a preliminary drawing punch that performs preliminary drawing on the outer periphery of the material in cooperation with the preliminary drawing die to form a preliminary drawing section extending in the approach/separation direction; The shapes and dimensions of the punch and die for marking and the punch and die for preliminary drawing are such that the preliminary drawing part is formed at the latest by the intermediate stage of the main marking, and the length of the preliminary drawing part is the same as the original drawing part. A drawing die characterized by having a shape and dimensions that become shorter as the crest progresses.