JPH0252568B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for forming deep-bottomed containers, and more particularly, to a method for forming deep-bottomed containers in which redrawing is performed using a reverse redrawn counter-hydraulic method in which circumferential hydraulic pressure is applied. Deep drawing is used to make container-shaped products with bottoms, but there is a certain limit to how much drawing can be done in one process, so when forming deep containers, the drawing process is divided into several steps. A method is adopted in which a molded product is drawn to a predetermined depth from a flat plate (first drawing), and then this first drawn product is deep drawn several times (redrawing). This re-drawing method includes a direct re-drawing method and a reverse re-drawing method, but a forming method that uses a combination of initial drawing and reverse re-drawing has the advantage of requiring two fewer bends if the degree of bending is the same. A continuous reverse redrawing method that uses a first drawing punch that also serves as a redrawing die, a cushion-type blank holder, an initial drawing die, and a redrawing punch is also well known. However, since such a conventional continuous reverse redrawing method uses die drawing, the drawing ratio is low, that is, the limits are a redrawing ratio of around 1.3 and a total drawing ratio of around 2.6. Therefore, in order to improve this, a method has been adopted in which the molded product is intermediately annealed after the initial drawing, but when this method is adopted, it is necessary to take out the material for re-drawing from the press at some point. This has the drawback of not being able to be continuous and reducing machining efficiency.Furthermore, even if an intermediate annealing process is introduced, the re-drawing ratio can only be improved to around 1.8 at maximum and the total drawing ratio can only be improved to around 3.5. Ta. The present invention was devised through repeated research and experiments in order to eliminate the drawbacks of the conventional method as described above, and its purpose is to increase the re-drawing ratio without intervening a heat treatment process such as intermediate annealing. The object of the present invention is to provide a deep drawing method of this kind, which can significantly improve the process and form a container with a much deeper depth than when intermediate annealing is used in one press stroke. In order to achieve this object, the present invention performs the initial drawing by the conventional mold cushion drawing method, and then performs the reverse re-drawing in the same mold by the opposed hydraulic drawing method.
Moreover, a part of the high-pressure liquid increased during this counter-hydraulic reverse re-drawing is supplied to the flange end of the first-drawn product. This provides the effect of pushing in the axial direction and the friction reduction effect of lubrication on both sides of the side wall and bottom. That is, the features of the present invention include a punch that also serves as a redrawing die and has a hydraulic chamber formed in the axial direction from the upper surface, and a blank plate is mounted on a cushion-type blank holder on the outer periphery of the punch, and Conventional cushion drawing is performed using the die for initial drawing facing the die and the punch, and the crease pressing gap formed between the bottom of the die for initial drawing or the lower surface of the blank holder for re-drawing in place of this and the upper surface of the punch is the plate thickness t ₀ 1.05 to 1.20t ₀ and then push the re-drawing punch into the hydraulic pressure chamber, and the hydraulic pressure in the hydraulic chamber is applied to the ring between the punch and the first drawing die through a bypass passage passing through the side wall of the punch. Pressing the first drawing product in the side wall axial direction by flowing it into the sliding gap around the re-drawing punch through the wrinkle presser gap,
The purpose of this method is to perform reverse re-drawing using opposed hydraulic pressure while fluidly lubricating both sides of the side wall and bottom of the initial drawn product in the plate thickness direction. Embodiments of the present invention will be described below with reference to the accompanying drawings. The method of forming deep-bottomed containers using circumferential pressure reverse re-drawing according to the present invention basically involves the initial drawing (flat plate drawing) process (Figs. 1 to 3) using the conventional mold cushion drawing method. , and an opposing hydraulic pressure reverse re-throttling stroke (FIGS. 4 and 5) by applying circumferential hydraulic pressure. Specifically, the initial drawing is performed by a die 10 for the initial drawing attached to the outer slide 18, a blank holder 50 for the initial drawing on the cushion pin 22 that penetrates the bed 21, and this blank holder 50 sliding along the outer periphery. The re-drawing is performed using the punch 1 (which also serves as a re-drawing die) fixed on the bed 21 in such a manner that the re-drawing punch 4 is attached to the inner slide 17 and the first drawing die. 10
a re-drawing blank holder 5 fixed integrally with or separately from the punch 1; and a hydraulic chamber 2 provided inside the punch 1.
This is done by In order to apply circumferential hydraulic pressure during this re-squeezing, the present invention provides bypass passages 9, 9 which are bored at multiple locations through the side wall of the punch, communicating with the hydraulic pressure chamber 2 and the end of the reduced diameter outer surface of the punch. Also, a sealing gasket 23 is provided on the outer peripheral surface of the punch below the bypass passages 9, 9.
is installed. However, when forming deep-bottomed containers, the first
As shown in the figure, raise the cushion pin 22 and raise the blank holder 50 to a position where its holder surface is aligned with the upper surface of the punch 1. Supply liquid. This liquid simultaneously passes through the bypass passages 9, 9 and fills the cylindrical gap between the inner diameter surface of the blank holder 50 and the diameter reduction punch outer surface of the punch 1. Next, the material W is mounted on the blank holder 50 and the upper surface of the punch 1, the outer slide 18 is lowered, the material W is sandwiched between the initial drawing die 10 and the blank holder 50, and a wrinkle pressing force is applied as shown in FIG. While feeding through the cushion pin 22, the initial drawing die 10 is lowered to perform cushion drawing. The material W is punched 1 by lowering the first drawing die 10.
While being wrapped around, it is squeezed into the first drawing die,
As shown in FIG. 3, when the blank holder 50 is pushed down to its lower limit, a cup-shaped first drawing product _W1 is obtained. In the above stroke, the punch diameter reduced outer surface 1 is passed through the hydraulic pressure chamber and bypass passage of the punch 1.
The liquid filling the gap between the inner surface 501 of the blank holder 50 and the sealing gasket 23 attached to the outer surface of the punch is caused by the contact between the sealing gasket 23 attached to the outer surface of the punch and the inner surface of the blank holder, and by the wrinkles acting on the initial drawing die 10 and the blank holder 50. At the stage where the liquid is sealed by the pressing force and the initial squeezing is completed, the liquid is passed through the initial squeezing die 10.
The punch is sealed in a ring-shaped sealing gap 7 formed by the inner surface 101 of the punch, the reduced-diameter outer surface 11 of the punch, and the stepped portion 13 at the starting end of the reduced-diameter outer surface of the punch. Next, the first drawing product W ₁ obtained in the previous step is held between the first drawing die 10 and the punch 1 and subjected to reverse re-drawing. That is, first, the outer slide 18 pressurizes the bottom of the initial drawing die 10 or the redrawing blank holder 5 provided in place of the bottom to apply the creasing force necessary for reverse redrawing between it and the top surface of the punch 1. let Then inner slide 1
7 to lower the re-drawing punch 4 and push it into the hydraulic chamber 2 through the bottom of the first-drawing die 10 or through the central hole 52 of the re-drawing blank holder 5.
Start counter hydraulic pressure reverse re-throttling. The hydraulic chamber 2 is closed by pushing the re-squeezing punch 4.
The liquid inside is increased in pressure to generate a counter hydraulic pressure Pc, and as shown in _FIGS . The bottom of the container is formed by tightly wrapping it around the shoulder, and the side wall is formed by subsequent pressing with the re-drawing punch 4 while producing the frictional retention effect that is an advantage of the opposed hydraulic drawing method. At this time, a part of the pressurized liquid flows to the upper surface of the punch through the gap between the shoulder of the punch (re-drawing die here) 1 and the material, thereby causing the side walls and bottom of the first drawn product W ₁ to Each lower surface is hydrodynamically lubricated. Normal opposed hydraulic throttle stops at this, but
As mentioned above, the present invention connects the hydraulic pressure chamber 2 and the gap 7 on the outer periphery of the diameter reducing punch outer surface 11 to the bypass passages 9, 9.
It is tied by Therefore, the re-drawing punch 4
As shown in Fig. 6, a part of the opposing hydraulic pressure Pc ₁ increased by the pushing is press-fitted into the end of the ring-shaped gap 7 on the outer surface of the punch from the bypass passage 9, and this circumferential hydraulic pressure Pc ₁
acts directly on the side wall of the first drawn product _W1 as a compressive force, pressing the side wall end Wc in the axial direction. and,
The circumferential liquid pressure Pc ₁ passes through the side wall outer surface and the bottom outer surface of the first drawing product W ₁ and is composed of the redrawing punch 4 and the bottom of the first drawing die or the hole wall of the redrawing blank holder 5. It flows upward from the gap 52.
During this time, the side wall outer surface and the bottom outer surface of the first drawn product W ₁ are fluid-lubricated. In this way, in the present invention, by performing the re-reverse drawing with opposed hydraulic pressure drawing, not only can the friction retention effect of the punch shoulder and side wall parts be obtained, but also a part of the opposed hydraulic pressure can be applied to the first drawn product W. By supplying _{W 1} to the edge of the ring-shaped gap between the punch 1 containing W 1 and the initial drawing die 10, the side wall of the initial drawing product W ₁ is actively pushed in the axial direction. The tensile force generated on the side wall of the molded product is reduced, and at the same time, both the side wall and bottom of the first drawn product _W1 are effectively fluid-lubricated. Therefore, due to these synergistic effects, the redrawing ratio is greatly improved, and a container _W2 with a deep bottom as illustrated in FIG. 5 is formed in one process. The method of pressurizing the hydraulic chamber 2 in the reverse re-restriction stroke may be a natural pressure increase method by pushing the re-restriction punch 4, as shown in FIGS. 4 and 5. If the pressure is insufficient just by pushing in, check the pressure when the first drawing is completed (the third
A forced pressure increase method may be adopted in which the pressure in the hydraulic chamber 2 is forcibly increased using a pump or the like in the state shown in the figure), and then a punch is pushed in. Further, as the wrinkle pressing method in the reverse re-drawing process, either a fixed wrinkle pressing method or a pressure wrinkle pressing method may be adopted. In this embodiment, the bed 21
A fixed wrinkle pressing method is adopted by interposing a spacer 24 between the blank holder 5a and the blank holder 5a. The spacer 24 may be a ring-shaped spacer with a hole through which the cushion pin 22 passes, or
Blank holder 50 for initial drawing of spacers without holes
The spacer may be fixed to the lower surface of the spacer with an embedded bolt or the like, and the spacer may be pushed up together with the blank holder 50 for initial drawing using the cushion pin 22.
In the case of this fixed wrinkle holding method, forming is performed while maintaining a constant gap between the bottom of the initial drawing die or the blank holder 5 for redrawing and the punch 1, thereby simplifying the forming apparatus. In the case of using the pressure wrinkle pressing method, the spacer 24 may be removed and the wrinkle pressing pressure by the outer slide 18 may be controlled as the hydraulic pressure in the hydraulic chamber 2 increases. In addition, if the wrinkle presser clearance Ch (the clearance between the bottom of the initial drawing die or the lower surface 51 of the redrawing blank holder 5 and the upper surface 100 of the punch) in the reverse redrawing process using the fixed wrinkle presser method is too small, the wrinkle presser is too strong, fluid lubrication by the hydraulic pressure Pc ₁ cannot be performed smoothly, and the rupture limit decreases. On the other hand, if the crease presser gap Ch is too large than necessary, the decrease in hydraulic pressure from the set hydraulic pressure will be large, and the breaking limit will be lowered due to insufficient hydraulic pressure. According to the studies conducted by the present inventors, the wrinkle holding gap Ch is 1.05 to 1.20t ₀ in relation to the material plate thickness t ₀
In the range of , the above-mentioned friction retention effect + side wall pressing effect + double-sided lubrication effect was fully exhibited. 7 and 8 show an embodiment in which a forming tool is attached to a double-acting press with a cushion in order to carry out the method of the present invention described above. , and this guide hole 10
0 is connected to an external hydraulic pressure control device 12. The hydraulic pressure control device 12 is limited to the circuit configuration of the embodiment as long as it has a pump 16 for sending liquid into the hydraulic pressure chamber 2 and a control valve 14 for setting the hydraulic pressure in the hydraulic pressure chamber 2 to a predetermined value. Not done. In this embodiment, a blank holder 5 for re-drawing is fixed to the upper part of the die 10 for initial drawing, and a sealing gasket 23 is interposed between the contact surfaces thereof. Further, a spacer 24 for fixed wrinkle pressing is attached to the lower surface of the blank holder 50. Next, specific examples of the present invention will be shown. EXAMPLE Using the experimental apparatus shown in FIGS. 7 and 8, a container with a deep bottom was molded according to the present invention by a reverse redrawing method. (1) The press is a double-acting hydraulic press with a cushion (inner 80 tons, outer 50 tons, cushion 50 tons)
was used. (2) The material used was A11000 with a nominal thickness of 0.8 mm. Its mechanical properties are shown in Table 1 below.

[Table] (3) The initial squeezing conditions are as follows. Punch diameter; d _p1 = 75mmφ Die hole diameter for initial drawing: d _d1 = 77mmφ Punch shoulder radius: r _p1 = R6 Die shoulder radius for initial drawing: r _d1 = R5 Lubricating oil: High viscosity oil (manufactured by Nippon Craft Oil Co., Ltd.)
G630A) Wrinkle holding force: 10000 Kgf The drawing ratio (D ₀ /d _p1 ) was changed by changing the material diameter while keeping the tool constant. (4) The reverse re-drawing conditions are as follows, and the change in the re-drawing ratio is as follows: d _p1 , d _d1 are kept constant, d _p2 ,
This was done by varying d _d2 . Diameter of punch for redrawing: d _p2 = 30, 32, 34,
36mmφ Die hole diameter (punch hole diameter at initial drawing): d _d2 = 32, 34, 36, 38mmφ Die hole depth: 215mm Punch shoulder radius for re-drawing: r _p2 = R5 Die shoulder radius: r _d2 = R5 Re Squeezing punch length: 200mm (actually 175mm) Wrinkle holding method: Fixed wrinkle holding method Pressure increase method: Forced pressure boosting Fluid for opposing hydraulic pressure: Hydraulic oil (manufactured by Nippon Oil Co., Ltd., product name Super Hyland 32) Bypass passage: Four axially symmetrical locations each with a diameter of 6 mm. First, the forming situation when the initial drawing was performed under the condition (3) above is shown in FIG. 9. Therefore, the successful range of initial aperture ratio D ₀ /d _p1 is 1.8~
2.15, the redrawing ratio d _p1 /d _p2 is 2.34, the wrinkle holding gap Ch is _1.20t0 , and the forming situation is shown when the initial drawing-peripheral hydraulic pressure reverse re-drawing method is carried out according to the present invention. FIG. 10 shows the same, and FIG. 11 shows the molding situation when the redrawing ratio d _p1 /d _p2 was set to 2.5 and the wrinkle presser gap Ch was set to 1.15t ₀ . As is clear from these FIGS. 10 and 11, when the present invention is used, the re-drawing ratio
d _p1 /d _p2 can be significantly improved compared to the conventional method of around 1.3, and the total aperture ratio D ₀ /
_dp2 has been improved to more than 4.9, nearly double the conventional method's maximum of around 2.6. In this example, the minimum redrawing punch diameter was 30 mmφ and the die hole diameter was 32 mmφ, so the redrawing ratio was only about 2.5 and the total drawing ratio was about 4.9. If you make it small,
It is fully possible to form the product up to a re-drawing ratio of about 2.6 and a total drawing ratio of about 5.3. Next, in order to confirm the effect of applying circumferential hydraulic pressure according to the present invention, in (4) above, a bypass passage was not provided, the wrinkle presser was a constant pressure wrinkle presser, and other conditions were kept the same, and no circumferential hydraulic pressure was applied. I tried the opposing hydraulic pressure reverse re-squeezing method (comparative method). As a result, Fig. 12 shows the forming situation when the re-drawing ratio P _p1 /d _p2 was set to 2.08, and Fig. 13 shows the forming situation when the re-drawing ratio was increased to 2.21. It is. As is clear from these Figures 12 and 13, when reverse redrawing is performed using opposing hydraulic pressure, the redrawing ratio is improved to about 2.2 compared to the conventional mold usage method, and the total Aperture ratio _D0 / _dp2 is 4.0~
It is improved to about 4.2. However, this comparative method is also less effective in improving the redraw ratio than the method of the present invention which applies peripheral fluid pressure. In the case of the comparative method, this difference is only due to the friction retention effect due to opposing hydraulic pressure and the lubrication effect on one side of the first drawn product. (In the initial drawing stroke, breakage is likely to occur at the punch hole).
In the present invention, in addition to the above-mentioned comparative method, the pushing effect of the peripheral liquid pressure on the side wall of the first drawn product and the friction reduction effect of lubrication on the remaining surface of the first drawn product act synergistically. As a result, early breakage is less likely to occur, and the re-drawing ratio and total drawing ratio are improved. Another method is to insert an annular protrusion into the bottom of the blank plate from above and below during the initial drawing, sealingly isolate the top and bottom surfaces of the blank plate from the surrounding areas, and operate the piston in this state to create a ring-shaped high pressure. The pressure in the chamber is increased, and the ram is pushed in while applying high hydrostatic pressure to the pressure chamber on the outside of the blank sealed by the protrusion, and the pressure chamber applies high hydrostatic pressure to the peripheral end surface of the blank, causing the blank to form an annular protrusion. If the method was to push the material into the cavity by biting it into the cavity as if it were being stretched with an iron, and then discharge the liquid pressure inside the cavity from the bottom through a passage and a check valve into the apparatus, extremely high pressure would be required for molding. Since the friction holding effect and the double-sided lubrication effect by hydraulic pressure are not required only by the circumferential pressing effect, the breaking limit is low and it is impossible to achieve the drawing ratio as in the present invention. In addition, the opposing hydraulic pressure is simply discharged to the outside of the device and is not involved in circumferential pressing, and requires a special piston, ring-shaped high pressure chamber, etc. for circumferential pressing, which complicates the mechanism. The problem is that the pressure chamber and piston must be controlled separately, making the circuit and operation complicated. According to the present invention as described above, bypass passages 9, 9 are provided in the side wall of the punch 1, passing through the side wall of the punch 1, instead of simply performing the initial drawing in the conventional manner and then performing reverse re-drawing by applying hydraulic pressure from the circumferential direction. At the time of re-drawing, the hydraulic pressure in the hydraulic chamber increased by pushing the re-drawing punch 4 is discharged into the ring-shaped gap 7 between the punch 1 and the initial drawing die 10 through the bypass passages 9, 9, and the wrinkles are removed. Presser gap Ch (first drawing die 10
The clearance between the bottom surface 51 of the re-drawing blank holder 5 and the top surface 100 of the punch is intentionally set large, that is, it is set to 1.05 to _1.20t0 in relation to the material plate thickness _t0 . In order to cause the liquid pressure that has flowed into the ring-shaped gap 7 to flow out into the sliding gap 52 of the re-squeezing punch 5, this opposing liquid pressure presses the side wall end Wc, and at the same time, while it flows out from the wrinkle holding gap Ch, the side wall Wb , the upper surface of the bottom wall Wa is fluid-lubricated, and at the same time, the opposing hydraulic pressure in the hydraulic pressure chamber 2 flows to the upper surface of the punch via the punch shoulder, so that the side wall
Wb, the lower surface of the bottom wall Wa is provided with fluid lubrication, and
In the hydraulic pressure chamber 2, the opposing hydraulic pressure acts on the punch shoulder and side wall of the blank plate, so a friction retention effect is obtained, and this friction retention effect, side wall axial direction pressurizing effect, and side wall Wb of the first drawn product _W1 Due to the synergistic effect of the double-sided lubrication effect of the bottom part Wa and the bottom part Wa, deep-bottom containers with extremely high re-drawing ratios and total drawing ratios can be formed efficiently at low pressure. Moreover, despite this effect, the hydraulic pressure for circumferential pressing and double-sided lubrication is obtained by forming the bypass passages 9, 9 that penetrate the side wall of the punch 1, that is, the creation of a hydraulic chamber. This is achieved by effectively utilizing opposing hydraulic pressure, and therefore has a simple structure and can be implemented easily and inexpensively, providing excellent effects.

[Brief explanation of the drawing]

Figures 1 to 5 are cross-sectional views showing step-by-step an embodiment of a method for forming deep-bottomed containers using circumferential hydraulic pressure reverse redrawing according to the present invention, and Figure 6 is a counter-hydraulic reverse redrawing process. FIG. 7 is a half-sectional view showing the circumferential hydraulic pressure supply situation at each stage; FIG.
The figure is a sectional view taken along the line of Fig. 7, and Fig. 9 is a graph showing the forming situation of the initial drawing process in the present invention.
Figures 10 and 11 are graphs showing the forming situation in the reverse redrawing process of the present invention, and Figures 12 and 13 are graphs showing the forming situation when reverse redrawing using opposing hydraulic pressure is performed without using circumferential hydraulic pressure. This is a graph showing the situation. 1...Punch that doubles as a re-drawing die, 10...
Die for initial drawing, 2... Hydraulic pressure chamber, 5... Blank holder for reverse re-drawing, 50... Blank holder for initial drawing, 7... Gap, 9... Bypass passage, 52...
...Gap, 100...Top surface of punch, _W1 ...First drawing product, Wa...Bottom, Wb...Side wall, Wc...Side end wall.

Claims (1)

[Claims] 1. A blank sheet W is mounted on a punch 1 which also serves as a re-drawing die and a cushion-type blank holder 50 on the outer periphery of the punch, in which a hydraulic chamber 2 is formed in the axial direction from the top surface, and a blank holder W is mounted on the blank holder 50 and a first sheet facing the blank holder 50. Conventional cushion drawing is performed using the drawing die 10 and the punch 1, and the wrinkle holding gap Ch formed between the bottom of the initial drawing die 10 or the lower surface 51 of the re-drawing blank holder 5, which is an alternative thereto, and the upper surface 100 of the punch is formed on the plate. The re-squeezing punch ₄ is then set to 1.05 to 1.20t0 in relation to the thickness _t0 , and the re-squeezing punch 4 is pushed into the hydraulic pressure chamber 2, and the hydraulic pressure in the hydraulic pressure chamber is controlled by the bypass passages 9, 9 passing through the side wall of the punch 1. It flows out into the ring-shaped gap 7 between the punch 1 and the initial drawing die 10,
By flowing this into the sliding gap 52 around the re-drawing punch 4 through the wrinkle holding gap Ch, pressure is applied in the axial direction of the side wall of the first drawn product and the side wall Wb and bottom Wa of the first drawn product are A method for forming deep-bottom containers using circumferential hydraulic reverse redrawing, which is characterized by performing counter hydraulic reverse redrawing while fluid lubrication is applied to both surfaces in the thickness direction.