JP2010247172A - Method of deep-drawing metal sheet cylindrically - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of deep-drawing a metal sheet cylindrically the formability of which is improved by using a servo press when applying the deep drawing cylindrically by pushing a punch into a metal sheet to be worked which is fixed with a die and a blank holder. <P>SOLUTION: A preliminary deep drawing is preliminarily performed by taking the conditions such as the materials and the shape of the die, the blank holder and the punch, and the materials, shapes and blank holding force of the metal sheet to be worked, lubricating conditions and working speed are made into the same conditions as the conditions of an actual deep drawing and for forming to the deep drawing height where a rack is generated and, and after measuring the height between a position of the crack generated on a preliminarily deep drawn article and the top of the deep drawing, a stage for once separating the die or the blank holder from the metal sheet to be worked is interposed between passing the shoulder R of the punch to be used and arrival at the height to the drawing position where the crack is generated when the actual deep drawing. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a cylindrical deep drawing method for a metal plate in which formability is improved by once separating a mold from a material immediately before the height of a cracking position during drawing.

As a method for manufacturing automobile parts and home appliance parts, a method of pressing a thin metal plate material is often used. Among the press working methods, there are (1) a drawing method and (2) an overhanging method.
Drawing is a plastic working that draws the outer periphery of the blank material into a die while drawing it into the die, and generally has a case of up to about 2 to 2.5 times the punch size even if the size of the blank is large. It is used for forming a shape with little or no flange after forming.
The overhanging process is a plastic process in which the size of the blank is considerably larger than the size of the punch, the flange hardly moves into the die during molding, and processing is performed only by elongation deformation of the material in the region where the punch is projected.

In press processing, formability is improved by traditionally performing inching molding that stops the slide in the middle of processing, or repeated stroke molding that molds to the bottom dead center while repeatedly raising and lowering the slide several times during processing. It is known.
The former improves the formability by performing an inching operation so that distortion occurs in a portion different from the portion where the strain is once concentrated.
The latter is a method that is possible with a type that allows manual operation of the slide, such as a hydraulic press, for example. In addition to the former effect, oil shortage generated under high surface pressure is eliminated by separating the mold and work material. As a result, the formability is improved as a result of the restoration of the lubricity. When molding is very difficult, the operator may apply lubricant to the material surface after raising the slide.

  For example, as can be seen in Patent Document 1, in a press molding method in which a metal plate is clamped with a punch and a die, the punch first reaches the stroke end after the punch first contacts the metal plate and molding starts. In the press forming method, the operation of once separating the punch from the metal plate and forming the metal plate again using the punch and the die is performed at least once before the forming is completed. Proposed.

By the way, as a press method of a press machine, conventionally, two methods of a hydraulic press and a crank press have been mainstream.
The hydraulic press is suitable for deep drawing because it can be molded at low speed, but its productivity is low. On the other hand, the crank press has an advantage that it is excellent in productivity because of its high processing speed, but there is also a drawback that cracking tends to occur when the processing speed is high. For this reason, in order to improve the deep drawing workability of the crank press, a link motion press provided with a link mechanism to reduce the processing speed during deep drawing is also used (for example, see Non-Patent Document 1).

  More recently, for example, as shown in Patent Document 2, a servo press capable of arbitrarily setting a slide motion using an AC servo motor as a drive source is also used.

JP 2005-199318 A JP 2002-263742 A

Nakada Hiroyasu, “Theory and Practice of Press”, Corona Co., Ltd., February 20, 1973, p.171

So far, in press processing, the lower the slide speed during processing, the better the moldability, so even with link motion etc., the slide speed is slow until the press processing is completed, and the slide speed is increased after passing the bottom dead center. The motion to do was adopted.
Recently, servo presses that are frequently used use an AC servo motor as a drive source, and therefore can perform forward rotation, reverse rotation, stop, speed switching, and the like of a slide arbitrarily. In addition, it can be expected to reduce noise and improve the die life by adjusting the processing speed during press working.

The method proposed in Patent Document 1 is effective in terms of improving moldability. However, since the timing for once separating the mold in the middle of processing from the metal plate to be processed has not been clarified, if the timing for once separating the mold from the metal plate to be processed is not appropriate, the workability improvement effect cannot be sufficiently obtained. It will be.
The present invention has been devised to solve such a problem. When a cylindrical deep drawing process is performed by pressing a punch into a metal plate to be processed, a timing for once separating the die or the plate presser from the metal plate to be processed. An object of the present invention is to provide a cylindrical deep drawing method for a metal plate with improved formability by using a servo press by setting at a point where the effect is large.

  In order to achieve the object, the cylindrical deep drawing method of the metal plate according to the present invention includes a die, a plate presser, and a presser when performing a cylindrical deep drawing by pressing a punch into a work metal plate fixed by a die and a plate presser. Preliminary forming to the deep drawing height where cracks occur in advance by setting the material and shape of the punch, the material and shape of the metal plate to be processed, the wrinkle holding force, the lubrication conditions and the processing speed conditions to the same conditions as the actual deep drawing conditions After performing deep drawing and measuring the height from the position of the crack generated in the preliminary deep drawing product to the top of the deep drawing, during the actual deep drawing, the crack R occurred past the shoulder R of the punch used. It is characterized in that a step of once separating the die or the plate presser from the metal plate to be processed is interposed until the height to the drawing position is reached.

According to the present invention, the lubricant film is regenerated and the formability is improved by interposing a step of once separating the die or the plate presser from the metal plate to be processed. Moreover, since the timing of releasing once is an effective timing for suppressing the concentration of strain at the crack-prone area, the regeneration effect of the lubricant film effectively acts on the dispersion of strain, and the deep drawability is dramatically improved. .
For this reason, by adopting a servo press, productivity is remarkably improved without slowing down the slide speed during press working.

The figure explaining the aspect which performs deep drawing processing to a metal plate, (a) At the time of normal deep drawing processing, (b) When the plate presser is separated from the metal plate to be processed (A) The figure explaining the cross-sectional shape of the molded product after preliminary deep drawing, (b) The figure explaining the timing which separates a plate retainer from a processed metal plate

Generally, in the drawing process, as the processing proceeds, the flange part runs out of oil, so that the slidability of the flange part decreases.
Therefore, when performing the drawing process, the lubricant film on the surface of the metal plate to be processed is regenerated by separating the mold from the metal plate to be processed during the processing (Patent Document 1).
The present inventors refer to the metal plate press forming method described in Patent Document 1, and use a servo press that can freely set the motion of a slide, thereby enabling deep drawing in cylindrical deep drawing. The effect of the timing of mold release on the metal was investigated and the present invention was reached.
As a result, the height from the position of the crack generated in the preliminary deep drawing product to the top of the deep drawing is measured, and during the actual deep drawing, the shoulder R of the punch used is passed to the drawing position where the crack has occurred. It has been found that the deep drawability is improved by once separating the die or the plate retainer from the workpiece metal plate until the height is reached.
Details will be described below.

First, a hot dip galvanized steel sheet with a thickness of 0.8 mm was used as a test material, and a cylindrical deep drawing process with a punch diameter of 103 mm and a forming height of 78 mm was performed using a blank cut into a circle with a diameter of 210 mm. The die was φ105 mm and the shoulder R (Rd) of the die was 2 mm. The punch shoulder R (Rp) was 5 mm. Noxlast 3060 manufactured by Parker Kosan Co., Ltd. was used as the press oil, and single motion cylindrical deep drawing was performed at a wrinkle pressing force: 100 kN, slide speed: 20 spm.
In this deep drawing, when the drawing depth became 23 mm, a crack occurred at a position 19 mm from the top of the cylindrical surface.

Next, deep drawing was performed again under the same conditions. Here, the condition of once separating the plate retainer from the workpiece metal plate at a molding height of 5 mm and the step of once separating the plate retainer from the workpiece metal plate at a molding height of 23 mm are sandwiched. I tried two types of deep drawing under conditions.
In the former, it was possible to draw out with a deep drawing height of 78 mm. On the other hand, in the latter, cracking occurred when the drawing depth reached 40 mm.

  As described above, as shown in FIG. 1B, the step of once separating the plate retainer from the metal plate to be processed is performed at a time before forming to a height up to the crack position generated in the deep drawing processing of only one step. By interposing, the deep drawability can be greatly improved. FIG. 1A shows the situation during deep drawing. Details will be given in the description of the embodiment, but under exactly the same conditions, the drawing height is set to the height H from the crack generation position generated in the preliminary deep drawing product to the top of the drawing (see FIG. 2A). It has been found that it is effective to intervene a step of once separating the plate presser from the metal plate to be processed at a time point until reaching (see FIG. 2B).

  In drawing, cracks occur at sites where distortion is concentrated and the amount of deformation is large. The position where the strain concentrates varies depending on the shape of the mold, the wrinkle pressing force, the material characteristics, the lubrication conditions, the processing speed, and the like. For example, in the cylindrical deep drawing of the above hot dip galvanized steel sheet, it is considered that the position at a height of 19 mm from the deep drawing top, which is a cracked portion, corresponds to a portion where distortion is concentrated and the amount of deformation is large. Further, in the drawing process, since the material is not restrained from the punch at the part past the shoulder R of the punch, the strain tends to concentrate. Therefore, just before processing the part where strain tends to concentrate, it is the timing with the most effective improvement in formability that the plate presser is once separated from the material to release the pressing force between the plate presser and the die and restore the lubricity. I can say that. On the contrary, even if the plate presser is once separated from the material before the portion where the restraint by the punch is removed is processed, the effect of improving the formability is hardly recognized. Although details of setting the timing are also given in the description of the embodiment, before the forming depth reaches a depth corresponding to the shoulder R of the punch used, the effect of improving the formability is not recognized.

When drawing is performed by pressing the punch against the metal plate to be processed by continuous one-stroke slide movement, the surface of the metal plate to be processed, the plate presser, and the die surface slide while being pressed against each other. As the molding progresses, the lubricant film that exists between the plate retainer and the die surface and the metal plate surface to be processed becomes thin at the start of molding. Will be in contact.
As the oil film thickness decreases in the process, the lubricity decreases, so the coefficient of friction between the surface of the metal plate to be processed and the plate retainer and die surface increases, the lubricity decreases and the metal plate to be processed cracks. Cause it to occur.
And the crack occurs in the part where distortion tends to concentrate most.

Thus, it is considered that deep drawing formability can be improved by grasping in advance the part where distortion is most likely to concentrate and improving the lubricity when processing the part during deep drawing.
First, as means for improving lubricity, means for once separating the plate retainer from the metal plate to be processed is employed. When the plate retainer is separated from the workpiece metal plate, the pressing force between the plate retainer and the die is released, and the effect that distortion occurs in the part other than the part where the strain has once concentrated, the plate retainer and the die surface It is considered that the formability is improved by the effect that the lubricant that has been confined at a high pressure in the fine recesses of the metal plate or in the fine recesses of the surface of the metal plate appears on the surface to regenerate the lubricant film and improve the lubricity. . Even if the step of separating the die from the metal plate to be processed instead of the step of separating the plate retainer from the metal plate to be processed is adopted, the same effect can be expected.

The part where the distortion is most likely to be concentrated can be known by measuring the height from the top of the drawing to the position where the crack occurs when deep drawing is performed by continuous one-stroke slide movement.
When deep drawing is performed by continuous one-stroke slide movement, a step of once separating the plate retainer and the die from the workpiece metal plate is formed before forming from the crack occurrence position to the height of the drawing top. The good reason is that when deep drawing is performed by continuous one-stroke slide movement, the height from the crack occurrence position to the top of the drawing and the position where the strain concentrates are almost the same, and the plate just before the strain concentrates. It is considered that the most effective improvement in moldability is to release the presser or die from the material to restore the lubricity.

The areas where strain is most likely to concentrate are the physical properties of the metal plate, including the mechanical properties of the material, the surface condition, etc., the mold characteristics including the surface condition of the mold, the usage status of the lubricant, or the processing speed. It varies greatly depending on.
Therefore, a preliminary experiment was performed in which the metal plate, die, crease presser force, lubricant used, and processing speed to be actually deep drawn were exactly the same, and the crack occurrence position according to the conditions. It is necessary to know in advance the height H from the top to the throttle top.

In the conventional mechanical press, it is difficult to once separate the plate retainer or the die from the material during the molding, and even in the hydraulic press, it is difficult to automatically perform such repeated stroke motion. Therefore, if the servo press is capable of arbitrarily setting the slide motion using an AC servo motor as the drive source, the plate presser or the die can be once separated from the material during the molding, which improves the moldability. The plate holder or die is once released from the material at an effective timing (before forming from the crack occurrence position to the top of the drawing when deep drawing is performed by continuous one-stroke slide movement). be able to.
In addition, as described above, before the portion where the restriction by the punch is removed is processed, specifically, before the drawing depth reaches a depth corresponding to the shoulder R of the punch to be used, the plate presser or the die is moved. Even if it is once separated from the material, the effect of improving the formability is hardly recognized.

As a test material, a hot-dip galvanized steel sheet with a thickness of 0.8 mm was used, a blank cut into a circle with a diameter of 210 mm was used, and a cylindrical deep drawing process with a punch diameter of 103 mm and a die diameter of 105 mm was performed with a forming height of 78 mm. . The punch shoulder R (Rp) was changed into three types of 5 mm, 10 mm, and 20 mm, and cylindrical deep drawing was performed. The die shoulder R (Rd) was 2 mm.
The Noxlast 3060 was used as the press oil, and single motion cylindrical deep drawing was performed at a wrinkle pressing force: 100 kN, slide speed: 20 spm. And the cylindrical deep drawing process was completed when the crack generate | occur | produced. Thereafter, the deep drawing height was measured, and the height from the crack occurrence position to the top of the drawing was measured.
The results are as shown in Table 1 for the drawing depth and the height of the crack position.

Next, cylindrical deep drawing was performed again under the same conditions. However, when the drawing depth reached the height described in the timing of Table 1, a step of once separating the plate presser from the workpiece metal plate was sandwiched. And the cylindrical deep drawing process was completed when the crack generate | occur | produced. Thereafter, the deep drawing height was measured.
The results are also shown in Table 1.
From the results shown in Table 1, the process of temporarily separating the die or the plate presser from the metal plate to be processed is required until it passes the shoulder R of the punch to be used and reaches the height of the squeezed position where the crack has occurred. Is understood to be effective.

Claims (1)

  When pressing a punch into a workpiece metal plate fixed by a die and a plate retainer and performing deep drawing of the cylinder, the material and shape of the die, plate retainer and punch, the material and shape of the workpiece metal plate, the wrinkle retaining force, and lubrication Preliminary deep drawing is performed to form the deep drawing height at which cracks are generated in advance under the same conditions as the actual deep drawing conditions. After measuring the height to the top, during the actual deep drawing, the die or plate presser is covered while passing through the shoulder R of the punch to be used and reaching the height to the drawing position where the crack has occurred. A cylindrical deep drawing method for a metal plate, comprising a step of once separating from the processed metal plate.

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