JPH04351231A - Redrawing method - Google Patents

Abstract

PURPOSE:To provide the redrawing method by which the development of folds is prevented, the development of shock line is reduced and the development of black seam is provented in a redrawing work in a deep drawing work, particularly, manufacture of two pieces-drink-can body for beer, etc. CONSTITUTION:By using a fold restrainer 2' having shoulder redius smaller than shoulder redius at the bottom part of a blank 4 formed in cup-state, the shoulder part at the bottom part of the cup 4 is formed with this fold restrainer 2' just before drawing of redrawing work and successively, the redrawing work is executed with a punch 1.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to redrawing in deep drawing, and in particular to two-piece beverage can bodies for beer, juice, carbonated drinks, etc., which are produced using drawing or drawing and ironing. It concerns a method suitable for manufacturing.

0002

[Prior Art] In deep drawing processing for manufacturing cylinder bodies, etc.,
There is a deep drawing limit to the depth that can be obtained from a blank in one deep drawing process. For this reason, if a depth exceeding the limit is required, the drawing process is divided into several stages. At first, the blank is drawn to a medium level to form a bottomed cylindrical body (hereinafter referred to as a cup). A so-called re-drawing process is being carried out in which the material is further drawn.

[0003] Cans manufactured by such a redrawing process include so-called two-piece beverage cans, which are widely used for beer, juice, carbonated drinks, and the like. This is a DR process in which a metal blank such as aluminum alloy is once drawn and formed, and then the cup is re-drawn and formed.
There are cans, DI cans, etc. manufactured by sequentially performing re-drawing and ironing.

For example, DI cans are normally manufactured by drawing twice and ironing two to three times, as shown in FIG. This is done by first punching out a blank as shown in Figure 3(a) from a flat plate of material using a press called a cupping press, and then punching out the blank as shown in Figure 3(a).
The first-stage drawing process (cupping) in which the material is drawn into a relatively shallow cup as shown in (b) is performed in one stroke. Next, a can-dedicated forming machine, generally called a body maker, continuously performs a second drawing process, that is, a re-drawing process, two to three stages of ironing process, and doming (bottom forming) in one stroke. Cans are usually produced at a rate of 100 to 200 cans/min. This re-drawing process is performed using dies, punches, and wrinkle presses in the same way as the first stage, and the shallow cup shown in Figure 3(b) formed by the cupping press is drawn into the deep cup shape shown in Figure 3(c). . In addition, the ironing process involves using two to three ring-shaped dies and a cylindrical punch to thin the side wall of the cup shown in Figure 3(c) and forming it into a can as shown in Figure 3(d).
Furthermore, use a doming die to process the bottom into a dome shape.

The mold configuration for this redrawing process consists of a punch 1, a die 3, and a wrinkle presser 2, as shown in FIG. The wrinkle presser 2 is inserted into the inner surface of the molded cup 4 as shown in FIG. The shoulder part has the effect of bending and unbending the blank. Therefore, the wrinkle presser used during this re-drawing process is usually made in a shape that makes contact with the inner surface of the cup.

[0006]

Problems to be Solved by the Invention In the process of making cans by the above-mentioned redrawing process, breakage during the drawing or redrawing process sometimes occurs, which is called "can breakage." If this can breakage occurs at a body maker, for example, it will cost 100 to 20
The operation that had been manufacturing at a rate of 0 cans per minute is interrupted, and since fragments remain in the body maker, it takes time to remove them, resulting in a significant drop in productivity. Furthermore, during the re-drawing process, dark-colored areas generally called "black streaks" may occur on the side wall of the can. These black streaks impair the appearance quality of the can, thereby lowering its commercial value.

[0007] As a result of intensive research, the inventor found that the above-described defects occur due to the mismatch in shape between the cup and a mold such as a punch, die, or wrinkle presser. This will be explained below with reference to the drawings. FIG. 4 is a cross-sectional view showing the re-drawing process using a conventional mold configuration. The re-drawing process involves re-drawing a blank formed into a cup shape using a mold configuration consisting of a punch, a die, and a wrinkle holder. Since the shoulder radius of the crease presser 2 is larger than the shoulder radius of the bottom of the cup 4, a gap 5 exists between the crease presser 2 and the shoulder of the bottom of the cup 4 from the beginning. If there is a gap 5 at the bottom of the cup, the cup cannot be sufficiently restrained during the re-squeezing process, and sufficient wrinkle-pressing force is not applied, which causes wrinkles to form around the shoulder of the bottom of the cup. Among the wrinkles that occur, the wrinkles that appear on the flange part in the latter stages of re-drawing are caused by the ironing action of the re-drawing punch and re-drawing die because the plate thickness of the flange part has become thicker due to the re-drawing process. It may be removed during the process. However, the wrinkles that occur from the cup shoulder to the middle part of the cup at the beginning of the re-drawing process are not as thick as the plate thickness, so the squeezing action of the flange part does not work as well, and the wrinkles remain even after the re-drawing process. What remains is the current situation. The wrinkles that occur from the shoulder of the cup to the middle of the cup do not become smooth even after the next two or three stages of ironing, but rather become uneven, resulting in a poor appearance called "black streaks" on the side wall of the can. It was found that it was occurring. In addition, if the shoulder radius of the bottom of the cup is formed small in the previous process, and there is a gap 5 at the bottom of the cup during re-drawing, that is, the cup is not in close contact with the wrinkle presser, when re-drawing The repeated bending and unbending deformation of the can becomes severe and a strong shock line is generated, which leads to can breakage.

[0008]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the inventors conducted various studies on the shape of molds, and as a result, they came up with the invention of the present invention. That is, the present invention uses a wrinkle presser with a shoulder radius smaller than the bottom shoulder radius of a blank formed into a cup shape in redrawing in deep drawing,
This re-drawing process is characterized in that immediately before drawing in the re-drawing process, the shoulder of the bottom of the cup is formed using the wrinkle presser, and then the re-drawing process is performed using a punch.

That is, in the cup forming step before the re-drawing process, the shoulder radius of the cup bottom is formed to be larger, and the shoulder radius of the wrinkle presser used for the re-drawing process is designed to be smaller than the cup shoulder radius. When performing the re-drawing process, first, the cup is held between the wrinkle presser and the die, and the shoulder at the bottom of the cup is bent back by the wrinkle presser, and the punch is continued to be pushed in while holding the cup to re-draw it. It is used for processing.

0010

[Operation] The present invention will be explained below with reference to the drawings. FIG. 2 is a sectional view showing the re-drawing process according to the method of the present invention. The relationship between the cup 4 and the crease presser 2' according to the present invention is such that the crease presser shoulder radius is smaller than the shoulder radius of the cup bottom, as described above, as shown in FIGS. 2(a) and 2(b). When re-drawing is performed using this wrinkle presser 2', the wrinkle press 2' bends and unbends the bottom of the cup 4 at the time when the wrinkle presser 2' is applied to the cup 4, that is, just before drawing. The shoulder at the bottom is shaped to be in close contact with the shoulder of the wrinkle presser 2'. Therefore, no gap is created between the cup 4 and the crease presser 2'. After that, drawing is continued with the punch 1, so that the drawing process is performed again with sufficient wrinkle pressing force applied, and the occurrence of wrinkles can be prevented. As a result, it is possible to obtain a can with excellent appearance quality without the occurrence of black streaks caused by wrinkles generated on the cup.

[0011] Also, the shoulder radius at the bottom of the cup 4 is pressed by the wrinkle presser 2.
By making the shoulder radius larger than the shoulder radius, repeated bending and unbending deformation during the drawing process can be performed smoothly, and shock lines can be reduced. This reduces the incidence of broken cans, prevents production interruptions, and improves productivity.

0012

[Examples] Examples of the present invention will be described below. The material is commonly used aluminum alloy A3004.
Using a plate of P-H19 material with a thickness of 0.280 mm, processing was performed using a cupping press and a body maker in the usual manner. The re-oil is Nalco 174-L manufactured by Nalco, and the cupping coolant and body maker coolant are Quarol 800 manufactured by Japan Quaka Chemical Co., Ltd.
DI was used for each. The molding speed of the body maker was 280 SPM, and molding tests were conducted with various wrinkle pressing corner radii and cup bottom corner radii as shown in Table 1.

[0013]

[Table 1]

In the molding test, 10,000 cans were continuously molded under various conditions, and appearance quality and can breakage were investigated. Regarding cup wrinkles due to re-drawing, forming was carried out using only a redraw die made by a separate body maker, and the presence or absence of cup wrinkles was examined. The results are shown in Table 1. In the comparative example using the conventional method, cup wrinkles were observed, and black streaks were observed although some were weak. Additionally, some cans ran out. However, in the examples of the present invention, neither cup wrinkles nor dark streaks occur. Also, no occurrence of can breakage was observed.

[0015]

[Effect] As described above, according to the re-drawing method of the present invention, drawing can be performed with sufficient wrinkle pressing force, and as a result, the occurrence of wrinkles can be reduced and the occurrence of black streaks can be prevented. . In addition, bending and unbending deformation is performed smoothly,
The occurrence of shock lines can be reduced, and as a result, breakage of blanks such as broken cans can be prevented, and productivity can be maintained and improved. Although the present invention has been described using a cylindrical deep drawing as an example, it goes without saying that it can also be applied to shapes other than cylinders, such as a rectangular deep drawing. Further, even when re-drawing is performed two or more times, the same effect can be obtained as long as the requirements of the present invention are met.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the configuration of a re-drawing die according to the present invention.

FIG. 2 is a sectional view of a redrawing process showing an embodiment of the present invention.

FIG. 3 is a cross-sectional view showing the deformation process of a material in DI processing.

FIG. 4 is a sectional view showing a mold configuration in a re-drawing process of the prior art.

[Explanation of symbols]

1 Punch 2. Conventional technology wrinkle presser 2’ Wrinkle presser of the present invention 3 Dice 4 Cup 5 Gap

Claims (1)

[Claims] Claim 1: In the re-drawing process in deep drawing, a wrinkle presser with a shoulder radius smaller than the bottom shoulder radius of the blank formed into a cup shape is used, and the wrinkle presser is used to remove the wrinkles immediately before drawing in the re-drawing process. A re-drawing process characterized by forming the shoulder at the bottom of the cup and then performing re-drawing using a punch.