JPH0446647B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a pipe shrinking method for forming a relatively long narrow tube with a large diameter difference compared to the diameter of the raw tube using a spinning machine.

Prior Art and Problems Figure 1a shows a blank tube, and Figure 1b shows a product 2 formed from the blank tube 1.The product 2 has a large diameter portion 3 having the same diameter as the blank tube 1, and It consists of a long blank tube 4 with a small diameter d that is larger in diameter than the diameter D of the portion 3. The blank tube 4 is normally formed by multiple cycles of drawing using one drawing roll 5, as shown in FIG. However, in this case, although the core metal 6 is used, the drawing process in the middle is a so-called dry drawing process. Therefore, when the tube is contracted, the free end of the rough section 7 is deflected due to uneven thickness, variation in elongation rate, unevenness, etc. as shown in FIG. 2, and this grows with each cycle and sometimes the tube The end is struck against the metal core, and a portion from the opening end is deformed into a polygonal shape, often resulting in a crack 8 at the free end of the rough section 7, as shown in FIG. When continuing the drawing process, crack 8
As the cracks grow, it is necessary to cut out the crack 8 part during processing, which is very time-consuming and may sometimes break off at the stepped part 9, and the longer the length of the thin tube 4, the greater the tendency for this to occur. It is.

According to the experimental results, the material of the raw pipe 1 is aluminum, and the outer diameter (same diameter as the large diameter part 3 of the product 2)
48mm, raw tube wall thickness 2.0mm, outer diameter d of thin tube 4 = 12mm,
In the case of a wall thickness of 1.75 mm, the limit for the length of the thin tube 4 is 60 to 70 mm, and there are drawbacks such as unevenness in the wall thickness of the thin tube 4 due to the tube shrinking process, and a length of 12 mm cannot be processed. The wall thickness of the thin tube 4 is determined by pressing the squeeze roll 5 against the core metal 6 and ironing it.
If the narrow diameter portion 6a of the core metal 6 is thin and long, the core metal will be bent, making it impossible to perform the process effectively, and there is also a risk of breakage at the stepped portion.

For this reason, a method has been proposed in which a plurality of, for example, three, drawing rolls are arranged symmetrically around the rotation axis to perform drawing. When using this method, the squeezing is done simultaneously by three squeezing rolls, so
When ironing along the core metal 6, there is no risk of bending the core metal, but when dry drawing, the above 1.
As in the case of individual squeeze rolls, occurrence of cracks and breakage at the stepped portion 8 due to deflection of the free end cannot be avoided.

For this reason, a method has been proposed in which the free end of the raw pipe 1 is held by a restraining roller or the like to prevent the above-mentioned deflection, but this method is structurally complex, takes time to install, and the restrained part requires pipe shrinking. Since it cannot be used, the movement of the raw pipe is poor, and it is only used in special cases.
Not commonly used.

Means for Solving the Problems The present invention has been made in view of the above points, and provides a tube shrinking method that does not cause runout during tube shrinking and can easily process thin tubes with large diameter differences. With the purpose of is equipped with a drawing roll located on the support side of the raw pipe along the axial direction parallel to the processing axis, and a guide roll located behind the drawing roll, and through multi-cycle dry drawing processing, the raw pipe is held by the guide roll and drawn. It is characterized by drawing it into a rough shape using rolls, and then ironing it along the core metal using drawing rolls.

Embodiment FIG. 4 is a front view of a processing roll used in the processing method of the present invention. This processing roll 10 has a plurality of ridges 1 (two in the example) spaced apart in the axial direction.
1 and 12, one ridge 11 is used as a squeezing roll, and the other ridge 12 is used as a guide roll,
Does the guide roll 12 have the same diameter as the squeeze roll 11?
Alternatively, it is formed to have a slightly smaller diameter. Although the above embodiment has been described as an integral type, it goes without saying that the rolls 11 and 12 may be fixed individually in the axial direction with a predetermined interval between them.

The fifth method for shrinking the tube using the processing roll 10 is as follows.
A description will be given of FIGS. 7 to 7.

One end of the raw tube 1 is fitted onto the core bar 6 and fixed to a chuck 13 that is attached to the main shaft (not shown) of the spinning machine together with the core bar 6, and the tip of the narrow diameter portion 6a of the core bar 6 is connected to the tailstock. (not shown)
The other end 1a of the blank tube 1 is freely open.

As shown in FIG. 6, a plurality of processing rolls 10 (three in the illustrated example) are arranged symmetrically around the rotation axis. First, as shown in machining cycle A in FIG. 5, each machining roll 10 synchronously reciprocates in the Y-axis direction and bites in the X-axis direction, and performs dry drawing with the squeeze roll 11 to form a rough shape. A section 15 is formed. At this time, runout occurs during tube shrinking by the squeeze roll 11, but since it is immediately restrained or supported by the rear guide roll 12, the runout is corrected and processing can be performed under the best conditions without causing runout as shown in Figure 2. You can make progress. In this case, due to the nature of the pipe shrinking process, the coarsely formed part 15 is slightly thicker than the raw pipe 1.

By continuing the above-mentioned dry drawing, the inner diameter of the coarse portion 15 comes into contact with the narrow diameter portion 6a of the core bar 6. After contacting each other, as shown in FIG. 7, each processing roll 10 performs ironing processing by reciprocating in the Y-axis direction and biting in the X-axis direction as shown in processing cycle B as described above, thereby forming a rough part. 15 is finished into a thin tube 4 having a predetermined wall thickness to form the product 2 shown in FIG. 1b.

According to the experimental results, when using the method of the present invention, the outer diameter of the raw pipe (the outer diameter of product 2 is also the same) D =
In the case of an aluminum tube with a diameter of 48 mm and a wall thickness of 2.0 mm, the diameter d of the thin tube 4 is 12 mm, the wall thickness is 1.75 mm, and its length is
It is possible to make it 400mm or more, and the thin tube 4
It was also possible to make the wall thickness approximately uniform.

Effects of the Invention According to the present invention, a plurality of processing rolls are arranged symmetrically with respect to the processing axis, and the processing rolls are formed from a plurality of rolls along the axial direction, so that the free end side of the raw tube swings. Therefore, the free end will not be deformed or cracked, and a long thin tube with a predetermined wall thickness can be easily formed. In addition, one of the plurality of rolls mentioned above is a squeeze roll, and even if any deflection or deflection occurs due to the tube shrinking process, it is immediately restrained or corrected by the rear guide roll, so there is no occurrence of deflection, deflection, etc. We were able to perform the tube shrinking process efficiently and accurately.

[Brief explanation of the drawing]

Figure 1a is the raw pipe, Figure b is a longitudinal cross-sectional view of the product, Figure 2 is an explanatory diagram of the conventional drawing process, Figure 3
The figure is an explanatory diagram showing cracks generated by conventional drawing processing, Figures 4 to 7 relate to the processing method of the present invention, Figure 4 is a front view of the processing roll, and Figure 5 shows the processing procedure for the rough section. The explanatory drawings, FIG. 6, are a sectional view taken along the - line in FIG. 5, and FIG. 7 is an explanatory view of the ironing procedure. 1 is a raw tube, 4 is a thin tube, 6 is a core metal, 10 is a processing roll, 11 is a drawing roll, 12 is a guide roll, 1
5 is a rough portion.

Claims (1)

[Claims] 1. In a pipe shrinking method in which one end of the raw pipe is supported together with a rotating core metal and the bottom side is shrunk into a thin tube with a larger diameter difference than the base pipe, the raw pipe is inserted onto the core metal,
One end is supported and the other end is a free end, a plurality of processing rolls are arranged symmetrically around the processing axis, and each processing roll is supported along the axis direction parallel to the processing axis. It is equipped with a drawing roll located on the side and a guide roll located behind it, and through multi-cycle dry drawing processing, the raw tube is gripped by the guide roll, squeezed into a rough shape by the drawing roll, and then drawn along the core metal. A pipe shrinking method characterized by ironing with rolls.