JPS58171210A - Shearing method of circular pipe - Google Patents

Abstract

PURPOSE:To shear a long circular pipe efficiently by a method wherein split molds are brought into contact on both sides of the circular pipe to compress the circular pipe into an elliptic shape and a punch is brought into contact with the pipe from the long diameter direction. CONSTITUTION:After the circular pipe 1 is located between a pair of molds 2 having elliptic hole, a hydraulic or pneumatic piston 11 is advanced, the circular pipe is deformed into an elliptic shape to produce compressive force. Upper plate 8 is dropped to shear the circular pipe 1 with the punch 3. A pair of metallic molds 2 provides a suitable clearance or a hole of relief so that they do not collide with the punch 3. When the mold 2 is opened after shearing operation, the circular pipe 1 is corrected by a pair of rolls 4 into a circular shape and discharged.

Description

[Detailed Description of the Invention] Cutting and drilling of circular pipes by shear processing has a faster processing speed than cutting, grinding, fusing, and other processing methods, so it not only has high productivity and can reduce costs. ,
It has the advantage of good shear surface accuracy, little burr, and no contamination of the inside of the pipe with chips, so it has a fairly wide range of potential applications, but since the technology has not yet been established, there are no practical examples. Few. What is important in shearing circular pipes is that
It is important not to cause collapse. In order to prevent the tube from collapsing inside, there is a method of inserting a mandrel inside the tube and shearing it. This method has little value as it becomes difficult to position the circular tube and mandrel when the circular tube becomes long, and it takes time and effort to take in and take out the circular tube. The shearing method for circular pipes using mandrels is limited by the length of the pipe, and its range of use is limited.

Another processing method that prevents the pipe from collapsing inside and performs shear processing without using a mandrel is the double parting method. In this processing method, a slit is made in the horizontal direction with a cutting knife in the horizontal direction, and in the second step, a thin movable cutting knife with a pointed tip is thrust into the slit, and is the most widely used method. In this processing method, since the first step of slitting is cutting, the bit-shaped cutting blade wears quickly, reducing the machine operating rate due to tool replacement, and there are restrictions on the cutting thickness. It is possible only for internal pipes, and is not suitable for thick-walled pipes. Furthermore, since it requires two steps, a special machine is required. In terms of accuracy, some burrs and crushing occur during slitting and breaking through the bottom. Other processing methods for shearing without using a mandrel include the biaxial shearing method, the inverted V-shaped parting method, and the breakthrough method, but there are limitations on the precision of the sheared surface, crushing of the circular tube, wall thickness, etc. There are problems with either the need for a dedicated machine, etc., and there are very few examples of this being implemented.

In order to solve the drawbacks of the above-mentioned processing method, the present invention uses the same equation x2/a2+y when distorting a circular tube to make it circular.
2/b2=1 [However, the relationship between the major axis 2a and the minor axis 2b is
A half-split mold with a curvature of [a > b] was brought into contact with the circular tube from both sides, and pressure was applied to deform the circular tube into a circular shape, applying compressive stress in the circumferential direction of the circular tube. In this state, a punch is brought into contact with the deformed tube from the direction of its major diameter to perform shearing.

One way to suppress the collapse of a circular tube is to increase the quadratic cross-sectional area. In order to increase the cross-sectional dimension of a circular tube without changing its wall thickness, it is necessary to warp the circular tube to make it circular. When a circular pipe is deformed into a circular shape, its moment of inertia is I=x(r4-(
From r-t)4)/4, Ia=x(a3b-(a-t)
3(b-t))/4 [where t represents the wall thickness of the tube]. Since the circumferential length of the circular tube is constant, b decreases by increasing a of the circle, but Ia still increases to a value close to a2. Therefore, if a of the circular shape is sufficiently larger than b, collapse of the circular pipe due to shear load can be prevented by increasing the moment of inertia of area. Moreover, this circular mold is effective for thin-walled circular pipes that are easily crushed. As the wall thickness of the circular pipe decreases, as is clear from the above formula I, the moment of inertia of area decreases, and the collapse upon shearing increases. However, when the wall thickness decreases, even if it is distorted into a circular shape and the ratio of the major axis to the minor axis is increased,
Plastic deformation of the pipe is unlikely to occur. Therefore, thin-walled circular tubes can be sheared without crushing by increasing the ratio of the major axis to minor axis, and thick-walled circular tubes have a large moment of inertia of the tube themselves, so Shearing without crushing can be performed without increasing the short axis ratio. That is,
By using a circular mold with a curve appropriate for the wall thickness and material, shearing without crushing is possible without being restricted by the material or wall thickness of the tube.

Further, since the circular tube is deformed into a circular shape and is in close contact with the surrounding mold, the tube cannot be freely deformed in the outward direction. This also has the effect of suppressing the pipe from being distorted due to shear load, causing a portion of the pipe to bulge outward in a circular shape and reducing the moment of inertia of the pipe, thereby preventing collapse.

Furthermore, when compressive stress is applied in the circumferential direction of a circularly warped tube within the elastic region, a reaction force acts on the circular tube, causing it to expand outward. This reaction force has the effect of preventing the tube from deforming inward at the contact portion of the punch when shearing the tube with the punch.

As mentioned above, by warping a circular pipe into a circular shape using a mold and applying compressive stress in the circumferential direction, several effects appear to suppress collapse, and the shearing without collapse is achieved. The first invention is a processing method characterized in that processing can be performed.

In addition, after the shearing process is completed, if the circular tube that has been distorted into a circular shape by the mold reaches the plastic region and the circular shape remains, it is necessary to The second invention is to correct the deformation by installing a roll and passing the pipe through it.

Next, specific examples of the present invention will be explained with reference to the drawings.

In the present invention, a guide post 9 and a holding plate 1 are provided in the lower part 7.
4 and the mounting plate 13, and attach the cylinder 1 to the mounting plate 13.
Install 2. Further, a support 6 holding the shafts 5 of the pair of rolls 4 is fixed on the passage of the tube of the lower die 7. The support stand 10 with the punch 3 attached is fixed to the upper mold 8, and the upper mold 8 is inserted into the guide post 9. One side of the mold 2 that holds the circular tube 1 is attached to the holding plate 14, and the other side is attached to the piston 11 of the cylinder 12.

Next, to explain the above method of use, after positioning the circular tube 1, move the piston 11 forward using hydraulic or pneumatic pressure, deform the circular tube 1 into a circular shape, and generate compressive stress. The mold 8 is lowered by a press, and the circular tube 1 is sheared by the punch 3. The pair of molds is provided with an escape hole having an appropriate clearance in a portion through which the punch 3 passes so as not to collide with the punch 3. When the shearing process is completed, the upper die 8 rises,
The piston 11 retreats and the mold 2 separates. Thereafter, the circular tube 1 is passed through the rolls 4 and taken out. Then, the circular tube 1 for main processing is put into the mold 2 again, positioned, and the next operation is performed. Note that the mechanism for pressing the mold 2 for deforming the circular tube 1 into a round shape according to the present invention uses a hydraulic or pneumatic piston 11, but there are also mechanical or pneumatic pistons such as the distance piece method. Since it is also possible to press electromagnetically, the method of pressing is not limited.

The present invention can be used not only for cutting circular pipes but also for drilling holes. Furthermore, it is possible to machine holes in shapes other than round holes, such as square holes, which are difficult to machine by cutting.

As mentioned above, the present invention makes it possible to shear long circular tubes, which were conventionally considered difficult to process, without being subject to wall thickness restrictions, without crushing them, in a single process using an ordinary press. It is now possible to perform hole drilling operations that are not limited by conditions, which is revolutionary as it greatly contributes to improving quality, productivity, and reducing product costs.

[Brief explanation of the drawing]

FIG. 1 is a front view of a circular tube shearing device. FIG. 2 is a front view of the roll. FIG. 3 is a side view of the circular tube shearing device. 1... Circular tube 2... Mold 3... Punch 4... Roll 7... Lower mold 8... Upper ■

Claims (2)

[Claims] 1. The same equation as when circular tube 1 is distorted into a circular shape x
A half-split mold 2 having a curvature of 2/a2+y2/b2=1 [the relationship between the major axis 2a and the minor axis 2b is a>b] is brought into contact with the circular tube 1 from both sides, and further pressure is applied to form a circle. A processing method characterized by deforming a pipe 1 into a circular shape, applying compressive stress in the circumferential direction of the circular pipe 1, and then bringing a punch 3 into contact with the deformed pipe from the long diameter direction to shear it. 2. An auxiliary device for shearing a circular tube, characterized in that a roll 4 is installed on the path of the circular tube 1 behind the two circular molds described above, and the tube is passed through to correct the collapse.