JPS6245429A - Crack preventing method for flange part in burring - Google Patents

Abstract

PURPOSE:To increase the efficiency in burring by removing the rupture face of the prepared hole caused in punching stage with flat punching. CONSTITUTION:A prepared hole 2 is formed by punching on a coil stock 1 in the first stage. The rupture face 2a of the prepared hole 2 is then crushed by performing the flat punching from the lower part by arranging a flat punching punch 5 at the lower part of the coil stock 1 for a die 7 in the second stage. In this case the tip head part 5a of the punch 5 is made in semiglobular shape and the diameter is set in the same diameter with that of the prepared hole 2. Due to the shoulder part 5b with R for striking being abutted completely to the rupture face 2a of the prepared hole 2 the whole rupture face 2a can be crushed completely. Then, due to the burring being performed the work having no crack on the flange part is made possible. With this method the automation of the full stage in the working is enabled and the efficiency in burring is increased.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention provides a method for preventing cracks from occurring in the flange formed by burring when a prepared hole formed by punching is burred. This invention relates to a method for preventing cracking of a flange portion during burring.

[Prior Art] When performing burring on a pilot hole formed by normal punching, as a pretreatment step, the fractured surface that has occurred in the pilot hole in the punching step is removed with a drill or reamer to smooth the cut. process has been adopted.

[Problems to be Solved by the Invention] When a prepared hole is formed in a flat plate by punching as described above, a fractured surface is generated at the cut end outside the sheared surface, except in special cases. Therefore, if burring is performed as is, the burring coefficient will naturally be poor, and defects such as cracks will easily occur in the flange portion to be formed. In other words, burring of a predetermined diameter becomes difficult.

Therefore, as mentioned above, the process of removing the fractured surface using a reamer or drill has been adopted as a pretreatment process, but since these work processes are performed using a drilling machine, This process is completely different from press work processes such as punching and burring of pilot holes that are performed before and after the process, and therefore, the reality is that the entire process cannot be automated using a transfer or progressive system using a press. However, there is a problem in that it is difficult to measure the efficiency of burring.

[Structure for Solving Problems 1it1 The gist of the configuration of the present invention is that in burring processing in which a pilot hole is formed by punching in a flat plate and a rim is attached to the pilot hole, prior to the burring step, This is a method for preventing cracking of the flange part during burring processing, in which the fractured surface generated in the pilot hole during the punching process is removed by face punching.

The surface punching is performed so as to completely crush the fractured surface of the pilot hole. It is appropriate to strike the face material punch from the end of the pilot hole where the fractured surface is occurring, that is, the side where the burr is occurring, to crush the fractured surface.

The guide head at the tip of the face material punch is formed into a hemispherical shape with the same diameter as the pilot hole, the shoulder is rounded for hitting, and the diameter of the lower base is approximately twice that of the pilot hole. do. The radius of the shoulder portion is set appropriately so that the guide head completely contacts the fractured surface of the pilot hole from the bottom to the shoulder, and the entire fractured surface can be flattened. This face punch/chi is made of cemented carbide.

The subsequent burring process is preferably carried out by piercing the prepared hole with a burring punch from the same direction as the surface material punch, from the viewpoint of making the flange portion less likely to crack or break.

In general, it is preferable that the tip of a Hering punch has a conical or spherical shape, but with further innovation, the tip shape is spherical or conical, with a front part that is slightly smaller in diameter than the target diameter. If this is followed by a rear part that expands into a conical shape from the continuous part and reaches the target diameter, the formability will be further improved and the flange part will be less likely to have defects such as cracks. Burring processing may be performed. Furthermore, if a pilot protrusion is provided at the center of the front section, even more accurate centering with respect to the pilot hole can be achieved.

Note that when forming the pilot hole first, it is naturally preferable to minimize the fractured surface as much as possible. For example, the neck of a punch for forming a prepared hole is formed to have a smaller diameter than the cutting edge at the tip to eliminate the possibility of return contact. Also, the clearance between the outer diameter of the cutting edge of the punch and the inner diameter of the die is 0.
．． It is better to make it 1 mm or less.

[Function] Since the present invention is configured as described above, the fractured surface generated in the prepared hole during the punching process is removed by a surface punching operation that can be similarly performed by a press. No breakage or cracks occur in the flange during the burring process.

Furthermore, since the surface punching step is an operation step that can be performed by the same press machine as the preceding and subsequent pilot hole punching and burring steps, the entire process can be performed in a series of transfer or progressive steps.

Therefore, since the entire process can be automated as described above, very highly efficient burring can be performed without causing cracks or breaks in the flange.

[Example] An embodiment of the present invention will be described below based on the drawings.

In this example, a 6.3-mm pilot hole 2 is drilled in a 2,3t coil material 1 using a progressive processing method using a press machine.
This is the step of forming the flange f of 3.2-.

As shown in FIG. 1, a pilot hole 2 is formed in the coil material 1 by punching in the first step, and as shown in FIG. The fractured surface 2a generated in step 2 is faceted, and then, as shown in FIG. 3, the prepared hole 2 is burred in a third step. It goes without saying that each of the above-mentioned steps is carried out in successive stages in which the coil material 1 is fed one stroke at a time.

In the first step, the 6.3-prepared hole 2 is formed as described above. The width of the fractured surface 2a of the pilot hole 2 is made as narrow as possible. The tip cutting edge 3a of the punching bond 3 for forming a prepared hole has a diameter of 6.3 mm, and its neck 3b is formed to have a smaller diameter than the tip cutting edge 3a. The purpose is to eliminate the chance of a return hit. The height of the tip cutting edge portion 3a is 2.64 mm.

This is 1.2 times the thickness of the coil material 1. Also, the clearance with the inner diameter of die 4 is 0. Imm or later.

The second step is carried out so as to completely crush the fractured surface 2d of the pilot hole 2. Try to crush it. This face material punch 5 has a hemispherical guide head 5a at the tip, and its diameter is 6.3#, which is the same diameter as the prepared hole 2. The shoulder portion 5b is rounded for hitting. This will be 7R.

The diameter of the base portion 5c of this face material punch 5 is 12'. The R shoulder part 5b for striking from the lower part of the hemispherical guide head 5a completely contacts the fractured surface 2a of the prepared hole 2 formed in the first step, and the entire fractured surface 2a. can be crushed cleanly.

The third step in section 1 is a burring step.

The burring punch 6 is inserted into the prepared hole 2 in the same direction as the face material punch 5, that is, from the r direction. This burring punch 6 has a front end portion 6a that is hemispherical and has a slightly smaller diameter than the target inner diameter of 20.5', and a conical portion that is enlarged from the continuous portion to have a target inner diameter of 20.5'.
1 and a rear section 6b which is the same as that of 1. Furthermore, a pilot protrusion 6C is attached to the center of the front part 6a to ensure accurate centering with respect to the pilot hole 2.

Note that the punch 3, surface punch 5, and burring punch 6 are all made of cemented carbide.

In the figure, 7 is the die of the face material punch 5, and 8 is the die of the burring punch 6.

Since this embodiment is configured as described above,
While the coil material 1 is being fed sequentially, the first to third steps are executed at each stage.

In the first step, a pilot hole 2 is punched out with a punch 3,
The fractured surface 2 produced in the prepared hole 2 in this step is crushed and removed by the face material punch 5 in the second step. In the subsequent third step, the burring punch 6 is passed through the prepared hole 2 to perform the burring step. However, in the second step above, the pilot hole 2
Since the fractured surface 2a of the flange f is removed by the face material, formability is improved, and reliable burring can be performed without cracking the flange f.

As described above, the fractured surface 2a of the pilot hole 2 is face-faced with the face-material punch 5, and this process is configured in a progressive manner along with the previous and subsequent steps, resulting in a greatly improved gun carriage.

[Effects of the Invention] According to the present invention, since the fractured surface of the pilot hole can be removed by pressing, the process of punching and burring the front and rear pilot holes, as well as the subsequent blanking step F, etc. It is easy to automate the entire process. Therefore, compared to methods that involve extraneous processes such as removing the fractured surface with a reamer or drill, the improvement rate is overwhelmingly higher.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention, and FIG. 1 is a partially cutaway side view showing the punching process, FIG. 2 is a partially cutaway side view showing the facing process, and FIG. The figure is a partially cutaway side view showing the burring process. 1...Coil material? ... Pilot hole, 2a ... Fractured surface,
3... Punch, 3a... Tip cutting edge, 3b...
・Part 6, 4.7.8... Die, 5... Face material punch,
5a... Guide head, 5b... Shoulder part, 5c... Base shaft part, 6... Burring punch, 6a... Front part, 6
b...Rear section, 6C...Protrusion, f...Flange. Patent Applicant Sato Seiki Co., Ltd. Patent Attorney Yukio Kibata Figure 3

Claims (1)

[Claims] In the burring process in which a pilot hole is formed by punching in a flat plate and the pilot hole is edged, prior to the burring process, the fractured surface of the pilot hole generated in the punching process is face-faced. A method for preventing cracks in a flange portion during burring processing, characterized by removing the cracks by.