CN110788209A

CN110788209A - Method for inhibiting flanging hole from cracking

Info

Publication number: CN110788209A
Application number: CN201911101295.0A
Authority: CN
Inventors: 吴勇; 徐志平; 张凯旋
Original assignee: Adient Engineering and IP GmbH
Current assignee: Yanfeng Adient Seating Co Ltd; Adient Engineering and IP GmbH
Priority date: 2019-11-12
Filing date: 2019-11-12
Publication date: 2020-02-14

Abstract

The invention relates to a method for inhibiting the cracking of a flanging hole, which comprises the following steps: clamping a to-be-formed part between an upper die and a lower die, wherein the upper die is provided with an upper punch capable of ascending and descending along a central longitudinal axis, and the lower die is provided with a groove arranged around the central longitudinal axis and a lower punch capable of ascending and descending along the central longitudinal axis; the upper punch selects a press packet punch, free ends of the upper punch and the lower punch opposite to each other are matched in the groove to stretch the piece to be formed into a convex packet, and the convex packet is provided with a thinned bottom wall; the upper punch is replaced by a pre-punching punch, and the upper punch punches towards the bottom wall of the piece to be formed to form stamping; the upper punch is replaced by a flanging punch, which punches out towards the impression of the piece to be formed to form the flanging hole. The method according to the invention presses out the convex hulls by means of a drawing step, stores the material and reduces the material flow tendency, avoids the formation of broken strips, but becomes fillet strips, and the problem of cracking is eliminated or at least substantially avoided by the flanging holes obtained by means of the pre-punching step and the hole drawing step.

Description

Method for inhibiting flanging hole from cracking

Technical Field

The invention relates to a hole drawing process, in particular to a method for inhibiting cracking of a flanging hole.

Background

The seat cushion pad of the automobile seat is formed using a high-strength material (for example, high-strength steel) for strength. In the prior art, the cushion pad is usually fixed by welding a nut.

Obviously, the connection by means of the weld nut requires additional personnel to be arranged after the cushion pan is formed to complete the connection, which necessarily results in a long production cycle and high manufacturing costs.

In order to solve the problem, it has been reported that the welding nut is changed into the tapping hole tapping, so that the tapping can be integrated into the die, the production tact can be reduced from 16s to 4s, and therefore, not only is the additional labor cost saved, but also the stock of semi-finished products is eliminated, and the like, and the method has remarkable advantages.

However, practical results show that high-strength materials (e.g., high-strength steels) tend to have lower plasticity and ductility, e.g., the elongation or elongation EL (%) of high-strength steel CR980T/700Y is only 8%, so that the flanging hole thus achieved has an extremely high cracking rate, resulting in the occurrence of a large number of rejects.

Disclosure of Invention

In order to solve the problem that the high-strength material is easy to crack during hole drawing, the invention provides a method for inhibiting the cracking of a flanging hole.

The method for inhibiting the cracking of the flanging hole comprises the following steps: s1, clamping the piece to be formed between an upper die and a lower die, wherein the upper die is provided with an upper punch capable of ascending and descending along a central longitudinal axis, and the lower die is provided with a groove arranged around the central longitudinal axis and a lower punch capable of ascending and descending along the central longitudinal axis; s2, selecting a bag pressing punch by the upper punch, and matching free ends, opposite to each other, of the upper punch and the lower punch in the groove to stretch the piece to be formed into a convex bag, wherein the convex bag is provided with a thinned bottom wall; s3, replacing the upper punch by a pre-punching punch, and punching the upper punch towards the bottom wall of the piece to be formed to form an impression; s4, the upper punch is replaced with a burring punch, and the upper punch is blanked toward the impression of the piece to be formed to form a burring hole.

Preferably, in step S2, the upper punch presses the to-be-formed part downward toward the groove to form a convex hull in the groove, and the lower punch pushes the to-be-formed part upward toward the groove to form a fillet strip in the groove.

Preferably, in step S2, the area where the material to be formed is pressed into the groove by the upper and lower punches forms a fillet.

Preferably, in step S2, the convex hull further comprises an extension wall connected to the body, wherein the extension wall is disposed between and connects the body and the bottom wall, and the fillet is an end of the extension wall adjacent to the bottom wall.

Preferably, the body has a first thickness, the bottom wall has a second thickness, and the thickness of the extension wall gradually decreases from the first thickness to the second thickness after increasing in the fillet zone.

Preferably, the first thickness is 1-2mm and the second thickness is 0.5-0.8 mm.

Preferably, the diameter of the pre-pierce punch is smaller than the diameter of the press-wrap punch and smaller than the diameter of the bottom wall.

Preferably, the diameter of the flanging punch is smaller than that of the press wrapping punch and larger than that of the bottom wall.

Preferably, the rounded free end of the flanging punch transitions more gradually than the rounded free end of the press-wrapping punch.

Preferably, the height of the flanging hole is 3-4 mm.

The method according to the invention first presses out the convex hulls by means of a drawing step, stores the material and reduces the material flow tendency, avoids the formation of broken strips, but becomes fillet strips, and then eliminates or at least substantially avoids the problem of cracking by means of the flanging holes obtained by means of a pre-punching step and a hole drawing step.

Drawings

FIG. 1 illustrates a drawing step of a method of suppressing burring hole cracking according to the present invention;

FIG. 2 is an enlarged view of a portion of the part to be formed resulting from the drawing step of FIG. 1;

FIG. 3 illustrates a pre-punching step of a method of inhibiting burring hole cracking according to the present invention;

fig. 4 illustrates a hole drawing step of the method of suppressing the cracking of the burring hole according to the present invention.

Detailed Description

The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

As shown in fig. 1, the method of suppressing the burring hole from being cracked according to the present invention first includes a drawing step. In this step, the member to be formed 1 is sandwiched and arranged between an upper die 2 and a lower die 3, the upper die 2 having an upper punch 21 which is liftable along a central longitudinal axis L, the lower die 3 having a recess 31 provided around the central longitudinal axis L and a lower punch 32 which is liftable along the central longitudinal axis L, free ends of the upper punch 31 and the lower punch 32 which are opposed to each other being fitted in the recess 31 to press the member to be formed 1. Specifically, the upper punch 21 is a press-wrapping punch 21a, which may also be referred to as a round-head punch, which presses the to-be-formed part 1 downward toward the recess 31 so that it forms a convex wrap in the recess 31, and correspondingly, the lower punch 31 pushes the to-be-formed part 1 upward toward the recess 31 so that it forms a fillet 1a in the recess 31 as shown in fig. 2. Wherein the fillet band 1a is formed as a result of the material of the member to be formed 1 in the drawing step being pressed into the a region (see fig. 1) in the recess 31 by the upper and

lower punches

31, 32.

As shown in fig. 2, the member to be molded 1 after the drawing step includes a body 11 and a convex hull including an extension wall 12 and a bottom wall 13, wherein the extension wall 12 is disposed between the body 11 and the bottom wall 13 and connects the body 11 and the bottom wall 13, and the fillet 1a is an end of the extension wall 12 adjacent to the bottom wall 13. The body 11 has a first thickness (i.e. the original thickness of the piece 1 to be formed before the drawing step), the bottom wall 13 has a second reduced thickness, and the thickness of the extension wall 12 gradually decreases from the first thickness to a second thickness which increases slightly and then gradually decreases in the region of the fillet 1 a. In this embodiment, the first thickness is 1.5mm and the second thickness is 0.5 mm. It is clear that a slight increase in the thickness in the region of the fillet strip 1a is associated with the pressing of the upper and

lower punches

31, 32 against the part to be formed 1.

As shown in fig. 3, the method of suppressing the cracking of the burring hole according to the present invention next includes a pre-punching step. In this step, the upper punch 21 punches toward the bottom wall 13 of the member to be molded 1 to form an impression. Wherein the upper punch 21 is replaced by a pre-punch 21b, also called flat-head punch, having a diameter smaller than the diameter of the press-wrapping punch 21a in the drawing step and slightly smaller than the diameter of the bottom wall 13, for example 0.1mm smaller than the bottom wall 13.

As shown in fig. 4, the method of suppressing the burring hole from being cracked according to the present invention next includes a hole drawing step. In this step, the upper punch 21 punches out toward the impression of the to-be-molded article 1 to form a burring hole. In this case, the upper punch 21 is replaced with a burring punch 21c, which may also be referred to as an elliptical-head punch, which is slightly smaller than the diameter of the press-wrapping punch 21a in the drawing step, larger than the diameter of the pre-punching punch 21b and larger than the diameter of the bottom wall 13. The rounded free end of the burring punch 21c transitions more gradually than the rounded free end of the clinch punch 21 a. In this embodiment, the height of the burring holes is 3.5 mm.

In the initial development of finding that the flanging hole is easy to crack, a conical upper punch is used to replace a round upper punch, the flanging hole directly obtained by punching still has high cracking rate, the cracking positions of the flanging hole are all at the positions of fracture zones, and the fracture zones are common terms in the punching industry and mean that in the blanking process, the material at the end opposite to the punch is torn, and large burrs are generated. After a considerable inventive effort, the method according to the invention first presses out the convex hulls by means of a drawing step, stores the material and reduces the material flow tendency, avoids the formation of broken bands, but becomes fillet bands, and then eliminates or at least substantially avoids the problem of cracking by means of the flanging holes obtained by means of a pre-punching step and a hole drawing step.

The above embodiments are merely preferred embodiments of the present invention, which are not intended to limit the scope of the present invention, and various changes may be made in the above embodiments of the present invention. All simple and equivalent changes and modifications made according to the claims and the content of the specification of the present application fall within the scope of the claims of the present patent application. The invention has not been described in detail in order to avoid obscuring the invention.

Claims

1. A method of inhibiting the cracking of a burring hole, the method comprising the steps of:

s1, clamping the piece to be formed between an upper die and a lower die, wherein the upper die is provided with an upper punch capable of ascending and descending along a central longitudinal axis, and the lower die is provided with a groove arranged around the central longitudinal axis and a lower punch capable of ascending and descending along the central longitudinal axis;

s2, selecting a bag pressing punch by the upper punch, and matching free ends, opposite to each other, of the upper punch and the lower punch in the groove to stretch the piece to be formed into a convex bag, wherein the convex bag is provided with a thinned bottom wall;

s3, replacing the upper punch by a pre-punching punch, and punching the upper punch towards the bottom wall of the piece to be formed to form an impression;

s4, the upper punch is replaced with a burring punch, and the upper punch is blanked toward the impression of the piece to be formed to form a burring hole.

2. The method of claim 1, wherein in step S2, the upper punch presses the to-be-formed part downward toward the groove to form a convex hull in the groove, and the lower punch pushes the to-be-formed part upward toward the groove to form a fillet in the groove.

3. The method of claim 2, wherein in step S2, the area where the material to be formed is pressed into the groove by the upper and lower punches forms a fillet.

4. The method of claim 2, wherein in step S2, the convex hull further comprises an extension wall connected to the body, wherein the extension wall is disposed between and connects the body and the bottom wall, and the fillet is an end of the extension wall adjacent to the bottom wall.

5. The method of claim 4, wherein the body has a first thickness, the bottom wall has a second thickness, and the thickness of the extending wall gradually decreases from the first thickness to the second thickness after increasing in the fillet zone.

6. The method of claim 5, wherein the first thickness is 1-2mm and the second thickness is 0.5-0.8 mm.

7. The method of claim 1, wherein the pre-punch has a diameter less than the diameter of the press pack punch and less than the diameter of the bottom wall.

8. The method of claim 1, wherein the diameter of the hole flanging punch is smaller than the diameter of the bale press punch and larger than the diameter of the bottom wall.

9. The method of claim 1, wherein the radiused free end of the pierce punch transitions more gradually than the radiused free end of the pack punch.

10. The method of claim 1, wherein the height of the burring holes is 3 to 4 mm.