CN107908809B - Optimization design method for cooperation of three-axis free bending die and guide mechanism - Google Patents
Optimization design method for cooperation of three-axis free bending die and guide mechanism Download PDFInfo
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- CN107908809B CN107908809B CN201710878955.0A CN201710878955A CN107908809B CN 107908809 B CN107908809 B CN 107908809B CN 201710878955 A CN201710878955 A CN 201710878955A CN 107908809 B CN107908809 B CN 107908809B
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F30/00—Computer-aided design [CAD]
- G06F30/10—Geometric CAD
- G06F30/17—Mechanical parametric or variational design
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D37/00—Tools as parts of machines covered by this subclass
- B21D37/10—Die sets; Pillar guides
- B21D37/12—Particular guiding equipment, e.g. pliers; Special arrangements for interconnection or cooperation of dies
Abstract
The invention discloses a three-axis free bending die and guide mechanism matching optimization design method, and belongs to the technical field of metal plastic forming. The optimal design method is to change the matching form (independent and linear) of the existing three-axis bending die and the guide mechanism into a spherical contact type. Compared with the traditional form, the movement of the bending die in the pipe forming process is more stable in the matching form, the rotation angle theta can be accurately controlled, and the minimum relative bending radius (R/D) of the three-axis free bending equipment can be ensured0) Down to 2.5.
Description
Technical Field
The invention relates to the field of design and assembly of a metal plastic forming device die, in particular to an optimal design method for cooperation of a three-axis free bending die and a guide mechanism.
Background
The three-dimensional free bending system can realize high-precision die-free forming of pipes, profiles and wires under the conditions of various bending radii without replacing a die. The existing three-dimensional free bending equipment can be divided into three-axis, five-axis and six-axis free bending systems according to the motion freedom degree of a bending die. Compared with five-axis and six-axis equipment, the bending die in the three-axis free bending equipment can only actively realize X, Y translational freedom degrees in two directions, and the deflection motion of the three-axis free bending equipment is a passive motion mode and generally needs to be realized by depending on the combined action of the bending die, a spherical bearing and a guide mechanism in matching connection. These two special forms of connection in the three-axis configuration make the die assembly more complex, resulting in geometric limitations on the displacement distance and deflection angle of the bending die during its movement. Due to these geometrical constraints, the relative minimum bend radius of currently available commercial three-axis free-form bending devices is typically only 3.
At present, the matching form of a bending die and a guide mechanism in domestic three-axis free bending equipment is independent and linear. Free standing refers to a three axis free bending configuration with the bending die and guide mechanism completely disengaged. In this form, the rotation of the bending die becomes more uncontrollable, the distance between the spherical bearing and the guide mechanism is often made small in order to control the angle of rotation of the bending die not to be too large, the maximum angle of rotation of the bending die is limited by the contact collision of the bending die with the guide mechanism, but this causes increased wear of the die and reduced service life. Meanwhile, the corner theta of the bending die and the eccentricity of the bending die have no specific geometric relationship and are greatly influenced by the feeding of the pipe, so that the corner theta of the bending die possibly exceeds the maximum stroke angle of the bending die in the motion process, even the bending die is reversely deflected after reaching the preset eccentricity, and the instability of the motion of the bending die is increased. The straight line type is a three-axis free bending configuration in which a generatrix of the bending die and the guide mechanism is tangent to a circle in a half section. In this form, only half of the tail of the bending die is in contact with the guide means and the other half is completely disengaged from the guide means during the upward travel of the bending die. This also results in that at the beginning of the descending process of the bending die, the half of the tail part of the bending die which is not in contact with the guide mechanism directly collides with the guide mechanism, which affects the stability of the movement and damages the die.
Disclosure of Invention
The invention provides a method for optimally designing the cooperation of a three-axis free bending die and a guide mechanism, aiming at solving the problems in the prior art. The optimal design method is to change the matching form (independent and linear) of the existing three-axis bending die and the guide mechanism into a spherical contact type. Compared with the traditional form, the matched form bends in the pipe forming processThe motion of the die is more stable, the deflection angle theta can be accurately controlled, and the minimum relative bending radius (R/D) of the three-axis free bending device can be ensured0) Down to 2.5.
The key point of the optimization design method is to calculate the size of the inner curved surface of the bending die ball contacted with the spherical surface of the guide mechanism, and the specific method comprises the following steps: when the bending die spherical radius R0, the guide mechanism spherical radius R1 and the distance B between the spherical centers of the two are constant, the bending die center O and the upper guide mechanism vertex M are connected, the perpendicular bisector of OM is made to intersect the center line O 'M of the guide mechanism at a point N, and MN is the spherical radius R2 of the bending die spherical inner curved surface which is in contact with the guide mechanism spherical surface (R2 ═ MN ═ ML × OM/O' M ═ OM2/2O’M＝(B2+R12) and/2R 1), wherein TM is the projection line of the inner curved surface of the tail part of the bending die in the half section.
According to the optimization design method for the matching of the three-axis free bending die and the guide mechanism, the envelope curved surface of the tail part of the bending die matched with the guide mechanism is always tangent to the outer spherical surface of the guide mechanism, and the tangent line is closed, so that the stable motion of the bending die is realized.
The sphere center of the envelope surface is collinear with the sphere center of the guide mechanism at the initial position, and the sphere radius R2 of the envelope surface is related to the sphere radius R1 of the guide mechanism and the distance B from the sphere center of the bending die to the sphere center of the guide mechanism, namely R2 ═ B (B)2+R12)/2R1。
The real-time deflection angle theta of the bending die is related to the distance B from the spherical center of the bending die to the spherical center of the guide mechanism and the eccentricity U of the bending die, namely
The real-time bending angle phi of the pipe is related to the distance A from the spherical center of the bending die to the front end of the guide mechanism and the eccentricity U of the bending die, namely
The maximum stroke of the bending die is 0.7 times of the outer diameter of the pipe, and the size of the bending die is closely related to the geometric dimensions and the geometric positions of the bending die and the guide mechanism.
The horizontal length ry of the tail extension line of the bending die in contact with the spherical surface of the guide mechanism is determined by the maximum stroke Umax of the bending die, namely
Under the matching form of the contact between the bending die and the spherical surface of the guide mechanism, the maximum stroke of the bending die has 4 basic limit conditions according to the geometrical relationship, one bending die does not depart from the front end of the guide mechanism, the two bending dies do not collide with the rear end of the guide mechanism, the three pipes are pushed out of the inner hole of the bending die and then do not contact and collide with the inner wall of the bending die and the spherical bearing, and the rotation angles of the four bending dies are smaller than the designed maximum stroke angle (the left end of the bending die does not cross the central line of the spherical bearing).
The invention has the beneficial effects that:
1. under the matching mode that the bending die is in contact with the spherical surface of the guide mechanism, compared with other matching modes, the bending angle phi of the pipe and the deviation value gamma of the bending angle phi and the rotation angle theta of the bending die are smaller
Thereby reducing the cross section distortion and deflection in the pipe forming process, increasing the motion stability of a key mechanism of the equipment, and improving the forming precision and forming limit of the pipe fitting.
2. Intersecting with other matching modes, the method can reduce the distance A from the spherical center of the bending die to the front end of the guide mechanism and increase the eccentricity Umax of the bending die, thereby reducing the minimum bending radius which can be achieved by equipment
3. The method can reduce the minimum relative bending radius (R/D0) of the three-axis free bending device to 2.5.
4. The three-dimensional free bending device for the pipe fully exerts the advantages of being capable of realizing bending and one-time flexible forming of the metal member with the complex shape.
5. The method is simple and feasible, has high production efficiency, and has important engineering application value and obvious economic benefit in the engineering fields of aerospace, nuclear power, automobiles and the like.
Drawings
Fig. 1 shows a schematic view (half section) of a spherical contact design of a bending die and a guide mechanism.
Fig. 2 is a schematic diagram of a three-dimensional free bending device for pipes.
Fig. 3 is a schematic diagram showing a free-standing type of the combination of the bending die and the guide mechanism.
Fig. 4 is a schematic view showing the matching form of the bending die and the guide mechanism in a linear form.
Fig. 5 is a schematic diagram of the motion of the connection of the bending die and the spherical surface of the guide mechanism.
Fig. 6 is a schematic diagram illustrating calculation of the maximum stroke of the bending die.
Fig. 7 is a schematic diagram of the basic dimensions of the bending die and the guide sleeve.
In the figure, 1-bending die, 2-guiding mechanism, 3-spherical envelope curve surface of the tail part of the bending die matched with the guiding mechanism, 4-spherical bearing and 5-tube blank.
Detailed Description
The invention will be further explained with reference to the drawings.
As shown in fig. 1, the spherical contact type means that the bending die and the guide mechanism are in a half-section in which a circle is tangent to the circle (inscribed).
Fig. 2 is a schematic view of a three-dimensional free bending device for a pipe, fig. 3 is a schematic view of a bending die and a guide mechanism in a free-standing manner, and fig. 4 is a schematic view of a bending die and a guide mechanism in a linear manner. In the figure, 1-bending die, 2-guiding mechanism, 3-spherical envelope curve surface of the tail part of the bending die matched with the guiding mechanism, 4-spherical bearing and 5-tube blank. The envelope surface 3 of the tail part of the bending die 1 matched with the guide mechanism 2 is always tangent to the outer spherical surface of the guide mechanism, and the tangent line is closed, so that the stable motion of the bending die is realized.
The key of the optimization design method is to calculate the curved mold ball contacted with the spherical surface of the guide mechanismThe method for measuring the inner curved surface comprises the following specific steps: when the bending die spherical radius R0, the guide mechanism spherical radius R1 and the distance B between the spherical centers of the two are constant, the bending die center O and the upper guide mechanism vertex M are connected, the perpendicular bisector of OM is made to intersect the center line O 'M of the guide mechanism at a point N, and MN is the spherical radius R2 of the bending die spherical inner curved surface which is in contact with the guide mechanism spherical surface (R2 ═ MN ═ ML × OM/O' M ═ OM2/2O’M＝(B2+R12) and/2R 1), wherein TM is the projection line of the inner curved surface of the tail part of the bending die in the half section.
As shown in fig. 5, in the form of spherical contact, the real-time rotation angle of the bending die is related to the eccentricity of the bending die, and can be calculated by the following formula:
fig. 6 is a schematic diagram showing calculation of horizontal distance between the upper and lower tangent points of the bending die and the center of the guide sleeve after translation and rotation. The horizontal distances rp, ab of the upper and lower tangent points b, r are calculated as follows:
The basic dimensions of the bending die and the guide sleeve are shown in fig. 7, and under the form of spherical contact, the basic limitation condition of the theoretical maximum stroke of the bending die is as follows: (1) the lower cutting point of the bending die does not fall off the front end of the guide sleeve, namely vr is equal to B-rp is equal to B-R1sin ro' p is equal to or more than A; (2) the upper cutting point of the bending die does not drop out of the rear end of the guide sleeve, namely ab & ltR 1sin & gt ao' b & lt C & gt;(3) after being pushed out of the inner hole of the bending die, the pipe does not contact and collide with the inner wall of the bending die, namely gamma phi-theta is less than alpha; (4) after the bending die rotates, the upper left point cannot cross the end point of the contact between the starting position and the spherical bearing, namely theta (arctan) (U/B)<Pi/2-alpha. Under the matching form of spherical contact of the bending die and the guide mechanism, the maximum stroke of the bending die is about 0.7 times of the outer diameter of the pipe through theoretical calculation of the formula. Then the minimum relative bending radius (R/D) of the three-axis free bending equipment can be ensured by reasonably designing the size of the mould0) Down to 2.5.
The present invention is described in detail below with reference to specific examples of embodiments applicable to 3 target minimum bend radii (forming limit values).
Example 1
The outer diameter of the tube blank is D, the target minimum bending radius is 2.5D, and the limit eccentricity of a bending die is 0.7D. In order to determine the overall dimensions of the mold, some dimensions that can be derived from the basic molding requirement parameters described above are calculated in advance, and for some dimensions that cannot be directly derived, the dimensions are determined from empirical values. The order of die sizing is therefore: (1) determining the value of the distance A between the center of the bending die and the front end of the guide mechanism:
(2) some dimensions that cannot be directly derived are determined from empirical values: B-2D, R0-1.8D, R1-1.2D, C-0.8D, α -60 °; (3) determining the spherical radius of a spherical envelope surface matched with the bending die and the guide mechanism: r2 ═ B2+R12) 2R1 ═ 2.27D; (4) determining the length of the spherical envelope surface at the tail part of the bending die:
(5) 4 basic constraints for the theoretical maximum travel of the bending die were examined:
example 2
The outer diameter of the tube blank is D, the target minimum bending radius is 3.0D, and the limit eccentricity of a bending die is 0.7D. In order to determine the overall dimensions of the mold, some dimensions that can be derived from the basic molding requirement parameters described above are calculated in advance, and for some dimensions that cannot be directly derived, the dimensions are determined from empirical values. The order of die sizing is therefore: (1) determining the value of the distance A between the center of the bending die and the front end of the guide mechanism:
(2) some dimensions that cannot be directly derived are determined from empirical values: 2.5D for B, 2.0D for R0, 1.6D for R1, 1.0D for C, 60 °; (3) determining the spherical radius of a spherical envelope surface matched with the bending die and the guide mechanism: r2 ═ B2+R12) 2R1 ═ 2.75D; (4) determining the length of the spherical envelope surface at the tail part of the bending die:
(5) 4 basic constraints for the theoretical maximum travel of the bending die were examined:
example 3
The outer diameter of the tube blank is D, the target minimum bending radius is 3.5D, and the limit eccentricity of a bending die is 0.7D. To determine the overall dimensions of the mold, a number of preliminary calculations may be made as described aboveThe dimensions deduced from the basic forming requirements are determined empirically for some dimensions that cannot be directly deduced. The order of die sizing is therefore: (1) determining the value of the distance A between the center of the bending die and the front end of the guide mechanism:
(2) some dimensions that cannot be directly derived are determined from empirical values: 2.8D for B, 2.2D for R0, 1.8D for R1, 1.2D for C, 60 °; (3) determining the spherical radius of a spherical envelope surface matched with the bending die and the guide mechanism: r2 ═ B2+R12) 2R1 ═ 3.07D; (4) determining the length of the spherical envelope surface at the tail part of the bending die:
(5) 4 basic constraints for the theoretical maximum travel of the bending die were examined:
while the invention has been described in terms of its preferred embodiments, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.
Claims (5)
1. A three-axis free bending die and guide mechanism matching optimization design method is characterized in that: the envelope surface of the tail part of the bending die matched with the guide mechanism is always tangent to the outer spherical surface of the guide mechanism, and the tangent line is closed; the sphere center of the envelope surface is collinear with the sphere center of the guide mechanism at the initial positionThe spherical radius R2 is related to the spherical radius R1 of the guide mechanism and the distance B from the spherical center of the bending die to the spherical center of the guide mechanism, namely R2 ═ B2+R12)/2R1。
2. The optimization design method for the cooperation of the three-axis free bending die and the guide mechanism according to claim 1, wherein the optimization design method comprises the following steps: the real-time deflection angle theta of the bending die is related to the distance B from the spherical center of the bending die to the spherical center of the guide mechanism and the eccentricity U of the bending die, namely
3. The optimization design method for the cooperation of the three-axis free bending die and the guide mechanism according to claim 1, wherein the optimization design method comprises the following steps: the real-time bending angle phi of the pipe is related to the distance A from the spherical center of the bending die to the front end of the guide mechanism and the eccentricity U of the bending die, namely
4. The optimization design method for the cooperation of the three-axis free bending die and the guide mechanism according to claim 1, wherein the optimization design method comprises the following steps: the maximum stroke of the bending die is 0.7 times of the outer diameter of the pipe.
5. The optimization design method for the cooperation of the three-axis free bending die and the guide mechanism according to claim 1, wherein the optimization design method comprises the following steps: the horizontal length ry of the tail extension line of the bending die in contact with the spherical surface of the guide mechanism is determined by the maximum stroke Umax of the bending die, namely
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| CN111250575B (en) * | 2020-02-17 | 2021-01-05 | 西北工业大学 | Double-ball bowl type die for free bending forming process |
| CN114103039A (en) * | 2020-08-27 | 2022-03-01 | 常州星宇车灯股份有限公司 | Method and device for selecting optimal die drawing direction of plastic part |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| SU740345A2 (en) * | 1977-05-19 | 1980-06-15 | Предприятие П/Я М-5755 | Die for tube bending |
| CN203678967U (en) * | 2014-01-21 | 2014-07-02 | 浙江省仙居县博达异型橡塑有限公司 | Bending forming device for guide rail in sliding door |
| CN105666842A (en) * | 2016-01-27 | 2016-06-15 | 余姚中国塑料城塑料研究院有限公司 | Processing method of high-temperature thermoplastic composite product |
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Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| SU740345A2 (en) * | 1977-05-19 | 1980-06-15 | Предприятие П/Я М-5755 | Die for tube bending |
| CN203678967U (en) * | 2014-01-21 | 2014-07-02 | 浙江省仙居县博达异型橡塑有限公司 | Bending forming device for guide rail in sliding door |
| CN105666842A (en) * | 2016-01-27 | 2016-06-15 | 余姚中国塑料城塑料研究院有限公司 | Processing method of high-temperature thermoplastic composite product |
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Inventor after: Guo Xunzhong Inventor after: Ma Ziqi Inventor after: Xiong Hao Inventor after: Li Heng Inventor after: Cheng Yi Inventor after: Ma Yannan Inventor after: Wang Hui Inventor after: Jin Kai Inventor before: Guo Xunzhong Inventor before: Ma Ziqi Inventor before: Xiong Hao Inventor before: Cheng Yi Inventor before: Ma Yannan Inventor before: Wang Hui Inventor before: Jin Kai |
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