CN116833293B - Closed loop stretch forming method of flexible stretch forming machine of electromagnetic clamp - Google Patents
Closed loop stretch forming method of flexible stretch forming machine of electromagnetic clamp Download PDFInfo
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- CN116833293B CN116833293B CN202310431905.3A CN202310431905A CN116833293B CN 116833293 B CN116833293 B CN 116833293B CN 202310431905 A CN202310431905 A CN 202310431905A CN 116833293 B CN116833293 B CN 116833293B
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- 238000004364 calculation method Methods 0.000 claims abstract description 32
- 238000004088 simulation Methods 0.000 claims abstract description 19
- 238000002360 preparation method Methods 0.000 claims abstract description 7
- 238000005520 cutting process Methods 0.000 claims abstract description 4
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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
- B21D22/00—Shaping without cutting, by stamping, spinning, or deep-drawing
- B21D22/20—Deep-drawing
- B21D22/22—Deep-drawing with devices for holding the edge of the blanks
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21C—MANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES OR PROFILES, OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL
- B21C51/00—Measuring, gauging, indicating, counting, or marking devices specially adapted for use in the production or manipulation of material in accordance with subclasses B21B - B21F
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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
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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
- B21D43/00—Feeding, positioning or storing devices combined with, or arranged in, or specially adapted for use in connection with, apparatus for working or processing sheet metal, metal tubes or metal profiles; Associations therewith of cutting devices
- B21D43/003—Positioning devices
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Abstract
The invention provides a closed loop stretch forming method of an electromagnetic clamp flexible stretch forming machine, which adopts the following steps: two-cylinder electromagnetic clamp flexible stretch forming machine, multi-point die and on-line measuring scriber; the stretch-forming method comprises the steps of performing process simulation calculation based on a target part; performing actual stretch forming preparation work according to a process simulation calculation result; carrying out actual stretch forming on the metal plate, and carrying out primary measurement; performing electromagnetic compensation forming on the metal plate, and performing secondary measurement; and scribing, cutting and storing the qualified metal plate. The stretch forming method adopts a composite process of combining stretch forming and electromagnetic forming, reduces rebound in the forming process, simplifies rebound regulation and control process, and effectively improves the forming performance of large-size metal plates.
Description
Technical Field
The invention belongs to the technical field of plastic processing of metal parts, and particularly relates to a closed-loop stretch forming method of an electromagnetic clamp flexible stretch forming machine.
Background
With the rapid development of industries such as aviation, high-speed rail, ships and the like, the processing precision requirement of the multi-curvature large-size workpiece is higher and higher, and the stretch forming process has been widely applied to the multi-curvature large-size workpiece forming process due to the characteristics of flexibility, deformation homogenization and control simplification.
However, conventional stretch forming processes employ conventional stretch forming machines such as: plate stretch forming machine (ZL 200910067003.6), plate stretch forming machine (ZL 200910067216.9), high-flexibility head stretch forming machine (ZL 20091017701. X), multi-clamp stretch forming machine (ZL 201010266441.8) and the like, and in the existing stretch forming process, the problems of uneven stress and strain distribution, large-size rebound, difficult rebound regulation and control and the like of different areas of the plate are often caused, so that qualified high-precision product parts cannot be obtained efficiently.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a closed-loop stretch forming method of an electromagnetic clamp flexible stretch forming machine, which adopts a composite process of combining stretch forming and electromagnetic forming, reduces rebound in the forming process, simplifies rebound regulation and control process, and effectively improves the forming performance of large-size metal plates.
The technical scheme of the invention is as follows:
a closed loop stretch forming method of an electromagnetic clamp flexible stretch forming machine adopts the following steps: two-cylinder electromagnetic clamp flexible stretch forming machine, multi-point die and on-line measuring scriber;
two rows of two-cylinder loading stretching mechanisms of the two-cylinder electromagnetic clamp flexible stretch forming machine are symmetrically distributed, each row of two-cylinder loading stretching mechanisms is formed by linearly arranging a plurality of two-cylinder loading stretching mechanisms with the same structure, and in the loading stretching mechanisms, a horizontal hydraulic cylinder and a vertical hydraulic cylinder are hinged with a clamp;
the multi-point die is a lower male die type multi-point die and consists of die unit bodies which are distributed in a matrix mode and can be adjusted independently in height, and the tops of the die unit bodies are swing heads containing induction coils;
the online measurement scribing instrument is used for carrying out online measurement and scribing on the metal plate in the forming process;
the control end of the drawing machine is connected with a computer terminal internally provided with intelligent drawing software, process simulation calculation of the part drawing process is realized through the intelligent drawing software, real-time data generated by actual drawing of the drawing machine and detected by a sensor are fed back to the computer terminal, and closed-loop control of the intelligent drawing process is realized;
the stretch forming method comprises the following specific steps:
s1: performing process simulation calculation based on the target part;
s2: performing actual stretch forming preparation work according to a process simulation calculation result;
s3: carrying out actual stretch forming on the metal plate, and carrying out primary measurement;
s4: performing electromagnetic compensation forming on the metal plate, and performing secondary measurement;
s5: and scribing, cutting and storing the qualified metal plate.
Further, the specific process of performing the process simulation calculation based on the target part in the step S1 is as follows:
s101, importing a three-dimensional digital model of a target part into intelligent stretch forming software, identifying the size and the material of the target part, and judging whether preheating treatment is required to be carried out on a metal plate for stretch forming or not;
s102, calculating the size of the metal plate;
s103, calculating a target part tensile critical strain value;
s104, calculating the motion trail of the electromechanical clamp of the stretch forming machine;
s105, outputting simulation process parameters.
Further, the specific process of calculating the metal sheet size in step S102 is as follows:
longitudinal dimension L of metal plate z The calculation formula is as follows:
L z ＝l+2Δkl+2l 1 +2l 2 ·············(1)
in the above formula (1):
l is the maximum value of the surface longitudinal length of the target part;
Δk is a target part margin coefficient that depends on the target part material;
l 1 the horizontal distance from the electromagnetic jaw of the stretch forming machine to the stretch forming die;
l 2 for the engagement length of electromagnetic clamps；
Transverse dimension B of metal plate h The calculation formula is as follows:
B h ＝b+2Δkb··············(2)
in the above formula (2):
b is the maximum value of the transverse length of the unfolded surface of the target part;
Δk is a target part margin coefficient that depends on the target part material.
Further, the specific process of calculating the tensile critical strain value of the target part in step S103 is as follows:
target part tensile critical strain value epsilon Critical of The calculation formula is as follows:
in the above formula (3):
t is the thickness of the metal plate;
r is the maximum curvature diameter of the multipoint mould, and the maximum curvature diameter R of the multipoint mould is input into intelligent drawing software in advance as known data of the multipoint mould;
sigma is the yield strength of the plate;
e is the elastic modulus of the plate.
Further, the specific process of calculating the motion track of the electromagnetic clamp of the stretch forming machine in the step S104 is as follows:
the transverse motion track of the electromagnetic clamp of the stretch forming machine is as follows:
in the above formula (4):
Δx is the current point clamp lateral movement displacement, i.e. the last point to current point clamp lateral displacement;
x i the upper clamp is laterally displaced;
l r is the minimum interface edge length of the multipoint mould,representing the maximum boundary range which can be formed by the multipoint mould;
t is the stretching time of the current point;
θ is the inclination angle of the metal plate section and the tangent line of the multipoint mold, and is a dynamic update value, as shown in fig. 6;
t is the total length of the stretching process;
l is the maximum value of the surface longitudinal length of the target part;
the longitudinal movement track of the electromagnetic clamp of the stretch forming machine is as follows:
in the above formula (5):
Δz is the current point clamp longitudinal displacement, i.e. the last point to current point clamp longitudinal displacement;
the cross section curve equation of the multi-point die is adopted;
l is the maximum value of the surface longitudinal length of the target part;
θ is the inclination angle of the metal plate section and the tangent line of the multipoint mold, and is a dynamic update value, as shown in fig. 6;
l r representing the maximum boundary range which can be formed by the multipoint mould for the minimum boundary line length of the multipoint mould;
t is the stretching time of the current point;
t is the total length of the stretching process;
and phi (0, z) is x=0, and the section curve equation of the multipoint mold.
Further, the actual stretch-forming preparation in step S2 includes:
(1) the electromagnetic clamp is electrified to clamp the metal plate;
(2) adjusting the height of each die unit body in the multipoint die according to the process simulation calculation result to form a lower convex die surface matched with the shape of the stretched target part;
(3) placing an elastic rubber pad on the surface of the regulated multipoint mould;
(4) judging whether preheating treatment is needed according to the material of the target part, if so, controlling the flow and the magnitude of current flowing through the electromagnetic clamp, and preheating the metal plate by self-resistance heating of the electromagnetic clamp.
Further, in the step S3, the actual stretch-forming process is as follows: according to the motion track of the optimal stretch-forming machine electromagnetic clamp obtained through calculation in the steps, controlling the horizontal hydraulic cylinder and the vertical hydraulic cylinder to stretch and load to control the motion of the electromagnetic clamp, further attaching the metal plate to the multi-point die which is formed in an adjusting mode, in the stretch-forming process of the metal plate, identifying the stretch strain value of the metal plate by a strain sensor, and when the stretch strain value reaches the target part stretch critical strain value obtained through calculation in the steps, sending a signal to a computer terminal storing intelligent stretch-forming software, and stopping the stretch process.
Further, in the step S3, the primary measurement process is as follows:
s301, controlling to reduce current flowing through an electromagnetic clamp, and adsorbing the metal plate by utilizing electromagnetic induction to maintain the shape of the metal plate after rebound;
s302, performing primary measurement on the metal plate subjected to stretch forming by using an online measurement scriber, and sending a measurement result to a computer terminal storing intelligent stretch forming software;
s303, judging whether the stretched metal plate is qualified or not by calculating the curvature average error, if not, entering the step S4, and if so, entering the step S5.
Further, the electromagnetic compensation stretch forming process in the step S4 includes the following three modes:
(1) the electromagnetic clamp clamps the metal plate of the column, the top of each die unit body in the multipoint die is electrified to generate electromagnetic attraction with the metal plate, so that the metal plate is further subjected to plastic deformation, and electromagnetic compensation stretch-forming is realized;
(2) the electromagnetic clamp clamps the metal plate of the column, the top of the multipoint mould swings and is electrified, the height of each mould unit body in the multipoint mould is regulated, and the metal plate is further subjected to plastic deformation through the electromagnetic attraction of the multipoint mould and the jacking of the multipoint mould, so that electromagnetic compensation stretch-forming is realized;
(3) the electromagnetic clamp clamps the metal plate of the column, the top of the multi-point die swings and is electrified, the height of each die unit in the multi-point die is adjusted, the electromagnetic clamp is electrified, and the metal plate is further subjected to plastic deformation jointly through electromagnetic attraction of the multi-point die, jacking of the multi-point die and the electromagnetic clamp electrification, so that electromagnetic compensation stretch-forming is realized.
Furthermore, three electromagnetic compensation drawing modes are sequentially and circularly carried out according to the priority order of (1), (2) and (3), after the electromagnetic compensation drawing is completed in one mode, secondary measurement is carried out through an online measurement scribing instrument, and along with each electromagnetic compensation drawing, the measurement result is iterated until the metal plate after the electromagnetic compensation drawing is qualified in forming, and the electromagnetic compensation drawing is finished.
Compared with the prior art, the invention has the beneficial effects that:
1. the stretch forming method adopts a composite process combining electromagnetic clamp stretch forming and electromagnetic compensation forming, reduces rebound in the forming process, simplifies rebound regulation and control process, and improves the forming performance of large-size metal plates.
2. According to the stretch forming method, after stretch forming is matched with electromagnetic forming, the inner flow of the metal plate can be effectively increased, the thickness reduction of the area most prone to fracture is reduced, and therefore the inner flow rate of the metal plate is effectively improved.
3. According to the stretch forming method, after the metal plate is stretched and formed, the metal plate can generate high-frequency oscillation phenomenon only by small plastic deformation through electromagnetic induction, and the thickness reduction can be effectively reduced through small plastic deformation.
Drawings
FIG. 1 is a schematic view of the overall structure of a stretch forming apparatus in the stretch forming method according to the present invention;
FIG. 2 is a schematic diagram of a two-cylinder loading and stretching mechanism in a stretch forming apparatus in a stretch forming method according to the present invention;
FIG. 3a is a schematic diagram of a multi-point die prior to forming in the stretch forming method of the present invention;
FIG. 3b is a schematic view of a multi-point die after forming in the stretch-forming method according to the present invention;
FIG. 4 is a schematic view of the top structure of a die unit body of a multi-point die in the stretch forming method according to the present invention;
FIG. 5 is a flow chart of the stretch forming method of the present invention;
FIG. 6 is a schematic view showing the inclination angle between the section of the metal plate and the tangent line of the multipoint mold in the drawing method according to the present invention;
FIG. 7 is a schematic diagram of the electromagnetic clamp for clamping a metal sheet in the stretch forming method according to the present invention;
FIG. 8 is a drawing of sheet metal in the drawing method of the present invention;
FIG. 9 is a schematic view showing the shape of a metal sheet after rebound in the stretch forming method according to the present invention;
FIG. 10 is a schematic diagram showing the plastic deformation of a metal sheet by the electromagnetic attraction of a multi-point die and the pressing of the multi-point die in the drawing method of the present invention;
FIG. 11 is a schematic diagram showing the plastic deformation of a metal sheet by the electromagnetic attraction of a multi-point die and the pressing of the multi-point die in the drawing method of the invention;
FIG. 12 is a drawing of a metal sheet with an on-line measurement scriber in a method of drawing according to the present invention;
in the figure:
the drawing machine comprises a 1-drawing frame, a 2-two-cylinder loading drawing mechanism, a 3-multi-point die, a 4-on-line measuring scriber, a 5-metal plate and a 6-elastic rubber pad;
201-horizontal hydraulic cylinder, 202-vertical hydraulic cylinder, 203-electromagnetic clamp.
Detailed Description
For a clear and complete description of the technical scheme and the specific working process thereof, the following specific embodiments of the invention are provided with reference to the accompanying drawings in the specification:
in the present invention, unless explicitly specified and limited otherwise, the terms "mounted," "connected," "secured," and the like are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; either directly or indirectly, through intermediaries, or both, may be in communication with each other or in interaction with each other, unless expressly defined otherwise. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art according to the specific circumstances.
In the present invention, unless expressly stated or limited otherwise, a first feature "up" or "down" a second feature may be the first and second features in direct contact, or the first and second features in indirect contact via an intervening medium. Moreover, a first feature being "above," "over" and "on" a second feature may be a first feature being directly above or obliquely above the second feature, or simply indicating that the first feature is level higher than the second feature. The first feature being "under", "below" and "beneath" the second feature may be the first feature being directly under or obliquely below the second feature, or simply indicating that the first feature is less level than the second feature.
In the description of the present specification, a description referring to terms "one embodiment," "some embodiments," "examples," "specific examples," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, the different embodiments or examples described in this specification and the features of the different embodiments or examples may be combined and combined by those skilled in the art without contradiction.
The invention discloses a closed loop stretch forming method of an electromagnetic clamp flexible stretch forming machine, which is characterized in that the structure of stretch forming equipment adopted by the stretch forming method is briefly introduced for more clearly describing the stretch forming method:
the stretch forming equipment adopted by the stretch forming method comprises the following steps: two jar type electromagnetism clamp flexible stretch forming machines, multiple spot mould and online measurement marking instrument, wherein:
as shown in fig. 1, in the two-cylinder electromagnetic clamp flexible stretch forming machine, two rows of two-cylinder loading stretching mechanisms are symmetrically distributed and are respectively arranged at the inner side of the stretch forming rack 1, each row of two-cylinder loading stretching mechanisms is formed by linearly arranging a plurality of two-cylinder loading stretching mechanisms 2 with the same structure, and the two-cylinder loading stretching mechanisms 2 are used for clamping a plate material at corresponding positions so as to apply stretching force to the metal plate material.
As shown in fig. 2, the two-cylinder loading stretching mechanism 2 includes: the horizontal hydraulic cylinder 201, the vertical hydraulic cylinder 202 and the electromagnetic clamp 203, wherein the horizontal hydraulic cylinder 201 is horizontally arranged, the loading end of the horizontal hydraulic cylinder 201 is hinged to the electromagnetic clamp 203, the bottom of the cylinder body of the horizontal hydraulic cylinder 201 is hinged to the stretch-forming frame 1, the vertical hydraulic cylinder 202 is vertically arranged, the loading end of the vertical hydraulic cylinder 202 is hinged to the electromagnetic clamp 203, the bottom of the cylinder body of the vertical hydraulic cylinder 202 is hinged to the stretch-forming frame 1, and the stretching force and the direction of the stretch-forming force implemented by the electromagnetic clamp 203 are controlled by cooperatively controlling the hydraulic pressure output by the horizontal hydraulic cylinder 201 and the vertical hydraulic pressure output by the vertical hydraulic cylinder 202, so that the tension or the thrust is applied to the metal plate, and the metal plate is stretched, deformed and attached to the upper surface of the multi-point die 3. The electromagnetic clamp 203 is an imitation animal claw electric control permanent magnet clamping mechanism with a self-resistance heating function, on one hand, the electromagnetic clamp 203 is electrified to electrify metal plates, and on the other hand, the electromagnetic clamp 203 is electrified to realize self-resistance heating so as to preheat the metal plates clamped by the electromagnetic clamp 203.
As shown in fig. 1, the multi-point mold 3 is a multi-point mold with a downward convex mode, the multi-point mold 3 is disposed on a base at a middle position of a stretch-forming area inside the stretch-forming frame 1, the multi-point mold 3 is composed of mold unit bodies which are distributed in a matrix and whose heights can be independently adjusted, and a downward convex mold surface matched with the shape of a target curved surface part formed by stretching is formed by adjusting the heights of the mold unit bodies. As shown in fig. 4, after the top of the die unit body forming the multipoint die 3 is provided with the swinging head containing the inductance coil, the inductance coil swinging the top of the die unit body is electrified to generate magnetic force, and at the same time, when the metal plate material of which the upper surface of the multipoint die 3 is subjected to preliminary forming is electrified, the top swinging head of the multipoint die 3 which is electrified simultaneously generates electromagnetic attraction force with the metal plate material, so that the metal plate material is further subjected to plastic deformation.
As shown in fig. 5, in the operation of the multipoint mold 3, a layer of elastic rubber pad 6 is disposed between the metal plate 5 and the multipoint mold 3, the elastic rubber pad 6 prevents dent defects from being formed during the forming process of the metal plate 5 on one hand, and an insulating layer is formed between the multipoint mold 3 and the metal plate 5 on the other hand, the thickness of the elastic rubber pad 6 is 1mm, and the elastic rubber pad is specifically disposed on the mold surface of the upper surface of the multipoint mold 3.
As shown in fig. 1, the online measurement scriber 4 is disposed above the stretching area, and is used for online measurement and scribing of the metal sheet in the forming process.
In addition, the control end of the drawing machine is connected with a computer terminal, intelligent drawing software is arranged in the computer terminal, process simulation calculation of the part drawing process is realized through the intelligent drawing software, and real-time data generated by actual drawing of the drawing machine and detected by a sensor are fed back to the computer terminal, so that closed-loop control of the intelligent drawing process is realized.
Based on the stretch forming apparatus, as shown in fig. 5, the specific steps of the stretch forming method are as follows:
s1: performing process simulation calculation based on the target part;
the specific process of this step S1 is as follows:
s101, importing a three-dimensional digital model of a target part into intelligent stretch forming software, identifying the size and the material of the target part, and judging whether preheating treatment is required to be carried out on a metal plate for stretch forming or not;
the three-dimensional digital model of the target part comprises shape and size data, and the size comprises the length, the width, the height, the thickness and the curvature of the target part;
s102, calculating the size of the metal plate;
longitudinal dimension L of metal plate z The calculation formula is as follows:
L z ＝l+2Δkl+2l 1 +2l 2 ·············(1)
in the above formula (1):
l is the maximum value of the surface longitudinal length of the target part;
Δk is a target part margin coefficient, and the target part margin coefficient depends on the material of the target part and takes a value of 0.1-0.3;
l 1 the horizontal distance from the electromagnetic jaw of the stretch forming machine to the stretch forming die;
l 2 is the engagement length of the electromagnetic clamp;
transverse dimension B of metal plate h The calculation formula is as follows:
B h ＝b+2Δkb·············(2)
in the above formula (2):
b is the maximum value of the transverse length of the unfolded surface of the target part;
Δk is a target part margin coefficient, and the target part margin coefficient depends on the material of the target part and takes a value of 0.1-0.3;
s103, calculating a target part tensile critical strain value;
target part tensile critical strain value epsilon Critical of The calculation formula is as follows:
in the above formula (3):
t is the thickness of the metal plate;
r is the maximum curvature diameter of the multipoint mould, and the maximum curvature diameter R of the multipoint mould is input into intelligent drawing software in advance as known data of the multipoint mould;
sigma is the yield strength of the plate;
e is the elastic modulus of the plate;
s104, calculating the motion trail of the electromechanical clamp of the stretch forming machine;
the transverse motion track of the electromagnetic clamp of the stretch forming machine is as follows:
in the above formula (4):
Δx is the current point clamp lateral movement displacement, i.e. the last point to current point clamp lateral displacement;
x i the upper clamp is laterally displaced;
l r representing the maximum boundary range which can be formed by the multipoint mould for the minimum boundary line length of the multipoint mould;
t is the stretching time of the current point;
θ is the inclination angle of the metal plate section and the tangent line of the multipoint mold, and is a dynamic update value, as shown in fig. 6;
t is the total length of the stretching process;
l is the maximum value of the surface longitudinal length of the target part;
the longitudinal movement track of the electromagnetic clamp of the stretch forming machine is as follows:
in the above formula (5):
Δz is the current point clamp longitudinal displacement, i.e. the last point to current point clamp longitudinal displacement;
the cross section curve equation of the multi-point die is adopted;
l is the maximum value of the surface longitudinal length of the target part;
θ is the inclination angle of the metal plate section and the tangent line of the multipoint mold, and is a dynamic update value, as shown in fig. 6;
l r representing the maximum formable of the multipoint mould for the minimum interface edge length of the multipoint mouldBoundary range;
t is the stretching time of the current point;
t is the total length of the stretching process;
a cross-sectional curve equation of the multipoint mold at a time when phi (0, z) is x=0;
s105, outputting simulation process parameters;
in the step S105, simulation process parameters including the metal sheet size, the target part tensile critical strain value, the motion track of the drawing machine electromechanical clamp, etc. obtained by calculation in the previous step are output and stored into a command memory of a computer terminal, and the computer terminal is respectively connected with the multipoint mold, the drawing mechanism and the on-line measurement scriber by signals.
S2: performing actual stretch forming preparation work according to a process simulation calculation result;
the actual stretch-forming preparation comprises:
(1) as shown in fig. 7, the electromagnetic clamp is electrified to clamp the metal plate;
(2) adjusting the height of each die unit body in the multipoint die according to the process simulation calculation result to form a lower convex die surface matched with the shape of the stretched target part;
(3) placing an elastic rubber pad with the thickness of 1mm on the surface of the regulated multipoint mould;
(4) judging whether preheating treatment is needed according to the material of the target part, if so, controlling the flow and the magnitude of current flowing through the electromagnetic clamp, and preheating the metal plate by self-resistance heating of the electromagnetic clamp, wherein the preheating time and the preheating target temperature are both dependent on the material of the target part.
S3: carrying out actual stretch forming on the metal plate, and carrying out primary measurement;
in this step S3, the actual stretch-forming process is: as shown in FIG. 8, according to the motion track of the optimal drawing machine electric clamp obtained by calculation in the previous step, the horizontal hydraulic cylinder and the vertical hydraulic cylinder are controlled to stretch and load to control the motion of the electromagnetic clamp so as to form the metal plate and the multi-point die which is formed in a fitting way, the stretching speed is 0.5-1mm/s, in the stretching forming process of the metal plate, the strain sensor identifies the stretching strain value of the metal plate, and when the stretching strain value reaches the target part stretching critical strain value obtained by calculation in the previous step, a signal is sent to a computer terminal which stores intelligent drawing software, and the stretching process is stopped.
In this step S3, the primary measurement process is:
s301, as shown in FIG. 9, controlling to reduce the current flowing through the electromagnetic clamp, and adsorbing the metal plate by utilizing electromagnetic induction to maintain the shape of the metal plate after rebound;
s302, performing primary measurement on the metal plate subjected to stretch forming by using an online measurement scriber, and sending a measurement result to a computer terminal storing intelligent stretch forming software;
s303, judging whether the stretched metal plate is qualified or not by calculating the curvature average error, if not, entering the step S4, and if so, entering the step S5.
The calculation formula of the curvature average error value delta is as follows:
in the above formula (6):
n is the number of measurement points; n (N) i Height coordinates of the i-th measurement point of the part being stretch-formed; n (N) i1 The height coordinate of the ith measuring point of the target part;
and when the curvature average error value delta is smaller than a preset value 5, judging whether the stretched metal plate is qualified or not, and if not, judging that the stretched metal plate is unqualified.
S4: performing electromagnetic compensation forming on the metal plate, and performing secondary measurement;
the step S4 is because the metal sheet is actually stretch-formed in the step S3 to obtain no qualified stretch-formed metal sheet, and then the electromagnetic compensation stretch-forming process is performed on the metal sheet, where the electromagnetic compensation stretch-forming process includes the following three modes:
(1) the electromagnetic clamp clamps the metal plate of the column, the top of each die unit body in the multi-point die is electrified in a swinging way, and electromagnetic attraction force is generated between the die unit bodies and the metal plate, so that the metal plate is further subjected to plastic deformation, and electromagnetic compensation stretch-forming is realized.
(2) The electromagnetic clamp clamps the metal plate of the column, the top of the multipoint mould swings and is electrified, and meanwhile, the height of each mould unit body in the multipoint mould is adjusted, as shown in fig. 10 and 11, the metal plate is further subjected to plastic deformation through the electromagnetic attraction of the multipoint mould and the jacking of the multipoint mould, so that electromagnetic compensation stretch forming is realized.
(3) The electromagnetic clamp clamps the metal plate of the column, the top of the multi-point die swings and is electrified, the height of each die unit in the multi-point die is adjusted, the electromagnetic clamp is electrified, and the metal plate is further subjected to plastic deformation jointly through electromagnetic attraction of the multi-point die, jacking of the multi-point die and the electromagnetic clamp electrification, so that electromagnetic compensation stretch-forming is realized.
The electrified current of the electromagnetic clamp is 13-14 kv, and the current is adjusted according to different actual working conditions.
The three electromagnetic compensation drawing modes are sequentially and circularly carried out according to the priority order of (1), (2) and (3), secondary measurement is carried out through an online measurement scribing instrument after the electromagnetic compensation drawing is completed in one mode, as shown in fig. 12, and the measurement result is iterated along with each electromagnetic compensation drawing until the average curvature error of the metal plate after the electromagnetic compensation drawing is smaller than a preset value, the metal plate is qualified in forming, and the electromagnetic compensation drawing is finished.
The measurement result iteration process comprises the following steps:
A. measuring the position coordinates of the formed metal plate in the X, Y and Z directions;
B. fitting and measuring geometric digital-analog of the formed metal plate and original digital-analog of the part for comparison analysis;
C. the top of the multipoint mould swings, and the current flowing through the plate material is analyzed through an electromagnetic clamp;
D. and adjusting the height of the corresponding multipoint mould unit body to compensate.
S5: and scribing, cutting and storing the qualified metal plate.
In the step S5, the electromagnetic formed metal plate is scribed through an on-line measurement scriber, then the qualified metal plate is cut and formed, a qualified part is obtained, and finally the stretch forming process of the qualified part is memorized and stored through an intelligent system, so that the subsequent processing process of the same part is simplified, and the highly-automatic and intelligent stretch forming process of the stretch forming machine is realized.
While embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and not to be construed as limiting the invention, and that variations, modifications, alternatives and variations may be made to the above embodiments by one of ordinary skill in the art within the scope of the invention.
The above-described embodiments of the present invention do not limit the scope of the present invention. Any of various other corresponding changes and modifications made according to the technical idea of the present invention should be included in the scope of the claims of the present invention.
Claims (7)
1. A closed loop stretch forming method of an electromagnetic clamp flexible stretch forming machine is characterized in that:
the stretch forming method adopts the following steps: two-cylinder electromagnetic clamp flexible stretch forming machine, multi-point die and on-line measuring scriber;
two rows of two-cylinder loading stretching mechanisms of the two-cylinder electromagnetic clamp flexible stretch forming machine are symmetrically distributed, each row of two-cylinder loading stretching mechanisms is formed by linearly arranging a plurality of two-cylinder loading stretching mechanisms with the same structure, and in the loading stretching mechanisms, a horizontal hydraulic cylinder and a vertical hydraulic cylinder are hinged with a clamp;
the multi-point die is a lower male die type multi-point die and consists of die unit bodies which are distributed in a matrix mode and can be adjusted independently in height, and the tops of the die unit bodies are swing heads containing induction coils;
the online measurement scribing instrument is used for carrying out online measurement and scribing on the metal plate in the forming process;
the control end of the drawing machine is connected with a computer terminal internally provided with intelligent drawing software, process simulation calculation of the part drawing process is realized through the intelligent drawing software, real-time data generated by actual drawing of the drawing machine and detected by a sensor are fed back to the computer terminal, and closed-loop control of the intelligent drawing process is realized;
the stretch forming method comprises the following specific steps:
s1: the process simulation calculation is carried out based on the target part, and the specific process is as follows:
s101, importing a three-dimensional digital model of a target part into intelligent stretch forming software, identifying the size and the material of the target part, and judging whether preheating treatment is required to be carried out on a metal plate for stretch forming or not;
s102, calculating the size of the metal plate;
s103, calculating a target part tensile critical strain value;
s104, calculating the motion trail of the electromagnetic clamp of the stretch forming machine, wherein the specific process is as follows:
the transverse motion track of the electromagnetic clamp of the stretch forming machine is as follows:
in the above formula (1):
Δx is the current point clamp lateral movement displacement, i.e. the last point to current point clamp lateral displacement;
x i the upper clamp is laterally displaced;
l r representing the maximum boundary range which can be formed by the multipoint mould for the minimum boundary line length of the multipoint mould;
t is the stretching time of the current point;
θ is the inclination angle between the section of the metal plate and the tangent line of the multipoint mold, and is a dynamic update value;
t is the total length of the stretching process;
l is the maximum value of the surface longitudinal length of the target part;
the longitudinal movement track of the electromagnetic clamp of the stretch forming machine is as follows:
in the above formula (2):
Δz is the current point clamp longitudinal displacement, i.e. the last point to current point clamp longitudinal displacement;
the cross section curve equation of the multi-point die is adopted;
l is the maximum value of the surface longitudinal length of the target part;
θ is the inclination angle between the section of the metal plate and the tangent line of the multipoint mold, and is a dynamic update value;
l r representing the maximum boundary range which can be formed by the multipoint mould for the minimum boundary line length of the multipoint mould;
t is the stretching time of the current point;
t is the total length of the stretching process;
a cross-sectional curve equation of the multipoint mold at a time when phi (0, z) is x=0;
s105, outputting simulation process parameters;
s2: performing actual stretch forming preparation work according to a process simulation calculation result;
s3: carrying out actual stretch forming on the metal plate, and carrying out primary measurement;
s4: performing electromagnetic compensation forming on the metal plate, and performing secondary measurement;
the electromagnetic compensation forming process comprises the following three modes:
(1) the electromagnetic clamp clamps the metal plate of the column, the top of each die unit body in the multipoint die is electrified to generate electromagnetic attraction with the metal plate, so that the metal plate is further subjected to plastic deformation, and electromagnetic compensation stretch-forming is realized;
(2) the electromagnetic clamp clamps the metal plate of the column, the top of the multipoint mould swings and is electrified, the height of each mould unit body in the multipoint mould is regulated, and the metal plate is further subjected to plastic deformation through the electromagnetic attraction of the multipoint mould and the jacking of the multipoint mould, so that electromagnetic compensation stretch-forming is realized;
(3) the electromagnetic clamp clamps the metal plate of the column, the top of the multi-point die swings and is electrified, the height of each die unit body in the multi-point die is adjusted, the electromagnetic clamp is electrified, and the metal plate is further subjected to plastic deformation by the electromagnetic attraction of the multi-point die, the jacking of the multi-point die and the electromagnetic clamp electrification, so that the electromagnetic compensation stretch-forming is realized;
s5: and scribing, cutting and storing the qualified metal plate.
2. The closed loop stretch forming method of the flexible stretch forming machine of the electromagnetic clamp according to claim 1, wherein the method comprises the following steps:
the specific process of calculating the metal plate size in step S102 is as follows:
longitudinal dimension L of metal plate z The calculation formula is as follows:
L z ＝l+2Δkl+2l 1 +2l 2 ·············(3)
in the above formula (3):
l is the maximum value of the surface longitudinal length of the target part;
Δk is a target part margin coefficient that depends on the target part material;
l 1 the horizontal distance from the electromagnetic jaw of the stretch forming machine to the stretch forming die;
l 2 is the engagement length of the electromagnetic clamp;
transverse dimension B of metal plate h The calculation formula is as follows:
B h ＝b+2Δkb··············(4)
in the above formula (4):
b is the maximum value of the transverse length of the unfolded surface of the target part;
Δk is a target part margin coefficient that depends on the target part material.
3. The closed loop stretch forming method of the flexible stretch forming machine of the electromagnetic clamp according to claim 2, wherein the method comprises the following steps:
the specific process of calculating the tensile critical strain value of the target part in the step S103 is as follows:
target part tensile critical strain value epsilon Critical of The calculation formula is as follows:
in the above formula (5):
t is the thickness of the metal plate;
r is the maximum curvature diameter of the multipoint mould, and the maximum curvature diameter R of the multipoint mould is input into intelligent drawing software in advance as known data of the multipoint mould;
sigma is the yield strength of the plate;
e is the elastic modulus of the plate.
4. The closed loop stretch forming method of the flexible stretch forming machine of the electromagnetic clamp according to claim 1, wherein the method comprises the following steps:
the actual stretch-forming preparation in step S2 includes:
(1) the electromagnetic clamp is electrified to clamp the metal plate;
(2) adjusting the height of each die unit body in the multipoint die according to the process simulation calculation result to form a lower convex die surface matched with the shape of the stretched target part;
(3) placing an elastic rubber pad on the surface of the regulated multipoint mould;
(4) judging whether preheating treatment is needed according to the material of the target part, if so, controlling the flow and the magnitude of current flowing through the electromagnetic clamp, and preheating the metal plate by self-resistance heating of the electromagnetic clamp.
5. The closed loop stretch forming method of the flexible stretch forming machine of the electromagnetic clamp according to claim 1, wherein the method comprises the following steps:
in the step S3, the actual stretch-forming process is as follows: according to the motion track of the optimal stretch-forming machine electromagnetic clamp obtained through calculation in the steps, controlling the horizontal hydraulic cylinder and the vertical hydraulic cylinder to stretch and load to control the motion of the electromagnetic clamp, further attaching the metal plate to the multi-point die which is formed in an adjusting mode, in the stretch-forming process of the metal plate, identifying the stretch strain value of the metal plate by a strain sensor, and when the stretch strain value reaches the target part stretch critical strain value obtained through calculation in the steps, sending a signal to a computer terminal storing intelligent stretch-forming software, and stopping the stretch process.
6. The closed loop stretch forming method of the flexible stretch forming machine of the electromagnetic clamp according to claim 1, wherein the method comprises the following steps:
in the step S3, the primary measurement process is as follows:
s301, controlling to reduce current flowing through an electromagnetic clamp, and adsorbing the metal plate by utilizing electromagnetic induction to maintain the shape of the metal plate after rebound;
s302, performing primary measurement on the metal plate subjected to stretch forming by using an online measurement scriber, and sending a measurement result to a computer terminal storing intelligent stretch forming software;
s303, judging whether the stretched metal plate is qualified or not by calculating the curvature average error, if not, entering the step S4, and if so, entering the step S5.
7. The closed loop stretch forming method of the flexible stretch forming machine of the electromagnetic clamp according to claim 1, wherein the method comprises the following steps:
the three electromagnetic compensation drawing modes are sequentially and circularly carried out according to the priority order of (1), (2) and (3), after the electromagnetic compensation drawing is completed in one mode, the two-level measurement is carried out through an online measurement scribing instrument, the measurement result is iterated along with each electromagnetic compensation drawing, until the metal plate after the electromagnetic compensation drawing is qualified in forming, and the electromagnetic compensation drawing is finished.
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