CN110788193B - Controllable medium cold stamping forming process method and die structure thereof - Google Patents
Controllable medium cold stamping forming process method and die structure thereof Download PDFInfo
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- CN110788193B CN110788193B CN201911037095.3A CN201911037095A CN110788193B CN 110788193 B CN110788193 B CN 110788193B CN 201911037095 A CN201911037095 A CN 201911037095A CN 110788193 B CN110788193 B CN 110788193B
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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
- 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
- B21D37/01—Selection of materials
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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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Abstract
The invention provides a controllable medium cold stamping forming process method and a die structure thereof, wherein the die is provided with an upper die and a lower die, a deformable polyurethane male die is arranged on the lower die, a groove for guiding deformation is formed in one side of the polyurethane male die facing a plate to be formed, the upper die is provided with a rigid female die, a closed groove is formed in the female die, the shape of the closed groove is consistent with that of a product, and an exhaust hole is formed in the bottom of the groove. The profile of the fillet of the groove on the polyurethane male die is larger than that of the groove on the female die, and the depth of the groove on the polyurethane male die is gradually deepened from outside to inside. The controllable medium cold stamping forming process method and the die structure thereof provided by the invention eliminate the defects of the surface products around the groove caused by the traditional process, are particularly suitable for the forming problem of the characteristics of the groove on the stamping part, reduce the research and distribution workload in the die manufacturing process, reduce the repair rate, and have the advantages of simple structure, convenient manufacture, stable material pressing and convenient maintenance.
Description
Technical Field
The invention belongs to the technical field of stamping, and particularly relates to a controllable medium cold stamping forming process method and a die structure thereof.
Background
Groove-like structures exist on many cold stamped parts, such as automobile door outer panel hand-clinch grooves, hemispherical structural members, and the like, and such groove shapes are typically achieved using draw forming processes. However, due to the limitation of the drawing process itself, surface defects such as pits, wrinkles, etc. are easily generated around the groove, thereby affecting the quality of the product, and therefore, a great amount of manpower and material resources are consumed in order to optimize the quality during the debugging of the mold.
For an external covering part with higher requirement on the quality of a surface product, such as an external door wrench buckle area of an automobile, the hand buckle shape is an important shape characteristic on the appearance of the automobile except for the edge line shape of the side surface of the automobile body, the quality of the surface product around the hand buckle can be focused during the Audit evaluation, and the surface defect is more easily generated around the hand buckle formed by adopting a drawing process under the condition that the edge line of the automobile body penetrates through the hand buckle, so that the overall appearance effect is influenced.
Such groove structures are typically formed in a drawing process in the first stage of a stamping die, with the buckle shape being formed by negative forming of a female die. In the drawing forming process, the force of the convex shape of the upper die on the plate material in the groove fillet of the male die is far greater than the pulling force applied to the plate material outside the groove fillet of the male die, so the plate material outside the fillet can cross the fillet and flow into the groove, the uneven inflow of the plate material is aggravated by the irregular shape of the groove, uneven tangential compressive stress exists on the plate material around the groove, the generation of surface product defects is caused, and even if strong pressure is applied to the peripheral area of the groove, the defects cannot be completely solved. Therefore, a solution to such technical problems is needed.
Disclosure of Invention
The invention aims to provide a controllable medium cold stamping forming process method and a die structure thereof, which solve the technical problems of tangential pressure stress and sheet material flowing outside a closed groove fillet, eliminate the surface product defects around a product groove, reduce the research and preparation workload in die manufacturing, shorten the manufacturing period, and have the advantages of simple structure, convenient manufacturing, stable material pressing and convenient maintenance.
A controllable medium cold stamping forming process method comprises the following steps:
step S1, in the mold preparation stage, an upper mold is fixed on an upper sliding block of a press through bolts, the upper mold is a female mold, a lower mold is composed of a material pressing ring and a deformable polyurethane male mold, a groove is formed in the male mold, and the lower mold is fixed on a workbench of the press through bolts;
the contour of the groove on the male die is larger than that of the groove of the female die to be formed, and the groove on the male die completely covers the groove on the female die;
step S2: in the preparation stage, the material pressing ring is jacked to the working height by a support rod of a workbench of a press, and the material pressing ring and a male die support a forming plate;
step S3: in the pressing-down stage, the upper sliding block moves downwards, the upper die and the pressing ring compress the plate material to provide enough pressing force, the plate material is compressed on the polyurethane male die and the pressing ring, and the pressing ring starts to move downwards under the action of the upper die along with the continuous downward movement of the upper sliding block;
the plate begins to deform under the action of the upper die, the material pressing ring and the male die, and the part contacting the plate deforms firstly;
step S4: in the deformation starting stage, as the polyurethane male die has deformability, deformation is started at the inner edge part of the polyurethane male die, which is contacted with the plate material, along with the continuous increase of pressure, the material of the male die gradually deforms from outside to inside from the fillet part of the groove and expands towards the inner side, the groove on the male die is gradually filled and leveled and bulges, and the edge position of the polyurethane male die is contacted with the plate material earlier than the inner part;
the polyurethane male die gradually deforms and compresses the plate material, and the plate material gradually reaches the groove fillet edge part of the female die;
step S5: in the deformation development stage, when the force transmitted by the deformed polyurethane male die is large, the plate begins to deform along the fillet of the female die and gradually clings to the fillet of the female die, and the plate is pressed in the thickness direction all the time by the force transmitted by the polyurethane male die without radial tensile stress, so that the plate outside the fillet of the female die groove cannot flow into a closed groove to be formed;
step S6: in the later forming stage, along with the gradual deformation of the polyurethane male die, the deformed area of the polyurethane male die becomes a pressing area, along with the continuous forming, the pressing area becomes larger continuously, the plate outside the to-be-formed closed groove fillet is difficult to flow into the closed groove under the effects of pressing force and fillet resistance, and the plate in the groove is slowly attached to the inner wall along the edge of the female die under the effect of the polyurethane male die;
step S7: and at the end of the deformation, the groove of the polyurethane male die is filled with the self-deformed material and is protruded into the shape of the groove of the female die, in the whole forming process, the plate to be deformed in the groove of the female die is always in a state of plane bidirectional tensile stress, the formed plate is completely attached to the inner wall of the female die, and finally the shape of a closed groove is formed on the plate.
In the step S1, the upper die is provided with a convex shape for the shape of the reverse forming groove, which is consistent with the shape of the product;
the male die is provided with a groove shape for reversely forming the groove shape, and the groove profile of the male die is larger than that of a product.
In the step S2, the sheet material in the groove is in a free state, and the pressing force provided by the upper die and the pressing ring only presses the sheet material tightly.
The lower die is provided with a deformable polyurethane male die, and one side of the polyurethane male die, which faces the plate to be formed, is provided with a groove shape for guiding deformation;
the upper die is a rigid female die, a groove with the shape consistent with that of a product is arranged on the female die, and the size of the outer contour of the groove on the polyurethane male die is larger than that of the outer contour of the groove on the female die.
The polyurethane male die is made of polyurethane variable materials with certain hardness and toughness.
The hardness of the polyurethane is 80-95 Shore hardness.
The thickness of the polyurethane male die is greater than or equal to 80mm and is determined according to specific product sizes.
The polyurethane male die is characterized in that the upper groove of the polyurethane male die is arc-shaped, and the groove is free of edges and is provided with a rounding circle.
The bottom of the groove on the female die is provided with an exhaust hole, and the diameter of the exhaust hole is 4-6 mm.
The lapping surface of the polyurethane male die and the material pressing ring is a plane or a curved surface.
The invention achieves the following remarkable effects:
(1) the invention can form a perfect groove structure on a metal plate, can control the thickness distribution of a final product after forming, and can be used for stamping parts with high requirements on the quality or the dimensional accuracy of surface products in the shape of the groove of the stamping part;
(2) the male die is made of polyurethane material and has certain hardness, toughness and deformability, the outline of a groove on the male die is larger than that of a groove of the female die to be formed, the groove on the male die completely covers the groove on the female die, the part outside a fillet of the groove of the male die plays a role in pressing materials at the beginning, the material of the male die gradually deforms from outside to inside from the fillet part of the groove along with continuous descending, the plate is gradually pressed on the groove of the female die from the fillet part of the groove of the female die, the deformed male die quickly becomes a pressing area, the pressing area is continuously enlarged, the pressing force and the fillet of the groove of the female die limit the flow of the plate outside the fillet, and therefore the defect of the surface products caused by tangential compressive stress is fundamentally solved;
(3) the deformation of the plate is carried out from outside to inside, the plate outside the groove basically does not participate in the deformation, the plate at the central part is always subjected to plane bidirectional tensile stress and is the final forming area, and the position with the largest thinning rate is also the position. In the forming process, the plate participating in deformation is fully deformed, the thinning rate is gradually reduced from inside to outside, and the forming performance of the plate is improved, so that the plate is not easy to break by adopting the forming process in the invention under the same condition;
(4) under the action of force, the deformable male die and the plate synchronously deform without relative sliding, and the polyurethane material and the plate have high friction force, so that the surface quality of a product is ensured;
(5) the structure of the convex die formed by the controllable medium provides controllability in the deformation process, and the area between the outer contour of the convex die and the groove fillet of the convex die provides a pressing force in the initial deformation stage, so that the flow of materials outside the fillet can be effectively controlled.
Drawings
Fig. 1 is a schematic structural diagram of a mold structure in an embodiment of the present invention.
Fig. 2 is a schematic structural diagram of a drawing forming die in the prior art.
FIG. 3 is a state diagram of stress for a prior art drawn material.
Fig. 4 is a schematic structural diagram of a prior art hydraulic bulging die.
Fig. 5 is a diagram of a prior art material stress state of a hydroforming.
Fig. 6 is a schematic structural diagram of a controllable medium forming mold in an embodiment of the invention.
FIG. 7 is a diagram illustrating stress states of materials formed by the controllable medium according to an embodiment of the present invention.
Wherein the reference numerals are: 1. an upper base plate; 2. an exhaust hole; 3. a female die; 4. fixing a female die plate; 5. a plate material; 6. polyurethane male die; 7. a material pressing ring; 8. a male die support plate; 9. a lower base plate; 10. a support rod; 11. a limiting block; 12. a guide post; 13. and (4) guiding a sleeve. A. B, C, D four stress state points are respectively selected in sequence from outside to inside in the forming process.
Detailed Description
In order to clearly illustrate the technical features of the present solution, the present solution is described below by way of specific embodiments.
Referring to fig. 1, a controllable medium cold stamping forming process method includes the following steps:
step S1, in the preparation stage of the mold, the mold is provided with an upper mold and a lower mold, the upper mold is composed of an upper bottom plate 1, an exhaust hole 2, a female mold 3, a female mold fixing plate 4 and a guide sleeve 13, and the lower mold is composed of a polyurethane male mold 6, a material pressing plate 7, a male mold supporting plate 8, a lower bottom plate 9, a support rod 10, a limiting block 11 and a guide post 12. The female die 3 and the female die fixing plate 4 are tightly screwed on the upper base plate 1 through bolts, and the exhaust holes 2 are through holes in the female die 3 and the female die fixing plate 4 and used for exhausting air inside in the forming process. The male die supporting plate 8 is tightly fixed on the lower bottom plate 9 through a bolt, the polyurethane male die 6 is placed on the male die supporting plate 8, the material pressing ring 7 is connected with the support rod 10 through a bolt, the support rod 10 transmits pressure provided by a lower air cushion of the press to the material pressing ring 7, the material pressing ring 7 plays a role in supporting the plate material 5 and serves as a containing frame of the polyurethane male die 6, and the limiting block 11 limits the material pressing ring 7 to further move downwards when the die reaches a closed height so as to protect the die. The guide post 12 and the guide sleeve 13 provide a guiding function when the upper die and the lower die are contacted. The plate 5 is placed on the polyurethane male die 6 and the material pressing ring 7. The polyurethane male die 6 is a deformable male die made of polyurethane material, and a groove is formed on one side facing the plate to be formed. The female die 3 is made of rigid materials, grooves are formed in the female die 3, and the shapes of the grooves are consistent with those of products. The outline of the groove on the polyurethane male die 6 is larger than that of the groove on the female die 3, so that the polyurethane male die 6 can completely cover the female die 3 after die assembly. According to the invention, a closed groove means that the circumferential profile of the groove formed in the sheet is closed;
the upper die is fixed on an upper sliding block of the press through a bolt, and the lower die is fixedly arranged on a workbench of the press through a bolt;
the contour of the groove on the male die is larger than that of the groove on the female die 3 to be formed, and the groove on the male die completely covers the groove on the female die 3;
step S2: in the preparation stage, the material pressing ring 7 is jacked up to the working height by the support rod 10, and the material pressing ring 7 and the male die 6 support the forming plate 5;
step S3: in the pressing-down stage, the upper sliding block moves downwards, the female die 3 and the pressing ring 7 tightly press the plate 5 to provide enough pressing force, the plate 5 is tightly pressed on the polyurethane male die 6 and the pressing ring 7, and the pressing ring starts to move downwards under the action of the upper die along with the continuous downward movement of the upper sliding block;
the sheet 5 starts to deform under the action of the female die 3, the material pressing ring 7 and the male die 6;
step S4: in the deformation starting stage, as the polyurethane male die 6 has deformability, deformation starts at the inner edge part of the polyurethane male die 6, which is contacted with the plate 5, along with the continuous increase of pressure, the material of the male die gradually deforms from outside to inside from the fillet part of the groove and expands towards the inner side, the groove on the male die is gradually filled and raised, and the edge position of the polyurethane male die 6 is contacted with the plate 5 earlier than the inner part;
the polyurethane male die 6 gradually deforms and compresses the plate 5, and gradually reaches the groove fillet edge part of the female die 3;
step S5: in the deformation development stage, when the force transmitted by the deformed polyurethane male die 6 is large, the plate 5 starts to deform along the fillet of the female die 3 and gradually clings to the fillet of the female die 3, and because the force transmitted by the polyurethane male die 6 always compresses the plate 5 in the material thickness direction, radial tensile stress does not exist, the plate 5 outside the groove fillet of the female die 3 cannot flow into a closed groove to be formed;
step S6: in the later forming stage, along with the gradual deformation of the polyurethane male die 6, the deformed area of the polyurethane male die 6 becomes a pressing area, along with the continuous forming, the pressing area becomes larger continuously, and the plate 5 outside the to-be-formed closed groove fillet is difficult to flow into the closed groove under the effects of pressing force and fillet resistance; the plate 5 in the groove of the female die 3 slowly clings to the inner wall along the edge of the female die 3 under the action of the polyurethane male die 6;
step S7: and at the end of the deformation, the groove of the polyurethane male die 6 is filled with the self-deformed material and is protruded into the shape of the groove of the female die 3, the plate 5 to be deformed in the groove of the female die 3 is always in a state of plane bidirectional tensile stress in the whole forming process, the formed plate 5 is completely attached to the inner wall of the female die 3, and finally the shape of a closed groove is formed on the plate 5.
In step S1, the female die 3 is provided with a groove shape for the reverse forming groove shape, which is consistent with the shape of the product;
the male die 6 is provided with a groove shape for the reverse forming groove shape, and the groove profile of the male die is larger than that of the product.
In step S2, the sheet 5 in the groove is in a free state, and the sheet 5 is tensioned by the pressing force provided by the female die 3 and the pressing ring.
A deformable polyurethane male die 6 is arranged on the lower die, and a groove shape for guiding deformation is arranged on one side, facing the plate 5 to be formed, of the polyurethane male die 6;
the upper die is a rigid female die 3, the female die 3 is provided with a groove with the shape consistent with that of a product, and the size of the outer contour of the groove on the polyurethane male die 6 is larger than that of the outer contour of the groove on the female die 3.
The polyurethane male die 6 adopts polyurethane variable materials with certain hardness and toughness.
The hardness of the polyurethane is 80 to 95 Shore hardness.
The thickness of the polyurethane male die 6 is greater than or equal to 80mm, determined according to the specific product size.
The groove on the polyurethane male die 6 is arc-shaped, and the groove has no edge and is provided with a rounding.
The groove on the female die 3 is provided with an exhaust hole 2 at the bottom, and the diameter of the exhaust hole 2 is 4mm-6 mm.
The lapping surface of the polyurethane male die 6 and the material pressing ring is a plane or a curved surface.
Referring to fig. 2, 3, 4, 5, 6 and 7, to further illustrate the advantages of the present invention over the prior art, comparing the prior art draw forming process with the hydro-bulging process, the draw process: the male die is made of rigid materials, when the plate begins to deform, the bottom of the male die contacts the plate firstly, and along with descending of the male die, force acting on the plate at the bottom of the male die causes deformation of the plate by taking the contact point as the center. The forming force is transmitted to the plate outside the fillet through the force transmission area of the side wall, so that the area with the thinnest wall thickness of the part is on the side wall after final forming.
The hydraulic bulging process comprises the following steps: the male die is made of liquid materials, when the liquid is pressed, the internal pressure is equal everywhere, so that the force acting on the plate is also equal everywhere, and the wall thickness of the finally formed part is equal everywhere.
The controllable medium forming process comprises the following steps: the male die is made of polyurethane, the polyurethane has certain hardness and strength, when the male die is pressed to deform, the part contacting the plate deforms firstly, namely the plate at the round corner of the female die deforms firstly, the deformed plate is immediately attached to the rigid female die, the deformation continuously expands towards the inner part of the groove along with the continuous increase of the pressure, and the deformed polyurethane can limit the further flow of the plate under the action of pressing.
In the material forming process, A, B, C, D four stress state points are selected from the material from outside to inside in sequence for comparative analysis, and the detailed analysis is as follows:
(1) point A at the fillet of the female die
For the drawing process, force is transmitted to the plate through the rigid male die, and the unit cells are subjected to radial tensile stress and tangential compressive stress, because the plate enters the female die under the driving of the male die and the plate shrinks to generate compressive stress; the cell contacts the fillet of the concave die, so the cell is stressed in the material thickness direction;
for the hydraulic bulging process, the cells are also subjected to forces in three directions, but tensile stress is applied in the tangential direction, and the tensile stress is applied in the tangential direction because the plate is subjected to uniform pressure stress in the thickness direction and the plate needs to expand the area to be close to the female die;
for the controllable medium forming process, the unit cells are only subjected to compressive stress in the material thickness direction, and no stress exists in the radial direction and the tangential direction because the deformation of the plate material in the area is finished and the plate material is completely attached to the female die.
(2) Point B is located at the inner part of the fillet of the concave die
For the drawing process, the unit grids do not contact with the die, so that no stress exists in the material thickness direction, the radial direction is tensile stress, and the tangential direction is still compressive stress;
for the hydraulic bulging process, because the plate is always in contact with the male die, the stress still exists in three directions and is consistent with the position of the A point;
for the forming process of the controllable medium, the plate at the position of the B point just completes deformation, so that no stress exists in the tangential direction, but the plate is still subjected to slight tensile stress in the radial direction due to the position of the plate in a critical area of deformation, and the plate is subjected to compressive stress in the thickness direction.
(3) Point C, at a lower position than point B
For the drawing process, the stress state is consistent with the point B, only the tangential direction is changed from compressive stress to tensile stress, because in the tangential direction, the plate is drawn into the female die at the beginning, the plate is preferentially attached to the male die from the bottom of the male die gradually upwards, in the attaching process, the deformation of the plate is a process of shrinking and expanding from the center of the male die to a groove fillet, therefore, an area exists on the side wall, the tangential stress of the area is equal to 0, the tangential direction is the compressive stress outwards in the area, and the tangential direction is the tensile stress within the area;
for the hydraulic bulging process, the state is unchanged;
for the controllable medium forming process, the unit grids are at the moment of deformation, the plate material is gradually attached to the female die under the action of the male die, and the plate material is attached to the female die in a process of gradually changing from outside to inside without a process of first shrinking and then expanding of a drawing process, so that tensile stress is applied in the tangential direction and the radial direction, and compressive stress is applied in the material thickness direction.
(4) D, the position of the center of the bottom of the male die
For the drawing process, the bottom of the male die is contacted with the plate, the plate is subjected to tensile stress in the radial direction and the tangential direction, and the plate is subjected to compressive stress in the thickness direction;
for the hydraulic bulging process, the state is not changed and is consistent with the original state;
for the controllable medium forming process, because the concave shape of the male die is adopted, the unit grids do not contact with the die, so that no stress exists in the material thickness direction, tensile stress is applied in the tangential direction and the radial direction, and in the whole deformation process, the tensile stress is applied in the tangential direction and the radial direction of the part of the plate material.
In summary, the controllable medium forming process of the present invention is substantially different from the traditional drawing and hydraulic bulging processes, and the specific differences are as follows:
(a) the drawing process has very large radial tensile stress at the fillet of the groove, the hydraulic bulging process has the advantages that in the forming process, the plate always receives uniform compressive stress in the material thickness direction, the plate cannot flow into the fillet due to very large blank holder force, the controllable medium forming process is characterized in that the male die is made of polyurethane and has certain hardness and deformability, the contour of the groove on the male die is larger than that of the groove of the female die to be formed, the groove on the male die completely covers the groove on the female die, the part outside the fillet of the groove of the male die plays a role in material pressing at the beginning, the material of the male die gradually deforms from outside to inside along with continuous descending, the plate is gradually pressed on the groove of the female die from the fillet of the groove of the female die, the deformation of the plate is gradually realized, and the deformed male die immediately becomes a material pressing area, the pressing area is continuously enlarged in the whole forming process, and the pressing force and the concave die groove fillet limit the flow of the plate outside the fillet, so that the defect of the flour product caused by tangential pressure stress is fundamentally solved;
(b) for the drawing process, the side wall part in the sheet forming process plays a role in transferring forming force in the forming process and belongs to a force conduction area, the position with the largest thinning rate of a final product is at the side wall part and is a part easy to break, the bearing capacity of the sheet at the side wall position determines the maximum deformation degree of a drawing part, the sheet at the central position is firstly contacted with a male die, and due to the use of friction, the sheet at the central part is not easy to flow, so that the thinning rate is smaller, and the thinning rate distribution of final parts is very uneven; for the hydraulic bulging process, all positions of the plate are always stressed in the same state, so that the thickness of the formed part of the plate is always uniform;
for the forming process of the controllable medium, the deformation of the plate is carried out from outside to inside, the plate outside the groove basically does not participate in the deformation, the plate at the central part is always subjected to plane bidirectional tensile stress, and the plate is the final forming area, and the position with the largest thinning rate is also the position. In the forming process, the plate 5 participating in deformation is fully deformed, the thinning rate is gradually reduced from inside to outside, and the forming performance of the plate is improved, so that the plate is less prone to fracture when a controllable medium forming process is adopted under the same conditions.
(c) When the drawing process is used for forming, the plate and the male and female dies slide relatively, which is a condition that a product can be finally formed, so that the influence of friction force is fully considered during drawing and forming, generally, the friction force between the rigid male and female dies and the plate is small, and the plate can smoothly flow under the action of the male and female dies; when the hydraulic bulging process is used for forming, the friction force between the plate and the liquid material is basically avoided;
when the controllable medium is formed, the deformable male die and the plate synchronously deform under the action of force without relative sliding, and the polyurethane material and the plate have large friction force.
(d) For the drawing process, the plate material at the central part of the plate material participating in deformation preferentially contacts the bottom of the male die, the deformation of the plate material is started from the central part and then gradually expands to the outside, the deformed plate material is gradually attached to the male die from the bottom of the male die upwards until the die is closed, and the plate material is completely attached to the male die, so that the whole process is a deformation process from inside to outside; for the hydraulic bulging process, the plate materials participating in deformation always contact the liquid male die, and due to the fact that the pressure intensity of the liquid male die is equal everywhere, the pressure stress applied in the material thickness direction is also equal everywhere, so that the deformation of the plate materials starts to be deformed at the same time, and no sequence exists; for the controllable medium forming process, due to the shape of the groove on the male die, under the action of force, the material at the round corner of the groove of the male die is preferentially deformed, so that the plate is forced to be attached to the round corner of the groove of the female die, the depth of the groove of the male die is gradually reduced along with the continuous deformation of the male die, and the plate is slowly changed into a convex state.
(e) Compared with a drawing process and a controllable medium forming process, the stress state of the central part of the plate material is different, and for the drawing process, the central part is in contact with the center of a male die to be stressed so as to pull the surrounding material to flow into the groove; the controllable medium is formed differently, the plate material at the central part is subjected to outward tensile stress, and the central material flows to the outside, which is different from the deformation path of the traditional process.
The structure of the convex die formed by the controllable medium provides controllability in the deformation process, and the area between the outer contour of the convex die and the fillet of the concave groove of the convex die provides a pressing force in the initial deformation stage, so that the flow of materials outside the fillet can be effectively controlled; the shape and depth of the concave groove of the male die are determined according to the shape of a product, and under different shapes and depths of the concave groove, the deformation paths of the male die under the action of pressure are different, so that the deformation paths of the plate are different, namely the distribution of the thinning rate is different on the final part, and the forming mode is controllable.
The specific working process of the invention is as follows:
the die comprises an upper die and a lower die, wherein the upper die comprises an upper bottom plate 1, an exhaust hole 2, a female die 3, a female die fixing plate 4 and a guide sleeve 13, and the lower die comprises a polyurethane male die 6, a pressure plate 7, a male die supporting plate 8, a lower bottom plate 9, a support rod 10, a limiting block 11 and a guide pillar 12. The female die 3 and the female die fixing plate 4 are fastened on the upper base plate 1 through bolts, and the exhaust holes 2 are through holes in the female die 3 and the female die fixing plate 4 and used for exhausting air inside in the forming process. The male die supporting plate 8 is fastened on the lower bottom plate 9 through bolts, the polyurethane male die 6 is placed on the male die supporting plate 8, the material pressing ring 7 is connected with the support rod 10 through bolts, the support rod 10 transmits pressure provided by a lower air cushion of the press to the material pressing ring 7, the material pressing ring 7 plays a role in supporting the plate material 5 and serves as a containing frame of the polyurethane male die 6, and the limiting block 11 limits the material pressing ring 7 to further move downwards when the die reaches a closed height so as to protect the die. The guide post 12 and the guide sleeve 13 provide a guiding function when the upper die and the lower die are contacted. The plate 5 is placed on the polyurethane male die 6 and the material pressing ring 7. The polyurethane male die 6 is a deformable male die made of polyurethane material, and a groove is formed on one side facing the plate to be formed. The female die 3 is made of rigid materials, grooves are formed in the female die 3, and the shapes of the grooves are consistent with those of products. The outline of the groove on the polyurethane male die 6 is larger than that of the groove on the female die 3, so that the polyurethane male die 6 can completely cover the female die 3 after die assembly. According to the invention, a closed groove means that the circumferential profile of the groove formed in the sheet is closed.
Firstly, a plate 5 is placed on a polyurethane male die 6 and a material pressing ring 7, when a press starts to move, an upper die moves downwards along with a press sliding block, and a guide post 12 is combined with a guide sleeve 13 and plays a role in guiding; when the female die 3 descends to a certain stage, the female die 3 is in contact with the sheet material 5, and the sheet material 5 is tightly pressed on the polyurethane male die 6 and the pressing ring 7, so that the pressing effect is achieved, along with the continuous descending of the female die 3, the pressing ring 7 starts to descend under the action of the female die 3, due to the fact that the polyurethane male die 6 has deformability, deformation starts at the inner edge part of the polyurethane male die 6, which is in contact with the sheet material, along with the continuous increase of pressure, the deformation gradually expands towards the inner side, the groove is gradually filled and leveled and protrudes, and due to the shape, the edge position of the polyurethane male die 6 can be in contact with the sheet material 5 earlier than the inner part.
When the polyurethane male die 6 deforms gradually to press the plate 5 and gradually reaches the edge of the groove fillet of the female die 3, because the plate at the position is not supported by the female die 3, if the force transmitted by the deformed polyurethane male die 6 is large enough, the plate 5 starts to deform along the fillet of the female die 3 and gradually clings to the fillet of the female die 3, and along with the gradual deformation of the polyurethane male die 6, the plate can slowly cling to the inner wall along the edge of the female die 3 under the action of the polyurethane male die 6.
And finally, the groove of the polyurethane male die 6 is filled by the self-deformed material and is protruded into the shape of the groove of the female die 3, the plate 5 is completely attached to the inner wall of the female die 3, and then the shape of a closed groove is formed on the plate finally.
When the forming starts, the plate 5 only deforms along the fillet of the female die 3 and slowly clings to the fillet, the plate 5 is pressed in the thickness direction by the force transmitted by the polyurethane male die 6, and radial tensile stress does not exist, so that the plate does not flow into a closed groove to be formed, and the problems of tangential compressive stress and plate flowing around the closed groove are solved; in the later forming process, the plate is slowly formed into a product shape along with the deformation of the polyurethane male die 6, the plate without deformation is always in a plane bidirectional tensile stress state, the forming mode is completely different from the deformation path of the existing forming process, and the groove shape of the polyurethane male die 6 plays an important role in the whole forming process and can play a role in adjusting the plate thinning rate, so the forming process is called as a controllable medium forming process. The deformed area of the polyurethane male die 6 becomes a pressing area, which plays a pressing role, and the pressing area is continuously enlarged along with the continuous forming.
According to the invention, the plate outside the round corner of the closed groove to be formed is difficult to flow into the closed groove under the action of the pressing force and the round corner resistance, so the invention fundamentally solves the problems of generating tangential pressure stress and plate flowing outside the round corner of the closed groove, solves the problem of surface product defects around the groove of a product, reduces the research and preparation workload in the manufacture of a mould, shortens the manufacturing period, and has the advantages of simple structure, convenient manufacture, stable pressing, convenient maintenance and the like.
The technical features of the present invention which are not described in the above embodiments may be implemented by or using the prior art, and are not described herein again, of course, the above description is not intended to limit the present invention, and the present invention is not limited to the above examples, and variations, modifications, additions or substitutions which may be made by those skilled in the art within the spirit and scope of the present invention should also fall within the protection scope of the present invention.
Claims (10)
1. A controllable medium cold stamping forming process method is characterized by comprising the following steps:
step S1, in the mold preparation stage, an upper mold is fixed on an upper sliding block of a press through bolts, the upper mold is a female mold, a lower mold is composed of a material pressing ring and a deformable polyurethane male mold, a groove is formed in the male mold, and the lower mold is fixed on a workbench of the press through bolts;
the contour of the groove on the male die is larger than that of the groove of the female die to be formed, and the groove on the male die completely covers the groove on the female die;
step S2: in the preparation stage, the material pressing ring is jacked to the working height by the support rod, and the material pressing ring and the male die support the forming plate;
step S3: in the pressing-down stage, the upper sliding block moves downwards, the upper die and the pressing ring compress the plate material to provide enough pressing force, the plate material is compressed on the polyurethane male die and the pressing ring, and the pressing ring starts to move downwards under the action of the upper die along with the continuous downward movement of the upper sliding block;
the plate begins to deform under the action of the upper die, the material pressing ring and the male die;
step S4: in the deformation starting stage, as the polyurethane male die has deformability, deformation is started at the inner edge part of the polyurethane male die, which is contacted with the plate material, along with the continuous increase of pressure, the material of the male die gradually deforms from outside to inside from the fillet part of the groove and expands towards the inner side, the groove on the male die is gradually filled and leveled and bulges, and the edge position of the polyurethane male die is contacted with the plate material earlier than the inner part;
the polyurethane male die gradually deforms and compresses the plate material, and the plate material gradually reaches the groove fillet edge part of the female die;
step S5: in the deformation development stage, when the force transmitted by the deformed polyurethane male die is large, the plate begins to deform along the fillet of the female die and gradually clings to the fillet of the female die, and the plate is pressed in the thickness direction all the time by the force transmitted by the polyurethane male die without radial tensile stress, so that the plate outside the fillet of the female die groove cannot flow into a closed groove to be formed;
step S6: in the later forming stage, along with the gradual deformation of the polyurethane male die, the deformed area of the polyurethane male die becomes a pressing area, along with the continuous forming, the pressing area becomes larger continuously, the plate outside the to-be-formed closed groove fillet is difficult to flow into the closed groove under the effects of pressing force and fillet resistance, and the plate in the concave groove slowly leans against the inner wall along the edge of the concave die under the effect of the polyurethane male die;
step S7: and at the end of the deformation, the groove of the polyurethane male die is filled with the self-deformed material and is protruded into the shape of the groove of the female die, in the whole forming process, the plate to be deformed in the groove of the female die is always in a state of plane bidirectional tensile stress, the formed plate is completely attached to the inner wall of the female die, and finally the shape of a closed groove is formed on the plate.
2. The controlled medium cold stamping forming process method according to claim 1, wherein in step S1, the upper die is provided with a shape of a reverse forming groove, which is consistent with the shape of the product;
the male die is provided with a groove shape for reversely forming the groove shape, and the groove profile of the male die is larger than that of a product.
3. The controlled medium cold stamping forming process method according to claim 2, wherein in the step S2, the sheet material in the groove is in a free state, and the sheet material is only compressed by the pressing force provided by the upper die and the pressing ring.
4. A controllable medium cold stamping forming die structure comprises an upper die and a lower die, and is characterized in that a deformable polyurethane male die is arranged on the lower die, and a groove shape for guiding deformation is arranged on one side, facing a plate to be formed, of the polyurethane male die;
the upper die is a rigid female die, a groove with the shape consistent with that of a product is arranged on the female die, and the size of the outer contour of the groove on the polyurethane male die is larger than that of the outer contour of the groove on the female die.
5. The controllable medium cold stamping die structure according to claim 4, wherein the polyurethane male die is made of a polyurethane deformable material;
and a material pressing ring is arranged on the outer frame of the polyurethane male die.
6. The controlled media cold press formed die structure of claim 5, wherein the polyurethane has a hardness of 80-95 Shore.
7. The controlled media cold stamping die structure of claim 6, wherein the polyurethane male die has a thickness greater than or equal to 80 mm.
8. The controlled media cold stamping die structure as recited in claim 7, wherein the polyurethane male die has a circular arc-shaped groove, and the groove has no edges and is provided with a radius.
9. The controlled media cold stamping and forming die structure as recited in claim 8, wherein the recess of the female die has vent holes at the bottom thereof, the vent holes having a diameter of 4mm to 6 mm.
10. The controllable medium cold stamping die structure as claimed in claim 9, wherein the overlapping surface of the polyurethane male die and the material pressing ring is a plane or a curved surface.
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| CN111151624B (en) * | 2020-01-09 | 2021-08-27 | 贵州永红航空机械有限责任公司 | Flexible forming device and method for sealing cone |
| CN113070400A (en) * | 2021-03-25 | 2021-07-06 | 中国航发南方工业有限公司 | Thin-wall conical part punch forming die |
| CN114505432B (en) * | 2022-02-24 | 2024-05-14 | 漳州锐腾电器有限公司 | Pier extrusion die capable of changing section width of stamping part and pier extrusion precision cutting process |
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