CN113084006B

CN113084006B - Step extrusion method for effectively reducing box body forming load

Info

Publication number: CN113084006B
Application number: CN202110361365.7A
Authority: CN
Inventors: 徐健; 张治民; 张慧芳; 穆崇礼; 韩瑞
Original assignee: North University of China
Current assignee: North University of China
Priority date: 2021-04-02
Filing date: 2021-04-02
Publication date: 2023-04-25
Anticipated expiration: 2041-04-02
Also published as: CN113084006A

Abstract

The invention discloses a step extrusion method for effectively reducing the forming load of a box body, which comprises the following steps: 1. analyzing and preliminarily determining extrusion characteristics and dimensions of the box body, wherein the extrusion characteristics comprise shape and position of an internal cavity, an extrusion process and an extrusion procedure, and preliminarily splitting the box body structure into a front cavity and a rear cavity; 2. simultaneously presetting a maximum extrusion load through UG modeling, judging whether the preliminary splitting mode of each cavity is proper or not through the extrusion load data and the maximum extrusion load of a simulation test, further splitting extrusion forming characteristics of the cavities with the excessive values, and reasonably arranging and modifying again; 3. determining a split mode of step-by-step extrusion; 4. and repeating the second and third steps until an optimal extrusion design scheme is determined. The problem of excessive load in the extrusion forming process of the box body is solved, the step-by-step extrusion process is reasonably designed, and the purposes of reducing the load and effectively forming are achieved.

Description

Step extrusion method for effectively reducing box body forming load

Technical Field

The invention belongs to the technical field of die extrusion forming, and particularly relates to a step-by-step extrusion method for effectively reducing forming load of a box body.

Background

Along with the requirements of energy conservation and emission reduction, the light alloy of the magnesium alloy series is widely applied in production and life, and particularly has obvious effect in the industries of automobile manufacturing, transportation and the like. With the development of production technology, the light-weight replacement of small parts cannot meet the actual production activity demands of people, and more large-size parts start to be explored in light-weight. For the large-size forming target, the realization of light weight and the application have important economic value in the aspects of energy conservation and emission reduction, but the excessive forming load caused by the oversized blank is always a difficult problem in the extrusion forming process.

The box body has the characteristics of complex structure, large size and the like, and cannot be perfectly formed at one time under the limited technical conditions, wherein the forming load is the most important. In addition, the repeated forming of the box body consumes a great deal of manpower and material resources, and brings unnecessary trouble to actual production and processing. The step extrusion die for effectively and practically reducing the forming load of the large-sized box body is urgently required to be put forward by combining the structural characteristics of the box body and the practical requirements of load reduction forming and rapid production.

Disclosure of Invention

The invention aims to provide a step-by-step extrusion method for effectively reducing the forming load of a box body, solves the problem of overlarge load in the extrusion forming process of the box body, and reasonably designs a step-by-step extrusion process in a numerical simulation mode so as to achieve the purposes of reducing the load and effectively forming.

To achieve the above object, the solution of the present invention is: a step extrusion method for effectively reducing the forming load of a box body comprises the following steps:

firstly, analyzing and preliminarily determining extrusion characteristics and dimensions of a box body, wherein the extrusion characteristics comprise shape and position of an internal cavity, an extrusion process and an extrusion procedure, the box body structure is firstly preliminarily split into a front cavity and a rear cavity, the extrusion process is preliminarily determined to be forward extrusion according to the shape of each cavity, and the extrusion procedure is sequentially formed according to the front cavity and the rear cavity;

the front cavity comprises a vertical cavity, a left U-shaped cavity, a right U-shaped cavity and a dumbbell-shaped cavity, the front end of the vertical cavity is provided with an opening at the front surface, the left U-shaped cavity and the right U-shaped cavity are respectively positioned at the left side and the right side of the front end of the vertical cavity, and the dumbbell-shaped cavity is coaxially positioned at the rear sides of the left U-shaped cavity and the right U-shaped cavity; the rear cavity comprises a wide cavity and a strip cavity, the wide cavity spans the rear side of the dumbbell-shaped cavity, and the strip cavity spans the rear side of the wide cavity and exceeds the left end and the right end of the wide cavity; semicircular grooves are coaxially formed in the cavity walls between each cavity and the adjacent cavity and in the front end face and the rear end face of the box body;

the step-by-step extrusion die comprises an upper die plate connected with the upper press machine, a lower die plate connected with the lower press machine, a male die assembly which can be detached from the upper die plate, a female die and a push rod which are arranged on the lower die plate;

the male die assembly comprises an insert corresponding to each cavity of the front cavity and the rear cavity, a backing plate connected below the upper die plate and a T-shaped groove bolt; the front and the side of the backing plate are provided with T-shaped grooves for placing T-shaped groove bolts, and the tail ends of the T-shaped groove bolts are connected with the insert in a threaded fit manner; the female die is provided with an inner cavity for placing the box blank below the male die component, the middle of the bottom of the inner cavity is provided with an ejection hole, and the size of the ejection hole is matched with that of the ejector rod;

step two, modeling and carrying out a simulation experiment, combining the extrusion characteristics and the dimensions, designing the dimensions of a step extrusion die through UG modeling, simultaneously presetting the maximum extrusion load meeting the forming requirement, then carrying out an extrusion simulation experiment, judging whether the preliminary splitting mode of each cavity is suitable or not through extrusion load data and the maximum extrusion load of the simulation experiment, and judging whether the preset maximum extrusion load is suitable or not and the preset maximum extrusion load is unsuitable; if the method is suitable, the next step is carried out, if the method is unsuitable, the extrusion forming characteristics of the die cavity exceeding the preset maximum extrusion load are further split, reasonable arrangement and modification are carried out again, modeling is carried out again after the modification is finished, a simulation experiment is carried out, the split mode after the modification is judged to be suitable, and until the structure is judged to be suitable;

step three, determining a split mode of step-by-step extrusion;

and fourthly, repeating the second operation and the third operation until the optimal extrusion design scheme is determined.

Further, the bottoms of the lower die plate and the female die are outwards diverged and uniformly distributed with the ejection holes as circle centers, and the mounting holes are used for mounting bolts to connect the lower die plate and the female die.

Further, the periphery of the insert is provided with a pattern drawing angle.

The invention effectively realizes the purpose of reducing the extrusion forming load of the box body in a step-by-step extrusion mode. By analyzing the complex box body characteristics, the forming part is effectively split, so that the aim of reducing the load is fulfilled. And the finite element simulation analysis technology is combined to realize the optimization of the step-by-step extrusion mode, and whether the step-by-step extrusion mode is reasonable or not is judged according to the simulation result. And if the extrusion conditions are not met, the extrusion part is split, so that the load is reduced, and the process is repeated until a proper extrusion mode is designed. The method combines the characteristics of a method for reducing forming load by step extrusion, and adopts a detachable pin structure for fixing an insert and an upper template. After extrusion is completed, the insert is disassembled and placed into a forming cavity, and then the next extrusion work is performed. The invention is suitable for solving the problem of overlarge load in extrusion forming of large-size blanks. The invention has the beneficial effects that:

(1) Effectively reduce load: the step extrusion design of the invention considers the extrusion forming characteristics and mode characteristics of the box body, reasonably separates a plurality of preformed cavities and effectively reduces forming load. The multi-step extrusion is used for replacing the one-step extrusion mode, so that the extrusion requirements of balanced stress and perfect forming are met.

(2) Economy: according to the invention, through a finite element simulation technology, the practical production condition is verified and continuously optimized in a modeling and simulation mode, so that the forming difficulty in the practical production process is avoided, and unnecessary waste is effectively reduced.

(3) High efficiency: the invention combines a step-by-step extrusion mode with the placement of the backing plate, and the die realizes that after the extrusion of each step of die cavity is finished by a detachable structure, the insert is taken as a cushion block to be placed in the die cavity. In actual processing production, the concept saves complex disassembly and assembly steps in the production process and realizes quick production.

(4) And (3) performing perfect forming: the step extrusion forming is designed in a mode of adjacent continuous division, and the forming of adjacent cavities is continuous, so that the influence of the subsequent cavity forming on the formed cavities is reduced in a step mode.

Drawings

Fig. 1 is a schematic structural diagram of a target box according to a first embodiment of the present invention;

FIG. 2 is a front view of a mold structure according to a first embodiment of the present invention;

FIG. 3 isbase:Sub>A cross-sectional view taken along line A-A of FIG. 2;

FIG. 4 is a top view of a mold according to a first embodiment of the invention;

FIG. 5 is a schematic view of a lower template according to an embodiment of the present invention;

FIG. 6 is an insert elevation view of a vertical cavity according to an embodiment of the present invention;

FIG. 7 is a top view of an insert of a vertical cavity according to an embodiment of the present invention;

FIG. 8 is a cross-sectional view taken along B-B of FIG. 6;

FIG. 9 is a front view of an insert of a left and right U-shaped cavity in accordance with an embodiment of the present invention;

FIG. 10 is a top view of an insert of a left and right U-shaped cavity according to an embodiment of the present invention;

FIG. 11 is a cross-sectional view taken along line C-C of FIG. 9;

FIG. 12 is an elevation view of an insert of a dumbbell-shaped cavity in accordance with embodiments of the invention;

FIG. 13 is a top view of an insert of a dumbbell-shaped cavity according to embodiments of the invention;

FIG. 14 is an elevation view of an insert of a wide cavity in accordance with an embodiment of the present invention;

FIG. 15 is a top view of an insert with a wide cavity in accordance with an embodiment of the present invention;

FIG. 16 is an elevation view of an insert of an elongated cavity according to an embodiment of the present invention;

FIG. 17 is a top view of an insert of an elongated cavity according to an embodiment of the present invention;

FIG. 18 is a front view of a backing plate in accordance with an embodiment of the present invention;

FIG. 19 is a top view of a backing plate according to an embodiment of the invention;

FIG. 20 is a cross-sectional view taken along D-D of FIG. 18;

FIG. 21 is a front view of a pin according to an embodiment of the present invention;

FIG. 22 is a top view of a pin according to an embodiment of the present invention;

FIG. 23 is a sequence diagram of a one-step extrusion process in accordance with an embodiment of the present invention;

fig. 24 is a flow chart illustrating a step-wise extrusion method according to an embodiment of the present invention in a large-scale box extrusion process.

Description of the reference numerals:

a front cavity 1, a vertical cavity 11, a left U-shaped cavity 12, a right U-shaped cavity 13, a dumbbell-shaped cavity 14, a rear cavity 2, a wide cavity 21, a strip cavity 22, a semicircular groove 3, an upper die plate 4, a male die assembly 5, an insert 51, a backing plate 52, T-shaped groove bolts 53, a lower die plate 6, a female die 7 and a push rod 8.

Detailed Description

The invention will be described in detail with reference to the accompanying drawings and specific embodiments.

The invention relates to a step-by-step extrusion method for effectively reducing the forming load of a box body, which comprises the following steps:

firstly, analyzing and preliminarily determining extrusion characteristics and dimensions of a box body, wherein the extrusion characteristics comprise shape positions of internal cavities, an extrusion process and an extrusion procedure, the shapes of the whole internal cavities are firstly preliminarily split into cavity shapes at a plurality of different positions, the extrusion process is preliminarily determined according to the shapes of all the cavities, and the extrusion procedure is preliminarily determined according to the position sequence of all the cavities;

step two, modeling, performing simulation experiments, combining extrusion characteristics and sizes, designing the sizes of a female die 7 and a male die through UG modeling, simultaneously presetting the maximum extrusion load meeting the forming requirement, performing extrusion simulation experiments, judging whether the preliminary splitting mode of each cavity is proper or not through extrusion load data and the maximum extrusion load of the simulation experiments, if so, performing the next step, if not, further splitting the extrusion forming characteristics of the cavity exceeding the preset maximum extrusion load, reasonably arranging and modifying again, performing simulation experiments again after modification, judging whether the splitting mode after modification is proper or not, and judging whether the splitting mode after modification is proper or not;

step three, determining a split mode of step-by-step extrusion;

step four, repeating the operations of step two and step three until an optimal extrusion design scheme is determined, and referring to fig. 23.

In this embodiment, a box structure with a complex internal cavity structure is designed according to the method provided above, the target box structure is shown in fig. 1, the box structure is divided into a front cavity 1 and a rear cavity 2,

the front cavity 1 comprises a vertical cavity 11, a left U-shaped cavity 12, a right U-shaped cavity 13 and a dumbbell-shaped cavity 14, wherein the front end of the vertical cavity 11 is open at the front, the left U-shaped cavity 12 and the right U-shaped cavity 13 are respectively positioned at the left side and the right side of the front end of the vertical cavity 11, and the dumbbell-shaped cavity 14 is coaxially positioned at the rear sides of the left U-shaped cavity 12 and the right U-shaped cavity 13;

the rear cavity 2 comprises a wide cavity 21 and a strip cavity 22, the wide cavity 21 spans the rear side of the dumbbell-shaped cavity 14, and the strip cavity 22 spans the rear side of the wide cavity 21 and extends beyond the left end and the right end of the wide cavity 21;

semicircular grooves 3 are coaxially formed in the cavity walls between each cavity and the adjacent cavity and in the front end face and the rear end face of the box body.

In order to realize the design of the forming die of the box body, the specific steps are as follows:

step one, analyzing and preliminarily determining extrusion characteristics and dimensions of the box body, wherein the extrusion characteristics and dimensions can be preliminarily split into the following cavity parts: the method comprises the steps of firstly, determining a front cavity 1 and a rear cavity 2 as positive extrusion by a preliminary extrusion process, and forming the front cavity 1 and the rear cavity 2 in sequence in the preliminary extrusion process;

modeling to perform simulation experiments, designing the size of a die through UG modeling by combining the extrusion characteristics and the size, and presetting the maximum extrusion load meeting the forming requirement;

the invention provides a step-by-step extrusion die capable of effectively reducing the forming load of a box body, which is combined with figures 1 to 5, and comprises an upper die plate 4 connected with an upper press machine, a lower die plate 6 connected with a lower press machine, a male die assembly 5 which can be detached from the upper die plate 4, a female die 7 and a push rod 8 which are arranged on the lower die plate 6;

figures 1, 2, in combination with figures 6 to 22, the punch assembly 5 comprises an insert 51 corresponding to each of the front and

rear cavities

1, 2, a backing plate 52 connected below the upper die plate 4, and a T-slot bolt 53; the front and side edges of the backing plate 52 are provided with T-shaped grooves for placing T-shaped groove bolts 53, and the tail ends of the T-shaped groove bolts 53 are connected with the insert 51 in a threaded fit manner, so that the disassembly is convenient; the upper template 4 and the backing plate 52 are fixed by inner hexagon bolts; the female die 7 is provided with an inner cavity for placing a box blank below the male die assembly 5, the middle of the bottom of the inner cavity is provided with an ejection hole, and the size of the ejection hole is matched with that of the ejector rod 8; the bottoms of the lower die plate 6 and the female die 7 are outwards diverged and uniformly distributed with the ejection holes as circle centers, and the mounting holes are used for mounting bolts to connect the lower die plate 6 and the female die 7.

The periphery of the insert 51 is provided with a certain drawing angle, so that the demolding after the extrusion is finished is facilitated.

The connection structure of the insert 51 and the backing plate 52 is designed to be a detachable structure for reasonable arrangement, after extrusion is completed, the insert 51 can be detached to be placed in a formed cavity to serve as a cushion block, the follow-up extrusion action is prevented from damaging the formed cavity, interference reaction caused by the next extrusion operation is avoided, and the forming effect is effectively ensured.

After the insert 51 connected by the T-shaped groove bolt 53 slides into the T-shaped groove of the backing plate 52, the slide of the insert 51 in the T-shaped groove is limited by the cylindrical pins which can be split into three parts, as shown in fig. 20 and 22, the connecting function is realized by mutually matching, and the matched cylindrical pins are rotated by 90 degrees so as to achieve the purpose of fixing the insert 51 and the backing plate 52.

The backing plate 52 is provided with "T-shaped" slots on the sides and front for attachment of T-slot bolts 53, taking into account the constructional features of the extrusion machine: the side of the extruder is provided with a lifting rod which is inconvenient to operate, after the extrusion work of the

front cavities

11, 12 and 13 of the box body is completed, the T-shaped groove bolts 53 are pulled out, the detached insert 51 is placed into the formed cavity, the whole die is rotated by 90 degrees anticlockwise, the T-shaped groove on the side surface of the backing plate 52 faces the front surface of the machine, and the next extrusion step is smoothly carried out;

extrusion simulation parameter setting: the temperature of the blank is 450 ℃, the material and the attribute of the blank are rare earth magnesium alloy and plastomer, and the grid number is 50000; the male die assembly 5 is a rigid body, the temperature is 450 ℃, the extrusion speed is 0.6mm/sec, and the pressing depth is 145mm; the die 7 and the backing plate 52 are rigid bodies, and the temperature is 450 ℃. The extrusion conditions were that the maximum extrusion load was not more than 3000T, the reserved subsequent machining allowance was 3mm, and the effective working height of the insert 51 was 155mm in consideration of the blank surface leveling and machining allowance. Then, the STL format is exported, parameters are set in software Deforman, extrusion simulation test is conducted, extrusion load data and maximum extrusion load of the simulation test are used for judging, whether a preliminary splitting mode of each cavity is proper or not is judged, if yes, the next step is carried out, if not, extrusion forming characteristics of the cavities exceeding the preset maximum extrusion load are further split, reasonable arrangement and modification are conducted again, modeling is conducted again after modification is completed, whether the modified splitting mode is proper is judged, and until the judging result is proper;

step three, determining a split mode of step-by-step extrusion, extruding and forming the integral die cavity, and performing a first step of trial, and combining extrusion conditions and forming requirements: the tank is formed more perfectly within the requirement of a maximum crush load of 3000T. Under the set extrusion conditions and the pressing depth requirements, although the surface of the blank is subjected to the extrusion force, the contact area of the male die and the blank is too large, so that the extrusion load is rapidly increased, the rated load is reached in a short time, and the forming depth of the die cavity cannot meet the expected requirements.

And fourthly, repeating the second operation and the third operation until the optimal extrusion design scheme is determined. Under the set pressing depth requirement, the extrusion molding divided into the front cavity 1 and the rear cavity 2 is not capable of meeting the actual production conditions although the pressing load is reduced to a certain extent. Because the gap between the dumbbell-shaped cavity 14 and the left and right U-shaped cavities is too small, the metal flows faster than other positions, so that the metal contacts the backing plate 52 too early, the load rises quickly, and as a result, the load reaches the production requirement when the insert 51 is not pressed down to a given position, and therefore, the load is further optimized;

repeating the second and third steps again, dividing the front cavity 1 and the rear cavity 2 which are preliminarily divided again, dividing the front cavity 1 into a vertical cavity 11, a left U-shaped cavity 12, a right U-shaped cavity 13 and a dumbbell-shaped cavity 14, dividing the rear cavity 2 into a wide cavity 21 and a long cavity 22, and finally processing the semicircular groove 3. In addition, to ensure that the forming effect restricts the billet flow, the extrusion sequence is determined: the vertical cavity 11, the left U-shaped cavity 12, the right U-shaped cavity 13, the dumbbell-shaped cavity 14, the wide cavity 21, the long cavity 22 and the semicircular groove 3 are used for intuitively reflecting the design thought of the invention and facilitating understanding, and the specific flow is shown in the figure 24. In such a step-by-step extrusion mode, the extrusion operation can be completed under the pressure condition of 3000T. There are still some disadvantages in the shaping requirements, with the shape modification of the insert 51 to optimize the metal flow orientation for further shaping optimization. But for the wide cavity 21, the large contact area makes the lower load excessive and it is difficult to reduce the load by modifying the shape of the insert 51. For the wide cavity 21, the problem of reducing the load by modifying the shape of the insert 51 is difficult, in which case the step extrusion method is particularly important;

and repeating the second and third steps again, and avoiding mutual interference in cavity forming in consideration of forming effect, so that machining allowance is reserved between the cavities. Finally, the semicircular groove 3 is extruded, and the situation of overlarge load also occurs. Since the semicircular groove 3 is formed on the cavity wall of the box body, the lower surface of the backing plate 52 is contacted with the blank which is formed in the pressing process, so that the load is overlarge;

and repeating the second and third steps, and dividing the semicircular groove 3 into a front cavity and a rear cavity for extrusion forming, and correspondingly placing the formed insert 51 into the formed cavity before extrusion of the semicircular groove 3, so as to avoid damaging the integrity of the finished cavity.

By integrating the steps, the invention adopts a step extrusion method to effectively reduce extrusion forming load. Dividing the characteristics to be extruded and formed, verifying whether the dividing mode meets the production requirement through modeling and simulation means to judge the rationality of the dividing mode, if not, dividing again to reduce the load to meet the forming requirement, and finally determining the most complete forming mode.

The extrusion process of the front cavity 1 has forming incompleteness, leaves forming allowance at the part difficult to form, and combines the backing plate 52 to limit metal flow, thereby achieving the purpose of perfect forming. The ear plate structures on the two sides of the box body wide cavity 21 belong to difficult-to-shape areas for the back extrusion mode, and the ear plate forming is realized by guiding metal flow in a mode of placing limiting blocks at the two most side positions of the concave die strip cavity 22.

In addition, the operation problem brought by the die structure in the production and processing process is supplemented. The insert 51 and the backing plate 52 are mounted by T-slot bolts 53, the "T" slots of the vertical cavity 11, the left U-shaped cavity 12, the right U-shaped cavity 13 are open at the front of the backing plate 52, and the "T" slots of the remaining cavities are open at the sides of the backing plate 52. After the extrusion of the vertical cavity 11, the left U-shaped cavity 12 and the right U-shaped cavity 13 is completed, the whole die is required to rotate anticlockwise by 90 degrees and then the subsequent extrusion work is required. The removed insert 51 is placed into the formed cavity as in the simulation. The detachable pin structure is as shown in fig. 21 and 22, the detachable cylindrical pins are respectively inserted into and detached from the insert 51 and the backing plate 52 to fix the insert and the backing plate, the insert and the backing plate are rotated by 90 degrees after connection to complete fixing operation, the detachable pin is rotated by 90 degrees after extrusion is completed to be taken out, and then the T-shaped groove bolt 53 is pulled out to be detached. After all extrusion work is completed, the ejector rod 8 at the bottom ejects the formed piece to carry out demoulding, and the formed blank is taken out.

The above embodiments are only preferred embodiments of the present invention, and are not limited to the present invention, and all equivalent changes made according to the design key of the present invention fall within the protection scope of the present invention.

Claims

1. A step extrusion method for effectively reducing the forming load of a box body is characterized by comprising the following steps of: the method comprises the following steps:

the male die assembly comprises an insert corresponding to each cavity of the front cavity and the rear cavity, a backing plate connected below the upper die plate and a T-shaped groove bolt; the connecting structure of the insert and the backing plate is designed into a detachable structure, and after extrusion is finished, the insert can be detached and placed in a formed cavity to serve as a cushion block; the front and the side of the backing plate are provided with T-shaped grooves for placing T-shaped groove bolts, and the tail ends of the T-shaped groove bolts are connected with the insert in a threaded fit manner; the female die is provided with an inner cavity for placing the box blank below the male die component, the middle of the bottom of the inner cavity is provided with an ejection hole, and the size of the ejection hole is matched with that of the ejector rod;

step three, determining a split mode of step-by-step extrusion;

2. A stepwise extrusion process for effectively reducing a forming load of a container as defined in claim 1, wherein: the bottom of the lower die plate and the bottom of the female die are outwards diverged by taking the ejection hole as a circle center, and the mounting holes are used for mounting bolts to connect the lower die plate and the female die.

3. A stepwise extrusion process for effectively reducing a forming load of a container as defined in claim 1, wherein: the periphery of the insert is provided with a die drawing angle.