A method for forming a narrow rectangular tube with small corners by extreme stretching

Abstract

A method for forming a narrow rectangular tube with a small corner by extreme stretching, comprising two parts: blank determination and stretching die design; the blank is designed with a blank geometric pattern by a blank expansion calculation method for rectangular tube products, and the deepest barrel that can be stretched at the punch corner of the rectangular tube part at one time is calculated as the basic rectangular tube expansion area of ​​the blank shape and outer dimensions; the calculated width is determined as the blank reference width for the extreme stretching process, and the height of the upper rectangular tube expansion area is determined; the expansion area of ​​the remaining rectangular tubes is calculated by the rectangular tube blank expansion calculation method; 10% of the calculated area of ​​the lower rectangular tube is divided into two equal parts, which are arranged in the "X" axis direction of the upper blank, and 90% of the area is divided into two equal parts, which are arranged in the "Y" axis direction; the blank is finally formed into a sheet that is symmetrical in the upper and lower parts and in the left and right parts; and then stretched into a final product by a special stretching die.

Description

Technical Field

[0001] The present invention relates to a machining technology, in particular to an ultimate stretching forming method for a small-corner long and narrow rectangular cylinder. Background Art

[0002] Stretching forming is a well-known technology commonly used in machining. In the stretching forming of a rectangular shape, for parts with a small inner R, multiple stretching operations are usually required, and the R corner is gradually formed to reach the required part forming height and shape. Due to the need for multiple die formings, the die cost of this kind of product is usually relatively high, so that it is necessary to change the product design or meet the final product requirements through splicing and split welding.

[0003] By calculating the stretching limit of the material during drawing and calculating the redundancy during drawing, precise calculation of the unfolding is carried out at the blank stage, so that when the material flows in the final drawing stage, there will be no convection between materials or within the material, thereby eliminating wrinkles, bulges, and cracks caused by the flow of excess materials.

[0004] The main technical problems to be solved are as follows:

[0005] 1. The one-time stretchable ultimate depth (stretching rate) of a rectangular cylinder is limited by the size of the four corners of the punch and the flowability of the material, and the conventional empirical law: the stretchable depth of a rectangular cylinder is ≤ 6 to 8

[0006] times the stretching punch four corners.

[0007] 2. The process determination of the conventional deep drawing process for a small-corner rectangular cylinder requires decomposing the corners of the final product and inversely deducing the actual required number of process steps for the product.

[0008] 3. Due to the technical particularity of the stretching process of a rectangular cylinder, the stretching products are not popular except for special product design requirements. The fundamental reason is closely related to the die development ability and the accumulated high cost. Therefore, the industry generally designs the split stretching parts as components and completes the shape of the stretching process products with similar shapes through welding process and grinding.

[0009] Therefore, how to solve the one-time forming problem of a small-corner rectangular cylinder has always been an urgent technical issue in the machining field. Summary of the Invention

[0010] The purpose of the present invention is to propose an ultimate stretching method for a small-corner long and narrow rectangular cylinder that can be stretched and formed in one time.

[0011] An ultimate stretching forming method for a small-corner long and narrow rectangular cylinder, characterized in that: it includes two parts: blank determination and stretching die design. The blank is carried out according to the following steps:

[0012] A: Calculation and area configuration of stretched blank:

[0013] 1) By analyzing the structure of the designed rectangular cylinder product, the surface basic area of ​​the rectangular cylinder is first estimated, and the approximate basic shape is developed through the general rectangular area calculation method. Then, according to the shape required by the final rectangular cylinder itself, a polygonal blank that is roughly symmetrical in the upper, lower, left and right directions is roughly calculated;

[0014] 2) Design the geometric pattern of the blank using the blank expansion calculation method for rectangular cylindrical products, and calculate the deepest barrel that can be stretched at the punch corner of the rectangular barrel part at one time as the basic expansion area of ​​the blank shape and outer dimensions;

[0015] 3) The width calculated above is determined as the reference width of the blank using the ultimate stretching process, and the reference length of the unfolded area of ​​the rectangular tube is determined;

[0016] 4) Continue to follow the rectangular tube blank expansion calculation method in the first step to calculate the remaining expansion area of ​​the rectangular tube and the remaining expansion area of ​​the rectangular tube at the end of the special-shaped extension;

[0017] 5) Divide 10% of the calculated area of ​​the lower rectangular tube of the extension into two equal parts, arranged in the "X" axis direction of the unfolded base blank, and divide 90% of the area into two equal parts, arranged in the "Y" axis direction; so that the blank will eventually form a nearly rectangular sheet that is symmetrical in the upper and lower parts and in the left and right parts.

[0018] B. Design of stretching die:

[0019] The stretching die is composed of a forming die 5, a forming punch 7, a pressure plate 6, and a fixed plate 8; the forming punch 7 and the forming die 5 are fitted in a gap-like manner, the inner cavity of the forming die 5 is a rectangular cavity, the joint of the adjacent edges around it is a small right-angle corner R1, and the front end columnar body of the outer end of the forming punch 7 is a large right-angle corner R2; a pressure plate 6 is provided on the upper cover surface of the forming die 5, and a slot hole of the same specification as the middle slot hole of the forming punch 7 is provided in the middle part of the pressure plate 6, and a fixed plate 8 fixedly connected to the forming punch 7 is provided at the rear of the forming punch 7, and a spring mechanism 9 is provided between the fixed plate 8 and the pressure plate 6, and the space between the die 5 and the pressure plate 6 is the placement area of ​​the blank.

[0020] Furthermore, the stretched blank can be divided into: a central conventional stretching portion 1 and a radial material distribution area 2 around the corners symmetrically distributed on the left and right sides of the central conventional stretching portion 1, a super extreme stretching material distribution area 3 and material areas 1 at the stretching portions at both ends. The super extreme stretching material distribution area 3 and the radial material distribution area 2 around the corners are symmetrically distributed on both sides of the material area 1 at the stretching portions at both ends, wherein the outer edge extension lines of the two super extreme stretching material distribution areas 3 intersect at the material areas 1 at the stretching portions at both ends.

[0021] Furthermore, the measurement method of the blank is as follows: use the distance of H1 to determine the position of the drawing limit point D1, and use the ordinary drawing limit point H2 on the front side to obtain D2; then use points D1 and D2 as the center of the circle, take the distance from point D1 to the highest point of the product as its radius R1, and take the distance from point D2 to the highest point of the product as its radius R2, and draw a circle respectively. The upper and lower small circles and the circle in the middle intersect to obtain two points respectively, and ignore the points that interfere with the product, so as to obtain the other two important points P1 and P2. The obtained points P1 and P2 are smoothly connected with point D1 with arcs, and the edge boundaries on the left and right sides of the blank can be obtained.

[0022] Furthermore, the corresponding relationship between the product unfolding size and the formed product is as follows:

[0023] A = 2A1 + 2A2 + A3, B = 2B1 + 2B2 + B3;

[0024] Among them: A is the total width after unfolding, B is the unfolded size of the extreme stretching points on the left and right sides; C is the compensation length of the over-limit stretching material; the correspondence between the size of the blank after unfolding and the molded product should conform to the following corresponding relationship: A=2A1+2A2+A3; B=2B1+2B2+B3.

[0025] The extreme stretching forming method of the narrow rectangular tube with small corners proposed in the above technical scheme not only completely abandons the traditional production of narrow rectangular tube with small corners which requires multiple processes such as stamping, welding and grinding, and realizes the one-time stamping and stretching to obtain the designed rectangular tube body, but also can greatly shorten the manufacturing time and reduce the manufacturing cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the blank design scheme of the present invention;

[0027] Figure 2 It is a schematic diagram of the design key points of the blank of the present invention;

[0028] Figure 3 A schematic diagram of the key design points for stretch products;

[0029] Figure 4This is a schematic diagram of the corresponding relationship between the unfolded size of the blank and the formed product;

[0030] Figure 5 It is a schematic diagram of the stretching die structure;

[0031] Figure 6 It is a schematic diagram of the working state of the stretching die;

[0032] Figure 7 for Figure 6 D-D section diagram;

[0033] Figure 8 for Figure 6 C-C section view;

[0034] Fig. 9 It is a schematic diagram of the primary product after stretching;

[0035] Fig.10 Schematic diagram of the final product after stretch forming.

[0036] In the figure: 1—the conventional stretching part in the middle; 2—the radial material release part around the corner;

[0037] 3—Super extreme pulling part; 4—Stretching parts at both ends; 5—Die; 6—Pressing plate;

[0038] 7—forming punch; 8—fixed plate; 9—spring; 10—large R angle; 11-small R angle;

[0039] 12- a narrow rectangular cylinder with small corners and flange edges; 13- a final stretching cylinder;

[0040] A-total width of the blank after unfolding; A1-flange of the product; A2-height of the product;

[0041] A3—product width; B-the dimensions after expansion at the extreme stretching points on the left and right sides;

[0042] B1—distance from the limit point to the R angle; B2—molding R angle;

[0043] C-compensation length of over-limit stretched material; C3-part of over-limit material;

[0044] D1—The highest point that can be reached by ordinary molding on the left and right sides;

[0045] D2—normal stretching limit point on the front and rear sides; G1—bottom reference point;

[0046] H1 is the highest height of stretching at both ends; H2 is the highest height of conventional stretching in the middle;

[0047] L1—general height of conventional stretching in the middle; K1—final product height;

[0048] R1—the distance between the stretching limit point at both ends and the highest point;

[0049] R2—The distance between the highest point in the middle and the highest point on the side. DETAILED DESCRIPTION

[0050] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments of the present invention are given.

[0051] The core idea of ​​the limit stretching forming method of the narrow rectangular tube with small corners proposed in the above technical solution is: by analyzing the structure of the designed rectangular tube product, the surface basic area of ​​the rectangular tube is first estimated, and the approximate basic shape is developed through the general rectangular area calculation method, and then a polygonal blank that is roughly symmetrical in the upper, lower, left and right directions is roughly calculated according to the shape required by the final rectangular tube itself;

[0052] According to the design scheme of the narrow rectangular tube with small corners, the blank to be stretched and formed is firstly designed, and then the blank is stretched and formed at one time using a stretching die suitable for the narrow rectangular tube with small corners.

[0053] Figure 1-4 In order to realize the design scheme of the small corner narrow rectangular tube stretch forming blank, Figure 1 What is given is a schematic diagram of the functional distribution of the blank plane based on the rectangular coordinate system.

[0054] 10% of the calculated area of ​​the lower rectangular tube is divided into two equal parts and arranged in the "X" axis direction of the unfolded upper blank, and 90% of the area is divided into two equal parts and arranged in the "Y" axis direction; so that the blank is finally formed into a sheet that is symmetrical in the upper and lower parts and in the left and right parts and is close to a rectangle.

[0055] From the attached Figure 1 It can be seen from the figure that the narrow rectangular cylinder with small corners to be produced has a cylinder blank whose distribution in the middle part between the X-axis and the Y-axis after unfolding is the conventional stretching part 1 in the middle of the rectangular cylinder after forming, and the parts of the blank along both sides of the X-axis are the radial material release part 2 around the corner, the super extreme pulling part 3 and the stretching parts 4 at both ends.

[0056] Figure 2 Given are the key design points for the radial material release portion 2 at the corners, the super-limit stretching portion 3 and the stretching portions 4 at both ends, which are distributed on the left and right sides of the central conventional stretching portion 1 during the stretching process of the blank.

[0057] in Figure 2 , Figure 3 and Figure 4The design points of the rectangular cylinder blank based on the rectangular cylinder after stretching are given respectively:

[0058] The stretched blank can be divided into: a central conventional stretching portion 1 and a corner peripheral radial material distribution area 2 symmetrically distributed on the left and right sides of the central conventional stretching portion 1, a super extreme stretching material distribution area 3 and a material area 1 at the stretching portions at both ends. The super extreme stretching material distribution area 3 and the corner peripheral radial material distribution area 2 are symmetrically distributed on both sides of the material area 1 at the stretching portions at both ends, wherein the outer edge extension lines of the two super extreme stretching material distribution areas 3 intersect at the material area 1 at the stretching portions at both ends.

[0059] The measurement method of the blank is as follows: use the distance of H1 to determine the position of the pulling limit point D1, and use the ordinary drawing limit point H2 on the front side to obtain D2; then use points D1 and D2 as the center of the circle, take the distance from point D1 to the highest point of the product as its radius R1, and take the distance from point D2 to the highest point of the product as its radius R2, and draw a circle respectively. The upper and lower small circles and the circle in the middle intersect to obtain two points respectively, and ignore the points that interfere with the product, so as to obtain the other two important points P1 and P2. The obtained points P1 and P2 are smoothly connected with point D1 with arcs, and the edge boundaries on the left and right sides of the blank can be obtained.

[0060] The corresponding relationship between the product unfolding size and the formed product is as follows:

[0061] A = 2A1 + 2A2 + A3, B = 2B1 + 2B2 + B3;

[0062] Among them: A is the total width after unfolding, B is the unfolded size of the extreme stretching points on the left and right sides; C is the compensation length of the over-limit stretching material; the correspondence between the size of the blank after unfolding and the molded product should conform to the following corresponding relationship: A=2A1+2A2+A3; B=2B1+2B2+B3.

[0063] Attached Figure 5 , Attachment Figure 6 A schematic diagram of the die structure for stretching the narrow rectangular tube with small corners; Figure 7 for Figure 6 D-D cross-sectional view, Figure 8 for Figure 6 Cross-sectional view along CC direction.

[0064] The die for stretching a narrow rectangular tube with small corners is composed of a forming die 5, a forming punch 7, a pressure plate 6 and a fixed plate 8; the forming punch 7 and the forming die 5 are fitted in a gap-like manner, the inner cavity of the forming die 7 is a rectangular cavity, the joint of the adjacent edges around it is a small right-angle corner R1, and the front end columnar body of the outer end of the forming punch 7 is a large right-angle corner R2; a pressure plate 6 is provided on the upper cover surface of the forming die 5, and a slot hole of the same specification as the middle slot hole of the forming punch 7 is provided in the middle part of the pressure plate 6, a fixed plate 8 fixedly connected to the forming punch 7 is provided at the rear part, and a spring mechanism 9 is provided between the fixed plate 8 and the pressure plate 6, and the space between the die 5 and the pressure plate 6 is the placement area of ​​the blank.

[0065] The actual stretch forming process of this narrow rectangular tube with small corners is as follows:

[0066] 1. First, place the blank on the lower part of a pressing plate 6 with a through hole for the forming punch 7 to penetrate in the middle;

[0067] 2. As the upper forming die 5 is gradually pressed downward, the blank placed on the press plate 6 is supported by the lower forming die convex die 7, so that the blank is supported by the forming convex die 7 along the gap between the upper forming die 5 and the forming convex die 7 until the upper part of the fixed plate 8 on which the forming convex die 7 is placed gradually approaches the bottom of the press plate 6, indicating that the sheet blank has been successfully stretched into a narrow rectangular cylinder with small corners; at this time, as long as the propulsion force on the upper die 5 is removed, the upper forming die 5 is removed from the upper part, and the forming convex die 7 set on the fixed plate 8 is pushed out at the same time, the following can be obtained Fig. 9 The illustrated embodiment is a narrow rectangular cylinder 12 with small corners and a flange.

[0068] 3. Finally, after cutting according to the actual required depth of the rectangular cylinder, you can get Fig.10 The narrow rectangular cylinder with small corners shown finally stretches the cylinder 13.

[0069] The above is only one of the basic implementation methods of the present invention given by the applicant in accordance with the technical solution. Any improvement made by any technician in the industry with reference to this basic solution that does not have substantial creativity should be deemed to fall within the protection scope of the present invention.

Claims

1. A method for the ultimate stretching of a narrow rectangular cylinder with small corners. Features: The steps include: S1: Calculation and area configuration of stretched blank: 1) By analyzing the structure of the designed rectangular cylinder product, the surface basic area of ​​the rectangular cylinder is first estimated, and the approximate basic shape is developed through the general rectangular area calculation method. Then, according to the shape required by the final rectangular cylinder product itself, a polygonal blank that is roughly symmetrical in top, bottom, left and right is roughly calculated; 2) Design the geometric pattern of the blank using the blank development calculation method for rectangular cylindrical products, and calculate the deepest barrel that can be stretched at the punch corner of the rectangular cylindrical product as the basic development area of ​​the blank shape and outer dimensions; 3) The width calculated above is determined as the reference width of the blank using the present limit stretching process, and the reference length of the unfolded area of ​​the rectangular tube is determined; 4) Continue to follow the rectangular tube blank expansion calculation method to calculate the expansion area of ​​the remaining rectangular tubes and the remaining expansion area of ​​the rectangular tube body of the end special-shaped extension; 5) 10% of the calculated area of ​​the rectangular cylinder of the special-shaped extension part is divided into two equal parts, left and right, and arranged in the "X" axis direction of the base blank, and 90% of the area is divided into two equal parts, upper and lower, and arranged in the "Y" axis direction; so that the blank is finally formed into a sheet that is symmetrical in the upper, lower, left and right directions and is close to a rectangle; S2. Design of the stretching die: The stretching die is composed of an upper forming die (5), a forming punch (7), a pressure plate (6), and a fixed plate (8); the forming punch (7) and the upper forming die (5) are fitted in a gap-like manner, the inner cavity of the upper forming die (5) is a rectangular cavity, the joint of the adjacent edges around it is a small right-angle corner R1, and the front end columnar body of the outer end of the forming punch (7) is a large right-angle corner R2; a pressure plate (6) is provided on the upper cover surface of the upper forming die (5), and a slot hole of the same specification as the middle slot hole of the forming punch (7) is provided in the middle part of the pressure plate (6), a fixed plate (8) fixedly connected to the forming punch (7) is provided at the rear of the forming punch (7), and a spring mechanism (9) is provided between the fixed plate (8) and the pressure plate (6), and the space between the upper forming die (5) and the pressure plate (6) is a blank placement area; S3. Obtain a rectangular cylinder through one-time stamping and stretching.

2. The method for forming a narrow rectangular cylinder with small corners by extreme stretching according to claim 1, Features: The drawn blank is divided into: a central conventional drawing portion (1), a corner peripheral radial material distribution area (2) symmetrically distributed on the left and right sides of the central conventional drawing portion (1), a super extreme drawing material distribution area (3) and a material area (4) at the two end drawing portions. The super extreme drawing material distribution area (3) and the corner peripheral radial material distribution area (2) are symmetrically distributed on both sides of the material area (4) at the two end drawing portions, wherein the outer edge extension lines of the two super extreme drawing material distribution areas (3) intersect at the material area (4) at the two end drawing portions.

3. The method for forming a narrow rectangular cylinder with small corners by extreme stretching as claimed in claim 2, Features: Step S3 is specifically as follows: 1) First, the blank is placed on the lower part of a press plate (6) with a through hole for the forming punch (7) to penetrate in the middle; 2) As the upper forming die (5) is gradually pressed downward, the blank placed on the press plate (6) is supported by the forming punch (7), so that the blank is supported by the forming punch (7) along the gap between the upper forming die (5) and the forming punch (7) until the upper part of the fixed plate (8) on which the forming punch (7) is placed gradually approaches the bottom of the press plate (6), indicating that the sheet-like blank has been successfully stretched into a narrow rectangular cylinder with small corners; at this time, as long as the pushing force on the upper forming die (5) is removed, the upper forming die (5) is removed from the top, and the forming punch (7) set on the fixed plate (8) is pushed out at the same time, a narrow rectangular cylinder with small corners and a flange edge can be obtained; 3) Finally, the flange edge of the lower edge of the narrow rectangular cylinder with a small corner is cut off, and the final stretched cylinder of the narrow rectangular cylinder with a small corner is obtained after cutting according to the actual required depth of the rectangular cylinder.

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