CN103111521B - Drawing die of rectangular container and drawing method - Google Patents

Abstract

The invention discloses a stretching die and a stretching method for a rectangular container, comprising an initial stretching die and a shaping die, the initial stretching die includes a concave die, a punch and a pressing ring, and the upper section of the punch has a quasi-rectangular structure. The top corner of the same rectangle as the workpiece is transitioned from a large arc with a radius equal to 1/3 to 2/3 of the length of the short side of the rectangle; the lower part of the punch is a square platform and the side edges are arc transitions; the inner hole of the binder ring Cooperate with the gap of the punch, the shape of the binder ring is similar to the cross-section shape of the punch, the middle part of each side of the bottom of the binder ring is chamfered, and the chamfer angle gradually increases from a certain distance from the top corner of the binder ring to the middle of each side; The height of the bottom surface of the binder ring gradually increases from the top corner to the middle of each side, showing a linear or arc-shaped arched structure; using this drawing die to apply the secondary drawing process to the product, first use the initial drawing die and then use the shaping die For stretching, the initial stretch coefficient is 0.646, the plastic stretch coefficient is 0.66, and the total stretch coefficient is 0.426. The invention selectively presses the edge, prevents the wrinkle and crack of the workpiece, and only needs secondary stretching.

Description

A stretching die and stretching method for a rectangular container

technical field

The invention belongs to the technical field of drawing dies, and in particular relates to a drawing die for a rectangular container and a method for stretching a rectangular container using the drawing die.

Background technique

For the stretching of rectangular containers in the prior art, especially the stretching of rectangular containers with flanges, the mold structure and process flow are very complicated. Due to the anisotropy of materials, the difference of metal flow conditions during stretching, the difference between the convex and concave Due to the uneven gap between the parts and the unequal frictional resistance, the shape, dimensional accuracy and surface quality of the parts vary greatly, and the mold wears quickly, and there are even defects such as local wrinkles, cracks and fractures of the parts. Stretching of rectangular containers generally requires the use of blank holders and stamping in multiple processes. For example, there is a rectangular container with a total stretch coefficient of 0.42. The existing technology requires three stretches, each with a stretch coefficient of 0.65. , 0.75, 0.86, respectively using the square --- square --- square process to complete three times. Obviously, more stretching times will lead to more molds, longer stretching time, low efficiency and high cost. Therefore, it is very important to rationally design stretching dies and stretching processes.

China Patent No. ZL 201020683361.8, a utility model patent named "head drawing die", discloses a drawing die, including a punch and a die, the punch is connected to a transmission device, and the die is provided with a boss. Because a convex step is provided, the blank holder is not pressed onto the workpiece, and when the workpiece is completely pulled out of the mold, the blank holder is still in its original position. The patent said "the blank holder is not pressed onto the workpiece", which means that a certain gap is uniformly reserved between the blank holder and the surface of the workpiece, which may have some effect on the circular blank, but for the flanged rectangular Stretching of the container is not positive. During the stretching process of the rectangular container, the flange is in a state of radial tension and tangential compression. The radial stretch makes the flange material thinner, and the tangential compression makes the flange thicker. The closer to the outside of the flange, The smaller the radial tensile stress, the greater the tangential compressive stress, which increases the thickness of the flange outside. This change is especially different for the middle and top corners of each side of the rectangle, and this difference is also related to the pressure of the blank holder ring. It is closely related, so it is not appropriate to keep a certain gap between the blank holder and the surface of the workpiece uniformly.

Contents of the invention

The technical problem to be solved by the present invention is to overcome the defect that the drawing dies in the prior art cannot be targeted to press the edges and easily cause poor quality of the parts, and to provide a method for selectively pressing the edges according to the structural differences of the parts and selectively Stretching dies that apply different pressures in order to improve the quality of the parts and simplify the stretching process, improve work efficiency and reduce costs.

The purpose of the present invention is achieved by the following technical solutions: a stretching die for a rectangular container, comprising an initial stretching die and a shaping die, the initial stretching die comprising a die, a punch and a binder ring, wherein, ( 1), the cross-sectional shape of the punch is a quasi-rectangular structure, and the quasi-rectangular structure means that the top corner of the rectangle identical to the workpiece is formed by a large arc transition, and the radius of the large arc is equal to 1/1 of the length of the short side of the rectangle. 3～2/3; the lower part of the punch is a four-sided platform structure and the side edge of the four-sided platform is a circular arc transition connection; (2), the inner hole of the binder ring is matched with the gap between the punch and the shape of the binder ring It is a quasi-rectangular structure similar to the cross-sectional shape of the punch, and the middle part of each side of the bottom of the binder ring has a progressive chamfer. (3) The height of the bottom surface of the binder ring gradually increases from the top corner to the middle of each side, showing a linear or arc-shaped arched structure.

The first step in stamping a rectangular container is to stamp and stretch the blank into a quasi-rectangular shape, instead of becoming a rectangular piece in one step, so that the material flow in the middle of each side of the blank and the quasi-rectangle is relatively increased, and the material at each corner is relatively large. The flow rate is relatively reduced to achieve the purpose of directional stretching, accurate deformation, avoiding wrinkling and preventing breakage; the height of the bottom surface of the binder ring is gradually increased from the top corner to the middle of each side in a linear or arc-shaped arch , it can achieve a gradual change of blank-holding force from large to small on the workpiece blank from the top corner to the middle. This gradual blank-holding force just matches the deformation and stress of the workpiece to ensure that the workpiece does not wrinkle or fracture.

Preferably, the linear or arc-shaped arched structure has a height difference of 0.1-1 mm.

Preferably, the length of the chamfered portion is less than or equal to 1/2 of the side length.

Preferably, the length of the chamfered portion is less than or equal to 1/4 to 1/5 of the side length.

Preferably, the angle of the chamfer is 5-20°.

As preferably, the lower surface of the upper mold base is provided with an annular lower groove, the upper surface of the binder ring is provided with an annular upper groove, the annular lower groove and the annular upper groove are correspondingly arranged, and the annular lower groove and the annular upper groove Spring coils are embedded between them.

Preferably, the spring ring is made of an annular rubber ring.

Another object of the present invention is to apply the drawing method of the drawing die of a kind of rectangular container, this method comprises the following steps:

Apply the stretching die of a rectangular container as mentioned above to process the product, the method is to carry out the secondary stretching process on the product blank, and use the initial stretching die for the first stretching, and the semi-finished product formed has a quasi-rectangular structure. The plastic mold is applied to the secondary stretching, and the finished product meets the requirements of the finished product; the total stretching coefficient is 0.426, wherein the stretching coefficient of the first stretching is 0.646, and the stretching coefficient of the second stretching is 0.66.

Preferably, the workpiece blank is a quasi-rectangular structure similar to the cross-sectional shape of the upper section of the punch, and the total area of the workpiece blank is equal to or slightly larger than the total area of the workpiece. the

The beneficial effects of the present invention are:

1. There is a gradual chamfer at the middle part of each side at the bottom of the binder ring of the initial drawing die, and the edge is selectively pressed according to the structural difference of the workpiece to prevent wrinkles and cracks;

2. The height of the bottom surface of the binder ring gradually increases from a certain distance from the top corner of the binder ring to the middle part of each side, so as to achieve the effect of gradual change of blank holder force, directional stretch and accurate deformation;

3. Apply the quasi-rectangular-rectangular stretching process, and only need two stretches to reach the standard;

4. The mold structure is compact, the product quality is good, and the cost is low;

5. The stretching process is simple, saving man-hours and improving efficiency.

Description of drawings

Fig. 1 is a schematic diagram of the initial drawing die structure of an embodiment of the present invention;

Fig. 2 is a schematic sectional view of the binder ring;

Fig. 3 is a schematic diagram of the shape of the workpiece blank.

In the figure, die 1; punch 2; binder ring 3; chamfer 31; linear arched structure 32; annular upper groove 33; 6; large circular arc 61; lower mold base 7; steps 71; top plate 8; ejector rod 81;

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

Embodiment: as shown in Figure 1, 2, a kind of stretching die of rectangular container comprises initial drawing die and shaping die, and initial drawing die comprises die 1, punch 2 and binder ring 3, punch 2 Fixed in the upper mold, the binder ring 3 is set on the outside of the punch 2 and is movably connected with the upper mold base 4 through a tie rod. The spring ring 5 is placed between the binder ring 3 and the upper mold base 4, and the The cross-sectional shape is a quasi-rectangular structure similar to the workpiece blank 6. The quasi-rectangular structure is formed by the transition of a large arc 61 at the apex of the rectangle, and the radius of the large arc 61 is equal to 3/5 of the length of the short side of the rectangle; The lower section is a four-sided platform structure, and the side edges of the four-sided platform are connected by a circular arc transition; the inner hole of the binder ring 3 is matched with the punch 2, and the shape of the binder ring 3 is similar to the cross-sectional shape of the punch. Rectangular structure, the middle part of each side of the bottom of the binder ring 3 has a progressive chamfer 31, and the angle of the chamfer 31 gradually increases from a position with a certain distance from the top corner of the binder ring to the middle part of each side; The height of the bottom surface of the ring 3 gradually increases from the adjacent two top corners to the middle of each side, forming a linear arch structure 32. The height difference of the linear arch structure 32 is 0.5mm, and the length of the chamfered portion is equal to the length of the side. 3/5; the angle of the chamfer 31 is 15°; the die 1 is fixed in the lower mold base 7, and the upper side of the lower mold base 7 is provided with a step 71, and the step 71 is used for positioning the workpiece blank 6; The surface is provided with an annular lower groove 41, the upper surface of the binder ring 3 is provided with an annular upper groove 33, and the annular lower groove 41 is set correspondingly to the annular upper groove 33, and the upper and lower ends of the spring ring 5 are embedded in the annular lower groove respectively. In the groove 41 and the annular upper groove 33 , the spring ring 5 is composed of an annular rubber ring.

Shown in Fig. 1 is the condition that the upper mold goes down until the binder ring 3 and the punch 2 just touch the workpiece blank 6.

In the first step of stamping a rectangular container, the blank 6 is punched and stretched into a quasi-rectangular shape, rather than a rectangular piece in one step, so that the material flow of the blank 6 in the middle of each side of the quasi-rectangle increases and the corners of each corner The amount of material flow in the part is relatively reduced to avoid the risk of wrinkling and fracture; the height of the bottom surface of the application binder ring 3 is linearly arched from the top corner to the middle of each side, and can reach 6 From the top corner to the middle, a gradual blank-holding force is applied from large to small. This gradual blank-holding force just matches the deformation and stress of the workpiece, achieving the effect of directional stretching and accurate deformation, and ensuring that the workpiece does not stand up. Wrinkled, not broken.

The inside of the die 1 is provided with a movable top plate 8, and the lower end surface of the top plate 8 is connected with a push rod 81, and the push rod 81 is movably matched with the die cushion 9.

Apply the stretching die of a kind of rectangular container described in the present invention to product and apply secondary stretching process, first stretching application initial stretching die processing, semi-finished product is quasi-rectangular structure, the second stretching application shaping die, The finished product meets the requirements of the finished product, and the total stretch coefficient is 0.426, among which the initial stretch coefficient is 0.646, and the shaping coefficient is 0.66.

The workpiece blank 6 is a quasi-rectangular structure similar to the cross-sectional shape of the upper part of the punch 2, so that the material flows according to the predetermined requirements during the stretching process, and the total area of the workpiece blank is slightly larger than the total area of the workpiece, leaving a little surplus The amount is in case the irregular part of the edge is cut flat after the stretching is completed. the

The present invention can be used in drawing dies and processes for rectangular containers, and has the effects of selective blank-holding and gradual change of blank-holding force, directional stretching and accurate deformation, preventing workpieces from wrinkling and cracking, compact mold structure, and high-quality workpieces Well, the advantages that can be achieved only by secondary stretching, if those skilled in the art make simple modifications or replacements to the above-mentioned content of the invention, such changes cannot be considered as departing from the scope of the present invention. Modifications obvious to one are intended to be included within the scope of the claims of the present invention.

Claims (7)

1. a drawing die of a rectangular container, comprising an initial drawing die and a shaping die, is characterized in that the initial drawing die comprises a die, a punch and a binder ring, wherein, (1), the cross-sectional shape of the punch It is a quasi-rectangular structure, and the said quasi-rectangular structure means that the apex of the same rectangle as the workpiece is formed by the transition of a large arc, and the radius of the large arc is equal to 1/3 to 2/3 of the length of the short side of the rectangle; the punch The lower part of the truss is a square truss structure and the side edges of the truss are connected by a circular arc transition; (2) The inner hole of the binder ring is matched with the punch, and the shape of the binder ring is similar to the cross-sectional shape of the punch The quasi-rectangular structure has a progressive chamfer at the middle of each side at the bottom of the binder ring, and the progressive chamfer means that the angle of the chamfer starts from a position with a certain distance from the top corner of the binder ring and slopes upward from the inside to the outside. (3) The height of the bottom surface of the binder ring gradually increases from the top corner to the middle of each side, showing a linear or arc-shaped upward concave arched structure. 2. A drawing die for a rectangular container according to claim 1, characterized in that the height difference of the linear or arc-shaped arched structures is 0.1-1 mm. 3. A drawing die for a rectangular container according to claim 2, wherein the angle of the chamfer is 5-20°. 4. A drawing die for a rectangular container according to claim 1 or 2, characterized in that the lower surface of the upper mold base has an annular lower groove, the upper surface of the binder ring has an annular upper groove, and the annular lower groove The groove is arranged corresponding to the upper annular groove, and a spring ring is embedded between the lower annular groove and the upper annular groove. 5 . The drawing die for a rectangular container according to claim 4 , wherein the spring ring is formed of an annular rubber ring. 6 . 6. A stretching method for a rectangular container, characterized in that, the stretching die as claimed in claim 1 is used to apply a secondary stretching process to the product blank, and the initial stretching die is used for the first stretching, and the formed The semi-finished product has a quasi-rectangular structure, and the plastic mold is used for the second stretching, and the finished product meets the requirements of the finished product; the total stretching coefficient is 0.426, of which the stretching coefficient of the first stretching is 0.646, and the stretching coefficient of the second stretching is 0.66. 7. A stretching method for a rectangular container according to claim 6, wherein the blank is a quasi-rectangular structure similar to the cross-sectional shape of the upper section of the punch, and the total area of the blank is equal to or slightly larger than The total area of the part.