Double-roller multi-track parallel ball rolling die and process

Abstract

The invention relates to the field of metal plastic forming processes, and provides a double-roller multi-track parallel ball rolling die and process. The die comprises a first round roller die and a second round roller die; the first round roller die comprises a plurality of ribs which are arranged side by side, and all the ribs have the same starting and ending positions; the first rib located in the middle is arranged in the circumferential direction of the roller surface, and the other ribs on the two sides of the first rib are obliquely arranged relative to the first rib; the height of each protruding edge is gradually increased, and every two adjacent protruding edges form a first half rolling ball track. The total width of all the convex edges at the rolling starting position is smaller than that of all the convex edges at the rolling finishing position; the second round roller die is provided with protruding edges corresponding to the first round roller die, and a second half rolling ball track is formed between every two adjacent protruding edges. The whole rolling process meets the volume conservation principle, and the precision of the rolled ball piece is high; a plurality of metal balls with the same size can be formed at a time, continuous production can be achieved, and the production efficiency is high.

Description

Technical Field

[0001] This invention relates to the field of metal plastic forming processes, and in particular to a double-roller multi-track parallel ball rolling die and process. Background Technology

[0002] Small and medium-sized metal spheres (5mm-10mm in diameter) are widely used in bearings, grinding, and other industries. The forming of spheres mainly includes cold / hot rolling, cold / hot upsetting, and cutting. Rolling can achieve high efficiency and high material utilization. The mainstream steel ball rolling forming method is only skew rolling. With the continuous emergence of new processes, wedge cross rolling of steel balls has also appeared. However, the precision achievable by skew rolling is not high, and the force is uneven at various locations during the rolling process. Precision and forming quality are highly dependent on the process parameters during rolling. Twin-roll wedge cross rolling has high precision, but because less metal participates in deformation at the wedge tip at the beginning of the rolling process, insufficient friction leads to significant slippage. Therefore, the initial die adjustment procedure is complex, and increasing die friction is an unavoidable process. The process of rolling bars into balls requires balancing the diameter expansion rate, which is the ratio of the target ball's diameter to the billet's diameter. An excessive diameter expansion rate can cause deep annular grooves and incomplete filling of the steel balls. Therefore, a forming method with high rolling efficiency, high forming accuracy, good friction conditions, and low diameter expansion rate is needed.

[0003] CN115415453A discloses a multi-hole parallel wedge cross rolling die and a forming method, the unfolded view of which is shown below. Figure 1 As shown, a twin-roll wedge cross rolling process is used, but the following problems exist: On the one hand, the starting positions of each roll table are different, especially at the start of rolling, the billet and the die only contact at one point, making it difficult to maintain a stable position of the billet during rolling, causing the bar to skew after rolling begins; on the other hand, during the wedge cross rolling process, the material of the billet continuously flows outward along the axial direction. This axial flow leads to incomplete metal filling in a single ball groove, uneven metal flow, and the rolled balls will exhibit non-roundness, material shortage, or overlapping phenomena, such as... Figure 7 As shown, this is especially true for small-sized (diameter within 6mm) spherical parts; furthermore, without volume balance calculations for the mold, the parameters for controlling the forming quality during the forming process are unclear, and the accuracy and efficiency of the rolled balls need to be further improved. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a dual-roller multi-track parallel ball rolling die and process. Each cross-sectional cavity of the die is calculated with volume conservation, which can realize high-precision rolling of spherical parts with small diameter expansion rate.

[0005] The present invention adopts the following technical solution: On one hand, the present invention provides a dual-roll multi-track parallel ball rolling die, comprising a first round roll die and a second round roll die; The first round roll die includes multiple protrusions arranged side by side, all of which have the same starting and ending positions; the first protrusion located in the middle is arranged circumferentially along the roll surface, and the other protrusions on both sides of the first protrusion are arranged at an inclination relative to the first protrusion; the height of each protrusion gradually increases, and a first half-rolling ball track is formed between two adjacent protrusions; the total width of all protrusions at the rolling start position is less than the total width of all protrusions at the rolling completion position. The second round roll mold is provided with a protruding ridge corresponding to the first round roll mold, and a second half-ball rolling track is formed between two adjacent protruding ridges; The first hemispherical track and the corresponding second hemispherical track constitute a complete ball rolling track; when the roller mold rotates, the cylindrical blank is gradually rolled into multiple spherical parts by the multiple ball rolling tracks composed of the first roller mold and the second roller mold.

[0006] In addition to any of the possible implementations described above, another implementation is provided in which the ball rolling track includes an arc segment and a straight segment, the straight segment being located at the top and bottom of the ball rolling track, and the arc segment being located on both sides of the straight segment; from the starting position of rolling to the finishing position of rolling, the length of the straight segment gradually decreases, the length of the arc segment gradually increases, and the billet gradually changes from a short cylinder shape to being squeezed by the convex edge, and is rolled into a spherical shape including a connecting neck, a ball platform, and a cylindrical part; the connecting neck gradually becomes thinner and longer, and the cylindrical part gradually becomes shorter to zero, eventually becoming a spherical part.

[0007] In addition to any of the possible implementations described above, another implementation is provided in which the volume of the cylindrical billet entering the ball-rolling track at the starting position of rolling is equal to the volume of the rolled spherical part, and approximately equal to the volume of the metal in the ball-rolling track at any moment during the rolling process plus the volume of the connecting neck; the volume conservation equation is as follows: ; ; ; ; ; ; In the formula, V is the volume of the cylindrical billet entering the ball rolling track, or the volume of the spherical part after rolling; V1 and V5 are the volumes of the two semi-connecting necks, respectively; V3 is the volume of the cylindrical part; V2 and V4 are the volumes of the two ball platforms, respectively; L0 represents the distance between two adjacent convex ridges at the feed inlet; d represents the diameter of the billet; L represents the diameter of the connecting neck; b represents the length of the connecting neck, which is equal to the width of the top of the convex ridge; h2 represents the height of the ball platform; R represents the radius of the target ball; and a represents the length of the straight section.

[0008] In addition to any of the possible implementations described above, another implementation is provided, wherein the ball rolling track is specifically designed as follows: the ratio of the target ball diameter D to the bar diameter d is 105%-110%, the height of each convex ridge increases linearly, and the length of the straight section gradually decreases to 0; given the values ​​of the initial height, end height, and initial top width of the convex ridge, the values ​​of the top width of the convex ridge and the length of the straight section of each cross section of the ball rolling track are obtained according to the volume conservation equation.

[0009] The width of the convex ridge tip changes from the initial position to the final position, first narrowing and then widening, which is due to the volume balance calculation. In the early stage of the rolling process, the ridge height is small and the plastic deformation is not severe. In the middle stage of rolling, the plastic deformation gradually intensifies, and the convex ridge needs to gradually cut into the billet until it reaches the axis of the billet. Therefore, the ridge width becomes smaller at this time. In the final stage of rolling, the ridge width increases because the adjacent balls need to separate. This can also improve the strength of the convex ridge and extend the die life.

[0010] In addition to any of the possible implementations described above, a further implementation is provided in which, at the rolling completion position, the height of the convex edge of the first roller die reaches the height of the center of the spherical part, and the height of the convex edge of the second roller die is slightly lower than the height of the center of the spherical part.

[0011] In addition to any of the possible implementations described above, a further implementation is provided in which a guide plate is provided between the first and second roller molds, and a column for supporting the blank is provided on the upper part of the guide plate.

[0012] In addition to any of the possible implementations described above, another implementation is provided in which the protruding edges of the first and second roller molds are provided with a top bevel angle ф at the tail end, with a value of 15-20°.

[0013] In addition to any of the possible implementations described above, a further implementation is provided in which two adjacent protrusions are inclined with an included angle of 1°-3°.

[0014] On the other hand, the present invention also provides a twin-roll multi-track parallel ball rolling process, wherein the process uses the aforementioned twin-roll multi-track parallel ball rolling die, and the process includes: S1. Adjust the distance between the first and second round roller dies so that the ball rolling track forms a complete circle with the same diameter as the target ball part at the end of the convex edge; S2. Place the cylindrical billet at the starting rolling position; S3. The first and second round roller dies rotate in the same direction and at the same speed. The cylindrical bar is squeezed and deformed in the ball rolling track formed by the protrusions of the first and second round roller dies, and gradually rolled into a spherical shape including a connecting neck, a ball platform, and a cylindrical part. Finally, the connecting neck is cut off and formed into multiple spherical parts.

[0015] The process is applicable to cold forming, hot forming, or warm forming of small-diameter steel balls with a diameter of 5mm-10mm.

[0016] The beneficial effects of this invention are as follows: 1. The mold of this invention calculates the volume of metal that can be accommodated within the corresponding tracks of multiple cross sections, ensuring that the volume of the die at each position during the rolling process is equal to the volume of the final sphere. The height and width of the convex edge of this mold design can be adjusted according to the different types of metal being rolled. Theoretical calculations show that the entire process satisfies the principle of volume conservation, making the metal flow pattern during rolling more reasonable and resulting in high precision rolled spherical parts.

[0017] 2. The range of each ball-forming part is defined at the beginning of rolling, which restricts the axial material flow of the billet and improves the quality of the ball-forming.

[0018] 3. The equal volume design of the forming roller table is more in line with the billet forming process. During the rolling process, the die outline is always close to the billet, resulting in higher forming efficiency.

[0019] 4. At the start of rolling, the die and the billet make contact at multiple points, making it easy to fix the position of the billet and ensuring the rolling quality.

[0020] 5. The forming method can form multiple metal balls of the same size in one operation, enabling continuous production. Production efficiency is considerable, and it is suitable for cold rolling, warm rolling, and hot rolling of metal ball parts. Attached Figure Description

[0021] Figure 1 The diagram shown is a schematic diagram of the mold development for cross-rolling spherical parts using a double-roll wedge in the prior art.

[0022] Figure 2 The diagram shown is a schematic representation of the overall structure of a dual-roller, multi-track, parallel ball rolling die according to an embodiment of the invention.

[0023] Figure 3 The figure shown is an assembly diagram of the components viewed axially in the embodiment.

[0024] Figure 4The diagram shown is a schematic diagram of the mold unfolding and a schematic diagram of a certain cross section in the embodiment.

[0025] Figure 5 The diagram shown is a schematic representation of the volume composition of the blanks contained in the rotating body formed by the circular arc groove of any cross section of the mold in the embodiment.

[0026] Figure 6 The diagram shown is a schematic of the guide plate structure in the embodiment.

[0027] Figure 7 The image shows a comparison of photographs of metal balls obtained by different rolling methods.

[0028] In the figure: 1 First roller mold; 2 Second roller mold; 3 Cylindrical blank; 4 Guide plate; 1-1 Protruding ridge on the surface of the first roller mold; 1-2 Unloading groove on the surface of the first roller mold; 2-1 Protruding ridge on the surface of the second roller mold; 2-2 Unloading groove on the surface of the second roller mold; 4-1 Guide plate body; 4-2 Column on the surface of the guide plate; 4-3 Arc surface of the guide plate. Detailed Implementation

[0029] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be noted that the technical features or combinations of technical features described in the following embodiments should not be considered in isolation, but can be combined with each other to achieve better technical effects.

[0030] like Figure 2 As shown, an embodiment of the present invention provides a dual-roller multi-track parallel ball rolling die, comprising a first round roll die 1 and a second round roll die 2; The first circular roller mold 1 includes multiple protruding ribs 1-1 arranged side by side, all of which have the same starting and ending positions. The first protruding rib located in the middle is arranged circumferentially along the roller surface, and the other protruding ribs on both sides of the first protruding rib are arranged at an angle relative to the first protruding rib. The height of each protruding rib gradually increases, and the width of the top of each protruding rib gradually widens, forming a first semi-rolling ball track between two adjacent protruding ribs. The total width of all the protruding ribs at the rolling start position is less than the total width of all the protruding ribs at the rolling completion position. (See the unfolded diagram below.) Figure 4 As shown; The second round roller mold 2 is provided with a protruding rib 2-1 corresponding to the first round roller mold, and a second half-ball rolling track is formed between two adjacent protruding ribs; The first hemispherical track and the corresponding second hemispherical track constitute a complete ball rolling track; when the roller molds 1 and 2 rotate, the cylindrical blank is gradually rolled into multiple spherical parts by the multiple ball rolling tracks composed of the first roller mold 1 and the second roller mold 2.

[0031] In one specific embodiment, the two circular roller molds 1 and 2 rotate in the same direction around their own axes during operation, and the assembly relationship between the rollers, the billet, and the guide plate 4 is as follows: Figure 2 As shown.

[0032] In one specific embodiment, the ball rolling track includes an arc segment and a straight segment. The straight segment is located at the top and bottom of the ball rolling track, and the arc segment is located on both sides of the straight segment. From the starting position of rolling to the finishing position, the length of the straight segment gradually decreases, and the length of the arc segment gradually increases. The billet is gradually squeezed by the convex ridge from a short cylindrical shape and rolled into a spherical shape including a connecting neck, a ball platform, and a cylindrical part. The connecting neck gradually becomes thinner and longer, and the cylindrical part gradually becomes shorter to zero, eventually becoming a spherical part.

[0033] In one specific embodiment, such as Figure 3 As shown, an unloading groove 2-2 is provided at the end of the protrusion, and the formed spherical parts fall into the unloading groove 2-2.

[0034] In one specific embodiment, such as Figure 5 As shown, the volume of the cylindrical billet entering the ball-rolling track at the initial rolling position is equal to the volume of the rolled spherical part, which is approximately equal to the volume of the metal in the ball-rolling track at any given moment during the rolling process plus the volume of the connecting neck; the volume conservation equation is as follows: ; ; ; ; ; ; In the formula, V is the volume of the cylindrical billet entering the ball rolling track, or the volume of the spherical part after rolling; V1 and V5 are the volumes of the two semi-connecting necks, respectively; V3 is the volume of the cylindrical part; V2 and V4 are the volumes of the two ball platforms, respectively; L0 represents the distance between two adjacent convex ridges at the feed inlet; d represents the diameter of the billet; L represents the diameter of the connecting neck; b represents the length of the connecting neck, which is equal to the width of the top of the convex ridge; h2 represents the height of the ball platform; R represents the radius of the target ball; and a represents the length of the straight section.

[0035] The mold can be designed according to the required diameter expansion rate, which is expressed as the ratio of the target ball diameter D to the billet diameter d. The method of this invention can be designed according to the diameter expansion rate applicable to different materials: the basic rule is that the larger the diameter expansion rate, the smaller the inclination angle between the two side edges and the middle edge, the more ball rolling grooves on the mold surface, and the larger the angle between the outermost edge and the middle edge.

[0036] In one specific embodiment, the ball rolling track is specifically designed as follows: the ratio of the target ball diameter D to the bar diameter d is 105%-110%, the height of each convex ridge increases linearly, the top width of the convex ridge first narrows and then widens, and the length of the straight section gradually decreases to 0; given the initial height, end height, and initial top width of the convex ridge, the top width of the convex ridge and the length of the straight section of each cross section of the ball rolling track are obtained according to the volume conservation equation.

[0037] In one specific embodiment, at the rolling completion position, the height of the protrusion of the first round roll die 1 reaches the height of the center of the spherical part, and the height of the protrusion of the second round roll die 2 is slightly lower than the height of the center of the spherical part.

[0038] In one specific embodiment, a guide plate 4 is provided between the first roller mold 1 and the second roller mold 2, and a column 4-2 for supporting the blank is provided on the upper part of the guide plate 4.

[0039] In one specific embodiment, such as Figure 6 As shown, the guide plate 4 has an arc surface 4-3 that is the same as the maximum outer circle surface of the roller mold. The column 4-2 between two adjacent grooves on the guide plate 4 supports the billet. The column 4-2 effectively increases the rigidity of the guide plate 4 and ensures that the guide plate 4 provides sufficient support for the billet during the rolling process.

[0040] In one specific embodiment, the protruding edges of the first roller mold 1 and the second roller mold 2 are both provided with a top bevel angle ф at the tail end, with a value of 15-20°.

[0041] In one specific embodiment, ф is taken as 20°.

[0042] In one specific embodiment, two adjacent protrusions are inclined, with an included angle of 1°-3°.

[0043] This invention provides a two-roll multi-track parallel ball rolling process, which uses the aforementioned two-roll multi-track parallel ball rolling die and includes the following steps: S1. Adjust the distance between the first round roller mold 1 and the second round roller mold 2 so that the ball rolling track forms a complete circle with the same diameter as the target ball part at the end of the convex edge; S2. Place the cylindrical billet at the starting rolling position; S3. The first round roller mold 1 and the second round roller mold 2 rotate in the same direction and at the same speed. The cylindrical bar is squeezed and deformed in the ball rolling track formed by the protrusions of the first round roller mold 1 and the second round roller mold 2, and gradually rolled into a ball shape including a connecting neck, a ball platform, and a cylindrical part. Finally, the connecting neck is cut off and formed into multiple ball parts.

[0044] S4. The billet is pushed axially to begin the next rolling process.

[0045] By repeating S1-S4, an efficient ball rolling process can be achieved.

[0046] In one specific embodiment, the metal spheres obtained by conducting rolling experiments using the present invention are as follows: Figure 7 As shown in (c) and (d), in addition Figure 7 It also includes some other rolling methods for obtaining metal balls, such as Figure 7 As shown in (a) and (b); from Figure 7 It can be seen that the metal balls rolled using the method of this invention have no obvious scratches or overlapping skins, and also have a high degree of roundness.

[0047] The process is applicable to cold forming, hot forming, or warm forming of small-diameter steel balls with a diameter of 5mm-10mm.

[0048] This invention can roll multiple target parts at once, with considerable efficiency. The dual-roller, multi-track parallel ball rolling can meet the needs of rolling small spherical parts. The volume of each position on the die track is calculated, following the principle of volume conservation, which allows for more precise control of the volume of metal entering the track and the volume of the final formed ball.

[0049] While several embodiments of the present invention have been provided herein, those skilled in the art should understand that modifications can be made to these embodiments without departing from the spirit of the invention. The above embodiments are merely exemplary and should not be construed as limiting the scope of the invention.

Claims

1. A double roll multi-track parallel rolling ball mold characterized by, The mold comprises a first round roller mold and a second round roller mold; The first round roller mold comprises a plurality of ribs arranged side by side, all of which have the same starting position and ending position; the first rib in the middle is arranged along the circumference of the roller surface, and the other ribs on both sides of the first rib are arranged obliquely relative to the first rib; the height of each rib gradually increases, and a first half ball rolling track is formed between two adjacent ribs; the total width of all ribs at the rolling starting position is smaller than the total width of all ribs at the rolling completion position; The second round roller mold is provided with ribs corresponding to the first round roller mold, and a second half ball rolling track is formed between two adjacent ribs; The first half ball rolling track and the corresponding second half ball rolling track form a complete ball rolling track; when the round roller mold rotates, the cylindrical blank is gradually rolled into a plurality of ball parts by the plurality of ball rolling tracks formed by the first round roller mold and the second round roller mold.

2. The double roll multi-track parallel rolling ball mold according to claim 1, wherein The ball rolling track comprises a circular arc segment and a straight segment, the straight segment is located at the top and bottom of the ball rolling track, and the circular arc segment is located on both sides of the straight segment; from the rolling starting position to the rolling completion position, the length of the straight segment gradually decreases, and the length of the circular arc segment gradually increases; the blank is gradually extruded by the ribs to be rolled into a ball capsule shape comprising a connecting neck, a ball table and a cylindrical part; The connecting neck gradually becomes thin and long, the cylindrical part gradually becomes short to zero, and finally becomes a spherical part.

3. The double roll multi-track parallel rolling ball mold according to claim 2, wherein, The volume of the cylindrical blank entering the ball rolling track at the rolling starting position is equal to the volume of the ball part after rolling, which is approximately equal to the volume of the metal in the ball rolling track at any time during the rolling process plus the volume of the connecting neck; the volume conservation equation is as follows: ； ； ； ； ； ； In the formula, V is the volume of the cylindrical blank entering the ball rolling track, or the volume of the ball part after rolling; V1 and V5 are the volumes of the two half connecting necks, respectively; V3 is the volume of the cylindrical part; V2 and V4 are the volumes of the two ball tables, respectively; L0 represents the distance between the adjacent two ribs at the inlet; d represents the diameter of the blank, L represents the diameter of the connecting neck; b represents the length of the connecting neck, which is equal to the width of the top of the rib; h2 represents the height of the ball table; R represents the radius of the target ball; a represents the length of the straight segment.

4. The double roll multi-track parallel rolling ball mold according to claim 3, wherein The ball rolling track is specifically designed as follows: the ratio of the target ball diameter D to the rod diameter d is 105%-110%; the height of each rib linearly increases, and the length of the straight segment gradually decreases to 0; given the initial height, final height and initial top width of the rib, the values of the top width of the rib and the length of the straight segment at each section of the ball rolling track are obtained according to the volume conservation equation.

5. The double roll multi-track parallel rolling ball mold according to claim 1, wherein, At the rolling completion position, the rib height of the first round roller mold reaches the height of the ball center of the ball part, and the rib height of the second round roller mold is slightly lower than the height of the ball center of the ball part.

6. The double roll multi-track parallel rolling ball mold according to claim 1, wherein, A guide plate is arranged between the first round roller mold and the second round roller mold, and a stand for supporting the blank is arranged on the upper part of the guide plate.

7. The double roll multi-track parallel rolling ball mold according to claim 1, wherein, The top inclined angle ф of the rib of the first round roller mold and the second round roller mold is arranged at the tail section, and the value is 15-20°.

8. The double roll multi-track parallel rolling ball mold according to claim 1, wherein, The two adjacent ribs are arranged obliquely, and the included angle is 1°-3°.

9. A twin roll multi-track parallel rolling ball process characterized in that, The process uses the double-roller multi-track parallel rolling ball mold according to any one of claims 1-8, and the process comprises the following steps: S1, adjusting the distance between the first circular roller mold and the second circular roller mold, so that the rolling ball track forms a complete circle with the same diameter as the target spherical part at the end of the convex rib; S2, placing the cylindrical blank at the starting rolling position; S3, the first circular roller mold and the second circular roller mold rotate at the same speed in the same direction, and the cylindrical rod is extruded and deformed in the rolling ball track composed of the convex ribs of the first circular roller mold and the second circular roller mold, gradually rolled into a spherical capsule shape including a connecting neck, a spherical platform part, and a cylindrical part, and finally the connecting neck is cut off to form multiple spherical parts.

10. The twin roll multi-track parallel rolling ball process of claim 9, wherein, The process is suitable for cold forming, hot forming or warm forming of small-diameter steel balls with a diameter of 5-10 mm.

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