Plate-type parallel multi-roller-way bidirectional idle-stroke-free ball rolling mold and process

Abstract

The invention relates to the field of metal plastic forming processes and equipment, and provides a plate-type parallel multi-roller-way bidirectional idle-stroke-free ball rolling die and process. The die comprises an upper plate die and a lower plate die; the upper flat plate mold is provided with two groups of convex edges, and each group of convex edges comprises a plurality of convex edges arranged side by side; the first protruding edge located in the middle of the first set of protruding edges is arranged in the moving direction of the flat plate mold, and the other protruding edges on the two sides of the first protruding edge are obliquely arranged relative to the first protruding edge. The height of each rib is gradually increased; 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 group of ribs and the first group of ribs have the same structure and are arranged in opposite directions; and the lower flat plate mold is provided with two groups of convex edges corresponding to the upper flat plate mold. According to the invention, the volume of the blank for forming the ball is not changed in the rolling process, so that high-precision ball forming is realized; and the efficiency of the plate-type ball rolling method can be remarkably improved through two-way idle stroke-free rolling.

Description

Technical Field

[0001] This invention relates to the field of metal plastic forming processes and equipment, and in particular to a plate-type parallel multi-roller bidirectional empty stroke ball rolling die and process. Background Technology

[0002] Spherical parts are widely used in the machinery and chemical industries. Currently, production methods mainly focus on casting, forging, cold heading, and skew rolling. For small spherical parts, cold heading and rolling are the primary methods. Cold heading is a widely used spherical forming method, but it requires sophisticated equipment and consumes a large amount of molds. The smaller the sphere, the more difficult the cold heading process becomes, and the harder it is to improve production efficiency. Skew rolling offers high production efficiency, but the size of the formed sphere is limited by the guide plate, making it less suitable for smaller target sphere sizes. Therefore, a simple and feasible process for efficiently forming small-diameter spherical parts needs to be designed.

[0003] Plate rolling is a widely used metal forming process with relatively low forming technology difficulty. The rolling mill equipment is simple and easy to manufacture, and there are various die processing methods available for flat plates, including planing, milling, or laser processing, resulting in low die manufacturing costs. Traditional plate rolling processes involve two strokes, one push stroke and one return stroke. Often, the return stroke is an idle stroke, meaning that the power cannot be fully utilized for forming during the actual rolling process, which limits its production efficiency.

[0004] CN115446234A discloses a plate-type wedge cross-rolling die for spherical parts and a forming method thereof. The die is as follows: Figure 1 As shown. A plate wedge cross rolling process is used, but the following problems exist: Firstly, the starting positions of each roller table are different, especially at the start of rolling, the billet and die only contact at one point, making it difficult to maintain a stable billet position during rolling, causing the bar to skew after rolling begins; secondly, during the wedge cross rolling process, the billet material continuously flows outward axially, leading to incomplete metal filling in individual ball grooves and uneven metal flow, resulting in rolled balls that are not round or have missing material or scratches, as shown in the image. 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

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a plate-type parallel multi-roller bidirectional zero-empty stroke ball rolling die and process, which can more accurately control the volume of metal entering the track and the volume of the final formed ball. The rolling process can be realized in both the push stroke and the return stroke. Two sets of ball parts can be formed in one reciprocating motion of the die, which significantly improves the forming efficiency of plate rolling.

[0006] The present invention adopts the following technical solution: On the one hand, the present invention provides a plate-type parallel multi-roller bidirectional empty stroke ball rolling die, comprising upper and lower plate dies; The upper plate mold is provided with two sets of protruding ribs, each set of protruding ribs including multiple protruding ribs arranged side by side; All the protrusions in the first group have the same starting and ending positions; the first protrusion located in the middle is set along the movement direction of the flat die, and the other protrusions on both sides of the first protrusion are set at an inclination relative to the first protrusion; the height of each protrusion gradually increases, and the width of the top of each protrusion gradually increases, and an upper half rolling ball track is formed between two adjacent protrusions; the total width of all the protrusions at the rolling start position is less than the total width of all the protrusions at the rolling completion position. The second set of protruding ribs has the same structure as the first set of protruding ribs and is arranged side by side; the starting position of the second set of protruding ribs and the ending position of the first set of protruding ribs are at the same end, and the ending position of the second set of protruding ribs and the starting position of the first set of protruding ribs are at the other end. The lower plate mold is provided with two sets of protruding ribs corresponding to the upper plate mold. The two adjacent protruding ribs in each set form a lower half ball rolling roller track. The upper hemisphere track and the corresponding lower hemisphere track constitute a complete ball rolling roller track; A linear reciprocating motion is generated between the upper plate mold and the lower plate mold; during the forward stroke, the first cylindrical billet located at the rolling position of the first set of protrusions is gradually rolled into multiple spherical parts by the multiple ball rolling rollers formed by the first set of protrusions of the upper plate mold and the lower plate mold; during the backward stroke, the second cylindrical billet located at the rolling position of the second set of protrusions is gradually rolled into multiple spherical parts by the multiple ball rolling rollers formed by the second set of protrusions of the upper plate mold and the lower plate mold.

[0007] In addition to any of the possible implementations described above, another implementation is provided in which the ball rolling mill includes an arc segment and a straight segment, the straight segment being located at the top and bottom of the ball rolling mill, 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 cylindrical shape to being squeezed by the convex ridge, 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.

[0008] 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 mill at the starting position of rolling is equal to the volume of the metal in the ball rolling mill at any time during the rolling process plus the volume of the connecting neck, and is also equal to the volume of the spherical part after rolling; the volume conservation equation is as follows: ; ; ; ; ; In the formula, V is the volume of the cylindrical billet entering the ball rolling mill, or the volume of the spherical part after rolling; V1 and V5 are the volumes of the two semi-connecting necks; V3 is the volume of the cylindrical part; V2 and V4 are the volumes of the two ball platforms; 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. In addition to any of the possible implementations described above, another implementation is provided, wherein the ball rolling roller conveyor 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, the final height, and the 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 roller conveyor 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 upper plate die reaches the height of the center of the spherical part, and the height of the convex edge of the lower plate 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, another implementation is provided in which the first group of protruding ridges and the second group of protruding ridges are both provided with a top bevel angle ф at the tail section, with a value of 15-20°.

[0012] In addition to any of the possible implementations described above, another implementation is provided in which two adjacent protrusions are inclined with an included angle of 1°-3°.

[0013] In addition to any of the possible implementations described above, another implementation is provided in which the upper plate mold and the lower plate mold are configured to reciprocate horizontally or vertically.

[0014] In addition to any of the possible implementations described above, another implementation is provided in which the upper and lower plate molds can be laser-processed, which can be used to process micro-miniature parts molds, and the resulting molds can be used for forming micro-miniature spherical parts.

[0015] On the other hand, the present invention also provides a plate-type parallel multi-roller bidirectional zero-empty-stroke ball rolling process, wherein the process uses the above-mentioned plate-type parallel multi-roller bidirectional zero-empty-stroke ball rolling die, and the process includes: S1. Push-stroke rolling: The first cylindrical billet is placed in the push-stroke feed port. The upper plate die and the lower plate die move in opposite directions at the same speed. The first cylindrical billet is gradually rolled into a ball shape including a connecting neck, a ball platform, and a cylindrical part by the multiple ball rolling rollers formed by the first set of protrusions of the upper plate die and the lower plate die. Finally, the connecting neck is cut off and formed into multiple ball parts. S2, Return Rolling: The second cylindrical billet is placed at the return feed inlet. The upper and lower plate molds move in opposite directions at the same speed. The second cylindrical billet is gradually rolled into a spherical shape including a connecting neck, a ball platform, and a cylindrical part by multiple ball rolling rollers formed by the second set of protrusions of the upper and lower plate molds. Finally, the connecting neck is cut off, forming multiple spherical parts.

[0016] In addition to any of the possible implementations described above, a further implementation is provided in which the process is applicable to the cold forming of small-diameter steel balls with a diameter of 6 mm or less.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 5. The forming method can form multiple metal balls of the same size in one pass, with no idle stroke in both reciprocating directions, enabling continuous production. Production efficiency is considerable, and it is suitable for cold rolling small-diameter metal ball parts. Attached Figure Description

[0022] Figure 1 The diagram shows a structural schematic of a conventional wedge-type roll forming die.

[0023] Figure 2 The diagram shown is a schematic representation of the overall structure of a plate-type parallel multi-track bidirectional zero-empty-stroke ball rolling die according to an embodiment.

[0024] Figure 3 The image shown is a side view of the mold in the embodiment.

[0025] Figure 4 The diagram shown is a schematic of the arc-shaped groove on the mold surface used to form the sphere in the embodiment.

[0026] Figure 5 The diagram shown is a schematic diagram of the inclined plane angle designed on both sides of the convex tail of the mold in the embodiment.

[0027] Figure 6 The figure shows the volume composition of each part of a single cavity of the mold in the embodiment.

[0028] Figure 7 The image shows a comparison of photographs of metal balls obtained from experiments using different rolling methods.

[0029] In the diagram: 1-Upper flat plate mold; 2-Lower flat plate mold; 3-Cylindrical blank. Detailed Implementation

[0030] 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.

[0031] like Figure 2 , Figure 3 , Figure 4 As shown, an embodiment of the present invention provides a plate-type parallel multi-roller bidirectional zero-empty-stroke ball rolling die, comprising two upper and lower plate dies 1 and 2; The upper plate mold 1 is provided with two sets of protruding ribs, each set of protruding ribs including multiple protruding ribs arranged side by side; All the protrusions in the first group have the same starting and ending positions; the first protrusion located in the middle is set along the movement direction of the flat die, and the other protrusions on both sides of the first protrusion are set at an inclination relative to the first protrusion; the height of each protrusion gradually increases, and an upper half rolling ball track is formed between two adjacent protrusions; the total width of all the protrusions at the rolling start position is less than the total width of all the protrusions at the rolling completion position. The second set of protruding ribs has the same structure as the first set of protruding ribs and is arranged side by side; the starting position of the second set of protruding ribs and the ending position of the first set of protruding ribs are at the same end, and the ending position of the second set of protruding ribs and the starting position of the first set of protruding ribs are at the other end. The lower plate mold 2 is provided with two sets of protrusions corresponding to the upper plate mold, and the two adjacent protrusions in each set of protrusions form a lower half ball rolling roller track; The upper hemisphere track and the corresponding lower hemisphere track constitute a complete ball rolling roller track; The upper plate mold 1 and the lower plate mold 2 generate a linear reciprocating motion; during the forward stroke, the first cylindrical billet located at the rolling position of the first set of protrusions is gradually rolled into multiple spherical parts by the multiple ball rolling rollers formed by the first set of protrusions of the upper plate mold 1 and the lower plate mold 2; during the backward stroke, the second cylindrical billet located at the rolling position of the second set of protrusions is gradually rolled into multiple spherical parts by the multiple ball rolling rollers formed by the second set of protrusions of the upper plate mold and the lower plate mold.

[0032] In one specific embodiment, there are two mold driving methods: one is that the lower platen mold 2 is fixed and the upper platen mold 1 reciprocates; the other mold driving method is that the upper platen mold 1 and the lower platen mold 2 move in opposite directions at the same speed.

[0033] In one specific embodiment, such as Figure 6 As shown, the ball rolling mill includes an arc section and a straight section. The straight section is located at the top and bottom of the ball rolling mill, and the arc section is located on both sides of the straight section. From the starting position of rolling to the finishing position, the length of the straight section gradually decreases, and the length of the arc section gradually increases. The billet 3 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.

[0034] In one specific embodiment, the volume of the cylindrical billet entering the ball rolling mill at the initial rolling position is equal to the volume of metal in the ball rolling mill at any moment during the rolling process plus the volume of the connecting neck, and is also equal to the volume of the spherical part after rolling; the volume conservation equation is as follows: ; ; ; ; ; In the formula, V is the volume of the cylindrical billet entering the ball rolling mill, or the volume of the spherical part after rolling; V1 and V5 are the volumes of the two semi-connecting necks; V3 is the volume of the cylindrical part; V2 and V4 are the volumes of the two ball platforms; 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. In one specific embodiment, the ball rolling roller conveyor 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 top width of each convex ridge first narrows and then widens, while 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 values ​​of the top width of the convex ridge and the length of the straight section of each cross section of the ball rolling roller conveyor are obtained according to the volume conservation equation.

[0035] In one specific embodiment, at the rolling completion position, the height of the protrusion of the upper plate mold 1 reaches the height of the center of the spherical part, and the height of the protrusion of the lower plate mold 2 is slightly lower than the height of the center of the spherical part.

[0036] In one specific embodiment, such as Figure 5 As shown, both the first and second sets of protruding ridges have a top bevel angle ф at the tail section, with a value of 155-160°. This design ensures that the billet at the connection between the two balls can flow smoothly into the arc-shaped groove during the rolling process. Therefore, bevels with fixed angles are designed on both sides of the ridge. In one embodiment, the angle of the bevel increases as the plasticity of the metal decreases.

[0037] In one specific embodiment, two adjacent protrusions are inclined, with an included angle of 1°-3°.

[0038] In one specific embodiment, the termination positions of both the first set of protruding ridges and the second set of protruding ridges are provided with receiving grooves, such as... Figure 4 As shown.

[0039] In one specific embodiment, the upper plate mold and the lower plate mold are configured to reciprocate horizontally or vertically.

[0040] If the rolled part is a micro-sized ball, the arc-shaped groove on the surface of the flat die can be processed by laser. The processing cost is low, the method is simple and feasible, and the two dies produced have good consistency.

[0041] This invention provides a plate-type parallel multi-roller bidirectional zero-empty-stroke ball rolling process, wherein the process uses the aforementioned plate-type parallel multi-roller bidirectional zero-empty-stroke ball rolling die, and the process includes: S1. Push-stroke rolling: The first cylindrical billet is placed in the push-stroke feed port. The upper plate die and the lower plate die move in opposite directions at the same speed. The first cylindrical billet is gradually rolled into a ball shape including a connecting neck, a ball platform, and a cylindrical part by the multiple ball rolling rollers formed by the first set of protrusions of the upper plate die and the lower plate die. Finally, the connecting neck is cut off and formed into multiple ball parts. S2, Return Rolling: The second cylindrical billet is placed at the return feed inlet. The upper and lower plate molds move in opposite directions at the same speed. The second cylindrical billet is gradually rolled into a spherical shape including a connecting neck, a ball platform, and a cylindrical part by multiple ball rolling rollers formed by the second set of protrusions of the upper and lower plate molds. Finally, the connecting neck is cut off, forming multiple spherical parts.

[0042] 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 (a) and (b) also include some other rolling methods for obtaining metal balls; from Figure 7 It can be seen that the metal balls rolled using this invention have no obvious scratches or overlapping skins, and also have a high degree of roundness.

[0043] The process is applicable to the cold forming of small-diameter steel balls with a diameter of 6 mm or less.

[0044] This invention features a plate die with multiple rows of parallel raised ridges on its surface. Adjacent raised ridges form cavities to accommodate the billet, ensuring a consistent volume of metal within each cavity. This guarantees a constant volume of billet used to form the spheres during rolling, achieving high-precision sphere forming. The die is mounted on a plate rolling mill, and the billet is formed from a cylindrical bar into a sphere of the target diameter through the opposite movements of the upper and lower dies. Multiple cavities can be configured on the die, with corresponding cavities for the push and return strokes, enabling bidirectional, zero-gap rolling and significantly improving the efficiency of the plate rolling method. Furthermore, this plate rolling method utilizes a simple die structure with good consistency between the upper and lower dies, offering diverse processing options. It eliminates the need for specialized equipment, allowing for the rolling of multiple spheres in a single feed. It boasts advantages such as high production efficiency, high forming accuracy, and fewer processes, and can be used for near-net-shape rolling of spherical parts, reducing grinding allowances and thus saving materials.

[0045] 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 plate type parallel multi-roller two-way no-stroke rolling ball mold, characterized by, The mold comprises an upper plate mold and a lower plate mold; The upper plate mold is provided with two groups of convex ribs, each group of convex ribs comprising a plurality of convex ribs arranged side by side; All the convex ribs of the first group of convex ribs have the same starting position and ending position; a first convex rib located in the middle is arranged along the movement direction of the plate mold; the other convex ribs on both sides of the first convex rib are arranged obliquely relative to the first convex rib; the height of each convex rib gradually increases, and an upper half ball track is formed between adjacent two convex ribs; the total width of all the convex ribs at the starting position of rolling is smaller than the total width of all the convex ribs at the completion position of rolling; The second group of convex ribs has the same structure as the first group of convex ribs and is arranged side by side; the starting position of the second group of convex ribs and the ending position of the first group of convex ribs are located at the same end, and the ending position of the second group of convex ribs and the starting position of the first group of convex ribs are located at the other end; The lower plate mold is provided with two groups of convex ribs corresponding to the upper plate mold, and a lower half ball roller track is formed between adjacent two convex ribs of each group of convex ribs; The upper half ball track and the corresponding lower half ball track form a complete ball roller track; Linear reciprocating motion is generated between the upper plate mold and the lower plate mold; when moving forward, a first cylindrical blank located at the starting position of rolling of the first group of convex ribs is gradually rolled into a plurality of ball parts by a plurality of ball roller tracks formed by the first group of convex ribs of the upper plate mold and the lower plate mold; when moving backward, a second cylindrical blank located at the starting position of rolling of the second group of convex ribs is gradually rolled into a plurality of ball parts by a plurality of ball roller tracks formed by the second group of convex ribs of the upper plate mold and the lower plate mold.

2. The plate-type parallel multi-roller two-way no-stroke rolling ball mold according to claim 1, wherein The ball roller track comprises an arc segment and a straight segment; the straight segment is located at the top and bottom of the ball roller track, and the arc segment is located on both sides of the straight segment; from the starting position of rolling to the completion position of rolling, the length of the straight segment gradually decreases, and the length of the arc segment gradually increases; the blank is gradually extruded by the convex rib from a short cylindrical shape into a ball capsule shape comprising a connecting neck, a ball table and a cylindrical part; The connecting neck gradually becomes thin and long, and the cylindrical part gradually becomes short to zero, finally becoming a spherical part.

3. The plate-type parallel multi-roller two-way no-stroke rolling ball mold according to claim 2, wherein The volume of the cylindrical blank entering the ball roller track at the starting position of rolling is equal to the volume of the metal in the ball roller track at any time during rolling plus the volume of the connecting neck, and also equal to the volume of the ball part after rolling; the volume conservation equation is as follows: ； ； ； ； ； In the formula, V is the volume of the cylindrical blank entering the ball roller track, or the volume of the ball part after rolling; V1 and V5 are the volumes of two half connecting necks, respectively; V3 is the volume of the cylindrical part; V2 and V4 are the volumes of two ball tables, respectively; L0 represents the distance between adjacent two convex ribs at the feeding port; 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 convex rib; h2 represents the height of the ball table; R represents the radius of the target ball; and a represents the length of the straight segment.

4. The plate-type parallel multi-roller two-way no-stroke rolling ball mold according to claim 2, wherein The ratio of the target ball diameter D to the bar diameter d is 105%-110%, the height of each ridge linearly increases, and the length of the flat section gradually decreases to 0; given the initial height, the final height, and the initial top width of the ridge, the values of the top width of the ridge and the length of the flat section of each section of the ball rolling roller are obtained according to the volume conservation equation.

5. The plate-type parallel multi-roller two-way no-gap rolling ball mold according to claim 1, wherein At the rolling completion position, the ridge height of the upper flat die reaches the ball center height of the spherical part, and the ridge height of the lower flat die is slightly lower than the ball center height of the spherical part.

6. The plate-type parallel multi-stand double-strand no-idling rolling ball mold according to claim 1, wherein The first group of ridges and the second group of ridges are provided with a top inclined angle ф of 15-20° at the tail section.

7. The plate-type parallel multi-roller bidirectional no-stroke rolling ball mold according to claim 1, wherein Two adjacent ridges are inclinedly arranged, and the included angle is 1°-3°.

8. The plate-type parallel multi-stand double-strand no-idling rolling ball mold according to claim 1, wherein The upper flat die and the lower flat die are arranged to horizontally reciprocate or vertically reciprocate.

9. A plate-type parallel multi-roller two-way no-gap rolling ball process, characterized by, The process uses the plate-type parallel multi-roller two-way no-empty-stroke ball rolling die according to any one of claims 1-8, and the process comprises: S1, forward rolling: a first cylindrical blank is placed at the forward feeding port, the upper flat die and the lower flat die move at the same speed in opposite directions, and the first cylindrical blank is gradually rolled into a spherical capsule shape including a connecting neck, a spherical platform, and a cylindrical part by a plurality of ball rolling rollers formed by the first group of ridges of the upper flat die and the lower flat die, and finally the connecting neck is cut off to form a plurality of spherical parts; S2, back rolling: a second cylindrical blank is placed at the back feeding port, the upper flat die and the lower flat die move at the same speed in opposite directions, and the second cylindrical blank is gradually rolled into a spherical capsule shape including a connecting neck, a spherical platform, and a cylindrical part by a plurality of ball rolling rollers formed by the second group of ridges of the upper flat die and the lower flat die, and finally the connecting neck is cut off to form a plurality of spherical parts.

10. The plate-type parallel multi-stand bidirectional no-gap rolling ball process according to claim 9, wherein, The process is suitable for cold forming of small-diameter steel balls with a diameter of 6 mm or less.

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