One-time extrusion forming tool and its design method

Abstract

The present application discloses a one-time extrusion forming tool and its design method. The extrusion head assembly is arranged in the installation channel, and the installation position of the cylindrical pin in the installation channel is adjustable, and the extrusion head is exposed from the installation channel. The degree to which the extrusion head protrudes from the installation channel increases from the first turn to the last turn on the preset spiral track. The one-time extrusion forming tool and its design method provided by the present invention, through the structural design of the one-time extrusion forming tool, take the working part as the main part, and the extrusion head assembly is spirally arranged on the working part. The degree to which the extrusion head protrudes from the installation channel increases from the first turn to the last turn on the preset spiral track. When the one-time extrusion forming tool contacts the nut blank, the rotation and downward pressing movements can smoothly perform the one-time extrusion forming process. The extrusion process is from shallow to deep, which not only ensures the forming accuracy but also improves the efficiency. The processing of the inner raceway of the lead screw nut can be completed only by one extrusion.

Description

Technical Field

[0001] The present invention relates to the field of screw nut processing devices, and particularly relates to a one-time extrusion forming tool and its design method. Background Art

[0002] The extrusion forming technology utilizes the principle of metal plastic deformation, that is, the volume of the metal extruded by the tool extrusion head is equal to the volume of the metal formed after plastic deformation, and it is a chip-free processing technology. This technology is applicable to alloys with relatively low strength and good plasticity and is often used for the processing of internal threads.

[0003] In recent years, due to the increasing demand for high-speed feeding, the demand for large-lead screw nut pairs has also gradually increased, and the extrusion forming technology has gradually been applied to the processing of the internal raceways of large-lead screw nuts.

[0004] In the prior art, a single extrusion head is mostly used to repeatedly extrude the inner hole of the screw nut blank to form the required spiral raceway. However, the method of using a single extrusion head has extremely strict requirements. If there are deviations (failures) in the size of the extrusion head itself or deviations (failures) occur due to repeated extrusion; specifically, if the size of the extrusion head is too small, the volume of the metal that undergoes plastic deformation will be small, and the filling of the raceway will be incomplete; when the size of the extrusion head is too large, the volume of the metal that causes plastic deformation will increase, which will result in a loose fit between the screw nut and the screw, affecting the transmission accuracy. In addition to the problems in processing dimensional accuracy, when the extrusion amount is too large, it will also lead to excessive local resistance, resulting in a very large amount of instantaneous heat generated, which will not only reduce the tool life but also damage the processed material. Summary of the Invention

[0005] The main object of the present invention is to provide a one-time extrusion forming tool and its design method, aiming to solve the problems that in the process of extruding and forming screw nuts, in addition to the problems in processing dimensional accuracy, when the extrusion amount is too large, it will also lead to excessive local resistance, resulting in a very large amount of instantaneous heat generated, which will not only reduce the tool life but also damage the processed material.

[0006] To achieve the above object, the present invention provides a one-time extrusion forming tool for processing the internal raceway of a screw nut, including:

[0007] A working part, which is columnar. A plurality of installation channels are arranged on the outer wall of the working part in a preset spiral trajectory. The installation channels are arranged along the radial direction of the working part. Among them, at least one installation channel is provided on each circle of the preset spiral trajectory;

[0008] A plurality of extrusion head assemblies are arranged in the installation channels. The extrusion head assembly includes a cylindrical pin and an extrusion head. The installation position of the cylindrical pin in the installation channel is adjustable, and the extrusion head is exposed outside the installation channel;

[0009] Among them, the degree to which the extrusion head protrudes from the installation channel increases from the first turn to the last turn on the preset spiral track.

[0010] Furthermore, at least three installation channels are provided on each turn of the preset spiral track.

[0011] Furthermore, the installation channel is a through hole.

[0012] Furthermore, the installation channel includes a smooth section and a threaded section connected to each other. Among them, the extrusion head is installed in the smooth section, and the cylindrical pin is threadedly connected to the threaded section.

[0013] Furthermore, the primary extrusion forming tool further includes a clamping part and a calibration part; the calibration part is columnar and is used to calibrate the roundness of the primary extrusion forming tool and improve the coaxiality during use; the cross-section of the clamping part is an arched rectangle with opposite sides being arc-shaped;

[0014] Among them, the calibration part is connected to both ends in the length direction of the working part, and the clamping part is connected to the free end of the calibration part.

[0015] Furthermore, the increasing degree of the extrusion head on each turn of the preset spiral track is selected from a linear rising trend, a stepped linear rising trend, an exponential rising trend, or a logarithmic rising trend.

[0016] The present invention also provides a design method, which is applied to the above-mentioned primary extrusion forming tool and includes

[0017] S1. Collect the nut raceway parameters of the lead screw nut;

[0018] S2. Determine the external dimensions of the working part according to the nut raceway parameters;

[0019] S3. Establish the spiral raceway profile equation of the lead screw nut according to the nut raceway parameters;

[0020] S4. Establish the calculation equation of the nut forming tool profile parameters, calculate the extrusion head profile parameters, and complete the design of the primary extrusion forming tool.

[0021] Furthermore, in the step of S1, the nut raceway parameters include the contact angle α , nominal diameter d m , nut inner diameter d 0 , ball diameter d b , raceway radius R、 lead P z , helix angle λAnd the circular arc eccentricity e ;

[0022] The steps of S3 include:

[0023] Establish a normal section coordinate system (o'-x'y'z') with the center of the ball as the origin, establish a workpiece coordinate system (o-xyz) with the axis of the lead screw nut as the z-axis, and determine the transformation matrix for transforming from the normal section coordinate system to the workpiece coordinate system, , where, θ is the movement angle of the center of the ball relative to the central axis of the lead screw nut, 0 ≤ θ ≤ 2π, r m is the nominal radius, , p is nut helix parameter, ; Establish the surface equation of the nut helix raceway in the normal section coordinate system, , where, z m The "-" sign before μ represents the right circular arc, and the "+" sign represents the left circular arc; is the raceway circular arc angle; Through the transformation matrix, establish the surface equation of the nut helix raceway in the workpiece coordinate system, .

[0024] Furthermore, the steps of S4 include:

[0025] S4. Establish the calculation equation for the surface parameters of the nut forming tool. The surface of the s-th extrusion head on the t-th turn of the one-time extrusion forming tool is expressed as,

[0026] where, 0 ≤ μ ≤ π / 2, 0 ≤ θ ≤ 2π, 0 < t ≤ T, 0 < s ≤ S, T is the number of turns of the preset spiral trajectory, S is the number of extrusion heads on each turn of the preset spiral trajectory,

[0027] Calculate the surface parameters of the extrusion head to complete the design of the one-time extrusion forming tool.

[0028] Furthermore, the one-time extrusion forming tool further includes a clamping part and a calibration part. The calibration part is columnar and is used to calibrate the roundness of the one-time extrusion forming tool and improve the coaxiality during use. The cross-section of the clamping part is an arched rectangle with opposite sides being arc-shaped. The calibration part is connected to both ends in the length direction of the working part, and the clamping part is connected to the free end of the calibration part;

[0029] The design method further includes:

[0030] Design the specific parameters of the calibration part and the clamping part to complete the design of the entire tool.

[0031] The one-time extrusion forming tool and its design method provided by the present invention, through the structural design of the one-time extrusion forming tool, use the working part as the main part, and helically arrange the extrusion head assembly on the working part. The degree to which the extrusion head protrudes from the installation channel increases from the first turn to the last turn on the preset spiral trajectory. When the one-time extrusion forming tool contacts the nut blank, the rotation and downward pressing movements can smoothly perform the one-time extrusion forming process. Through the above structural design, the surface shapes and arrangement methods of multiple extrusion heads cause metal plastic flow along the arc surface of the extrusion head, and finally form a spiral inner raceway. The extrusion process is from shallow to deep, which not only ensures the forming accuracy but also improves the efficiency. The processing of the inner raceway of the lead screw nut can be completed only by one extrusion. Brief Description of the Drawings

[0032] Figure 1 is a schematic diagram of the one-time extrusion forming tool according to an embodiment of the present invention;

[0033] Figure 2 is a partial schematic diagram of the one-time extrusion forming tool according to an embodiment of the present invention;

[0034] Figure 3 is a schematic diagram of the lead screw nut parameters (the first part);

[0035] Figure 4 is a schematic diagram of the lead screw nut parameters (the second part);

[0036] Figure 5 is a schematic diagram of the normal section coordinate system and the workpiece coordinate system in the one-time extrusion forming tool according to an embodiment of the present invention.

[0037] The realization, functional characteristics and advantages of the object of the present invention will be further described with reference to the embodiments and the accompanying drawings. Detailed Embodiments

[0038] It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0039] Those skilled in the art can understand that, unless specifically stated otherwise, the singular forms "a", "an", "the", "above-mentioned" and "said" used herein may also include the plural forms. It should be further understood that the term "comprising" used in the specification of the present invention means the presence of the described features, integers, steps, operations, elements, units, modules and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, units, modules, components and / or their groups. It should be understood that when we say that an element is "connected" or "coupled" to another element, it can be directly connected or coupled to other elements, or there may also be intermediate elements. In addition, the "connection" or "coupling" used herein may include wireless connection or wireless coupling. The phrase "and / or" used herein includes all or any unit and all combinations of one or more associated listed items.

[0040] Those skilled in the art can understand that, unless otherwise defined, all terms used herein (including technical terms and scientific terms) have the same meaning as the general understanding of those of ordinary skill in the art to which the present invention belongs. It should also be understood that terms such as those defined in a general dictionary should be understood to have a meaning consistent with the meaning in the context of the prior art, and will not be interpreted with an idealized or overly formal meaning unless specifically defined as here.

[0041] Referring to Figures 1 to 5 , in an embodiment of the present invention, a one-time extrusion forming tool includes:

[0042] A working part 3, which is columnar. A plurality of installation channels 11 are arranged on the outer wall of the working part 3 in a preset spiral trajectory. The installation channels 11 are arranged along the radial direction of the working part 3. Wherein, at least one installation channel 11 is arranged on each circle of the preset spiral trajectory;

[0043] A plurality of extrusion head assemblies are arranged in the installation channels 11. The extrusion head assembly includes a cylindrical pin 12 and an extrusion head. The installation position of the cylindrical pin 12 in the installation channel 11 is adjustable, and the extrusion head is exposed out of the installation channel 11;

[0044] Wherein, the degree to which the extrusion head protrudes out of the installation channel 11 increases from the first circle to the last circle on the preset spiral trajectory.

[0045] In the prior art, in addition to the problems in terms of machining dimensional accuracy in the extrusion forming technology, when the extrusion amount is too large, it will also cause too large local resistance, resulting in a very large amount of heat generated instantaneously, which will not only reduce the tool life, but also cause damage to the processed material.

[0046] In the present invention, the extrusion head is a carbide steel ball, which is embedded in the installation channel 11 of the working part 3. When the primary extrusion forming tool rotates, the embedded extrusion head completes the primary extrusion forming of the inner raceway of the lead screw nut (especially the large lead).

[0047] It is necessary to determine the nut raceway parameters of the lead screw nut; then determine the outer dimensions of the working part based on the nut raceway parameters; establish the spiral raceway profile equation of the lead screw nut based on the nut raceway parameters; establish the nut forming tool profile parameter calculation equation, calculate the tool extrusion head profile parameters, and complete the extrusion forming tool design. In the specific process, the diameter size D of the working part 3 is determined by the inner hole of the extruded nut blank. According to the needs, the model of the lead screw nut 010 is processed, the lead Pz of the lead screw nut 010, the number and size of the extrusion head are confirmed, and the extrusion depth H that the extrusion head needs to reach is determined. The protrusion of the last circle of the extrusion head is determined by the extrusion depth H, which is also H. H is divided into T equal parts, and the protrusion of each circle or the protrusion increased by each circle is calculated, so as to arrange the depth of the extrusion head.

[0048] For example, in this one-time extrusion forming tool, 48 extrusion heads are embedded in the working part 3 in 16 rows with 3 in each circle. Assuming that the nominal diameter of the nut to be extruded is 32mm and the lead is 32mm, the spacing of the steel balls embedded in the same circle on the tool axis is 10.67mm. Then, through the nut forming tool profile, the protrusion of each circle of extrusion heads can be calculated.

[0049] During the installation of the extrusion head assembly, the extrusion head and the mounting channel 11 are slightly interference fit. First, drill an inlay hole on the working part 3 to embed the extrusion head. Rotate the working part 3 180° and drill a threaded hole with a diameter of M5 at the symmetrical position. The inlay hole and the threaded hole together constitute the mounting channel 11. When adjusting the embedding depth of the extrusion head, first insert the cylindrical pin 12, use the M5 set screw to support the middle cylindrical pin 12, and the other side of the cylindrical pin 12 contacts the extrusion head, so as to adjust the embedding depth of the extrusion head. The overall shape of the specific extrusion head is preferably spherical, but is not limited to a spherical shape; for example, the working part of the extrusion head (i.e., the extrusion part) meets the profile design, while other parts are adaptive structural designs.

[0050] During use, when the one-time extrusion forming tool is stretched to the highest limit, the nut blank is placed on the workpiece table of the equipment, the cylinder is controlled to slowly descend, and the one-time extrusion forming tool passes through the inner hole of the nut blank, passes through the workpiece table component, and is connected to the tool pull-down column, and the pull-down column is connected to the pull-down beam. The servo motor is controlled to start, the one-time extrusion forming tool moves downward, and when the extrusion head embedded in the one-time extrusion forming tool contacts the inner side of the nut blank, the turntable servo motor starts, the spindle rotates, and the claw clamps the nut to start the one-time extrusion forming process.

[0051] In summary, through the structural design of the one - time extrusion forming tool, with the working part 3 as the main body part, and the extrusion head assembly is spirally arranged on the working part 3. The degree to which the extrusion head protrudes from the installation channel 11 increases from the first turn to the last turn on the preset spiral track. When the one - time extrusion forming tool contacts the nut blank, by rotating and pressing down, the one - time extrusion forming process can be smoothly carried out. Through the above structural design, the profile and arrangement of multiple extrusion heads cause metal plastic flow along the arc surface of the extrusion head, and finally form a spiral inner raceway. The extrusion process is from shallow to deep, which not only ensures the forming accuracy but also improves the efficiency. The processing of the inner raceway of the lead screw nut can be completed with only one extrusion.

[0052] In one embodiment, at least three installation channels 11 are provided on each turn of the preset spiral track.

[0053] In this embodiment, when the number of installation channels 11 provided on each turn of the preset spiral track increases, while the force required for a single extrusion head assembly decreases, it can provide a self - centering effect for the entire one - time extrusion forming tool.

[0054] In one embodiment, the installation channel 11 is a through - hole.

[0055] In the foregoing embodiment, the installation channel 11 is not limited to being a through - hole. When it is a blind hole, the position of the cylindrical pin 12 is adjusted first, and then the extrusion head is installed. In this embodiment, since the installation channel 11 is a through - hole, the height of the extrusion head can still be adjusted from the back after the whole installation.

[0056] In one embodiment, the installation channel 11 includes a smooth section and a threaded section connected to each other. Among them, the extrusion head is installed in the smooth section, and the cylindrical pin 12 is threadedly connected to the threaded section.

[0057] In this embodiment, a convenient fixing method for the extrusion head and the cylindrical pin 12 is provided. While meeting the functions, the structure and operation are relatively simple.

[0058] In one embodiment, the one - time extrusion forming tool further includes a clamping part 1 and a calibration part 2; the calibration part 2 is column - shaped and is used to calibrate the roundness of the one - time extrusion forming tool and improve the coaxiality during use; the cross - section of the clamping part 1 is an arched rectangle with opposite sides being arc - shaped;

[0059] Among them, the calibration part 2 is connected to both ends of the working part 3 in the length direction, and the clamping part 1 is connected to the free end of the calibration part 2.

[0060] In this embodiment, half of the clamping portion 1 is designed in a square shape and half in an arc shape, and the clamping portion 1 as a whole is designed in a quadrilateral shape. The non-circular design is adopted to transmit the continuous extrusion force to the clamping portion 1 in an intermittent form, effectively reducing the force on the clamping portion 1, thereby enhancing the connection stiffness between the primary extrusion forming tool and the outside and the service life of the primary extrusion forming tool itself.

[0061] The size of the square design of the clamping portion 1 can be the same as the size of the direction groove inside the tool locking mechanism, which plays a guiding role during the movement of the primary extrusion forming tool.

[0062] The calibration portion 2 is mainly used to correct the coaxiality of the primary extrusion forming tool passing through the nut blank. The calibration portion 2 is located in the middle of the working portion 3 and the clamping portion 1, and its diameter is smaller than that of the working portion 3 and larger than that of the clamping portion 1. According to the different diameters of the extruded inner holes, it is usually located at the average value of the two diameters. The length of the calibration portion 2 is usually 5 - 10 mm.

[0063] In one embodiment, the degree of increase of the extrusion head on each circle of the preset spiral trajectory is selected from a linear upward trend, a stepped linear upward trend, an exponential upward trend, or a logarithmic upward trend.

[0064] In this embodiment, the form of the increase in the protruding degree of the extrusion head along the length direction of the working portion 3 is specifically described.

[0065] In the linear upward trend, the protruding amount of the extrusion head in the current circle of the preset spiral trajectory is increased by a fixed value compared with the previous circle.

[0066] In the stepped linear upward trend, all circles of the preset spiral trajectory are divided into several connected groups. In the current group, the protruding amount of the extrusion head is increased by a fixed value compared with the previous group.

[0067] In the exponential upward trend or the logarithmic upward trend, the increase in the protruding amount of adjacent circles of the preset spiral trajectory satisfies the corresponding exponential curve relationship or logarithmic curve relationship. It should be noted that when it is a logarithmic upward trend, it is beneficial, that is, in the previous stage of the processing, processing with a larger deformation amount is carried out, and in the later stage of the processing, processing with a smaller deformation amount is carried out to meet the final processing accuracy.

[0068] The present invention also provides a design method, which is applied to the above-mentioned primary extrusion forming tool and includes

[0069] S1. Collect the nut raceway parameters of the lead screw nut;

[0070] S2. Determine the outer shape dimensions of the working portion according to the nut raceway parameters;

[0071] S3. Establish the spiral raceway profile equation of the lead screw nut according to the nut raceway parameters;

[0072] S4. Establish the calculation equation for the profile parameters of the nut forming tool, calculate the profile parameters of the extrusion head, and complete the design of the primary extrusion forming tool.

[0073] In this embodiment, in the step of S1, the relevant nut raceway parameters include the normal profile, contact angle α、 nominal diameter d m 、 nut inner diameter d 0 、 raceway radius R 、 lead P z 、 helix angle λ 、 arc eccentricity e、 Horizontal eccentricity and vertical eccentricity, etc. Through the above parameters, the most important thing is to calculate and establish the spiral raceway profile equation of the ball screw nut and the calculation equation for the profile parameters of the nut forming tool.

[0074] Normal profile: The profile obtained by intersecting the normal section of the helix passing through the center of the ball 030 with the ball screw 020 and the spiral raceway of the ball screw nut. The commonly used normal profiles are single circular arc and double circular arc.

[0075] contact angle α : In the normal section of the ball screw 020, the angle between the line connecting the center of the ball 030 and the contact point of the ball 030 on the raceway and the symmetry line of the section. The contact angle is usually taken as 45 degrees.

[0076] nominal diameter d m : In the case of a 45-degree contact angle between the ball 030 and the spiral groove of the ball screw 020 or the ball screw nut, the diameter of the cylinder passing through the center of the ball 030. The nominal diameter of the ball screw 020 is both the nominal diameter of the ball screw nut and the ball screw.

[0077] nut inner diameter d 0 : The diameter of the inner wall of the screw nut 010.

[0078] ball diameter d b : The diameter of the ball.

[0079] raceway radius R : The radius of the arc in the normal section of the spiral raceway.

[0080] lead P z : The distance that the nut moves relative to the screw after rotating one circle relative to the screw.

[0081] Helical lift angle λ : The angle between the tangent of the helix on the cylinder with the nominal diameter d m and the end section of the cylinder. Its calculation formula is: ,

[0082] Arc eccentricity e : The distance between the center of the raceway arc and the center of the ball 030. Its calculation formula is: ,

[0083] Horizontal eccentricity ,

[0084] Vertical eccentricity ,

[0085] When the contact angle is 45 degrees, e H = e V ,

[0086] Raceway arc angle μ : Parameter variable.

[0087] In step S2, according to the nut raceway parameters, determine the external dimensions of the working part, specifically including the diameter and length.

[0088] In step S3, according to the nut raceway parameters, establish the spiral raceway profile equation of the lead screw nut.

[0089] The connection line of the centers of the balls 030 in the inner raceway of the nut is a cylindrical helix. Establish a normal section coordinate system (o'-x'y'z') with the center of the ball 030 as the origin, and establish a workpiece coordinate system (o-xyz) with the axis of the lead screw nut as the z-axis. The transformation matrix from the normal section coordinate system to the workpiece coordinate system is: , where θ is the movement angle of the center of the ball 030 relative to the central axis of the lead screw nut, 0 ≤ θ ≤ 2π; r m is the nominal radius, ; p is Nut helix parameter, ; In the normal section coordinate system, the profile equation of the nut spiral raceway is, , 0 ≤ μ ≤ π / 2; where z m The "-" sign before indicates the right arc, and the "+" sign indicates the left arc. For a single arc raceway, select according to the actually contacted arc segment; for a double arc raceway, since the left and right arc segments are symmetric, only the right arc needs to be discussed.

[0090] Transforming the profile on the normal section coordinate system to the workpiece coordinate system, the profile equation of the nut spiral raceway can be obtained as follows: .

[0091] In the step of S4, since it is a one-time extrusion forming, it is required that the nut spiral raceway profile completely corresponds to the tool raceway profile. It can be considered that the workpiece coordinate system and the tool coordinate system completely coincide. Only the extrusion head on the one-time extrusion forming tool contacts the nut blank, and only the profile of the extrusion head needs to be expressed.

[0092] Suppose there are S extrusion heads on each turn of the spiral raceway of the one-time extrusion forming tool (S is generally taken as 3 to achieve the self-centering effect), and the protrusion amount of the extrusion heads on each turn of the raceway is the same. There are T turns of the tool raceway, so the total number of extrusion heads on the one-time extrusion forming tool is S×T. The distance between each turn of the extrusion heads is the lead Pz. The spacing of the extrusion heads on the axis of the one-time extrusion forming tool on the same turn is Pz / S.

[0093] Suppose the final raceway depth of the nut is H (on the normal section), then H = d b / 2 - ( d m - d 0 ), with e = R - d b / 2, then the eccentricity e can be expressed in terms of H, e = R - H + - d 0 - d m .

[0094] The protrusion amount of the last extrusion head on the one-time extrusion forming tool is also H.

[0095] H can be divided into T equal parts. The protrusion amount of each ring of the extrusion head increases by H / T compared to the previous ring, and the protrusion amount of each ring of the extrusion head increases at equal intervals. It can also increase according to different intervals. In short, H can be regarded as a function of t, denoted as H(t). The increase degree of the extrusion head on each ring of the preset spiral trajectory is selected from a linear upward trend, a stepped linear upward trend, an exponential upward trend, or a logarithmic upward trend. In the linear upward trend, the protrusion amount of the extrusion head in the preset spiral trajectory of the current ring is increased by a fixed value compared to the previous ring. In the stepped linear upward trend, the preset spiral trajectories of all rings are divided into several connected groups. In the current group, the protrusion amount of the extrusion head is increased by a fixed value compared to the previous group. In the exponential upward trend or the logarithmic upward trend, the increase in the protrusion amount of the preset spiral trajectories of adjacent rings satisfies the corresponding exponential curve relationship or logarithmic curve relationship. It should be noted that when it is a logarithmic upward trend, it is beneficial, that is, in the previous processing process, processing with a larger deformation amount is performed, and in the subsequent processing process, processing with a smaller deformation amount is performed to meet the final processing accuracy.

[0096] Then, the profile of the s-th extrusion head on the t-th ring of the one-time extrusion forming tool is expressed as:

[0097] where 0 ≤ μ ≤ π / 2, 0 ≤ θ ≤ 2π, 0 < t ≤ T, 0 < s ≤ S, and both s and t are integers.

[0098] According to the above profile equation, the profile of each extrusion head on the one-time extrusion forming tool can be designed.

[0099] In one embodiment, the steps of S3 include:

[0100] Establish a normal section coordinate system (o'-x'y'z') with the center of the ball of the ball 030 as the origin, establish a workpiece coordinate system (o-xyz) with the axis of the lead screw nut as the z-axis, and determine the transformation matrix from the normal section coordinate system to the workpiece coordinate system. ; Establish the profile equation of the nut spiral raceway in the normal section coordinate system. ; Through the transformation matrix, establish the profile equation of the nut spiral raceway in the workpiece coordinate system. .

[0101] In this embodiment, the connection line of the centers of the balls of the balls 030 in the inner raceway of the nut is a cylindrical helix. Establish a normal section coordinate system (o'-x'y'z') with the center of the ball of the ball 030 as the origin, and establish a workpiece coordinate system (o-xyz) with the axis of the lead screw nut as the z-axis. The transformation matrix from the normal section coordinate system to the workpiece coordinate system is: , where θ is the movement angle of the center of the ball relative to the central axis of the lead screw nut, 0 ≤ θ ≤ 2π; r mis the nominal radius, ; p is nut helix parameter, ; In the normal section coordinate system, the surface equation of the nut helical raceway is,[[]] , 0 ≤ μ ≤ π / 2, where z m The "-" sign before

[0102] Transforming the surface on the normal section coordinate system to the workpiece coordinate system, the surface equation of the nut helical raceway can be obtained as: .

[0103] In one embodiment, the steps of S4 include:

[0104] S4. Establish the calculation equation for the surface parameters of the nut forming tool. The surface of the s-th extrusion head on the t-th turn of the single-pass extrusion tool is expressed as,

[0105] where, 0 ≤ μ ≤ π / 2, 0 ≤ θ ≤ 2π, 0 < t ≤ T, 0 < s ≤ S, T is the number of turns of the preset spiral trajectory, S is the number of extrusion heads on each turn of the preset spiral trajectory,

[0106] Calculate the surface parameters of the extrusion head to complete the design of the single-pass extrusion tool.

[0107] In this embodiment, in the steps of S4, since it is a single-pass extrusion forming, it is required that the surface of the nut helical raceway corresponds exactly to the surface of the tool raceway. It can be considered that the workpiece coordinate system coincides exactly with the tool coordinate system. Only the extrusion heads on the single-pass extrusion tool contact the nut blank, and only the surface of the extrusion heads needs to be expressed.

[0108] Assume that there are S extrusion heads on each turn of the helical raceway of the single-pass extrusion tool (S is generally taken as 3 to achieve the self-centering effect), and the protrusion amount of the extrusion heads on each turn of the raceway is the same. There are T turns of the tool raceway, so the total number of extrusion heads on the single-pass extrusion tool is S×T. The distance between the extrusion heads on each turn is the lead Pz. The spacing of the extrusion heads on the axis of the single-pass extrusion tool on the same turn is Pz / S.

[0109] Assume that the final depth of the nut raceway is H (in the normal section), then H = d b / 2 - ( d m - d 0 ), since e = R - d b / 2, then the eccentricity e can be expressed in terms of H, e = R - H ± d 0 - d m 。

[0110] The protrusion amount of the last extrusion head on the one-time extrusion forming tool is also H.

[0111] H can be divided into T equal parts. The protrusion amount of each circle of extrusion heads increases by H / T compared to the previous circle, and the protrusion amount of each circle of extrusion heads increases at equal intervals. It can also increase according to different intervals. In short, H can be considered as a function of t, denoted as H(t). The increase degree of the extrusion heads on each circle of the preset spiral trajectory is selected from a linear upward trend, a stepped linear upward trend, an exponential upward trend, or a logarithmic upward trend. In the linear upward trend, the protrusion amount of the extrusion heads in the current circle of the preset spiral trajectory is increased by a fixed value compared to the previous circle. In the stepped linear upward trend, all circles of the preset spiral trajectory are divided into several connected groups. In the current group, the protrusion amount of the extrusion heads is increased by a fixed value compared to the previous group. In the exponential upward trend or the logarithmic upward trend, the increase in the protrusion amount of adjacent circles of the preset spiral trajectory satisfies the corresponding exponential curve relationship or logarithmic curve relationship. It should be noted that when it is a logarithmic upward trend, it is beneficial, that is, in the previous stage of the processing process, processing with a larger deformation amount is carried out, and in the later stage of the processing process, processing with a smaller deformation amount is carried out to meet the final processing accuracy.

[0112] Then the profile of the s-th extrusion head on the t-th circle of the one-time extrusion forming tool is expressed as:

[0113] where 0 ≤ μ ≤ π / 2, 0 ≤ θ ≤ 2π, 0 < t ≤ T, 0 < s ≤ S, and both s and t are integers.

[0114] In one embodiment, the one-time extrusion forming tool further includes a clamping part 1 and a calibration part 2. The calibration part 2 is columnar and is used to calibrate the roundness of the one-time extrusion forming tool and improve the coaxiality during use. The cross-section of the clamping part 1 is an arched rectangle with opposite sides being arc-shaped. The calibration part 2 is connected to both ends in the length direction of the working part 3, and the clamping part 1 is connected to the free end of the calibration part 2;

[0115] The design method further includes:

[0116] Design the specific parameters of the calibration part 2 and the clamping part 1 to complete the design of the entire tool.

[0117] The one-time extrusion forming tool and its design method provided by the present invention, through the structural design of the one-time extrusion forming tool, take the working part as the main part, and a extrusion head assembly is spirally arranged on the working part. The degree to which the extrusion head protrudes from the installation channel increases from the first turn to the last turn on the preset spiral track. When the one-time extrusion forming tool contacts the nut blank, the rotation and downward pressing movements can smoothly carry out the one-time extrusion forming process. Through the above structural design, the surface shapes and arrangement modes of multiple extrusion heads cause metal plastic flow along the arc surface of the extrusion head, and finally form a spiral inner raceway. The extrusion process is from shallow to deep, which not only ensures the forming accuracy but also improves the efficiency. The processing of the inner raceway of the lead screw nut can be completed only by one extrusion.

[0118] The above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. Any equivalent structure or equivalent process transformation made by using the content of the specification and drawings of the present invention, or directly or indirectly applied in other related technical fields, shall be equally included in the patent protection scope of the present invention.

Claims

1. A design method for a one-time extrusion molding tool, wherein the one-time extrusion molding tool is used to process the inner raceway of a lead screw nut, the one-time extrusion molding tool comprises a columnar working part and a plurality of extrusion head assemblies, a plurality of mounting channels are arranged on the outer wall of the working part in a preset spiral track, the mounting channels are arranged along the radial direction of the working part, at least one mounting channel is arranged on each circle of the preset spiral track, a plurality of the extrusion head assemblies are arranged in the mounting channel, the extrusion head assembly comprises a cylindrical pin and an extrusion head, the mounting position of the cylindrical pin in the mounting channel is adjustable, and the extrusion head is exposed in the mounting channel, and the degree to which the extrusion head protrudes from the mounting channel increases from the first circle to the last circle on the preset spiral track; it is characterized in that The design method comprises: S1. Collect the nut raceway parameters of the screw nut, including the contact angle α, the nominal diameter d m , nut inner diameter d0, ball diameter d b , raceway radius R, lead P z , helix angle λ and arc eccentricity e; S2. Determine the dimensions of the working part according to the nut raceway parameters; S3. Establish a normal truncated coordinate system (o'-x'y'z') with the center of the ball as the origin, establish a workpiece coordinate system (o-xyz) with the axis of the screw nut as the z-axis, and determine the transformation matrix from the normal truncated coordinate system to the workpiece coordinate system. Where θ is the moving angle of the ball center relative to the central axis of the screw nut, 0≤θ≤2π, r m is the nominal radius, p is the nut helix parameter, p = 2P z π; The profile equation of the nut spiral raceway in the normal truncated coordinate system is established. Among them, z m The "—" sign in front indicates the right arc, the "+" sign indicates the left arc, and μ is the arc angle of the raceway; Through the transformation matrix, the nut spiral raceway profile equation in the workpiece coordinate system is established, x nut =(r m -Rsinμ-ecosα)cosθ-(esinα-Rcosμ)sinθsinλ y nut =(r m -Rsinμ-ecosα)sinθ+(esinα-Rcosμ)cosθsinλ; z nut =(Rcosμ-esinα)cosλ+pθ S4. The calculation equation for the profile parameters of the nut forming tool is established as follows: the profile of the sth extrusion head on the tth circle of the primary extrusion forming tool is expressed as: 0≤θ≤2π, 0<t≤T, 0<s≤S, T is the number of circles of the preset spiral trajectory, S is the number of extrusion heads on each circle of the preset spiral trajectory, the extrusion head profile parameters are calculated, and the extrusion forming tool design is completed.

2. The design method according to claim 1, characterized in that: The one-time extrusion forming tool further comprises a clamping part and a calibration part, wherein the calibration part is cylindrical and used to calibrate the roundness of the one-time extrusion forming tool and improve the coaxiality during use, and the cross section of the clamping part is an arched rectangle with opposite sides being arc-shaped, the calibration part is connected to both ends of the length direction of the working part, and the clamping part is connected to the free end of the calibration part; The design method further comprises: Design the specific parameters of the calibration part and the clamping part to complete the design of the entire tool.

3. The design method according to claim 1, characterized in that: At least three installation channels are arranged on each circle of the preset spiral track.

4. The design method according to claim 1, characterized in that: The installation channel is a through hole.

5. The design method according to claim 4, characterized in that: The installation channel comprises a smooth section and a threaded section connected to each other, wherein the extrusion head is installed on the smooth section, and the cylindrical pin is threadedly connected to the threaded section.

6. The design method according to claim 1, characterized in that: The degree of increase of the extrusion head on each circle of the preset spiral track is selected from a linear rising trend, a step linear rising trend, an exponential rising trend or a logarithmic rising trend.

Images