Precise cold spinning machining method for variable-wall-thickness multi-rib cylinder with spherical end socket
By employing a two-pass spinning process and a precision cold spinning method, the dimensional accuracy and form and position tolerance issues of multi-ribbed cylinders with varying wall thickness were resolved, enabling high-precision spinning processing of the product and improving its quality and applicability.
Patent Information
- Application Number
- CN202511746304.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-26
- Publication Date
- 2026-01-23
AI Technical Summary
In the existing technology, during the spinning process of multi-ribbed cylinders with variable wall thickness, poor dimensional accuracy, difficulty in controlling geometric tolerances, poor material fluidity, and instability under stress lead to product quality problems.
A two-stage spinning process is employed, including blank forging, spinning mandrel design, spinning wheel parameter optimization, heat treatment, and non-destructive testing. Combined with a CNC spinning program, this ensures the stability and precision of the spinning process.
The problem of dimensional accuracy and geometric tolerance of multi-ribbed cylinders with variable wall thickness has been successfully solved. The spinning process is stable, the product has excellent performance and strong applicability.
Smart Images
Figure CN121373153A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the technical field of metal plastic forming processing, and particularly relates to a precision cold spinning processing method for a variable-wall-thickness multi-rib cylinder with a spherical head. BACKGROUND
[0002] The force spinning processing technology is an advanced precision forming processing technology, and belongs to spinning processing technology. Due to the advantages of complete metal fibers, refined grains, greatly improved mechanical properties and high manufacturing size precision of parts after force spinning processing, the force spinning processing technology is widely used in key parts of various industries.
[0003] Based on the structural characteristics of the variable-wall-thickness multi-rib cylinder, the wall thickness at the rib is different from the wall thickness of the cylinder body, which leads to different metal flow in the spinning process, increases the difficulty of size precision control in the forming process, and shape precision quality problems are prone to occur in the production and manufacturing process. Limited by the comprehensive action of multiple factors such as spinning process parameters, spinning tooling, spinning equipment processing capacity and product wall thickness difference change, the wall thickness reduction at the step and the spinning force of this type of product change sharply, and the metal deformation flow is often unstable, the step precision guarantee capacity is poor, and the quality problems such as convex outer surface, concave inner surface, large wall thickness deviation, roundness out-of-tolerance and poor axial straightness seriously affect the product quality. The precision control of the variable-wall-thickness rib is difficult. SUMMARY
[0004] The technical problem solved by the application is to provide a precision cold spinning processing method for a variable-wall-thickness multi-rib cylinder with a spherical head, which adopts two-pass spinning forming to solve the problems of poor size precision at the variable-wall-thickness rib, difficult control of form and position tolerances, poor material flow and stress instability in the prior art.
[0005] The technical scheme adopted by the application is: a precision cold spinning processing method for a variable-wall-thickness multi-rib cylinder with a spherical head, comprising the following steps: Step 1, forging of the blank: according to the product wall thickness and length requirements, the length and wall thickness of the blank are determined by the principle of constant volume and the thinning rate; Step 2, installation of the blank: the spinning mandrel is installed on the machine tool and aligned, the clamping tool is installed on the machine tool and aligned, the blank is pressed tightly on the spinning mandrel and lubricating oil is applied; Step 3, initial spinning: a horizontal three-wheel force spinning machine is used for processing, three spinning wheels are arranged at an interval of 120° along the circumference and in the axial direction, and the spinning pass thinning rate is Ψ c , the blank is spun from the initial wall thickness to a wall thickness of t c ; Step 4, first heat treatment: heating temperature 620℃, holding time 2h, then heating to 800℃, holding time 70min; Step 5, Fine spinning: Based on the product shape, compile CNC spinning programs with different wall thicknesses and their corresponding lengths, and perform spinning to transform the blank part from a wall thickness of t... c One-step spinning forming; Step 6, Non-destructive testing: Check the product for the presence of linear magnetic traces; the presence of linear magnetic traces indicates a failure. Step 7, Second heat treatment: Heating temperature 480℃, holding time 6h; Step 8, Inspection: Measure the inner diameter using an inner diameter gauge and the wall thickness using a thickness gauge to determine if it meets the product design requirements.
[0006] Preferably, the thinning rate in step 1 is taken within a range determined by a combination of the material properties, the performance of the spinning equipment, the structure of the spinning wheel, the number of spinning passes, lubrication, and the ultimate thinning rate.
[0007] Preferably, the spinning mandrel includes a connecting section, a limiting section, and a spinning working section that are installed with the spinning machine. The limiting section is located between the connecting section and the spinning working section. The spinning working section includes a straight section and a spherical end cap. The straight section is a cylinder, and the spherical end cap is a spherical body. The length of the spinning working section is 300mm + the maximum length of the product. The diameter of the spinning working section is the minimum inner diameter of the product design - 0.10mm. The radius of the spherical end cap is 0.02mm smaller than the lower tolerance of the inner surface radius of the spherical end cap of the product.
[0008] Preferably, the end face of the clamping fixture is ellipsoidal, which is adapted to the concave and convex shape of the outer end face of the spherical end cap of the product, and the center of the clamping fixture is machined with a threaded hole for connection with the machine tool.
[0009] Preferably, the angle of attack of the rotating wheel is α = 20°, and the radius of the rotating wheel is R = 4.8 mm.
[0010] The beneficial effects of this invention are: through the design of the spinning blank, the design of the spinning tooling, the setting of the spinning parameters, and the requirements of the spinning process, this invention successfully realizes the precision cold spinning of multi-ribbed cylinders with spherical heads and variable wall thickness, effectively solving the problems of dimensional accuracy and geometric tolerance errors at multiple rib positions; the spinning process is stable, the product performance is good, and the applicability is strong. Attached Figure Description
[0011] Figure 1 A schematic diagram of a multi-ribbed cylindrical product with a spherical end cap and variable wall thickness.
[0012] Figure 2 This is a schematic diagram of the blank part.
[0013] Figure 3 This is a schematic diagram of a spun mandrel structure.
[0014] Reference numerals: 1-connecting section, 2-limiting section, 3-spinning working section, t0-blank wall thickness, t1-wall thickness of the transition section of the cylindrical head, t2-wall thickness of the thin-walled section of the cylinder, t3-wall thickness at the rib of the cylinder. Detailed Implementation
[0015] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.
[0016] like Figure 1 As shown, the product processed by this invention is a multi-ribbed cylinder with a spherical end cap and variable wall thickness. One end is a spherical end cap, and the other end is an open end. Its outer circumferential surface has multiple ribs with different wall thicknesses. The wall thickness of the multi-ribbed cylinder includes the wall thickness t1 of the transition section of the cylinder end cap, the wall thickness t2 of the thin-walled section of the cylinder, and the wall thickness t3 at the ribs. This results in multiple protrusions along the length of the cylinder, i.e., the ribs, with both ends of the protrusions being thin-walled sections of the cylinder, and the wall thickness at these thin-walled sections being consistent.
[0017] Taking a high-strength steel product made of 20Ni9Co5Mo2Cr2V as an example, the high-strength spinning process of its variable wall thickness multi-ribbed cylinder mainly involves the following aspects: First, determine the thinning rate. As a crucial process parameter in the high-pressure spinning of cylindrical parts, the thinning rate directly affects the spinning pressure and the quality of the spun parts, significantly influencing the overall quality. It is closely related to material accumulation during spinning. As the thinning rate increases, the degree of material accumulation rapidly increases, leading to a decrease in the surface quality of the spun parts, and even defects such as ripples, folds, and fish-scale patterns. If the thinning rate is too high, severe material accumulation will cause local deformation under the spinning wheel to be in an unstable state, greatly increasing the spinning pressure and potentially making spinning impossible. Conversely, if the thinning rate is too low, it will increase the uneven deformation of the spun parts' thickness, reducing their precision, and may also cause insufficient deformation of the inner surface, leading to cracks. The appropriate thinning rate needs to be selected based on factors such as material properties, spinning equipment performance, spinning wheel structure, number of spinning passes, and lubrication, to ensure the product dimensions are correct.
[0018] Formula for calculating the thinning rate: Ψ t =t0-t f / t0; in: t0 — Blank wall thickness; t f —The wall thickness of the blank after one thinning process.
[0019] Limiting thinning rate: Ψ tmax=( t0-t min ) / t 0= Ψ / (0.17+Ψ); In the formula: Ψ tmax —Limited thinning rate; t0 — Blank wall thickness; t min —Minimum wall thickness of spun parts; Ψ—Reduction of area of the material.
[0020] Calculations show that the ultimate thinning rate Ψ of 20Ni9Co5Mo2Cr2V high-strength steel is... tmax =( t0-t min ) / t 0= Ψ / (0.17+Ψ)=74.63%.
[0021] Based on the product characteristics, a two-stage spinning process was designed, namely, the thinning of the spinning blank from t0 to the initial spinning t. c Then, processing is completed at t1, t2, and t3.
[0022] Based on the factors affecting the thinning rate mentioned above, a range for the thinning rate can be determined. Within this range, an appropriate thinning rate value is selected, and the blank wall thickness t0 is then calculated. Specifically, based on the known product wall thicknesses t1, t2, and t3, and combined with the thinning rate, the formula is: Ψ1 = (t... c -t1) / t c Ψ2=( t c -t2) / t c Ψ3=( t c -t3) / t c Derivation of the blank wall thickness t after initial spinning c Similarly, based on the initial turning of the blank wall thickness t... c The blank wall thickness t0 is derived by combining the thinning rate.
[0023] Due to the thin wall thickness and high dimensional accuracy requirements of the parts, the wall thickness difference of the blank before spinning is critical. Uneven wall thickness in the spinning blank will cause variations in the circumferential thinning during the spinning process, resulting in an uneven appearance, making it difficult to guarantee dimensional accuracy, and may also lead to surface peeling, wrinkles, and other issues. Therefore, the wall thickness accuracy requirement for the blank before spinning is 0.1 mm, and the inner diameter accuracy of the spinning blank is no greater than 0.15 mm. Based on the calculated thinning rate per pass, the original spinning blank wall thickness t0 is calculated to be 6.5 mm. High-intensity spinning is a non-cutting process, and the volume change during spinning is negligible. The length of the spinning blank is determined by adding a process allowance based on the principle of constant volume. Assuming the material is incompressible, the spinning blank is designed according to the principle of constant volume before and after spinning.
[0024] According to the formula: ; in: l — Product length; l0—Length of the blank; t0 — Blank wall thickness; t — Product wall thickness; d m —Product inner diameter.
[0025] The blank length l0 is obtained according to the formula. Based on the product's dimensions and structure, the designed spinning blank is as follows: Figure 2 As shown, the inner diameter of the spinning blank is determined according to the size of the product; it should be as close as possible to the size of the spinning mandrel while ensuring easy assembly, with a gap of 0.2 to 0.3.
[0026] like Figure 3 As shown, the spinning mandrel is an indispensable forming tool in the spinning production process. During spinning, the mandrel surface is subjected to considerable localized forces, with the point of application varying helically along the feed direction. Furthermore, the metal material flows along the mandrel contact surface during deformation, generating significant friction. Therefore, the spinning mandrel needs sufficient strength, rigidity, hardness, and good wear resistance; simultaneously, its surface must have low roughness, free from defects such as cracks, scratches, abrasions, and localized unevenness, and it must also possess properties such as low thermal sensitivity and a small coefficient of thermal expansion. Otherwise, the mandrel will affect the dimensional accuracy and surface quality of the product to varying degrees. In the design of the spinning mandrel, Cr12MoVA was selected as the mandrel material, with a heat treatment hardness requirement of HRC58~62. The spinning mandrel consists of a connecting section 1, a limiting section 2, and a spinning working section 3, which are installed with the spinning machine. The spinning working section 3 consists of a straight section and a ball head. The length of the spinning working section 3 meets the maximum length of the product + 300mm, the diameter of the spinning working section 3 is the minimum inner diameter of the product design - 0.10mm, and the radius of the ball head is 0.02mm smaller than the lower tolerance of the inner surface radius of the spherical head of the product.
[0027] The function of the clamping fixture is to hold the blank firmly against the spinning mandrel during spinning to prevent relative rotation. To ensure reliable clamping of the spinning blank and prevent back-extrusion during spinning, the contact surface between the clamping fixture and the product is maximized to increase the frictional torque among the spinning blank, the spinning mandrel, and the clamping fixture, preventing relative rotation and swaying of the spinning blank during spinning and avoiding cracking at the clamping surface. It is also necessary to consider that the clamping fixture should not geometrically interfere with the related devices of the spinning wheel seat during spinning. The contact point between the spinning blank and the clamping fixture is the ellipsoidal end cap. The dimensions are designed according to the ellipsoidal shape of the blank to increase its contact area. Therefore, the end face of the clamping fixture is an inwardly concave ellipsoid, which matches the concave and convex outer end face of the product's spherical end cap. A threaded hole is machined in the center of the clamping fixture for connection with the machine tool.
[0028] The spinning wheel is one of the important process equipment in the spinning process. The rationality of the design of the spinning wheel parameters directly affects the surface quality of the spun parts and the manufacturing precision of the spun parts. Spinning wheels can be classified according to their working shape into circular arc spinning wheels, straight and circular arc combination spinning wheels, double-cone spinning wheels, stepped spinning wheels, etc. Precision spinning of high-strength steel requires the use of double-cone spinning wheels for the spinning of cylinders. The design scheme of the spinning wheel will fully consider suitable contact radii, contact angles, and finishing angles. All three spinning wheels are double-cone angle spinning wheels, evenly distributed at 120° circumference along the spun blank, axially staggered, and arranged front and back along the X, Y, and Z axes. The spinning wheel angle of attack α = 20°, and the spinning wheel radius R is 4.8mm.
[0029] The process is carried out using a horizontal three-wheel high-power spinning machine. Before spinning, the spinning mandrel is clamped on the spinning machine tool and connected to the spindle flange by the threaded connecting plate. The spinning mandrel is aligned to ensure that the runout is no more than 0.03. The prepared CNC spinning program is input into the computer, and then a no-load test run is performed to ensure the safety of the machine tool operation and the feasibility of the program.
[0030] The specific steps are as follows: Step 1, Forging of the blank: Based on the product wall thickness and length requirements, the length and wall thickness of the blank are determined by the principle of constant volume and the thinning rate; Step 2, Install the blank: Install the spinning mandrel on the machine tool and align it. Install the clamping fixture on the machine tool and align it. Press the blank onto the spinning mandrel and apply lubricating oil. Use the clamping fixture to clamp it onto the spinning mandrel. Drive the spinning mandrel and the blank to rotate together through the spinning machine spindle. Coolant needs to be sprayed during the spinning process. Step 3, Initial Spinning: A horizontal three-wheel high-power spinning machine is used for processing. Three spinning wheels, arranged at equal intervals along the axial direction and with an included angle of 120°, spin the material. The thinning rate per spinning pass is Ψ. c The spinning wheel feeds sequentially along the set CNC program, continuously thinning the blank from its initial wall thickness to a wall thickness of t. cThe product is demolded using a stripper fork; Step 4, First heat treatment: Heating temperature 620℃, holding time 2h, then heating to 800℃, holding time 70min, to improve the plasticity of the spinning blank material and perform quenching and tempering treatment; Step 5, Fine Spinning: Based on the product's shape, a CNC spinning program is created for different wall thicknesses and their corresponding lengths. The spinning wheel feeds sequentially along the set CNC program, continuously thinning the blank from a wall thickness of t. c The product is demolded using a stripper fork after a single spin forming process. Step 6, Non-destructive testing: Check the product for the presence of linear magnetic traces; the presence of linear magnetic traces indicates a failure. Step 7, Second heat treatment: Heating temperature 480℃, holding time 6h; Step 8, Inspection: Measure the inner diameter using an inner diameter gauge and the wall thickness using a thickness gauge to determine if it meets the product design requirements.
[0031] The main parameters of spinning processing include: thinning rate per pass, spindle speed, spinning wheel feed ratio, and spinning gap.
[0032] The spindle speed of a machine tool is a parameter directly related to the spinning equipment and productivity, and can be selected within a wide range to improve production efficiency. Increasing the spinning speed can effectively improve the surface roughness of the spun parts and increase productivity. However, the increase in spindle speed is limited by the power, rigidity, and cooling conditions of the spinning equipment. When the spun parts operate at high speeds, equipment with insufficient rigidity will produce severe vibrations. Furthermore, the intense friction between the spinning wheel and the spun parts caused by high-speed rotation, if not adequately cooled, will prevent the generated heat from dissipating in time, inevitably leading to a significant decrease in the surface quality of the spun parts. Based on the characteristics of the part material and the thin-walled nature of the spinning cylinder, a speed of 160-200 r / min is selected.
[0033] The feed ratio of the spinning wheel has a significant impact on the spinning process and is a crucial factor affecting the dimensional accuracy of the product. It significantly influences the diameter accuracy and overall quality of the spun part. During spinning, a large feed ratio promotes necking, while a small feed ratio has the opposite effect. Both the inner diameter deviation and wall thickness deviation of the spun product increase with increasing feed ratio. However, appropriately increasing the feed ratio can improve the film adhesion of the spun part, thereby reducing the degree of diameter expansion. Based on finite element simulation results, the feed ratio of the spinning wheel is set to 0.8-1.6 mm / r.
[0034] The thinning rate per pass is selected as follows: The initial spin pass thinning rate is Ψ c = (t0-t c) / t0 = (6.5 - 3.1) / 6.5 = 52.31%; The thinning rate of the fine spinning section is divided into three parts: 1) Thinning rate of the transition section of the cylindrical head: Ψ1 = (t c -t1) / t c = (3.1-2.4) / 3.1=22.58%; 2) Thinning rate per pass in the thin-walled section of the cylinder: Ψ2 = (t c -t2) / t c = (3.1-1.2) / 3.1=61.29%; 3) Thinning rate at the cylindrical reinforcement: Ψ3 = (t) c -t3) / t c = (3.1-2) / 3.1=35.49%.
[0035] The gap between the spinning wheel and the mandrel is one of the important process parameters in the high-strength spinning process. During spinning, the wall thickness of the spun part is determined by adjusting the gap between the spinning wheel and the spinning mandrel. The spinning gap directly affects the dimensional accuracy of the part, especially the dimensional accuracy at ribs with different wall thicknesses. Because the spun part itself will have a certain springback after deformation, the wall thickness of the spun part will increase. Therefore, the wall thickness of the blank after spinning is t=t 理论 +△h, where △h is the springback amount of spinning, which is related to the material and wall thickness. With the material remaining constant, when the blank wall thickness t ≤ 0.9 mm, the springback amount △h is 0.10–0.30 mm; when the blank wall thickness t > 0.9–10 mm, the springback amount △t is 0.30–0.60 mm; when the blank wall thickness t > 10–20 mm, the springback amount △t is 0.60–0.70 mm; and when the blank wall thickness t > 20 mm, the springback amount △t is 0.70–0.90 mm.
[0036] Through the design of the spinning blank, the design of the spinning tooling, the setting of the spinning parameters, and the requirements of the spinning process, the precision cold spinning of the variable wall thickness multi-ribbed cylinder with spherical head was successfully achieved, and the product qualification rate was significantly improved.
[0037] The above describes specific embodiments of the present invention and the technical principles employed. Any modifications or equivalent transformations based on the technical solutions of the present invention should be included within the protection scope of the present invention.
Claims
1. A method for precision cold spinning of a multi-ribbed cylinder with a spherical end cap and variable wall thickness, characterized in that, Includes the following steps: Step 1, Forging of the blank: Based on the product wall thickness and length requirements, the length and wall thickness of the blank are determined by the principle of constant volume and the thinning rate; Step 2, Install the blank: Install the spinning mandrel on the machine tool and align it, install the clamping fixture on the machine tool and align it, press the blank onto the spinning mandrel and apply lubricating oil; Step 3, Initial Spinning: A horizontal three-wheel high-power spinning machine is used for processing. Three spinning wheels, arranged at equal intervals along the axial direction and with an included angle of 120°, spin the material. The thinning rate per spinning pass is Ψ. c The blank is spun from its initial wall thickness to a wall thickness of t. c ; Step 4, First heat treatment: Heating temperature 620℃, holding time 2h, then raising the temperature to 800℃, holding time 70min; Step 5, Fine spinning: Based on the product shape, compile CNC spinning programs with different wall thicknesses and their corresponding lengths, and perform spinning to transform the blank part from a wall thickness of t... c One-step spinning forming; Step 6, Non-destructive testing: Check the product for the presence of linear magnetic traces; the presence of linear magnetic traces indicates a failure. Step 7, Second heat treatment: Heating temperature 480℃, holding time 6h; Step 8, Inspection: Measure the inner diameter using an inner diameter gauge and the wall thickness using a thickness gauge to determine if it meets the product design requirements.
2. The method for precision cold spinning of a multi-ribbed cylinder with a spherical end cap and variable wall thickness according to claim 1, characterized in that: The thinning rate mentioned in step 1 is taken within a range based on the material properties, the performance of the spinning equipment, the structure of the spinning wheel, the number of spinning passes, lubrication, and the ultimate thinning rate.
3. The method for precision cold spinning of a multi-ribbed cylinder with a spherical end cap and variable wall thickness according to claim 1, characterized in that: The spinning mandrel includes a connecting section, a limiting section, and a spinning working section that are installed with the spinning machine. The limiting section is located between the connecting section and the spinning working section. The spinning working section includes a straight section and a spherical end cap. The straight section is a cylinder, and the spherical end cap is a spherical body. The length of the spinning working section is 300mm + the maximum length of the product. The diameter of the spinning working section is the minimum inner diameter of the product design - 0.10mm. The radius of the spherical end cap is 0.02mm smaller than the lower tolerance of the inner surface radius of the spherical end cap of the product.
4. The method for precision cold spinning of a multi-ribbed cylinder with a spherical end cap and variable wall thickness according to claim 1, characterized in that: The end face of the clamping fixture is ellipsoidal, which is adapted to the concave and convex shape of the outer end face of the spherical end cap of the product. The center of the clamping fixture is machined with a threaded hole for connection with the machine tool.
5. The method for precision cold spinning of a multi-ribbed cylinder with a spherical end cap and variable wall thickness according to claim 1, characterized in that: The angle of attack of the rotating wheel is α = 20°, and the radius of the rotating wheel is 4.8 mm.