Design method of spinning core and sleeve for thin-walled cylindrical part with inward annular rib

Abstract

A design method of a thin-walled cylindrical spinning core mold and a sleeve with a circumferential inner rib, comprising a fixed core mold, a movable core mold and a sleeve. The fixed core mold is connected to the spinning machine at one end of the connecting section; the flange of the movable core mold fixes the spinning blank and the movable core mold together through the sleeve. Three sleeves are evenly distributed on the circumference of the flange of the movable core mold, and the spinning blank fixed section in contact with the end face of the flange and the flange are fixed. The processing efficiency of the single-piece workpiece is shortened by 88.2%, the material utilization rate is increased by 3.2 times, the raw material cost is reduced, the workpiece processing efficiency is improved, the workpiece precision guarantee capability is improved, and mass production is easy to realize. The structure of the forward spinning blank is optimized from the traditional inner flange to the outer flange, and the axial movement of the blank during forming is limited through the sleeve. When demolding, the workpiece with an inner rib is removed from the spinning core mold by disassembling the sleeve, which reduces the difficulty of demolding and shortens the demolding time, and has good engineering application value.

Description

Technical Field

[0001] This invention relates to the field of spinning forming, specifically a design method for a spinning mandrel with annular inward ribs on a thin-walled cylindrical part, and a demolding method using the mandrel. Background Technology

[0002] Thin-walled rotating parts are a type of structural component widely used in the aerospace field, such as solid rocket motor casings, missile guidance bays, and warhead compartments. In recent years, due to specific aerodynamic loads and flight sling requirements, thin-walled steel engine casings with circumferential internal ribs have become increasingly common. This type of structure improves the strength and stiffness of the workpiece without affecting its external aerodynamic performance, thereby optimizing the structural weight of the engine casing and enhancing overall performance. Spin forming of thin-walled cylindrical parts with internal ribs offers advantages such as high material utilization, high forming accuracy, high efficiency, and low cost. However, the spin forming of such thin-walled cylindrical parts with internal ribs presents significant challenges in the structural design of the spin forming mandrel, mandrel installation, and workpiece demolding.

[0003] Currently, to ensure the forming quality of the internal ribs, spinning is performed using a forward spinning method, where the direction of the spinning wheel feed is consistent with the direction of metal flow. Typically, to prevent the blank from sliding axially during spinning, an inner flange with an inner diameter smaller than the spinning mandrel diameter is designed at the starting point of the forward spinning blank. This prevents the forward spinning blank from sliding axially during forming due to the restriction of the inner flange, thus ensuring forming accuracy and quality. However, this spinning method requires that after spinning, the thin-walled cylindrical part with internal ribs and a portion of the spinning mandrel must be removed. The inner flange on the cylindrical part must then be machined off before the thin-walled cylindrical part with internal ribs can be removed from the removed portion of the spinning mandrel. This significantly increases the difficulty and time of demolding, reduces production efficiency, and increases manufacturing costs.

[0004] To address the challenges in designing the spinning mandrel and the difficulty in demolding during the spinning process with internal ribs, Northwestern Polytechnical University disclosed a mandrel for spinning parts with transverse internal ribs in its utility model patent 201120390009.X. The workpiece targeted by this spinning mandrel is a thin-walled component with a curved generatrix and transverse internal ribs, similar to a headgear. This component differs significantly in structure from the thin-walled cylindrical component described in this invention, and the spinning methods used by the two are also fundamentally different.

[0005] Northwestern Polytechnical University disclosed a mandrel and demolding method for spinning with transverse inner ribs in invention application No. 2011103109892; a mandrel and forward demolding method for spinning with transverse inner ribs in invention application No. 2011101549351; and a mandrel and backward demolding method for spinning with transverse inner ribs in invention application No. 2011101549807. The aforementioned inventions all address the demolding of spun parts with transverse internal ribs by using multiple short clamping blocks to form a detachable clamping plate at the core mold corresponding to the transverse internal rib segment. After disassembly, the spun part with transverse internal ribs can be removed from the spun core mold. However, the workpieces addressed by these inventions are all thin-walled components with curved generatrices, which differ structurally from the thin-walled cylindrical parts addressed by this invention. Furthermore, thin-walled cylindrical parts are typically processed using a high-pressure spun forming method. During the forming process, the spun core mold needs to withstand a large radial load. The clamping plate, composed of multiple parts, requires high assembly precision and is difficult to assemble; moreover, it poses a risk of damage when bearing large radial loads. Therefore, this design method is unsuitable for spun forming of thin-walled cylindrical parts with circumferential internal ribs. The spun core mold designed in this invention has a core mold portion corresponding to the circumferential internal rib segment that is integral with the other parts of the core mold, thus possessing sufficient strength and rigidity to meet the requirements of spun forming of thin-walled cylindrical parts.

[0006] Invention application number 2018101730531 discloses a multifunctional complex longitudinal and transverse internal ribbed cylindrical component spinning forming mandrel device and method; invention application number 201811188626.4 discloses a mandrel for spinning components with spiral internal ribs and demolding; invention application number 201910139586.2 discloses a spinning forming die for components with longitudinal and transverse internal ribs and a dimensional design method. All of the above inventions are spinning mandrels for spinning cylindrical components with longitudinal and transverse internal ribs. To achieve demolding, the spinning mandrels are all designed as segmented molds. However, the overall design of the spinning mandrel is quite complex, with many components, each exceeding 10 parts. Moreover, the demolding process relies on disassembling the segmented mold piece by piece, which brings great difficulty to the installation and disassembly of the entire mandrel, resulting in low efficiency. Furthermore, the excessive number of components also poses significant challenges in controlling installation accuracy, thus limiting its engineering application value. Therefore, the design concept of the above invention has no guiding significance for the efficient spinning forming of thin-walled cylindrical parts with an inner circumferential rib, which is the target of this invention. Moreover, the design concept of this invention is based on rapid demolding under forward spinning conditions, and its engineering application value is obvious.

[0007] The invention with application number 201710604379.0 discloses a mandrel and forming method for spinning transverse inner rib members of different widths. The feature of this invention is that the spinning of transverse inner rib members of different widths can be achieved by adjusting the position of the movable sleeve on a set of mandrels. However, the invention does not describe how the workpiece is demolded.

[0008] In summary, existing research on the design and demolding methods of mandrels for spinning thin-walled parts with internal ribs focuses on two aspects. One aspect is the spinning of curved busbar parts, where the spinning method and mandrel design differ significantly from the spinning method and mandrel design of the thin-walled cylindrical parts described in this invention. The other aspect is the spinning of thin-walled cylindrical parts with longitudinal and transverse internal ribs. The spinning mandrel structure designed in this invention is very complex, with many components, resulting in cumbersome mandrel installation and disassembly during the forming process, low production efficiency, and difficulty in controlling the installation accuracy of such mandrels, thus limiting their engineering application value. Summary of the Invention

[0009] To overcome the shortcomings of existing technologies, such as overly complex core mold structures, cumbersome demolding processes, and long processing times, this invention proposes a design method for a spin molding core mold and ferrule for thin-walled cylindrical parts with circumferential inner ribs.

[0010] The spinning mandrel with circumferential inner ribs proposed in this invention includes a fixed mandrel, a movable mandrel, and ferrules. The fixed mandrel is functionally divided into a fixed mandrel connecting section and a fixed mandrel forming section; one end of the fixed mandrel connecting section is connected to the spinning machine; the movable mandrel flange uses ferrules to fix the spinning blank to the movable mandrel. There are three ferrules, evenly distributed on the circumference of the flange of the movable mandrel, which fix the spinning blank section that is in contact with the flange end face to the flange.

[0011] The movable core mold is functionally divided into a movable core mold connecting section, a movable core mold flange, and a movable core mold forming section. The end face of the movable core mold forming section has an axially protruding conical locking block. This conical locking block is embedded in a conical groove at the center of the end face of the thin-walled cylindrical inner rib forming section on the fixed core mold, ensuring that the end face of the movable core mold forming section is in close contact with the end face of the thin-walled cylindrical inner rib forming section of the fixed core mold.

[0012] The circumferential surface of the movable mandrel forming section is stepped. The section closest to the movable mandrel flange is the movable mandrel thin-walled cylindrical forming section, and its diameter is the same as that of the fixed mandrel thin-walled cylindrical forming section. The section furthest from the movable mandrel flange is the movable mandrel thin-walled cylindrical inner rib forming section, and its diameter is the same as that of the fixed mandrel thin-walled cylindrical inner rib forming section. The length of the movable mandrel thin-walled cylindrical inner rib forming section is equal to the workpiece inner rib width × 0.5. The diameter of the movable mandrel flange is the same as the outer diameter of the spinning blank fixed section, and the axial length L1 of the movable mandrel flange is 15–20 mm.

[0013] The end face between the movable mandrel flange and the movable mandrel connecting section has an axially protruding annular boss. The diameter of the annular boss is 20mm smaller than the diameter of the thin-walled cylindrical forming section of the movable mandrel. Screw holes for connecting the tail rod are evenly distributed on the end face of the annular boss.

[0014] The end face of the movable mandrel flange near the movable mandrel connection section is machined with an annular positioning groove with a depth of 2mm and a width of Lp. The width Lp of the annular positioning groove is 0.5mm larger than the diameter of the positioning screw. When the positioning screw contacts the movable mandrel, the center of the diameter of the positioning screw is located on the pitch circle of the annular positioning groove.

[0015] The large-diameter section of the fixed mandrel is the fixed mandrel connecting section, and the small-diameter section is the fixed mandrel forming section. The fixed mandrel connecting section is connected to the adapter plate of the spinning machine.

[0016] The fixed mandrel forming section is divided into a thin-walled cylindrical forming section and a thin-walled cylindrical inner rib forming section. The thin-walled cylindrical forming section is used for forming thin-walled cylinders, and its outer diameter is 0.2–0.3 mm smaller than the inner diameter of the workpiece. The end of the fixed mandrel forming section is the thin-walled cylindrical inner rib forming section; the outer diameter of the thin-walled cylindrical inner rib forming section = outer diameter of the thin-walled cylindrical forming section - height of the workpiece inner rib × 2; the length of the thin-walled cylindrical inner rib forming section = width of the workpiece inner rib × 0.5.

[0017] There is a groove at the center of the end face of the fixed core mold connecting section for assembly with the spinning machine adapter plate; there is a conical groove at the center of the end face of the thin-walled cylindrical inner rib forming section for assembly with the movable core mold.

[0018] The ferrule is a quarter-circle arc plate, with its inner diameter R equal to the outer diameter of the movable mandrel flange multiplied by 0.5. The inner surface of the arc plate has a circumferential groove for fixing the fixed section of the spinning blank and the movable mandrel flange. The groove width L is (L1 + L2) + 0.3–0.5 mm; where L1 is the axial length of the movable mandrel flange and L2 is the axial length of the fixed section of the spinning blank. The groove depth h is 10–12 mm; the thickness L0 of the groove walls on both sides is determined according to the diameter of the workpiece, and is 10–15 mm. When the workpiece diameter is ≤300 mm, the smaller value of L0 is used; when the workpiece diameter is >300 mm, the larger value of L0 is used. The thickness of the bottom of the ferrule groove is H, where H = 5–8 mm.

[0019] The design method for the ferrule in the spinning mandrel of the thin-walled cylindrical part with annular inward ribs proposed in this invention specifically involves the design of the thickness H at the bottom of the ferrule groove. The specific process is as follows:

[0020] Step 1, determine the strength requirements for the card sleeve:

[0021] Let P be the axial spinning force of a single spinning wheel during the forward high-force spinning of a cylindrical component. Z The yield strength of the material used for the ferrule is σ, and the ferrule must satisfy the following:

[0022] (1)

[0023] In formula (1): S is the cross-sectional area of ​​the bottom thickness of the groove, and K is the safety factor. Considering the deviation between the theoretical calculation of the rotation force and the actual existence, the safety factor K = 1.2.

[0024] The inner diameter of the arc plate of the ferrule is R.

[0025] Step 2, determine the cross-sectional area S of the bottom thickness of the groove:

[0026] The cross-sectional area S of the bottom thickness of the groove is determined by formula (2).

[0027] (2)

[0028] In the formula, L is the arc length at H / 2. .

[0029] Substituting L into Formula 2, the cross-sectional area S is:

[0030] (3)

[0031] Step 3, determine the thickness H of the bottom of the groove:

[0032] Substituting formula (3) into formula (1), we obtain the thickness H at the bottom of the groove; this H must satisfy formula (4):

[0033] (4)

[0034] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0035] Compared to traditional thick-walled tube turning, the spinning method used in this invention can significantly reduce raw material costs, improve workpiece processing efficiency, and enhance workpiece precision assurance capabilities, facilitating mass production. Traditional thick-walled tube turning requires a tube length at least greater than the total length of the workpiece to be machined. Furthermore, the material removal from the thick-walled tube to the final workpiece is substantial, resulting in significant accumulated processing stress. To reduce workpiece deformation caused by processing stress, the turning process typically requires one or more manual stress-relieving aging treatments, leading to long processing cycles and high costs. Additionally, during the turning process, the wall thickness continuously decreases, weakening the tube blank's rigidity and increasing deformation, thus making precision control difficult and resulting in a low yield rate. For example, a workpiece has an outer diameter of 210mm, a length of 850mm, a cylindrical section wall thickness of 1.5mm, and includes a circumferential rib with an inner rib height of 2mm and a width of 120mm. Initially, a thick-walled tube with a diameter of 180mm, a thickness of 12mm, and a length of 900mm was machined by turning, taking 72 hours. Due to the high precision required for the workpiece wall thickness, the overall pass rate was less than 70%. A spinning method was then adopted, using an 8mm thick spinning blank, which was machined in three consecutive passes to a thickness of 1.5mm. Including the spinning blank... The processing time for one workpiece is approximately 8.5 hours. Furthermore, based on the principle of constant volume, the length of the spun blank used to process one workpiece is 280mm. Therefore, using turning methods, 3.2 spun blanks can be processed from the thick-walled tube used to process one workpiece. Thus, compared to traditional turning methods for thick-walled tubes, spun forming reduces the processing efficiency per workpiece by 88.2%, increases material utilization by 3.2 times, and reduces raw material costs to 32.15% of the original, demonstrating significant economic benefits.

[0036] Furthermore, compared to existing spinning methods, the demolding efficiency of this invention is effectively improved. Compared to reverse spinning, forward spinning is beneficial for increasing the filling rate of internal ribs and reducing internal rib forming defects. However, in order to limit the axial movement of the blank during the forming process, the part in contact with the end of the spinning mandrel is often designed as an inner flange structure in the blank design. After the workpiece with internal ribs is spun, since the diameter of the internal rib part and the diameter of the inner flange part are both smaller than the diameter of the spinning mandrel, the workpiece with internal ribs needs to be unloaded together with a part of the spinning mandrel during unloading. Then, the inner flange on the workpiece is machined off by turning before the workpiece with internal ribs can be removed from the part of the spinning mandrel that was unloaded together. This not only increases the difficulty of demolding, but also increases the demolding time. The spinning mandrel designed in this invention optimizes the structure of the forward spinning blank from a traditional inner flange to an outer flange. Simultaneously, it restricts axial movement of the blank during the forming process using a ferrule. Thus, during demolding, the workpiece with internal ribs can be removed from the spinning mandrel simply by disassembling the ferrule, significantly reducing demolding difficulty and time. Taking a 210mm diameter workpiece with internal ribs as an example, using the traditional forward spinning method, the demolding time for one workpiece is 2 hours. Using the spinning mandrel and demolding method of this invention, the demolding time for one workpiece is 15 minutes, a reduction of 87.5%, demonstrating significant value in engineering applications. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the structure of the present invention.

[0038] Figure 2 yes Figure 1 View from direction A.

[0039] Figure 3 This is a schematic diagram of the fixed core mold structure.

[0040] Figure 4 This is a schematic diagram of the movable core mold.

[0041] Figure 5 This is a schematic diagram of the card sleeve structure; in which, Figure 5 'a' is the main view. Figure 5 b is Figure 5 Sectional view of CC in a.

[0042] Figure 6 It is a part drawing of a spun blank.

[0043] In the diagram: 1. Fixed mandrel; 2. Movable mandrel; 3. Sleeve; 4. Positioning screw; 5. Spinning blank; 6. Fixed mandrel connecting section; 7. Fixed mandrel forming section; 8. Movable mandrel connecting section; 9. Movable mandrel flange; 10. Movable mandrel forming section; 11. Spinning blank deformation section; 12. Spinning blank transition section; 13. Spinning blank fixing section; 14. Pitch circle position of the annular positioning groove. Detailed Implementation

[0044] This embodiment is a spinning mandrel for a thin-walled cylindrical part with annular inward ribs. The thin-walled cylindrical part with annular inward ribs has an inner diameter of Φ207±0.15mm, a length of 850mm, a wall thickness of 1.5mm, an inner rib height of 1mm, and an inner rib width of 120mm.

[0045] The spinning mandrel includes a fixed mandrel 1, a movable mandrel 2, and a retaining sleeve 3. The fixed mandrel 1 is functionally divided into a fixed mandrel connecting section 6 and a fixed mandrel forming section 7; one end of the fixed mandrel connecting section 6 is connected to the spinning machine, and one end of the fixed mandrel forming section 7 is connected to the movable mandrel. There are three retaining sleeves 3, evenly distributed on the circumference of the flange of the movable mandrel, which secure the spinning blank fixing section 13, which is in contact with the flange end face, to the flange.

[0046] In use, one end of the spinning blank 5 is fitted onto the fixed core mold, and one end of the positioning section of the movable core mold is inserted into the spinning blank, so that the tapered locking block on the end face of the movable core mold is inserted into the tapered groove on the end face of the fixed core mold. Three retaining sleeves 3 are respectively fitted onto the outer circumferential surface of the connection between the movable core mold and the fixed section of the spinning blank, and each retaining sleeve 3 is connected to the movable core mold it contacts by positioning screws 4, thereby fixing the spinning blank 5 and the movable core mold 2 together.

[0047] The movable core mold 2 is a rotating body with a stepped circumferential surface. Functionally, it comprises a movable core mold connecting section 8, a movable core mold flange 9, and a movable core mold forming section 10. The end face of the movable core mold forming section has an axially protruding conical locking block. This conical locking block is embedded in a conical groove at the center of the end face of the thin-walled cylindrical inner rib forming section on the fixed core mold 1, ensuring that the end face of the movable core mold forming section is in contact with the end face of the thin-walled cylindrical inner rib forming section of the fixed core mold.

[0048] The circumferential surface of the movable core mold forming section 10 is a stepped surface. The section closest to the movable core mold flange is the movable core mold thin-walled cylindrical forming section, and the diameter of the movable core mold thin-walled cylindrical forming section is the same as the diameter of the fixed core mold thin-walled cylindrical forming section. The section furthest from the movable core mold flange is the movable core mold thin-walled cylindrical inner rib forming section, and the diameter of the movable core mold thin-walled cylindrical inner rib forming section is the same as the diameter of the fixed core mold thin-walled cylindrical inner rib forming section. The length of the movable core mold thin-walled cylindrical inner rib forming section is equal to the width of the workpiece inner rib × 0.5.

[0049] In the movable core mold 2, the movable core mold connecting section 8 is used to connect the tail ejector rod on the tail ejector seat of the spinning machine; the spinning blank 5 is fitted onto the fixed core mold forming section, and the tail ejector rod is moved axially towards the fixed core mold forming section to ensure that the movable core mold forming section and the fixed core mold forming section are assembled together. The spinning blank is moved towards the movable core mold flange 9 until the end face of the fixed section of the spinning blank is in contact with the end face of the movable core mold flange 9. The movable core mold flange 9 fixes the spinning blank 5 and the movable core mold 2 together through the ferrule 3. The diameter of the movable core mold flange 9 is consistent with the outer diameter of the fixed section 13 of the spinning blank, and the axial length L1 of the movable core mold flange 9 is 15-20mm.

[0050] The end face between the movable core mold flange 9 and the movable core mold connecting section 8 has an axially protruding annular boss. The diameter of the annular boss is generally 20mm smaller than the diameter of the thin-walled cylindrical forming section of the movable core mold. Two screw holes are evenly distributed on the end face of the annular boss. When the movable core mold connecting section 8 is fitted onto the tail ejector rod, the two screw holes on the end face of the annular boss are used to fix the movable core mold 2 and the tail ejector rod together.

[0051] A ring-shaped positioning groove with a depth of 2mm and a width of Lp is machined on the end face of the movable core mold flange 9 near the movable core mold connecting section 8. The width Lp of the ring-shaped positioning groove is 0.5mm larger than the diameter of the positioning screw 4. When the positioning screw 4 contacts the movable core mold 2, the center of the diameter of the positioning screw 4 is located on the pitch circle of the ring-shaped positioning groove.

[0052] In this embodiment, the outer diameter of the movable mandrel flange 9 is consistent with the outer diameter of the fixed section 13 of the spinning blank. Once the structural dimensions of the spinning blank are determined, the outer diameter of the movable mandrel flange 9 can be determined. The length L1 of the movable mandrel flange 9 is 15mm. The outer diameter of the fixed mandrel thin-walled cylindrical forming section is Φ206.70±0.05mm. Since the outer diameter of the movable mandrel thin-walled cylindrical forming section is consistent with the outer diameter of the fixed mandrel thin-walled cylindrical forming section, the outer diameter of the movable mandrel thin-walled cylindrical forming section is Φ206.70±0.05mm. The outer diameter of the fixed mandrel thin-walled cylindrical inner rib forming section is Φ204.70±0.05mm. Since the outer diameter of the movable mandrel forming section inner rib forming section is consistent with the outer diameter of the fixed mandrel forming section inner rib forming section, the outer diameter of the movable mandrel thin-walled cylindrical inner rib forming section is Φ204.70±0.05mm. The width of the inner rib of the workpiece is 120mm. The length of the inner rib forming section of the thin-walled cylindrical movable mandrel is 120mm × 0.5 = 60mm, that is, the length of the inner rib forming section of the thin-walled cylindrical movable mandrel is 60mm.

[0053] The large-diameter section of the fixed mandrel 1 is the fixed mandrel connecting section 6, and the small-diameter section is the fixed mandrel forming section 7. The fixed mandrel connecting section 6 is connected to the adapter plate of the spinning machine.

[0054] The fixed mandrel forming section 7 is divided into a thin-walled cylinder forming section and a thin-walled cylinder inner rib forming section. The thin-walled cylinder forming section is used for forming the thin-walled cylinder, and its outer diameter is 0.2–0.3 mm smaller than the inner diameter of the workpiece. At the end of the fixed mandrel forming section, there is an annular concave surface on the circumferential surface for forming the inner rib of the thin-walled cylinder. This annular concave surface is the thin-walled cylinder inner rib forming section. The outer diameter of the thin-walled cylinder inner rib forming section = outer diameter of the thin-walled cylinder forming section - height of the inner rib of the workpiece × 2; the length of the thin-walled cylinder inner rib forming section = width of the inner rib of the workpiece × 0.5.

[0055] There is a groove at the center of the end face of the fixed core mold connecting section 6 for assembly with the spinning machine adapter plate; there is a conical groove at the center of the end face of the thin-walled cylindrical inner rib forming section for assembly with the movable core mold 2.

[0056] In this embodiment, the inner diameter of the thin-walled cylindrical part with annular inner ribs is 207±0.15mm. To facilitate smooth demolding of the workpiece after spinning, the outer diameter of the thin-walled cylindrical forming section 7 of the fixed core mold is 0.3mm smaller than the inner diameter of the workpiece. Therefore, the outer diameter of the thin-walled cylindrical forming section of the fixed core mold is Φ206.70±0.05mm. The height of the inner rib of the workpiece is 1mm. The outer diameter of the thin-walled cylindrical forming section of the fixed core mold is equal to the outer diameter of the thin-walled cylindrical forming section of the fixed core mold Φ206.70±0.05mm minus twice the height of the inner rib of the workpiece (1mm), i.e., the outer diameter of the thin-walled cylindrical forming section of the fixed core mold is Φ204.70±0.05mm. The width of the inner rib of the workpiece is 120mm. The length of the thin-walled cylindrical forming section of the fixed core mold is the width of the inner rib of the workpiece (120mm) × 0.5 = 60mm, i.e., the length of the thin-walled cylindrical forming section of the fixed core mold is 60mm.

[0057] The ferrule 3 is a quarter-circle arc plate, with its inner diameter R equal to the outer diameter of the movable mandrel flange 9 multiplied by 0.5. The inner surface of the arc plate has a circumferential groove for fixing the fixed section of the spinning blank and the movable mandrel flange. The groove width L is (L1 + L2) + 0.3–0.5 mm; where L1 is the axial length of the movable mandrel flange and L2 is the axial length of the fixed section of the spinning blank. The groove depth h is 10–12 mm; the thickness L0 of the groove walls on both sides is determined according to the diameter of the workpiece, and is 10–15 mm. When the workpiece diameter is ≤300 mm, the smaller value of L0 is used; when the workpiece diameter is >300 mm, the larger value of L0 is used. The thickness of the bottom of the ferrule groove is H, where H = 5–8 mm.

[0058] On the side of the slot near the movable mandrel flange, there are four threaded holes for installing positioning screws 4. The diameter and thread profile of the threaded holes are consistent with the diameter and thread profile of the positioning screws 4. The threaded holes are evenly distributed on the arc corresponding to the central angle of 90°, that is, the included angle between the centers of two adjacent threaded holes is 18°.

[0059] This embodiment also proposes a design method for determining the thickness H of the bottom of the sleeve groove, the specific process of which is as follows:

[0060] Step 1, determine the strength requirements for the card sleeve:

[0061] Let P be the axial spinning force of a single spinning wheel during the forward high-force spinning of a cylindrical component. Z The yield strength of the material used for ferrule 3 is σ. To ensure that ferrule 3 does not undergo plastic deformation during use, the ferrule must meet the following requirements:

[0062] (1)

[0063] In formula (1): S is the cross-sectional area of ​​the bottom thickness of the groove, and K is the safety factor. Considering the deviation between the theoretical calculation of the rotation force and the actual existence, the safety factor K = 1.2.

[0064] Step 2, determine the cross-sectional area S of the bottom thickness of the groove:

[0065] The cross-sectional area S of the bottom thickness of the groove is determined by formula (2).

[0066] (2)

[0067] In the formula, L is the arc length at H / 2. .

[0068] Substituting L into Formula 2, the cross-sectional area S is:

[0069] (3)

[0070] R is the inner diameter of the card sleeve.

[0071] Step 3, determine the thickness H of the bottom of the groove:

[0072] Substituting formula (3) into formula (1), we obtain the thickness H at the bottom of the groove; this H must satisfy formula (4):

[0073] (4)

[0074] In this embodiment, the ferrule 3 is made of 30CrMnSiA high-strength steel with a yield strength σ = 835MPa. The material used for spinning is D406A ultra-high-strength steel with a tensile strength of 650MPa in the formed state. The thinning rate Ψ = 75%, the thickness of the deformation section 11 of the spinning blank is 6mm, the feed speed is f = 1mm / r, the diameter of the spinning wheel is D = 380mm, and the contact angle of the spinning wheel is α = 25°. The axial spinning force P is calculated when the cylindrical part is spun under positive force. Z =17992N. According to the present invention, the thickness H at the bottom of the groove in the sleeve 3 must satisfy formula (3): It can be seen that the thickness H at the bottom of the groove in the sleeve 3 needs to meet the following requirements:

[0075] Considering the rigidity of the sleeve 3 during use, in this embodiment, the thickness H of the bottom of the groove in the sleeve 3 is 5mm.

Claims

1. A spinning mandrel for a thin-walled cylindrical part with annular inward ribs, characterized in that, Fixed core mold (1), movable core mold (2), and ferrule (3); the fixed core mold is divided into a fixed core mold connecting section (6) and a fixed core mold forming section (7) according to its function; one end of the fixed core mold connecting section is connected to the spinning machine; the movable core mold flange (9) fixes the spinning blank and the movable core mold (2) together through the ferrule; there are three ferrules, which are evenly distributed on the circumference of the flange of the movable core mold, and fix the spinning blank fixing section (13) that is in contact with the end face of the flange to the flange; The movable core mold (2) is divided into a movable core mold connecting section (8), a movable core mold flange (9), and a movable core mold forming section (10) according to their functions. The end face of the movable core mold forming section has an axially protruding conical block. The conical block is embedded in the conical groove at the center of the end face of the thin-walled cylindrical inner rib forming section on the fixed core mold (1), and the end face of the movable core mold forming section is in contact with the end face of the thin-walled cylindrical inner rib forming section of the fixed core mold. The fixed core mold forming section (7) is divided into a thin-walled cylindrical forming section and a thin-walled cylindrical inner rib forming section; wherein, the thin-walled cylindrical forming section is used for forming thin-walled cylinders, and its outer diameter is 0.2 to 0.3 mm smaller than the inner diameter of the workpiece; the end of the fixed core mold forming section is the thin-walled cylindrical inner rib forming section; the outer diameter of the thin-walled cylindrical inner rib forming section = the outer diameter of the thin-walled cylindrical forming section - the height of the inner rib of the workpiece × 2; the length of the thin-walled cylindrical inner rib forming section = the width of the inner rib of the workpiece × 0.5; The circumferential surface of the movable core mold forming section (10) is a stepped surface. The section closest to the movable core mold flange is the movable core mold thin-walled cylindrical forming section, and the diameter of the movable core mold thin-walled cylindrical forming section is the same as the diameter of the fixed core mold thin-walled cylindrical forming section. The section furthest from the movable core mold flange is the movable core mold thin-walled cylindrical inner rib forming section, and the diameter of the movable core mold thin-walled cylindrical inner rib forming section is the same as the diameter of the fixed core mold thin-walled cylindrical inner rib forming section. The length of the movable core mold thin-walled cylindrical inner rib forming section is equal to the width of the inner rib of the workpiece × 0.

5. The diameter of the movable core mold flange (9) is the same as the outer diameter of the spinning blank fixed section 13. The axial length L1 of the movable core mold flange is 15-20 mm.

2. The spinning mandrel with annular inward ribs for thin-walled cylindrical parts as described in claim 1, characterized in that, The end face between the movable core mold flange (9) and the movable core mold connecting section (8) has an axially protruding annular boss. The diameter of the annular boss is 20 mm smaller than the diameter of the thin-walled cylindrical forming section of the movable core mold. Screw holes for connecting the tail rod are evenly distributed on the end face of the annular boss.

3. The spinning mandrel with annular inward ribs for thin-walled cylindrical parts as described in claim 1, characterized in that, The end face of the movable core mold flange near the movable core mold connecting section (8) is machined with an annular positioning groove with a depth of 2mm and a width of Lp. The width Lp of the annular positioning groove is 0.5mm larger than the diameter of the positioning screw 4. When the positioning screw contacts the movable core mold (2), the center of the diameter of the positioning screw is located on the pitch circle of the annular positioning groove.

4. The spinning mandrel with annular inward ribs for thin-walled cylindrical parts as described in claim 1, characterized in that, The large-diameter section of the fixed core mold (1) is the fixed core mold connecting section (6), and the small-diameter section is the fixed core mold forming section (7); the fixed core mold connecting section is connected to the transfer plate of the spinning machine.

5. The spinning mandrel with annular inward ribs for thin-walled cylindrical parts as described in claim 1, characterized in that, There is a groove at the center of the end face of the fixed core mold connecting section (6) for assembly with the spinning machine adapter plate; there is a conical groove at the center of the end face of the thin-walled cylindrical inner rib forming section for assembly with the movable core mold (2).

6. The spinning mandrel with annular inward ribs for thin-walled cylindrical parts as described in claim 1, characterized in that, The ferrule (3) is a 1 / 4 circle arc plate, and the inner diameter R of the arc plate is equal to the outer diameter of the movable mandrel flange (9) × 0.

5. The inner surface of the arc plate has a circumferential groove, which is a groove for fixing the fixed section of the spinning blank and the movable mandrel flange. The groove width L is (L1+L2)+0.3~0.5mm. Wherein, L1 is the axial length of the movable mandrel flange and L2 is the axial length of the fixed section of the spinning blank. The groove depth h is 10~12mm. The thickness of the bottom of the ferrule groove is H, where H=5~8mm.

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