Manufacturing method of bearing bush bending and shaping die, die and cavity grinding device

Abstract

The invention belongs to the technical field of metal plastic processing dies, and particularly relates to a manufacturing method of a bearing bush bending and shaping die, the die and a cavity grinding device. The manufacturing method comprises the steps that cold work die steel is adopted as a material; sequentially carrying out blanking, rough milling and linear cutting on the blank to roughly machine a cavity; quenching and secondary tempering heat treatment including subzero treatment are carried out; carrying out finish machining on the cavity by adopting low-speed wire cutting; rough grinding is conducted on the working face of the cavity through a grey cast iron grinding rod with a specific thread groove in the surface, then precise polishing is conducted through a multi-stage diamond grinding agent, and the surface roughness reaches Ra0.2 or below; and finally, the whole mold is subjected to physical vapor deposition coating treatment. The working cavity of the manufactured mold has extremely low surface roughness and excellent geometric accuracy, and is covered with the super-hard wear-resistant coating, so that the wear resistance and the adhesion resistance are remarkably improved, and the service life of the mold is remarkably prolonged. The bearing bush bending and shaping die solves the technical problems that a bearing bush bending and shaping die is poor in precision retentivity and short in service life.

Description

Technical Field

[0001] This invention relates to the field of metal plastic forming mold technology, specifically to a mold for bending and forming bearing bushes of engine crankshafts, a manufacturing method thereof, and a grinding device for the mold cavity. Background Technology

[0002] The bearing shell is a critical sliding bearing in the crankshaft connecting rod assembly of an engine. It typically employs a thin-walled steel backing structure, with its inner surface coated with a wear-resistant and friction-reducing alloy layer such as copper-aluminum alloy, high-tin aluminum alloy, or Babbitt alloy to reduce friction loss, improve lubrication performance, and extend service life. To meet assembly precision and interference fit requirements, the bearing shell needs to be processed into a specific geometry through a cold extrusion forming process. Among these processes, the bearing shell bending and shaping die is a key piece of equipment for achieving high-precision and high-efficiency forming. It is generally used in conjunction with a high-speed servo press, which can complete the pre-bending and final shaping of the bearing shell within a very short processing cycle.

[0003] Currently, the high-performance bearing bending and forming dies used in China mainly rely on imports, which generally suffer from long delivery cycles (standard delivery time is about 2.5 months), high procurement costs, and large fluctuations in die lifespan. Of particular note is the fact that the die forming surface—namely, the central arc cavity and its entrance transition area—requires extremely stringent processing precision and surface quality. Traditional processes often rely on expensive equipment such as dedicated CNC cylindrical grinding machines for final finishing and polishing, resulting in high equipment investment and high technical barriers, severely restricting the localization and large-scale application of this type of die.

[0004] In existing manufacturing processes, key indicators such as the cylindricity of the mold cavity (generally required to be ≤0.006mm), the perpendicularity of the bottom surface (≤0.006mm), and the surface roughness of the working surface (must reach Ra0.2 or below) are difficult to control stably at the same time. During processing, wire electrical discharge machining may produce a "white layer" on the surface. If the abrasive cleaning is not thorough or mixed during the polishing process, it is very easy to cause secondary damage to the processed surface. These problems not only affect the molding accuracy and surface consistency of the mold, but also reduce the adhesion of the subsequent physical vapor deposition (PVD) coating, thus directly affecting the overall service life and molding stability of the mold.

[0005] Therefore, there is an urgent need to develop a bearing bush bending and shaping mold and its manufacturing method that can achieve import substitution, have a shorter manufacturing cycle, lower overall cost, and can reliably guarantee high-precision forming surface quality and ultra-long service life, so as to overcome the defects of existing technologies such as strong dependence on external equipment, high process cost, insufficient processing consistency and life reliability. Summary of the Invention

[0006] The present invention aims to provide a high-precision, high-wear-resistant, and long-life bearing bending and forming mold and its efficient and stable manufacturing method. It also provides a bearing bending and forming mold for precision grinding of the mold cavity, so as to solve the problems of poor surface roughness, easy wear, and low processing efficiency of the mold in the prior art.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] In a first aspect, the present invention provides a method for manufacturing a bearing bush bending and shaping mold, comprising the following steps:

[0009] S1. Material preparation: High wear-resistant cold work die steel is used as the die material;

[0010] S2. Rough machining: The mold blank is cut into blanks, rough milled to form the outer shape and bolt holes, and wire cut to process the middle arc and keyway.

[0011] S3. Heat treatment: The mold is subjected to quenching and secondary tempering heat treatment to improve its overall hardness and dimensional stability.

[0012] S4. Precision machining: The middle arc and keyway are precision machined using slow wire EDM.

[0013] S5. Grinding and polishing: Use gray cast iron grinding rods to grind and polish the middle arc working surface in multiple stages to make its surface roughness reach below Ra0.2;

[0014] S6. Surface strengthening: The entire mold is treated with physical vapor deposition coating to enhance its surface wear resistance and corrosion resistance.

[0015] In addition to the above-mentioned technical features, the present invention has also made optimizations and improvements in the following aspects:

[0016] As a preferred embodiment of the present invention, the heat treatment process includes three high-temperature temperings at a temperature not lower than 510°C, and includes a cryogenic treatment step to further eliminate internal stress and stabilize the microstructure.

[0017] As a preferred technical solution of the present invention, the grinding and polishing steps specifically include: firstly, using a gray cast iron grinding rod with threaded grooves on the surface for rough grinding; then, sequentially using multi-level diamond abrasives from coarse to fine and corresponding polishing wheels for multi-level fine polishing until the target roughness is achieved.

[0018] As a preferred embodiment of the present invention, the physical vapor deposition coating is a TiCN coating or a TiAlN coating, and the coating thickness is not greater than 0.005 mm, so as to ensure wear resistance while avoiding affecting dimensional accuracy.

[0019] As a preferred technical solution of the present invention, the gray cast iron bar used for rough grinding has a diameter 0.01 mm smaller than the diameter of the central arc of the mold, and has a threaded groove with a pitch ≥ 30 mm and a depth of 0.5 to 0.8 mm on its surface. The mold is moved back and forth on a lathe at a speed of 25 to 38 r / min for rough grinding. This design is conducive to chip removal and efficient grinding.

[0020] Secondly, the present invention provides a bearing bush bending and shaping mold, manufactured using any one of the manufacturing methods described in the first aspect above. The mold includes a mold body, the surface roughness of the working surface of the central arc-shaped cavity of the mold body is not higher than Ra0.2, and the surface is covered with a physical vapor deposition coating. Further, the cylindricity of the working arc surface is not greater than 0.002 mm, and the perpendicularity of its bottom surface is not greater than 0.006 mm. The mold body is preferably made of cold work die steel KD11S, and its overall hardness is HRC58-60.

[0021] Thirdly, the present invention provides a cavity grinding apparatus for manufacturing the bearing bending and shaping mold described in the second aspect above, comprising:

[0022] The grinding rod body has a working section diameter that matches the diameter of the mold cavity to be processed, and its surface is provided with spiral grooves for accommodating abrasive and removing chips.

[0023] A drive mechanism for driving the grinding rod body to rotate about its own axis;

[0024] The fixture is used to clamp the mold to be processed and can drive the mold to move back and forth along the axis of the grinding rod body to achieve uniform grinding of the cavity.

[0025] This application systematically integrates and deeply couples four major technical modules: high-performance material selection, multi-stage precision heat treatment, composite ultra-precision machining, and physical vapor deposition coating, forming a mutually reinforcing and synergistic organic whole. This closed-loop design of the technology chain enables breakthroughs in mold performance across three dimensions: lifespan, precision, and surface functionality, specifically manifested in the following technical effects:

[0026] 1. The three-pronged matrix strengthening effect of "materials-heat treatment-structural precision"

[0027] Synergy between materials and heat treatment: Special cold work die steel KD11S was selected, whose composition system (high Cr, Mo, V content) provides a material basis for subsequent high-temperature tempering (≥510℃) and deep cryogenic treatment. This combination of "quenching + multiple tempering + deep cryogenic treatment" not only achieves high hardness of HRC 58–60, but also significantly refines grains, transforms retained austenite, and releases internal stress, enabling the die matrix to simultaneously possess a "toughened" state of high hardness, high toughness, and low stress.

[0028] Structural precision supports performance: On a toughened substrate, the cylindricity of the working arc surface is controlled to ≤0.002mm and the perpendicularity of the bottom surface to ≤0.006mm through slow wire EDM and composite grinding processes. This ultra-precise geometry, combined with the toughened substrate, allows for uniform stress distribution when the mold is subjected to high-speed alternating impact loads, avoiding the initiation of microcracks caused by localized stress concentration, thereby extending the mold's fatigue life to the theoretical limit.

[0029] 2. Functional integration of the interface between grinding process, surface roughness, and coating adhesion.

[0030] The step-by-step coupling of grinding and polishing: A gray cast iron grinding rod (with specific threaded grooves) is used for rough grinding, whose "micro-cutting + micro-extrusion" action efficiently removes excess material and initially levels the surface. This is followed by multi-stage polishing using W40 to W0.5 diamond abrasives, gradually eliminating microscopic undulations. This "rough grinding and shaping → fine polishing to mirror finish" process chain ensures shape accuracy while precisely controlling surface roughness to Ra < 0.2, achieving a mirror finish of SPI A2 level or higher.

[0031] Enhanced interface between the mirror-like substrate and the PVD coating: The aforementioned mirror-like surface not only possesses an extremely low coefficient of friction and anti-adhesion properties, but more importantly, it provides a smooth, clean, and highly active deposition interface for the subsequent PVD coating (TiCN / TiAlN, ≤0.005mm). A strong metallurgical bond is formed between the coating and the substrate, significantly improving adhesion and making the coating less prone to peeling under long-term high-speed impact, truly demonstrating its ultra-hard, wear-resistant, and high-temperature-resistant protective functions.

[0032] 3. Reconstruction of the manufacturing ecosystem through "process innovation - equipment replacement - cost control"

[0033] Breaking through equipment bottlenecks through technological innovation: A creative approach using a "lathe + gray cast iron grinding rod" to replace a dedicated CNC cylindrical grinding machine for ultra-precision machining of cavities was proposed. This process leverages the widespread availability of lathes, the self-grinding properties of cast iron rods, and the ultra-precision machining capabilities of diamond abrasives to form a low-cost, highly flexible, and easily implemented precision machining solution.

[0034] Cost and cycle optimization across the entire process chain: From the selection of domestically produced materials, optimization of heat treatment processes, and reasonable arrangement of processing steps (such as separation of rough and fine machining and precise control of allowances), to the final localization of coating treatment, the entire manufacturing chain has achieved cycle compression (from 2.5 months to 1 month) and cost control. While ensuring performance that surpasses imported molds, it has built a fully independent and controllable high-performance mold manufacturing system.

[0035] 4. Overall performance: Simultaneous improvement in lifespan, accuracy, and stability.

[0036] The deep integration of the above-mentioned technical features ultimately results in a comprehensive improvement in the overall performance of the mold:

[0037] Life indicators: Under high-speed continuous stamping (cycle time < 1s) conditions, the die life is 5-10 times longer than that of conventional processes, with small life dispersion and high reliability.

[0038] Precision retention: The cylindricity change of the working arc surface is ≤0.001mm after long-term use, and the dimensional stability is excellent.

[0039] Product qualification rate: The molded bearing bushes have uniform wall thickness, no scratches on the surface, and improved adhesion, with a first-pass qualification rate of ≥99.5%.

[0040] In summary, this application integrates technologies across the entire chain, from material matrix to functional surface, and from geometric precision to process implementation. This not only solves the industry pain points of imported molds, such as long cycle time, high cost, and unstable lifespan, but also forms a set of high-performance precision molds that can be replicated and promoted, with significant technological advancement and industrial application value. Attached Figure Description

[0041] Figure 1 This is a flowchart of the manufacturing method of the bearing bending and shaping mold of the present invention. Detailed Implementation

[0042] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0043] I. Explanation of descriptive terms used in this invention

[0044] The embodiments provided in conjunction with the technical solutions of this invention are intended to make the invention more thorough and complete, and to fully express the scope of the invention to those skilled in the art. It should be noted that unless otherwise specifically stated in this invention, the relative arrangements of components described in these embodiments should be interpreted as merely exemplary and not as a limitation on the technical solutions of this invention.

[0045] In this invention, when directional terms such as "up," "down," "left," "right," "bottom," and "top" are used, they are defined relative to the directions shown in the accompanying drawings and are used only to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly. These or other directional terms should not be construed as restrictive terms.

[0046] In this invention, the terms "a," "an," "an," "the," and similar words used do not indicate quantity limitations and can represent singular or plural. The terms "comprising," "including," "having," and any variations thereof used in this invention are intended to cover non-exclusive inclusion; the terms "first," "second," "third," etc., used in this invention are merely to distinguish similar objects and do not represent a specific ordering of objects.

[0047] In this invention, when a specific device is described as being located between a first device and a second device, an intermediary device may or may not be present between the specific device and the first or second device. When a specific device is described as being connected to other devices, the specific device may be directly connected to the other devices without an intermediary device, or it may be not directly connected to the other devices but have an intermediary device.

[0048] Furthermore, this invention does not discuss in detail the technologies and equipment known to those skilled in the art, but where appropriate, such technologies and equipment should be considered part of the specification.

[0049] II. The core technical problem to be solved by the technical solution of this application

[0050] Existing high-performance bearing bending and forming dies mainly rely on imports, resulting in long delivery cycles and high procurement costs. During the manufacturing process, key precision indicators such as the cylindricity, perpendicularity, and surface roughness of the die cavity are difficult to guarantee consistently. The machining process heavily relies on expensive equipment such as specialized CNC cylindrical grinding machines, leading to high technical barriers and investment costs. Furthermore, wire electrical discharge machining (EDM) is prone to producing damaging "white layers," and if subsequent polishing processes involve incomplete abrasive cleaning or the use of mixed abrasives, secondary surface damage can occur, affecting forming consistency and the adhesion of physical vapor deposition coatings. Ultimately, this results in large fluctuations in die lifespan and insufficient reliability, severely restricting the localization and large-scale application of this key process equipment.

[0051] III. Based on the above problems, the present invention specifically provides a technical solution to solve the above problems, which will be described below in conjunction with the appendix. Figure 1 The present invention will be described in detail with reference to specific embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the invention.

[0052] The core of this invention is to provide a method for manufacturing a bearing bending and shaping mold, a mold obtained by the method, a special grinding device for processing the mold, and a bearing manufacturing method using the mold.

[0053] Example 1: Manufacturing method of bearing bush bending and shaping die

[0054] This embodiment provides a method for manufacturing a bearing bush bending and shaping mold, the detailed steps of which are as follows:

[0055] Step 1: Material preparation and preliminary processing

[0056] This embodiment uses KD11S (a modified version of SKD11) patented cold work die steel from Japan High Frequency Co., Ltd. as the raw material for the die body. The specific steps are as follows:

[0057] Cutting: Use a band saw to cut the KD11S board to a cutting size of 159mm×97mm×89mm.

[0058] Rough milling of the outer shape: On a horizontal milling machine, a disc milling cutter with Zhuzhou carbide YT14 inserts is used to rough mill the blank, leaving a machining allowance of 0.6mm on each side of the outer shape. The machining parameters are: spindle speed S = 380~420r / min, feed rate f = 0.12mm / r, depth of cut 2.5mm.

[0059] Machining bolt holes: On a conventional milling machine, use Φ9mm and Φ15mm drill bits to machine bolt holes for mold mounting and fixing. The rotation speed is S=380~450r / min, with manual feed.

[0060] Step 2: Pre-heat treatment forming process

[0061] After rough machining and before heat treatment, the key forming parts of the mold are pre-machined to release stress:

[0062] Wire EDM pre-processing: Using a fast wire EDM machine, the arc-shaped cavity working surface in the middle of the mold that needs to be formed is cut, leaving a 1mm machining allowance on each side. This step can avoid the risk of cracking caused by abrupt changes in cross-section during subsequent heat treatment.

[0063] Step 3: Heat Treatment

[0064] Quenching and tempering: The mold undergoes vacuum quenching and three high-temperature tempering treatments. The tempering temperature is not lower than 510℃. After heat treatment, the overall hardness of the mold reaches HRC58~60.

[0065] Cryogenic treatment: After heat treatment, cryogenic treatment is performed to further reduce residual austenite, reduce stress concentration inside the mold, and improve dimensional stability and toughness.

[0066] This step utilizes a "hot-cold" synergy between cryogenic treatment and high-temperature tempering to further eliminate micro-stress and refine grains. Its direct technical effect is that the mold achieves high hardness while possessing excellent dimensional stability and toughness, greatly improving dimensional controllability during subsequent wire cutting and polishing processes, and providing an inherent guarantee for achieving micron-level geometric tolerances.

[0067] Step 4: Finishing and Shaping

[0068] After heat treatment, the mold possesses stable high hardness, allowing for precision machining:

[0069] Precision grinding of the outer surface: Using a small surface grinder, the outer reference surface of the mold is ground to ensure the positioning accuracy of subsequent processing.

[0070] Precision cutting and shaping: A slow wire EDM machine is used to finish the working surface of the central arc cavity and the positioning keyway 13 at the bottom. This process is the final dimension machining, with only a polishing allowance of 0.01 to 0.015 mm on each side, in order to remove the deteriorated layer from fast wire EDM and obtain a precise contour.

[0071] The above steps involve precision machining of the arc-shaped cavity 12 and keyway 13 on a dimensionally stable, high-hardness substrate using slow wire EDM. The key to this process is precisely transferring the stabilized shape after heat treatment to the final contour with a polishing allowance of only 0.01-0.015mm on each side. This replaces the traditional method relying on dedicated grinding machines. The combined effect is that, while avoiding grinding burns and stress, it provides a "blank" with extremely small allowance and precise contour for the next critical polishing process, keeping machining errors within a range that can be easily corrected in the final step.

[0072] Step 5: Precision grinding and polishing of the working surface of the cavity

[0073] This is the core step to ensure the final precision and surface quality of the mold:

[0074] Rough grinding: Prepare a gray cast iron grinding rod. The diameter of its working section is 0.01 mm smaller than the designed diameter of the arc cavity 12 in the middle of the mold, the length is 230 mm, and the straightness is less than 0.01 mm. Thread grooves with a pitch ≥ 30 mm and a depth of 0.5–0.8 mm are machined on the surface of the rod to contain and transport the abrasive.

[0075] Apply an appropriate amount of W40 diamond abrasive to the grooves of the abrasive bar.

[0076] The grinding rod is clamped on a conventional lathe and rotated at a speed of S = 25-38 r / min.

[0077] The arc-shaped cavity 12 of the mold is inverted onto the rotating grinding rod, and grinding pressure is applied by relying on the weight of the mold itself.

[0078] The operator holds the mold and moves it back and forth at a constant speed along the axis of the grinding rod, completing a 230mm stroke in approximately 3-5 seconds, for a total of 5 round trips. This rough grinding process evenly removes wire-cutting allowances and preliminarily corrects the surface.

[0079] Note: For safety reasons, the rotation speed must not exceed 40 r / min during this process.

[0080] Multi-stage precision polishing: After rough grinding, finer diamond abrasives and corresponding polishing wheels (such as wool wheels) are used sequentially to polish the working surfaces of the cavity. The specific process is as follows:

[0081] Use W20 diamond abrasive and a new polishing wheel for polishing. Before polishing, the mold surface must be thoroughly cleaned and the polishing tools replaced to ensure that there are no W40 coarse particles left over from the previous process.

[0082] Repeat the polishing and cleaning process by replacing the diamond abrasives in sequence with W10, W5, W1, and W0.5 and the corresponding new polishing wheels.

[0083] Ultimately, the surface roughness of the cavity working surface reaches below Ra0.2, exhibiting a mirror-like effect of SPIA2 level or higher. This not only reduces the frictional resistance during bearing forming but also provides an excellent adhesion substrate for subsequent PVD coating.

[0084] This step achieves the core goal of "achieving ultra-high precision with low-cost equipment" by integrating grinding and polishing processes, combining tooling innovation and process control.

[0085] A low-cost, high-precision grinding device is achieved using a self-made gray cast iron grinding rod. Its diameter is specifically reduced by 0.01mm, combined with a surface-deep threaded groove structure, enabling continuous supply of grinding compound, uniform pressure, and smooth chip removal during low-speed (25-38 r / min) rotation on a lathe. The mold relies on its own weight to adhere to the grinding surface, avoiding additional errors introduced by complex fixtures. This combination solves the problem of uniform, controllable, and precise grinding of small internal arc surfaces on conventional machine tools, achieving results comparable to dedicated grinding machines at a significantly lower cost.

[0086] Contamination control in the multi-stage polishing process: Multi-stage polishing with diamond abrasives from W40 to W0.5 is not simply a matter of changing the grit size. The key lies in a strict process of "thorough cleaning and simultaneous tool replacement." Before each stage of polishing, all residual coarse abrasive particles from the previous stage must be completely removed and the polishing wheel replaced. This control measure directly ensures a step-by-step purification and improvement in surface quality, effectively preventing "reverse damage" caused by coarse particles scratching the already polished, fine surface. This is the process guarantee for ultimately achieving a mirror finish below Ra0.2 (SPIA2 level). This mirror finish not only reduces friction but also provides an extremely clean and highly active substrate for subsequent coatings.

[0087] Step 6: Surface strengthening treatment

[0088] PVD Coating: The polished mold is coated with a physical vapor deposition (PVD) coating. TiCN or TiAlN compounds (e.g., Balchas coating) are used as the coating material, and the coating thickness is controlled to be no more than 0.005 mm. This ultra-hard, wear-resistant coating significantly improves the surface hardness, wear resistance, and anti-adhesion properties of the mold.

[0089] Post-coating treatment: Use W10 metallographic sandpaper or diamond abrasive paste with a fine wool wheel to lightly sand the non-working surfaces after PVD coating to remove any tiny burrs that may be caused by coating deposition.

[0090] Step 7: Inspection

[0091] Final inspection: The mold is subjected to full-dimensional inspection using precision instruments such as a Zeiss coordinate measuring machine. This ensures that: the cylindricity of the working surface of the central arc cavity is no greater than 0.002 mm, the perpendicularity of its bottom surface to the axis is no greater than 0.006 mm, and the surface roughness meets the standards. After passing inspection, it is marked using a laser marking machine.

[0092] Through the above methods, especially the series of coordinated process steps of "pre-processing to release stress before heat treatment → three high-temperature tempering and deep cryogenic treatment to stabilize dimensions → slow wire cutting to ensure shape → unique gray cast iron grinding rod process to achieve high precision and ultra-smooth surface → ultra-thin PVD coating to strengthen the surface", a high-performance bearing bending and shaping mold was successfully manufactured.

[0093] This manufacturing method, through the integration of interconnected technologies, eliminates the need for expensive and dedicated CNC cylindrical grinding machines, and achieves the same or even higher precision using conventional equipment and innovative tooling.

[0094] This method provides a reliable processing foundation through "pre-processing stress guidance" + "composite heat treatment for dimensional stability"; "slow wire EDM precision transfer" + "innovative grinding and polishing of cast iron rods" achieves ultra-high precision and surface finish on a low-cost path; "ultra-smooth substrate" + "ultra-thin reinforcing coating" ultimately integrate high geometric accuracy and ultra-long service life.

[0095] In terms of technical effectiveness, the synergistic effect of the entire technology chain has enabled domestically produced molds to achieve comprehensive breakthroughs in cycle time (about 1 month), cost (no need for special grinding machines), and core performance (cylindricity ≤ 0.002mm).

[0096] The mold manufacturing cycle can be reduced to about one month, and the mold produced has a stable lifespan. Tests have shown that it can reach and exceed the highest lifespan level of the original imported molds, making the overall cost highly competitive.

[0097] Example 2: Bearing Bending and Shaping Die

[0098] This embodiment provides a bearing bending and shaping mold manufactured by the manufacturing method described in Embodiment 1.

[0099] The mold includes a mold body. The mold body is made of cold work die steel KD11S and has an overall hardness of HRC58-60 after heat treatment.

[0100] The mold body has a crucial central arc-shaped working surface for bending and shaping the bearing blank. The specific parameter requirements for this working surface are as follows:

[0101] The surface roughness is not higher than Ra0.2;

[0102] The surface is covered with a physical vapor deposition coating, such as a TiCN or TiAlN coating, with a coating thickness of no more than 0.005 mm;

[0103] Cylindricity not greater than 0.002 mm;

[0104] The verticality of its bottom surface is no more than 0.006 mm.

[0105] The mold body is also provided with bolt holes for installation and fixing, and keyway 13 for precise positioning.

[0106] Due to the high-precision manufacturing method employed in Example 1, this mold possesses extremely low roughness, extremely high geometric accuracy (cylindricity, perpendicularity), and an ultra-hard wear-resistant coating on its core working surface. When used in actual high-speed servo presses to bend and shape steel-aluminum composite bearing blanks, it ensures stable dimensions, high consistency, and good surface quality of the bearing products.

[0107] This mold possesses a triple combination of properties: ultra-high precision geometry, ultra-smooth low-friction surface, and ultra-thin high-strength coating. This allows it to achieve near-perfect material flow control, extremely low forming friction and adhesion tendency, and uniformly distributed impact loads during high-speed stamping (cycle time < 1 second) of bearing bushes. Simultaneously, the uniform load distribution and excellent surface properties result in exceptional wear and fatigue resistance, significantly extending its service life and enabling a high-quality domestic replacement of imported molds.

[0108] Example 3: Cavity grinding device for manufacturing bearing bending and shaping molds

[0109] This embodiment provides a dedicated device for the grinding process described in step five of Embodiment 1. This cavity grinding device mainly includes:

[0110] The grinding rod body is made of gray cast iron. Its working section diameter matches the diameter of the mold cavity to be processed (typically slightly smaller by 0.01 mm). The working section surface has spiral grooves (threaded grooves) for accommodating the abrasive.

[0111] Drive mechanism: used to clamp and drive the grinding rod body to rotate about its own axis.

[0112] A clamp is used to hold the mold to be processed and can drive the mold to move back and forth along the axis of the grinding rod body. It is usually held by the operator or a special clamp.

[0113] Working principle: The drive mechanism rotates the grinding rod coated with abrasive, and the fixture moves the mold so that its cavity 12 fits onto the grinding rod and moves axially. Through mechanical grinding, the working surface of the mold cavity is precisely machined.

[0114] Technical effect description: The device has a simple structure and cleverly utilizes the self-lubricating properties and easy abrasive grain embedding characteristics of gray cast iron. When used with a conventional lathe, it can achieve the final forming and polishing of high-precision mold cavities, completely replacing expensive special CNC grinding machines. It is a key tooling innovation for reducing mold manufacturing costs.

[0115] This combination of "simple equipment + intelligent tooling" perfectly replaces the specialized internal and external cylindrical grinding machines that require complex CNC systems and high-rigidity structures.

[0116] This device simplifies the complex control issues of "precise tool setting," "uniform pressure," and "continuous abrasive grain renewal" required for grinding into easy-to-operate mechanical actions through the ingenious design of the tooling. This greatly reduces equipment investment while reliably achieving precision machining of mold cavities.

[0117] Example 4: Manufacturing method of engine bearing bush

[0118] This embodiment provides a method for manufacturing engine bearings using the bearing bending and shaping mold described in Embodiment 2.

[0119] The method includes the following steps:

[0120] First, the steel-aluminum composite sheet is stamped and blanked to obtain the flat blank of the bearing bush.

[0121] Then, the above-mentioned blank is placed into a high-speed servo press, and the bearing bending and shaping die prepared in Example 2 is used to perform bending and shaping processes on the blank. The upper die punch of the press quickly and accurately forms the bearing semi-finished product in a cycle time of less than 1 second, according to the action sequence of bending the middle part first and then shaping the two ends.

[0122] Technical benefits: Utilizing domestically produced molds with ultra-high surface precision and excellent surface quality, this method produces bearing semi-finished products with high dimensional accuracy and consistent surface quality, laying a solid foundation for subsequent wear-resistant alloy coating and assembly. Simultaneously, the long-life molds ensure the stability and economy of large-scale production.

[0123] This embodiment illustrates the bearing manufacturing method using the mold described in Embodiment 2, demonstrating the downstream transmission effect of "good mold leading to good process". This method uses a domestically produced high-performance bearing bending and shaping mold on a high-speed servo press to bend and shape blanks of steel-aluminum composite plates.

[0124] In summary, through the technical solutions of Examples 1 to 4, this invention constructs a complete technical system encompassing mold materials, processing technology, specialized tooling, and final application. The technical features of each example are mutually supportive and deeply coupled: high-quality materials are the foundation, integrated processes are the core, specialized equipment is the key, high-performance molds are the achievement, and efficient manufacturing is the ultimate value realization. This system successfully breaks the foreign technological monopoly, achieving comprehensive optimization of the bearing bending and shaping mold in four dimensions: precision, lifespan, cost, and cycle time, providing a technical path for the localization of high-end molds.

[0125] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

[0126] Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them; when the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

Claims

1. A method for manufacturing a bearing bush bending and shaping mold, characterized in that, Includes the following steps: Cold work die steel is used as the die material; The mold blank is sequentially cut, rough milled to include the outer shape and bolt holes, and wire-cut to process the middle arc and keyway. The mold undergoes quenching and secondary tempering heat treatment; The intermediate arc and keyway are precision machined using slow wire EDM. The middle arc working surface is ground and polished using a gray cast iron grinding rod to achieve a surface roughness of Ra0.2 or less. The entire mold is treated with physical vapor deposition coating.

2. The manufacturing method according to claim 1, characterized in that, The heat treatment process includes three high-temperature temperings, with a tempering temperature of not less than 510°C, and also includes a cryogenic treatment step.

3. The manufacturing method according to claim 1, characterized in that, The steps of grinding and polishing the intermediate arc working surface using a gray cast iron grinding rod include: The intermediate arc working surface is rough-ground using a gray cast iron grinding rod with threaded grooves on its surface. Then, the working surface is polished in stages using multi-level diamond abrasives of varying coarseness and corresponding polishing wheels until the surface roughness reaches below Ra0.

2.

4. The manufacturing method according to claim 1, characterized in that, In the grinding step, a gray cast iron bar with a diameter 0.01 mm smaller than the diameter of the central arc of the mold is used to perform rough grinding by moving the mold back and forth on a lathe at a speed of 25-38 r / min.

5. The manufacturing method according to claim 3 or 4, characterized in that, The gray cast iron bar used for rough grinding has a threaded groove with a pitch of ≥30mm and a depth of 0.5~0.8mm on its surface.

6. The manufacturing method according to claim 1, characterized in that, The physical vapor deposition coating is a TiCN coating or a TiAlN coating, and the coating thickness is no greater than 0.005 mm.

7. A bearing bush bending and shaping mold, characterized in that, Made by the manufacturing method of any one of claims 1 to 6, comprising a mold body, wherein the surface roughness of the working surface of the intermediate arc-shaped cavity of the mold body is not higher than Ra0.2, and the surface is covered with a physical vapor deposition coating.

8. The bearing bush bending and shaping mold according to claim 6, characterized in that, The cylindricity of the working arc surface is no greater than 0.002 mm, and the perpendicularity of its bottom surface is no greater than 0.006 mm.

9. The bearing bush bending and shaping mold according to claim 1, characterized in that, The mold body is made of cold work die steel KD11S, and the overall hardness is HRC58~60.

10. A cavity grinding apparatus for manufacturing a bearing bending and shaping mold as described in any one of claims 6 to 8, characterized in that, include: The grinding rod body has a working section diameter that matches the diameter of the mold cavity to be processed, and a spiral groove is provided on its surface. A drive mechanism for driving the grinding rod body to rotate about its own axis; A clamp is used to hold the mold to be processed and can drive the mold to move along the axial direction of the grinding rod body.

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