A mold cavity integrated forming machining process

Abstract

This application discloses an integrated molding process for mold cavities, relating to the field of mold processing technology. The process includes S1, homogenization pretreatment of the entire material: selecting a single piece of the integrated mold blank, grinding and removing impurities, degreasing and rust, and performing non-destructive testing to eliminate defective blanks containing pores, cracks, and inclusions; and subjecting qualified blanks to gradient tempering heat treatment. This application utilizes an integrated, one-time clamping molding structure, combined with multiple sets of original quantitative calculation formulas, to achieve precise data-driven control of the entire mold cavity processing process. This eliminates assembly gaps, cumulative positioning errors, and human experience deviations inherent in traditional split-processes. Combined with dynamic thermal deformation correction, quantitative stress elimination, and gradient nanopolishing processes, it effectively solves problems such as poor cavity precision, weak surface consistency, high residual stress, and easy deformation in the later stages, improving cavity dimensional accuracy, surface quality, and structural stability, and eliminating defects such as flash and dimensional deviations.

Description

Technical Field

[0001] This invention relates to the field of mold processing technology, and in particular to an integrated molding process for mold cavities. Background Technology

[0002] Mold cavities are core precision components of molding dies used in injection molding and die casting. Their machining accuracy, surface quality, and structural stability directly determine the molding accuracy, appearance quality, and service life of the finished product. Currently, the mainstream mold cavity machining process in the industry generally adopts the traditional process mode of separate module machining and subsequent assembly. This requires each cavity module to be cut, milled, and clamped and positioned separately, and finally assembled with bolts and locating pins, followed by manual mold repair and correction. This traditional machining method has many inherent technical defects in actual production and is difficult to meet the high precision, high consistency, and long service life production requirements of high-end precision irregular molds.

[0003] First, traditional modular molding processes suffer from unavoidable structural errors. Multi-module modular processing requires multiple disassembly and reassembly, and repeated reference switching, which easily leads to a large amount of cumulative positioning errors. Furthermore, after module assembly, there will inevitably be gaps and misalignments, resulting in poor overall cavity contour and dimensional consistency. Molded products are prone to defects such as flash, burrs, and out-of-tolerance dimensions. At the same time, under the long-term high temperature and high pressure cycle of the mold, the spliced ​​structure is prone to loosening, leakage, and local deformation, which significantly shortens the service life of the mold.

[0004] Secondly, the control of existing machining process parameters relies heavily on manual experience and lacks quantitative data support. In traditional milling and polishing processes, key process parameters such as cutting speed, feed rate, depth of cut, and polishing parameters are all set by operators based on experience. There is a lack of standardized and quantitative matching formulas and error correction mechanisms. The material removal rate is poorly adapted to the cavity structure and blank material. The machining is highly random and the process is not easily reproducible. Complex irregular curved cavities are prone to problems such as overcutting, undercutting, and surface distortion, resulting in unstable finished product yield. Summary of the Invention

[0005] (a) Technical problems to be solved

[0006] To address the problems existing in the prior art, the present invention provides an integrated molding process for mold cavities.

[0007] (II) Technical Solution

[0008] To achieve the above objectives, the present invention is implemented through the following technical solution: an integrated molding process for mold cavities, including S1, whole material homogenization pretreatment: selecting a whole blank of integrated mold, grinding and removing impurities, degreasing and removing rust, and non-destructive testing of the blank to remove defective blanks containing pores, cracks, and slag inclusions; subjecting qualified blanks to gradient tempering heat treatment to obtain an integrated substrate with uniform hardness and consistent initial internal stress value;

[0009] S2. Cavity Quantitative Modeling and Tolerance Prediction: Construct a three-dimensional model of the cavity based on the product molding standard. Combine the plastic shrinkage rate and processing deformation error, complete the model size pre-compensation through the cavity precise molding size calculation formula. At the same time, predict the processing deformation range based on finite element simulation and generate a CNC machining path with quantitative tolerance threshold.

[0010] S3. Integrated clamping and positioning with reference: The process adopts a one-time clamping reference locking process. The whole blank is positioned and calibrated by a high-precision reference tooling, which limits the clamping flatness and perpendicularity deviation. There is no secondary disassembly or reference switching throughout the process, eliminating the cumulative error of multiple positioning.

[0011] S4. Adaptive Layered Quantitative Milling Forming: Based on the preset material removal rate calculation formula, the cutting parameters of roughing, semi-finishing, and finishing milling are matched. Layered progressive integrated milling is adopted. Combined with real-time temperature monitoring data, the cutting feed is dynamically fine-tuned through the thermal deformation deviation correction formula to achieve seamless integral forming of the cavity.

[0012] S5. Gradient nano-precision polishing: The inner wall of the milled cavity is polished using a multi-level gradient polishing process. Different mesh sizes of grinding media and polishing parameters are matched according to the curvature of the cavity surface to remove micro-tool marks and reduce surface roughness step by step, ensuring the uniformity of the cavity surface.

[0013] S6. Vacuum Quantitative Stress Relief: Based on the billet material and machining allowance, match the corresponding low-temperature aging process parameters to accurately eliminate residual internal stress generated during milling and polishing in a vacuum environment, and suppress the later deformation of the cavity.

[0014] S7. Full-dimensional precision verification and protection: Quantitative testing is performed on the dimensional accuracy, curvature, surface roughness, and deformation of the molding cavity. After all indicators meet the standards, a nano-protective coating is applied to complete the integrated molding process of the mold cavity.

[0015] As a preferred embodiment of the integrated molding process for mold cavities described in this invention, in step S2, the formula for calculating the precise molding dimensions of the cavity is:

[0016] in, The final design and machining dimensions of the mold cavity are in mm. The nominal dimensions of the product are in mm. This represents the average shrinkage rate of the plastic material. Product dimensional tolerances, in mm; To compensate for the tolerance in mold processing, the value is taken as 1 / 4 to 1 / 6 of the product size tolerance.

[0017] As a preferred embodiment of the mold cavity integrated molding process of the present invention, in step S4, the material removal rate is calculated using the following formula:

[0018] in, Material removal rate, in mm³ / min; This refers to the milling spindle speed, in r / min. Feed per revolution, in mm / r; The depth of cut is axial, in mm. Radial cutting width, in mm; rough milling control based on graded matching parameters according to formula. Semi-finish milling control: 8000–12000 mm³ / min 3000~5000mm³ / min, precision milling control The flow rate is 500–1500 mm³ / min.

[0019] As a preferred embodiment of the mold cavity integrated molding process of the present invention, in step S4, the thermal deformation deviation correction formula is:

[0020] in, This is the real-time thermal deformation correction amount, in mm; The coefficient of thermal expansion of the billet material; The temperature difference between the real-time processing temperature and the standard constant temperature of 22℃ is expressed in °C. These are the reference dimensions for cavity machining, in mm; The deformation correction coefficient is set to 0.0001 to 0.0003. During the machining process, the cutting parameters are finely adjusted in real time based on the calculated correction amount to control the thermal deformation error to ≤0.002mm.

[0021] As a preferred embodiment of the integrated molding process for mold cavities described in this invention, in step S1, the gradient tempering heat treatment parameters are as follows: heating to 830-870℃ and holding at that temperature for 2-4 hours; cooling in the furnace to 450℃ in the first stage at a cooling rate of 15℃ / min; and cooling in the furnace to below 300℃ in the second stage before air cooling. After heat treatment, the hardness of the billet is uniformly maintained at HRC29-33, the initial deformation of the billet is ≤0.008mm, and the internal residual stress is ≤80MPa.

[0022] As a preferred embodiment of the integrated molding process for mold cavities described in this invention, in step S3, the integrated clamping and positioning standard is as follows: calibration is performed using a dial indicator in conjunction with a laser tool setter, the flatness error of the worktable is ≤0.003mm, the perpendicularity error is ≤0.004mm, the clamping reference overlap is 100%, and the locking reference is locked without offset throughout the process, thus completely eliminating the cumulative positioning error of traditional multiple clamping.

[0023] As a preferred embodiment of the mold cavity integrated molding process described in this invention, the gradient nano-precision polishing process in step S5 is as follows: First, mechanical rough polishing is performed using 1000-1500 grit abrasion-resistant sandpaper to remove macroscopic milling marks; second, ultra-fine polishing is performed using 2500-3500 grit diamond polishing paste to correct microscopic uneven surfaces; third, mirror-finish polishing is performed using silica polishing liquid with a particle size of 20-50 nm, resulting in a surface roughness Ra ≤ 0.015 μm for the cavity after polishing; for irregular curved surfaces with a radius of curvature < 5 mm, the polishing speed is reduced by 20% to avoid over-polishing deformation of the curved surface.

[0024] As a preferred embodiment of the mold cavity integrated molding process of the present invention, in step S6, the vacuum quantification stress relief parameters are: vacuum degree ≤ 0.07 MPa, temperature rise to 190~

[0025] Maintain a constant temperature of 230℃ for 4–7 hours, with a heating rate of 8–12℃ / h, and allow to cool naturally to room temperature; adjust according to processing residue requirements.

[0026] Force formula Matching the heat preservation time, among which The material stress coefficient, To ensure a milling machining time of ≥95% residual stress relief rate.

[0027] As a preferred embodiment of the mold cavity integrated molding process described in this invention, in step S7, the full-dimensional accuracy verification includes four core indicators: dimensional accuracy, surface contour, flatness, and surface roughness. The verification is performed using a coordinate measuring machine and a laser profilometer. After passing the verification, a nano-ceramic protective coating with a thickness of 6-12 μm is sprayed on, with a coating hardness ≥6H, which significantly improves the wear resistance and corrosion resistance of the cavity.

[0028] (III) Beneficial Effects

[0029] This invention provides an integrated molding process for mold cavities. It offers the following advantages:

[0030] 1. By relying on the integrated one-time clamping and forming architecture of the whole material and combining multiple sets of original quantitative calculation formulas, the entire process of mold cavity processing is standardized and data-driven for precise control. This eliminates the assembly gaps, cumulative errors from multiple positioning, and human experience deviations of traditional processes from the root. Combined with dynamic thermal deformation correction, quantitative stress elimination, and gradient nano-precision polishing technology, it effectively solves the industry pain points of unstable cavity processing accuracy, poor surface consistency, large residual stress, and easy deformation in the later stage. It significantly improves the overall dimensional accuracy, surface finish, and structural stability of the mold cavity, eliminates quality defects such as flash and out-of-tolerance dimensions in product forming, and simplifies cumbersome processes such as assembly, repeated calibration, and secondary mold repair. This shortens the processing cycle, improves the yield rate of finished products and the replicability of the process, and greatly extends the service life of the mold under high temperature and high pressure conditions. It has strong engineering practicality and large-scale promotion value. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This is a flowchart of the overall process steps of the present invention. Detailed Implementation

[0033] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0034] Example 1

[0035] S1. Homogenization Pretreatment of Solid Material: Select a 200mm×150mm×80mm P20 plastic mold steel integrated solid material blank. First, use an 80-mesh industrial flap wheel to grind and remove impurities from the six outer surfaces of the blank, removing oxide scale, forging burrs and machining marks. Then, soak in an alkaline degreasing agent for 15 minutes, followed by high-pressure water jet rinsing to complete degreasing and rust removal, removing surface oil, rust and impurities. After surface treatment, use an ultrasonic non-destructive testing instrument to conduct a full-area inspection of the blank's interior, checking for defects such as pores, cracks, inclusions, and looseness, and selecting defect-free qualified blanks. For qualified billets, a segmented gradient tempering heat treatment process is adopted. Specific parameters are as follows: Heating to 850℃ at a rate of 10℃ / h, holding at that temperature for 3 hours to ensure uniform temperature between the core and surface layers, and full austenitization of the alloy microstructure; The first stage involves furnace cooling to 450℃, with a strictly controlled cooling rate of 15℃ / min to avoid microstructural stress caused by rapid cooling; the second stage involves continuous furnace cooling to 280℃, followed by air cooling to room temperature. After heat treatment, the billet hardness is tested at multiple points using a Rockwell hardness tester, maintaining a uniform overall hardness of HRC31. A high-precision level is used to measure the overall deformation of the billet, which is 0.007mm. A residual stress tester detects the initial internal residual stress of the billet at 72MPa, meeting the requirements for integrated machining substrates.

[0036] S2. Cavity Quantitative Modeling and Tolerance Prediction: For precision injection molded products made of ABS material, the nominal size of the product L0 = 50mm, the product design dimensional tolerance Δ = 0.03mm, the average shrinkage rate of ABS material S = 0.6%, and the mold processing compensation tolerance δ is taken as 1 / 5 of the product tolerance, i.e., δ = 0.006mm. Substitute these values ​​into the formula for calculating the precise molding dimensions of the cavity. The final machining reference dimension of the mold cavity was accurately calculated to be L=50.28mm. Using 3D modeling software, a complete integrated 3D model of the cavity was constructed based on the calculated reference dimension, fully replicating all structural features of the product's irregular curved surfaces, fillets, and grooves. The 3D model was imported into ANSYS finite element simulation software to conduct milling stress simulation, temperature field simulation, and deformation simulation. The cutting deformation range of different curved areas of the cavity was predicted, and structural optimization and path compensation were performed on easily deformable areas such as irregular narrow grooves and small curvature arcs. Finally, a high-precision CNC machining path file with tolerance control within ±0.002mm was generated and imported into the CNC machining center for later use.

[0037] S3. Integrated Baseline Clamping and Positioning: The pre-processed P20 blank is placed on the precision worktable of a vertical CNC machining center and clamped and fixed using a high-precision hydraulic baseline fixture to achieve gapless baseline positioning. After assembly, a dial indicator and laser tool setter are used to calibrate the blank's horizontality, verticality, and baseline coincidence in all aspects. The clamping force of the fixture and the placement position of the blank are finely adjusted. Finally, the flatness error of the blank's contact with the worktable is 0.002mm, the verticality error of the side wall is 0.003mm, and the overall clamping baseline coincidence reaches 100%. After clamping, the fixture baseline is locked, and the baseline switching function is turned off throughout the process. There is no secondary disassembly or repositioning calibration during the entire machining process, completely avoiding the cumulative positioning error caused by multiple clamping.

[0038] S4, Adaptive Layered Quantization Milling Forming: Calls a preset CNC machining path file, using rough milling,

[0039] A three-stage, progressive, integrated milling process encompassing semi-finish milling and finish milling, with constant-temperature micro-volume cutting fluid spraying at 22°C throughout the entire process.

[0040] Cooling is applied to prevent heat buildup during processing. This is achieved through the material removal rate formula. Precisely match milling parameters at each stage: For rough milling, use a Φ10mm carbide end mill, set the spindle speed n=2000r / min, feed per revolution f=0.4mm / r, and axial depth of cut a. p =1.0mm, radial cutting width a e =1.2mm, the calculated material removal rate MRR is 10200mm³ / min, quickly removing excess substrate from the blank, leaving a uniform finishing allowance of 0.5mm; semi-finish milling uses a Φ8mm carbide milling cutter, setting the spindle speed n=2600r / min, feed per revolution f=0.2mm / r, and axial depth of cut a p =0.4mm, radial cutting width a e =0.8mm, the calculated material removal rate MRR is 4160mm³ / min. The basic contour of the cavity is precisely corrected to eliminate steps and allowance deviations in rough milling. For finish milling, a Φ6mm diamond-coated milling cutter is used, with a spindle speed set to n=3300r / min, feed per revolution f=0.08mm / r, and axial depth of cut a. p =0.15mm, radial cutting width a e =0.5mm, the calculated material removal rate MRR is 924mm³ / min, completing the final cavity size forming. During processing, the temperature data of the processing area is collected in real time and compared with the standard constant temperature of 22℃. The temperature difference is then substituted into the thermal deformation deviation correction formula. By finely adjusting the feed parameters in real time, the overall thermal deformation error of this machining process was precisely controlled within 0.0015mm.

[0041] S5. Gradient Nano-Precision Polishing: After milling, the internal cavity is cleaned of cutting residue and oil. A three-stage gradient nano-polishing process is used to finely polish the entire inner wall of the cavity. The first stage is mechanical rough polishing: 1200-grit wear-resistant waterproof sandpaper is used with a low-speed polishing machine to uniformly grind the cavity's flat surfaces and large curved areas, thoroughly removing macroscopic tool marks, cutting burrs, and uneven steps remaining from milling. The second stage is ultra-fine grinding: 3000-grit diamond ultra-fine grinding paste is used with a flexible silicone grinding head for fine grinding of narrow grooves, rounded corners, and irregular curved surfaces in the cavity, correcting microscopic surface defects. The third stage is mirror-finish polishing: 30nm silica nano-polishing slurry is used with a high-speed, silent polishing head for full-area mirror polishing. For small-curvature irregular curved surfaces with a radius of curvature of 4mm inside the cavity, the polishing speed is actively reduced by 20% to avoid over-polishing, deformation, and distortion of the curved surface. After polishing, a roughness tester was used to check multiple points. The overall surface roughness of the cavity was Ra=0.012μm, which meets the standard for use in precision mirror molds.

[0042] S6. Vacuum-based stress relief: Clean the polished mold blank thoroughly, ensuring it is free of impurities and oil. Place it inside a vacuum heat treatment aging furnace and seal the furnace. Set the furnace vacuum to 0.06 MPa and heat to 210°C at a uniform rate of 10°C / h. Hold at this temperature for 5 hours. Calculate the residual stress using the formula... By combining the stress coefficient of P20 material, the overall milling material removal rate, and the total milling time of 3.2 hours, the heat preservation aging parameters are precisely matched to fully release the residual stress on the surface and in the core generated during the milling and polishing process. After heat preservation, the mold is naturally cooled to room temperature in the furnace. After exiting the furnace, the residual stress elimination rate of the mold reaches 96%, with no stress concentration areas, completely avoiding the risk of deformation and cracking in the later use of the mold.

[0043] S7. Full-Dimensional Precision Verification and Protection: A coordinate measuring machine, laser profilometer, and surface roughness tester are used to perform full-dimensional, multi-point precision inspection of the molded cavity. The inspection items include four core indicators: critical cavity dimensional accuracy, surface contour accuracy, flatness, and inner wall surface roughness. All inspection data meet design tolerance standards, with no dimensional deviations, surface distortion, or unevenness. After passing inspection, the entire cavity undergoes dust removal and degreasing pretreatment. A nano-ceramic protective coating is then uniformly sprayed onto the inner wall of the cavity using an electrostatic spraying process, with the coating thickness strictly controlled at 8μm. After spraying, a low-temperature curing treatment is performed, ensuring a uniform coating without accumulation, missed areas, or bubbles. The cured coating hardness reaches 6H. Finally, the entire precision injection mold cavity is integrally molded.

[0044] Example 2

[0045] S1. Homogenization Pretreatment of the Integral Material: A single H13 hot work die steel billet with dimensions of 350mm × 280mm × 120mm is selected to meet the requirements of high-temperature and high-pressure die casting. First, the outer surface of the billet is ground with a 60-grit industrial grinding wheel to remove the forging oxide layer, surface hard skin, and large burrs. Then, it is soaked in a specialized die degreasing and cleaning agent for 20 minutes, followed by ultrasonic cleaning to deeply remove surface oil, dust, and rust impurities. After cleaning and drying, ultrasonic non-destructive testing equipment is used to perform a full-area scan of the billet's interior, rigorously checking for internal defects such as porosity, cracks, inclusions, and looseness, selecting only fully qualified integral billets. Qualified billets underwent gradient tempering heat treatment with a heating rate of 12℃ / h, reaching 860℃ and holding at that temperature for 2.5h to ensure complete dissolution of carbides and uniform, refined microstructure in the H13 steel. The first stage involved furnace cooling to 450℃ at a constant rate of 15℃ / min, followed by furnace cooling to 290℃ before air cooling to room temperature. After heat treatment, the billet hardness was measured at multiple points, maintaining a uniform HRC32. The overall deformation was only 0.006mm, and the initial residual stress was 75MPa, meeting the high-strength and high-stability processing requirements of the die-casting mold.

[0046] S2. Cavity Quantitative Modeling and Tolerance Prediction: Considering the characteristics of aluminum alloy die-casting products, combined with the average shrinkage rate S=0.8%, nominal product size L0=80mm, product design dimensional tolerance Δ=0.04mm, and the mold processing compensation tolerance δ being taken as 1 / 4 of the product tolerance, i.e., δ=0.01mm, the values ​​are then substituted into the precise cavity forming dimension calculation formula. The baseline machining dimensions of the die-casting mold cavity are accurately calculated. A 3D modeling software is used to construct a complete model of the large, irregularly shaped die-casting cavity, fully replicating all structural features such as complex curved surfaces, deep grooves, bosses, and irregular holes. The model is then imported into a finite element simulation platform to simulate cutting forces, high-temperature deformation, and vibration deviations during high-speed milling of the die-casting mold. Machining paths are optimized and tolerances are compensated for easily deformable areas such as deep cavities, thin walls, and irregular curved surfaces. The overall machining tolerance of the model is strictly controlled within ±0.002mm, generating a dedicated CNC machining path file adapted to the large die-casting cavity.

[0047] S3. Integrated Clamping and Positioning: The pre-processed H13 blank is placed on the worktable of a large CNC machining center and clamped in place using a high-strength hydraulic locking fixture to ensure uniform stress and no local suspension. A combination of laser tool setter and high-precision dial indicator is used for comprehensive calibration of the blank's levelness, perpendicularity, and datum positioning accuracy. The clamping force of the fixture and the blank's placement are fine-tuned, ultimately achieving a blank flatness error ≤0.003mm, a perpendicularity error ≤0.003mm, and datum overlap of 100%. After clamping and calibration, the fixture datum system is locked throughout the entire machining process, ensuring no loosening, disassembly, or repositioning. This completely eliminates the cumulative positioning deviation caused by multiple clampings of large blanks, guaranteeing the overall consistency of large cavity forming.

[0048] S4. Adaptive Layered Quantitative Milling Forming: Imports optimized CNC machining paths, employs a three-level layered integrated milling process, and maintains constant-temperature (20℃) cutting fluid spray cooling throughout the process to meet the heat dissipation requirements of high-speed milling of H13 steel. Based on the material removal rate formula... Precise matching of milling parameters at each stage: For rough milling, a large-diameter carbide end mill is selected, with a spindle speed n = 1800 r / min, feed per revolution f = 0.5 mm / r, and axial depth of cut a. p =0.8mm, radial cutting width a e =1.5mm, control the material removal rate at 11500mm³ / min, quickly remove a large amount of substrate, and leave a uniform finishing allowance; reduce the cutting amount in the semi-finish milling stage, spindle speed n=2500r / min, feed per revolution f=0.25mm / r, and axial cutting depth a p =0.3mm, radial cutting width a e =1.0mm, control the material removal rate at 4800mm³ / min, and correct the basic contour and overall flatness of the cavity; in the finish milling stage, a diamond milling cutter is used, the spindle speed n=3200r / min, the feed per revolution f=0.1mm / r, and the axial depth of cut a p =0.1mm, radial cutting width a e =0.4mm, controlling the material removal rate at 1280mm³ / min to achieve precise dimensional forming of the cavity. During the processing, the processing temperature is monitored in real time, and the cutting feed parameters are dynamically fine-tuned by substituting the temperature difference data into the thermal deformation deviation correction formula, so as to strictly control the overall thermal deformation error of the large cavity within 0.002mm.

[0049] S5. Gradient Nano-Precision Polishing: After completing the overall milling of the cavity, thoroughly clean the internal cutting chips, oil, and residual cutting fluid. Then, employ a gradient nano-polishing process adapted to large, irregularly shaped cavities for refined machining. First stage: Rough polishing. Use 1500-grit abrasion-resistant sandpaper to grind the large-area flat and curved surfaces of the cavity, removing macroscopic tool marks and cutting burrs of varying depths generated by high-speed milling. Second stage: Ultra-fine grinding. Use 2500-grit diamond polishing paste with a large-stroke flexible grinding device to comprehensively grind complex areas such as deep grooves, corners, and irregularly shaped bosses in the cavity, eliminating microscopic defects. Third stage: Mirror-finish polishing. Use a 20-50nm gradient silica polishing slurry for full-area mirror polishing. For the numerous precision irregularly shaped curved surfaces with a curvature radius <5mm in this cavity, uniformly reduce the polishing speed by 20% to avoid surface collapse and contour distortion caused by high-speed polishing. After polishing, multiple sampling inspections were conducted, and the overall surface roughness of the cavity was Ra=0.014μm, which meets the requirements of high wear resistance and high demolding accuracy for die-casting molds.

[0050] S6. Vacuum Quantitative Stress Relief: After cleaning the polished large mold thoroughly to remove all impurities, place it in a vacuum aging furnace. Seal the furnace and evacuate it, maintaining a stable vacuum level of 0.07 MPa. Set the heating rate to 8℃ / h, uniformly raising the temperature to 220℃ and holding it at that temperature for 4.5 hours. Based on the stress coefficient of H13 steel, the overall milling material removal rate, and the total machining time, residual stress is calculated using the formula... Precise matching of heat preservation aging parameters effectively eliminates deep residual stress generated during large cavity milling and polishing. After heat preservation, the mold is naturally cooled to room temperature in the furnace. After exiting the furnace, residual stress is tested throughout the mold, and the stress elimination rate reaches 95.5%. The mold as a whole is free from stress concentration and hidden deformation risks.

[0051] S7. Full-Dimensional Precision Verification and Protection: A three-coordinate measuring machine, laser contour scanner, and high-precision roughness tester are used to perform full-area, multi-point inspection of the large, irregularly shaped cavity. Four core indicators are verified sequentially: critical dimensional accuracy, complex surface contour accuracy, overall flatness, and inner wall surface roughness. All test data meet the design standards and die-casting mold precision requirements, with no dimensional deviations, surface deformations, or surface defects. After passing inspection, the cavity undergoes dust removal, degreasing, and drying pretreatment. A nano-ceramic protective coating is uniformly sprayed using a high-pressure electrostatic spraying process, with the coating thickness strictly controlled at 10μm. After low-temperature curing, the coating is dense, uniform, bubble-free, and does not peel off, with a hardness ≥6H. This significantly improves the high-temperature resistance, wear resistance, and corrosion resistance of the die-casting mold cavity, ultimately completing the integrated molding process of the large, irregularly shaped die-casting mold cavity.

[0052] Comparative Example

[0053] S1. Pre-treatment of Split Blanks: P20 mold steel blanks of the same specification are manually cut and disassembled into multiple split modules, including upper mold, lower mold, inserts, and cores. Each split module is individually ground, derusted, and cleaned, and simple appearance defect inspection is carried out on each piece. Each split module is subjected to conventional overall quenching and tempering heat treatment without gradient temperature control. The heat treatment parameters are uniformly 840℃ for 2.5h and then air-cooled. The hardness of each module varies greatly, ranging from HRC27 to 34. The deformation of each module is not uniform, the initial residual stress ranges from 80 to 120MPa, and the consistency of the base material is poor.

[0054] S2. Split Modeling and Experience-Based Machining: The overall structure of the cavity is manually disassembled, and each split module is modeled separately. There is no quantitative size compensation formula. It relies entirely on the operator's experience to reserve shrinkage allowance and machining tolerance. There is no finite element simulation deformation prediction. It is impossible to correct the machining deviation of irregular curved surfaces in advance. The machining model itself has initial design errors.

[0055] S3. Multiple separate clamping and positioning: Each separate module is clamped and milled separately. Each module undergoes at least two clamping and positioning operations. After processing, the modules are disassembled and replaced. The entire process involves multiple disassembly and assembly operations and multiple reference switching operations, which inevitably generates a large number of cumulative positioning errors. The maximum positioning deviation of a single module can reach 0.015mm.

[0056] S4. Experience-based split milling: There is no quantitative material removal rate matching standard. Operators arbitrarily set milling speed, feed rate and depth of cut based on experience. There is no precise classification of rough and finish milling parameters. There is no constant temperature cooling or real-time thermal deformation correction during the machining process. The cutting temperature fluctuates greatly, the thermal deformation of each module is uneven, and the dimensional deviation of individual modules is large.

[0057] S5. Separate manual grinding and polishing: After each module is processed, it is manually ground and polished separately. There is no gradient polishing process. The grit of sandpaper and polishing paste can be matched at will. Irregular curved surfaces rely entirely on manual feel for grinding, which can easily lead to problems such as over-polishing, under-polishing, and surface distortion. The surface quality of each module is inconsistent.

[0058] S6. Simple overall aging treatment: After all modules are assembled, only conventional low-temperature simple aging treatment is performed. There is no quantitative stress calculation and precise insulation parameter matching. The residual stress elimination rate is only about 60%, and a large amount of processing stress remains inside the mold.

[0059] S7. Assembly, Mold Construction, and Inspection Protection: All separate modules are manually assembled into a single cavity using bolts and locating pins. Obvious assembly gaps exist after assembly, with gap widths ranging from 0.02 to 0.05 mm. The cumulative dimensional error is 0.01 to 0.03 mm, and there are obvious steps and misalignments at the cavity joints. After secondary manual grinding and mold repair, the surface roughness of the cavity is Ra ≥ 0.8 μm, with poor surface consistency. Finally, a simple spray of ordinary anti-rust oil is applied for protection, without a high-strength nano-ceramic protective coating.

[0060] It should be noted that in this paper, relational terms such as first and second are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations.

Claims

1. A mold cavity integrated forming machining process, characterized in that, Including the following: S1. Homogenization pretreatment of whole material: Select a whole blank of integrated mold, grind and remove impurities, degrease and remove rust, and conduct non-destructive testing on the blank to remove defective blanks containing air holes, cracks and slag inclusions. Qualified billets are subjected to gradient tempering heat treatment to obtain an integrated substrate with uniform hardness and consistent initial internal stress. S2. Cavity Quantitative Modeling and Tolerance Prediction: Construct a three-dimensional model of the cavity based on the product molding standard. Combine the plastic shrinkage rate and processing deformation error, complete the model size pre-compensation through the cavity precise molding size calculation formula. At the same time, predict the processing deformation range based on finite element simulation and generate a CNC machining path with quantitative tolerance threshold. S3. Integrated clamping and positioning with reference: The process adopts a one-time clamping reference locking process. The whole blank is positioned and calibrated by a high-precision reference tooling, which limits the clamping flatness and perpendicularity deviation. There is no secondary disassembly or reference switching throughout the process, eliminating the cumulative error of multiple positioning. S4. Adaptive Layered Quantitative Milling Forming: Based on the preset material removal rate calculation formula, the cutting parameters of roughing, semi-finishing, and finishing milling are matched. Layered progressive integrated milling is adopted. Combined with real-time temperature monitoring data, the cutting feed is dynamically fine-tuned through the thermal deformation deviation correction formula to achieve seamless integral forming of the cavity. S5. Gradient nano-precision polishing: The inner wall of the milled cavity is polished using a multi-level gradient polishing process. Different mesh sizes of grinding media and polishing parameters are matched according to the curvature of the cavity surface to remove micro-tool marks and reduce surface roughness step by step, ensuring the uniformity of the cavity surface. S6. Vacuum Quantitative Stress Relief: Based on the billet material and machining allowance, match the corresponding low-temperature aging process parameters to accurately eliminate residual internal stress generated during milling and polishing in a vacuum environment, and suppress the later deformation of the cavity. S7. Full-dimensional precision verification and protection: Quantitative testing is performed on the dimensional accuracy, curvature, surface roughness, and deformation of the molding cavity. After all indicators meet the standards, a nano-protective coating is applied to complete the integrated molding process of the mold cavity.

2. The process of claim 1, wherein, In step S2, the formula for calculating the precise forming dimensions of the cavity is: Wherein, is the final design processing size of the mold cavity, unit: mm; is the nominal size of the product, unit: mm; is the average shrinkage rate of the plastic material; is the product size tolerance, unit: mm; is the mold processing compensation tolerance, which is 1 / 4-1 / 6 of the product size tolerance.

3. The mold cavity integrated molding process according to claim 1, characterized in that, In step S4, the formula for calculating the material removal rate is: in, Material removal rate, in mm³ / min; This refers to the milling spindle speed, in r / min. Feed per revolution, in mm / r; The depth of cut is axial, in mm. Radial cutting width, in mm; rough milling control based on graded matching parameters according to formula. Semi-finish milling control: 8000–12000 mm³ / min 3000~5000mm³ / min, precision milling control The flow rate is 500–1500 mm³ / min.

4. The mold cavity integrated molding process according to claim 1, characterized in that, In step S4, the formula for correcting thermal deformation deviation is: in, This is the real-time thermal deformation correction amount, in mm; The coefficient of thermal expansion of the billet material; The temperature difference between the real-time processing temperature and the standard constant temperature of 22℃ is expressed in °C. These are the reference dimensions for cavity machining, in mm; The deformation correction coefficient is set to 0.0001 to 0.0003. During the machining process, the cutting parameters are finely adjusted in real time based on the calculated correction amount to control the thermal deformation error to ≤0.002mm.

5. The mold cavity integrated molding process according to claim 1, characterized in that, In S1, the gradient tempering heat treatment parameters are as follows: heating to 830-870℃ and holding at that temperature for 2-4 hours; cooling in the furnace to 450℃ in the first stage at a cooling rate of 15℃ / min; cooling in the furnace to below 300℃ in the second stage and then air cooling after removal from the furnace; after heat treatment, the hardness of the billet is uniformly maintained at HRC29-33, the overall initial deformation of the billet is ≤0.008mm, and the internal residual stress is ≤80MPa.

6. The mold cavity integrated molding process according to claim 1, characterized in that, In S3, the integrated clamping and positioning standard is as follows: calibration is performed using a dial indicator in conjunction with a laser tool setter, the flatness error of the worktable is ≤0.003mm, the perpendicularity error is ≤0.004mm, the clamping reference overlap is 100%, the reference is locked throughout the entire process without deviation, and the cumulative positioning error of traditional multiple clamping is completely eliminated.

7. The mold cavity integrated molding process according to claim 1, characterized in that, In step S5, the specific process of gradient nano-precision polishing is as follows: First, mechanical rough polishing is performed using 1000-1500 grit abrasion-resistant sandpaper to remove macroscopic milling marks; second, ultra-fine polishing is performed using 2500-3500 grit diamond polishing paste to correct microscopic uneven surfaces; third, mirror-finish polishing is performed using silica polishing slurry with a particle size of 20-50 nm, resulting in a surface roughness Ra≤0.015μm for the cavity after polishing; for irregular curved surfaces with a radius of curvature <5mm, the polishing speed is reduced by 20% to avoid over-polishing deformation of the curved surface.

8. The mold cavity integrated molding process according to claim 1, characterized in that, In step S6, the vacuum quantization stress relief parameters are: vacuum degree ≤ 0.07 MPa, temperature rise to 190℃. Maintain a constant temperature of 230℃ for 4–7 hours, with a heating rate of 8–12℃ / h, and allow to cool naturally to room temperature; adjust according to processing residue requirements. Force formula Matching the heat preservation time, among which The material stress coefficient, For milling machining Duration, ensuring residual stress relief rate ≥95%.

9. The mold cavity integrated molding process according to claim 1, characterized in that, In S7, the full-dimensional accuracy verification includes four core indicators: dimensional accuracy, surface profile, flatness, and surface roughness. It is jointly tested using a coordinate measuring machine and a laser profiler. After passing the test, a nano-ceramic protective coating with a thickness of 6-12 μm is sprayed on, with a coating hardness ≥6H, which greatly improves the wear resistance and corrosion resistance of the cavity.

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