Gear injection molding control method

Abstract

The embodiment of the application provides a gear injection molding regulation method, obtains a test parameter table of target gear injection molding; performs simulation test according to the test parameter table to obtain a simulation result; determines global optimal process parameters according to the simulation result; performs injection test under the obtained global optimal process parameters to obtain a gear sample through injection molding; determines gear molding shrinkage according to gear sample measurement data; determines gear mold inverse cavity size parameters according to the gear molding shrinkage; determines gear cavity size according to the gear mold inverse cavity size parameters, and performs precision machining according to the gear cavity size to obtain a target gear injection mold; and performs target gear injection molding according to the target gear injection mold to obtain a target gear finished product. The small modulus gear injection molding precision is improved, which is beneficial to large-scale production and manufacturing of high-precision small modulus gears.

Description

Technical Field

[0001] This invention relates to the fields of advanced machinery manufacturing and material forming, and in particular to a method for controlling gear injection molding. Background Technology

[0002] The primary manufacturing method for small module gears is injection molding. During injection molding, small module plastic gears undergo three steps: heating and melting the engineering plastic, forming the liquid plastic flow, and cooling and solidifying within the mold cavity. During this process, due to the physical properties of plastic's thermal expansion and contraction, the plastic gear undergoes significant shrinkage after being removed from the mold. This results in discrepancies between the actual gear dimensions and tooth profile shape and the design. Furthermore, during involute tooth casting, variations in local mold temperature and the flow direction and speed of the casting liquid during pouring lead to different local shrinkage amounts, causing nonlinear shrinkage problems.

[0003] Meanwhile, single process optimization has limited effect on shrinkage control; therefore, cavity inversion design is required, which involves reverse-expanding the gear cavity to compensate for shrinkage. Traditional inversion methods mainly include the following two: Huang Tianshi obtains the cavity tooth profile curve by positively displacing the tooth profile curve; Li Jianxin performs module and pressure angle corrections on the cavity tooth profile, with the module correction being... The correction for the pressure angle is as follows: Although the above two inversion design methods can improve the tooth profile accuracy of small module plastic gears to a certain extent, considering that the polymer shrinkage rate is affected by a variety of factors such as material properties, production environment, process parameters and mold structure, the material shrinkage rate alone cannot truly reflect the degree of gear shrinkage. It is necessary to combine the gear shrinkage characteristics and the actual molding shrinkage rate to perform parametric inversion design of the mold cavity. Summary of the Invention

[0004] This invention provides a gear injection molding control method to address the problem that existing inversion cavity design methods do not consider the significant deviation between material shrinkage and actual molding shrinkage. By detecting the shrinkage rate of key dimensions in the actual molding of small module gears, the inversion cavity of small module gears can be parametrically designed. This reduces the number of trial moldings, avoiding wasted time and costs. Simultaneously, it simplifies and improves the accuracy of small module gear inversion design, avoiding inaccuracies and significantly enhancing the injection molding precision of small module gears. This is beneficial for the large-scale production of high-precision small module gears.

[0005] In a first aspect, embodiments of the present invention provide a gear injection molding control method, the method comprising:

[0006] Obtain the test parameter table for the injection molding of the target gear;

[0007] A simulation experiment was conducted according to the aforementioned experimental parameter table, and the simulation results were obtained.

[0008] Based on the simulation results, determine the globally optimal process parameters;

[0009] An injection molding experiment was conducted under the obtained globally optimal process parameters, and a gear sample was obtained by injection molding.

[0010] The gear forming shrinkage rate was determined based on the measurement data of the gear sample.

[0011] Based on the gear forming shrinkage rate, determine the inverted cavity size parameters of the gear mold;

[0012] Based on the inverted cavity size parameters of the gear mold, the gear cavity size is determined, and precision machining is performed according to the gear cavity size to obtain the target gear injection mold;

[0013] The target gear is injection molded according to the target gear injection mold to obtain the finished target gear.

[0014] Optionally, obtaining the test parameter table for injection molding of the target gear includes:

[0015] Obtain the test input parameters for the target gear;

[0016] The range of process parameters is determined based on the material properties of the target gear;

[0017] Based on the test input parameters and the range of process parameters, a test parameter table for the injection molding of the target gear is determined.

[0018] Optionally, the step of conducting simulation experiments based on the experimental parameter table to obtain simulation results includes:

[0019] Based on the actual forming conditions, a simulation model of the target gear is established;

[0020] After selecting the analysis type and analysis sequence, conduct a simulation experiment according to the experimental parameter table to obtain the simulation results.

[0021] Optionally, determining the globally optimal process parameters based on the simulation results includes:

[0022] Based on the simulation results, the maximum shrinkage and volume shrinkage rate are determined;

[0023] Based on the simulation results, the addendum circle diameter and dedendum circle diameter of the target gear simulation model are determined.

[0024] The shrinkage rate of the tip circle diameter and the shrinkage rate of the root circle diameter are determined based on the tip circle diameter and the root circle diameter.

[0025] Using the maximum shrinkage, the volume shrinkage rate, the tip circle diameter shrinkage rate, and the root circle diameter shrinkage rate as response targets, and taking the minimum of the response targets as the optimization target, the globally optimal process parameters are determined.

[0026] Optionally, determining the globally optimal process parameters with the minimum response target as the optimization objective includes:

[0027] Determine the response surface model between the process parameters and the target response;

[0028] The response surface model is optimized with the goal of minimizing the response target to obtain the globally optimal process parameters.

[0029] Optionally, the step of performing injection molding tests under the obtained globally optimal process parameters to obtain gear samples includes:

[0030] Determine the initial gear cavity according to the target gear dimensions;

[0031] Based on the initial gear cavity, the initial mold cavity is precision machined to obtain the initial injection mold;

[0032] Gear samples are obtained by injection molding using the initial injection mold.

[0033] Optionally, determining the gear forming shrinkage rate based on the gear sample measurement data includes:

[0034] After the gear sample has stabilized, the dimensions of the gear sample are determined.

[0035] The gear forming shrinkage rate is determined based on the dimensions of the gear sample.

[0036] Optionally, determining the gear forming shrinkage rate based on the dimensions of the gear sample includes:

[0037] Calculate the average root circle diameter of multiple gear samples;

[0038] The gear forming shrinkage rate is calculated based on the average root circle diameter.

[0039] Optionally, determining the gear mold cavity size parameters based on the gear forming shrinkage rate includes:

[0040] Based on the module of the target gear and the gear forming shrinkage rate, the inverse cavity size parameters of the gear mold are determined.

[0041] Optionally, the step of precision machining according to the gear cavity dimensions to obtain the target gear injection mold includes:

[0042] Keeping the overall mold structure, cooling system, temperature control system and casting system unchanged, the mold cavity is precisely machined according to the gear cavity size to obtain the target gear injection mold.

[0043] In this embodiment of the invention, an experimental parameter table for injection molding of the target gear is obtained; a simulation experiment is conducted according to the experimental parameter table to obtain simulation results; the globally optimal process parameters are determined based on the simulation results; an injection molding experiment is conducted under the obtained globally optimal process parameters to obtain a gear sample; the gear molding shrinkage rate is determined based on the measurement data of the gear sample; the gear mold inversion cavity size parameters are determined based on the gear molding shrinkage rate; the gear cavity size is determined based on the gear mold inversion cavity size parameters, and precision machining is performed based on the gear cavity size to obtain the target gear injection mold; the target gear is injection molded based on the target gear injection mold to obtain the target gear finished product. By detecting the shrinkage rate of key dimensions in the actual molding of small module gears, the inversion cavity of small module gears can be parametrically designed, which can reduce the number of trial moldings, avoid the waste of time and cost, and make the inversion design of small module gears simpler and more accurate. It can avoid the problem of inaccurate inversion design of small module gears, greatly improve the injection molding accuracy of small module gears, and is conducive to the large-scale production and manufacturing of high-precision small module gears. Attached Figure Description

[0044] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the 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.

[0045] Figure 1 This is a flowchart of a gear injection molding control method provided in an embodiment of the present invention. Detailed Implementation

[0046] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0047] Please see Figure 1 , Figure 1 This is a flowchart of a gear injection molding control method provided in an embodiment of the present invention, such as... Figure 1As shown, the gear injection molding control method includes the following steps:

[0048] 101. Obtain the test parameter table for injection molding of the target gear.

[0049] In this embodiment of the invention, the target gear can be a plastic small module gear, which is the most commonly used transmission component in microelectromechanical systems. It has significant advantages such as small weight, low cost, self-lubrication, transmission noise reduction, and strong ability to absorb shock and vibration. It is widely used in cutting-edge fields such as aerospace, 5G communication, and medical devices.

[0050] Optionally, obtaining the test parameter table for injection molding of the target gear includes: obtaining the test input parameters of the target gear; determining the range of process parameters based on the material properties of the target gear; and determining the test parameter table for injection molding of the target gear based on the test input parameters and the range of process parameters.

[0051] In this embodiment of the invention, the above-mentioned experimental input parameters can be mold temperature, melt temperature, holding pressure, holding time, injection speed, and cooling time. Mold temperature is the main influencing factor during injection molding. If the mold temperature is too low, the strength of the part will decrease, the surface quality will be poor, the internal stress will increase, demolding will be difficult, and even the part may be incompletely filled (not fully filled). If the mold temperature is too high, the part is prone to deformation and the production cycle will be prolonged. Melt temperature directly affects the properties of the melt. Holding pressure refers to the pressure applied to the front melt after injection, without the screw immediately retracting. Holding pressure ≤ injection pressure. Holding time refers to the time that the material is held under a certain pressure after filling the cavity during injection molding. Injection speed refers to the speed at which the filling speed is divided into segments (beginning, middle, and end) and a smooth transition is achieved from one set point to another. This ensures a stable melt surface speed to produce the desired molecular separation and minimum internal stress. Cooling time refers to the cooling time of the injection molding process. A long cooling time will affect production costs, while a short cooling time will easily lead to deformation and affect the yield.

[0052] The aforementioned target gear material properties refer to its density, processing temperature, average specific heat, mold temperature, and shrinkage rate.

[0053] Specifically, based on the material properties, a suitable range of process parameters is selected, and Box-Behnken experimental design is performed using ISIGHT software to obtain the corresponding experimental parameter table. ISIGHT was first proposed and led by Dr. Siu S. Tong of MIT around the 1980s, and after years of development, it has become a leader among similar software. ISIGHT itself does not perform calculations, but it calls other software (such as ABAQUS, ANSYS, etc.) to perform calculations through appropriate methods. Therefore, ISIGHT is primarily a "software robot" that can continuously call relevant engineering calculation software to perform calculations without human intervention. Box-Behnken experimental design is a type of response surface design that does not include embedded factors or partial factor designs. Box-Behnken designs have treatment combinations located at the center point of the experimental space edge and require at least three factors.

[0054] In this embodiment of the invention, the above-mentioned test parameter table may refer to mold temperature parameters, melt temperature parameters, holding pressure parameters, holding time parameters, injection speed parameters, and cooling time parameters.

[0055] 102. Conduct simulation experiments according to the experimental parameter table and obtain simulation results.

[0056] In this embodiment of the invention, the above simulation experiment is to simulate the effect of reality using Moldflow simulation software on a computer. Moldflow simulation software connects theoretical conditions and experimental processes through a graphical interface, and at the same time uses certain programming to achieve the effect of simulating reality.

[0057] Optionally, the simulation test is conducted according to the above-mentioned test parameter table to obtain the simulation results, including: establishing the above-mentioned target gear simulation model according to the actual molding situation; after selecting the analysis type and analysis sequence, the simulation test is conducted according to the above-mentioned test parameter table to obtain the simulation results.

[0058] In this embodiment of the invention, the above-mentioned model, based on the actual molding conditions, includes a gear cavity, a gating system, and a cooling system. A simulation model of a small-module gear is established. The analysis type is thermoplastic composite material injection molding, and the analysis sequence is cooling + filling + holding pressure + warpage. Simulation experiments are conducted according to the experimental parameter table to obtain simulation results. The gear cavity is a non-standard internal gear. The outer circle and thickness of the gear cavity blank have been precision machined and can be directly used as the installation and measurement reference for the cavity. The gating system typically consists of four parts: the sprue, the runner (main runner and branch runner), the sprue-to-cold slug well, and refers to the channel system that guides the plastic melt from the injection molding machine nozzle to the cavity. The cooling system is mainly used to cool the oil temperature. Excessive oil temperature can cause various malfunctions, so the oil temperature must be controlled.

[0059] In this embodiment of the invention, the aforementioned thermoplastic composite material is a general term for various thermoplastic resins reinforced with glass fiber, carbon fiber, aramid fiber, etc., and is known internationally as FRTP (Fiber Rinforced Thermo Plastics). Due to the different types of thermoplastic resins and reinforcing materials, the production processes and properties of the resulting composite materials vary greatly. The density of thermoplastic composite materials is 1.1–1.6 g / cm³, only 1 / 5 to 1 / 7 that of steel, and 1 / 3 to 1 / 4 lighter than thermosetting fiberglass. It can achieve higher mechanical strength with a smaller unit mass. The physical, chemical, and mechanical properties of thermoplastic composite materials are designed through the rational selection of raw material types, proportions, processing methods, fiber content, and layup methods.

[0060] Specifically, thermoplastic composite injection molding process has a short molding cycle, minimal energy consumption, high product precision, and can mold complex switches and products with inserts in one go. Several products can be produced in one mold, resulting in high production efficiency.

[0061] In this embodiment of the invention, the aforementioned cooling + filling + holding pressure + warpage refers to the gear injection molding process. Cooling accounts for approximately 70% to 80% of the total time in injection molding. Therefore, cooling time directly affects the molding cycle length and production volume of plastic products. During the demolding stage, the temperature of the plastic product should be cooled below its heat distortion temperature to prevent relaxation due to residual stress or warpage and deformation caused by demolding forces. Filling is the first step in the injection molding cycle, starting from the moment the mold closes and begins injection, until the mold cavity is filled to approximately 95%. Holding pressure is the most important stage affecting the final product performance during injection molding. Because the polymer melt expands when heated and contracts upon cooling, it inevitably leads to uneven distribution of internal density and yield within the product. Therefore, a suitable holding pressure must be selected. The holding pressure stage is a complex, non-isothermal, compressible stage. Warpage occurs when a plastic part does not conform to its designed shape and instead undergoes surface distortion. Warpage is caused by uneven shrinkage of the molded part. If the entire plastic part has a uniform shrinkage rate, the part will not warp but will only shrink in size. However, due to the interaction of many factors such as molecular chain / fiber alignment, mold cooling, part design, mold design, and molding conditions, achieving low shrinkage or uniform shrinkage is a very complex task.

[0062] 103. Based on the simulation results, determine the globally optimal process parameters.

[0063] In this embodiment of the invention, the above-mentioned globally optimal process parameters may be the optimal mold temperature, the optimal melt temperature, the optimal holding pressure, the optimal holding time, the optimal injection speed, and the optimal cooling time.

[0064] Optionally, determining the globally optimal process parameters based on the simulation results includes: determining the maximum shrinkage and volumetric shrinkage rate based on the simulation results; determining the addendum circle diameter and dedendum circle diameter of the target gear simulation model based on the simulation results; determining the addendum circle diameter shrinkage rate and dedendum circle diameter shrinkage rate based on the addendum circle diameter and dedendum circle diameter; and determining the globally optimal process parameters by using the maximum shrinkage, volumetric shrinkage rate, addendum circle diameter shrinkage rate, and dedendum circle diameter shrinkage rate as response targets and minimizing the response targets as the optimization objective.

[0065] In this embodiment of the invention, the maximum shrinkage refers to the physical property of plastic thermal expansion and contraction. Plastic gears undergo significant shrinkage after being removed from the mold. The volumetric shrinkage rate refers to the percentage increase in local density from the end of the holding pressure stage until the part cools to the ambient reference temperature (default value 25°C / 77°F). Local shrinkage, critical dimension shrinkage, and overall shrinkage of the gear directly affect the molding accuracy of small module gears. Therefore, the maximum shrinkage (…) is selected… ), tooth tip circle diameter shrinkage rate ( ), tooth root circle diameter shrinkage rate ( ) and volume shrinkage rate ( As the response target (Y), the maximum contraction amount and volume shrinkage rate It can be obtained directly from the simulation results.

[0066] Then, the gear shrinkage model was exported from the simulation results at a 1:1 scale, and the addendum circle diameter of the gear shrinkage model was measured using CAD 3D modeling software. and root circle diameter Then the tooth tip circle diameter shrinkage rate tooth root circle diameter shrinkage rate .

[0067] Import the test results into the Isight software, and establish a second-order response surface model between the process parameters and the response target through the Approximation Models module. By adjusting the structure of the model, the accuracy of the model can be ensured to reach more than 90%.

[0068] The aforementioned ISIGHT was first proposed and led by MIT PhD Siu S. Tong around the 1980s, and after years of development, it has become a leader among similar software programs. ISIGHT itself does not perform calculations, but it calls other software (such as ABAQUS and ANSYS) to perform calculations through appropriate methods. Therefore, ISIGHT is primarily a "software robot" that can continuously call relevant engineering calculation software to perform calculations without human intervention. The aforementioned Approximation Models module represents the approximation model; to reduce the complexity of the problem and the amount of computation, certain approximate modeling methods are required.

[0069] Optionally, the above-mentioned determination of the globally optimal process parameters with the minimum of the above-mentioned response target as the optimization objective includes: determining the response surface model between the process parameters and the above-mentioned response target; optimizing the above-mentioned response surface model with the minimum of the above-mentioned response target as the optimization objective to obtain the globally optimal process parameters.

[0070] In this embodiment of the invention, the local shrinkage, critical dimension shrinkage, and overall shrinkage of the gear all directly affect the forming accuracy of the small module gear. Therefore, the maximum shrinkage amount is selected ( ), tooth tip circle diameter shrinkage rate ( ), tooth root circle diameter shrinkage rate ( ) and volume shrinkage rate ( As the response target (Y), the maximum contraction amount and volume shrinkage rate It can be obtained directly from the simulation results.

[0071] Then, the gear shrinkage model was exported from the simulation results at a 1:1 scale, and the addendum circle diameter of the gear shrinkage model was measured using CAD 3D modeling software. and root circle diameter Then the tooth tip circle diameter shrinkage rate tooth root circle diameter shrinkage rate .

[0072] Import the test results into the Isight software, and establish a second-order response surface model between the process parameters and the response target through the Approximation Models module. By adjusting the structure of the model, the accuracy of the model can be ensured to reach more than 90%.

[0073] The established second-order response surface model was optimized using the Multi-Objective Optimization module. Multi-Objective Optimization, or multi-objective optimization, obtains the optimal solution of the objective function through a specific optimization algorithm. The chosen algorithm is NSGA-II, proposed by Srinivas and Deb in 2000 based on NSGA. NSGA-II is superior to NSGA in several ways: it employs a fast non-dominated sorting algorithm, significantly reducing computational complexity compared to NSGA; it uses crowding degree and crowding degree comparison operators instead of the required shared radius `shareQ`, which is used as the winning criterion in peer comparisons after fast sorting, allowing individuals in the quasi-Pareto domain to expand to the entire Pareto domain and be evenly distributed, maintaining population diversity; and it introduces an elitist strategy, expanding the sampling space, preventing the loss of the best individuals, and improving the algorithm's computational speed and robustness. In the algorithm settings, the Population side is set to 12, the Number of Generations is set to 20, and the sample size is 240, meeting the recommended range of 20-200. Setting the Crossover Rate to 0.9 (within the recommended range of 0.6 to 1) and keeping the rest at their default settings will yield the globally optimal process parameters that minimize the optimization index Y.

[0074] 104. Under the obtained globally optimal process parameters, an injection molding test was conducted to obtain a gear sample.

[0075] In this embodiment of the invention, a precision injection molding machine is selected to conduct a small-module gear injection molding test under the obtained globally optimal process parameters to obtain an injection-molded gear sample.

[0076] Optionally, the above-mentioned injection molding test under the obtained global optimal process parameters, and the injection molding to obtain a gear sample, includes: determining the initial gear cavity according to the target gear size; performing precision machining on the initial mold cavity according to the initial gear cavity to obtain the initial injection mold; and injection molding the gear sample through the initial injection mold.

[0077] In this embodiment of the invention, the initial gear cavity is designed according to the target gear dimensions. The mold cavity is precisely machined using a slow wire EDM process, and finally, a super depth-of-field microscope is used to check if the gear mold dimensions are within the error range. Because polymer particles absorb water vapor from the air, to avoid excessive changes in polymer particle density and resulting in large fluctuations in material shrinkage, the polymer particles are weighed after removal. Before molding, the polymer material needs to be thoroughly dried until the weight data stabilizes. Then, a precision injection molding machine is used to mold the target gear to obtain an injection-molded gear sample.

[0078] In this embodiment of the invention, the aforementioned slow wire EDM is a type of electrical discharge wire EDM. It utilizes a continuously moving fine metal wire (called the electrode wire) as an electrode to perform pulsed spark discharge on the workpiece to remove metal and cut it into shape. The wire feed speed is generally below 0.2 mm / s, with an accuracy of 0.001 mm, and the surface quality is close to that of grinding. The aforementioned ultra-depth-of-field microscope is a binocular continuous zoom stereomicroscope that can magnify tiny objects to form clear, upright stereoscopic images. The ultra-depth-of-field microscope has a long working distance, a wide range of sharpness, complete accessories, and is easy to operate. When observing objects, it produces upright three-dimensional spatial images with strong stereoscopic effect, clear and wide imaging.

[0079] 105. Determine the gear forming shrinkage rate based on the measurement data of the gear sample.

[0080] In this embodiment of the invention, the aforementioned measurement data refers to the key dimensions of the gear sample, including the root circle diameter and the addendum circle diameter. The dimensional shrinkage rate of the gear is calculated by measuring these key dimensions. Since the root circle diameter has the largest shrinkage rate, we select it as the optimal measurement. As the basis for measuring shrinkage rate, the gear sample was measured using a super depth-of-field microscope. First, the gear teeth were magnified under high magnification to check for defects. If defects were found, the sample was unusable. If the tooth surface was intact, the high magnification was replaced with low magnification, allowing the entire gear to be displayed on the screen. Then, the three-point circle determination method was used to determine the tooth root circle and addendum circle profiles, and the coincidence of the centers of the addendum and root circles was checked. Coincidence indicates that the teeth of the gear sample shrank synchronously. Finally, the diameter of the tooth root circle was measured using the planar measurement function of the super depth-of-field microscope measurement system.

[0081] In this embodiment of the invention, the final gear mold cavity needs to be appropriately enlarged. The gear cavity is designed according to the target gear size, and the mold cavity is precision machined using a slow wire EDM process. Finally, an ultra-depth-of-field microscope is used to check whether the gear mold size is within the error range.

[0082] Optionally, determining the gear forming shrinkage rate based on the gear sample measurement data includes: determining the dimensions of the gear sample after the gear sample has stabilized; and determining the gear forming shrinkage rate based on the dimensions of the gear sample.

[0083] In this embodiment of the invention, since polymer particles absorb water vapor from the air, to avoid excessive changes in the density of the polymer particles and resulting in excessive material shrinkage fluctuations, the polymer particles are weighed after removal. Before molding, the polymer material needs to be thoroughly dried until the weight data remains stable. Then, experiments are conducted under the obtained globally optimal process parameters. The injection-molded gear sample is placed in a ventilated area for cooling for 48 hours. After the dimensions stabilize, the gear sample is dimensionally measured. The dimensional shrinkage rate of the gear is calculated by measuring the key dimensions. The gear sample is measured using a super depth-of-field microscope. First, the gear teeth are magnified under high magnification to check for defects. If defects are found, the sample is unusable. If the tooth surface is intact, the high magnification is replaced with a low magnification to show the entire gear on the screen. Then, the tooth root circle and tooth tip circle profiles are determined using the three-point circle method, and the centers of the tooth tip circle and tooth root circle are checked for coincidence. Coincidence indicates that the teeth of the gear sample shrink synchronously. Finally, the diameter of the tooth root circle was measured using the planar measurement function of the ultra-depth-of-field microscope measurement system.

[0084] Optionally, determining the gear forming shrinkage rate based on the dimensions of the gear samples includes: calculating the average root circle diameter of multiple gear samples; and calculating the gear forming shrinkage rate based on the average root circle diameter.

[0085] In this embodiment of the invention, the aforementioned plurality of gear samples can be 10 or more gear samples. The diameter of the tooth root circle is measured using the planar measurement function of a super depth-of-field microscope measurement system. To ensure calculation accuracy, the tooth root circle diameter is retained to two decimal places. Finally, the tooth root circle diameters of 10 gear samples are measured, and the average value is calculated. Based on the obtained average root circle diameter Calculate the gear forming shrinkage rate Furthermore, the shrinkage rate value is retained to two decimal places.

[0086] The gear forming shrinkage rate is shown in the following formula:

[0087]

[0088] 106. Determine the inverse cavity size parameters of the gear mold based on the gear forming shrinkage rate.

[0089] In this embodiment of the invention, the inverse cavity dimensions of the gear mold are calculated based on the aforementioned gear forming shrinkage rate. The results are shown in the table below:

[0090]

[0091] Optionally, determining the gear mold inversion cavity size parameters based on the gear forming shrinkage rate includes: determining the gear mold inversion cavity size parameters based on the module of the target gear and the gear forming shrinkage rate.

[0092] In this embodiment of the invention, the target gear module is m; the inverted gear module is... .

[0093] The module of the inverted gear can also be negative; the number of teeth is z, and the target gear and the inverted gear have the same number of teeth; the pressure angle is... The pressure angles of the target gear and the inverted gear are the same; the tooth width is b, and the tooth widths of the target gear and the inverted gear are the same.

[0094] 107. Based on the inverse cavity size parameters of the gear mold, determine the gear cavity size, and perform precision machining according to the gear cavity size to obtain the target gear injection mold.

[0095] In this embodiment of the invention, the gear cavity size parameters are designed according to the inversion parameters, the gear cavity size is determined, and precision machining is performed to obtain the target gear injection mold.

[0096] Optionally, the above-mentioned precision machining based on the gear cavity dimensions to obtain the target gear injection mold includes: keeping the overall mold structure, cooling system, temperature control system and casting system unchanged, and precision machining the mold cavity based on the gear cavity dimensions to obtain the target gear injection mold.

[0097] In this embodiment of the invention, precision machining is performed according to the inverted gear cavity dimensions. Except for the change in cavity dimensions, the overall mold structure, cooling system, temperature control system, and gating system remain unchanged, thus obtaining the target gear injection mold.

[0098] 108. Based on the injection mold of the target gear, the target gear is injection molded to obtain the finished target gear.

[0099] In this embodiment of the invention, a small-module gear injection molding test is conducted using a precision injection molding machine under globally optimal process conditions to obtain injection-molded gear samples. The gear molding shrinkage rate is obtained from the gear samples, and the gear mold cavity size parameters are determined based on the gear molding shrinkage rate to obtain the gear cavity size. Precision machining is then performed based on the gear cavity size to obtain the target gear injection mold. Finally, injection molding is performed under globally optimal molding process parameters based on the target gear injection mold to obtain the target gear finished product, i.e., a high-precision small-module gear.

[0100] In this embodiment of the invention, by detecting the shrinkage rate of key dimensions in the actual molding of small module gears, the inversion cavity of small module gears can be parametrically designed. This reduces the number of trial moldings, avoids wasting time and costs, and makes the inversion design of small module gears simpler and more accurate. It avoids the problem of inaccurate inversion design of small module gears, greatly improves the injection molding accuracy of small module gears, and is beneficial to the large-scale production and manufacturing of high-precision small module gears.

[0101] The above description discloses only preferred embodiments of the present invention and should not be construed as limiting the scope of the present invention. Therefore, equivalent variations made in accordance with the claims of the present invention are still within the scope of the present invention.

Claims

1. A method of injection molding control of a gear, characterized by, The method comprises the following steps: obtaining a test parameter table for injection molding of a target gear; performing a simulation test according to the test parameter table to obtain a simulation result; determining a global optimal process parameter according to the simulation result, including determining a maximum shrinkage and a volume shrinkage rate according to the simulation result; determining a dedendum diameter and a addendum diameter of the target gear simulation model through the simulation result; determining a addendum diameter shrinkage rate and a dedendum diameter shrinkage rate according to the addendum diameter and the dedendum diameter; the local shrinkage, the critical dimension shrinkage and the overall shrinkage of the gear directly affect the molding precision of the small modulus gear, the maximum shrinkage, the volume shrinkage rate, the addendum diameter shrinkage rate and the dedendum diameter shrinkage rate are taken as response targets, and a global optimal process parameter is determined by taking the minimum of the response targets as an optimization target; the maximum shrinkage and the volume shrinkage rate can be obtained through the simulation result, and the addendum diameter shrinkage rate and the dedendum diameter shrinkage rate can be respectively expressed as: ； ； wherein is the addendum diameter contraction rate, is the addendum diameter after contraction, is the addendum diameter before contraction, is the dedendum diameter contraction rate, is the dedendum diameter after contraction, is the dedendum diameter before contraction; The global optimal process parameter is determined by taking the minimum of the response targets as the optimization target, including determining a response surface model between the process parameter and the response target; the response surface model is optimized by taking the minimum of the response targets as the optimization target to obtain the global optimal process parameter; performing an injection molding test under the obtained global optimal process parameter to obtain a gear sample by injection molding, including determining an initial gear cavity according to the size of the target gear; precisely machining an initial injection mold cavity according to the initial gear cavity; weighing the polymer particle material after taking it out, and drying the polymer material sufficiently until the weight data of the polymer material remains stable before molding; and obtaining a gear sample by injection molding through the initial injection mold; determining a gear molding shrinkage rate according to the gear sample measurement data; determining a gear mold inverse cavity size parameter according to the gear molding shrinkage rate; determining a gear cavity size according to the gear mold inverse cavity size parameter, and precisely machining the target gear injection mold according to the gear cavity size; performing injection molding of the target gear according to the target gear injection mold to obtain a target gear finished product.

2. The method of claim 1, wherein, The test parameter table for injection molding of the target gear comprises: obtaining a test input parameter of the target gear; determining a process parameter range according to the material properties of the target gear; determining the test parameter table for injection molding of the target gear according to the test input parameter and the process parameter range.

3. The method of claim 2, wherein the gear is a pinion gear. The simulation test is performed according to the test parameter table to obtain a simulation result, including: establishing the target gear simulation model according to the actual molding situation; after selecting an analysis type and an analysis sequence, performing a simulation test according to the test parameter table to obtain a simulation result.

4. The method of claim 1, wherein the gear is a gear for a power steering system. The gear molding shrinkage rate is determined according to the gear sample measurement data, including: after the gear sample is stable, determining the size of the gear sample; determining a gear molding shrinkage rate according to the size of the gear sample.

5. The method of claim 4, wherein the gear is a pinion gear. The gear forming shrinkage is determined according to the size of the gear sample, and the method comprises the steps of: calculating the average dedendum circle diameter of a plurality of gear samples; calculating the gear forming shrinkage according to the average dedendum circle diameter.

6. The method of claim 5, wherein the gear is injection molded. The gear mold inverse cavity size parameter is determined according to the gear forming shrinkage, and the method comprises the steps of: determining the gear mold inverse cavity size parameter according to the modulus of the target gear and the gear forming shrinkage.

7. The method of claim 6, wherein the gear is injection molded. The target gear injection mold is obtained by precision machining according to the gear cavity size, and the method comprises the steps of: keeping the overall structure, cooling system, temperature control system and pouring system of the mold unchanged, and precision machining the mold cavity according to the gear cavity size to obtain the target gear injection mold.

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