A semi-solid magnesium alloy hot runner injection method and apparatus

Abstract

The application discloses a kind of semi-solid magnesium alloy hot runner injection method and equipment, the method is first carried out preliminary design hot runner structure, then optimize hot runner structure, again debug the control system of hot runner structure, finally injection production;Its equipment includes control system, main runner, branch runner, main heater, auxiliary heater, several thermocouples, at least one gate, at least one cylinder and at least one valve needle, by designing suitable semi-solid magnesium alloy hot runner structure and debugging the control system of hot runner structure, again using preferred heating mode, runner shape, runner size, gate form, gate diameter, valve needle shape and valve needle size to produce magnesium alloy product, can reduce runner waste, improve material utilization and precision control filling process.

Description

Technical Field

[0001] This invention relates to the field of metal hot runner manufacturing technology, and in particular to a semi-solid magnesium alloy hot runner injection method and equipment. Background Technology

[0002] With the global pursuit of energy conservation, emission reduction, environmental protection, and efficiency, especially in industries such as automotive, aerospace, and electronics, the demand for weight reduction in components is extremely urgent. Magnesium alloys are ideal materials for achieving lightweighting, especially when weight reduction is required while maintaining volume, rigidity, and machinability, where their advantages are obvious.

[0003] In existing technologies, magnesium alloys are usually processed using die casting. However, the cold runner production process of die casting involves many gates and a lot of runner waste. It also requires shearing to remove the waste, making it impossible to precisely control the filling process and making it unsuitable for producing small and complex precision parts. Summary of the Invention

[0004] The purpose of this invention is to provide a semi-solid magnesium alloy hot runner injection method and equipment that reduces runner waste, improves material utilization, and precisely controls the filling process, so as to solve the problems mentioned in the background art.

[0005] The technical solution of this invention is as follows: This invention discloses a semi-solid magnesium alloy hot runner injection method, comprising the following steps: Step S1: Preliminary design of hot runner structure: Based on the preset specifications of the magnesium alloy products to be produced, the preliminary design parameters of the hot runner structure are given. Step S2: Optimize the hot runner structure: The process involves using flow analysis software to simulate the various preset indicators of the magnesium alloy product to be produced and the preliminary design parameters obtained in step S1. The simulation results in various operating parameters of the magnesium alloy melt in the flow channel. Based on the simulated operating parameters in the flow channel, the preliminary design parameters of the flow channel structure are adjusted to obtain the optimized design parameters of the hot runner structure. Step S3: Debug the control system of the hot runner structure: Based on the optimized design parameters of the hot runner structure obtained in step S2, the optimized hot runner structure is obtained. The control parameters of the control system (1) of the hot runner structure are adjusted to perform injection control. The parameters of the magnesium alloy sample obtained by injection are analyzed to determine whether it is qualified. If it is qualified, step S4 is executed. If it is not qualified, step S2 is returned and steps S2 and S3 are repeated until the parameters of the magnesium alloy product obtained by injection are qualified. Step S4, Injection Production: Solid magnesium alloy is heated to a semi-solid state to form a solid-liquid two-phase slurry. The semi-solid magnesium alloy is then injected into a hot runner structure. Using the final optimized hot runner structure and a control system with all control parameters properly adjusted, the semi-solid magnesium alloy is controlled to smoothly fill the mold cavity. The plastic material is then allowed to cool and solidify fully to obtain the injection-molded magnesium alloy product.

[0006] Furthermore, in step S1, the preset indicators include structural shape, size and quality requirements, and the preliminary design parameters include the heating method of the hot runner, the runner shape, the runner size, the gate type, the gate diameter, the valve needle shape and the valve needle size; In step S2, the operating parameters include pressure loss, flow rate, temperature change, heat distribution in the hot runner, real-time temperature data in the runner, and thermal expansion of the valve needle.

[0007] Furthermore, the control system of the hot runner structure includes a temperature control unit and a cylinder drive unit. The optimized hot runner structure obtained in step S2 is used for actual operation. Preliminary temperature control commands and cylinder drive commands are input to inject and generate the corresponding magnesium alloy product. The status of the magnesium alloy product is checked, and the temperature control unit and cylinder drive unit are adjusted accordingly. When a qualified magnesium alloy product is obtained and the control system is running stably, the parameters of the debugged hot runner control system are locked. Step S4, Injection Molding: Solid magnesium alloy is heated to a semi-solid state to form a solid-liquid two-phase slurry. The semi-solid magnesium alloy is then injected into a hot runner structure. Using the final optimized hot runner structure and a control system with all control parameters properly adjusted, the semi-solid magnesium alloy is controlled to smoothly fill the mold cavity. The plastic material is then allowed to cool and solidify fully to obtain the injection-molded magnesium alloy product.

[0008] Furthermore, in step S1, when the required magnesium alloy product size is within 50mm*50mm, wall thickness is less than 1mm, and weight is less than 100g, it is defined as a small product. The shape of the runner can be any one of circular, trapezoidal, or semi-circular. Circular runners have the lowest flow resistance, are the most commonly used, are easy to process, and have low pressure loss. The diameter of the main runner is 20mm-25mm, and the diameter of the branch runners is 10mm-15mm. Using a runner with a suitable diameter can reduce waste and thermal inertia. The gate type can be a point gate or a side gate. Point gates are suitable for small parts with high appearance requirements, as they have small gates and small marks, while side gates are simple to process. The valve needle is generally cylindrical, with a diameter of 8mm-12mm. The hot runner is a closed structure, which is to directly seal it after injection to prevent the slurry from flowing out. The heating method is local electric heating, and heating coils or heating strips can be set only on the branch runners. When the required magnesium alloy product size ranges from 50mm*50mm to 200mm*200mm, the wall thickness ranges from 1.0mm to 2.0mm, and the weight ranges from 100g to 500g, it is defined as a medium-sized product. The shape of the runner can be either circular or trapezoidal, with circular runners being the preferred choice as they facilitate pressure transmission and filling control. The diameter of the main runner ranges from 25mm to 30mm, and the diameter of the branch runners ranges from 15mm to 20mm, suitable for medium injection volumes and balancing pressure and heat. The gate type can be any of the following: point gate, side gate, or fan gate. The fan gate is suitable for uniform filling; the side gate is universal; the point gate is used for multi-cavity applications or those with high appearance requirements. The valve needle is generally cylindrical, with a diameter of 12mm to 18mm. The heating method is a zoned electric heating method, meaning that heating rods or heating bands are installed in both the main runner and the branch runners to ensure the fluidity of the semi-solid slurry and prevent premature solidification. When the required magnesium alloy product size is 200mm*200mm or larger, wall thickness is 0.8mm-2.0mm, and weight is greater than 500g, it is defined as a large product. The runner shape can be circular, with the main runner diameter ranging from 30mm to 35mm and the branch runner diameter ranging from 20mm to 25mm, suitable for high-flow injection to ensure filling capacity. The gate type can be any of the following: fan-shaped gate, side gate, or submersible gate. The fan-shaped gate is suitable for large-area uniform injection; multi-point injection can improve filling balance. The valve needle is generally cylindrical, with a diameter of 18mm-32mm. The heating method is multi-zone electric heating, that is, heating rods or heating bands are set in the main runner, branch runners, and gate. It is necessary to ensure that the slurry in the long runner does not solidify prematurely, especially at the gate position.

[0009] Furthermore, in step S2, when the simulation shows excessive pressure loss at a certain section of the runner or gate, excessive pressure loss means that higher injection pressure and longer filling time are required, which will lead to: Increased energy consumption, increased wear on molds and machines, short shots that may occur due to insufficient filling or excessively thick condensate layer, and melt degradation due to shear overheating can all be addressed by increasing the runner diameter or changing the runner shape, such as changing a circular runner shape to a trapezoidal runner shape to improve heat distribution, reducing flow rate, reducing shear, and thus significantly reducing pressure loss. The adjustment of runner size usually follows the runner balance principle, that is, ensuring that the melt reaches the end of each cavity simultaneously.

[0010] Furthermore, in step S2, when the simulation shows that the flow rate is too high or too low, an excessively high flow rate will lead to a high shear rate, which may destroy the thixotropic properties of the semi-solid slurry, causing "jetting," air entrainment, or defects such as flow marks on the product surface; when the flow rate is too low, the temperature at the melt front drops too quickly, which may lead to cold welds or short shots; the flow rate can be controlled within an optimal range by adjusting the flow channel size, increasing the cross-section to reduce the flow rate, or decreasing the cross-section to increase the flow rate, or by changing the gate form, such as using a fan-shaped gate to flatten the flow rate.

[0011] Furthermore, in step S2, when the simulation shows that the temperature of the melt drops too much after passing through the gate, the gate is the last barrier for the melt to enter the cavity, and its thermal state directly determines the filling quality. It is necessary to ensure that the melt enters the cavity within a precise temperature range. Increasing the gate size can reduce shear heat generation and pressure loss, while decreasing the gate size can increase the shear rate, which is beneficial for breaking up the particle structure. However, a careful balance must be struck. Changing from a direct pin gate to a fan-shaped gate or a convex gate can avoid jetting and allow the melt to enter the cavity smoothly.

[0012] Furthermore, in step S2, when the mold flow analysis software predicts defects that may be caused by improper gate position and form, such as air pockets, weld line position and strength, the gate position can be changed or a combined gate form can be used to guide the melt flow direction, thereby controlling the generation and position of defects, optimizing defect distribution, driving them to non-visual surfaces or positions that facilitate venting, or enhancing the strength of weld lines by changing the melt convergence angle.

[0013] Further, in step S2, when the simulation shows that the valve needle diameter increases due to thermal expansion at the operating temperature, the thermal expansion amount is subtracted as follows: Valve needle machining diameter = Ideal working diameter - Simulated thermal expansion amount. Ideal working diameter: A design value determined based on sealing requirements, friction coefficient, and other factors; this is the essence of hot runner system design. Thermal expansion amount: , It is the coefficient of linear expansion of the material. It is the initial diameter. Temperature changes are a factor, and flow analysis software can provide more accurate data on non-uniform expansion based on the actual temperature field. If the cold (room temperature) diameter of the valve needle is designed according to the ideal clearance, then after expansion at the operating temperature, it will seize up with the runner wall or gate or suffer severe wear, resulting in malfunction (poor opening and closing), leakage, or damage.

[0014] When simulations show overheated "hot spots" or undercooled "cold spots" inside the hot runner, uneven heat distribution can lead to: uneven melt temperature, inconsistent product quality; localized material degradation; and increased thermal stress on valve needles and heating elements, reducing their lifespan. Therefore, the layout and power of the heating coils can be adjusted, or materials with different thermal conductivity (such as beryllium copper sleeves) can be added / adjusted to ensure a uniform and stable temperature throughout the entire runner system.

[0015] In step S2, flow analysis software is used to automatically calculate the flow path length from the gate to each point in the magnesium alloy mold cavity. Combined with the local wall thickness of the product input by the user, the flow length ratio is automatically calculated and displayed. When the magnesium alloy product to be produced is a small product, the flow length ratio is set to less than 80:1; when the magnesium alloy product to be produced is a medium-sized product, the flow length ratio is set to 80:1-100:1; when the magnesium alloy product to be produced is a large product, the flow length ratio is set to 100:1-150:1.

[0016] Regarding the pressure values ​​of the hot runner, the maximum injection pressure should be less than 70-80% of the rated pressure of the injection molding machine. The pressure loss in each section of the runner should be uniform and as small as possible. The flow velocity at the gate should be lower than the critical value that causes turbulence or jetting, and lower than the critical shear rate that causes structural damage to the magnesium alloy. The cooling rate of each part of the product should be relatively uniform. The valve needle and the runner should maintain an optimal fit clearance (e.g., 5-15μm) that can both seal and prevent jamming. All parameters should be iterated until convergence, until all key indicators of the simulation results enter the previously set ideal process window. The runner, gate, and valve needle dimensions obtained at this time are the optimized parameters.

[0017] Furthermore, in step S3, the working temperatures of the main runner, branch runner, and gate are controlled within 580℃-600℃ after debugging. When the temperature difference between the main runner, branch runner, and gate is ≤10℃, preferably ≤5℃, the cylinder drive unit is started.

[0018] This invention also discloses a semi-solid magnesium alloy hot runner injection apparatus for performing the above-described semi-solid magnesium alloy hot runner injection method. It includes a control system, a main runner, branch runners, a main heater, an auxiliary heater, several thermocouples, at least one gate, at least one cylinder, and at least one valve needle. The control system is electrically connected to the main heater, the auxiliary heater, the thermocouples, and the cylinder. The thermocouples are located near the main runner, the branch runners, and the gate. The main heater is located on the periphery of the main runner. The auxiliary heater is located on the surface of the branch runners and the gate. The cylinder drives and connects to the valve needle, which penetrates the branch runners and the gate. The main runner is interconnected with the branch runners and the gate.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: by designing a hot runner structure suitable for semi-solid magnesium alloys and adjusting the control system of the hot runner structure, and by adopting the preferred heating method, runner shape, runner size, gate form, gate diameter, valve needle shape and valve needle size for the production of magnesium alloy products, it is possible to reduce runner waste, improve material utilization and precisely control the filling process. Attached Figure Description

[0020] Figure 1 This is a flowchart illustrating a semi-solid magnesium alloy hot runner injection method according to the present invention. Figure 2 This is a circuit block diagram of the control system used in the semi-solid magnesium alloy hot runner injection method of the present invention. Figure 3 This is a cross-sectional structural diagram of a semi-solid magnesium alloy hot runner injection device according to the present invention. Figure 4 for Figure 3 A schematic diagram of the overall structure.

[0021] Reference numerals: 1. Control system; 11. Temperature control unit; 12. Cylinder drive unit; 2. Main runner; 3. Branch runner; 4. Main heater; 5. Auxiliary heater; 6. Thermocouple; 7. Gate; 8. Cylinder; 9. Valve needle. Detailed Implementation

[0022] Please refer to Figure 1 and Figure 2 This invention provides a semi-solid magnesium alloy hot runner injection method, comprising the following steps: Step S1: Preliminary design of hot runner structure: Based on the preset specifications of the magnesium alloy products to be produced, the preliminary design parameters of the hot runner structure are given. Specifically, when the required magnesium alloy product size is within 50mm*50mm, wall thickness is less than 1mm, and weight is less than 100g, it is defined as a small product. The shape of the runner can be any one of circular, trapezoidal, or semi-circular. Circular runners have the lowest flow resistance, are the most commonly used, are easy to process, and have low pressure loss. The diameter of the main runner is 20mm-25mm, and the diameter of the branch runners is 10mm-15mm. Using a runner with a suitable diameter can reduce waste and thermal inertia. The gate type can be a point gate or a side gate. Point gates are suitable for small parts with high appearance requirements, as they have small gates and small marks, while side gates are simple to process. The valve needle is generally cylindrical, with a diameter of 8mm-12mm. The hot runner is a closed structure, which is to directly seal after injection to prevent the slurry from flowing out. The heating method is local electric heating, and heating coils or heating strips can be set only on the branch runners. When the required magnesium alloy product size ranges from 50mm*50mm to 200mm*200mm, the wall thickness ranges from 1.0mm to 2.0mm, and the weight ranges from 100g to 500g, it is defined as a medium-sized product. The shape of the runner can be either circular or trapezoidal, with circular runners being the preferred choice as they facilitate pressure transmission and filling control. The diameter of the main runner ranges from 25mm to 30mm, and the diameter of the branch runners ranges from 15mm to 20mm, suitable for medium injection volumes and balancing pressure and heat. The gate type can be any of the following: point gate, side gate, or fan gate. The fan gate is suitable for uniform filling; the side gate is universal; the point gate is used for multi-cavity applications or those with high appearance requirements. The valve needle is generally cylindrical, with a diameter of 12mm to 18mm. The heating method is a zoned electric heating method, meaning that heating rods or heating bands are installed in both the main runner and the branch runners to ensure the fluidity of the semi-solid slurry and prevent premature solidification. When the required magnesium alloy product size is 200mm*200mm or larger, wall thickness is 0.8mm-2.0mm, and weight is greater than 500g, it is defined as a large product. The runner shape can be circular, with the main runner diameter ranging from 30mm to 35mm and the branch runner diameter ranging from 20mm to 25mm, suitable for high-flow injection to ensure filling capacity. The gate type can be any of the following: fan-shaped gate, side gate, or submersible gate. The fan-shaped gate is suitable for large-area uniform injection; multi-point injection can improve filling balance. The valve needle is generally cylindrical, with a diameter of 18mm-32mm. The heating method is multi-zone electric heating, that is, heating rods or heating bands are set in the main runner, branch runners, and gate. It is necessary to ensure that the slurry in the long runner does not solidify prematurely, especially at the gate position.

[0023] Step S2: Optimize the hot runner structure: The process involves using flow analysis software to simulate the various preset indicators of the magnesium alloy product to be produced and the preliminary design parameters obtained in step S1. The simulation results in various operating parameters of the magnesium alloy melt in the flow channel. Based on the simulated operating parameters in the flow channel, the preliminary design parameters of the flow channel structure are adjusted to obtain the optimized design parameters of the hot runner structure. Step S3: Debug the control system of the hot runner structure: Based on the optimized design parameters of the hot runner structure obtained in step S2, the optimized hot runner structure is obtained. The control parameters of the control system (1) of the hot runner structure are adjusted to perform injection control. The parameters of the magnesium alloy sample obtained by injection are analyzed to determine whether it is qualified. If it is qualified, step S4 is executed. If it is not qualified, step S2 is returned and steps S2 and S3 are repeated until the parameters of the magnesium alloy product obtained by injection are qualified. Step S4, Injection Production: Solid magnesium alloy is heated to a semi-solid state to form a solid-liquid two-phase slurry. The semi-solid magnesium alloy is then injected into a hot runner structure. Using the final optimized hot runner structure and a control system with all control parameters properly adjusted, the semi-solid magnesium alloy is controlled to smoothly fill the mold cavity. The plastic material is then allowed to cool and solidify fully to obtain the injection-molded magnesium alloy product.

[0024] Furthermore, in step S1, the preset indicators include structural shape, size and quality requirements, and the preliminary design parameters include the heating method of the hot runner, the runner shape, the runner size, the gate type, the gate diameter, the valve needle shape and the valve needle size; In step S2, the operating parameters include pressure loss, flow rate, temperature change, heat distribution in the hot runner, real-time temperature data in the runner, and thermal expansion of the valve needle.

[0025] Specifically: The flow analysis software is used to simulate the shape, size, structure, quality requirements of the magnesium alloy product to be produced and the preliminary hot runner structure in step S1. The software simulates the pressure loss, flow rate and temperature change of the magnesium alloy melt in the runner, as well as the heat distribution and real-time temperature data in the runner. It also simulates the thermal expansion of the valve needle, thereby adjusting the runner shape, runner size, gate type, gate diameter, valve needle shape and valve needle size to obtain the optimized hot runner structure. The optimized valve needle diameter parameter is obtained by subtracting the thermal expansion. Step S3: Debug the control system of the hot runner structure: The hot runner structure control system 1 includes a temperature control unit 11 and a cylinder drive unit 12. The optimized hot runner structure obtained in step S2 is used for actual operation. The initial temperature control command and cylinder drive command are input, and the corresponding magnesium alloy product is injected. The status of the magnesium alloy product is checked, and the temperature control unit and cylinder drive unit are adjusted accordingly. When a qualified magnesium alloy product is obtained and the control system is running stably, the parameters of the hot runner control system after debugging are locked. Step S4, Injection Molding: Solid magnesium alloy is heated to a semi-solid state to form a solid-liquid two-phase slurry. The semi-solid magnesium alloy is then injected into a hot runner structure. Using the final optimized hot runner structure and a control system with all control parameters properly adjusted, the semi-solid magnesium alloy is controlled to smoothly fill the mold cavity. The plastic material is then allowed to cool and solidify fully to obtain the injection-molded magnesium alloy product.

[0026] In step S2, when the simulation shows excessive pressure loss at a certain section of the runner or gate, excessive pressure loss means that higher injection pressure and longer filling time are required, which will lead to: Increased energy consumption, increased wear on molds and machines, short shots that may occur due to insufficient filling or excessively thick condensate layer, and melt degradation due to shear overheating can all be addressed by increasing the runner diameter or changing the runner shape, such as changing a circular runner shape to a trapezoidal runner shape to improve heat distribution, reducing flow rate, reducing shear, and thus significantly reducing pressure loss. The adjustment of runner size usually follows the runner balance principle, that is, ensuring that the melt reaches the end of each cavity simultaneously.

[0027] Furthermore, in step S2, when the simulation shows that the flow rate is too high or too low, an excessively high flow rate will lead to a high shear rate, which may destroy the thixotropic properties of the semi-solid slurry, causing "jetting," air entrainment, or defects such as flow marks on the product surface; when the flow rate is too low, the temperature at the melt front drops too quickly, which may lead to cold welds or short shots; the flow rate can be controlled within an optimal range by adjusting the flow channel size, increasing the cross-section to reduce the flow rate, or decreasing the cross-section to increase the flow rate, or by changing the gate form, such as using a fan-shaped gate to flatten the flow rate.

[0028] Furthermore, in step S2, when the simulation shows that the temperature of the melt drops too much after passing through the gate, the gate is the last barrier for the melt to enter the cavity, and its thermal state directly determines the filling quality. It is necessary to ensure that the melt enters the cavity within a precise temperature range. Increasing the gate size can reduce shear heat generation and pressure loss, while decreasing the gate size can increase the shear rate, which is beneficial for breaking up the particle structure. However, a careful balance must be struck. Changing from a direct pin gate to a fan-shaped gate or a convex gate can avoid jetting and allow the melt to enter the cavity smoothly.

[0029] Furthermore, in step S2, when the mold flow analysis software predicts defects that may be caused by improper gate position and form, such as air pockets, weld line position and strength, the gate position can be changed or a combined gate form can be used to guide the melt flow direction, thereby controlling the generation and position of defects, optimizing defect distribution, driving them to non-visual surfaces or positions that facilitate venting, or enhancing the strength of weld lines by changing the melt convergence angle.

[0030] Further, in step S2, when the simulation shows that the valve needle diameter increases due to thermal expansion at the operating temperature, the thermal expansion amount is subtracted as follows: Valve needle machining diameter = Ideal working diameter - Simulated thermal expansion amount. Ideal working diameter: A design value determined based on sealing requirements, friction coefficient, and other factors; this is the essence of hot runner system design. Thermal expansion amount: , It is the coefficient of linear expansion of the material. It is the initial diameter. Temperature changes are a factor, and flow analysis software can provide more accurate data on non-uniform expansion based on the actual temperature field. If the cold (room temperature) diameter of the valve needle is designed according to the ideal clearance, then after expansion at the operating temperature, it will seize up with the runner wall or gate or suffer severe wear, resulting in malfunction (poor opening and closing), leakage, or damage.

[0031] When simulations show overheated "hot spots" or undercooled "cold spots" inside the hot runner, uneven heat distribution can lead to: uneven melt temperature, inconsistent product quality; localized material degradation; and increased thermal stress on valve needles and heating elements, reducing their lifespan. Therefore, the layout and power of the heating coils can be adjusted, or materials with different thermal conductivity (such as beryllium copper sleeves) can be added / adjusted to ensure a uniform and stable temperature throughout the entire runner system.

[0032] In step S2, flow analysis software is used to automatically calculate the flow path length from the gate to each point in the magnesium alloy mold cavity. Combined with the local wall thickness of the product input by the user, the flow length ratio is automatically calculated and displayed. When the magnesium alloy product to be produced is a small product, the flow length ratio is set to less than 80:1; when the magnesium alloy product to be produced is a medium-sized product, the flow length ratio is set to 80:1-100:1; when the magnesium alloy product to be produced is a large product, the flow length ratio is set to 100:1-150:1.

[0033] Regarding the pressure values ​​of the hot runner, the maximum injection pressure should be less than 70-80% of the rated pressure of the injection molding machine. The pressure loss in each section of the runner should be uniform and as small as possible. The flow velocity at the gate should be lower than the critical value that causes turbulence or jetting, and lower than the critical shear rate that causes structural damage to the magnesium alloy. The cooling rate of each part of the product should be relatively uniform. The valve needle and the runner should maintain an optimal fit clearance (e.g., 5-15μm) that can both seal and prevent jamming. All parameters should be iterated until convergence, until all key indicators of the simulation results enter the previously set ideal process window. The runner, gate, and valve needle dimensions obtained at this time are the optimized parameters.

[0034] In step S2, flow analysis software is used to automatically calculate the flow path length from the gate to each point in the magnesium alloy mold cavity. Combined with the local wall thickness of the product input by the user, the flow length ratio is automatically calculated and displayed. When the magnesium alloy product to be produced is a small product, the flow length ratio is set to less than 80:1; when the magnesium alloy product to be produced is a medium-sized product, the flow length ratio is set to 80:1-100:1; when the magnesium alloy product to be produced is a large product, the flow length ratio is set to 100:1-150:1.

[0035] Reference Figure 3 and Figure 4 The present invention also discloses a semi-solid magnesium alloy hot runner injection apparatus for performing the above-mentioned semi-solid magnesium alloy hot runner injection method. It includes a control system 1, a main runner 2, a branch runner 3, a main heater 4, an auxiliary heater 5, four thermocouples 6, two gates 7, two cylinders 8, and two valve needles 9. The control system 1 is electrically connected to the main heater 4, the auxiliary heater 5, the thermocouples 6, and the cylinders 8. The thermocouples 6 are located near the main runner 2, the branch runner 3, and the gates 7. The main heater 4 is located on the periphery of the main runner 2. The auxiliary heater 5 is located on the surface of the branch runner 3 and the gates 7. The cylinders 8 drive and connect to the valve needles 9. The valve needles 9 are inserted through the branch runner 3 and the gates 7. The main runner 2 is interconnected with the branch runner 3 and the gates 7.

[0036] It is worth noting that injection molding of such magnesium alloy products uses hot runners, resulting in less dimensional deformation.

[0037] The above-described embodiments are merely one implementation of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method for hot runner injection molding of semi-solid magnesium alloy, characterized in that, Includes the following steps: Step S1: Preliminary design of hot runner structure: Based on the preset specifications of the magnesium alloy products to be produced, the preliminary design parameters of the hot runner structure are given. Step S2: Optimize the hot runner structure: The process involves using flow analysis software to simulate the various preset indicators of the magnesium alloy product to be produced and the preliminary design parameters obtained in step S1. The simulation results in various operating parameters of the magnesium alloy melt in the flow channel. Based on the simulated operating parameters in the flow channel, the preliminary design parameters of the flow channel structure are adjusted to obtain the optimized design parameters of the hot runner structure. Step S3: Debug the control system of the hot runner structure: Based on the optimized design parameters of the hot runner structure obtained in step S2, the optimized hot runner structure is obtained. The control parameters of the control system (1) of the hot runner structure are adjusted to perform injection control. The parameters of the magnesium alloy sample obtained by injection are analyzed to determine whether it is qualified. If it is qualified, step S4 is executed. If it is not qualified, step S2 is returned and step S2 and S3 are repeated until the parameters of the magnesium alloy product obtained by injection are qualified. Step S4, Injection Molding: Solid magnesium alloy is heated to a semi-solid state to form a solid-liquid two-phase slurry. The semi-solid magnesium alloy is then injected into a hot runner structure. Using the final optimized hot runner structure and a control system with all control parameters properly adjusted, the semi-solid magnesium alloy is controlled to smoothly fill the mold cavity. The plastic material is then allowed to cool and solidify fully to obtain the injection-molded magnesium alloy product.

2. The semi-solid magnesium alloy hot runner injection method according to claim 1, characterized in that, In step S1, the preset indicators include structural shape, size and quality requirements, and the preliminary design parameters include the heating method of the hot runner, the runner shape, the runner size, the gate type, the gate diameter, the valve needle shape and the valve needle size; In step S2, the operating parameters include pressure loss, flow rate, temperature change, heat distribution in the hot runner, real-time temperature data in the runner, and thermal expansion of the valve needle.

3. The semi-solid magnesium alloy hot runner injection method according to claim 2, characterized in that, In step S1, when the required magnesium alloy product size is within 50mm*50mm, wall thickness is <1mm, and weight is <100g, it is defined as a small product. The shape of the runner can be any one of circular, trapezoidal, or semi-circular. The diameter of the main runner is 20mm-25mm, the diameter of the branch runner is 10mm-15mm, the gate type can be a point gate or a side gate, the valve needle is cylindrical, the valve needle diameter is 8mm-12mm, and the heating method is local electric heating. When the required magnesium alloy product size ranges from 50mm*50mm to 200mm*200mm, the wall thickness ranges from 1.0mm to 2.0mm, and the weight ranges from 100g to 500g, it is defined as a medium-sized product. The runner shape can be circular or trapezoidal, the main runner diameter ranges from 25mm to 30mm, the branch runner diameter ranges from 15mm to 20mm, the gate type can be any one of point gate, side gate, or fan gate, the valve needle is cylindrical, the valve needle diameter is 12mm to 18mm, and the heating method is zoned electric heating. When the required magnesium alloy product size is 200mm*200mm or larger, the wall thickness is 0.8mm-2.0mm, and the weight is greater than 500g, it is defined as a large product. The runner shape is circular, the main runner diameter is 30mm-35mm, the branch runner diameter is 20mm-25mm, the gate type is any one of fan-shaped point gate, side gate or submarine gate, the valve needle is cylindrical, the valve needle diameter is 18mm-32mm, and the heating method is multi-zone electric heating.

4. The semi-solid magnesium alloy hot runner injection method according to claim 3, characterized in that, In step S2, when the simulation shows that the pressure loss at a certain section of the flow channel or gate is too large, the flow channel diameter can be increased or the flow channel shape can be changed, such as changing the circular flow channel shape to a trapezoidal flow channel shape. In step S2, when the simulated flow rate is too high or too low, the flow rate can be reduced by adjusting the flow channel size, increasing the cross-section to reduce the cross-section, or increasing the cross-section to increase the flow rate, or the gate form can be changed, such as using a fan-shaped gate to flatten the flow rate.

5. The semi-solid magnesium alloy hot runner injection method according to claim 3, characterized in that, In step S2, when the simulation shows that the temperature of the melt drops too much after passing through the gate, the gate size can be increased to reduce shear heat generation and pressure loss, while the gate size can be decreased to increase the shear rate. The gate can be changed from a direct pin gate to a fan-shaped gate or a convex gate.

6. The semi-solid magnesium alloy hot runner injection method according to claim 3, characterized in that, In step S2, when the mold flow analysis software predicts the defects that may be caused by improper gate position and form, the gate position can be changed or a combination gate form can be used to guide the melt flow direction.

7. The semi-solid magnesium alloy hot runner injection method according to claim 3, characterized in that, In step S2, when the simulation shows that the valve needle diameter increases due to thermal expansion at the operating temperature, the thermal expansion amount is subtracted as follows: valve needle machining diameter = ideal working diameter - simulated thermal expansion amount.

8. The semi-solid magnesium alloy hot runner injection method according to claim 4, characterized in that, In step S3, the working temperature of the main runner, branch runner and gate is controlled within 580℃-600℃ after debugging. When the temperature difference between the main runner, gate and branch runner is ≤10℃, the cylinder drive unit is started.

9. The semi-solid magnesium alloy hot runner injection method according to claim 3, characterized in that, In step S2, flow analysis software is used to automatically calculate the flow path length from the gate to each point in the magnesium alloy mold cavity. Combined with the local wall thickness of the product input by the user, the flow length ratio is automatically calculated and displayed. When the magnesium alloy product to be produced is a small product, the flow length ratio is set to less than 80:1; when the magnesium alloy product to be produced is a medium-sized product, the flow length ratio is set to 80:1-100:1; when the magnesium alloy product to be produced is a large product, the flow length ratio is set to 100:1-150:

1.

10. A semi-solid magnesium alloy hot runner injection molding machine, characterized in that, It is used to perform the semi-solid magnesium alloy hot runner injection method as described in any one of claims 1-9, and includes a control system (1), a main runner (2), a branch runner (3), a main heater (4), an auxiliary heater (5), a plurality of thermocouples (6), at least one gate (7), at least one cylinder (8) and at least one valve needle (9). The control system (1) is electrically connected to the main heater (4), the auxiliary heater (5), the thermocouples (6) and the cylinder (8). The thermocouples (6) are located near the main runner (2), the branch runner (3) and the gate (7). The main heater (4) is located on the periphery of the main runner (2). The auxiliary heater (5) is located on the surface of the branch runner (3) and the gate (7). The cylinder (8) drives and connects to the valve needle (9). The valve needle (9) is disposed through the branch runner (3) and the gate (7). The main runner (2) is interconnected with the branch runner (3) and the gate (7).

Images