Filtering process for foundry sand treatment process

Abstract

The application relates to the field of foundry molding, and discloses a filtering process for a foundry sand treatment process, which comprises the following steps: according to surface roughness requirements of a to-be-molded task and a conveying time delay parameter, a sand flow distribution valve is controlled to pre-load specific grain size sand into a temporary storage bin; when physical parameters of the molding sand deviate from a reference interval, a downstream molding machine is used to drive an asymmetric Venturi ejector to generate pneumatic shearing force through an exhaust pulse, the molding sand in the temporary storage bin is inhaled, a residence time in a throat pipe section is constrained, a bentonite hydration film is subjected to shear thinning to release an adhered state and prevent the original sand from being broken, the application realizes phase alignment between the molding sand supply and the molding task, eliminates quality dislocation caused by conveying lag, and uses molding back pressure energy to achieve in-situ awakening of physical activity of the molding sand, breaks through physical restrictions between disaggregation of aggregates and breaking of the original sand, and guarantees process robustness under intelligent foundry island change-over working conditions.

Description

Technical Field

[0001] This invention belongs to the field of casting molding technology, and in particular relates to a filtration process for casting sand treatment. Background Technology

[0002] The particle size distribution and physical stability of the current molding sand particles determine the surface quality of the castings. Conventional sand treatment processes use fixed aperture screens and mechanical vibration to produce homogeneous molding sand, which is then supplied to the entire molding production line.

[0003] With the application of the flexible manufacturing mode of intelligent foundry islands, the requirements for molding sand particle size distribution in molding tasks change frequently with the production cycle. Existing filtration and adjustment schemes face the constraint of physical conveying lag when dealing with such sudden changes in demand. Because there are physical conveying pipelines between the filtration equipment and the downstream molding machine, when the molding system issues a specific quality task instruction, the specification molding sand produced at the filtration station cannot immediately reach the molding station, resulting in a phase misalignment between the residual sand in the pipeline and the current task requirement. In addition to the limitations of hardware structure layout, existing technical control strategies fail to take into account the dynamic balance of material flow. For example, publication number CN12 Chinese invention patent application 0961844A discloses an intelligent casting sand mixing equipment based on dynamic compensation. By monitoring the liquid flow rate and adjusting the rotation speed of the shaft to control the intervention state of the spiral blades, it solves the problem of sand solidification under short-term shutdown conditions. The technical basis of this solution lies in the strength compensation of the front-end mixing stage. However, it does not address the problem of physical activity decay caused by the static placement of wet molding sand in long-distance conveying pipelines. Mechanical low-speed stirring delays solidification and is difficult to solve the phase difference between the molding sand at the end of the conveying process and the molding task. It is also unable to achieve physical decoupling between the deagglomeration force field and the mechanical crushing threshold of the original sand when peeling off the secondary agglomerates on the surface of the wet molding sand.

[0004] Therefore, how to eliminate the phase misalignment of the physical pipeline through feedforward scheduling and construct a transient shear backflow mechanism to avoid mechanical damage to the raw sand has become the technical problem to be solved by this invention. Summary of the Invention

[0005] The present invention aims to solve the problems of delayed switching of molding sand quality caused by the time delay of physical pipeline transportation and the breakage of raw sand during the reflow process of wet molding sand.

[0006] In this technical solution, a filtration process for casting sand treatment includes the following steps:

[0007] Step S1: The process control unit reads the molding tasks in the task queue and obtains the surface roughness requirements of the mold, the delay constant of the conveying pipeline from the sand mixer to the molding sand storage bin, and the residual volume of the previous batch of molding sand in the conveying pipeline corresponding to the molding task.

[0008] Step S2: Based on the surface roughness requirements of the mold, determine the particle size distribution index of the target molding sand and the corresponding molding sand compaction rate benchmark range and molding sand permeability benchmark range. Calculate the preloading advance amount based on the delay constant of the conveying pipeline and the residual volume of the previous batch of molding sand. At the preloading advance amount node before the start of the molding task, drive the sand flow distribution valve to guide the molding sand output from the sand mixer to a filter path with corresponding filter aperture, and load molding sand that meets the particle size distribution index into the molding sand temporary storage bin.

[0009] Step S3: The compaction rate and air permeability of the molding sand in the molding sand storage chamber are measured by a physical state detection probe. When the compaction rate deviates from the benchmark range of molding sand compaction rate or the air permeability deviates from the benchmark range of molding sand air permeability, the pneumatic branch between the bottom return port of the molding sand storage chamber and the sand injection exhaust valve of the downstream molding machine is opened, and the high-pressure exhaust pulse of 0.5MPa to 0.7MPa generated by the downstream molding machine is introduced into the asymmetric venturi injector.

[0010] Step S4: Using the pneumatic shear force generated by the high-pressure exhaust pulse in the throat section of the asymmetric Venturi injector, deteriorated molding sand in the molding sand storage chamber is sucked in. The residence time of the molding sand in the throat section is controlled to be 10ms to 15ms. This is to peel off the bentonite hydration film on the surface of the molding sand while ensuring that the kinetic energy of the raw quartz sand is lower than its mechanical crushing threshold. After deagglomeration, the molding sand is introduced into the expansion section for deceleration and sprayed into the filtration path.

[0011] Preferably, step S2 includes: the process control unit extracts the minimum draft angle and the length-to-diameter ratio of the cavity depth hole for the molding task; when the minimum draft angle is lower than the preset critical value and the length-to-diameter ratio of the cavity depth hole is higher than the preset threshold, the maximum allowable impurity particle size in the particle size distribution index is reduced, and the bypass backfill pipeline is opened to replenish fine sand with a mesh size higher than the preset value to the molding sand temporary storage bin.

[0012] Preferably, step S3 includes: the process control unit determines a shear compensation coefficient based on the difference between the measured compaction rate and the benchmark range of the molding sand compaction rate, and adjusts the throat flow cross-sectional area of ​​the asymmetric Venturi injector according to the shear compensation coefficient.

[0013] Preferably, the cone angle of the reduced diameter section of the asymmetric venturi injector is 15° to 22°, the cone angle of the expanded diameter section is 4° to 6°, and the effective length of the throat section is 30mm to 50mm.

[0014] Preferably, step S2 further includes: during the transition period of molding sand type switching after the sand flow distribution valve is reversed, opening the mixing and unloading valve at the inlet end of the molding sand temporary storage bin to discharge the mixed sand material formed by mixing molding sand with different particle size indexes in the conveying pipeline into the waste sand recycling stream.

[0015] Preferably, step S4 further includes: utilizing the difference in mass density between the raw quartz sand and the stripped dust, the dust is discharged from the molding sand storage bin at the end of the expansion section via a pneumatic diversion interface.

[0016] Preferably, the inner wall of the asymmetric Venturi injector is provided with an anti-wear liner, and the surface of the anti-wear liner has a micro-rough structure that induces boundary layer turbulence, which is used to enhance the mechanical stripping effect of pneumatic shear force on the surface of sand particles.

[0017] Preferably, step S4 further includes: recording the settling time of the current batch of molding sand in the molding sand temporary storage bin, extracting the time compensation coefficient based on the settling time and adding it to the reflux ratio calculation model, so that molding sand with a settling time exceeding the rest threshold is discharged through the reflux port.

[0018] Preferably, the filtration process is integrated into the intelligent casting island, and the central control system of the intelligent casting island monitors the exhaust pressure waveform of the downstream molding machine and corrects the delay constant of the delivery pipeline online accordingly.

[0019] Compared with existing technologies, the filtration process of this invention for foundry sand treatment has the following advantages:

[0020] 1. In the filtration process of foundry sand treatment, phase alignment between molding sand supply and molding task is achieved, eliminating quality misalignment caused by physical conveying delay. The surface quality requirement parameters of the molding task are extracted by the process control unit and scheduling instructions are generated in advance in combination with the physical pipeline conveying time parameters. This allows the temporary storage unit to preload specific quality molding sand for the next task before the current molding task ends. This collaborative mechanism based on information flow feedforward and physical space temporary storage cuts off the rigid physical coupling between the upstream filtration station and the downstream molding station, ensuring that the molding machine can immediately obtain a precisely matched batch of molding sand when switching between different specifications of casting tasks, avoiding surface defects of castings caused by residual sand in traditional pipelines.

[0021] 2. To achieve in-situ awakening of the physical activity of wet molding sand and overcome the physical constraints between deagglomeration effect and raw sand crushing, this process uses the transient high-pressure exhaust pulse generated by the sand shooting action of the downstream molding machine as the driving source. A high-speed pneumatic shear flow field is generated through an asymmetric Venturi injector. This flow field utilizes the thixotropic properties of the bentonite hydration film under strong shear to complete the tearing and peeling of pseudo-secondary agglomerates within a microsecond time window of 10ms to 15ms. Since this residence time is lower than the kinetic energy accumulation period required for the crack propagation of quartz raw sand, this scheme maintains the mechanical integrity of raw sand particles while removing the agglomeration state of molding sand, and avoids the generation of dead clay ash.

[0022] 3. Establish a deep collaborative system of material flow and energy flow to achieve self-healing in the processing process. Through the pneumatic coupling of the physical state detection probe inside the temporary storage unit and the downstream exhaust valve, the molding back pressure, which was originally a waste energy emission, is transformed into the execution power of reflux control. When the compaction rate or permeability parameters of the molding sand deviate from the benchmark range, the system no longer relies on external mechanical mixing equipment, but synchronously drives the flow guiding pneumatic valve to guide the deteriorated molding sand through the throat section for secondary screening by using airflow carrying kinetic energy. This method of combining molding cycle with closed-loop control of sand processing enables the system to have real-time compensation capability for losses caused by long-distance transportation or static agglomeration, ensuring high convergence of the physical performance indicators of molding sand under continuous production conditions. Attached Figure Description

[0023] Figure 1 This is a flow chart of the molding sand preloading and pneumatic depolymerization filtration process of the present invention;

[0024] Figure 2 This is a hardware topology diagram of the intelligent casting island sand processing control of the present invention. Detailed Implementation

[0025] The technical solutions of the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application are within the scope of protection of this application.

[0026] It should be noted that all directional and positional terms used in this invention, such as: up, down, left, right, front, back, vertical, horizontal, inner, outer, top, low, lateral, longitudinal, center, etc., are only used to explain the relative positional relationship and connection between components in a specific state (as shown in the accompanying drawings). They are only for the convenience of describing this invention and do not require that this invention be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention. In addition, the descriptions of "first," "second," etc., in this invention are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly indicating the number of technical features indicated.

[0027] In the description of this invention, unless otherwise explicitly specified and limited, the terms installation, connection, and linking should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections; they can refer to direct connections or indirect connections through an intermediate medium; they can refer to the internal connection of two components. For those skilled in the art, the specific meaning of the above terms in this invention can be understood according to the specific circumstances.

[0028] In the description of this specification, references to the terms "an embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example, and the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0029] A filtration process for foundry sand treatment includes the following steps:

[0030] Step S1: The process control unit reads the molding tasks in the task queue and obtains the surface roughness requirements of the mold, the delay constant of the conveying pipeline from the sand mixer to the molding sand storage bin, and the residual volume of the previous batch of molding sand in the conveying pipeline corresponding to the molding task.

[0031] Step S2: Based on the surface roughness requirements of the mold, determine the particle size distribution index of the target molding sand and the corresponding molding sand compaction rate benchmark range and molding sand permeability benchmark range. Calculate the preloading advance amount based on the delay constant of the conveying pipeline and the residual volume of the previous batch of molding sand. At the preloading advance amount node before the start of the molding task, drive the sand flow distribution valve to guide the molding sand output from the sand mixer to a filter path with corresponding filter aperture, and load molding sand that meets the particle size distribution index into the molding sand temporary storage bin.

[0032] Step S3: The compaction rate and air permeability of the molding sand in the molding sand storage chamber are measured by a physical state detection probe. When the compaction rate deviates from the benchmark range of molding sand compaction rate or the air permeability deviates from the benchmark range of molding sand air permeability, the pneumatic branch between the bottom return port of the molding sand storage chamber and the sand injection exhaust valve of the downstream molding machine is opened, and the high-pressure exhaust pulse of 0.5MPa to 0.7MPa generated by the downstream molding machine is introduced into the asymmetric venturi injector.

[0033] Step S4: Using the pneumatic shear force generated by the high-pressure exhaust pulse in the throat section of the asymmetric Venturi injector, deteriorated molding sand in the molding sand storage chamber is sucked in. The residence time of the molding sand in the throat section is controlled to be 10ms to 15ms. This is to peel off the bentonite hydration film on the surface of the molding sand while ensuring that the kinetic energy of the raw quartz sand is lower than its mechanical crushing threshold. After deagglomeration, the molding sand is introduced into the expansion section for deceleration and sprayed into the filtration path.

[0034] Preferably, step S2 includes: the process control unit extracts the minimum draft angle and the length-to-diameter ratio of the cavity depth hole for the molding task; when the minimum draft angle is lower than the preset critical value and the length-to-diameter ratio of the cavity depth hole is higher than the preset threshold, the maximum allowable impurity particle size in the particle size distribution index is reduced, and the bypass backfill pipeline is opened to replenish fine sand with a mesh size higher than the preset value to the molding sand temporary storage bin.

[0035] Preferably, step S3 includes: the process control unit determines a shear compensation coefficient based on the difference between the measured compaction rate and the benchmark range of the molding sand compaction rate, and adjusts the throat flow cross-sectional area of ​​the asymmetric Venturi injector according to the shear compensation coefficient.

[0036] Preferably, the cone angle of the reduced diameter section of the asymmetric venturi injector is 15° to 22°, the cone angle of the expanded diameter section is 4° to 6°, and the effective length of the throat section is 30mm to 50mm.

[0037] Preferably, step S2 further includes: during the transition period of molding sand type switching after the sand flow distribution valve is reversed, opening the mixing and unloading valve at the inlet end of the molding sand temporary storage bin to discharge the mixed sand material formed by mixing molding sand with different particle size indexes in the conveying pipeline into the waste sand recycling stream.

[0038] Preferably, step S4 further includes: utilizing the difference in mass density between the raw quartz sand and the stripped dust, the dust is discharged from the molding sand storage bin at the end of the expansion section via a pneumatic diversion interface.

[0039] Preferably, the inner wall of the asymmetric Venturi injector is provided with an anti-wear liner, and the surface of the anti-wear liner has a micro-rough structure that induces boundary layer turbulence, which is used to enhance the mechanical stripping effect of pneumatic shear force on the surface of sand particles.

[0040] Preferably, step S4 further includes: recording the settling time of the current batch of molding sand in the molding sand temporary storage bin, extracting the time compensation coefficient based on the settling time and adding it to the reflux ratio calculation model, so that molding sand with a settling time exceeding the rest threshold is discharged through the reflux port.

[0041] Preferably, the filtration process is integrated into the intelligent casting island, and the central control system of the intelligent casting island monitors the exhaust pressure waveform of the downstream molding machine and corrects the delay constant of the delivery pipeline online accordingly.

[0042] Example 1: In a smart foundry island scenario where production switches between thin-walled complex castings for aero-engines and large castings for general machinery, this process addresses quality fluctuations caused by delays in long-distance physical pipeline transport. When the production task switches from ordinary casting tasks with lower requirements for molding sand impurity particle size to high-precision casting tasks with extremely high requirements for surface roughness, the time delay between the filtration station and the downstream molding machine can be as long as... The delivery pipeline is still filled with coarse-grained molding sand left over from previous tasks. This phase mismatch between the molding sand supply and the current task requirements, caused by the physical pipeline length, results in the molding sand particle size distribution supplied to the molding machine failing to meet the surface quality requirements of the current high-precision mold. Therefore, the process control unit reads the molding tasks in the task queue, obtains the mold surface roughness requirements corresponding to each task, the delay constant of the delivery pipeline from the sand mixer to the molding sand storage bin, and the residual volume of the previous batch of molding sand in the pipeline. Based on the mold surface roughness requirements, the process control unit determines the target molding sand particle size distribution index and calculates the preloading advance based on the delivery pipeline delay constant and the residual volume of the previous batch of molding sand. When the preloading advance node is reached before the current molding task is completed, the process control unit drives the sand distribution valve to guide the molding sand output from the sand mixer to a filter path with corresponding filter pore sizes, preloading the molding sand in the molding sand storage bin located upstream of the molding machine to meet the particle size distribution index. The preloading advance of molding sand is represented in the process control unit as the early trigger time node before the end of the current molding task. Its basic calculation model is determined by the linear superposition of the delay constant of the conveying pipeline and the additional delay caused by the residual volume of the previous batch of molding sand. During the calculation, the residual volume is divided by the theoretical full volume of the conveying pipeline to determine the proportion of residual material, and this proportion is used as a weighting coefficient to multiply by the delay constant to obtain the residual material delay increment. Finally, the delay constant, the residual material delay increment and the physical response time of the sand flow distribution valve are accumulated to obtain the total value of the preloading advance time for the system to perform feedforward switching control. The phase decoupling effect of the temporary storage unit is used to cut off the rigid physical coupling between the upstream filter and the downstream molding, ensuring that the molding machine can immediately obtain the molding sand batch with the matching physical state when performing high-precision tasks. The process control unit has a preset logical mapping matrix of surface roughness and particle size distribution. When the surface roughness requirement of the mold corresponding to the molding task is roughness When the particle size distribution is in the range of 6.3μm to 12.5μm, the process control unit determines the particle size distribution index of the target molding sand as the average particle diameter. In the range of coarse sand from 0.35 mm to 0.45 mm; when roughness requirements are met. When the particle size distribution is in the range of 1.6μm to 3.2μm, the average particle diameter is used as the index for determining the particle size distribution of the target molding sand. The fine sand range of 0.18mm to 0.25mm is used as a benchmark for driving the sand flow distribution valve to switch and select a specific filtration path.

[0043] To address the pseudo-secondary agglomeration phenomenon caused by moisture migration from the bentonite hydration film after wet molding sand has remained in the molding sand storage chamber for more than 30 minutes, this solution establishes a pneumatic branch between the bottom return port of the molding sand storage chamber and the sand injection exhaust valve of the downstream molding machine. Based on the principle of microwave attenuation in porous media and Darcy's law of permeability, the physical state detection probe includes a microwave sensor array and a differential pressure transmitter. The system uses the microwave sensor array to measure the phase shift after microwave penetration of the local molding sand layer in the storage chamber to obtain the dielectric constant. Combined with the flow resistance pressure drop gradient after injecting calibration airflow into the probe sampling cavity, the compaction rate and permeability measurements are calculated using a pre-set binary nonlinear regression model in the process control unit. This binary nonlinear regression model consists of two sets of empirically coupled polynomials with defined dimensions. The system substitutes the microwave dielectric constant as an independent principal term into the first-order characteristic equation to directly model the moisture content and the corresponding compaction rate trend. The binary nonlinear regression model is used to calculate the compaction rate measurement. The characteristic equation is ,in The measured microwave dielectric constant, and This is a fixed floating-point constant; while it is used to calculate the air permeability measurement value. The characteristic equation is: In the formula The flow resistance pressure drop gradient after injecting calibration gas into the probe sampling cavity. These constitute the cross-resistance parameters representing pore unobstructedness. and These are the solidified binary fitting coefficients. Through the collaborative operation of the characteristic equation, a deterministic physical state detection scalar is directly output. Simultaneously, the measured value of the flow resistance pressure drop gradient is multiplied by the reciprocal of the square term of the dielectric constant to construct a cross-resistance parameter representing pore flow permeability to characterize air permeability. The weight coefficients of the independent variables in the above two equations are all fitted by least squares using more than 100 sets of standard sand samples with known temperature and humidity conditions before the equipment leaves the factory, and are solidified in the control unit memory as floating-point constants. In response to the transient low gas volume characteristics of the exhaust pulse and the accompanying solid phase impurities, a multi-stage cyclone separator and a pressure-stabilized gas storage tank are connected in series in the pneumatic branch. The downstream molding machine generates multiple batches of transient exhaust pulses, which are introduced into the multi-stage cyclone separator to remove suspended dead clay and water vapor. After purification, the high-pressure gas enters the pressure-stabilized gas storage tank to complete energy accumulation and time broadening, and is continuously output to the asymmetric Venturi injector. To stabilize airflow, the pressure-stabilizing gas storage tank incorporates a damping flow field network based on multi-layer microporous throttling plates. Its core function is to volumetrically expand and lock in the discontinuous pneumatic waste energy discharged from the upstream molding machine at high frequencies of tens of milliseconds. When the internally sensed accumulated absolute pressure exceeds the 0.6MPa process limit, this structure utilizes the constant flow resistance attenuation effect of the throttling plate matrix to forcibly smooth the transient peaks and troughs of the upstream, transforming the intermittent sharp pulses into a smooth, wide-pulse static pressure source that can be continuously maintained for several seconds on the time axis. This overcomes the physical transient blockage and provides a seamless, stable, and continuous airflow energy for the downstream venturi tube. The physical state detection probe measures the compaction rate and permeability of the molding sand in the molding sand storage chamber. When the measured values ​​exceed the reference physical range, the process control unit drives the diversion pneumatic valve to reduce the pressure generated by the downstream molding machine during sand shooting from 0.5MPa to 0.A transient high-pressure exhaust pulse of 7 MPa is introduced into the asymmetric Venturi ejector. This high-pressure exhaust pulse is compressed in the narrowing section with a cone angle of 15° to 22°, and generates local negative pressure in the throat section with an effective length of 30 mm to 50 mm. This negative pressure draws in deteriorated agglomerated molding sand from the molding sand storage chamber. The time gradient generated by the high-speed airflow tears the hydration film on the surface of the molding sand particles, constraining the residence time of the molding sand in the throat section to a window of 10 ms to 15 ms. Since this residence time exceeds the time threshold of the bentonite shear thinning response and is lower than the kinetic energy accumulation period required for crack propagation in the original quartz sand, the molding sand, after deagglomeration, enters the widening section with a cone angle of 4° to 6° for deceleration, and is then injected into the filtration path in the form of a gas-solid two-phase discrete flow to complete secondary interception, maintaining the mechanical integrity of the original sand particles. Under the premise of restoring the physical activity of molding sand, after the macroscopic pressure field accelerates in the narrowing section, a strong microscopic airflow shear layer is formed in the throat section. When the molding sand particles pass through this shear layer, the velocity difference between the gas and solid phases forms a high-frequency boundary layer peeling force on the particle surface. This force directly acts on the thixotropic bentonite hydration film on the periphery, causing its apparent viscosity to drop instantaneously and undergo yielding rheology. At the same time, the extreme residence time at the microsecond level cuts off the energy chain that continuously transfers macroscopic kinetic energy to the microscopic lattice, making the energy peak value transferred to the internal quartz raw sand by physical collision much lower than the critical fracture stress for the expansion of its internal defects. This achieves cross-scale self-consistency of microscopic peeling and physical damage prevention mechanism. According to the non-Newtonian fluid shear thinning rheology model, the physical tearing strength of the molding sand pseudo-agglomerates directly depends on the jet velocity of the flow field, and the process control unit adopts the relationship. Real-time calculation of shear compensation coefficient, where, Represents the dimensionless shear compensation coefficient. This represents the actual compaction rate measurement value collected by the physical state detection probe. This represents the upper limit threshold of the benchmark range for the compaction rate of molding sand corresponding to the molding task to be performed. The rheological sensitivity factor was determined by a pre-flow step calibration experiment, with a value range limited to 0.12 to 0.18. An annular hydraulic chamber was coaxially fitted outside the throat section of the asymmetric venturi injector, with its inner wall made of elastic polyurethane material. When the process control unit determined that the actual compaction rate exceeded the reference range, it based on the calculated... A corresponding control bias voltage is output to the proportional servo valve of the hydraulic branch, driving the hydraulic source to pressurize and inject incompressible fluid medium into the annular hydraulic chamber. This causes the inner wall of the elastic polyurethane to undergo controlled radial contraction deformation, reducing the throat flow cross-sectional area and increasing the jet shear force at the physical boundary. To support the long-term safe execution of the above radial contraction deformation in a high-pressure abrasive flow environment, the inner wall of the elastic polyurethane adopts a multi-layer composite damping structure. Its outer layer is covered with a heavy-duty wear-resistant matrix with a Shore hardness of 95A, and micron-level liquid storage pits are densely distributed on the surface of the inner flow channel. When the high-speed gas-solid two-phase flow passes through, the residual water vapor carried by the airflow is thrown to the wall surface by centrifugal force and captured by the pit array, spontaneously forming a fully covered gas-liquid boundary slip layer. This dynamic liquid film is used to buffer and dissipate the instantaneous high temperature and shear stress generated by high-speed mechanical friction, thereby effectively avoiding direct hard wear of the wall surface by the solid medium while withstanding high-frequency compression deformation.

[0044] Example 2: Equipped with a pipeline of 50m length and a capacity of... In the physical test platform of the molding sand storage silo and the sand mixing unit, the test group verified the phenomenon of errors in molding sand particle size distribution caused by production task switching. The test data came from an online particle size sensor integrated at the end of the pipeline. The sampling frequency of this sensor was set to 100Hz. The selection of the sampling frequency balanced capturing 10ms-level transient changes in the flow field with reducing the computational load on the process control unit. The signal source was superimposed with Gaussian white noise with a signal-to-noise ratio of 20dB and 50Hz power frequency interference. The test group obtained the mold surface roughness requirements, delay constant, and residual volume of the previous batch of molding sand corresponding to the production task. ,in, To determine the volume of molding sand remaining in the conveying pipeline after the previous production task, the control group 1 used a fixed preloading advance of 240s without dynamic correction based on the residual volume. The experimental group used the process control unit to output dynamic preloading advance commands. The measured results showed that in the first 5 molds produced after the production task switch, the molding sand particle size of the control group 1 was... The average deviation between the measured values ​​and the target indicators was 28.6%, of which The particle diameter corresponds to a cumulative distribution percentage of 50%, while the experimental group maintained the correction of the dynamic preloading advance mechanism under noise interference, resulting in molding sand particle size. The average deviation converged to within 3.2%, and this data difference proves that the preloading mechanism of feedforward calculation can offset the quality misalignment caused by the delivery delay of physical pipelines.

[0045] To address the degradation of activity in wet molding sand with a residence time exceeding 30 minutes, the experimental group used a physical state detection probe to monitor the molding sand parameters in the temporary storage chamber in real time and obtain the initial permeability measurement value. The compaction rate was measured at 53.4%. The process control unit drove the pneumatic valve to direct the 0.62MPa high-pressure exhaust pulse emitted by the molding machine during sand injection to the asymmetric Venturi ejector. In contrast, in sample group two, the asymmetric Venturi ejector was removed, and the conventional gravity discharge method was maintained. The experimental group controlled the residence time of the molding sand in the throat section to be 12.5ms. The kinetic energy gradient generated by the high-speed airflow tore the bentonite hydration film on the surface of the molding sand particles. The measured data showed that the air permeability measurement value of sample group two remained constant after passing through the filtration path, while in the experimental group, under the action of the exhaust pulse, the compaction rate measurement value of the molding sand converged to 41.8%, and the air permeability measurement value rebounded to This repair effect, derived from the energy conversion of back pressure during molding, allows deteriorated molding sand particles to regain physical activity before secondary interception. In the actual operating conditions of the process control unit adjusting the flow-guiding pneumatic valve, if the residence time is compressed to less than 10ms, the high-speed airflow does not provide sufficient energy input for the boundary layer shearing and peeling of pseudo-agglomerates, and the bentonite hydration film cannot undergo sufficient yielding rheology, resulting in a significant deterioration of the in-situ activation effect. If the residence time is extended to more than 15ms, the quartz sand particles undergo high-frequency excessive mechanical collisions inside the throat section of the flow field, and the integral value of mechanical kinetic energy exceeds the critical fracture stress for the expansion of internal defects in the material, leading to a large amount of sand breakage and the generation of harmful dead clay ash. Therefore, strictly limiting the residence time to the range of 10ms to 15ms is the process boundary to ensure the deagglomeration efficiency of the flow field without causing mechanical damage.

[0046] To define the nonlinear influence of residence time in the throat section on the integrity of the original sand, a gradient verification system with residence times of 8.5 ms, 13.2 ms, and 24.8 ms was constructed. The state of the treated samples was analyzed using a high-resolution electron microscope. When the residence time was at the lower limit of 8.5 ms, the compaction rate decreased by only 1.5%, indicating that the shear thinning response of the bentonite hydration film had not yet fully started. When the residence time was at the median of 13.2 ms, the sand activity recovery efficiency reached 98.2%. The raw sand breakage rate remained below 0.5%. As the residence time increased to 24.8 ms, the fine powder content in the sample increased from the initial 1.1% to 9.4%, and the mass average diameter of the raw sand decreased from 285 μm to 242 μm. This raw sand breakage state indicates that shearing induced fatigue damage to the quartz crystal framework. This performance degradation point confirms that limiting the residence time to the 10 ms to 15 ms range can balance deagglomeration efficiency and raw sand damage, thereby ensuring the stability of the filtration process while maintaining the raw sand angularity index. The kinetic energy accumulation period for fatigue cracking of a quartz crystal framework is physically calculated based on the premise of the Griffith failure criterion in fracture mechanics. Using the measured lower limit of the elastic modulus of a single quartz grain with a known crystal form and the material's compressive strength, the upper limit of the critical fracture mechanical energy that prevents brittle collapse is determined. This fixed mechanical constant is then divided by the integral parameter of the mechanical kinetic energy input from direct gas-solid impact per unit time within a pre-set 0.6 MPa Venturi flow field. This theoretically proves the critical period boundary for crack initiation. The theoretical duration supports the safety margin of extreme dwell time calibration. Within the dwell time of 10ms to 15ms defined in this invention, although the nanosecond-level transient stress wave propagation and lattice stress redistribution have been completed inside the quartz raw sand skeleton, this millisecond-level time window is still much lower than the dynamic crack initiation cycle required for the unsteady propagation of fatigue cracks in quartz crystals. Thus, the cumulative chain of kinetic energy conversion to fracture surface energy caused by long-term continuous gas-solid collision is macroscopically cut off, allowing the raw sand to maintain the integrity of the skeleton while withstanding the peeling of the surface hydration film.

[0047] Example 3: In the intelligent casting island process for producing complex aerospace-grade aluminum alloy pump casings, the effective cross-sectional area of ​​the inner wall of the conveying pipeline dynamically shrinks due to the adhesion of wet molding sand. This causes a deviation between the pre-set pipeline delay constant and the actual physical conveying time. When the accumulated sand thickness on the pipe wall reaches 5mm to 8mm, the preloading advance calculated by the fixed parameter model lags behind the consumption rhythm of the molding machine, causing the molding sand level in the molding sand storage bin to fall below the safety threshold, resulting in an unplanned shutdown of the molding production line. To eliminate the timing discrepancy caused by pipeline model drift, the process control unit initiates the in-situ calibration procedure. Utilizing the no-load reset stroke of the molding machine during the production task switching interval, the process control unit injects a 2-second pulse sand flow into the output end of the sand mixer. Simultaneously, the varistor probe installed at the inlet of the molding sand storage bin is activated. The time difference between the pulse sand flow entering the pipeline from the sand flow distribution valve and reaching the detection point of the varistor probe is recorded, and this time difference is determined as the real-time pipeline delay constant. The process control unit compares With initial delay constant The deviation rate is used to correct the preload advance. , The calculation formula is as follows: ,in, This is the corrected preload lead time. This is the measured real-time pipeline delay constant. The residual volume of molding sand from the previous batch is obtained by integrating the data from the flow meter at the end of the pipeline. This is the theoretical total volume of the pipeline. The physical action response time of the sand flow distribution valve.

[0048] In response to task switching with different surface quality requirements, the process control unit executes the scheduling logic of the filtering path, which reads the preset surface roughness requirements of the mold in the task to be molded. The value is mapped to a three-level filtering matrix when the roughness requirement is met. When the roughness is in the range of 6.3μm to 12.5μm, the process control unit drives the sand flow distribution valve to switch to the primary filtration path with an pore size of 0.5mm to 0.8mm; when the roughness requirement is... When the particle size is in the range of 1.6μm to 3.2μm, the process control unit activates the secondary filtration path, using a fine-mesh screen with an aperture of 0.2mm to 0.4mm. The throat section length of the asymmetric venturi injector... Cone angle of the reduced diameter section Satisfying pneumatic shear constraints, when the high-pressure exhaust pulse pressure When set to 0.65MPa, the cone angle of the reduced diameter section Selected as 18° and larynx segment length The selected diameter is 42mm. This geometric configuration ensures that the static pressure drop value formed by the exhaust pulse at the central axis of the throat section is not less than 0.08MPa. The generated kinetic energy breaks the pseudo-agglomerates of molding sand with a diameter greater than 2mm into discrete particles with a particle size of less than 0.3mm. At the same time, the maximum shear stress generated is maintained below 30% of the compressive strength of the original quartz sand.

[0049] During steady-state operation of the production cycle, the process control unit completes the sand flow path switching synchronization process, which establishes the output flow rate of the sand mixer. Current liquid level in the molding sand temporary storage bin The linkage model uses a weighing sensor installed at the outlet of the sand mixer to obtain the instantaneous flow rate of molding sand, and the process control unit determines the volume of molding sand required for a single cycle of the molding machine. And the current styling rhythm layer for the styling task. Calculate the sand flow demand rate When the particle size distribution index corresponding to the next task in the task queue changes, the process control unit calculates the remaining volume of the molding sand temporary storage bin. ,in, The full volume of the molding sand temporary storage silo. Let be the cross-sectional area of ​​the molding sand temporary storage bin. If the batch volume is smaller than the preload volume required for the next task, the process control unit delays the output of the sand flow distribution valve switching command until the current molding task consumes part of the stock. The safe fill threshold has been reached.

[0050] Example 4: During the initial calibration of a newly installed system, the process control unit initiates the Venturi flow field characteristic measurement program. By injecting pressure pulses into the asymmetric Venturi injector, pressure sensors located at both ends of the throat section are used to collect the pressure difference change curves, and the gas flow rate corresponding to the high-pressure exhaust pulse pressure stepping from 0.4 MPa to 0.8 MPa is recorded. And based on the effective length of the tracheal segment Calculate the measured residence time. For molding sands of different densities, the process control unit adjusts the transient airflow by regulating the opening of the induced flow pneumatic valve to establish pressure. Duration of stay The compensation model enables the process control unit to calculate valve action commands that meet the dwell time requirements of 10ms to 15ms based on the physical parameter offset under production conditions.

[0051] When the system faces the situation of changing the quartz raw sand or changing the bentonite ratio, the process control unit initiates the reference physical zone initialization procedure, guiding the standard state molding sand produced by the sand mixer into the molding sand temporary storage bin. Ten sets of compaction rate and permeability measurements of the molding sand are continuously collected by the physical state detection probe. The average value of the measurements is calculated and determined as the physical reference center point. Based on the surface roughness requirements of the mold corresponding to the current molding task... A 5% tolerance bandwidth is set to generate a benchmark range for molding sand compaction rate and a benchmark range for molding sand permeability. These benchmark ranges are then stored in the memory of the process control unit as logical judgment thresholds for subsequently triggering high-pressure exhaust pulses to restore the activity of the molding sand.

[0052] The embodiments of this application have been described above with reference to the accompanying drawings. Unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other. This application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit of this application and the scope of protection of this invention, and all of these forms are within the protection scope of this application.

Claims

1. A filtration process for foundry sand treatment, characterized in that, Includes the following steps: Step S1: The process control unit reads the molding tasks in the task queue and obtains the surface roughness requirements of the mold, the delay constant of the conveying pipeline from the sand mixer to the molding sand storage bin, and the residual volume of the previous batch of molding sand in the conveying pipeline corresponding to the molding task. Step S2: Based on the surface roughness requirements of the mold, determine the particle size distribution index of the target molding sand and the corresponding molding sand compaction rate benchmark range and molding sand permeability benchmark range. Calculate the preloading advance amount based on the delay constant of the conveying pipeline and the residual volume of the previous batch of molding sand. At the preloading advance amount node before the molding task starts, drive the sand flow distribution valve to guide the molding sand output from the sand mixer to a filter path with corresponding filter aperture, and load molding sand that meets the particle size distribution index into the molding sand temporary storage bin. Step S3: The compaction rate and permeability of the molding sand in the molding sand storage chamber are measured by a physical state detection probe. When the compaction rate deviates from the benchmark range of molding sand compaction rate or the permeability deviates from the benchmark range of molding sand permeability, the pneumatic branch between the bottom return port of the molding sand storage chamber and the sand injection exhaust valve of the downstream molding machine is opened, and the high-pressure exhaust pulse of 0.5MPa to 0.7MPa generated by the downstream molding machine is introduced into the asymmetric venturi injector. Step S4: Using the pneumatic shear force generated by the high-pressure exhaust pulse in the throat section of the asymmetric Venturi injector, deteriorated molding sand in the molding sand storage chamber is sucked in. The residence time of the molding sand in the throat section is controlled to be 10ms to 15ms. This is to peel off the bentonite hydration film on the surface of the molding sand while ensuring that the kinetic energy of the raw quartz sand is lower than its mechanical crushing threshold. After deagglomeration, the molding sand is introduced into the expansion section for deceleration and sprayed into the filtration path.

2. The filtration process for foundry sand treatment according to claim 1, characterized in that, Step S2 includes: the process control unit extracts the minimum draft angle and the length-to-diameter ratio of the cavity depth hole of the molding task. When the minimum draft angle is lower than the preset critical value and the length-to-diameter ratio of the cavity depth hole is higher than the preset threshold, the maximum allowable impurity particle size in the particle size distribution index is reduced, and the bypass back-mixing pipeline is opened to replenish fine sand with a mesh size higher than the preset value to the molding sand temporary storage bin.

3. The filtration process for foundry sand treatment according to claim 1, characterized in that, Step S3 includes: the process control unit determines the shear compensation coefficient based on the difference between the measured compaction rate and the benchmark range of the molding sand compaction rate, and adjusts the throat flow cross-sectional area of ​​the asymmetric Venturi injector according to the shear compensation coefficient.

4. The filtration process for foundry sand treatment according to claim 1, characterized in that, The cone angle of the reduced diameter section of the asymmetric Venturi injector is 15° to 22°, the cone angle of the expanded diameter section is 4° to 6°, and the effective length of the throat section is 30mm to 50mm.

5. A filtration process for foundry sand treatment according to claim 1, characterized in that, Step S2 also includes: during the transition period of molding sand type switching after the sand flow distribution valve is reversed, opening the mixing and unloading valve at the inlet of the molding sand temporary storage bin to discharge the mixed sand material formed by mixing molding sand with different particle size indices in the conveying pipeline into the waste sand recycling stream.

6. A filtration process for foundry sand treatment according to claim 1, characterized in that, Step S4 also includes: utilizing the difference in mass density between the raw quartz sand and the stripped dust, the dust is discharged from the molding sand storage bin at the end of the expansion section through a pneumatic diversion interface.

7. A filtration process for foundry sand treatment according to claim 4, characterized in that, The inner wall of the asymmetric venturi ejector is equipped with an anti-wear liner. The surface of the anti-wear liner has a micro-rough structure that induces boundary layer turbulence, which is used to enhance the mechanical stripping effect of aerodynamic shear force on the surface of sand particles.

8. A filtration process for foundry sand treatment according to claim 1, characterized in that, Step S4 also includes: recording the settling time of the current batch of molding sand in the molding sand temporary storage bin, extracting the time compensation coefficient based on the settling time and adding it to the reflux ratio calculation model, so that molding sand with a settling time exceeding the rest threshold is discharged through the reflux port.

9. A filtration process for foundry sand treatment according to claim 1, characterized in that, The filtration process is integrated into the intelligent casting island. The central control system of the intelligent casting island monitors the exhaust pressure waveform of the downstream molding machine and corrects the delay constant of the delivery pipeline online accordingly.

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