Multi-stage composite sand removal method and system for investment casting of casting with narrow and small inner cavity

Abstract

The invention discloses a multi-stage composite sand cleaning method and system for investment casting of a narrow inner cavity casting, and relates to the technical field of investment casting, the method comprises the following steps: S1, primary shot blasting cleaning is carried out to remove floating sand on the outer surface of the casting and a shallow inner cavity, and a deep sand inlet is exposed; s2, inner cavity impact sand loosening is conducted, specifically, a sand body blocked in the deep portion of the inner cavity of the casting cracks and loosens through pneumatic impact; s3, ultrasonic vibration sand removal is conducted, specifically, the casting is installed on a special tool, loose sand grains are stripped from the inner cavity wall through ultrasonic vibration output by an ultrasonic generation unit, and a tuning control module is arranged to conduct real-time scanning on the casting and adjust the frequency of the ultrasonic vibration so as to be matched with the local resonance frequency of the inner cavity of the casting; s4, secondary shot blasting finishing is conducted, falling residual sand in the casting is removed, and surface finishing is achieved; and efficient, thorough and damage-free sand removal of sand grains in narrow, bent and deep inner cavities of the casting is realized through the multi-stage sand removal step.

Description

Technical Field

[0001] This invention relates to the field of investment casting technology, and in particular to a multi-stage composite sand removal method and system for investment casting of narrow-cavity castings. Background Technology

[0002] Investment casting, due to its ability to replicate the complex structure of wax patterns and achieve high dimensional accuracy and good surface quality, is widely used in the manufacturing of metal parts with complex three-dimensional structures, such as aero-engine blades, fuel nozzles, and precision medical components. With the development of high-performance equipment, more and more castings are designed with internal features such as micro-flow channels, deep cavities, curved intersecting holes, and narrow, long blind holes to meet performance requirements such as lightweighting, drag reduction, and enhanced heat transfer. However, these internal cavities often form shell structures with high aspect ratios, multiple bends, and multiple nodes during investment casting. After pouring and cooling, shell material (molding sand, ceramic shell fragments, etc.) is easily left inside, and the residue is often hidden, has high consolidation strength, and is extremely difficult to clean.

[0003] Currently, the commonly used sand removal technologies in the industry each have their limitations. Mechanical shot blasting relies on the impact of high-speed shot to remove sand. Although it is suitable for removing sand from external surfaces, it is difficult to get the shot into narrow, deep cavities, and the shot cannot form an effective flow field in complex internal cavities, resulting in the inability to impact and remove deep molding sand. At the same time, during shot blasting, the shot is prone to accumulate at the orifice or even blockage, which hinders subsequent cleaning. High-pressure water jet or air jet cleaning relies on the straight-line transmission of energy by the jet. It is effective for straight holes, but when there are bends, dead corners, and multi-node internal cavities, a "shadow effect" will occur, and the jet pressure cannot cover the entire area. In addition, water jet may cause metal surface corrosion problems.

[0004] Chemical sand removal methods, such as alkaline blasting and acid washing, can dissolve some ceramic shell materials, but they suffer from problems such as long processes, restricted emissions, severe pollution, and high treatment costs. For commonly used high-alumina, mullite, and corundum high-strength refractory materials, the efficiency of chemical sand removal methods is significantly reduced, and the internal residues are often "difficult to blast and dissolve." In addition, chemical sand removal makes it difficult to control the reaction location locally, which can easily cause over-corrosion of thin-walled cavities. Manual cleaning is still used in many enterprises, usually using tools such as steel needles, electric drills, and pneumatic picks to perform point operations on difficult-to-clean areas. However, it is labor-intensive, extremely inefficient, and can easily scratch or even penetrate thin-walled castings. It is also difficult to guarantee the consistency and repeatability of cleaning, making it unsuitable for the needs of mass production.

[0005] With the increasing complexity of investment casting structures and the improvement of refractory material performance, single physical or chemical methods are no longer sufficient to thoroughly clean sand from narrow and deep cavities. Therefore, the industry has begun to explore multi-step combined sand cleaning processes. However, most existing solutions are simply a combination of different equipment, lacking energy transfer path design tailored to the structural characteristics of deep cavities, and failing to achieve coordinated control of processes such as crushing, loosening, peeling, and discharge. As a result, it remains difficult to solve core problems such as deep sand blockage, residual sand at cross-cavity nodes, and non-destructive protection of the inner wall.

[0006] In summary, the existing technology has at least the following technical problems: Existing sand removal methods are inefficient and cannot completely remove deep molding sand. Some sand removal methods also have technical problems such as causing mechanical damage, corrosion or secondary blockage to thin walls or delicate internal cavities. Summary of the Invention

[0007] The purpose of this invention is to provide a multi-stage composite sand removal method and system for investment casting with narrow internal cavities, in order to solve the technical problems that existing sand removal methods are difficult to completely remove deep molding sand and have low efficiency, and that some sand removal methods also cause mechanical damage, corrosion or secondary blockage to thin walls or fine internal cavities.

[0008] The preferred technical solutions among the many technical solutions provided by this invention can produce a variety of technical effects, which are described in detail below.

[0009] To solve the above-mentioned technical problems, the present invention provides the following technical solution: This invention provides a multi-stage composite sand removal method for investment casting with narrow internal cavities, comprising the following sequential steps: S1, initial shot blasting: after investment casting, the casting is cut out and placed in a crawler-type shot blasting machine. High-speed shot is used to impact the outer surface, orifices, and shallow internal cavities of the casting to remove floating sand and oxide scale, thereby exposing the internal cavity structure of the casting and providing a channel for subsequent impact of deep clogging sand; S2, Internal cavity impact loosening: Using pneumatic impact equipment, the narrow and curved internal cavity of the casting after step S1 is subjected to high-frequency mechanical impact, causing the blocked molding sand to crack and loosen. S3. Ultrasonic vibration sand removal: The casting after step S2 is clamped on a special tooling connected to an ultrasonic generator unit. The ultrasonic vibration emitted by the ultrasonic generator unit is transmitted to the casting, causing the loosened molding sand to peel off from the inner wall of the casting. S4. Secondary shot blasting finishing: The casting after step S3 is placed in the crawler shot blasting machine again to remove the loose residual sand and perform a surface finishing treatment on the casting. In step S3, the ultrasonic generating unit is equipped with an adaptive tuning control module for the internal cavity resonance frequency. The tuning control module adjusts or selects the ultrasonic vibration frequency of the scanning frequency band in real time during the ultrasonic vibration of the ultrasonic generating unit, so that the ultrasonic vibration frequency is close to the resonance frequency of the internal cavity or local structure of the casting, thereby improving the peeling efficiency of deep sand particles in the casting.

[0010] In one embodiment, in step S2, the pneumatic impact device is a high-frequency air pick, and the impact needle of the high-frequency air pick is made of high-carbon steel or alloy steel, and is customized according to the internal cavity cross-sectional shape and size of the casting.

[0011] In one embodiment, in step S3, the ultrasonic vibration frequency of the ultrasonic generating unit is 20kHz to 40kHz, the output power is 200W to 2000W, and the ultrasonic vibration treatment time of the casting on the special tooling is 3-15 minutes.

[0012] In one embodiment, in step S3, the special tooling is made of a metal material with high acoustic conduction efficiency. The structure of the special tooling matches the outer contour of the casting and is rigidly connected to the output end of the ultrasonic generating unit by bolts and an amplitude transformer, which is used to improve the efficiency of ultrasonic vibration energy transmission to the casting.

[0013] In one embodiment, the tuning control module includes a frequency scanning unit, which, when the ultrasonic generating unit begins the ultrasonic vibration desanding treatment of the casting, rapidly scans the casting at an ultrasonic vibration frequency in the 20kHz~40kHz band; a feedback detection unit, which detects the vibration response amplitude or energy absorption characteristics of the casting at different vibration frequencies and outputs the detection results; and a tuning control unit, which selects or locks the frequency corresponding to the maximum response based on the detection results of the feedback detection unit, as the working frequency for the ultrasonic generating unit to perform ultrasonic vibration desanding on the current casting.

[0014] A multi-stage composite sand removal system is also provided, including a tracked shot blasting unit for sequentially performing the primary shot blasting and secondary shot blasting finishing on the casting; a pneumatic impact subsystem, including an air compressor, pipelines, and the pneumatic impact device, for performing the internal cavity impact sand loosening step of the casting; and an ultrasonic sand removal subsystem, including the tuning control module, the ultrasonic generating unit, the amplitude transformer, and the special tooling, wherein the tuning control module controls the vibration of the ultrasonic generating unit, and the ultrasonic generating unit transmits the vibration through bolts to the amplitude transformer. The vibration is transmitted to the special tooling, which transmits the vibration to the casting for ultrasonic vibration desanding; and a control system for controlling the start-up, shutdown, parameter setting, and timing linkage between the tracked shot blasting unit, the pneumatic impact subsystem, and the ultrasonic sand cleaning subsystem; the control system dynamically adjusts or selects the ultrasonic vibration frequency of the ultrasonic generator unit during the ultrasonic vibration desanding process according to the tuning result output by the tuning control module, so that the ultrasonic vibration frequency is close to the local resonance frequency of the inner cavity of the casting.

[0015] In one embodiment, the feedback detection unit of the tuning control module includes a vibration response detection sensor or an energy absorption analysis unit, used to detect the vibration response amplitude or energy absorption characteristics of the casting at different frequencies, and feed the detection results back to the tuning control unit to form the tuning result, which is then fed back to the control system through the tuning control module.

[0016] In one embodiment, the amplitude transformer adopts a stepped structure or an exponentially gradual structure to enhance the coupling degree of the ultrasonic wave generating unit to the special tooling for transmitting ultrasonic vibration energy.

[0017] The beneficial effects of this invention are as follows: (1) The thoroughness of sand removal is significantly improved, solving the industry pain point of difficulty in removing deep molding sand. This invention employs a multi-stage composite mechanism of "shot blasting pre-cleaning + pneumatic arch breaking and sand loosening + ultrasonic resonance sand removal + re-shot blasting finishing," wherein: step S1 exposes the inner cavity entrance and shallow structure of the casting, solving the problem of "tools being unable to effectively enter deep holes" in traditional methods; step S2 uses high-frequency mechanical impact to cause the molding sand, which was originally a blockage in the deep inner cavity of the casting, to crack and loosen, creating a "weak bonding state" for subsequent steps; step S3 uses the high-frequency acceleration of ultrasonic vibration to generate strong inertial force for the loosened sand particles, thereby completely detaching them from the inner wall; finally, step S4 further removes the remaining free sand and smooths the surface of the inner cavity of the casting; through multi-stage synergistic action, it has a significant sand-cleaning effect, especially on the deep curved structure and blind hole area of ​​the casting, and can increase the deep sand particle removal rate to a level that is difficult to achieve with traditional methods.

[0018] (2) The efficiency of ultrasonic desanding in the deep cavity of castings is significantly improved by the “adaptive tuning of internal cavity resonance frequency” technology. The tuning control module added in step S3 of this invention can automatically match or lock an ultrasonic vibration frequency close to the local natural frequency of the casting based on the vibration response of the casting at different frequencies when the ultrasonic generating unit scans in the 20–40kHz frequency band. This allows the ultrasonic generating unit to maintain the matched ultrasonic vibration frequency in subsequent continuous ultrasonic vibration, thereby improving the ultrasonic vibration sand removal effect through the resonance amplification effect formed by the ultrasonic waves and the inner cavity. The control effect formed by the tuning control module also includes: a significant increase in the local amplitude of the deep inner cavity, making it easier to remove sand particles in curved cavities and variable cross-section cavities, and solving the technical bottleneck of "fast energy attenuation and no vibration in deep cavities" in fixed frequency ultrasound. Thus, it achieves the "precise sand removal in deep cavities" effect that is difficult to achieve with traditional ultrasound, greatly improving the peeling efficiency and sand removal speed.

[0019] (3) The sand removal process will not damage the thin-walled or delicate internal cavity structure. Compared with contact-type mechanical sand removal such as steel needles and drill bits, in this invention: the pneumatic impact only acts on the sand body and does not directly contact the inner wall; ultrasonic sand removal is a non-contact vibration energy transfer method that does not introduce hard impacts, and most of the force acts on the sand particles rather than the metal body; therefore, it can effectively avoid the phenomena of inner wall scratches, thin-wall perforation, cavity deformation and local damage to low-strength alloys that occur in traditional cleaning methods, and is particularly suitable for the sand removal process of precision nozzles, small channels and complex flow channels of castings.

[0020] (4) Improved sand removal efficiency, controllable process and suitable for automated industrial applications The multi-stage composite sand cleaning method adopts all controllable mechanical and ultrasonic physical processes, which can be executed sequentially by the control system. In automated operation, the overall sand cleaning process cycle is stable, achieving high sand cleaning consistency, integration with production lines to achieve automated and batch operation, and reducing dependence on manual skills. Compared with traditional manual cleaning, the sand cleaning efficiency and stability of the multi-stage composite sand cleaning method of this invention are significantly improved.

[0021] (5) Purely physical sand cleaning, with no risk of corrosion or chemical pollution, economical and environmentally friendly. The present invention eliminates the need for chemical sand cleaning methods such as acid washing and alkaline blasting, does not corrode the inner wall of the metal, leaves no corrosive media residue, requires no chemical waste liquid treatment, and significantly reduces environmental protection costs, meeting the requirements of green manufacturing. The overall process is superior to traditional chemical sand cleaning methods in terms of both environmental protection and economy.

[0022] In summary, this invention achieves a highly efficient, thorough, and non-destructive cleaning process for residual sand in narrow, curved, and deep cavities of castings through a multi-stage composite sand removal mechanism and an ultrasonic sand removal technology with adaptive tuning of the internal cavity resonance frequency. It overcomes the shortcomings of existing sand removal technologies, such as low efficiency, inability to efficiently remove deep sand from castings, easy damage to thin walls, and excessive environmental pollution. It is suitable for large-scale and automated production applications. Attached Figure Description

[0023] To more clearly illustrate the technical solution of the present invention, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of the steps of the multi-stage composite sand removal method of the present invention; Figure 2 This is a schematic diagram of the overall structure of the multi-stage composite sand cleaning system of the present invention; Figure 3 This is a schematic diagram of the device structure for the ultrasonic vibration sand removal step of the present invention.

[0025] The accompanying figure is labeled as follows: 1. Castings; 2. Specialized tooling; 3. Ultrasonic generating unit; 31. Ultrasonic generator; 32. Transducer; 4. Amplitude bar. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0027] The specific implementation provides a multi-stage composite sand removal method and system for investment casting with narrow internal cavities. The method includes: Step S1, initial shot blasting to remove floating sand from the outer surface and shallow internal cavity of the casting and expose deep sand inlets; Step S2, internal cavity impact loosening, using pneumatic impact to cause cracks and loosen the deep blocking sand inlets within the casting cavity; Step S3, ultrasonic vibration sand removal, where the casting is mounted on a special fixture, and ultrasonic vibration output from an ultrasonic generator unit peels the loosened sand particles from the internal cavity wall. A tuning control module is included to scan the casting in real time and adjust the frequency of ultrasonic vibration to match the local resonance frequency within the casting cavity; Step S4, secondary shot blasting finishing, removing loosened residual sand from the casting and achieving surface smoothing. This multi-stage sand removal process achieves efficient, thorough, and non-destructive sand removal for narrow, curved, and deep internal cavities of castings. It effectively solves the technical problems of existing sand removal methods, which are difficult to completely remove deep molding sand and have low efficiency, and some sand removal methods also cause mechanical damage, corrosion, or secondary blockage to thin walls or delicate internal cavities.

[0028] The first implementation of the multi-stage composite sand removal method is as follows: Figure 1 and Figure 3 As shown, the process includes the following sequential steps: S1, initial shot blasting: After investment casting, the casting 1 is cut out and placed in a crawler shot blasting machine. High-speed shot streams are used to impact the outer surface, orifices and shallow inner cavities of the casting 1 to remove floating sand and oxide scale, thereby exposing the inner cavity structure of the casting 1 and providing a channel for subsequent impact of deep clogging sand. S2, Internal cavity impact loosening: Using pneumatic impact equipment, the narrow and curved internal cavity of casting 1 after step S1 is subjected to high-frequency mechanical impact, causing the blocked molding sand to crack and loosen. S3, Ultrasonic vibration sand removal: The casting 1 after step S2 is clamped on a special tooling 2 connected to the ultrasonic generating unit 3. The ultrasonic vibration emitted by the ultrasonic generating unit 3 is transmitted to the casting 1, causing the loosened molding sand to peel off from the inner wall of the casting 1. S4. Second shot blasting finishing: The casting 1 after step S3 is placed in the crawler shot blasting machine again to remove the loose residual sand and perform a surface finishing treatment on the casting 1. In step S3, the ultrasonic generating unit 3 is equipped with an adaptive tuning control module for the internal cavity resonance frequency. The tuning control module adjusts or selects the ultrasonic vibration frequency of the scanning frequency band in real time during the ultrasonic vibration process of the ultrasonic generating unit 3, so that the ultrasonic vibration frequency is close to the resonance frequency of the internal cavity or local structure of the casting 1, thereby improving the peeling efficiency of deep sand particles in the casting 1.

[0029] This invention addresses the technical problems of existing sand removal processes, such as difficulty in thoroughly cleaning sand from deep and narrow internal cavities, low sand removal efficiency, and easy mechanical damage, corrosion, or even secondary blockage to thin-walled or delicate internal cavities. It proposes a multi-stage composite sand removal method suitable for investment casting of narrow internal cavities. Compared with traditional single sand removal methods, this invention has several technical advantages: significantly improved sand removal thoroughness, solving the industry pain point of difficulty in removing deep molding sand: This invention adopts a multi-stage composite mechanism of "shot blasting pre-cleaning + pneumatic arch breaking and sand loosening + ultrasonic resonance sand removal + re-shot blasting finishing", wherein: step S1 exposes the inner cavity entrance and shallow structure of casting 1, solving the problem of "tools being unable to effectively enter deep holes" in traditional methods; the high-frequency mechanical impact in step S2 causes the molding sand, which was originally a blockage in the deep inner cavity of casting 1, to crack and loosen first, creating a "weak bonding state" for subsequent steps; step S3 uses the high-frequency acceleration of ultrasonic vibration to make the loose sand particles generate strong inertial force, thereby completely detaching them from the inner wall; finally, step S4 further removes the remaining free sand and smooths the surface of the inner cavity of casting 1; through multi-stage synergistic effect, it has a significant sand removal effect, especially on the deep curved structure and blind hole area of ​​casting 1, and can increase the deep sand particle removal rate to a level that is difficult to achieve with traditional methods.

[0030] By employing the "inner cavity resonance frequency adaptive tuning" technology, the efficiency of deep cavity ultrasonic sand removal for casting 1 is significantly improved. The tuning control module added in step S3 of this invention can automatically match or lock an ultrasonic vibration frequency close to the local natural frequency of the casting 1 based on the vibration response of the casting 1 at different frequencies when the ultrasonic generating unit 3 scans in the 20–40kHz frequency band. This allows the ultrasonic generating unit 3 to maintain the matched ultrasonic vibration frequency during subsequent continuous ultrasonic vibration, thereby enhancing the ultrasonic vibration sand removal effect through the resonance amplification effect between the ultrasonic waves and the inner cavity. The tuning control module also significantly increases the local amplitude of the deep inner cavity, making it easier to remove sand particles from curved cavities and variable cross-section cavities, and solving the technical bottleneck of "rapid energy attenuation and no vibration in deep cavities" in fixed-frequency ultrasound. This achieves a "precise deep cavity sand removal" effect that is difficult to achieve with traditional ultrasound, significantly improving peeling efficiency and sand removal speed.

[0031] The sand removal process will not damage thin-walled or delicate internal cavity structures: Compared with contact mechanical sand removal such as steel needles and drill bits, in this invention: the pneumatic impact only acts on the sand body and does not directly contact the inner wall, and ultrasonic sand removal is a non-contact vibration energy transfer that does not introduce hard impact. Most of the force acts on the sand particles rather than the metal body; therefore, it can effectively avoid the phenomena of inner wall scratches, thin-wall perforation, cavity deformation and local damage to low-strength alloys that occur in traditional cleaning methods. It is particularly suitable for the sand removal process of precision nozzles, small channels and complex flow channels of castings 1.

[0032] Improved sand removal efficiency, controllable process, and suitability for automated industrial applications: The multi-stage composite sand removal method adopts all controllable mechanical and ultrasonic physical processes, which can be executed sequentially by the control system. In automated operation, the overall sand removal process cycle is stable, achieving high sand removal consistency, integration with production lines to achieve automated and batch operation, and reducing reliance on manual skills. Compared with traditional manual cleaning, the sand removal efficiency and stability of the multi-stage composite sand removal method of this invention are significantly improved.

[0033] Purely physical sand cleaning, no risk of corrosion, no chemical pollution, economical and environmentally friendly: The entire process of this invention does not require acid washing, alkali explosion and other chemical sand cleaning, will not corrode the inner wall of the metal, there is no corrosive medium residue, no need for chemical waste liquid treatment, and significantly reduces environmental protection costs and meets the requirements of green manufacturing. The overall process is more environmentally friendly and economical than traditional chemical sand cleaning methods.

[0034] In summary, this invention achieves a highly efficient, thorough, and non-destructive cleaning process for residual sand in the narrow, curved, and deep cavities of casting 1 through a multi-stage composite sand removal mechanism and an ultrasonic sand removal technology with adaptive tuning of the internal cavity resonance frequency. It overcomes the shortcomings of existing sand removal technologies, such as low efficiency, inability to efficiently remove deep sand from casting 1, easy damage to thin walls, and excessive environmental pollution. It is suitable for large-scale and automated production applications.

[0035] As one alternative implementation method: Regarding the specific details of the pneumatic impact device in step S2 above, the pneumatic impact device in step S2 is a high-frequency air pick. The impact needle of the high-frequency air pick is made of high-carbon steel or alloy steel and is customized according to the shape and size of the inner cavity cross section of casting 1.

[0036] When applied, the impact needle of the high-frequency air pick generates high-frequency reciprocating impacts driven by compressed air. Its tip is customized to avoid contact with the inner cavity of the casting 1, so that the impact energy can be more accurately transmitted to the center of the blockage sand or the key stress point. This impact can not only quickly destroy the sintered structure between the molding sand, causing cracks or delamination, but also change the sand from a dense state to a loose state through continuous vibration, thereby significantly reducing the adhesion between the sand and the inner cavity wall.

[0037] The pneumatic impact process in step S2 works synergistically with the channel exposed in step S1, enabling the impact needle to be smoothly inserted into the entrance of a narrow or curved channel. It breaks up and loosens the blockage sand without directly contacting the inner wall of casting 1, improving the vibration response efficiency of subsequent ultrasonic vibration sand removal and avoiding the problem that ultrasound cannot directly remove the hardened sand and damage the inner wall surface.

[0038] In addition, the impact needle can be positioned with a flexible guide sleeve when entering a deep hole to prevent accidental contact with the inner wall of casting 1; and the impact frequency of the high-frequency air pick can be adjusted according to the density of the sand body to avoid excessive impact force.

[0039] Regarding the operating parameters set for the ultrasonic generating unit 3 in step S3 above, in step S3, the ultrasonic vibration frequency of the ultrasonic generating unit 3 is 20kHz to 40kHz, the output power is 200W to 2000W, and the ultrasonic vibration treatment time for the casting 1 on the special tooling 2 is 3-15 minutes.

[0040] In application, the ultrasonic generating unit 3 operates within a set frequency range and power range, causing the amplitude transformer 4 to generate controllable high-frequency mechanical vibration, which is then uniformly transmitted to the overall structure of the casting 1 through the special tooling 2. Different internal cavities of the casting 1 have different geometric dimensions and natural frequencies, while the vibration output frequency of the ultrasonic generating unit 3 is in the range of 20kHz to 40kHz, which can cover most common thin-walled curved cavities, allowing the molding sand inside the casting 1 to effectively respond to the vibration. The power of 200W to 2000W can be selected according to the wall thickness of the casting 1, the degree of sand loosening, and the cavity volume to ensure that the vibration acceleration is sufficient to cause the loose sand particles to produce an "inertial detachment" effect without causing excessive stress concentration in the thin-walled structure. The processing time of 3-15 minutes ensures that the vibration energy is fully transmitted to the deep, intersecting, or locally variable cross-section areas, achieving complete peeling of the loose sand in step S2.

[0041] The ultrasonic vibration sand removal process in step S3 works in synergy with the pneumatic sand loosening process in step S2, making the response in the loosened area more obvious, increasing the sand particle shedding speed and reducing energy loss.

[0042] In addition, the processing time for ultrasonic vibration desanding can be dynamically adjusted based on the internal cavity fluoroscopic image data of casting 1 or the real-time vibration response curve; the power can be pulsed to reduce the heat accumulation of casting 1.

[0043] Regarding the specific structure of the tuning control module set in the ultrasonic generating unit 3, the tuning control module includes a frequency scanning unit, which performs rapid scanning of the casting 1 at an ultrasonic vibration frequency in the 20kHz~40kHz band when the ultrasonic generating unit 3 starts ultrasonic vibration desanding treatment on the casting 1; a feedback detection unit, which detects the vibration response amplitude or energy absorption characteristics of the casting 1 at different vibration frequencies and outputs the detection results; and a tuning control unit, which selects or locks the frequency corresponding to the maximum response according to the detection results of the feedback detection unit, as the working frequency for the ultrasonic generating unit 3 to perform ultrasonic vibration desanding on the current casting 1, and outputs the tuning result.

[0044] When applied, the tuning control module rapidly scans the 20kHz to 40kHz frequency band through the frequency scanning unit. The vibration response of casting 1 in this frequency band is collected in real time by the feedback detection unit. Its amplitude peak or impedance valley represents the inherent resonance frequency of the corresponding local cavity structure. The tuning control unit automatically selects the optimal frequency as the working frequency of ultrasonic vibration sand removal based on these detection results, so that the sound energy forms a local resonance amplification effect inside casting 1.

[0045] The adaptive tuning process achieved through the tuning control module can significantly improve the transmission efficiency of vibration in gradually deepening curved channels and local variable cross-section areas, causing loosened sand particles to be subjected to greater inertial forces, thereby quickly detaching from the inner wall. The ultrasonic vibration sand removal in step S3 and the pneumatic sand loosening in step S2 form a clear "arch breaking-resonance peeling" synergistic path, achieving a deep sand removal capability that is difficult to achieve with traditional fixed-frequency ultrasound, and solving the problems of rapid attenuation of ultrasonic vibration energy in the complex inner cavity of casting 1 and insufficient amplitude in deep cavities in ultrasonic vibration sand removal methods.

[0046] The feedback detection unit can use a piezoelectric accelerometer, fiber optic vibration sensor, or electrical impedance detection to acquire multi-angle vibration response data of the molding sand in the inner cavity of casting 1; the tuning control module can use continuous scanning or frequency hopping scanning, and adjust the vibration response frequency of ultrasonic generator unit 3 in real time during the processing to achieve dynamic closed-loop tuning.

[0047] The second embodiment of the multi-stage composite sand removal method differs from the first embodiment in that, in step S3, the special tooling 2 is made of a metal material with high acoustic conduction efficiency. The structure of the special tooling 2 matches the outline of the casting 1, and it is rigidly connected to the output end of the ultrasonic generating unit 3 through bolts and the amplitude transformer 4, which is used to improve the efficiency of ultrasonic vibration energy transmission to the casting 1.

[0048] When applying the equipment, the special tool 2 is made of a metal material with high acoustic conduction efficiency, such as aluminum alloy, titanium alloy or hardened steel. Its mechanical damping is low, which can significantly reduce the energy loss of ultrasonic vibration during propagation.

[0049] The contour of the special tooling 2 is precisely designed to match the shape of the casting 1, so that the casting 1 fits tightly in the special tooling 2, thereby improving the acoustic coupling capability. The special tooling 2 is rigidly connected to the amplitude transformer 4 and the output end of the ultrasonic generator unit 3 by bolts, so that the vibration energy generated by the ultrasonic generator unit 3 is transmitted to the casting 1 body with minimal attenuation, and forms a resonance enhancement effect with the optimal frequency locked by the tuning control module. This significantly increases the vibration amplitude in the deep inner cavity area of ​​the casting 1, making the sand body peeling more thorough, while avoiding the energy absorption, leakage and vibration dispersion problems caused by traditional soft tooling or fixtures.

[0050] Based on the above embodiments of the multi-stage composite sand cleaning method, a multi-stage composite sand cleaning system is provided, such as... Figure 2 and Figure 3 As shown, the system includes a tracked shot blasting unit for sequentially performing primary shot blasting and secondary shot blasting finishing on casting 1; a pneumatic impact subsystem, including an air compressor, pipelines, and pneumatic impact equipment, for performing the internal cavity impact sand loosening step of casting 1; an ultrasonic sand removal subsystem, including a tuning control module, an ultrasonic generating unit 3, an amplitude transformer 4, and a special tooling 2. The tuning control module controls the vibration of the ultrasonic generating unit 3, which transmits the vibration to the special tooling 2 through bolts and the amplitude transformer 4. The special tooling 2 then transmits the vibration to casting 1 for ultrasonic vibration sand removal; and a control system for controlling the start-up, shutdown, parameter setting, and timing linkage between the tracked shot blasting unit, the pneumatic impact subsystem, and the ultrasonic sand removal subsystem. Based on the tuning results output by the tuning control module, the control system dynamically adjusts or selects the ultrasonic vibration frequency of the ultrasonic generating unit 3 during the ultrasonic vibration sand removal process, so that the ultrasonic vibration frequency is close to the local resonant frequency of the internal cavity of casting 1.

[0051] Among them, such as Figure 3 As shown, the ultrasonic generating unit 3 includes an ultrasonic generator 31 and a transducer 32. The ultrasonic generator 31 transduces ultrasonic waves into ultrasonic vibrations through the transducer 32, and then transmits them to the special tooling 2 through the amplitude transformer 4.

[0052] Specifically, the data exchange logic and working principle between the tuning control module and the control system are as follows: the feedback detection unit of the tuning control module includes a vibration response detection sensor or an energy absorption analysis unit, which is used to detect the vibration response amplitude or energy absorption characteristics of the casting 1 at different frequencies, and feeds the detection results back to the tuning control unit to form the tuning result. The tuning result is fed back to the control system through the tuning control module.

[0053] Specifically, the detection results from the feedback detection unit are received by the tuning control unit and a tuning result is generated. The tuning control module then feeds the tuning result back to the control system.

[0054] In application, the feedback detection unit of the tuning control module collects vibration signals of casting 1 at different ultrasonic excitation frequencies in real time through vibration response detection sensors or energy absorption analysis units, and uploads these signals to the tuning control unit for amplitude-frequency analysis. The tuning control unit generates a tuning result based on the detected amplitude peak or impedance valley, and feeds the tuning result back to the control system through a communication interface. The control system automatically adjusts the output frequency of the ultrasonic generator 31 based on the tuning result, keeping it close to the inherent resonant frequency of the local internal cavity structure of casting 1. Therefore, a closed-loop feedback structure is formed between the control system, the tuning control module, and the ultrasonic generator 3, enabling dynamic frequency tracking and concentrated energy transfer.

[0055] This data exchange logic optimizes the composite sand removal process from the traditional "fixed frequency vibration" to "intelligent adaptive resonance sand removal," significantly enhancing the sand removal efficiency for deep, curved, and thin-walled structures. Especially when the sand body is unevenly loose or the internal cavity geometry is complex, the automatic frequency matching mechanism can ensure that the sand removal process is efficient, stable, and does not damage the inner wall, solving the technical bottlenecks of insufficient depth and unstable effect of traditional ultrasonic sand removal as the workpiece changes.

[0056] In addition, the feedback detection unit can use an accelerometer, an impedance detection module, an acoustic emission sensor, or an optical fiber vibration sensor; the tuning control unit implements real-time signal processing based on FPGA or DSP; data interaction is extended through CAN bus or Modbus protocol; for complex castings 1, a multi-point detection and multi-frequency synthesis scanning strategy is adopted to achieve more accurate and concentrated acoustic energy.

[0057] Regarding the specific structure of the aforementioned amplitude transformer 4, the amplitude transformer 4 adopts a stepped structure or an exponentially gradual structure to enhance the coupling degree of ultrasonic vibration energy transmission from the ultrasonic generating unit 3 to the special tooling 2.

[0058] When applied, the amplitude transformer 4 serves as a key structure in the ultrasonic energy transmission path. Its stepped or exponentially varied structure can amplify and directionally guide the vibration energy provided by the ultrasonic transducer 32, so that the vibration displacement at the end reaches the mechanical amplitude required to effectively excite the casting 1.

[0059] Among them, the stepped amplitude rod 4 is composed of multiple rod segments of different diameters connected in a stepped transition, which has the characteristics of simple structure and convenient processing, and is suitable for ultrasonic vibration transmission of conventional size castings 1.

[0060] The amplitude transformer 4 with an exponentially gradient structure achieves a smooth impedance transition through a continuously changing cross section, resulting in higher energy transmission efficiency and frequency response stability. It is particularly suitable for tooling-casting 1 assemblies with complex shapes and locally thickened structures.

[0061] By using an alloy material with high acoustic transmission efficiency to make the amplitude rod 4 and rigidly connecting it with a special tooling 2 by bolts, the vibration output by the ultrasonic generating unit 3 can be efficiently and stably transmitted to the inner cavity of the casting 1. In addition, with the tuning control mechanism, the vibration energy forms a local standing wave effect in the target area, achieving the effect of rapid peeling of deep sand particles, thus solving the technical problems of fast vibration attenuation and insufficient deep response in traditional soft coupling methods.

[0062] Furthermore, the material of the amplitude transformer 4 is selected from titanium alloy Ti-6Al-4V, which has excellent high-frequency sound energy conduction, or high-hardness quenched steel.

[0063] The multi-stage composite sand removal system uses a control system to uniformly control and manage the start / stop of the tracked shot blasting unit, the pneumatic impact subsystem, and the ultrasonic sand removal subsystem. Based on the different casting dimensions, internal cavity shapes, and sand adhesion states, the control system uses programmable logic instructions to set the duration and process parameters of each operation stage in the multi-stage composite sand removal method, forming an efficient process of "sand removal – arch breaking – vibration peeling – finishing treatment".

[0064] The tracked shot blasting unit performs sand removal and finishing in two stages. It uses a high-intensity shot stream to remove floating sand and loose sand from the outer surface. The pneumatic impact subsystem mechanically loosens the deep-seated blockage sand, forming a loose body that can be vibrated out. The ultrasonic sand removal subsystem improves the shedding rate of deep sand by intelligently tuning the frequency and accurately transmits the vibration energy to the internal structure of the casting 1 through the amplitude transformer 4 and the special tooling 2.

[0065] Each step of this composite process employs the principle of superimposed physical forces to peel off the sand, synergistically achieving a step-by-step transformation of the sand body state from "tightly adhered" to "loose and broken" to "inertial peeling" to "full-area cleaning". This effectively avoids the problems of low efficiency and easy structural damage or corrosion caused by single sand cleaning methods in deep sand cleaning, while significantly improving the consistency, efficiency and environmental friendliness of sand cleaning processing.

[0066] The control system has a built-in process curve preset module, which can quickly switch the sand removal mode according to the structure of different castings; the control system supports MES or SCADA interfaces to integrate into the digital factory.

[0067] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described.

Claims

1. A multi-stage composite sand removal method for investment casting of narrow internal cavities, characterized in that, The process includes the following sequential steps: S1, initial shot blasting: After investment casting, the casting is cut out and placed in a tracked shot blasting machine. High-speed shot is used to impact the outer surface, orifices, and shallow inner cavities of the casting to remove loose sand and oxide scale, thereby exposing the inner cavity structure of the casting and providing a channel for subsequent impact of deep clogging sand. S2, Internal cavity impact loosening: Using pneumatic impact equipment, the narrow and curved internal cavity of the casting after step S1 is subjected to high-frequency mechanical impact, causing the blocked molding sand to crack and loosen. S3. Ultrasonic vibration sand removal: The casting after step S2 is clamped on a special tooling connected to an ultrasonic generator unit. The ultrasonic vibration emitted by the ultrasonic generator unit is transmitted to the casting, causing the loosened molding sand to peel off from the inner wall of the casting. S4. Secondary shot blasting finishing: The casting after step S3 is placed in the crawler shot blasting machine again to remove the loose residual sand and perform a surface finishing treatment on the casting. In step S3, the ultrasonic generating unit is equipped with an adaptive tuning control module for the internal cavity resonance frequency. The tuning control module adjusts or selects the ultrasonic vibration frequency of the scanning frequency band in real time during the ultrasonic vibration of the ultrasonic generating unit, so that the ultrasonic vibration frequency is close to the resonance frequency of the internal cavity or local structure of the casting, thereby improving the peeling efficiency of deep sand particles in the casting.

2. The multi-stage composite sand removal method according to claim 1, characterized in that, In step S2, the pneumatic impact device is a high-frequency air pick, and the impact needle of the high-frequency air pick is made of high-carbon steel or alloy steel, and is customized according to the shape and size of the inner cavity cross section of the casting.

3. The multi-stage composite sand removal method according to claim 1, characterized in that, In step S3, the ultrasonic vibration frequency of the ultrasonic generating unit is 20kHz to 40kHz, the output power is 200W to 2000W, and the ultrasonic vibration treatment time of the casting on the special tooling is 3-15 minutes.

4. The multi-stage composite sand removal method according to claim 3, characterized in that, In step S3, the special tooling is made of a metal material with high acoustic conduction efficiency. The structure of the special tooling matches the outer contour of the casting and is rigidly connected to the output end of the ultrasonic generating unit through bolts and an amplitude transformer, which is used to improve the efficiency of ultrasonic vibration energy transmission to the casting.

5. The multi-stage composite sand cleaning method according to claim 4, characterized in that, The tuning control module includes a frequency scanning unit. When the ultrasonic generating unit starts the ultrasonic vibration desanding treatment of the casting, the frequency scanning unit performs a rapid scan of the casting at an ultrasonic vibration frequency in the 20kHz~40kHz frequency band. And a feedback detection unit, which is used to detect the vibration response amplitude or energy absorption characteristics of the casting at different vibration frequencies and output the detection results; And a tuning control unit, which selects or locks the frequency corresponding to the maximum response based on the detection result of the feedback detection unit, as the working frequency for the ultrasonic generating unit to perform ultrasonic vibration desanding on the current casting.

6. A multi-stage composite sand cleaning system for implementing the multi-stage composite sand cleaning method according to any one of claims 1 to 5, characterized in that, Includes a tracked shot blasting unit, used to sequentially perform the primary shot blasting cleaning and the secondary shot blasting finishing on the casting; And a pneumatic impact subsystem, including an air compressor, pipelines and the pneumatic impact device, for performing the internal impact sand loosening step of the casting; And an ultrasonic sand removal subsystem, including the tuning control module, the ultrasonic generating unit, the amplitude transformer and the special tooling, wherein the tuning control module controls the vibration of the ultrasonic generating unit, the ultrasonic generating unit transmits the vibration to the special tooling through bolts and the amplitude transformer, and the special tooling transmits the vibration to the casting for performing ultrasonic vibration sand removal on the casting; And a control system, used to control the start-up, shutdown, parameter setting, and timing linkage between the tracked shot blasting unit, the pneumatic impact subsystem, and the ultrasonic sand cleaning subsystem; The control system dynamically adjusts or selects the ultrasonic vibration frequency of the ultrasonic generator unit during the ultrasonic vibration desanding process based on the tuning result output by the tuning control module, so that the ultrasonic vibration frequency is close to the local resonance frequency of the inner cavity of the casting.

7. The multi-stage composite sand cleaning system according to claim 6, characterized in that, The feedback detection unit of the tuning control module includes a vibration response detection sensor or an energy absorption analysis unit, which is used to detect the vibration response amplitude or energy absorption characteristics of the casting at different frequencies, and feed the detection results back to the tuning control unit to form the tuning result. The tuning result is fed back to the control system through the tuning control module.

8. The multi-stage composite sand cleaning system according to claim 7, characterized in that, The amplitude transformer adopts a stepped or exponentially varied structure to enhance the coupling degree of the ultrasonic wave generating unit to the special tooling for transmitting ultrasonic vibration energy.

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