Additive manufacturing stainless steel porous structure electrolyte plasma polishing device and polishing method

Abstract

The invention discloses an additive manufacturing stainless steel porous structure electrolyte plasma polishing device and method, and relates to the field of additive manufacturing, and the additive manufacturing stainless steel porous structure electrolyte plasma polishing device structurally comprises a liquid storage tank for storing a polishing liquid, a water pump, a liquid conveying pipeline, a heater, a filter, a flow meter, a multi-degree-of-freedom nozzle, a motor, an industrial personal computer, a workbench, a clamp and an industrial high-speed camera, the liquid storage tank is sequentially connected with the water pump, the flow meter and a pipeline in the workbench through liquid conveying pipelines, the multi-degree-of-freedom nozzle is installed at the tail end of the pipeline of the workbench, the industrial personal computer controls the motor sliding table to move through a transmission line, and the input end of the industrial personal computer is connected with the output end of the industrial high-speed camera through a transmission line. The industrial high-speed camera is arranged above a workpiece clamped on the workbench and used for obtaining a real-time image of machining and the change process of the workpiece, and the multi-degree-of-freedom nozzle is connected with the negative electrode of the power source. The method has a good application prospect in the field of post-treatment of metal additive manufacturing porous structures.

Description

Technical Field

[0001] The present invention relates to the technical field of additive manufacturing, and particularly to an optimization method for the surface treatment process of additively manufactured porous structures (such as triply periodic minimal surfaces, abbreviated as TPMS), aiming to solve the technical problems existing in the polishing process of complex porous structures. Background Art

[0002] Additive manufacturing technology can manufacture metal or non-metal structures with complex internal pores by layer-by-layer material deposition, and is widely used in fields such as aerospace (lightweight heat dissipation structures), biomedical (orthopedic implants), and energy engineering (heat exchangers). During the additive manufacturing process, due to process characteristics (such as the staircase effect, lack of fusion particles, and balling phenomenon in selective laser melting), the surface roughness (Ra 10 - 50 μm) of porous structures is significantly higher than that of traditional machined parts (below Ra 2.5 μm). For example, TPMS is a mathematically defined three-dimensional periodic minimal surface structure, and its topological characteristics enable high-precision forming through additive manufacturing (such as SLM, SLS). Although the TPMS structure has excellent performance, its surface treatment (such as polishing) poses significant challenges: geometric complexity, residual support structures, poor accessibility to internal pores, high difficulty in processing gradient structures, etc.

[0003] Electrolyte plasma polishing technology is considered an efficient, environmentally friendly, and economical metal surface polishing process, especially having unique advantages for the surface polishing of complex surface structure parts or cavities. This technology combines the synergistic effects of electrolysis and plasma discharge. Its basic working principle is to immerse the workpiece in a low-concentration neutral salt solution and apply a high-voltage direct current electric field. Driven by the oxygen evolution at the anode and the Joule heat effect, a stable gaseous envelope layer is rapidly formed on the workpiece surface. During this process, the micro-protrusions on the surface are preferentially selectively etched due to the tip effect. Through the combined action of plasma impact, micro-region electrolysis, and chemical passivation, nano-level surface roughness control is achieved. Compared with traditional polishing processes, this technology has non-contact processing characteristics, can eliminate mechanical stress and heat-affected zones, avoid micro-cracks and lattice distortion, and at the same time, the polishing solution is a neutral salt solution, which can be recycled by replenishing the salt solution and the solution is non-toxic and easy to recover, and the exhaust gas emissions are reduced by more than 90% compared with chemical polishing. This technology is applicable to metal surface polishing, removal of machining marks, deburring, removal of oxide layers, etc., and has the advantages of effectively reducing the surface roughness of metals, improving the wear resistance and corrosion resistance of metal surfaces, there being no macroscopic force during the polishing process, and no micro-cracks and residual stress being left on the workpiece surface to affect the workpiece life.

[0004] Due to the limitation of the size of the polishing liquid tank, the existing electrolyte plasma polishing equipment can only polish the surfaces of medium and small-sized parts. When processing complex geometric workpieces (such as porous and three-dimensional curved surfaces), the penetration ability of the plasma field in the liquid tank is limited, resulting in insufficient local polishing or burr residues, which greatly restricts the application range of the plasma polishing equipment. Summary of the Invention

[0005] The purpose of the present invention is to provide an electrolyte plasma polishing device and method for an additively manufactured stainless steel porous structure to solve the problem of difficult polishing existing in the existing additively manufactured porous structures, significantly improving the surface quality and flow resistance of the additively manufactured stainless steel porous structure. The electrolyte plasma polishing device and method can polish workpieces with complex geometric shapes.

[0006] An electrolyte plasma polishing device and method for an additively manufactured stainless steel porous structure include the following steps:

[0007] Step 1: Chemically degrease the workpiece with a porous structure, then ultrasonically clean it with deionized water and alcohol, and after drying, clamp it on a special fixture.

[0008] Step 2: Pour the polishing liquid into the liquid storage tank, and control the temperature of the polishing liquid at 75°C - 85°C through a heater.

[0009] Step 3: The industrial control computer controls the motor to move the special fixture to the starting polishing position of the workpiece. The workpiece is connected to the positive pole of the power supply and serves as the processing anode.

[0010] Step 4: Align the multi-degree-of-freedom nozzle with the surface of the workpiece to be processed. The nozzle is connected to the negative pole of the power supply and serves as the processing cathode.

[0011] Step 5: Align an industrial high-speed camera with the processing surface of the workpiece to record the processing reaction process and the changes of the workpiece.

[0012] Step 6: Turn on the water pump to make the polishing liquid in the liquid storage tank flow through the flowmeter along the liquid delivery pipeline, and then flow through the liquid delivery pipeline to the nozzle and spray out to form a polishing liquid jet with a certain flow rate, stable and continuous, to polish the workpiece.

[0013] Step 7: Immerse the polished workpiece prepared in Step 6 in absolute ethanol, and then rinse it with distilled water multiple times to remove the remaining polishing liquid in the workpiece.

[0014] Step 8: Place the workpiece obtained in Step 7 in a ventilated place to dry naturally.

[0015] In the above steps, the solutions used for chemical degreasing in Step 1 are sodium hydroxide solution, hydrogen peroxide, and sodium carbonate solution with certain concentrations in sequence, and at the same time, perform water bath heating to 80°C.

[0016] The polishing liquid added in Step 2, by weight percentage, contains: ammonium sulfate 1% - 4%, complexing agent 1.5% - 3.5%, organic acid 2% - 3%, and the balance is deionized water;

[0017] The specific parameters of electrolyte plasma polishing in Step 6 are: voltage 300V, polishing time 5 - 10 minutes, nozzle flow rate 0.5 - 1 L / min, and machining gap within 3 - 5 mm.

[0018] The additive manufacturing stainless steel porous structure electrolyte plasma polishing device used in the above method includes a liquid storage tank for storing polishing liquid, a water pump, a liquid delivery pipeline, a heater, a flow meter, a multi - degree - of - freedom nozzle, a motor, an industrial control computer, a workbench, a fixture, and an industrial high - speed camera. The liquid storage tank is connected to the pipelines in the water pump, flow meter, and workbench in sequence through the liquid delivery pipeline. The end of the workbench pipeline is equipped with a multi - degree - of - freedom nozzle. The industrial control computer controls the movement of the motor through a transmission line. The input end of the industrial control computer is connected to the output end of the industrial high - speed camera through a transmission line. The industrial high - speed camera is arranged above the workpiece clamped on the workbench to obtain real - time images of the processing and the change process of the workpiece. The multi - degree - of - freedom nozzle is connected to the negative pole of the power supply.

[0019] Beneficial effects: An additive manufacturing stainless steel porous structure electrolyte plasma polishing device and polishing method provided by the present invention have the following advantages:

[0020] 1. The polishing liquid is ejected through the multi - degree - of - freedom nozzle to form a polishing liquid jet, which is sprayed onto the surface of the workpiece at a certain flow rate for polishing. It can not only process small and medium - sized metal workpieces, but also polish large - sized workpieces and workpieces with complex geometric shapes, avoiding the problems of difficult polishing and high energy consumption caused by the limitation of the polishing tank size.

[0021] 2. The present invention is equipped with the best process parameters of synchronous process tests while designing the device, providing a method for solving the problems of difficult polishing and poor polishing effect of additive manufacturing stainless steel porous structures.

[0022] 3. The polishing liquid quantitatively ejected through the nozzle can achieve electrolyte plasma polishing, is not limited by the polishing tank size, and the polished liquid that has been filtered and recycled can be reused, improving the utilization rate of the polishing liquid and thus reducing the experimental cost.

[0023] 4. The polishing process is precisely controlled by the industrial control computer and the high - speed industrial camera, significantly improving the polishing effect and achieving high - efficiency polishing of additive manufacturing stainless steel porous structures. Description of the Drawings

[0024] Figure 1 It is the schematic diagram of additive manufacturing stainless steel porous structure electrolyte plasma polishing in the embodiment of the present invention;

[0025] Figure 2 Assembly schematic diagram of an electrolyte plasma polishing device for additively manufactured stainless steel porous structure according to the present invention;

[0026] Figure 3 Special fixture assembly schematic diagram and key component drawings for electrolyte plasma polishing of additively manufactured stainless steel porous structure workpieces;

[0027] Figure 4 Surface morphology of additively manufactured stainless steel TPMS structure workpiece by electrolyte plasma polishing, where A is the original surface of the workpiece before polishing and B is the surface of the workpiece after polishing.

[0028] The figure includes: 1 - high - speed camera; 2 - infusion pipeline; 3 - flowmeter; 4 - nozzle; 5 - fixture; 6 - experimental tank; 7 - filter; 8 - water pump; 9 - motor; 10 - workbench; 11 - liquid storage tank. Specific implementation mode

[0029] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments:

[0030] Embodiment 1

[0031] As Figure 2 shown, an electrolyte plasma polishing device for additively manufactured stainless steel porous structure includes an industrial high - speed camera 1, an infusion pipeline 2, a flowmeter 3, a nozzle 4, a fixture 5, an experimental tank 6, a filter 7, a water pump 8, a motor 9, a workbench 10, and a liquid storage tank 11. The liquid storage tank is connected to the pipelines in the water pump 8, the flowmeter 3, and the workbench 10 in sequence through the infusion pipeline 2. A multi - degree - of - freedom nozzle 4 is installed at the end of the workbench pipeline. The industrial control computer controls the movement of the motor 9 through a transmission line. The input end of the industrial control computer is connected to the output end of the industrial high - speed camera 1 through a transmission line. The industrial high - speed camera 1 is arranged above the workpiece clamped on the workbench 10 to obtain real - time images of the processing and the change process of the workpiece. The multi - degree - of - freedom nozzle 4 is connected to the negative pole of the power supply.

[0032] The special fixture mechanism 5 includes: a positioning seat 501, a bracket 502, a fixture base 503, a workpiece positioning block 504, and a conductive block 505. The bracket 502 is fixed to the motor 9 through the positioning seat 501 to ensure the stability of the entire fixture mechanism. The fixture base 503 is installed on the bracket 502 through bolts. The workpiece positioning block 504 is embedded according to the guiding groove on the fixture base 503 to determine the position of the workpiece. Then, the conductive block 505 is pushed by bolts to clamp the workpiece and conduct electricity to the workpiece.

[0033] Using the above device to perform electrolyte plasma polishing on additively manufactured stainless steel TPMS structure, including the following steps:

[0034] Step 1: chemically degrease the TPMS workpiece, then use ionized water and alcohol to ultrasonically clean it, and then clamp it on a special fixture 5 after drying;

[0035] Step 2, pour the polishing liquid into the liquid storage tank 11, and control the temperature of the polishing liquid at 75° C. to 85° C. through a heater;

[0036] Step 3, the industrial computer controls the motor 9 to move the special fixture 5 to the starting polishing position of the workpiece, and the workpiece is connected to the positive pole of the power supply as a processing anode;

[0037] Step 4, align the multi-degree-of-freedom nozzle 4 with the workpiece surface to be processed, and connect the nozzle to the negative pole of the power supply as the cathode of the processing;

[0038] Step 5, aiming the industrial high-speed camera 1 at the workpiece processing surface to record the processing reaction process and workpiece changes;

[0039] Step 6, turning on the water pump 8, so that the polishing liquid in the liquid storage tank 11 flows through the flow meter 3 along the liquid delivery pipe 2, and then flows to the nozzle 4 through the liquid delivery pipe 2 to form a polishing liquid jet with a certain flow rate and stable and continuous, so as to polish the workpiece;

[0040] Step 7, soaking the polished workpiece prepared in step 6 in anhydrous ethanol, and then rinsing with distilled water for multiple times to remove the polishing liquid remaining in the workpiece;

[0041] Step 8: Place the workpiece obtained in step 7 in a ventilated place to dry naturally.

[0042] Example 1 The polished workpiece obtained is as follows Figure 4 As shown in Figure 1, A is the original surface of the workpiece before polishing. The results show that the device has a significant effect on the polishing of the additively manufactured TPMS structure. As shown in Figure 1, the workpiece surface has a good surface gloss after polishing.

[0043] It should be noted that the above embodiments are only for describing the preferred embodiments of the present invention and are not intended to limit the present invention. Any modification of the form, equivalent replacement of technical features or partial adjustment of the technical solution made by any person skilled in the art to the embodiments under the premise of following the technical concept of the present invention shall be deemed to fall within the protection scope of the claims of the present invention as long as it does not deviate from the essential content of the present invention.

Claims

1. An additive manufacturing stainless steel porous structure electrolyte plasma polishing device, characterized in that: It includes a liquid storage tank for storing polishing liquid, a water pump, an infusion pipeline, a heater, a filter, a flow meter, a multi-degree-of-freedom nozzle, a motor, an industrial computer, a workbench, a fixture and an industrial high-speed camera. The liquid storage tank is connected to the water pump, the flow meter and the pipeline in the workbench in sequence through the infusion pipeline. The end of the workbench pipeline is equipped with a multi-degree-of-freedom nozzle. The industrial computer controls the movement of the motor slide through a transmission line. The input end of the industrial computer is connected to the output end of the industrial high-speed camera through a transmission line. The industrial high-speed camera is arranged above the workpiece clamped on the workbench to obtain real-time images of the processing and the change process of the workpiece. The multi-degree-of-freedom nozzle is connected to the negative pole of the power supply.

2. The additive manufacturing stainless steel porous structure electrolyte plasma polishing device according to claim 1, characterized in that The workbench is equipped with a special fixture for porous structure and a motor for driving the fixture to move.

3. The additive manufacturing stainless steel porous structure electrolyte plasma polishing device according to claim 1, characterized in that The experimental tank and the liquid storage tank are connected via a filter.

4. The additive manufacturing stainless steel porous structure electrolyte plasma polishing device according to claim 1, characterized in that An industrial high-speed camera is arranged around the workbench to record the processing reaction process and changes of the workpiece on the processing surface of the workpiece.

5. A method for polishing a workpiece using an additively manufactured stainless steel porous structure electrolyte plasma polishing device according to any one of claims 1 to 4, characterized in that: (1) The porous workpiece is chemically degreased, then ultrasonically cleaned with ionized water and alcohol, and then clamped on a special fixture after drying; (2) The nozzle is connected to the negative pole of the power supply as the cathode of the processing, and the workpiece is connected to the positive pole of the power supply as the anode of the processing; (3) Turn on the water pump to allow the polishing liquid in the liquid storage tank to flow through the flow meter along the liquid delivery pipeline, and then flow through the liquid delivery pipeline to the nozzle to form a polishing liquid jet with a certain flow rate and stable and continuous flow to polish the workpiece; (4) Soak the polished workpiece in anhydrous ethanol, and then rinse it with distilled water several times to remove the polishing liquid remaining in the workpiece.

6. A method for additive manufacturing of stainless steel porous structure electrolyte plasma polishing, characterized in that: The polishing parameters are as follows: the polishing liquid temperature is 75°C to 85°C, the polishing liquid pH is 6.6 to 7.5, the voltage used is 200 to 300V, the polishing time is 5 to 10 minutes, the nozzle flow rate is 0.5 to 1L / min, and the inter-electrode gap is 3 to 5mm.

Images