Air cylinder and additive manufacturing method thereof

Abstract

The invention provides an air cylinder and an additive manufacturing method thereof and belongs to the field of additive manufacturing, a cavity is formed in the wall face of the air cylinder, through holes are formed in the end faces of the two ends of the air cylinder and communicate with the cavity, and the cavity is sequentially filled with a first lattice layer, a third lattice layer and a second lattice layer from outside to inside in the radial direction of the air cylinder. The porosity of the first lattice layer, the second lattice layer and the third lattice layer is sequentially reduced, and the rigidity of the first lattice layer, the second lattice layer and the third lattice layer in the axial direction of the air cylinder is sequentially increased. According to the invention, the inner wall of the cavity of the inner wall of the cylinder is provided with a plurality of lattice layers respectively composed of a plurality of lattice types, and the positions of different lattice layers are arranged according to the stress condition in the use process of the cylinder, so that the cylinder with the lattice structure has good axial rigidity to cope with the complex stress condition; and the light weight and high heat conduction and heat dissipation capacity of the cylinder are guaranteed through cooperation of the multiple lattice layers, and the high-performance design requirement of the cylinder can be met.

Description

Technical Field

[0001] The present invention relates to the technical field of additive manufacturing, and particularly relates to a cylinder and an additive manufacturing method thereof. Background Art

[0002] At present, there is a strong demand for high-efficiency and lightweight engines in unmanned aerial vehicles. The performance and weight of the engine are directly related to the endurance, payload capacity, and flight performance of the aircraft. Chinese Patent CN201680081457 discloses an additive manufactured compressor component with a lattice core optimized for heat and sound, which has at least one internal area including a lattice structure with multiple repeating unit cells. The lattice structure can significantly reduce the material usage while ensuring the structural strength of the component, realizing the lightweight of the cylinder barrel. During use, the cylinder will not only be subjected to large reciprocating forces, resulting in complex stress conditions, but also experience a high temperature rise during operation, thereby affecting the performance of the cylinder. However, the current cylinder adopts a lattice structure of a single lattice type and cannot meet the high-performance design requirements of the cylinder. Summary of the Invention

[0003] In view of this, the present invention proposes a cylinder and an additive manufacturing method thereof to solve the problem that the current cylinder adopts a lattice structure of a single lattice type and cannot meet the complex stress conditions and temperature rise conditions generated during the operation of the cylinder, thereby affecting the performance of the cylinder.

[0004] The technical solution of the present invention is realized as follows: The present invention provides a cylinder. A cavity is formed inside the wall surface of the cylinder, and through holes are formed in both end faces of the cylinder. The through holes are communicated with the cavity. Inside the cavity, a first lattice layer, a third lattice layer, and a second lattice layer are sequentially filled from the outside to the inside along the radial direction of the cylinder. The porosity of the first lattice layer, the second lattice layer, and the third lattice layer decreases in sequence, and the stiffness of the first lattice layer, the second lattice layer, and the third lattice layer along the axial direction of the cylinder increases in sequence.

[0005] On the basis of the above technical solution, preferably, the first lattice layer is a cylindrical structure composed of a plurality of first lattice units, and the first lattice unit is a simple cubic lattice unit structure; the second lattice layer is a cylindrical structure composed of a plurality of second lattice units, and the second lattice unit is a face-centered cubic lattice unit structure; the third lattice layer is a cylindrical structure composed of a plurality of third lattice units, and the third lattice unit is a body-centered cubic lattice unit structure.

[0006] More preferably, the porosity of the first lattice layer is greater than 95%, the porosity of the second lattice layer is 83% - 95%, and the third lattice layer is less than 83%.

[0007] More preferably, the stiffness of the first lattice layer, the third lattice layer and the second lattice layer increases in sequence along the radial direction of the cylinder.

[0008] More preferably, the first lattice unit includes eight end points, which are respectively located at the eight tips of a cube. Every four end points enclose one face of the cube. Each end point is connected to the other end point that is not adjacent to the face where it is located, and a simple cube is formed; the second lattice unit includes eight end points and six face center points. Each face center point is located at the center of each face of the cube. Each face center point is simultaneously connected to the other three face center points of the adjacent faces and encloses a birdcage structure. The eight end points symmetrically surround the center of the cube and are connected to the birdcage structure to form a face-centered cube; the third lattice unit includes eight end points and one body center point. The body center point is located at the center of the cube. Each end point is connected to the other end point that is not adjacent to the face where it is located. The body center point is simultaneously connected to the eight end points and encloses a body-centered cube.

[0009] More preferably, the side length of the cube of the first lattice unit is 1-10 mm; the side length of the cube of the second lattice unit is 2-8 mm; the side length of the cube of the third lattice unit is 3-6 mm.

[0010] More preferably, a plurality of fins are arranged at intervals along the axial direction on the outer peripheral wall of the cylinder, and the fins are sheet-like structures composed of the first lattice units.

[0011] More preferably, a cylinder is simultaneously penetrated through the middle of the plurality of fins. The cylinder is hollow and extends along the axial direction of the cylinder at both ends.

[0012] Based on the above technical solutions, preferably, the thickness of the third lattice layer is the smallest.

[0013] On the other hand, the present invention also provides an additive manufacturing method for a cylinder, which is used to prepare the above-mentioned cylinder, and includes the following steps. Step 1, establish a model of the cylinder, and define the wall surface of the cylinder, the first lattice layer, the second lattice layer, the third lattice layer and the transition regions of each part; Step 2, determine the initial parameters of the thickness and porosity of the first lattice layer, the second lattice layer and the third lattice layer, and determine the initial parameters of the side length of the cube of the first lattice unit, the second lattice unit and the second lattice unit; Step 3, use finite element analysis to perform stress analysis on the model, determine the layout order of the first lattice layer, the second lattice layer and the third lattice layer according to the stress condition of the model, optimize the design parameters of the model, and then print to obtain the product according to the optimized model.

[0014] A cylinder and an additive manufacturing method thereof according to the present invention have the following beneficial effects compared with the prior art: (1) In the present invention, multiple lattice layers composed of various lattice types are arranged on the inner wall of the cylinder inner wall cavity. The positions of different lattice layers are arranged according to the stress conditions during the use of the cylinder, which not only ensures that the cylinder with a lattice structure has good axial stiffness to cope with complex stress conditions, but also ensures the light weight and high heat conduction and heat dissipation capacity of the cylinder through the cooperation of multiple lattice layers, and can meet the high-performance design requirements of the cylinder.

[0015] (2) In the present invention, fins are arranged on the outer wall of the cylinder to assist heat dissipation. At the same time, the fins are also made of a lattice structure, and the cylinder body passes through each fin. By using the natural convection air flow during the operation of the engine to flow through the cylinder body and the lattice structure fins, the heat dissipation performance of the cylinder can be significantly improved.

[0016] (3) The present invention utilizes additive manufacturing technology. Without traditional molds, it can directly manufacture a cylinder barrel with a complex lattice structure according to a digital model, reducing production costs and improving production efficiency. At the same time, the rapid manufacturing ability of additive manufacturing technology can meet the market's demand for rapid iteration and customized production of engines. The lattice structure design reduces the material usage and improves the material utilization rate, further reducing the raw material cost. Moreover, through finite element analysis and geometric parameter optimization, the lattice structure increases the density in high-stress areas and reduces the density in low-stress areas, achieving the optimal distribution of materials, improving the overall structural strength and stiffness of the cylinder barrel, and ensuring reliability and stability under various working conditions. Brief Description of the Drawings

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0018] Figure 1 is a three-dimensional view of the cylinder of the present invention; Figure 2 is a cross-sectional three-dimensional view of the cylinder of the present invention; Figure 3 is a partial cross-sectional view of the cylinder of the present invention; Figure 4 is a schematic structural diagram of the first lattice unit of the present invention; Figure 5 is a schematic structural diagram of the second lattice unit of the present invention; Figure 6 is a schematic structural diagram of the third lattice unit of the present invention.

[0019] In the figure: 1. Cylinder; 101. Cavity; 102. Through hole; 2. First lattice layer; 21. First lattice unit; 211. End point; 3. Second lattice layer; 31. Second lattice unit; 311. Face-centered point; 4. Third lattice layer; 41. Third lattice unit; 411. Body-centered point; 5. Fin; 6. Cylinder body. Detailed implementation manners

[0020] Next, in combination with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0021] As Figure 1 shown, in combination with Figure 2 and Figure 3, a cylinder of the present invention, a cavity 101 is provided inside the wall surface of the cylinder 1, through holes 102 are provided at both end faces of the cylinder 1, and the through holes 102 communicate with the cavity 101. Inside the cavity 101, a first lattice layer 2, a third lattice layer 4, and a second lattice layer 3 are filled in sequence from the outside to the inside along the radial direction of the cylinder 1. The porosity of the first lattice layer 2, the third lattice layer 3, and the third lattice layer 4 decreases in sequence, and the stiffness of the first lattice layer 2, the second lattice layer 3, and the third lattice layer 4 increases in sequence along the axial direction of the cylinder 1. The advantages of filling the lattice structure layer inside the cavity 101 on the wall surface of the cylinder 1 are as follows: 1) Significantly reduce the mass of the cylinder 1, making the engine lightweight, thereby greatly improving the thrust-to-weight ratio of the drone. In the case of improving the thrust-to-weight ratio, the same thrust can achieve a longer pushing distance, which is crucial for enhancing the power output of the engine and the acceleration performance of the aircraft. A higher thrust-to-weight ratio can make the aircraft perform better during takeoff, climb, and flight; 2) The openness and connectivity of the lattice structure increase the heat dissipation area, promoting heat transfer and dissipation. This design can effectively reduce the temperature of the cylinder 1 and improve the reliability and durability of the engine during high-power density operation; at the same time, since the cavity 101 is provided inside the wall surface of the cylinder 1, the wall thickness of the cylinder 1 can be significantly thinned, further enhancing the heat conduction and dissipation performance; 3) Through lightweight and heat dissipation optimization design, the preparation material cost of the cylinder 1 itself is greatly reduced; at the same time, the overall performance of the engine is improved, including higher power output, lower fuel consumption, and longer service life. However, under working conditions, a cylinder liner will be placed inside the hollow cylinder of the cylinder 1. During operation, the inner wall of the cylinder liner will continuously generate frictional heat due to the reciprocating motion of the piston, and the heat will conduct to the inside of the cylinder 1; moreover, the reciprocating force of the piston will also cause stress and strain on the cylinder liner and the cylinder 1 where the cylinder liner is installed. If a lattice structure layer of a single lattice type is filled into the cavity 101, it is difficult to simultaneously meet the two requirements of the strength and heat dissipation performance of the cylinder 1. In this embodiment, multiple lattice layers are provided inside the cavity 101 and the multiple lattice structures cooperate with each other. According to the internal structure and force distribution of the cylinder 1, the layout of multiple lattice structure layers is reasonably designed, increasing the lattice density in high-stress areas and reducing the lattice density in low-stress areas to achieve the optimal distribution of materials and improve the overall performance.Specifically, in the working environment, the cylinder 1 mainly receives the heat conducted from the inside to the outside by the piston and the cylinder liner, and the force exerted on the inner wall of the cylinder liner due to the reciprocating movement and friction of the piston inside the cylinder liner. As a result, stress and strain occur on the inner wall of the hollow cylinder of the cylinder 1 in contact with the cylinder liner. This stress situation is mainly concentrated in the axial direction of the cylinder 1. Therefore, in this embodiment, the second lattice layer 3 with a medium porosity and axial stiffness is arranged at a position closer to the inside of the cavity 101, so that the internal structure of the cylinder 1 has good axial stiffness while ensuring good heat conduction and dissipation performance; and the first lattice layer 2 with a larger porosity and a poorer axial stiffness is arranged at a position closer to the external environment of the cavity 101, which helps to fully conduct and dissipate heat, and at the same time will not significantly weaken the structural stiffness of the cylinder 1; the third lattice layer 4 with the smallest porosity and the best axial stiffness is sandwiched between the first lattice layer 2 and the second lattice layer 3. The third lattice layer 4 can be regarded as the skeleton of the wall of the cylinder 1, so that the overall structure of the cylinder 1 has good structural stiffness. In addition, when the engine is operating, natural convection wind will be generated. The natural convection wind enters the cavity 101 through the through hole 102 at one end of the cylinder 1, and after passing through the multi-lattice layer structure in the cavity 101, it flows out from the through hole 102 at the other end of the cylinder 1, thereby taking out the heat inside the cylinder 1 and achieving good heat dissipation performance.

[0022] In Figure 3 In a preferred embodiment shown, the first lattice layer 2 is a cylindrical structure composed of a plurality of first lattice units 21. The first lattice unit 21 is a simple cubic lattice unit structure. The unit shape of the simple cubic lattice is a standard regular cube, with a regular geometric structure, which is convenient for manufacturing and analysis. The unit size of the simple cubic lattice is 1 - 10 millimeters; the unit size determines the size of the lattice unit. A smaller unit size can provide higher strength and stiffness, but will increase the material consumption and manufacturing cost. A larger unit size can reduce the weight, but may reduce the structural strength. The unit density is the number of lattice units per 0.1 - 0.5 unit volume; the unit density affects the strength and stiffness of the lattice. A higher unit density can provide better support performance, but will increase the material consumption and weight.

[0023] The second lattice layer 3 is a cylindrical structure composed of a number of second lattice units 31. The second lattice unit 31 is a face-centered cubic lattice unit structure. The unit shape of the face-centered cubic lattice is a cube, and the center point of each face provides additional support, enhancing the strength and stiffness of the structure. The unit size of the face-centered cubic lattice is 3 - 6 mm; the unit size of the face-centered cubic lattice is usually small to ensure that each face-centered point can effectively participate in the structural support. A smaller unit size can improve strength and stiffness, but it will increase manufacturing complexity. The unit density is the number of lattice units per unit volume of 0.4 - 0.8; the unit density of the face-centered cubic lattice is relatively high, which can provide better strength and stiffness. A higher unit density can enhance the stability of the structure, but it will increase the weight.

[0024] The third lattice layer 4 is a cylindrical structure composed of a number of third lattice units 41. The third lattice unit 41 is a body-centered cubic lattice unit structure. The unit shape of the body-centered cubic lattice is a cube, and the center point provides additional support, enhancing the strength and stiffness of the structure. The unit size of the body-centered cubic lattice is 2 - 8 mm; the unit size of the body-centered cubic lattice is usually slightly larger than that of the simple cubic lattice to ensure that the center point can provide sufficient support. A smaller unit size can improve strength, but it will increase the manufacturing difficulty. The unit density is the number of lattice units per unit volume of 0.3 - 0.7; the unit density of the body-centered cubic lattice is relatively high, which can provide better strength and stiffness. A higher unit density can enhance the stability of the structure, but it will increase the weight.

[0025] It should be noted that although the structure of each lattice unit in this embodiment is a simple cube, face-centered cube, or body-centered cube, the above cube structure generally refers to the arrangement of atoms in the unit cell structure. However, the lattice units forming each lattice layer in this embodiment are not unit cells. The structure of the lattice unit only adopts the principle of the arrangement of atoms in the unit cell structure, but the actual lattice unit is a structural unit composed of points and lines, and its size is obviously much larger than that of the unit cell.

[0026] In Figure 3 In a preferred embodiment shown, the porosity of the first lattice layer 2 is greater than 95%, the porosity of the second lattice layer 3 is 83% - 95%, and the third lattice layer 4 is less than 83%. The lower the porosity, the higher the density of the lattice units in the lattice layer, and thus better strength and stiffness can be provided. A higher unit density can enhance the stability of the structure, but it will increase the weight.

[0027] In Figure 3In a preferred embodiment shown, the radial stiffness of the first, third, and second lattice layers 2, 4, and 3 increases sequentially along the cylinder 1. This results in the cylinder 1's overall structure exhibiting a trend of gradually increasing structural stiffness from the outside inward, thereby ensuring greater structural stiffness in the areas of the cylinder 1 where stress and strain are most pronounced. Typically, the second lattice unit 31, as a face-centered cubic structure, exhibits substantially the same radial stiffness (including in the X and Y directions) as its axial stiffness (including in the Z direction). Therefore, placing the second lattice layer 3 at the innermost layer of the cavity 101 allows it to better adapt to the stress and strain conditions experienced by the cylinder 1 under operating conditions, compared to placing the third lattice layer 4, which has the highest axial stiffness and intermediate radial stiffness, in the innermost layer.

[0028] exist Figure 4 、 5 In a preferred embodiment shown in Figure 6, this embodiment provides one of the implementation structures for different types of lattice structures for additive manufacturing. Specifically, the first lattice unit 21 includes eight endpoints 211, and the eight endpoints 211 are respectively located at the eight tips of the cube. Every four endpoints 211 surround one of the faces of the cube. Each endpoint 211 is connected to another endpoint 211 that is not adjacent to the face where it is located, and surrounds a simple cube. At least four faces of the simple cube are X-shaped cross lines. The structure is simple and regular; the second lattice unit 31 includes eight endpoints 211 and six face centers 311. Each face center 311 is located at the center of each face of the cube. Each face center 311 is simultaneously connected to the other three face centers 311 of the adjacent faces to form a birdcage structure. The birdcage structure can be regarded as a plurality of rhombuses. The birdcage-shaped frame is surrounded by a cube with eight endpoints 211 symmetrically connected to the center of the cube at the center, and the eight endpoints 211 are connected to the middle joint point of the rhombus in the birdcage structure to form a face-centered cube. The third lattice unit 41 includes eight endpoints 211 and a body center point 411. The body center point 411 is located at the center of the cube. Each endpoint 211 is connected to another endpoint 211 that is not adjacent to its face. The body center point 411 is connected to the eight endpoints 211 at the same time to form a body-centered cube. The difference between the body-centered cube and the simple cube is that the body center point 411 at the center of the cube is connected to each endpoint 211 by a connecting line. Therefore, the body-centered cube has a lower porosity and better axial stiffness than the simple cube.

[0029] exist Figure 4 、 5In a preferred embodiment shown in FIGS. 5 and 6, the side length of the cube of the first lattice unit 21 is 1-10 mm; the side length of the cube of the second lattice unit 31 is 2-8 mm; the side length of the cube of the third lattice unit 41 is 3-6 mm. The unit size determines the size of the lattice unit. A smaller unit size can provide higher strength and stiffness, but will increase the material usage and manufacturing cost. A larger unit size can reduce the weight, but may reduce the structural strength. Therefore, it is necessary to design the lattice size according to different lattice types.

[0030] In Figure 2 a preferred embodiment shown in FIGS. 7 and 8, a plurality of fins 5 are arranged at intervals along the axial direction on the outer peripheral wall of the cylinder 1. The fins 5 increase the area of the outer wall of the cylinder 1 and contribute to improving the heat dissipation performance of the cylinder 1. The fin 5 is a sheet-like structure composed of the first lattice unit 21, which further improves the heat dissipation capacity and heat dissipation area of the fin 5.

[0031] In Figure 2 a preferred embodiment shown in FIGS. 9 and 10, a cylinder body 6 is simultaneously penetrated through the middle parts of a plurality of fins 5. The cylinder body 6 is hollow and extends along the axial direction of the cylinder 1 at both ends. When the engine is working, the natural flowing wind generated will flow through the cylinder body 6 to take out the heat conducted from the inside of the cylinder 1 to the fins 5, achieving good heat dissipation performance.

[0032] In Figure 3 a preferred embodiment shown in FIGS. 11 and 12, the thickness of the third lattice layer 4 is the smallest. Since the third lattice layer 4 with the largest axial stiffness is used as the internal skeleton of the overall structure of the cylinder 1, its suitable thickness can already meet the structural strength requirements of the cylinder 1; when its thickness is too thick, it will have an adverse impact on the heat dissipation performance of the cylinder 1.

[0033] As Figure 1 shown in FIGS. 13 and 14, combined with Figure 2 and Figure 3 FIGS. 15 and 16, an additive manufacturing method for a cylinder of the present invention for preparing the above-mentioned cylinder includes the following steps: Step 1, establish a model of the cylinder 1, usually completed in 3D modeling software. Import the designed 3D object (such as a CAD model) into 3D printing software or analysis software for subsequent processing and analysis. Then define the wall surface of the cylinder 1, the first lattice layer 2, the second lattice layer 3, the third lattice layer 4 and the transition regions of each part, so as to define the shape of the lattice structure in the model and determine the volume ratio of the lattice structure in the model; among them, the transition region refers to the connection or transition region between different parts of the model, and its function is to ensure the smooth transition between different parts of the model and optimize the structural performance. It should be noted that at this time, the arrangement positions of the first lattice layer 2, the second lattice layer 3 and the third lattice layer 4 are preliminary designs based on the previous theoretical research and analysis.

[0034] Step 2: Determine the initial parameters of the thickness and porosity of the first lattice layer 2, the second lattice layer 3, and the third lattice layer 4, and determine the initial parameters of the cube side lengths of the first lattice unit 21, the second lattice unit 31, and the second lattice unit 31, so as to obtain the initial model of the cylinder 1.

[0035] Step 3: Use finite element analysis to perform stress analysis on the model and evaluate the performance of the model under stress. Determine whether the layout order of the first lattice layer 2, the second lattice layer 3, and the third lattice layer 4 can effectively adapt to the stress condition requirements of the cylinder 1 according to the finite element analysis of the model, and optimize the model design parameters to ensure the reliability and stability of the model in actual use. Optimize the design to reduce stress concentration, and the optimization algorithm can be selected from existing multiple algorithms according to actual requirements; select the optimal solution for printing after performing finite element analysis on several design cases, and finally print the product according to the optimized model.

[0036] The operation steps of additive manufacturing are as follows: 1. The printing material is aluminum alloy. Its advantages are: (i) Light weight: The density of aluminum alloy is about 1 / 3 of that of cast iron, which can significantly reduce the weight of the engine and improve fuel economy. (ii) Good thermal conductivity: The thermal conductivity of aluminum alloy is better than that of cast iron, which can effectively reduce the working temperature of the engine and improve the thermal efficiency. (iii) Matching thermal expansion coefficient: The thermal expansion coefficient of aluminum alloy is similar to that of aluminum pistons, which can reduce the gap change caused by thermal expansion, reduce impact noise and oil consumption.

[0037] 2. Set the laser power. The power is 80 - 180 watts. The laser power determines the ability to melt metal powder. Too low power will result in insufficient melting and porosity; too high power may cause the "balling" effect and excessive melt pool expansion, resulting in a decrease in part dimensional accuracy. Set the spot size range to about 80 microns; the spot size affects the concentration of laser energy and the melt pool size, and thus affects the melting effect and printing accuracy. Set the scanning speed to 600 - 2000 mm / s; the scanning speed determines the residence time of the laser on the powder surface. Too fast speed will result in insufficient melting, and too slow speed will cause the melt pool to overheat and cause defects. Set the scanning line distance to 0.08 - 0.15 mm; the scanning line distance determines the overlap degree between adjacent scanning lines, affects the coverage of the melting area and the density of the part. Set the layer thickness to 20 - 50 microns; the layer thickness affects the penetration depth of laser energy and the printing resolution. The thinner the layer thickness, the higher the printing accuracy, but the printing time will increase. The particle size of the material powder is 20 - 53 microns; the powder particle size affects the powder spreading uniformity and melting effect. Finer powder helps to improve the surface finish, but may increase the risk of powder caking. The ambient temperature is about 80°C; an appropriate ambient temperature helps to reduce powder oxidation and moisture absorption and improve the printing quality.

[0038] 3. Heat treatment: After printing is completed, heat treatment is usually required. For example, the temperature is raised to 300 °C, held for two hours under an atmosphere protection condition, and then cooled in the furnace. Heat treatment can eliminate residual internal stress and improve the dimensional stability and mechanical properties of the parts.

[0039] In addition, post-treatment can be carried out on the surface of the manufactured lattice structure housing, such as sandblasting, polishing or coating treatment, to improve its wear resistance and corrosion resistance and extend its service life. Specifically, the sandblasting operation includes the following steps: I. Preparation work: 1. Clean the workpiece: Remove dirt and impurities on the workpiece surface, and physical cleaning, chemical treatment, solvent cleaning and other methods can be used. 2. Select equipment and materials: According to the characteristics of the workpiece and treatment requirements, select appropriate sandblasting materials (such as glass beads, alumina, etc.) and equipment (such as sandblasting machines, spray guns, etc.), and prepare personal protective equipment. 3. Surface treatment and cleaning: 4. Remove grease: Use chemical methods such as solvents, pickling, degreasing agents, etc. to remove grease. 5. Remove oxide layer and rust: Physical methods such as brushing, polishing, grinding, etc. can be used. II. Sandblasting operation: 1. Adjust equipment parameters: Pour abrasive into the sand tank, connect the air source, adjust the sandblasting pressure (generally controlled between 3-7 bar), and adjust the spraying angle and distance of the spray gun according to the shape of the workpiece. 2. Spray evenly: Aim at the workpiece surface, keep a uniform spraying speed and trajectory, and avoid over-sandblasting or missed spraying. 3. Follow-up treatment: 4. Clean up: After sandblasting is completed, clean the abrasive residues on the workpiece surface, and compressed air blowing or brushing can be used for cleaning. 5. Inspection: Check the sandblasting effect to ensure that the surface reaches the expected cleanliness and roughness.

[0040] The polishing operation includes the following steps: 1. Clean the workpiece: Clean the workpiece to remove dirt and grease on the surface, and solution cleaning or ultrasonic cleaning machines can be used. 2. Prepare tools and materials: Prepare a polishing machine, sandpaper (different grits), polishing paste, polishing cloth, etc. 3. Rough grinding: Select sandpaper, use coarser sandpaper (such as #400-#600), paste it on the grinding wheel of the polishing machine. Grind the surface, grind the workpiece surface to make it flat, and pay attention to controlling the speed and pressure of the polishing machine. Medium grinding, replace the sandpaper with medium-grit sandpaper (such as #800-#1000). Further grind, further grind the workpiece after rough grinding to make the surface smoother, and pay attention to the grinding direction and strength. Fine grinding, use a fine grinding wheel or polishing cloth: Carry out fine grinding to make the workpiece surface smoother, and different coarse and fine grinding wheels or abrasives can be selected according to needs. 4. Polishing: Use a polishing agent and a polishing cloth to polish the workpiece surface. The fine abrasives and chemical reagents in the polishing agent can further improve the surface finish and brightness. 5. Cleaning and drying: Clean the workpiece, wash the polished workpiece with clean water or solvent to remove the polishing agent and residues on the surface, and an ultrasonic cleaning machine can also be used for cleaning. Dry the workpiece, use equipment such as a hot air gun or an oven to dry the workpiece to avoid moisture retention.

[0041] The coating operation includes the following steps: 1. Preparation work: Cleaning the workpiece: Thoroughly clean the surface of the workpiece to remove impurities such as oil stains, rust, and dust. Solvent cleaning, mechanical grinding, etc. can be used. Preparing the coating material: According to the workpiece material and coating requirements, select a suitable coating material (such as paint, metal coating, etc.), and strictly mix it according to the operating procedures. Preparing the coating equipment: Prepare coating equipment such as spray guns, spray cabinets, and filters, and check the working status of the equipment. Surface pretreatment: 2. Grinding the surface: Use sandpaper or a grinding wheel to grind the surface to increase the adhesion of the coating. 3. Rust prevention treatment: Conduct rust prevention treatment on the metal surface to extend the life of the coating. 4. Coating construction: Primer spraying: Select a suitable type of primer according to needs and spray it on the surface. Pay attention to the distance and angle of the spray gun and maintain uniform spraying. Drying: Wait for the primer to dry completely. It can be dried naturally or in an oven. Topcoat spraying: Spray the color layer. Usually, multiple sprays are required to achieve the desired thickness and color. Wait for the previous layer to dry completely between each spray. Clear coat (optional): To increase gloss and protection, a clear coat can be sprayed on the topcoat. 5. Curing treatment: Natural drying: Place the sprayed product in a normal temperature environment and wait for the paint to dry naturally. However, the natural drying time is long and it is easily affected by environmental temperature and humidity. Oven drying: Place the workpiece in an oven and control the temperature for heating and drying. The commonly used temperature range is 60 - 150°C, and the time is adjusted according to the characteristics of the paint. Oven drying has high efficiency and stable coating quality. Infrared heating: Use infrared rays to heat the coating to accelerate the drying speed. It is suitable for mass production and rapid curing requirements, but the heating time and distance need to be controlled. 6. Surface finishing: Grinding: Use sandpaper or a grinding wheel to grind the coating surface to remove surface defects. Clean the surface after grinding. Polishing: Conduct polishing treatment on the coating surface to increase the surface gloss. A polishing machine and polishing paste can be used for uniform polishing to avoid over-polishing and damaging the coating. Touch-up spraying: Conduct touch-up spraying on the coating with local defects. Conduct local cleaning and grinding before touch-up spraying, and drying and curing are required after touch-up spraying.

[0042] The above is only the preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A cylinder, characterized in that: A cavity (101) is provided inside the wall of the cylinder (1), and through holes (102) are provided on both end faces of the cylinder (1), the through holes (102) being connected to the cavity (101), and the cavity (101) is filled with a first lattice layer (2), a third lattice layer (4) and a second lattice layer (3) in sequence from outside to inside along the radial direction of the cylinder (1), the porosity of the first lattice layer (2), the second lattice layer (3) and the third lattice layer (4) decreases in sequence, and the stiffness of the first lattice layer (2), the second lattice layer (3) and the third lattice layer (4) along the axial direction of the cylinder (1) increases in sequence.

2. The cylinder according to claim 1, characterized in that: The first lattice layer (2) is a tubular structure composed of a plurality of first lattice units (21), wherein the first lattice unit (21) is a simple cubic lattice unit structure; the second lattice layer (3) is a tubular structure composed of a plurality of second lattice units (31), wherein the second lattice unit (31) is a face-centered cubic lattice unit structure; and the third lattice layer (4) is a tubular structure composed of a plurality of third lattice units (41), wherein the third lattice unit (41) is a body-centered cubic lattice unit structure.

3. The cylinder according to claim 2, characterized in that: The porosity of the first lattice layer (2) is greater than 95%, the porosity of the second lattice layer (3) is 83% to 95%, and the porosity of the third lattice layer (4) is less than 83%.

4. A cylinder according to claim 2, characterized in that: The stiffness of the first lattice layer (2), the third lattice layer (4) and the second lattice layer (3) increases in sequence along the radial direction of the cylinder (1).

5. A cylinder according to claim 4, characterized in that: The first lattice unit (21) includes eight endpoints (211), the eight endpoints (211) are respectively located at eight tips of a cube, and every four of the endpoints (211) surround one face of the cube, and each endpoint (211) is connected to another endpoint (211) that is not adjacent to the face on which it is located, and surrounds a simple cube; The second lattice unit (31) includes eight endpoints (211) and six face centers (311), each face center (311) is located at the center of each face of the cube, and each face center (311) is simultaneously connected to the other three face centers (311) of the adjacent faces to form a birdcage structure, and the eight endpoints (211) are symmetrically connected to the center of the cube and connected to the birdcage structure to form a face-centered cube; The third lattice unit (41) includes eight endpoints (211) and a body center point (411), wherein the body center point (411) is located at the center of the cube, and each endpoint (211) is connected to another endpoint (211) that is not adjacent to the face on which it is located. The body center point (411) is simultaneously connected to the eight endpoints (211) to form a body-centered cube.

6. The cylinder according to claim 2, characterized in that: The cube side length of the first lattice unit (21) is 1 to 10 mm; the cube side length of the second lattice unit (31) is 2 to 8 mm; and the cube side length of the third lattice unit (41) is 3 to 6 mm.

7. A cylinder according to claim 2, characterized in that: A plurality of fins (5) are arranged on the outer peripheral wall of the cylinder (1) at intervals along its axial direction, and the fins (5) are a sheet-like structure composed of first lattice units (21).

8. A cylinder according to claim 7, wherein: A cylinder body (6) is simultaneously inserted through the middle parts of several of the fins (5). The cylinder body (6) is hollow and extends along the axial direction of the cylinder (1) at both ends.

9. A cylinder according to claim 1, wherein: The thickness of the third lattice layer (4) is the smallest.

10. An additive manufacturing method for a cylinder, characterized in that, A method for manufacturing a cylinder according to any one of claims 2 to 8, comprising the following steps: Step 1: Establish a model of the cylinder (1), and define the wall surface of the cylinder (1), the first lattice layer (2), the second lattice layer (3), the third lattice layer (4), and the transition regions of each part. Step 2: Determine the initial parameters of the thickness and porosity of the first lattice layer (2), the second lattice layer (3), and the third lattice layer (4), and determine the initial parameters of the cube side lengths of the first lattice unit (21), the second lattice unit (31), and the second lattice unit (31). Step 3: Perform stress analysis on the model using finite element analysis, determine the layout order of the first lattice layer (2), the second lattice layer (3), and the third lattice layer (4) according to the stress condition of the model, optimize the design parameters of the model, and then print the product according to the optimized model.

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