Additive manufacturing product and method of making

Abstract

This application relates to an additive manufacturing product and its preparation method, applying the field of metal additive manufacturing technology. The preparation method includes selective laser melting printing by controlling contour scanning parameters to ensure the original surface defect depth of the printed product is within a preset range; mechanical removal processing is then performed on the product to reduce the surface defect depth, with the material removal thickness being greater than or equal to the average defect layer depth; the contour scanning parameters include: 2 to 4 contour scanning passes, and an adjacent contour scanning spacing of 0.1 to 0.16 mm. This application achieves end-to-end surface quality control from pre-printing to post-processing by controlling the contour scanning parameters during the printing stage to ensure the original surface defect depth is within a preset range, and then performing mechanical removal processing with a removal thickness greater than or equal to the average defect layer depth. This matches the active control during the printing stage with the material removal thickness during mechanical removal.

Description

Technical Field

[0001] This application relates to the field of metal additive manufacturing technology, and in particular to an additive manufacturing product and its preparation method. Background Technology

[0002] Additive manufacturing (AM) technology, especially metal additive manufacturing technology represented by selective laser melting (SLM), can manufacture complex structural products that are difficult to achieve with traditional processes by stacking layers one by one, and has important application prospects in aerospace and other fields.

[0003] However, the inherent layer-by-layer melting and solidification characteristics of this process result in printed products commonly exhibiting defects such as high surface roughness, adhered unmelted powder, molten pool ripples, and step effects, severely impacting assembly accuracy and service reliability. Currently, existing technologies primarily rely on post-processing techniques such as sandblasting, polishing, and acid pickling to address these surface quality issues, but these methods still have limitations. Summary of the Invention

[0004] Therefore, it is necessary to address the shortcomings of existing additive manufacturing technologies by providing an additive manufacturing product and its preparation method.

[0005] In a first aspect, this application provides a method for preparing an additively manufactured product, comprising the following steps:

[0006] By controlling the contour scanning parameters for selective laser melting printing, the original surface defect depth of the printed product is kept within a preset range.

[0007] The product is subjected to mechanical removal treatment to reduce the depth of surface defects, wherein the material removal thickness of the mechanical removal treatment is greater than or equal to the average depth of the defect layer;

[0008] The contour scanning parameters include: the number of contour scanning channels is 2 to 4, and the spacing between two adjacent contour scanning channels is 0.1 to 0.16 mm.

[0009] In one embodiment, the product has a lower surface, a vertical surface, and a top surface, and the selective laser melting printing by controlling contour scanning parameters further includes: setting contour scanning parameters according to the product surface type.

[0010] The upper surface is laser-treated with a power of 130–170W and a scanning speed of 500–1000 mm / s.

[0011] For vertical surfaces, a laser power of 130–170W and a scanning speed of 500–1000 mm / s are used.

[0012] The lower surface uses a laser with a power of 90-120W and a scanning speed of 700-1200mm / s, and the scanning speed of the lower surface is higher than that of the upper surface and the vertical surface.

[0013] In one embodiment, the preset range of the original surface defect depth of the product is set to be less than or equal to 120 μm, and the original roughness Ra of the product is ≤11 μm.

[0014] In one embodiment, the mechanical removal process employs one or more of the following: wheel grinding, belt grinding, vibratory polishing, flexible abrasive polishing, and rotary grinding.

[0015] In one embodiment, the preparation method further includes sandblasting; the sandblasting medium is one or more of alumina, glass beads, and ceramic beads; the particle size of the medium is 100-220 mesh, the spraying pressure is 0.25-0.45 MPa, the spraying time is 2-8 min, and the spraying angle is 45-80°.

[0016] In one embodiment, the preparation method further includes a chemical homogenization treatment; the chemical homogenization treatment uses a low-concentration acidic homogenization solution, the low-concentration acidic homogenization solution having a pH value of 1-4, a total acid content of 3%-20%, a treatment time of 1-5 min, and a treatment temperature of 20-40°C; the acid in the low-concentration acidic homogenization solution includes one or more of nitric acid, citric acid, phosphoric acid, acetic acid, and oxalic acid.

[0017] In one embodiment, the preparation method further includes an electrochemical homogenization treatment; the voltage of the electrochemical homogenization treatment is 200-320V, the treatment time is 1-4min, and the treatment temperature is 40-80℃.

[0018] In one embodiment, the preparation method further includes: performing dimensional correction on the product; the dimensional correction is performed by one or more of CNC milling, finish milling or semi-finish milling, CNC grinding and light dressing cutting; the single cutting depth of the dimensional correction is 0.01 to 0.10 mm, the feed rate is 100 to 600 mm / min, and the spindle speed is 2000 to 8000 rpm.

[0019] In one embodiment, the preparation method further includes: performing a final surface treatment on the product; the final surface treatment includes one or more of cleaning treatment, passivation treatment, and protective treatment.

[0020] Secondly, this application provides an additive manufacturing product, which adopts the following technical solution:

[0021] An additive manufacturing product is prepared using the above-described preparation method.

[0022] The above-mentioned additive manufacturing product preparation method controls the contour scanning parameters during the printing stage to keep the original surface defect depth of the product within a preset range, and then performs mechanical removal processing with a removal thickness greater than or equal to the average depth of the defect layer. This matches the active control during the printing stage with the material removal thickness during mechanical removal processing, achieving full-process surface quality control from pre-printing to post-processing. Attached Figure Description

[0023] Figure 1 Comparison of the surface state of products prepared using the method provided in this application. Figure 1 The left side shows the surface condition after printing with improved contour parameters, while the right side shows the surface condition before improvement.

[0024] Figure 2 A magnified view of the depth of native surface defects in a product prepared using existing contour scanning parameters.

[0025] Figure 3 This is a magnified view of the depth of the original surface defects of the product obtained using the contour scanning parameters provided in this application.

[0026] Figure 4 The image shows the fluorescence test results of the product prepared by the method provided in Example 1.

[0027] Figure 5 The fluorescence test results of the product prepared by the existing technology are shown in the figure.

[0028] Figure 6 The image shows the fluorescence test results of the product prepared by the method provided in Example 2.

[0029] Figure 7 The image shows the fluorescence test results of the product prepared by the method provided in Example 3. Detailed Implementation

[0030] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application are described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0031] The civil aircraft industry has high requirements for the surface quality of metal additive manufacturing products, such as roughness, parallelism, flatness, and dimensional tolerances. In addition, there are certain requirements for non-destructive testing, such as fluorescence and X-ray analysis. However, due to the inherent characteristics of metal additive manufacturing, which involves layer-by-layer melting, the original surface often has high roughness, with issues such as incomplete molten powder adhesion, surface pits, and deep molten pool ripples. These defects can form a weak surface layer, affecting fatigue performance and service reliability. Furthermore, because metal additive manufacturing products often have extremely complex structures, frequently including irregularly shaped parts, the dimensional removal in thin-walled areas is limited, making it difficult to achieve an ideal surface finish through conventional machining and grinding methods.

[0032] To address the aforementioned issues, this application provides a method for preparing additive manufacturing products and the products prepared using this method. By controlling the depth of surface defects during the printing stage and employing matched mechanical removal, intermediate homogenization, and machining processes during the post-processing stage, stable control of the product's surface quality and dimensional accuracy is achieved. This allows products prepared using this method to meet dimensional tolerance requirements, non-destructive testing requirements, and aesthetic appeal.

[0033] The following is in conjunction with the appendix Figure 1-7 This application will be described in further detail.

[0034] In some embodiments, this application provides a method for preparing an additively manufactured product, the method comprising the following steps:

[0035] Step S100: Selective laser melting printing is performed by controlling the contour scanning parameters so that the original surface defect depth of the printed product is within a preset range;

[0036] Step S200: Perform mechanical removal treatment on the product to reduce the depth of surface defects. The material removal thickness of the mechanical removal treatment is greater than or equal to the average depth of the defect layer.

[0037] In step S100, the control of contour scanning parameters includes controlling the number of contour scanning channels, energy density, scanning speed and scanning spacing, so that the depth of the original surface defects of the printed part is controlled within a preset range, and the height of molten pool ripples and attached powder is reduced, thereby reducing surface roughness.

[0038] In an exemplary embodiment, in the above-described selective laser melting printing by controlling contour scanning parameters, the contour scanning parameters are specifically:

[0039] The number of contour scan tracks is 2 to 4;

[0040] The spacing between adjacent contour scans is 0.10–0.16 mm.

[0041] In the above embodiments, the number of contour scanning channels can be 2, 3, or 4, etc., including but not limited to the listed values, and other unlisted values ​​within the range are also applicable; the spacing between adjacent contour scans can be 0.10mm, 0.11mm, 0.12mm, 0.13mm, 0.14mm, 0.15mm, or 0.16mm, etc., including but not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0042] In some other embodiments, the product includes a lower surface, a vertical surface, and a top surface formed sequentially. The aforementioned selective laser melting printing by controlling contour scanning parameters further includes setting the contour scanning parameters according to the product surface type.

[0043] The upper surface is laser-treated with a power of 130–170W and a scanning speed of 500–1000 mm / s.

[0044] For vertical surfaces, a laser power of 130–170W and a scanning speed of 500–1000 mm / s are used.

[0045] The lower surface uses a laser with a power of 90-120W and a scanning speed of 700-1200mm / s, and the scanning speed of the lower surface is higher than that of the upper surface and the vertical surface.

[0046] In the above embodiments, the laser power used on the upper surface can be 130W, 140W, 150W, 160W or 170W, etc. The laser power used on the upper surface includes, but is not limited to, the listed values, and other values ​​not listed within the value range are also applicable; the scanning speed used on the upper surface can be 500mm / s, 600mm / s, 700mm / s, 800mm / s, 900mm / s or 1000mm / s, etc. The scanning speed used on the upper surface includes, but is not limited to, the listed values, and other values ​​not listed within the value range are also applicable.

[0047] The laser power used on the vertical surface can be 130W, 140W, 150W, 160W, or 170W, etc. The laser power used on the vertical surface includes, but is not limited to, the listed values, and other unlisted values ​​within the range of laser power used on the vertical surface are also applicable; the scanning speed used on the vertical surface can be 500mm / s, 600mm / s, 700mm / s, 800mm / s, 900mm / s, or 1000mm / s, etc. The scanning speed used on the vertical surface includes, but is not limited to, the listed values, and other unlisted values ​​within the range of values ​​are also applicable.

[0048] It should be noted that the vertical surface and the upper surface shown in this application are both non-supported contact surfaces. The above-mentioned parameter combination is mainly used to control the stability of the molten pool, reduce spherical particles, adhering powder and molten pool ripples on the product surface, and reduce the depth of surface defects of the product.

[0049] The laser power used on the lower surface can be 90W, 100W, 110W, or 120W, etc., and the laser power used on the lower surface includes, but is not limited to, the listed values; other values ​​not listed within the range are also applicable. The scanning speed used on the lower surface can be 700mm / s, 800mm / s, 900mm / s, 1000mm / s, 1100mm / s, or 1200mm / s, etc., and the scanning speed used on the lower surface includes, but is not limited to, the listed values; other values ​​not listed within the range are also applicable. This parameter combination is used to improve the surface quality after support removal and reduce porosity and unfused areas.

[0050] It should be noted that, in this embodiment, the contour scanning parameters of the upper and lower surfaces are not aimed at the end face positions of the upper and lower surfaces, but rather at the outer contours of the upper and lower surfaces. The vertical surface is actually the end face formed by several outer contours during the multi-layer printing process, so the contour scanning parameters of the vertical surface are aimed at the end face position of the final formed vertical surface.

[0051] Furthermore, as mentioned above, although the upper surface and the vertical surface have different geometric orientations, they are both non-lower surfaces and non-support contact surfaces in this application. Their main defect control objectives are to reduce the depth of molten pool ripples, spherical particles, adhering powder, and surface pits. Experimental verification has shown that using the same or similar contour scanning power and scanning speed windows for both the upper and vertical surfaces can control the surface defect depth within the target range. Therefore, in this application, both are set to the same parameter range, and the preferred values ​​in specific embodiments are used to adapt to different product structures and surface conditions. The lower surface is more significantly affected by support, overhanging formation, and heat accumulation; therefore, a separate parameter window with relatively low power and a higher scanning speed is used.

[0052] It should be noted that, in the embodiments of this application, surface defects refer to geometric discontinuities such as pits, burrs, grooves caused by unfused powder, protrusions formed by powder agglomeration, and surface ripples on the outer surface of the product after additive manufacturing. These defects can form indicators in subsequent non-destructive testing (such as fluorescent penetrant testing) or become stress concentration sources under fatigue loads.

[0053] Surface defect depth (denoted as D) refers to the normal distance from the outermost envelope surface of the product's outer surface (a reference surface fitted with a local datum surface) to the deepest depression / defect root within a specified measurement area. When the surface defect manifests as a groove / unfused notch, the surface defect depth is taken as the maximum normal distance from the bottom of the groove relative to the reference surface. The original surface defect depth of the product refers to the surface defect depth of the product after printing, before any mechanical removal processing.

[0054] In an exemplary embodiment, the preset range of the original surface defect depth of the above-mentioned product is set to be less than or equal to 120 μm. Preferably, the preset range is 100–120 μm. The surface defect depth can be 100 μm, 110 μm, 120 μm, etc., including but not limited to the listed values. Other unlisted values ​​within the range are also applicable. In this embodiment, the original roughness Ra of the printed product is ≤11 μm. The original roughness can be 11 μm, 10 μm, 9 μm, or 8 μm, etc., including but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0055] In the above embodiments, the defect depth on the product surface can be measured using any of the following methods, and the three methods are considered equivalent in this application. Preferably, three-dimensional surface topography measurement is used to obtain statistically significant results. .

[0056] Method A: 3D optical profilometry / white light interferometry / confocal scanning. Specifically, this involves acquiring a 3D surface point cloud / height matrix within a specified measurement area, fitting a local reference surface (such as a least-squares plane / quadratic surface), and calculating the normal distance D between the deepest valley value within that area and the reference surface. The set of D is obtained at multiple sampling locations, and then calculated... .

[0057] Method B: Cross-sectional metallography. Specifically, this involves preparing a cross-section perpendicular to the surface at a designated location, identifying the deepest depression / defect root under a microscope, and measuring its distance to a reference profile as D. Suitable for verification measurements and process window calibration.

[0058] Method C: Industrial CT measurement. Specifically, this refers to performing high-resolution CT scans on the surface area and reconstructing the surface / near-surface defect morphology, extracting the depth D of the deepest defect. It is suitable for complex internal and external surfaces or areas difficult to sample. It should be noted that when the defect is mainly a protrusion (with attached powder), the maximum peak height Rp or peak-valley height Rz can be recorded simultaneously as supplementary indicators; in this application, the determination of "removal of the defect layer" is based on D or... As the standard.

[0059] In the above embodiments, the surface roughness of the product can be measured using either a contact profilometer or a non-contact optical roughness meter. Preferably, Ra is measured in multiple directions (e.g., along the scanning direction and perpendicular to the scanning direction) on the same surface area, and the average value or the value of the less favorable direction is taken as the judgment criterion. The sampling length, evaluation length, and filtering settings should be consistent across the same batch of test pieces. If different instruments are used, the instrument type and settings should be specified in the description to ensure comparability.

[0060] It should be noted that, in order to facilitate understanding of the present invention and to ensure that the process window is verifiable and reproducible, unless otherwise stated, all the above measurements are performed on the same batch of test pieces and the same surface area using the same method.

[0061] See Figure 1 As shown, Figure 1 The left side shows the product prepared using the contour scanning parameters of this application, and the right side shows the product prepared using the contour scanning parameters of the prior art. It can be clearly seen that the product prepared using the method of this application has a smoother surface and significantly reduced molten pool ripples, burrs and unmelted powder particles.

[0062] Combination Figure 2 and Figure 3 As shown, Figure 2 A magnified view of the depth of native surface defects in a product prepared using existing contour scanning parameters. Figure 3 This is a magnified view of the depth of native surface defects in a product obtained using the contour scanning parameters provided in this application. Figure 2 The product shown has burrs and pits that are approximately 154 μm deep from the surface, and the original surface roughness Ra is between 11 and 15 μm. Figure 3 The product shown has burrs and pits that are approximately 105 μm deep from the surface, and the original surface roughness Ra is between 8 and 11 μm.

[0063] In step S200, the defect layer refers to the material layer region inward from the original surface of the product, containing the influence of the aforementioned surface defects, and its characteristic depth can be characterized by the measured surface defect depth. The average depth of the defect layer (calculated as...) () refers to the arithmetic mean of the surface defect depths measured within a specified number of sampling points and sampling length.

[0064] The aforementioned weak surface layer refers to a material layer region on the original surface that is relatively more likely to expose defects during loading or testing due to factors such as lack of fusion, surface roughness peaks and valleys, adhering powder, or microcracks / micropores. In engineering evaluation, weak surface layers and defect layers can be considered equivalent or highly correlated.

[0065] The aforementioned material removal thickness refers to the thickness of material removed from the original surface by mechanical methods such as machining, grinding, belt abrasion, or vibratory polishing (characterized by equivalent thickness in the normal direction). When grinding / polishing is used, it is calculated by subtracting the difference in geometric dimensions or cross-sectional measurements at the same measurement location before and after the process. In this application, the material removal thickness is set to be greater than or equal to the average depth of the defect layer to reduce the impact of surface defects and improve the surface condition.

[0066] In this embodiment, the material removal thickness can be measured using at least one of the geometric dimension method and the cross-sectional method, with the geometric dimension method being preferred. The geometric dimension method uses a coordinate measuring machine (CMM), laser scanner, or outside micrometer to measure the dimensional difference at the same location before and after treatment under the same reference system and convert it into the equivalent removal thickness in the normal direction. When using the cross-sectional method, comparative cross-sections are prepared before and after treatment, and the removal thickness is obtained by measuring the surface position change using a microscope.

[0067] Furthermore, in steps S100 and S200 above, when selecting the measurement area, at least three representative areas that are spaced apart from each other are selected within the same type of surface (such as the upper surface / vertical surface / lower surface); if the product has critical free surfaces and critical mating surfaces, samples can be taken separately.

[0068] Specifically, at least n defect depth values ​​D are obtained for each region, preferably n≥10; the average defect depth of the region is calculated. _region; then average the values ​​of multiple regions to obtain the surface type. This application specifies that when "the material removal thickness is not less than the average depth of the defect layer," the total material removal thickness is equal to the average depth of the defect layer on that type of surface. Comparisons should be made. Furthermore, validation within the same process window should include at least three test specimens or three repeated measurements of the same test specimen in three different areas to eliminate random errors.

[0069] In one exemplary embodiment, the above-described mechanical removal process on the product employs one or more of the following: grinding wheel abrasion, belt abrasion, vibratory polishing, or flexible abrasive polishing. This mechanical removal process significantly reduces the depth of surface pits and eliminates adhering powder, providing a uniform surface for subsequent intermediate homogenization processes. After mechanical removal, the surface roughness of the product can be reduced to Ra ≤ 8 μm.

[0070] The process parameters for mechanical removal are as follows:

[0071] The abrasive grit size is 80-240 mesh. The abrasive grit size can be 80 mesh, 90 mesh, 100 mesh, 110 mesh, 120 mesh, 130 mesh, 140 mesh, 150 mesh, 160 mesh, 170 mesh, 180 mesh, 190 mesh, 200 mesh, 210 mesh, 220 mesh, 230 mesh or 240 mesh, etc., including but not limited to the listed values. Other values ​​within the range that are not listed are also applicable.

[0072] The grinding speed is 1000 to 6000 rpm. The grinding speed can be 1000 rpm, 2000 rpm, 3000 rpm, 4000 rpm, 5000 rpm or 6000 rpm, etc., including but not limited to the listed values. Other values ​​not listed within the range are also applicable.

[0073] The contact pressure is 0.02 to 0.10 MPa, and the contact pressure can be 0.02 MPa, 0.03 MPa, 0.04 MPa, 0.05 MPa, 0.06 MPa, 0.07 MPa, 0.08 MPa, 0.09 MPa or 0.10 MPa, etc., including but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0074] The thickness removed in a single pass is 0.05 to 0.20 mm. The thickness removed in a single pass can be 0.05 mm, 0.06 mm, 0.07 mm, 0.08 mm, 0.09 mm, 0.10 mm, 0.11 mm, 0.12 mm, 0.13 mm, 0.14 mm, 0.15 mm, 0.16 mm, 0.17 mm, 0.18 mm, 0.19 mm, or 0.20 mm, etc., including but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0075] In another exemplary embodiment, the mechanical removal process is performed using a rotary grinding head, which includes one or more of carbide grinding heads, diamond grinding heads, and resin grinding heads. The grinding grit or equivalent grinding grit of the rotary grinding head is 240–400 mesh, specifically 240 mesh, 280 mesh, 300 mesh, 320 mesh, 350 mesh, 380 mesh, or 400 mesh, etc., including but not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0076] Among them, carbide grinding heads are used to remove support connection residues, burrs, and large local protrusions; diamond grinding heads are used to remove surface-adhered powder, molten pool protrusions, and interlayer step peaks; resin grinding heads are used to repair grinding marks formed by carbide or diamond grinding heads and further reduce surface roughness.

[0077] For the upper surface of the product, it is preferable to use a 320-400 grit diamond grinding head or resin grinding head for light grinding; for the vertical surface, it is preferable to use a 240-320 grit carbide grinding head or diamond grinding head for main grinding, and then use a 400 grit resin grinding head for fine finishing; for the lower surface, it is preferable to first use a 240 grit carbide grinding head to remove the support connection residue and local protrusions, then use a 240-320 grit diamond grinding head for main grinding, and finally use a 400 grit resin grinding head for fine finishing.

[0078] The rotary grinding head operates at a speed of 2000–5000 rpm, a contact pressure of 0.02–0.10 MPa, and a feed rate of 100–300 mm / min. The surface roughness Ra of the product after mechanical grinding is 1.5–3.0 μm, preferably 1.8–2.2 μm, and more preferably approximately 2.0 μm.

[0079] Furthermore, in some other embodiments, after the initial mechanical removal process is completed, in order to eliminate localized machining marks caused by mechanical removal and further reduce surface roughness, making the product surface more uniform, the above-mentioned preparation method further includes:

[0080] Step S300: Perform intermediate homogenization treatment on the product. The intermediate homogenization treatment includes sandblasting, and one or more of chemical homogenization and electrochemical homogenization treatments. Among them, sandblasting is a necessary step and must be performed before chemical homogenization or electrochemical homogenization treatment.

[0081] In one exemplary embodiment, the process parameters for sandblasting are:

[0082] The sandblasting medium is one or more of alumina, glass beads and ceramic beads. By using the micro-cutting and hammering effect generated by the medium impacting the product surface at high speed under the drive of compressed air, the surface morphology after mechanical removal can be homogenized and residual micro-protrusions can be removed.

[0083] The particle size of the medium is 100 to 220 mesh. The particle size of the medium can be 100 mesh, 120 mesh, 140 mesh, 160 mesh, 180 mesh, 200 mesh or 220 mesh, etc., including but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0084] The injection pressure is 0.25 to 0.45 MPa. The injection pressure can be 0.25 MPa, 0.30 MPa, 0.35 MPa, 0.40 MPa or 0.45 MPa, etc., including but not limited to the listed values. Other values ​​not listed within the range are also applicable.

[0085] The spraying time is 2 to 8 minutes. The spraying time can be 2 minutes, 3 minutes, 4 minutes, 5 minutes, 6 minutes, 7 minutes or 8 minutes, etc., including but not limited to the listed values. Other values ​​not listed within the range are also applicable.

[0086] The spray angle is 45° to 80°. The spray angle can be 45°, 50°, 55°, 60°, 65°, 70°, 75° or 80°, etc., including but not limited to the listed values. Other values ​​not listed within the range are also applicable.

[0087] In one exemplary embodiment, a light chemical treatment may be performed after sandblasting to remove minor surface protrusions and micro-damaged edges, reducing localized notch effects. Specifically, the light chemical treatment may involve chemical homogenization of the sandblasted product, with the following process parameters:

[0088] Chemical homogenization treatment using a low-concentration acidic homogenizing solution is employed to remove minor surface protrusions and micro-damaged edges, reducing localized notch effects. This treatment aims to homogenize and refine the surface, rather than removing deep corrosion. In this application, the acid in the low-concentration acidic homogenizing solution includes one or more of nitric acid, citric acid, phosphoric acid, acetic acid, and oxalic acid.

[0089] The pH value of the low-concentration acidic homogenization solution is 1 to 4, preferably 1.5 to 3.5; the pH value can be selected from 1, 1.5, 2, 2.5, 3, 3.5 or 4, etc., including but not limited to the listed values, and other values ​​not listed within the range are also applicable.

[0090] The total acid content of the low-concentration acid homogenization solution is 3% to 20%, and the total acid content can be 3%, 5%, 7%, 9%, 11%, 13%, 15%, 17%, 19%, or 20%, etc., including but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0091] The processing time is 1 to 5 minutes, and the processing time can be 1 minute, 2 minutes, 3 minutes, 4 minutes or 5 minutes, etc., including but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0092] The processing temperature is 20 to 40°C. The processing temperature can be 20°C, 25°C, 30°C, 35°C or 40°C, etc., including but not limited to the listed values. Other values ​​not listed within the range are also applicable.

[0093] Preferably, the low-concentration acidic homogenization solution includes 5%–10% (volume fraction) nitric acid, 1%–3% citric acid, and the remainder is deionized water. The treatment temperature is 20–40°C, and the treatment time is 1–5 min.

[0094] In this embodiment, the thickness removed by chemical homogenization is controlled within the range of 0.01 to 0.05 mm to avoid excessive changes in product size.

[0095] In one exemplary embodiment, an electrochemical homogenization treatment can be performed after sandblasting. Specifically, electrochemical polishing can be used as a homogenization method to further improve the surface microstructure. In this embodiment, the process parameters for the electrochemical homogenization treatment are as follows:

[0096] The voltage for electrochemical homogenization treatment is 200–320V. The voltage can be 200V, 220V, 240V, 260V, 280V, 300V, or 320V, etc., including but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0097] The processing time is 1 to 4 minutes, and the processing time can be 1 minute, 2 minutes, 3 minutes or 4 minutes, etc., including but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0098] The processing temperature is 40 to 80°C. The processing temperature can be 40°C, 50°C, 60°C, 70°C or 80°C, etc., including but not limited to the listed values. Other values ​​within the range that are not listed are also applicable.

[0099] In summary, the intermediate homogenization treatment described in this application refers to a finishing step that, after the main mechanical removal process, uses methods such as sandblasting, chemical or electrochemical polishing, or light grinding to homogenize the microscopic peaks and valleys on the product surface and reduce processing marks and microscopic spikes. The characteristic of homogenization finishing is that the removal thickness is less than the main mechanical removal thickness; its purpose is to improve surface morphology consistency and inspection friendliness, rather than to perform the main removal function.

[0100] In this embodiment, the thickness removed by the intermediate homogenization process should be less than the thickness removed by the mechanical process in order to control product size changes and ensure that the intermediate homogenization process mainly undertakes the function of surface homogenization and finishing, rather than the main function of material removal.

[0101] In other embodiments, the above-described method for preparing additively manufactured products further includes:

[0102] Step S400: Perform dimensional correction on the product.

[0103] In this application, dimensional correction processing is used to perform machining correction on critical areas of the product after intermediate homogenization processing to ensure structural dimensional accuracy and avoid excessive thickness removal in post-processing that could affect structural safety. It should be noted that machining correction processing is preferentially applied to critical dimensional areas of the product, including but not limited to assembly surfaces, connection holes, contact surfaces, or design-specified reference areas.

[0104] In one exemplary embodiment, the dimensional correction process employs one or more combinations of CNC milling, finish milling or semi-finish milling, CNC grinding, and light dressing cutting, preferably using shallow depth-of-cut CNC milling or grinding to avoid creating new machining marks. Preferably, the thickness removed by the dimensional correction process is less than the thickness removed by the mechanical removal process.

[0105] In this embodiment of the application, the process parameters for the size correction process are as follows:

[0106] The depth of cut in a single pass is 0.01 to 0.10 mm. The depth of cut in a single pass can be 0.01 mm, 0.03 mm, 0.05 mm, 0.07 mm, or 0.10 mm, etc., including but not limited to the listed values. Other values ​​not listed within the range are also applicable.

[0107] The feed rate is 100 to 600 mm / min. The feed rate can be 100 mm / min, 200 mm / min, 300 mm / min, 400 mm / min, 500 mm / min or 600 mm / min, etc., including but not limited to the listed values. Other values ​​not listed within the range are also applicable.

[0108] The spindle speed is 2000 to 8000 rpm. The spindle speed can be 2000 rpm, 3000 rpm, 4000 rpm, 5000 rpm, 6000 rpm, 7000 rpm or 8000 rpm, etc., including but not limited to the listed values. Other values ​​within the range that are not listed are also applicable.

[0109] After dimensional correction, the residual roughness of the product surface is controlled to Ra≤6μm. The residual roughness can be 6μm, 5μm or 4μm, etc., including but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0110] In other embodiments, the above-described method for preparing additively manufactured products further includes:

[0111] Step S500: Perform final surface treatment on the product.

[0112] In this application, the product undergoes a final surface treatment, including one or more of cleaning, passivation, and protective treatments, to bring the product surface to the required service condition.

[0113] In one exemplary embodiment, the cleaning process is used to remove machining residues, sandblasting media residues, and chemical treatment residues. Through cleaning, surface contaminants can be effectively removed, improving surface cleanliness. In this application, the cleaning method includes one or more of ultrasonic cleaning, spray cleaning, and immersion cleaning, with ultrasonic cleaning being preferred. The process parameters for ultrasonic cleaning are as follows:

[0114] The cleaning medium is deionized water or neutral cleaning solution;

[0115] The ultrasonic frequency is 20 to 40 kHz. The ultrasonic frequency can be 20 kHz, 30 kHz or 40 kHz, etc., including but not limited to the listed values. Other values ​​not listed within the range are also applicable.

[0116] The cleaning time is 5 to 15 minutes. The cleaning time can be 5 minutes, 6 minutes, 7 minutes, 8 minutes, 9 minutes, 10 minutes, 11 minutes, 12 minutes, 13 minutes, 14 minutes or 15 minutes, etc., including but not limited to the listed values. Other values ​​not listed within the range are also applicable.

[0117] The cleaning temperature is 20-50℃. The cleaning temperature can be 20℃, 30℃, 40℃ or 50℃, etc., including but not limited to the listed values. Other values ​​not listed within the range are also applicable.

[0118] In one exemplary embodiment, passivation is performed after cleaning the product to stabilize the surface chemical state and improve corrosion resistance. In this application, passivation forms a stable surface film, reducing the risk of corrosion in the service environment. The passivation process parameters are as follows:

[0119] An acidic passivation solution is used, wherein the acid in the acidic passivation solution includes one or more of nitric acid, citric acid, phosphoric acid, and acetic acid;

[0120] The total acid content is 2% to 15% (volume fraction), with the balance being deionized water. The total acid content can be 2%, 5%, 7%, 9%, 11%, 13%, or 15%, etc., including but not limited to the listed values. Other unlisted values ​​within this range also apply.

[0121] The passivation time is 3 to 10 minutes. The passivation time can be 3 minutes, 4 minutes, 5 minutes, 6 minutes, 7 minutes, 8 minutes, 9 minutes or 10 minutes, including but not limited to the listed values. Other values ​​not listed within the range are also applicable.

[0122] The passivation temperature is controlled between 20 and 40°C. The passivation temperature can be 20°C, 30°C, or 40°C, including but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0123] In another exemplary embodiment, a corrosion inhibitor or surfactant may be further added to the acidic passivation solution to improve the uniformity of the passivation film.

[0124] In one exemplary embodiment, a protective treatment can be applied to the product after passivation to prevent surface degradation during transportation or storage. In this embodiment, the protective treatment includes one or more of the following: protective oil coating, temporary sealing protection, and anti-corrosion coating treatment.

[0125] The technical solution claimed in this application will be described in detail below with reference to specific embodiments:

[0126] Example 1

[0127] This embodiment provides a method for preparing additively manufactured products, using a titanium alloy structural part formed by selective laser melting as the preparation object. Specifically, the method uses a Ti-6Al-4V titanium alloy additively manufactured product formed by selective laser melting as the object, employing a coordinated control method of printing-mechanical removal-surface homogenization-dimensional correction-final surface treatment for product preparation, illustrating the preferred combination of process parameters in this application. The preparation method includes the following steps:

[0128] Preparation of the original product: The product is printed using SLM additive manufacturing technology. During the printing process, the number of contour scanning channels is controlled to be 2, and the scanning interval is 0.12mm for selective laser melting printing, thereby obtaining the original product.

[0129] The laser power used for preparing the upper surface of the product was 150W and the scanning speed was 800mm / s; the laser power used for preparing the vertical surface of the product was 150W and the scanning speed was 850mm / s; and the laser power used for preparing the lower surface of the product was 110W and the speed was 1000mm / s. The overall original surface roughness Ra of the printed product was ≤9μm, and the average depth of surface defects was 110μm.

[0130] After printing, a three-dimensional optical profilometer is used to select no less than three representative areas on the upper surface, vertical surface and lower surface to measure the surface morphology. No less than 10 defect depth values ​​are obtained in each area, and the average depth of the defect layer is calculated. A contact profilometer is used to measure the original surface roughness of the product.

[0131] Mechanical removal treatment is applied to the product: a combination of vibratory polishing and localized belt abrasion is used to reduce the depth of surface defects. The material removal thickness is greater than or equal to the average depth of the defect layer. The process parameters for mechanical removal are: abrasive grit size of 120 mesh, grinding speed of 3000 rpm, contact pressure of 0.05 MPa, and single-pass removal thickness of 0.10 mm. After mechanical removal treatment, the surface roughness Ra of the product is reduced to 7 μm.

[0132] Intermediate homogenization treatment was performed on the product: a combination of sandblasting and chemical homogenization was used to further refine the surface of the product after mechanical removal, thereby stabilizing the surface condition and improving the consistency of post-processing. The sandblasting process parameters were as follows: glass beads were used as the blasting medium, with a particle size of 150 mesh, a blasting pressure of 0.35 MPa, a blasting angle of 60°, and a blasting time of 5 min. The chemical homogenization process parameters were as follows: a low-concentration acidic homogenization solution was used, containing 7% (volume fraction) nitric acid and 2% (volume fraction) citric acid, with the remainder being deionized water, a treatment time of 3 min, and a treatment temperature of 25°C. After intermediate homogenization, the surface roughness Ra of the product was reduced to 5 μm.

[0133] Dimensional correction was performed on the product: Connecting holes and assembly surfaces were precision milled to ensure structural dimensional accuracy. The process parameters for dimensional correction were: depth of cut 0.04 mm, feed rate 300 mm / min, and spindle speed 4500 rpm. After processing, key dimensions met design requirements, and no new deep-machining marks were created on the surface.

[0134] Final surface treatment of the product: The product undergoes ultrasonic cleaning and passivation. The ultrasonic cleaning frequency is 30kHz, the cleaning time is 10 minutes, and the cleaning temperature is 30℃. Subsequently, an acidic passivation solution is used for passivation treatment, with a passivation time of 5 minutes and a passivation temperature of 25℃.

[0135] The final product was subjected to fluorescence detection, and the fluorescence detection results are as follows: Figure 4 As shown, the product's dimensions meet processing requirements and its surface uniformity is good, indicating that the additive manufacturing method claimed in this application can stably control the surface state of the additive product.

[0136] Comparative Example 1:

[0137] This comparative example uses the same equipment, Ti-6Al-4V titanium alloy powder, product structure, and other printing parameters as Example 1, except for the contour scanning parameters and post-processing.

[0138] Printing was performed using standard contour scanning parameters, with two contour scans and a 0.10mm spacing between adjacent scans. The laser power for the upper and vertical surfaces was 150W, and the scanning speed was 1250mm / s; the laser power for the lower surface was 100W, and the scanning speed was also 1250mm / s. After printing, the maximum defect depth on the printed surface was measured to be approximately 154μm, and the original surface roughness Ra was 11–15μm. The surface cross-sectional morphology is shown below. Figure 2 As shown.

[0139] After printing, mechanical grinding was performed using 120-grit sandpaper at a speed of 3000 rpm and a contact pressure of 0.05 MPa, resulting in a total material removal thickness of 0.10 mm. Subsequently, chemical treatment was performed using the same low-concentration acidic homogenization solution as in Example 1, with a treatment time of 3 min and a treatment temperature of 25°C. No sandblasting was performed.

[0140] The treated product was subjected to fluorescence penetration testing, and the test results are as follows: Figure 5 As shown. Compared with the detection results of Example 1, the comparative example product showed more fluorescence indication on its surface, indicating that the contour scanning parameters and the combined treatment method of mechanical removal, sandblasting and chemical homogenization used in this application are beneficial to reducing the depth of surface defects and improving the surface condition and non-destructive testing adaptability of the product.

[0141] Example 2

[0142] This application provides a method for preparing additively manufactured products, using a complex thin-walled product with a minimum wall thickness of 1.2 mm as the preparation target. The preparation method includes the following steps:

[0143] Preparation of the original product: Unlike Example 1, this embodiment employs a strategy of reducing the energy input to the lower surface. Specifically, the laser power used for preparing the upper surface of the product was 140W, and the scanning speed was 900mm / s; the laser power used for preparing the vertical surface of the product was 145W, and the scanning speed was 900mm / s; the laser power used for preparing the lower surface of the product was 100W, and the scanning speed was 1100mm / s. After printing, the original surface defect depth of the printed product was measured to be 100μm, and the original roughness Ra was 10μm.

[0144] Mechanical removal was performed on the product: Vibratory polishing was used to reduce the depth of surface defects. The abrasive particle size was 180 mesh, the vibration frequency was 50 Hz, the amplitude was 2 mm, the processing time was 10 min, and the total material removal thickness was 0.11 mm. After mechanical removal, the surface roughness Ra of the product was reduced to 7.5 μm.

[0145] Intermediate homogenization treatment of the product: A combination of sandblasting and electrochemical homogenization treatment was used. The sandblasting process parameters were: ceramic beads as the blasting medium, a particle size of 180 mesh, a blasting pressure of 0.28 MPa, a blasting angle of 60°, and a blasting time of 3 min. The electrochemical homogenization process parameters were: a treatment voltage of 260 V, a treatment time of 2 min, and a treatment temperature of 60 °C. After intermediate homogenization treatment, the surface roughness Ra of the product was reduced to 5.5 μm. Dimensional correction treatment of the product: Unlike Example 1, this application only performs light grinding on the reference surface of the product, with a single grinding depth of 0.02 mm, a table feed speed of 200 mm / min, and a grinding wheel spindle speed of 3000 rpm. Final surface treatment of the product: The product undergoes cleaning and passivation treatment, with passivation mainly achieved through a citric acid system.

[0146] The final product was subjected to fluorescence detection, and the fluorescence detection results are as follows: Figure 6 As shown, the product surface after final surface treatment has no obvious processing marks, and the thin-walled dimensions are stable.

[0147] Example 3

[0148] This application provides a method for manufacturing additively manufactured products, using connectors with strict dimensional tolerances as the manufacturing object. The method includes the following steps:

[0149] Preparation of the original product: Unlike Example 1, this application employs a strategy to improve contour stability. Specifically, the laser power used for preparing the upper surface of the product was 160W, and the scanning speed was 700mm / s; the laser power used for preparing the vertical surface of the product was 155W, and the scanning speed was 750mm / s; the laser power used for preparing the lower surface of the product was 110W, and the scanning speed was 950mm / s. After printing, the original surface defect depth of the printed product was measured to be 120μm, and the original roughness Ra was 11μm.

[0150] Mechanical removal of the product: The depth of surface defects is reduced by fine grinding with 150-grit abrasive belt. The grinding speed is 4000 rpm, the contact pressure is 0.06 MPa, and the total material removal thickness is 0.12 mm. After mechanical removal, the surface roughness Ra of the product is reduced to 6.5 μm.

[0151] Intermediate homogenization treatment was performed on the product: a combination of sandblasting and chemical homogenization was used to further refine the surface of the product after mechanical removal, thereby stabilizing the surface condition and improving the consistency of post-processing. The sandblasting process parameters were as follows: 180-mesh alumina was used as the sandblasting medium, the blasting pressure was 0.40 MPa, the blasting angle was 70°, and the blasting time was 6 min. The chemical homogenization process parameters were as follows: a low-concentration acidic homogenization solution was used, containing 5% (volume fraction) phosphoric acid and 1.5% (volume fraction) citric acid, with the remainder being deionized water, a treatment time of 4 min, and a treatment temperature of 30°C. After intermediate homogenization, the surface roughness Ra of the product was reduced to 4.5 μm.

[0152] Dimensional correction of the product: Precision milling is performed on key areas of the product to ensure structural dimensional accuracy. The process parameters for dimensional correction are: single cutting depth of 0.05mm, feed rate of 400mm / min, and spindle speed of 6000rpm.

[0153] Final surface treatment of the product: The product is sequentially cleaned, passivated, and sealed with protective oil.

[0154] The final product was subjected to fluorescence detection, and the fluorescence detection results are as follows: Figure 7 As shown, the product has a high dimensional compliance rate and good surface uniformity, and can pass non-destructive testing.

[0155] Example 4

[0156] This embodiment provides a method for preparing additively manufactured products, illustrating the lower end values ​​of the process parameter ranges in this application. This embodiment focuses on Ti-6Al-4V titanium alloy additively manufactured products formed by selective laser melting, employing a collaborative control method of printing-mechanical removal-surface homogenization-dimensional correction-final surface treatment for product preparation. This preparation method includes the following steps:

[0157] Preparation of the original product: The product is printed using SLM additive manufacturing technology. During the printing process, the number of contour scanning channels is controlled to be 2, and the scanning interval is 0.10mm to perform selective laser melting printing, thereby obtaining the original product.

[0158] Specifically, the laser power used for preparing the upper surface of the product is 130W and the scanning speed is 500mm / s; the laser power used for preparing the vertical surface of the product is 130W and the scanning speed is 500mm / s; and the laser power used for preparing the lower surface of the product is 90W and the speed is 700mm / s.

[0159] After printing, the surface defect depth was measured using a 3D optical profilometer, and the original surface roughness Ra was measured using a contact profilometer. The measurements showed that the surface defect depth was controlled within the range of 100–120 μm, and the original surface roughness Ra was ≤11 μm.

[0160] Mechanical removal treatment is performed on the product: the depth of surface defects is reduced by belt abrasion. The abrasive grit size is 80 mesh, the abrasion speed is 1000 rpm, the contact pressure is 0.02 MPa, and the thickness removed in a single pass is 0.05 mm.

[0161] In this application, the material removal thickness is determined based on the average depth of the defect layer measured after printing, and meets the requirement of being not less than the average depth of the defect layer. After mechanical removal, powder adhering to the product surface, local burrs, and large ripples are removed, and the surface roughness of the product is reduced to Ra≤8μm.

[0162] Intermediate homogenization treatment is performed on the product: a combination of sandblasting and chemical homogenization is used to further refine the surface of the product after mechanical removal, thereby stabilizing the surface condition and improving the consistency of post-processing. The sandblasting process parameters are as follows: glass beads are used as the blasting medium, with a particle size of 100 mesh, a blasting pressure of 0.25 MPa, a blasting angle of 45°, and a blasting time of 2 minutes. The chemical homogenization process parameters are as follows: a low-concentration acidic homogenization solution is used, with a total acid content of 3% (volume fraction), the remainder being deionized water, a treatment time of 1 minute, and a treatment temperature of 20°C. This treatment is used to remove localized micro-protrusions and micro-processing traces left by mechanical removal. After intermediate homogenization, the surface roughness Ra of the product is reduced to 7 μm.

[0163] Dimensional correction processing: This involves minor, localized adjustments to critical assembly surfaces or reference areas. The process parameters for dimensional correction are: depth of cut of 0.01 mm, feed rate of 100 mm / min, and spindle speed of 2000 rpm. This step is only used to ensure critical dimensional and reference accuracy and is not considered a primary surface removal process.

[0164] Final surface treatment of the product: The product is ultrasonically cleaned using deionized water as the cleaning medium at a frequency of 20 kHz for 5 minutes at a temperature of 20°C. Subsequently, the product undergoes passivation treatment for 3 minutes at a temperature of 20°C.

[0165] Testing revealed no obvious residual powder on the product surface, key dimensions met design requirements, and fluorescence detection showed no disallowable indications.

[0166] Example 5

[0167] This embodiment provides a method for preparing additively manufactured products, illustrating the high-end values ​​of various process parameters in this application. This embodiment focuses on Ti-6Al-4V titanium alloy additively manufactured products formed by selective laser melting, employing a collaborative control method of printing-mechanical removal-surface homogenization-dimensional correction-final surface treatment for product preparation. This preparation method includes the following steps:

[0168] Preparation of the original product: The product is printed using SLM additive manufacturing technology. During the printing process, the number of contour scanning channels is controlled to be 4, and the scanning interval is 0.16mm to perform selective laser melting printing, thereby obtaining the original product.

[0169] Specifically, the laser power used for preparing the upper surface of the product is 170W and the scanning speed is 1000mm / s; the laser power used for preparing the vertical surface of the product is 170W and the scanning speed is 1000mm / s; and the laser power used for preparing the lower surface of the product is 120W and the speed is 1200mm / s.

[0170] After printing, three-dimensional surface morphology data are acquired using a white light interferometer or confocal microscope, and the surface defect depth is calculated based on a local reference surface. The original surface roughness Ra is measured using a non-contact optical roughness meter. Measurements show that the surface defect depth is controlled within the range of 100–120 μm, and the original surface roughness Ra is ≤11 μm.

[0171] Mechanical removal treatment is applied to the product: a combination of vibratory polishing and localized flexible abrasive polishing wheel is used to reduce the depth of surface defects. The abrasive grit size is 240 mesh, the polishing speed is 6000 rpm, the contact pressure is 0.10 MPa, and the thickness removed in a single pass is 0.20 mm.

[0172] The material removal thickness is not less than the average depth of the defect layer, used to remove weak layers and deep pits on the printed surface. After mechanical removal, the surface roughness of the product is reduced to Ra≤8μm.

[0173] Intermediate homogenization treatment of products: The surface of the product after mechanical removal is further trimmed. The removal thickness of the intermediate homogenization treatment is less than that of the initial mechanical removal thickness. Its purpose is to reduce surface micro-peaks, homogenize processing marks and improve inspection friendliness.

[0174] In one optional embodiment, a combination of sandblasting and chemical homogenization is used. The sandblasting process parameters are as follows: alumina or ceramic beads are used as the blasting medium, with a particle size of 220 mesh; the blasting pressure is 0.45 MPa; the blasting angle is 80°; and the blasting time is 8 min. The chemical homogenization process parameters are as follows: a low-concentration acidic homogenization solution is used, with a total acid content of 20% (volume fraction) and the remainder being deionized water; the treatment time is 5 min; and the treatment temperature is 40°C. This treatment is used to remove localized micro-protrusions and micro-machining traces left after mechanical removal.

[0175] In another alternative embodiment, electrochemical homogenization is used instead of chemical homogenization. The electrochemical homogenization process has a processing voltage of 320V, a processing time of 4min, and a processing temperature of 80℃.

[0176] After intermediate homogenization, the surface roughness Ra of the product was reduced to 6 μm.

[0177] Dimensional correction processing: This involves machining the connecting holes, assembly surfaces, or design-specified reference areas of the product to ensure dimensional accuracy. The process parameters for dimensional correction are: single-cut depth of cut 0.10 mm, feed rate 600 mm / min, spindle speed 8000 rpm, and residual surface roughness controlled to Ra ≤ 6 μm after processing. This step is only used to ensure critical dimensions and reference accuracy and is not considered a major surface removal process.

[0178] Final surface treatment of the product: The product is ultrasonically cleaned using a neutral cleaning solution at a frequency of 40 kHz for 15 minutes at a temperature of 50°C. Subsequently, it is passivated using an acidic passivation solution for 10 minutes at 40°C. If necessary, a protective oil coating or temporary sealing protection is applied after passivation.

[0179] Example 6

[0180] This embodiment provides a method for preparing an additively manufactured product, illustrating the original surface roughness of the product obtained by printing in this application and the change in surface roughness of the product after mechanical removal treatment. The only difference between this preparation method and Embodiment 1 is that:

[0181] In this embodiment, the mechanical removal process on the product is modified to use a rotary grinding head for polishing. After printing, the original surface roughness Ra of the printed product was measured to be 6.0 μm on the upper surface, 7.0 μm on the vertical surface, and 9.0 μm on the lower surface. Then, a rotary grinding head was used to mechanically polish the surfaces facing different directions.

[0182] The upper surface mainly has shallow molten pool ripples and a small amount of attached powder. It is finely polished using a 400-mesh resin grinding head with a grinding head speed of 2000 rpm, a contact pressure of 0.02 MPa, a feed speed of 300 mm / min, and a polishing cycle of 1.

[0183] Vertical surface: Interlayer step marks and locally adhered powder exist. Cross-grinding is performed using a 320-mesh diamond grinding head. During grinding, a diamond grinding head with a grit size of 320 mesh is used, the grinding head speed is 3000 rpm, the contact pressure is 0.04 MPa, the feed rate is 250 mm / min, and the number of grinding passes is 1-2. The grinding path includes a longitudinal path along the forming height direction and a transverse path intersecting it.

[0184] The lower surface exhibits support connection marks, burrs, and noticeable localized protrusions. Initially, a 240-grit carbide grinding head was used for rough grinding, followed by a 400-grit resin grinding head for finish grinding. The rough grinding parameters were: grinding head grit or equivalent grinding grit of 240 mesh, grinding head speed of 4000 rpm, contact pressure of 0.06 MPa, feed rate of 200 mm / min, and one grinding cycle. The finish grinding parameters were: grinding head grit of 400 mesh, grinding head speed of 2500 rpm, contact pressure of 0.02 MPa, feed rate of 300 mm / min, and one grinding cycle.

[0185] After the above mechanical polishing, the surface roughness Ra of the upper surface is reduced to 1.8 μm, the surface roughness Ra of the vertical surface is reduced to 2.0 μm, and the surface roughness of the lower surface is reduced to 2.3 μm.

[0186] Example 7

[0187] This embodiment provides a method for preparing an additively manufactured product, illustrating the original surface roughness of the product obtained by printing in this application and the change in surface roughness of the product after mechanical removal treatment. The only difference between this preparation method and Embodiment 2 is that:

[0188] In this embodiment, the mechanical removal process on the product is modified to be polished using a rotary grinding head. After printing, the original surface roughness Ra of the printed product was measured to be 7.0 μm on the upper surface, 8.5 μm on the vertical surface, and 10.0 μm on the lower surface. Then, a rotary grinding head was used to mechanically polish the surfaces facing different directions.

[0189] Top surface: Fine grinding is performed using a 400-grit resin grinding head at a speed of 2500 rpm, a contact pressure of 0.03 MPa, a feed rate of 250 mm / min, and 1 to 2 grinding passes.

[0190] Vertical surface: There are interlayer step patterns and localized powder adhering. First, use a 320-grit diamond grinding head to remove the interlayer step peaks and adhering particles, and then use a 400-grit resin grinding head for finishing.

[0191] The first stage uses a 320-grit diamond grinding head for grinding, with a grinding head speed of 3500 rpm, a contact pressure of 0.05 MPa, a feed rate of 200 mm / min, and one grinding cycle. The second stage uses a 400-grit resin grinding head for dressing, with a grinding head speed of 2500 rpm, a contact pressure of 0.03 MPa, a feed rate of 250 mm / min, and one grinding cycle.

[0192] Lower surface: First, use a 240-grit carbide grinding head to remove support residue and larger protrusions, then use a 320-grit diamond grinding head and a 400-grit resin grinding head to gradually finish.

[0193] The process consists of three stages: First, a cemented carbide grinding head with a grit size or equivalent grinding grit of 240 mesh is used for local finishing, with a grinding head speed of 4500 rpm, a contact pressure of 0.08 MPa, a feed rate of 150 mm / min, and one grinding cycle; Second, a diamond grinding head with a grit size of 320 mesh is used for main finishing, with a grinding head speed of 3500 rpm, a contact pressure of 0.05 MPa, a feed rate of 200 mm / min, and one grinding cycle; Third, a resin grinding head with a grit size of 400 mesh is used for fine finishing, with a grinding head speed of 2500 rpm, a contact pressure of 0.03 MPa, a feed rate of 250 mm / min, and one grinding cycle.

[0194] After the above mechanical polishing, the surface roughness Ra of the upper surface is reduced to 1.8 μm, the surface roughness Ra of the vertical surface is reduced to 2.0 μm, and the surface roughness of the lower surface is reduced to 2.2 μm. Preferably, the surface roughness Ra of the upper surface, the vertical surface, and the lower surface are all controlled at 2 μm.

[0195] Example 8

[0196] This embodiment provides a method for preparing an additively manufactured product, illustrating the original surface roughness of the product obtained by printing in this application and the change in surface roughness of the product after mechanical removal treatment. The only difference between this preparation method and Embodiment 3 is that:

[0197] In this embodiment, the mechanical removal process on the product is modified to be polished using a rotary grinding head. After printing, the original surface roughness Ra of the printed product was measured to be 8.0 μm on the upper surface, 9.5 μm on the vertical surface, and 11.0 μm on the lower surface. Then, a rotary grinding head was used to mechanically polish the surfaces facing different directions.

[0198] Top surface: The main grinding is performed using a 320-grit diamond grinding head, followed by a 400-grit resin grinding head for finishing. The main grinding parameters are: grinding head speed 3000 rpm, contact pressure 0.04 MPa, feed rate 200 mm / min, and 1 grinding cycle. The finishing grinding parameters are: grinding head speed 2500 rpm, contact pressure 0.02–0.03 MPa, feed rate 250–300 mm / min, and 1 grinding cycle.

[0199] Vertical surface: There are interlayer step patterns and local powder adhering. First, use a 240-grit carbide grinding head to repair the local step peaks and larger protrusions, and then use a 320-grit diamond grinding head and a 400-grit resin grinding head for polishing in sequence.

[0200] The first stage uses a carbide grinding head at a speed of 4000 rpm and a contact pressure of 0.06 MPa; the second stage uses a diamond grinding head at a speed of 3500 rpm and a contact pressure of 0.05 MPa; the third stage uses a resin grinding head at a speed of 2500 rpm and a contact pressure of 0.03 MPa. The grinding path uses a longitudinal and transverse intersecting method to reduce the directionality of the interlayer step pattern.

[0201] Lower surface: First, a 240-grit carbide grinding head is used to remove the support connection residue, burrs, and large local protrusions. Then, a 240-320 grit diamond grinding head is used for the main surface removal. Finally, a 400-grit resin grinding head is used for fine finishing.

[0202] The process consists of three stages: First, a cemented carbide grinding head with a grit size or equivalent grinding grit of 240 mesh is used for local finishing. The grinding head speed is 5000 rpm, the contact pressure is 0.10 MPa, the feed rate is 100 mm / min, and the number of grinding passes is 1-2. Second, a diamond grinding head with a grit size of 240-320 mesh is used for main finishing. The grinding head speed is 3500-4500 rpm, the contact pressure is 0.05-0.07 MPa, the feed rate is 150-200 mm / min, and the number of grinding passes is 1-2. Third, a resin grinding head with a grit size of 400 mesh is used for fine finishing. The grinding head speed is 2500-3000 rpm, the contact pressure is 0.02-0.04 MPa, the feed rate is 250-300 mm / min, and the number of grinding passes is 1.

[0203] After the above mechanical polishing, the surface roughness Ra of the upper surface is reduced to 1.9 μm, the surface roughness Ra of the vertical surface is reduced to 2.1 μm, and the surface roughness of the lower surface is reduced to 2.5 μm.

[0204] In some embodiments, this application also provides an additive manufacturing product that uses the preparation method shown in any of the above embodiments.

[0205] Optionally, additive manufacturing products are structural or functional components in the aerospace field, including but not limited to aero-engine parts, aircraft structural supports, satellite parts, spacecraft heat exchangers, and key landing gear components. SLM additive manufacturing technology, with its high forming accuracy and high design freedom, can realize structures that are difficult to process using traditional processes, such as complex internal flow channels, lightweight lattice structures, and topology optimization. It is particularly suitable for the urgent needs of the aerospace field for lightweight and functionally integrated parts.

[0206] By employing the preparation method of any of the above embodiments of this application, the depth of original surface defects is reduced by controlling the contour scanning parameters during the printing stage, and then matching and removing defects based on this depth during the post-processing stage. This allows additively manufactured products to maintain structural dimensional accuracy while possessing excellent surface quality and service reliability. Testing has shown that additively manufactured products obtained using the preparation method of this application exhibit significantly reduced surface roughness, high fluorescence detection pass rate, and good surface uniformity, meeting the stringent requirements of high-reliability applications such as aerospace.

[0207] 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. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0208] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method for preparing an additively manufactured product, characterized in that, The preparation method includes: By controlling the contour scanning parameters for selective laser melting printing, the original surface defect depth of the printed product is kept within a preset range. The product is subjected to mechanical removal treatment to reduce the depth of surface defects, wherein the material removal thickness of the mechanical removal treatment is greater than or equal to the average depth of the defect layer; The contour scanning parameters include: the number of contour scanning channels is 2 to 4, and the spacing between two adjacent contour scanning channels is 0.1 to 0.16 mm.

2. The method for preparing additively manufactured products according to claim 1, characterized in that, The product has a lower surface, a vertical surface, and a top surface. The selective laser melting printing method by controlling contour scanning parameters further includes setting contour scanning parameters according to the product surface type. The upper surface is laser-treated with a power of 130–170W and a scanning speed of 500–1000 mm / s. For vertical surfaces, a laser power of 130–170W and a scanning speed of 500–1000 mm / s are used. The lower surface uses a laser with a power of 90-120W and a scanning speed of 700-1200mm / s, and the scanning speed of the lower surface is higher than that of the upper surface and the vertical surface.

3. The method for preparing additively manufactured products according to claim 1, characterized in that, The preset range of the original surface defect depth of the product is set to be less than or equal to 120 μm, and the original surface roughness Ra of the product is ≤11 μm.

4. The method for preparing additively manufactured products according to claim 1, characterized in that, The mechanical removal process employs one or more of the following: grinding wheel, belt grinding, vibratory polishing, flexible abrasive polishing, and rotary grinding head grinding.

5. The method for preparing an additively manufactured product according to claim 1, characterized in that, The preparation method further includes sandblasting; the sandblasting medium is one or more of alumina, glass beads and ceramic beads; the particle size of the medium is 100-220 mesh, the spraying pressure is 0.25-0.45 MPa, the spraying time is 2-8 min, and the spraying angle is 45-80°.

6. The method for preparing an additively manufactured product according to claim 5, characterized in that, The preparation method further includes chemical homogenization treatment; the chemical homogenization treatment uses a low-concentration acidic homogenization solution, the pH value of the low-concentration acidic homogenization solution is 1-4, the total acid content is 3%-20%, the treatment time is 1-5 min, and the treatment temperature is 20-40℃; the acid in the low-concentration acidic homogenization solution includes one or more of nitric acid, citric acid, phosphoric acid, acetic acid, and oxalic acid.

7. The method for preparing an additively manufactured product according to claim 5 or 6, characterized in that, The preparation method further includes an electrochemical homogenization treatment; the voltage of the electrochemical homogenization treatment is 200-320V, the treatment time is 1-4min, and the treatment temperature is 40-80℃.

8. The method for preparing an additively manufactured product according to claim 1, characterized in that, The preparation method further includes: The product is subjected to dimensional correction processing; the dimensional correction processing adopts one or more of CNC milling, finish milling or semi-finish milling, CNC grinding and light dressing cutting; the single cutting depth of the dimensional correction processing is 0.01 to 0.10 mm, the feed rate is 100 to 600 mm / min, and the spindle speed is 2000 to 8000 rpm.

9. The method for preparing an additively manufactured product according to claim 1, characterized in that, The preparation method further includes: performing a final surface treatment on the product; the final surface treatment includes one or more of cleaning treatment, passivation treatment and protective treatment.

10. An additively manufactured product, characterized in that, The product is prepared by the additive manufacturing method as described in any one of claims 1-9.

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