Surface treatment method for polyether-ether-ketone-based composite material 3D printing thin-wall workpiece

Abstract

The invention discloses a polyether-ether-ketone-based composite material 3D printing thin-wall part surface treatment method which comprises the following steps: S1, cleaning the surface of a composite material 3D printing part, uniformly coating the surface of a pre-film with a layer of adhesive after the surface of the composite material 3D printing part is dried, and performing polishing treatment by using abrasive paper after the adhesive is cured; s2, the surface of the workpiece is evenly coated with a layer of adhesive; s3, a thin film is softened and then attached to the surface, coated with the adhesive, of the workpiece, and the thin film is tightly attached to the surface of the workpiece; and S4, the workpiece coated with the thin film is embedded into a container filled with quartz sand, the whole container is sent into a drying oven for heat treatment, the adhesive is cured, the workpiece is taken out after curing is completed, and the remaining portion of the thin film is trimmed. According to the method, the mechanical property of the thermoplastic composite 3D printed part is effectively improved, the problem that the anisotropy of the thermoplastic composite 3D printed part is remarkable is effectively solved, and the interlayer bonding performance is remarkably improved.

Description

Technical Field

[0001] This invention belongs to the field of 3D printing technology, specifically relating to a surface treatment method that can improve the mechanical properties of 3D printed thin-walled parts made of polyether ether ketone (PEEK) composite materials. Background Technology

[0002] The forming principle of thermoplastic composite 3D printing technology is to heat and melt linear thermoplastic material in a nozzle, and then extrude it through the nozzle's micro-nozzles (typically 0.2–0.8 mm), depositing it layer by layer until the desired solid model is formed. Due to its advantages such as high design freedom, high material utilization, and the ability to rapidly prototyping complex structures, it is widely used in aerospace, automotive, and medical fields. However, thermoplastic composite 3D printed parts have disadvantages such as low mechanical properties, significant anisotropy, and poor surface quality. Taking polyetheretherketone (PEEK), currently at the top of the thermoplastic pyramid, as an example, its 0° tensile strength is only about 100 MPa, and its interlayer tensile strength is only 20-30% of that. The printed parts exhibit delamination and layer textures on the surface, and in areas with large curvature changes, the surface roughness is generally above Ra10, making it difficult for its mechanical properties to meet practical application requirements.

[0003] Currently, common methods to improve the mechanical properties of 3D printed thermoplastic composite parts are through optimizing printing process parameters or heat treatment. However, the former has limited effectiveness and struggles to balance printing efficiency and part accuracy, while the latter can improve mechanical properties but significantly reduces the elongation of the part, making it more brittle. Patent document CN109774118A proposes a hybrid manufacturing technology that involves spraying an ethanol solution containing sodium alginate powder during printing, followed by immersion in an aqueous solution containing Ca2+, Zn2+, or Fe3+ after printing. The cross-linking reaction of these substances forms a gel network structure within the part, thereby improving its overall mechanical properties. However, this method has the following problems: 1) It requires specific equipment, limiting its use and increasing manufacturing costs; 2) Spraying sodium alginate on the printing surface affects interlayer adhesion and is detrimental to interlayer mechanical properties; 3) Some of the sprayed sodium alginate powder exists in the closed gaps between the printing paths, making it difficult to contact the specific solution for cross-linking, thus hindering effective control of its reinforcing effect. Patent document CN113733562A proposes the design of a printing nozzle with ultrasonic micro-forging function, which reduces forming voids and defects and decreases crystal size through ultrasonic vibration, thereby improving the mechanical properties of the part. However, this method requires special printing equipment, has high requirements for the stability of the printing process, and increases manufacturing costs. Summary of the Invention

[0004] The purpose of this invention is to provide a surface treatment method for 3D printed thin-walled parts made of polyether ether ketone (PEEK) composite materials to improve the mechanical properties of the parts.

[0005] This invention is achieved through the following technical solution: A surface treatment method for 3D printed thin-walled parts made of polyetheretherketone (PEEK) composite materials includes the following steps: S1. Clean the surface of the 3D printed composite material part. After drying, apply a layer of adhesive evenly to the pre-attached film surface. After the adhesive has cured, sand it with sandpaper. S2. Apply a layer of adhesive evenly to the surface of the part; S3. After softening the film, apply it to the surface of the part coated with adhesive, and ensure that the film adheres tightly to the surface of the part. S4. Embed the part covered with the film into a container filled with quartz sand, and put the entire container into an oven for heat treatment to cure the adhesive. After curing, remove the part and trim off any excess film.

[0006] In some embodiments of the present invention, the same adhesive is used for coating in steps S1 and S2.

[0007] In some embodiments of the present invention, in steps S1 and S2, the adhesive is a thermoplastic polyurethane adhesive or an epoxy resin adhesive.

[0008] In some embodiments of the present invention, in step S1, the coating thickness of the adhesive is 0.03 mm to 0.05 mm, preferably 0.05 mm.

[0009] In some embodiments of the present invention, the sandpaper used for polishing in step S1 is 400-800 mesh, preferably 600 mesh.

[0010] In some embodiments of the present invention, in step S2, the coating thickness of the adhesive is 0.05 mm to 0.1 mm, preferably 0.1 mm.

[0011] In some embodiments of the present invention, in step S3, the film is a polyurethane film or a polyethylene terephthalate film, preferably a polyurethane film.

[0012] In some embodiments of the present invention, in step S3, the thickness of the film is 0.1 mm to 0.3 mm, preferably 0.2 mm.

[0013] In some embodiments of the present invention, in step S4, the part covered with a thin film is buried in a container filled with quartz sand, so that the surface of the part is subjected to a pressure of not less than 0.015 bar.

[0014] In some embodiments of the present invention, the quartz sand has a size of 100 mesh to 300 mesh, preferably 200 mesh.

[0015] Compared with the prior art, the present invention has the following advantages and beneficial effects: This invention effectively improves the mechanical properties of 3D printed thermoplastic composite parts, effectively addresses the significant anisotropy of 3D printed thermoplastic composite parts, significantly enhances interlayer bonding performance, and effectively improves the surface hardness, wear resistance, and surface quality of the parts. It can effectively protect the surface of the parts and extend their service life.

[0016] The method of this invention does not require modification of existing equipment or 3D printing devices, and does not increase equipment costs; the process is simple, convenient, easy to operate and low in cost; it does not require cross-linking reaction or long-term stable operation, the manufacturing process is controllable, has high fault tolerance and stable results, and helps to further expand the application scope of thermoplastic composite material 3D printing technology. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of a thin-walled composite material 3D printed part in an embodiment of the present invention.

[0019] Figure 2 This is a flowchart of the surface treatment process for the workpiece in an embodiment of the present invention.

[0020] Figure 3 This is a graph showing the curing temperature profiles of different adhesives.

[0021] Figure 4 This is a schematic diagram of the sand embedding process performed on the workpiece in an embodiment of the present invention.

[0022] Figure 5 This is a schematic diagram comparing the surface quality of parts after surface treatment in an embodiment of the present invention. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments.

[0024] This invention is mainly aimed at high-performance thermoplastic materials used in the aerospace manufacturing field, such as polyetheretherketone (PEEK), which has a melting point of 343℃, a printing temperature of 420℃-440℃, high viscosity, and poor flowability. Compared with common consumer-grade printing materials on the market, such as PLA, it is more difficult to print.

[0025] PEEK is short for polyetheretherketone, a high-melting-point semi-crystalline aromatic thermoplastic special engineering plastic. It has excellent mechanical properties, chemical corrosion resistance, creep resistance, fatigue resistance, radiation resistance, and high-temperature resistance. Its comprehensive performance is at the top of the plastic pyramid. It can replace aluminum and other metal materials in the manufacture of various aerospace parts, such as sealing plates, radar antenna covers, and sealing rings. Therefore, it has attracted widespread attention and is currently a hot research material in the industry.

[0026] Because the fused deposition modeling (FDM) printing speed is relatively slow (generally 20-60 mm / s), the thermoplastic resin (such as polyetheretherketone) on the surface of the previous layer of deposited filament has already solidified during the fused deposition process, resulting in very weak interlayer bonding strength and low strength in the Z-axis direction, which easily leads to interlayer delamination and cracking.

[0027] The current mainstream fused deposition modeling (FDM) technology has a layer thickness of 0.15-0.2 mm and a linewidth of 0.4-0.6 mm, resulting in a very obvious "layer texture" phenomenon and a surface roughness generally above Ra10. This easily leads to stress concentration, making the problem of low strength in the Z-axis direction even more pronounced. Based on the above problems, this invention improves the surface quality of the part to enhance its mechanical properties.

[0028] In some embodiments of the present invention, the surface treatment method for 3D printed thin-walled parts of polyetheretherketone (PEEK) composite materials is described in accordance with... Figure 2 This includes the following steps: S1, Surface pretreatment The surface of the 3D printed composite material part is cleaned and dried. After that, a layer of adhesive is evenly applied to the pre-attached film surface. After the adhesive has cured, it is sanded with sandpaper to remove surface impurities and burrs and improve the surface roughness of the part.

[0029] S2, Apply adhesive A layer of adhesive is uniformly coated on the surface of the pretreated part. The adhesive is either thermoplastic polyurethane (TPU) adhesive or epoxy resin adhesive.

[0030] S3, Applying film The film is softened by hot air blown from a hot air blower and then adhered to the surface of the part coated with adhesive. A certain pressure is applied to ensure that the film adheres tightly to the surface of the part. The size of the film should be slightly larger than the size of the part to ensure that the film can completely cover the surface of the part to which the film is applied.

[0031] S4, Post-processing The part covered with the film is embedded in a container filled with quartz sand, and the entire container is sent into an oven for heat treatment to cure the adhesive.

[0032] After curing, remove the part, clean off any foreign matter such as quartz sand from the surface, and trim the excess film to match the dimensions of the part.

[0033] In step S1, the cleaning agent used to clean the parts is alcohol or acetone.

[0034] The sandpaper used should be 400-800 grit, preferably 600 grit. Sandpaper with a grit higher than 800 grit will not achieve the desired roughening effect, while sandpaper with a grit lower than 400 grit may damage the substrate of the part and affect its mechanical properties.

[0035] In steps S1 and S2, the method used to apply the adhesive is one or more of the following: brush coating, doctor blade coating, roller coating, and spray gun coating. Generally speaking, brush coating is preferred for small area coating or complex feature structures, doctor blade coating is preferred for large area planar feature structures, and roller coating or spray gun coating is preferred for large-size, small-curvature continuous coating structures.

[0036] In steps S1 and S2, the adhesive applied should be consistent.

[0037] In step S1, the main function of applying adhesive is to fill the gaps between the layers of the workpiece and improve the surface roughness of the workpiece. Therefore, in order to reduce the amount of sanding, the coating thickness should be relatively small, generally 0.03mm to 0.05mm, preferably 0.05mm.

[0038] By controlling the coating thickness, the amount of subsequent sanding can be reduced. However, excessive coating can make it difficult to control the surface smoothness after curing, requiring adjustments to the sanding skills of the workers. Furthermore, too much adhesive can cause the stress generated during curing to deform the part.

[0039] In step S2, the main function of applying the adhesive is to ensure the bonding strength between the part and the film. Therefore, the coating thickness should be relatively large, generally 0.05mm to 0.1mm, preferably 0.1mm. Excess adhesive can be squeezed out by applying pressure with a hand roller during subsequent film lamination.

[0040] In step S3, the film is a polyurethane (TPU) film or a polyethylene terephthalate (PET) film, preferably a polyurethane (TPU) film.

[0041] The thickness of the film is 0.1 mm to 0.3 mm, preferably 0.2 mm.

[0042] In step S3, the tool used to compact the film and the workpiece is a hand roller, which should be made of plastic and have a surface finish better than Ra0.4. The pressure applied to compact the film and the workpiece is 5N to 20N, preferably 15N.

[0043] The compaction of the film in step S3 should be performed as soon as possible after step S2 is completed, generally within 10 minutes.

[0044] Step S3: For TPU film, the recommended temperature of the hot air blower is 60℃~90℃, preferably 90℃; for PET film, the hot air blower temperature is 90℃~120℃, preferably 120℃.

[0045] Reference Figure 3 For TPU adhesives, the curing temperature is 60℃~90℃, the heating / cooling rate is ≤3℃ / min, and the holding time is 15min~30min; preferably, the curing temperature is 60℃, the heating rate is 2℃ / min, and the holding time is 30min.

[0046] For epoxy resin adhesives, the curing temperature is 90℃~120℃, the heating / cooling rate is ≤2℃ / min, and the holding time is 120min~180min; preferably, the curing temperature is 90℃, the heating rate is 1.5℃ / min, and the holding time is 180min.

[0047] In step S4, the surface of the part should be subjected to a pressure of not less than 0.015 bar.

[0048] According to the fluid pressure formula P=ρgh (the bulk density ρ of 200 mesh quartz sand is 1.5×10⁻⁶),... 3 kg / m 3 Calculate the gravitational acceleration (g = 10). When using 200-mesh quartz sand, the embedment depth of the part should not be less than 100mm.

[0049] The size of the quartz sand is 100 mesh to 300 mesh, preferably 200 mesh.

[0050] Place the part with the opening facing upwards and bury it in the quartz sand, allowing the quartz sand to enter the part and ensuring that the pressure inside and outside the part is consistent, thus preventing the part from being deformed by pressure.

[0051] The embedment depth is directly related to the size of the quartz sand. Because quartz sand consists of spherical particles, the density used in practice is the "bulk density," not the density of the quartz sand itself. Generally, the larger the mesh number of the quartz sand, the greater the bulk density, and vice versa. The 100mm embedment depth parameter mentioned above is calculated based on 200-mesh quartz sand. If the mesh number of the quartz sand changes, the embedment depth parameter should also be changed accordingly. Furthermore, different component structures require different embedding methods; incorrect embedding methods may lead to component deformation.

[0052] The surface treatment method of the present invention will be described in detail below with reference to specific embodiments.

[0053] Reference Figure 1 This is a typical thermoplastic composite material 3D printed thin-walled part with a wall thickness of 1mm. It belongs to fairing parts and has high requirements for surface quality.

[0054] Reference Figure 2 The surface treatment process for the parts is as follows: Clean the surface of the 3D-printed thermoplastic composite part with alcohol. After drying, use a roller to evenly coat the pre-attached film surface with a layer of epoxy resin adhesive, 0.05mm thick. (Refer to...) Figure 2 The epoxy resin adhesive is cured at a curing temperature of 90℃, a heating rate of 1.5℃ / min, and a holding time of 180min. After the epoxy resin adhesive has cured, it is sanded with 600-grit sandpaper to remove surface impurities and burrs and improve the surface roughness of the part. After sanding, the surface of the part is cleaned.

[0055] After pretreatment, apply a layer of epoxy resin adhesive evenly to the surface of the part using a rubber roller. The thickness is 0.1 mm. Within 10 minutes, use hot air blown from a hot air blower to soften the PET film and then apply it to the surface of the part coated with adhesive. Apply about 15 N of pressure using a hand roller to ensure that the film adheres tightly to the surface of the part. The size of the film should be slightly larger than the size of the part to ensure that the film can completely cover the pre-filmed surface of the part.

[0056] The 3D-printed part of the thermoplastic composite material coated with a thin film is embedded in a container filled with quartz sand, and the embedding method is as follows. Figure 4 Then, the entire container is placed in an oven for heat treatment. Please refer to [the instructions]. Figure 2 The curing process was carried out at a curing temperature of 90℃, a heating rate of 1.5℃ / min, and a holding time of 180min.

[0057] After curing, the part is removed, foreign objects such as quartz sand are cleaned off the surface of the part, and the excess film is trimmed to match the shape and size of the part, thus completing the part manufacturing process.

[0058] like Figure 5The manufacturing principle of composite material 3D printing thin-walled parts is through layer-by-layer stacking. Magnified magnification reveals obvious "layer textures," resulting in poor surface quality. These textures also create stress concentration points, leading to poor mechanical properties, especially the Z-axis interlayer bonding performance. After treatment using the method of this invention, the most "protruding" areas on the part's surface are sanded away with 600-grit sandpaper, while the "recessed" areas are filled with epoxy resin. This significantly improves stress concentration and mechanical properties. Furthermore, by covering the outer layer with a thin film, the mechanical properties are further enhanced. Relevant performance test data are shown in Table 1. Simultaneously, because the outermost surface of the part is a thin film, its surface quality and wear resistance are greatly improved.

[0059] Table 1 Certain terms are used in the specification and claims to refer to specific components. Those skilled in the art will understand that hardware manufacturers may use different names to refer to the same component. This specification and claims do not distinguish components based on differences in name, but rather on differences in function. The terms "comprising" and "including" used throughout the specification and claims are open-ended and should be interpreted as "comprising / including but not limited to". "Approximately" means that within an acceptable margin of error, those skilled in the art can solve the technical problem and substantially achieve the technical effect within a certain margin of error. The following descriptions in the specification are preferred embodiments for carrying out this application; however, these descriptions are for the purpose of illustrating the general principles of this application and are not intended to limit the scope of this application. The scope of protection of this application shall be determined by the appended claims.

[0060] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a product or system comprising a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a product or system. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the product or system that includes said element.

[0061] It should be understood that the term "and / or" used in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0062] The foregoing description illustrates and describes several preferred embodiments of this application. However, as previously stated, it should be understood that this application is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. It can be used in various other combinations, modifications, and environments, and can be altered within the scope of the application concept described herein through the foregoing teachings or techniques or knowledge in related fields. Any modifications and variations made by those skilled in the art that do not depart from the spirit and scope of this application should be within the protection scope of the appended claims.

Claims

1. A surface treatment method for 3D printed thin-walled parts made of polyetheretherketone (PEEK) composite materials, characterized in that, Includes the following steps: S1. Clean the surface of the 3D printed composite material part. After drying, apply a layer of adhesive evenly to the pre-attached film surface. After the adhesive has cured, sand it with sandpaper. S2. Apply a layer of adhesive evenly to the surface of the part; S3. After softening the film, apply it to the surface of the part coated with adhesive, and ensure that the film adheres tightly to the surface of the part. S4. Embed the part covered with the film into a container filled with quartz sand, and put the entire container into an oven for heat treatment to cure the adhesive. After curing, remove the part and trim off any excess film.

2. The surface treatment method for 3D printed thin-walled parts of polyetheretherketone (PEEK) composite materials according to claim 1, characterized in that, The same adhesive is used for coating in steps S1 and S2.

3. The surface treatment method for 3D printed thin-walled parts of polyetheretherketone (PEEK) composite materials according to claim 1, characterized in that, In steps S1 and S2, the adhesive is a thermoplastic polyurethane adhesive or an epoxy resin adhesive.

4. The surface treatment method for 3D printed thin-walled parts of polyetheretherketone (PEEK) composite materials according to claim 1, characterized in that, In step S1, the coating thickness of the adhesive is 0.03 mm to 0.05 mm, preferably 0.05 mm.

5. The surface treatment method for 3D printed thin-walled parts of polyetheretherketone (PEEK) composite materials according to claim 1, characterized in that, In step S1, the sandpaper used for polishing is 400-800 grit, preferably 600 grit.

6. The surface treatment method for 3D printed thin-walled parts of polyetheretherketone (PEEK) composite materials according to claim 1, characterized in that, In step S2, the coating thickness of the adhesive is 0.05 mm to 0.1 mm, preferably 0.1 mm.

7. The surface treatment method for 3D printed thin-walled parts of polyetheretherketone (PEEK) composite materials according to claim 1, characterized in that, In step S3, the film is a polyurethane film or a polyethylene terephthalate film, preferably a polyurethane film.

8. The surface treatment method for 3D printed thin-walled parts of polyetheretherketone (PEEK) composite materials according to claim 1, characterized in that, In step S3, the thickness of the film is 0.1 mm to 0.3 mm, preferably 0.2 mm.

9. The surface treatment method for 3D printed thin-walled parts of polyetheretherketone (PEEK) composite materials according to claim 1, characterized in that, In step S4, the part covered with a thin film is buried in a container filled with quartz sand, so that the surface of the part is subjected to a pressure of not less than 0.015 bar.

10. The surface treatment method for 3D printed thin-walled parts of polyetheretherketone (PEEK) composite materials according to claim 1, characterized in that, The quartz sand has a size of 100 mesh to 300 mesh, preferably 200 mesh.

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