Ultrasonic-assisted machining method for fiber-reinforced ceramic-based composite material thin-wall workpiece

Abstract

The invention belongs to the technical field of aviation composite material workpiece machining, and provides an ultrasonic-assisted machining method for a fiber-reinforced ceramic matrix composite material thin-wall workpiece, which comprises the following steps: establishing an ultrasonic machining platform; workpiece clamping and positioning are designed and manufactured through a foam tool; the workpiece is processed and clamped to a foam tool; designing a processing path; ultrasonic machining parameters are determined; ultrasonic-assisted machining of the workpiece is completed; processing the workpiece after processing; and product precision and processing quality verification is carried out through three coordinates. According to the method, the technical problems of serious tool abrasion, low efficiency, poor surface quality, layering and the like during traditional processing of the fiber reinforced ceramic matrix composite thin-wall workpiece are solved, and the product processing efficiency and quality are improved while the product processing precision requirement is ensured.

Description

Technical Field

[0001] The invention belongs to the technical field of aviation composite material part processing, and in particular relates to a high-precision processing method for a fiber-reinforced ceramic-based composite material thin-wall part. Background Art

[0002] Due to their high hardness and fiber-woven structure, fiber-reinforced ceramic matrix composites (FMCs) present significant challenges in material removal during machining, leading to severe tool wear. Research results indicate that cutting temperatures in conventional FMCs can reach 700°C, resulting in high cutting forces and rapid tool failure. Variations in tool diameter during machining also lead to poor surface finish accuracy. Especially when machining thin-walled parts, their high brittleness and low fracture toughness predispose them to brittle fracture during conventional milling and drilling processes, leading to crack initiation and propagation into the material, resulting in severe surface and subsurface damage. The anisotropic fibers in FMCs can lead to defects such as fiber pullout, delamination, and internal debonding during machining processes such as cutting, grinding, and drilling, significantly impacting the workpiece's performance.

[0003] In recent years, ultrasonic vibration machining technology has been widely studied by domestic and foreign experts and scholars because of its ability to effectively improve the machining quality of hard and brittle materials. Studies have shown that ultrasonic-assisted machining enables the tool to generate high-frequency, low-amplitude cutting motion during the machining process, thereby promoting the removal of material from the product surface in a trace manner, which can effectively reduce the cutting force and cutting temperature generated by the tool during machining, improve tool life and machining efficiency, while reducing damage to the product surface, reducing product surface roughness, and improving product surface integrity. The characteristic of ultrasonic-assisted machining of trace removal helps to remove fibers in thin-walled parts of fiber-reinforced ceramic-based materials in a micro-brittle manner, inhibits interface cracks, and hinders the expansion of fiber cracks, which can effectively alleviate the manufacturing difficulties of such difficult-to-machine materials. In addition, ultrasonic toolholders are also easy to integrate with CNC machine tools. For this purpose, a high-precision machining method for thin-walled parts of fiber-reinforced ceramic-based composite materials was studied. Summary of the Invention

[0004] In response to the problems of low efficiency, low precision, poor surface quality, short tool life and easy delamination in existing mechanical processing, the present invention provides a high-precision processing method for thin-walled parts of fiber-reinforced ceramic-based composite materials. While ensuring the processing accuracy and quality requirements of the products, the processing efficiency and tool life are improved, and the occurrence of delamination is avoided.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A method for ultrasonically assisted machining of thin-walled fiber-reinforced ceramic matrix composite materials comprises the following steps:

[0007] Establishing ultrasonic machining platform;

[0008] Foam tooling design and manufacturing;

[0009] The workpiece is clamped onto the foam fixture;

[0010] Design machining paths;

[0011] Determine ultrasonic machining parameters;

[0012] Complete ultrasonic assisted processing of workpieces;

[0013] Post-processing of workpieces;

[0014] The three-coordinate process is used to inspect product accuracy and processing quality.

[0015] As a further solution of the present invention: the establishment of the ultrasonic machining platform is specifically: installing the ultrasonic tool holder system to a five-axis CNC machining center to complete the construction of the ultrasonic machining platform.

[0016] As a further solution of the present invention: the foam tooling is designed and manufactured, specifically: the effective area of ​​the product is clarified according to the product drawing, positioning holes and positioning buckles are set in the product margin area, the foam tooling is designed according to the product shape, positioning holes and positioning buckles, the foam blank is placed on the ultrasonic machining platform and a machining coordinate system is established, and finally the foam tooling manufacturing is completed.

[0017] As a further solution of the present invention: the product processing and clamping are specifically as follows: the outer surface of the product is polished and trimmed, and the workpiece is positioned on the foam tooling using positioning pins and positioning clips to complete the clamping of the workpiece; after the product is clamped, the clamping effect is inspected to check whether there is a problem of over-positioning or insufficient positioning, and the foam tooling is redesigned and manufactured according to the inspection structure to optimize the foam tooling structure and improve the positioning accuracy.

[0018] As a further solution of the present invention: the design of the processing path is specifically: using UG software to generate a tool processing trajectory, the starting point of the tool path needs to be set in the product allowance area, and the tool path of the initial processing needs to be tangent to the processing path to reduce the initial cutting force. After the tool path is completed, the trajectory is processed by a post-processing program to make it a CNC processing program that can be recognized by the machine tool, and input into the CNC machine tool.

[0019] As a further solution of the present invention: the determination of ultrasonic machining parameters is specifically: using orthogonal test method and single factor test method to conduct process tests on test pieces of the same material to determine the ultrasonic machining parameters.

[0020] As a further solution of the present invention: the completion of ultrasonic assisted machining of the workpiece is specifically: using a CNC program corresponding to the product to complete ultrasonic assisted machining of the product.

[0021] As a further solution of the present invention: the post-processing of the workpiece is specifically: after the workpiece processing is completed, burrs are polished with fine sandpaper and excess materials on the product surface are cleaned.

[0022] As a further solution of the present invention: the three-coordinate process performs product accuracy and processing quality inspection, specifically: using a three-coordinate measuring instrument to perform surface inspection on the completed product, evaluate whether the processing accuracy and surface quality meet the design requirements, and redesign the processing path and subsequent steps based on the evaluation results, optimize the processing parameters and path, and improve the processing quality.

[0023] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0024] 1. This application solves the problems of current fiber-reinforced ceramic matrix composite thin-walled parts, which are affected by the material properties and other factors, such as low production efficiency, low precision, poor surface quality, short tool life, easy delamination, and unclear economic benefits.

[0025] 2. The protection points of this application mainly lie in three aspects: first, the ultrasonic tool holder system is integrated with the CNC machine tool to establish an ultrasonic-assisted processing platform for thin-walled fiber-reinforced ceramic-based composite materials; second, in view of the complex structure and difficult positioning and clamping characteristics of thin-walled fiber-reinforced ceramic-based composite materials, foam tooling is designed; third, based on the processing platform, the process parameters are verified to obtain a better combination of processing process parameters for thin-walled fiber-reinforced ceramic-based composite materials.

[0026] 3. This application has been applied to the processing of multiple product models. Machining efficiency has increased by approximately 20%, surface roughness has been reduced by 30%, and machining accuracy has been reduced to ±0.1mm. The delamination of product entrances and exits during hole-making has been significantly improved. Tool wear has been reduced, extending tool life by 20%. Overall, this has resulted in a reduction in machining costs of approximately 25%. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a schematic flow chart of a high-precision processing method for thin-walled fiber-reinforced ceramic matrix composite parts according to the present invention;

[0028] Figure 2 This is a schematic diagram of the ultrasonic machining platform of the present invention;

[0029] Figure 3 This is a schematic diagram of the comparison of ultrasonic assisted machining;

[0030] Figure 4 This is a schematic structural diagram of a fiber-reinforced ceramic matrix composite thin-walled component of the present invention;

[0031] Figure 5 This is a schematic diagram of the first version of the foam tooling;

[0032] Figure 6 Schematic diagram of the foam tooling after optimization based on the test assembly results;

[0033] Figure 7 Schematic diagram of tool path design. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solutions and advantages of the present invention more clear, the technical solutions in the embodiments of the present invention will be described in more detail below with reference to the accompanying drawings in the embodiments of the present invention.

[0035] In the drawings, the same or similar reference numerals throughout the drawings represent the same or similar elements or elements having the same or similar functions. The described embodiments are only some of the embodiments of the present invention, but not all of the embodiments.

[0036] The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort shall fall within the scope of protection of the present invention.

[0037] The following is combined with Figure 1-7 The embodiments of the present invention are described in detail.

[0038] Example 1

[0039] Reference Figure 1 The present invention provides a high-precision processing method for thin-walled fiber-reinforced ceramic matrix composite parts, which comprises the following steps:

[0040] Step 1: Establish an ultrasonic machining platform and install the ultrasonic toolholder system to the five-axis CNC machining center to complete the construction of the ultrasonic machining platform;

[0041] Step 2: Design and manufacture foam tooling. Define the effective area of ​​the product according to the product drawing, set positioning holes and positioning buckles in the product margin area, design the foam tooling according to the product shape, positioning holes and positioning buckles, place the foam blank on the ultrasonic machining platform and establish the machining coordinate system to finally complete the foam tooling manufacturing;

[0042] Step 3: Product processing and clamping: polish and trim the outer surface of the product, use positioning pins and positioning buckles to position the workpiece on the foam fixture to complete the workpiece clamping. After the product is clamped, the clamping effect is inspected to check whether there is any problem of over-positioning or insufficient positioning. Re-foam fixture according to the inspection structure, optimize the foam fixture structure, and improve positioning accuracy;

[0043] Step 4: Design the machining path and use UG software to generate the tool machining trajectory. The starting point of the tool path needs to be set in the product allowance area, and the tool path of the initial machining needs to be tangent to the machining path to reduce the initial cutting force. After the tool path is compiled, the trajectory is processed using a post-processing program to make it a CNC machining program that can be recognized by the machine tool and input into the CNC machine tool.

[0044] Step 5: Determine the ultrasonic machining parameters. Use the orthogonal test method and the single factor test method to conduct process tests on test pieces of the same material to determine the ultrasonic machining parameters.

[0045] Step 6: Complete ultrasonic assisted machining of the workpiece and use the corresponding product CNC program to complete ultrasonic assisted machining of the product;

[0046] Step 7: After the workpiece is processed, use fine sandpaper to polish the burrs and clean the excess materials on the surface of the product;

[0047] Step 8: After the workpiece processing is completed, unload the clamping fixture, disconnect the mold vacuum source, remove the workpiece, use sandpaper to grind burrs and clean the workpiece to ensure that the processing quality meets the design requirements.

[0048] Step 9: The three-coordinate process is used to inspect product accuracy and processing quality. A three-coordinate measuring machine is used to inspect the surface of the finished product to evaluate whether the processing accuracy and surface quality meet the design requirements. Based on the evaluation results, the processing path and subsequent steps are redesigned to optimize the processing parameters and path to improve the processing quality.

[0049] Example 2

[0050] The present invention adopts the following technical solutions:

[0051] Ultrasonic vibration-assisted grinding and drilling processing method for thin-walled parts of fiber-reinforced ceramic-based composite materials. Under the conditions of ultrasonic vibration assistance in traditional mechanical processing, a trepanning drill is used for hole making, with a speed of 6000 rpm, a feed of 50 mm / min, and an ultrasonic vibration enablement of 80%. The damage such as delamination at the entrance and exit of the processed through-holes is effectively alleviated.

[0052] Surface processing uses a diamond abrasive ball-end grinding head with a rotation speed of 6000rpm, a feed of 100mm / min, and an ultrasonic vibration enable of 80%. A tool path from outside to inside is used to make the tool start cutting from the product allowance area to avoid the large cutting force generated by tool contact from damaging the effective area of ​​the product. At the same time, the wear of the grinding head after processing is observed under a microscope to determine that ultrasonic vibration can reduce tool wear during processing and thus extend the life of the tool, ultimately achieving high-precision processing of thin-walled curved surface samples of fiber-reinforced ceramic-based composite materials.

[0053] A ready-to-install ultrasonic vibration toolholder is designed. Without changing the structure of the machine tool itself, the ultrasonic vibration-assisted machine tool platform can be built at the lowest cost. Moreover, the ultrasonic vibration processing platform can be built on different machine tools by simply replacing the ultrasonic toolholder accessories.

[0054] A clamping and positioning method for thin-walled curved surface samples made of fiber-reinforced ceramic matrix composites. This invention addresses the difficulties of multi-station clamping and positioning of complex curved thin-walled products requiring machining. Positioning holes and auxiliary positioning slots are provided in the product margin area to enable rapid positioning and clamping of the machined surface.

[0055] The product structure of a fiber-reinforced ceramic matrix composite thin-walled product in a research project has a thin wall thickness and many through holes distributed inside.

[0056] During the product trial production process, it was found that the products obtained by traditional processing methods had the following problems: poor surface roughness, delamination in hole making, and because the product requires two-station processing, the traditional surface positioning method has an offset problem when clamping at the second station. Therefore, the processed products cannot meet the manufacturing accuracy requirement of ±0.15mm.

[0057] To solve the above problems, the processing method proposed in this application is used, which combines ultrasonic processing with the clamping and positioning method of the curved sample, and utilizes intermediate digital models and positioning tooling (positioning method of groove matching surface).

[0058] Comparing the processing results, we found that:

[0059] ① The roughness of the product surface and the delamination of the hole surface and inlet and outlet obtained by ultrasonic processing are significantly improved;

[0060] ② The manufacturing accuracy of three-coordinate measurement products is ±0.1mm, which meets the requirements of parts.

[0061] So far, the purpose of the present invention has been accomplished.

[0062] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for ultrasonically assisted machining of thin-walled fiber-reinforced ceramic matrix composite materials, characterized in that: The following steps are involved: Establishing ultrasonic machining platform; Foam tooling design and manufacturing; The workpiece is clamped onto the foam fixture; Design machining paths; Determine ultrasonic machining parameters; Complete ultrasonic assisted processing of workpieces; Post-processing of workpieces; The three-coordinate process is used to inspect product accuracy and processing quality.

2. The ultrasonic-assisted processing method for fiber-reinforced ceramic matrix composite thin-walled parts according to claim 1, characterized in that: The establishment of the ultrasonic machining platform specifically includes: installing the ultrasonic tool holder system to the five-axis CNC machining center to complete the construction of the ultrasonic machining platform.

3. The ultrasonic-assisted machining method for fiber-reinforced ceramic matrix composite thin-walled parts according to claim 1, characterized in that: The foam tooling is designed and manufactured as follows: the effective area of ​​the product is determined according to the product drawing, positioning holes and positioning clips are set in the product margin area, the foam tooling is designed according to the product shape, positioning holes and positioning clips, the foam blank is placed on the ultrasonic machining platform and a machining coordinate system is established, and finally the foam tooling manufacturing is completed.

4. The ultrasonic-assisted machining method for fiber-reinforced ceramic matrix composite thin-walled parts according to claim 1, characterized in that: The product processing and clamping are specifically as follows: grinding and trimming the outer surface of the product, positioning the workpiece on the foam tooling using positioning pins and positioning clips, and completing the workpiece clamping; after the product is clamped, inspecting the clamping effect to check whether there is any problem of over-positioning or insufficient positioning, redesigning and manufacturing the foam tooling based on the inspection structure, optimizing the foam tooling structure, and improving positioning accuracy.

5. The ultrasonic-assisted machining method for fiber-reinforced ceramic matrix composite thin-walled parts according to claim 1, characterized in that: The design of the processing path is specifically as follows: using UG software to generate a tool processing trajectory, the starting point of the tool path needs to be set in the product allowance area, and the tool path of the initial processing needs to be tangent to the processing path to reduce the initial cutting force. After the tool path is completed, the trajectory is processed using a post-processing program to make it a CNC processing program that can be recognized by the machine tool and input into the CNC machine tool.

6. The ultrasonic-assisted machining method for fiber-reinforced ceramic matrix composite thin-walled parts according to claim 1, characterized in that: The ultrasonic machining parameters are determined by performing a process test on a test piece made of the same material using an orthogonal test method and a single factor test method to determine the ultrasonic machining parameters.

7. The ultrasonic-assisted machining method for fiber-reinforced ceramic matrix composite thin-walled parts according to claim 1, characterized in that: The completing ultrasonic assisted machining of the workpiece specifically includes: using a CNC program corresponding to the product to complete the ultrasonic assisted machining of the product.

8. The ultrasonic-assisted machining method for fiber-reinforced ceramic matrix composite thin-walled parts according to claim 1, characterized in that: The post-processing of the workpiece is specifically as follows: after the workpiece processing is completed, burrs are polished with fine sandpaper and excess materials on the product surface are cleaned.

9. The ultrasonic-assisted machining method for fiber-reinforced ceramic matrix composite thin-walled parts according to claim 1, characterized in that: The three-coordinate process is used to inspect product accuracy and processing quality. Specifically, a three-coordinate measuring machine is used to inspect the surface of the finished product to evaluate whether the processing accuracy and surface quality meet the design requirements. Based on the evaluation results, the processing path and subsequent steps are redesigned to optimize the processing parameters and path to improve the processing quality.

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