A SiC f Method for drilling oblique small holes in SiC ceramic matrix composites

Abstract

This invention belongs to the field of ceramic matrix composite material machining technology, and discloses a SiC f A method for drilling small, oblique holes in SiC ceramic matrix composites includes: using a grinding head with applied ultrasonic vibration to drill the SiC... f The SiC ceramic matrix composite workpiece is subjected to dot-mapping to form a slanted small hole inlet platform; an ultrasonically vibrating drill bit is used at the slanted small hole inlet platform to drill the SiC to be processed. f This invention aims to solve the problem of drilling oblique small holes in SiC ceramic matrix composite workpieces. f The high hardness, brittleness, and inhomogeneity of SiC ceramic matrix composites present technical challenges, such as difficulty in drilling small oblique holes and easy tool breakage during the machining process.

Description

Technical Field

[0001] This invention belongs to the field of ceramic matrix composite material machining technology, specifically relating to a SiC... f / SiC ceramic matrix composite material oblique small hole drilling method. Background Technology

[0002] SiC f SiC ceramic matrix composites are mainly composed of silicon carbide fibers and a silicon carbide matrix. They possess characteristics such as low density, high temperature resistance, and high hardness, making them promising for applications in advanced aero-engine hot-section components. However, SiC... f The high hardness, brittleness, and inhomogeneity of SiC ceramic matrix composites present challenges in machining, including significant tool wear, difficulty in machining, and poor machinability. f In practical applications, high-temperature resistant components made of SiC ceramic matrix composites still incorporate numerous small holes, mostly angled, to enhance the material's heat resistance. f When drilling small, angled holes in SiC ceramic matrix composites, the inclined tool at the hole entrance experiences unilateral force, easily generating significant lateral forces that make the tool highly susceptible to breakage. Furthermore, the material's hardness, brittleness, and porosity make traditional drilling methods difficult for SiC. f Machining of oblique small holes in SiC ceramic matrix composites.

[0003] The paper "Ultrasonic Vibration Assisted Dry Drilling of SiC" published by Chen Yurong et al. in Aeronautical Manufacturing Technology, 2018, 61(21):47-51 f The experimental study on SiC ceramic matrix composites suggests that due to SiC... f The hardness and brittleness of SiC ceramic matrix composites, coupled with the high cutting forces and temperatures during drilling, easily lead to rapid tool wear and failure. Furthermore, this study focused on straight drilling with a diameter of 4.28 mm. Compared to drilling small-diameter inclined holes, the tool design and manufacturing processes are more mature, the tool rigidity is greater, and the possibility of tool breakage during drilling is relatively much lower. Therefore, the conclusions of this study cannot be applied to drilling small-diameter inclined holes. (Zhang Ruoheng, in his master's thesis "SiC...") f The study on ultrafast laser processing technology and properties of SiC composite materials suggests that at low laser power, SiC… fUltrafast laser processing of SiC ceramic matrix composites can result in large hole taper. While ultrafast laser processing can reduce hole taper when the laser power is high, it can easily cause significant ablation damage to the hole. The SiC fibers and SiC matrix on the hole wall and around the hole will be completely oxidized, resulting in a large number of pores and thermal ablation phenomena in the laser processing area, leading to poor hole processing quality.

[0004] In conclusion, neither of the two articles published above can solve the problem in SiC. f The challenge of machining high-quality oblique small holes on SiC ceramic matrix composites. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a SiC f The purpose of this method is to solve the problem of drilling small, oblique holes in SiC ceramic matrix composites. f The high hardness, brittleness, and inhomogeneity of SiC ceramic matrix composites present technical challenges, including difficulties in drilling small, oblique holes and the tendency for cutting tools to break during the machining process.

[0006] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution:

[0007] A SiC f Methods for drilling oblique small holes in SiC ceramic matrix composites include:

[0008] A grinding head with applied ultrasonic vibration is used to process SiC f / SiC ceramic matrix composite workpieces are processed with dot-hole machining to form oblique small hole inlet platforms;

[0009] The SiC to be processed is drilled using a drill bit with applied ultrasonic vibration at the inlet platform of the inclined hole. f Slanted small hole drilling is performed on SiC ceramic matrix composite workpieces.

[0010] Furthermore, the ultrasonic vibration applied to the grinding head has a vibration frequency of 17kHz to 20kHz and a vibration amplitude of 2µm to 3µm.

[0011] Furthermore, the grinding head is a diamond grinding head with a diameter of 0.7mm to 1.2mm, and the particle size of the diamond abrasive on the grinding head is 100 to 200 mesh.

[0012] Furthermore, the processing parameters for the dotting process include: spindle speed of 17000 r / min, feed rate of 1 mm / min, and pecking step length of 0.01 mm.

[0013] Furthermore, the ultrasonic vibration applied to the drill bit has a vibration frequency of 17kHz to 20kHz and a vibration amplitude of 2µm to 3µm.

[0014] Furthermore, the drill bit is a PDC drill bit with a diameter of 0.7mm to 1.2mm, and the drill bit tip angle is designed as a composite angle.

[0015] Furthermore, the machining parameters during the drilling process include: spindle speed of 17000 r / min, feed rate of 2 mm / min, and drill step length of 0.01 mm to 0.05 mm.

[0016] Furthermore, the grinding head subjected to ultrasonic vibration is used to process SiC f Before the dotting process is performed on SiC ceramic matrix composite workpieces, the following steps are also included:

[0017] For the SiC to be processed f / SiC ceramic matrix composite workpieces undergo surface finishing.

[0018] Furthermore, the SiC to be processed f When performing dot-mapping and inclined small-hole drilling on SiC ceramic matrix composite workpieces, a combination of emulsion and high-pressure atomization cooling is used.

[0019] Furthermore, an ultrasonic vibration-assisted drilling device is assembled and connected with a five-axis vertical machining center to apply ultrasonic vibration to the grinding head and drill bit.

[0020] Compared with the prior art, the present invention has at least the following beneficial effects:

[0021] This invention provides a SiC f The method for drilling small holes in SiC ceramic matrix composites first employs a grinding head with applied ultrasonic vibration to the SiC to be machined. f The SiC ceramic matrix composite workpiece is subjected to dot-mapping to form a beveled inlet platform for small holes. This reduces the lateral force on small-diameter tools during machining, allowing for smooth drilling and avoiding the problems of tool breakage and difficulty in drilling before the drill bit enters the bevel when directly machining small holes on the bevel. Finally, a drill bit with ultrasonic vibration is used at the beveled inlet platform position to machine the SiC ceramic matrix composite workpiece. f This invention enables the machining of oblique small holes in SiC ceramic matrix composite workpieces. Leveraging the advantages of ultrasonic vibration-assisted drilling, it combines ultrasonic vibration with drilling operations. Based on the relative motion between the cutting tool and the workpiece, externally excited high-frequency periodic vibration is applied to the tool, thereby reducing the contact time and friction coefficient between the tool and workpiece, lowering cutting force and heat, and improving tool durability. This allows for the machining of hard, brittle, and difficult-to-machine SiC ceramic matrix composite workpieces. fThe processing of SiC ceramic matrix composites. In summary, this invention effectively solves the problem caused by SiC... f The high hardness, brittleness, and inhomogeneity of SiC ceramic matrix composites make it difficult to perform small-diameter drilling and cause tool breakage during the machining process.

[0022] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the specific embodiments of the present invention, the drawings used in the description of the specific embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0024] Figure 1 This is a topographic view of the inclined hole inlet in an embodiment of the present invention;

[0025] Figure 2 This is a topographic view of the outlet of the inclined hole drilled in an embodiment of the present invention. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] As a specific embodiment of the present invention, a SiC f The method for drilling oblique small holes in SiC ceramic matrix composites includes the following steps:

[0028] 1. Assemble and connect the ultrasonic vibration-assisted drilling device with the five-axis vertical machining center.

[0029] 2. The SiC to be processed after surface finishing f / SiC ceramic matrix composite workpieces are clamped on a five-axis vertical machining center using special tooling.

[0030] 3. Select grinding head and drill bit

[0031] 3.1 Select diamond grinding heads with a diameter of 0.7mm to 1.2mm and a diamond abrasive grain size of 100 to 200 mesh.

[0032] 3.2 Select PDC drill bits with a diameter of 0.7mm to 1.2mm, and design the drill bit tip angle as a compound angle.

[0033] 4. Operate the five-axis vertical machining center to mount the SiC to be machined, which is clamped on a special fixture. f / SiC ceramic matrix composite workpieces are adjusted and placed at the tilt angle required by the process.

[0034] 5. Select cooling method: SiC to be processed f The drilling process for SiC ceramic matrix composite workpieces employs a combination of emulsion and high-pressure atomization cooling.

[0035] 6. Operate the equipment to process the SiC. f Slanted small hole drilling of SiC ceramic matrix composite workpieces.

[0036] 6.1 A diamond grinding head is used to complete the pitting process to obtain a platform at the entrance of the inclined small hole of the drill bit.

[0037] 1) Install a diamond grinding head with a diameter of 0.7mm to 1.2mm onto the ultrasonic drilling tool holder.

[0038] 2) Turn on the power of the ultrasonic vibration-assisted drilling device. The frequency range of the ultrasonic vibration is 17kHz to 20kHz. Test the vibration state of the ultrasonic vibration device. Use an LV-S20 self-focusing laser vibrometer to detect the vibration amplitude of the grinding head. The vibration amplitude should be controlled between 2µm and 3µm.

[0039] 3) Set the drilling parameters as follows: spindle speed 17000r / min, feed rate 1mm / min, and drill step length 0.01mm.

[0040] 4) Operate a five-axis vertical machining center to complete the dot-mapping process.

[0041] 6.2 Turn off the power to the ultrasonic vibration-assisted drilling device and remove the Ф0.7mm~Ф1.2mm diamond grinding head from the ultrasonic drilling tool holder.

[0042] 6.3 Using a PDC drill bit, complete the processing of the SiC to be processed. f Drilling of oblique small holes in SiC ceramic matrix composite workpieces.

[0043] 1) Install the PDC drill bit with a diameter of 0.7mm to 1.2mm onto the ultrasonic drilling shank.

[0044] 2) Turn on the power of the ultrasonic vibration-assisted drilling device. The frequency range of the ultrasonic vibration is 17kHz to 20kHz. Test the vibration state of the ultrasonic vibration device. Use an LV-S20 self-focusing laser vibrometer to detect the vibration amplitude of the grinding head. The vibration amplitude should be controlled between 2µm and 3µm.

[0045] 3) Set the drilling parameters as follows: spindle speed 17000r / min, feed rate 2mm / min, and drill step length 0.01mm~0.05mm.

[0046] 4) Operate a five-axis vertical machining center on the SiC to be machined. f On a SiC ceramic matrix composite workpiece, a small inclined hole is drilled through the area where the pitting process is completed, and the entire inclined hole is completed.

[0047] 6.4 After completing the drilling of the 0.7mm to 1.2mm oblique holes, turn off the power of the ultrasonic vibration assisted drilling system.

[0048] This invention analyzes SiC f The machining of oblique small holes in SiC ceramic matrix composites presents a challenge, which is addressed by introducing ultrasonic vibration-assisted drilling technology. Ultrasonic vibration-assisted drilling combines ultrasonic vibration with drilling operations. Based on the relative motion between the cutting tool and the workpiece, externally excited high-frequency periodic vibration is applied to the tool or workpiece, thereby reducing the contact time and friction coefficient between the tool and workpiece, lowering cutting force and heat, and improving tool durability. This enables the machining of hard and brittle materials that are difficult to machine. In SiC… f In the drilling of small inclined holes in SiC ceramic matrix composites, an ultrasonic vibration-assisted drilling process was employed. This, combined with optimized tool structure, machining process, and process parameters, reduced cutting forces and improved tool life, thus solving the problem of SiC… f Machining challenges in drilling oblique small holes in SiC ceramic matrix composites.

[0049] The SiC of the present invention f This method for drilling inclined small holes in SiC ceramic matrix composites leverages the advantages of ultrasonic vibration-assisted drilling technology. By selecting an appropriate ultrasonic amplitude, cutting forces, cutting heat, and tool wear are reduced during the drilling process, thus improving tool durability. During machining, a diamond grinding head is first used to create a pit, reducing the lateral force on the small-diameter tool and ensuring smooth drilling entry. This avoids the problem of tool breakage and difficulty in drilling before penetration when directly drilling small holes on an inclined surface. Secondly, a PDC drill bit with high hardness, good wear resistance, and designed with spiral flutes and a compound apex angle is used to drill into the small platform formed by the pit. Using reasonable ultrasonic drilling process parameters, the machining of inclined small holes is achieved. The dimensional and shape accuracy of the machined inclined small holes meet the design requirements, realizing the machining of SiC.f The machining of tiny oblique holes in SiC ceramic matrix composite specimens has driven a breakthrough in the precision machining technology of ceramic matrix composite components, laying a certain technical foundation for promoting the engineering application of ceramic matrix composites.

[0050] In one specific embodiment, a SiC f The specific method for drilling oblique small holes in SiC ceramic matrix composite materials is as follows:

[0051] 1. Assemble and connect the ultrasonic vibration-assisted drilling device with the five-axis vertical machining center.

[0052] In this embodiment, a BMC-630V five-axis vertical machining center and an ultrasonic vibration drilling device with an ultrasonic vibration frequency of 17.5kHz are used.

[0053] The ultrasonic vibration-assisted drilling device includes an ultrasonic generator, an energy transmission unit (including a transmission line, a retainer, and a magnetic head), and an ultrasonic drilling tool holder (including a transducer and an amplitude transformer). An ultrasonic tool holder with a vibration frequency of 17.5 kHz is selected and installed on the spindle of a five-axis vertical machining center. The ultrasonic generator is then connected to the magnetic head using the transmission line. Finally, the magnetic head is fixed using the retainer. Before fixing, the distance between the ultrasonic drilling tool holder and the magnetic head must be controlled at 0.4 ± 0.1 mm to ensure that the magnetic head does not contact the ultrasonic tool holder.

[0054] 2. Surface-finished SiC with dimensions of 38mm × 20mm × 2mm f / SiC ceramic matrix composite specimens were clamped on a five-axis vertical machining center using special tooling.

[0055] 3. Select grinding head and drill bit

[0056] 3.1 Select a Ф0.7mm diamond grinding head with 100 mesh diamond abrasive grains, a tool holder base material of 45 steel, and a nickel-based binder for the abrasive grains.

[0057] 3.2 Select a Ф0.7mm PDC drill bit with a Ф4mm shank diameter, a total tool length of 50mm, a spiral chip flute length of 4mm, a diamond layer length of 1.5mm, and a tool tip angle designed as a 120° / 50° composite tip angle.

[0058] 4. Operate the five-axis vertical machining center, and adjust the placement of the test piece clamped on the special tooling so that the tilt angle between the spindle drill and the test piece is 25°.

[0059] 5. Select the cooling method. SiC f The drilling process of the SiC ceramic matrix composite oblique small hole specimens adopted a combination of emulsion and high-pressure atomization cooling.

[0060] 6. Operate the equipment to perform SiC processing. f Slanted small hole drilling of SiC ceramic matrix composite specimens.

[0061] 6.1 A diamond grinding head is used to complete the pitting process to obtain a platform at the entrance of the inclined small hole of the drill bit.

[0062] 1) Install the 0.7mm diamond grinding head on the ultrasonic drilling tool holder.

[0063] 2) Turn on the power of the ultrasonic vibration-assisted drilling device, test the vibration state of the ultrasonic vibration device, use the LV-S20 self-focusing laser vibrometer to detect the vibration amplitude of the grinding head, and adjust the tool overhang to keep the amplitude at 2μm.

[0064] 3) Set the denting machining parameters as follows: spindle speed 17000r / min, feed rate 1mm / min, pecking step length 0.01mm, and denting depth 1.5mm.

[0065] 4) Operate a five-axis vertical machining center to complete the dot-mapping process.

[0066] 6.2 Turn off the power to the ultrasonic vibration-assisted drilling device and remove the Ф0.7mm diamond grinding head from the ultrasonic tool holder.

[0067] 6.3 Using a PDC drill bit, complete the SiC... f Drilling of oblique small holes in SiC ceramic matrix composites.

[0068] 1) Install the 0.7mm PDC drill bit on the ultrasonic drilling shank.

[0069] 2) Turn on the power of the ultrasonic vibration-assisted drilling device, test the vibration state of the ultrasonic vibration device, use the LV-S20 self-focusing laser vibrometer to detect the vibration amplitude of the grinding head, and adjust the tool overhang to about 22mm to keep the amplitude at 2μm.

[0070] 3) Set the drilling parameters as follows: spindle speed 17000r / min, feed rate 2mm / min, pecking step length 0.01mm, and drilling depth 4mm.

[0071] 4) Operate a five-axis vertical machining center in SiC f On the SiC ceramic matrix composite specimen, the area where the pitting process was completed was drilled at an angle to create a small hole. The hole was drilled through the specimen to complete the machining of the entire angled hole.

[0072] 6.4 After completing the drilling of the 0.7mm oblique hole, turn off the power to the ultrasonic vibration-assisted drilling system. In this embodiment, the inlet and outlet morphologies of the drilled oblique hole are as follows: Figure 1 and Figure 2 As shown.

[0073] In this embodiment, a diamond grinding head was used with the following process parameters: spindle speed 17000 r / min, feed rate 1 mm / min, drill step length 0.01 mm, ultrasonic frequency 17.5 kHz, and ultrasonic amplitude 2 μm, for pitting machining. A PDC drill bit was used with the following process parameters: spindle speed 17000 r / min, feed rate 2 mm / min, drill step length 0.01 mm, ultrasonic frequency 17.5 kHz, and ultrasonic amplitude 2 μm, for drilling small inclined holes. The results show that using the SiC of this invention... f A method for drilling oblique small holes in SiC ceramic matrix composites has been achieved. f Slanted small hole drilling with a diameter of Ф0.7mm and a hole inclination angle of 25° in SiC ceramic matrix composite material.

[0074] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0075] Finally, it should be noted that the above-described embodiments are merely specific implementations of the present invention, used to illustrate the technical solutions of the present invention, and not to limit it. The scope of protection of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art can still modify or easily conceive of changes to the technical solutions described in the foregoing embodiments within the technical scope disclosed in the present invention, or make equivalent substitutions for some of the technical features; and these modifications, changes, or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A SiC f A method for drilling oblique small holes in SiC ceramic matrix composite materials, characterized in that... include: A grinding head with applied ultrasonic vibration is used to process SiC f The SiC ceramic matrix composite workpiece is subjected to dot-hole processing to form an oblique small hole inlet platform; the ultrasonic vibration applied to the grinding head has a vibration frequency of 17kHz to 20kHz and a vibration amplitude of 2µm to 3µm. The SiC to be processed is drilled using a drill bit with applied ultrasonic vibration at the inlet platform of the inclined hole. f The SiC ceramic matrix composite workpiece is subjected to inclined small-hole drilling; the ultrasonic vibration applied to the drill bit has a vibration frequency of 17kHz to 20kHz and a vibration amplitude of 2µm to 3µm; the drill bit is a Ф0.7mm to Ф1.2mm PDC drill bit, and the drill bit tip angle is designed as a composite angle; the SiC to be processed is then subjected to this process. f When performing pitting and small-hole drilling on SiC ceramic matrix composite workpieces, a combination of emulsion and high-pressure atomization cooling is used. The grinding head is a diamond grinding head with a diameter of 0.7mm to 1.2mm, and the grit size of the diamond abrasive on the grinding head is 100 to 200 mesh. The machining parameters for the dotting process include: spindle speed of 17000 r / min, feed rate of 1 mm / min, and pecking step length of 0.01 mm. The machining parameters during drilling include: spindle speed of 17000 r / min, feed rate of 2 mm / min, and drill step length of 0.01 mm to 0.05 mm.

2. A SiC according to claim 1 f A method for drilling oblique small holes in SiC ceramic matrix composite materials, characterized in that... The SiC to be processed is produced using a grinding head that applies ultrasonic vibration. f Before the dotting process is performed on SiC ceramic matrix composite workpieces, the following steps are also included: For the SiC to be processed f / SiC ceramic matrix composite workpieces undergo surface finishing.

3. A SiC according to claim 1 f A method for drilling oblique small holes in SiC ceramic matrix composite materials, characterized in that... An ultrasonic vibration-assisted drilling device is assembled and connected to a five-axis vertical machining center to apply ultrasonic vibration to the grinding head and drill bit.

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