Dual-robot collaborative laser ultrasonic edge milling method for carbon fiber composite materials

Abstract

The present invention discloses a dual-robot collaborative laser ultrasonic milling-edge method for carbon fiber composite materials, and proposes to combine the robot laser cutting-edge technology with the robot ultrasonic milling-edge to improve the quality and efficiency of robot milling-edge. First, a dual-robot laser ultrasonic milling-edge system is built. Secondly, experimental studies on robot laser cutting-edge of carbon fiber composite materials and experimental studies on robot ultrasonic milling-edge are carried out. Finally, research on dual-robot collaborative laser ultrasonic milling-edge is carried out. The results show that: the processing quality and processing efficiency of carbon fiber composite parts after robot laser cutting-edge and robot ultrasonic milling-edge are significantly improved, and combining laser cutting-edge with ultrasonic milling-edge is an effective way to improve the processing quality and efficiency of robot-milled carbon fiber composite parts.

Description

Technical Field

[0001] The present invention belongs to the field of robot processing, and particularly relates to a dual-robot collaborative laser ultrasonic edge milling method for carbon fiber composite materials. The main content is to propose combining robot laser edge cutting technology with robot ultrasonic edge milling technology to improve the edge milling efficiency and quality of carbon fiber composite parts. Background Art

[0002] In recent years, with the continuous breakthroughs in manufacturing technologies in fields such as aerospace, automotive, petrochemical, and civilian life, the corresponding requirements for materials have also been developing towards high-performance directions such as high strength and lightweight. Traditional metal or alloy materials can no longer fully meet the requirements of new technology development. In contrast, carbon fiber composite materials such as polymer materials not only have properties such as high specific strength, high specific modulus, and lightweight, but also carbon fiber composite materials have high heat resistance, structural designability, strong anti-fatigue, corrosion resistance, anti-vibration, and electromagnetic shielding capabilities, which are more in line with the industry development trend. However, due to its poor forming accuracy, a margin is usually left as a sacrificial layer at the edge of the component during the forming process and is removed by milling after curing, which is called edge milling to meet the assembly and connection requirements with other components. For the edge milling of large-sized carbon fiber composite parts, existing traditional machine tools have limitations in processing stroke, the cost of developing special machine tools is high, and manual edge cutting has low efficiency and poor accuracy. Therefore, it has become a trend to use industrial robots with high flexibility and low cost for the edge milling of large-sized carbon fiber composites. Ultrasonic machining is a new technology that applies high-frequency vibration at the end of the tool to assist in cutting materials. Existing research results show that the combination of a robot and ultrasonic vibration can effectively suppress milling chatter, improve machining quality, and increase machining efficiency. However, the cutting depth of robot ultrasonic edge milling usually needs to be greater than the thickness of the carbon fiber composite part (full cutting depth), and the cutting width is generally the tool diameter (full cutting width), resulting in excessive cutting force fluctuations that are likely to cause milling deformation and machining vibration of the workpiece and the robot, seriously affecting the machining accuracy. In recent years, with the rapid development of laser technology, many scholars have used innovative laser edge cutting technology to process carbon fiber composite materials and obtained good machining quality. Some researchers have shown through experiments that using short-wavelength ultraviolet laser to process carbon fiber composite materials can obtain better machining quality, and the width of the heat-affected zone can also be limited within dozens of micrometers. This is mainly because short-wavelength lasers use photochemical effects to remove materials, which can greatly reduce the thermal damage of the short laser beam to the material. Some scholars have also used ultrafast pulsed lasers and multi-pass cutting to control the heat-affected zone within dozens of micrometers, greatly improving the machining quality. The greatest advantage of robot laser edge cutting is that it enables the robot machining system to have no direct contact with the workpiece, avoiding machining chatter caused by excessive dynamic cutting force. However, there is extremely easy to be a heat-damaged area on the surface after laser edge cutting of carbon fiber composite materials, and a finishing process is still required to meet the machining quality requirements. Summary of the Invention

[0003] The object of the present invention is to provide a dual-robot collaborative laser ultrasonic milling edge method for carbon fiber composite materials, which combines robot laser cutting edge technology with robot ultrasonic milling to improve the quality and efficiency of robot milling edge. To achieve the above object, the present invention adopts the following technical solutions:

[0004] A dual-robot collaborative laser ultrasonic milling edge method for carbon fiber composite materials, comprising the following steps:

[0005] Step 1: Establishment of a dual-robot laser ultrasonic milling edge system: The dual-robot laser ultrasonic milling edge system includes a robot laser cutting edge system module, a robot ultrasonic processing system module, a measurement system module, and an interference and collision detection module;

[0006] Step 2: Conduct experimental research on robot laser cutting edge: Study the influence of different processing parameters on the width and softening degree of the thermal damage area. On the one hand, select the tool diameter accordingly. On the other hand, establish a mapping model between the processing parameters and the width of the damage area at different thicknesses. Finally, obtain the appropriate feed speed and laser power;

[0007] Step 3: Experimental research on robot ultrasonic milling edge: Study the influence of the softening of the thermal damage area of laser cutting edge on the cutting force and milling edge stability of ultrasonic milling edge. Study the influence of laser cutting edge processing parameters on the quality of robot ultrasonic milling edge. Obtain the matching characteristics of robot laser cutting edge and robot ultrasonic milling edge processes, so as to determine the appropriate processing parameters;

[0008] Step 4: Conduct dual-robot collaborative laser ultrasonic milling edge: First, formulate the processing parameters of the dual-robot collaborative laser ultrasonic milling edge scheme. Secondly, in order to avoid interference and collision in dual-robot collaborative processing, conduct simulation of the dual-robot collaborative laser ultrasonic milling edge scheme. Finally, conduct dual-robot collaborative laser ultrasonic milling edge processing.

[0009] Further, the specific content of Step 1 is as follows:

[0010] Construction of the Robot Laser Edge Cutting System Module: The robot laser edge cutting system consists of two parts, hardware and software. The hardware part includes the robot system, laser system, laser cutting head, and robot controller. The software part includes the offline programming system and communication transmission system. The robot system uses the robotic arm as the motion carrier, which can drive the laser cutting head to process the workpiece. The user can manually teach through the teach pendant or generate a processing trajectory matching the product through the offline software. The robot controller controls the movement of the robotic arm. The laser system includes a fiber laser, a follower, and a proportional valve. The fiber laser can generate lasers of various wavelengths as the light source for cutting. The laser cutting head focuses the laser. The follower can adjust the distance between the laser cutting head and the workpiece surface in real time and provide auxiliary gas for cutting according to different metal materials. The proportional valve is used to regulate the gas flow. The robot controller can save and modify the motion trajectory and cutting process, and can display the position and posture of the robot and the cutting progress in real time. It also has the function of a process database. The communication transmission system is used to receive the robot start and emergency stop signals given by the robot controller and send them to the robot, and at the same time receive digital signals such as laser switch, follower head switch, and solenoid valve switch given by the controller, as well as analog signals such as laser power, frequency, duty cycle, and air pressure. The offline programming system is used to realize virtual robot control, cycle time analysis, and generation of robot programs;

[0011] Construction of the Robot Ultrasonic Machining System Module: The ultrasonic machining system consists of an ultrasonic vibration system and a robot end effector. The ultrasonic vibration system consists of an ultrasonic generator, an electrical energy transmission module, and an ultrasonic vibration system. First, the ultrasonic signal generation module can convert the 220V voltage provided by the ultrasonic power supply into an electrical signal, and then the transducer converts the electrical signal into a vibration signal with the same frequency. Then, through the amplification of the horn, the amplitude of the vibration signal is increased, and the amplified amplitude signal is transmitted to the milling cutter, so that the milling cutter generates an axial vibration with a certain frequency. The robot spindle holds the tool holder to fix the ultrasonic vibration system on the spindle, and uses a bracket to fix the non-contact electrical energy transmission port on the spindle to keep a certain distance from the ultrasonic transducer to facilitate the transmission of electrical signals between the magnetic coils. The gland is used to press the transducer tightly to fix the ultrasonic transducer and the horn together. The ultrasonic transducer is used to convert the electrical signal into a vibration signal and convert electrical energy into mechanical energy. The horn is used to amplify the amplitude of the ultrasonic vibration and change the vibration direction, and transmit the amplified vibration signal to the tool to make it generate high-frequency vibration. After the robot ultrasonic machining system is assembled, the power supply of the end effector device is turned on, and then its performance is tested. The ultrasonic transducer is connected to the ultrasonic power supply alone for a matching test, and a multimeter is used to observe the change of the resonant matching frequency. The result shows that the working frequency is within the working frequency range of the power supply. When the metal sheet touches the end face of the transducer, a sound of metal vibration will be generated, indicating that the working performance of the ultrasonic transducer is normal;

[0012] Measurement system module: It includes a digital microscope and a dynamometer. The digital microscope is used to measure the maximum thermal damage width of the edge of the carbon fiber composite part after laser cutting and the surface quality of the carbon fiber composite part after processing. The dynamometer is used to detect the milling force during the experiment;

[0013] Interference and collision detection module: On the TECNOMATIX simulation software, the path of the processing ends of the dual robots is simulated by adding motion commands. According to the results of kinematic calculations, the motion states of the robots are displayed in real time. Users can intuitively understand the rationality of the processing path planning and adjust the processing path points according to the corresponding prompts, so as to avoid interference and collision during the collaborative processing of the dual robots.

[0014] Further, step 2 specifically includes the following steps:

[0015] Step 2.1: Selection of processing parameters for the robot laser cutting experiment: Select the processing parameter range of the carbon fiber composite part thickness of 0.5 mm - 5 mm, the laser power of 500 - 20 kw, and the cutting speed of 1.0 - 10.0 m / min. The single-factor experiment method is used to conduct the carbon fiber composite cutting experiment under different processing parameters;

[0016] Step 2.2: Use the robot laser cutting system module to conduct the robot laser cutting experiment: First, on the robot controller, debug the ROBOGUIDE programming software for parameter setting and laser cutting programming. After the programming is completed and checked and confirmed, run the laser cutting system without turning on the laser. If an error occurs, re-debug the ROBOGUIDE programming software. If no error occurs, turn on the power of the end effector device and officially run the robot laser cutting system module. The robot moves the end effector to the position to be processed. The robot gives a signal of reaching the position to the robot controller through I / O. The internal program of the robot controller starts to execute. The laser beam moves relative to the carbon fiber composite part along the processing path, so that more and more materials are removed by heat, thus forming a cut. At the same time, the residues at the cut are also removed by the high-pressure auxiliary gas, thus completing the laser cutting process of the carbon fiber composite part. After the cutting action is completed, the robot controller gives a signal of the action completion to the robot through I / O, and judges whether all the cutting tasks have been completed. If all the tasks have not been completed, the end effector repeats the laser cutting process; if all the tasks have been completed, the end effector returns to the program setting point, and the program ends after reaching the position;

[0017] Step 2.3. Use the measurement system module to measure the maximum thermal damage width of the edge of the laser-cut carbon fiber composite part: Observe the microscopic morphology of the cut surface using a digital microscope, and select the distance from the edge of the cut to the maximum matrix damage to represent the maximum width value of the heat-affected zone, denoted as HAZ. Measure the maximum width of the heat-affected zone of the carbon fiber composite after the laser cutting experiment, and record the data;

[0018] Step 2.4. Establish a mapping model between the processing parameters and the width of the damage area at different thicknesses: Therefore, use MINITAB software to analyze the experimental results after robotic laser cutting, and obtain the mapping model between the processing parameters and the width of the damage area at different thicknesses. According to the established mapping model, obtain the laser power and feed rate corresponding to the best processing effect of the carbon fiber composite parts at different thicknesses.

[0019] Further, step 3 specifically includes the following steps:

[0020] Step 3.1. Set the processing parameters for the robotic ultrasonic milling edge experiment: Select the processing parameter range of a milling edge length of 30 - 50 mm, a feed rate of 1.0 - 3.0 m / min, and a spindle speed of 3000 - 5000 r / min. Use a PCD milling cutter with a diameter larger than the maximum thermal damage width to conduct a robotic ultrasonic milling edge experiment on the laser-cut carbon fiber composite part;

[0021] Step 3.2. Use the robotic ultrasonic machining system module to conduct an ultrasonic milling edge experiment on the laser-cut carbon fiber composite part, and simultaneously use a dynamometer to collect the real-time signal of the cutting force: The robot moves the end effector to the position to be processed. The robot gives a signal of reaching the position to the robot controller through I / O, and the internal program of the robot controller starts to execute. When the ultrasonic milling edge processes the laser-processed carbon fiber composite part, the milling cutter rotates at high speed along the feed direction, and at the same time, the vibration signal generated by the ultrasonic system is transmitted to the milling cutter, causing the milling cutter to generate high-frequency axial vibration, resulting in the periodic separation of the milling cutter from the processed carbon fiber composite part during the milling edge process. The carbon fiber composite to be removed is continuously removed after being subjected to high-frequency impacts by the milling cutter, thereby completing the ultrasonic milling edge processing of the laser-cut carbon fiber composite part. After the milling edge is completed, the robot controller gives an action completion signal to the robot through I / O, and the end effector returns to the program-set origin, and the program ends after reaching the position;

[0022] Step 3.3: Use the measurement system module to measure the surface roughness of the machined area of the carbon fiber composite parts after edge milling. For each group of carbon fiber composite parts after edge milling experiments, select 3 areas as the measurement positions for surface roughness, measure a total of 3 groups of surface roughness data, and then calculate the average value of these 3 groups of data as the surface roughness value of the carbon fiber composite parts after each edge milling experiment. Import the milling force data collected by the dynamometer into the MATLAB software to obtain the magnitude of the milling force during the entire edge milling experiment;

[0023] Step 3.4: Study the influence of the softening of the heat-affected zone of laser cutting on the ultrasonic edge milling cutting force and edge milling stability; During the laser cutting process, the high-energy laser beam will generate significant thermal stress on the heat-affected zone of the carbon fiber composite, resulting in obvious burning and softening phenomena of the carbon fiber composite. Different laser processing parameters cause different degrees of thermal damage, and different degrees of thermal damage result in different degrees of burning and softening of the carbon fiber composite, leading to different degrees of reduction in the milling force during subsequent ultrasonic milling experiments and different gain effects on the edge milling stability. According to the experimental results, it is found that in order to minimize the milling force during edge milling, a larger laser power and a smaller laser cutting speed should be selected;

[0024] Step 3.5: Study the influence of laser cutting processing parameters on the quality of robotic ultrasonic edge milling, obtain the matching characteristics of robotic laser cutting and robotic ultrasonic edge milling processes, and thus determine the appropriate processing parameters: By analyzing the quality of robotic ultrasonic edge milling, it is found that the edge milling quality of carbon fiber composites after edge cutting with different laser processing parameters is different. According to the experimental results, it is found that the influence of different laser processing parameters on the edge milling quality has a certain regularity, and the MINITAB software is used to analyze the experimental results to obtain the matching characteristics of robotic laser cutting and robotic ultrasonic edge milling processes. Finally, the corresponding processing parameters when the edge milling quality is the best are determined according to the matching characteristics.

[0025] Furthermore, the specific steps of Step 4 are as follows:

[0026] Step 4.1: Formulate the processing parameters of the dual-robot collaborative laser ultrasonic edge milling scheme: Select the processing parameters with the best processing quality obtained in Steps 2 and 3 as the processing parameters of the collaborative laser ultrasonic edge milling scheme, and carry out the dual-robot laser ultrasonic collaborative processing of carbon fiber composites;

[0027] Step 4.2: Conduct simulation of the dual-robot collaborative laser ultrasonic edge milling scheme: On the TECNOMATIX simulation software, simulate the paths of the processing ends of the dual robots by adding motion commands, detect interference and collision situations, and display the robot motion states in real time according to the kinematic calculation results. Users can intuitively understand the rationality of the processing path planning and adjust the processing path points according to the corresponding prompts, so as to ensure that each module can achieve the motion space required for system processing and avoid interference and collision during the collaborative processing of robots;

[0028] Step 4.3: Carry out dual-robot collaborative laser ultrasonic edge milling processing: After clamping the workpiece, adjust the postures of the dual robots, then set the corresponding processing parameters, and at the same time turn on the robot laser cutting edge system module and the robot ultrasonic processing system module. The robot moves the end effector to the position to be processed. The robot sends a signal indicating arrival to the robot controller through I / O. The internal program of the robot controller starts to execute, and starts the dual-robot collaborative laser ultrasonic edge milling processing of the carbon fiber composite material part. After waiting for the final processing to be completed, the robot controller sends an action completion signal to the two robots respectively through I / O. The end effector returns to the program-set origin, and the program ends after arriving.

[0029] Compared with the prior art, the advantages of the present invention include:

[0030] (1) During the process of the robot laser cutting the carbon fiber composite material part, there is no tool wear, the automation degree is high, the cutting speed is fast, the noise during processing is low, the vibration is small, the toxic dust generated by laser cutting only accounts for 10% of the existing method, the environmental pollution is small, and multiple high-cost processing procedures can be reduced, the process flow is shortened, and the processing efficiency is improved. At the same time, the robot occupies a small space, which is beneficial to the optimization of the production layout, saves the production space and greatly reduces the processing cost.

[0031] (2) When the robot ultrasonic edge mills the carbon fiber composite material part after laser cutting by the laser, only the laser cutting damage radiation area (within 1 mm) is removed, the milling force will be greatly reduced, the milling process is more stable, and at the same time, introducing ultrasonic energy can effectively improve the edge milling quality.

[0032] (3) A mapping model between the processing parameters and the width of the damage area under different thicknesses is established, the influence of the softening of the laser cutting thermal damage area on the ultrasonic edge milling cutting force and the edge milling stability is studied, the influence of the laser cutting processing parameters on the quality of the robot ultrasonic edge milling is studied, and the matching characteristics of the robot laser cutting and the robot ultrasonic edge milling processes are obtained, so as to determine the appropriate processing parameters.

[0033] (4) Aiming at the problem of low milling efficiency of large and complex components by robots, the present invention first proposes a robot processing solution that combines laser processing and ultrasonic milling. Through the cooperation of two robots, the workload is distributed to the two robots for execution, effectively reducing the processing time and improving the milling efficiency of the robots.

[0034] In addition to the purposes, features, and advantages described above, the present invention has other purposes, features, and advantages. The present invention will be further described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a flow chart of the method for laser ultrasonic milling of two robots according to the present invention.

[0036] Figure 2 It is a schematic diagram of a two-robot collaborative laser ultrasonic milling system.

[0037] Figure 3 It is a schematic diagram of a robot laser cutting system.

[0038] Figure 4 It is a simplified structural diagram of a robot ultrasonic milling system.

[0039] Figure 5 It is a composition diagram of an ultrasonic vibration system.

[0040] Figure 6 It is a simplified structural diagram of an ultrasonic vibration unit.

[0041] Figure 7 It is a schematic diagram of a laser-cut carbon fiber composite part.

[0042] Figure 8 It is a schematic diagram of a heat-affected zone.

[0043] Figure 9 It is a model diagram of ultrasonic milling.

[0044] Figure 10 It is a schematic diagram of the separation characteristics of an ultrasonic milling tool and a workpiece. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0045] The present invention will be further described below in conjunction with the accompanying drawings of the specification.

[0046] Figure 1 It is a flow chart of the process of robot laser ultrasonic milling of the method of the present invention, specifically including the following steps:

[0047] Step 1: Construction of a two-robot laser ultrasonic milling system: The schematic diagram of the two-robot laser ultrasonic milling system is as Figure 2 shown, which mainly includes a robot laser cutting system module, a robot ultrasonic processing system module, a measurement system module, and an interference and collision detection module.

[0048] Construction of the robot laser trimming system module: As Figure 3 shown, the robot laser trimming system consists of two parts: hardware and software. The hardware part includes a robot, a laser, a laser cutting head, and a robot controller. The software part includes an offline programming system, a communication transmission system, etc. Functions of the robot system: The robotic arm serves as a motion carrier to drive the laser cutting head to process workpieces. Users can manually teach through a teach pendant or generate a machining trajectory matching the product through offline software, and the controller controls the movement of the robotic arm. Functions of the laser system: The fiber laser generates lasers of various wavelength bands as the light source for cutting. The laser cutting head focuses the laser. The follower can adjust the distance between the laser cutting head and the workpiece surface in real time. According to different metal materials, auxiliary gases for cutting are provided, and the proportional valve is used to adjust the gas flow. Functions of the robot controller: It can save and modify the motion trajectory and cutting process, display the position, posture, and cutting progress of the robot in real time, and also has the function of a process database. Functions of the software part: Using corresponding communication transmission technologies, it receives the robot start and emergency stop signals given by the robot controller to the robot, and at the same time receives digital quantity signals such as laser switch, follower head switch, and solenoid valve switch given by the robot controller, as well as analog quantity signals such as laser power, frequency, duty cycle, and air pressure. Using offline programming technology to achieve virtual robot control, cycle time analysis, and generation of robot programs.

[0049] Construction of the robot ultrasonic machining system module: Assemble the robot ultrasonic machining system. As Figure 4 shown, the ultrasonic machining system consists of an ultrasonic vibration system and a robot end effector. The composition of the ultrasonic vibration system is as Figure 5 shown. The ultrasonic vibration system consists of an ultrasonic generator, an electric energy transmission module, and an ultrasonic vibration system. First, the ultrasonic signal generation module can convert the 220V voltage provided by the ultrasonic power supply into an electrical signal, and then through the transducer, the electrical signal is converted into a vibration signal with the same frequency. Then, through the amplification of the horn, the amplitude of the vibration signal is increased, and the amplified amplitude signal is transmitted to the milling cutter, so that the milling cutter generates axial vibration with a certain frequency. The structural schematic diagram of the ultrasonic vibration system is as Figure 6As shown, the robot spindle fixes the ultrasonic vibration system on the spindle by sucking the tool holder. A non-contact power transmission port is fixed on the spindle using a bracket, keeping a certain distance from the ultrasonic transducer to facilitate the transmission of electrical signals between the magnetic coils. The function of the gland is to press the transducer tightly, fixing the ultrasonic transducer and the horn together. The ultrasonic transducer converts electrical signals into vibration signals, converting electrical energy into mechanical energy. The horn amplifies the amplitude of the ultrasonic vibration and changes the vibration direction, and transmits the amplified vibration signal to the tool, causing it to generate high-frequency vibrations. After the robot ultrasonic machining system is assembled, the power of the end effector device is turned on, and then its performance is tested. The ultrasonic transducer is separately connected to the ultrasonic power supply for a matching test. A multimeter is used to observe the change in the resonance matching frequency to observe the change in the resonance matching frequency. The results show that the operating frequency is within the operating frequency range of the power supply. When the metal sheet contacts the end face of the transducer, a sound of metal vibration will be generated, indicating that the ultrasonic transducer is operating normally.

[0050] Measurement system module: The measurement system module includes a digital microscope and a dynamometer. The digital microscope is used to measure the maximum thermal damage width of the edge of the carbon fiber composite part after laser trimming and the surface quality of the carbon fiber composite part after machining. The dynamometer is used to detect the milling force during the experiment.

[0051] Interference and collision detection module: On the TECNOMATIX simulation software, the path of the machining end of the dual robots is simulated by adding motion commands. The look-ahead interpolation method is adopted to pre-interpolate the machining points through caching. According to the kinematic calculation results, the motion state of the robots is displayed in real time. Users can intuitively understand the rationality of the machining path planning and adjust the machining path points according to the corresponding prompts, thus avoiding interference and collision during the collaborative machining of the dual robots.

[0052] Step 2: Conduct experimental research on robot laser trimming: Conducting laser trimming experiments is to determine the width and softening degree of the thermal damage area under different machining parameters (feed rate, laser power, part thickness). On the one hand, the tool diameter can be selected accordingly, and on the other hand, a mapping model between the machining parameters and the width of the damage area at different thicknesses can be established, so as to determine the appropriate feed rate and laser power.

[0053] Step 2.1 Selection of machining parameters for robot laser trimming experimental research: Select the machining parameter range of the carbon fiber composite part thickness from 0.5 mm to 5 mm, the laser power from 500 to 20 kW, and the trimming speed from 1.0 to 10.0 m / min. The single-factor experimental method is used to conduct carbon fiber composite trimming experiments under different machining parameters.

[0054] Step 2.2: Conduct robot laser edge cutting experiment using the robot laser edge cutting system module. First, on the robot controller, debug and program the ROBOGUIDE software for parameter setting and laser edge cutting programming. After the programming is completed and confirmed, run the laser edge cutting system without turning on the laser. If an error occurs, re-debug the ROBOGUIDE programming software. Turn on the power of the end effector device and officially run the laser edge cutting system. The robot moves the end effector to the position to be processed, and the robot gives a signal indicating arrival at the robot controller through I / O, and the internal program of the robot controller starts to execute. As Figure 7 shown, the laser beam continuously moves relative to the carbon fiber composite part along the processing path, causing more and more material to be removed thermally, thus forming a cut. At the same time, the residues at the cut are also removed by the high-pressure auxiliary gas, thereby completing the laser edge cutting of the carbon fiber composite part. After the edge cutting action is completed, the robot controller sends a signal indicating the completion of the action to the robot through I / O. Determine whether all edge cutting tasks have been completed. If all tasks have not been completed, the end effector repeats the laser edge cutting process; if all tasks have been completed, the end effector returns to the program setting point, and the program ends after arriving.

[0055] Step 2.3: Use the measurement system module to measure the maximum thermal damage width of the edge of the carbon fiber composite part after laser edge cutting. Observe the microscopic morphology of the cut surface using a digital microscope, and select the distance from the edge of the cut to the maximum matrix damage to represent the maximum width value of the heat-affected zone, as Figure 8 shown, denoted by HAZ. The maximum width value of the heat-affected zone can be calculated using VK image processing software. Measure the maximum width of the heat-affected zone of the carbon fiber composite after the laser edge cutting experiment and record the data.

[0056] Step 2.4: Establish a mapping model between the processing parameters and the width of the damage area at different thicknesses. At different thicknesses, different processing parameters have different influences on the generated heat-affected zone. According to the experimental results, it can be found that the influence of processing parameters on the width of the damage area at different thicknesses has a certain regularity. Therefore, use MINITAB software to analyze the experimental results after robot laser edge cutting, and a mapping model between the processing parameters and the width of the damage area at different thicknesses can be obtained. Finally, according to the established mapping model, the laser power and feed rate corresponding to the best processing effect of the carbon fiber composite part at different thicknesses can be obtained.

[0057] Step 3: Experimental study on robot ultrasonic edge milling: Study the influence of the softening of the thermally damaged area of laser edge cutting on the cutting force and milling stability of ultrasonic edge milling, study the influence of laser edge cutting processing parameters on the quality of robot ultrasonic edge milling, and obtain the matching characteristics of robot laser edge cutting and robot ultrasonic edge milling processes, so as to determine appropriate processing parameters.

[0058] Step 3.1: Setting the processing parameters for the robot ultrasonic milling edge experiment: Select the processing parameter range of a milling edge length of 30 - 50 mm, a feed rate of 1.0 - 3.0 m / min, and a spindle speed of 3000 - 5000 r / min. Use a PCD milling cutter with a diameter larger than the maximum thermal damage width to conduct a robot ultrasonic milling edge experiment on the carbon fiber composite parts after laser cutting.

[0059] Step 3.2: Use the robot ultrasonic milling edge system module to conduct an ultrasonic milling edge experiment on the carbon fiber composite after laser cutting, and simultaneously use a dynamometer to collect the real-time signal of the cutting force: The robot moves the end effector to the position to be processed. The robot gives a signal of reaching the position to the robot controller through I / O, and the internal program of the robot controller starts to execute. As Figure 9 shown, when the ultrasonic milling edge process is applied to the carbon fiber composite parts after laser processing, the milling cutter rotates at a high speed along the feed direction. At the same time, the vibration signal generated by the ultrasonic system is transmitted to the milling cutter, causing the milling cutter to generate high-frequency axial vibration. As Figure 10 shown, this results in the periodic separation of the milling cutter from the carbon fiber composite being processed during the milling edge process. The carbon fiber composite to be removed is continuously removed after being subjected to high-frequency impacts by the milling cutter, thus completing the ultrasonic milling edge processing of the carbon fiber composite parts after laser cutting. After the milling edge is completed, the robot controller sends a signal of the action being completed to the robot through I / O, and the end effector returns to the program-set origin, and the program ends after reaching the position.

[0060] Step 3.3: Use the measurement system module to measure the surface roughness of the processed area of the carbon fiber composite parts after milling. For each group of carbon fiber composite parts after the milling edge experiment, take 3 areas as the measurement positions of the surface roughness, measure a total of 3 groups of surface roughness data, and then calculate the average value of these 3 groups of data as the surface roughness value of the carbon fiber composite parts after each group of milling edge experiments. Import the milling force data collected by the dynamometer into the MATLAB software, and obtain the magnitude of the milling force during the entire milling edge experiment through the corresponding program.

[0061] Step 3.4: Study the influence of the softening of the thermal damage area by laser cutting on the ultrasonic milling edge cutting force and milling edge stability; During the laser cutting process, the high-energy laser beam will generate large thermal stress on the thermal influence area of the carbon fiber composite, resulting in a significant phenomenon of burning and softening of the carbon fiber composite. Different laser processing parameters cause different degrees of thermal damage, and different degrees of thermal damage result in different degrees of burning and softening of the carbon fiber composite, leading to different degrees of reduction in the milling force during subsequent ultrasonic milling experiments and different gain effects of the milling edge stability. According to the experimental results, it is found that in order to minimize the milling force during milling, a larger laser power and a smaller laser cutting speed should be selected.

[0062] Step 3.5: Study the influence of laser trimming processing parameters on the quality of robotic ultrasonic milling of edges, and obtain the matching characteristics of robotic laser trimming and robotic ultrasonic milling processes, so as to determine appropriate processing parameters: By analyzing the quality of robotic ultrasonic milling of edges, it is found that the milling quality of carbon fiber composite parts after trimming with different laser processing parameters is different in the ultrasonic milling experiment. According to the experimental results, it can be found that the influence of different laser processing parameters on the milling quality has a certain regularity. Using MINITAB software to analyze the experimental results, the matching characteristics of robotic laser trimming and robotic ultrasonic milling processes can be obtained. Finally, according to the matching characteristics, the processing parameters corresponding to the best milling quality are determined.

[0063] Step 4: Conduct dual-robot collaborative laser ultrasonic milling of edges: First, formulate a dual-robot collaborative laser ultrasonic milling of edges plan. Secondly, to avoid interference and collision during dual-robot collaborative processing, conduct a simulation of the dual-robot collaborative laser ultrasonic milling of edges plan. Then carry out the dual-robot collaborative laser ultrasonic milling of edges processing. Finally, analyze the results of the dual-robot collaborative laser ultrasonic milling of edges. Compared with the milling of edges by ordinary robots, the milling force of the dual-robot collaborative laser ultrasonic milling of edges is reduced by 70 - 80%, the milling quality of edges is improved by 40%, and the processing efficiency of the robot is increased by more than 150%.

[0064] Step 4.1: Determine the processing parameters of the dual-robot collaborative laser ultrasonic milling of edges plan: Select the processing parameters obtained in Steps 2 and 3 with the best processing quality as the processing parameters of the collaborative laser ultrasonic milling of edges plan, and carry out the dual-robot laser ultrasonic collaborative processing of carbon fiber composite materials.

[0065] Step 4.2: Conduct a simulation of the dual-robot collaborative laser ultrasonic milling of edges plan: On the TECNOMATIX simulation software, simulate the paths of the processing ends of the two robots by adding motion commands, and detect interference and collision situations. According to the results of kinematic calculations, the motion states of the robots are displayed in real time. Users can intuitively understand the rationality of the processing path planning and adjust the processing path points according to the corresponding prompts. Thus, ensure that each module can achieve the motion space required for system processing and avoid interference and collision during robot collaborative processing.

[0066] Step 4.3: Conduct dual-robot collaborative laser ultrasonic milling edge machining. After clamping the workpiece, adjust the postures of the two robots, then set the corresponding machining parameters. At the same time, turn on the robot laser cutting edge system module and the robot ultrasonic machining system module. The robot moves the end effector to the position to be machined. The robot gives a signal indicating arrival at the position to the robot controller through I / O, and the internal program of the robot controller starts to execute. Start the dual-robot collaborative laser ultrasonic milling edge machining of the carbon fiber composite parts. After waiting for the final machining to be completed, the robot controller sends a signal indicating completion of the action to the two robots respectively through I / O. The end effector returns to the origin set by the program, and the program ends after arriving.

[0067] Analysis of the results of dual-robot collaborative laser ultrasonic milling edge: After laser cutting of carbon fiber composites, the softening phenomenon in the thermally damaged area leads to a significant reduction in the milling force during ultrasonic milling edge process and a substantial increase in milling stability. Compared with ordinary robot milling edge, the milling force of dual-robot collaborative laser ultrasonic milling edge is reduced by 70%-80%. Measure the surface roughness after machining. The surface three-dimensional roughness of the carbon fiber composite parts after dual-robot collaborative laser ultrasonic milling edge is within 1.5um. Compared with ordinary machining methods, the machining quality of dual-robot collaborative laser ultrasonic milling edge is improved by more than 40%. When machining the same batch of carbon fiber composite parts, the machining time spent is shortened by more than half, and the milling edge efficiency of the robot is increased by more than 150%.

[0068] Example 1

[0069] In this example, carbon fiber reinforced composite (CFRP) is taken as the object of milling edge research. The matrix material is T300 epoxy resin, and the workpiece size is 332mm×182mm×2mm. Use the robot laser cutting edge system (laser powers are 1500W / 2000W / 3000W respectively) to conduct robot laser cutting edge of carbon fiber composite parts. Use a digital microscope to measure the maximum width of the heat affected zone at the edge of the carbon fiber composite parts after laser cutting edge, and record the data. Then conduct robot ultrasonic milling edge machining on the carbon fiber composite parts after laser cutting edge. Before milling edge, drill holes in the carbon fiber composite workpiece, and then clamp and position the machining material firmly. The maximum thermal damage width at the edge of the carbon fiber composite parts after laser cutting edge is within 1.5mm, so set the milling edge width to 1.5mm. At the same time, set the milling edge length to 30mm, the feed speed to 2m / min, and the spindle speed to 4000r / min to conduct robot ultrasonic milling edge of carbon fiber reinforced composite parts. When conducting robot ultrasonic machining, set the ultrasonic frequency to 20KHz and the ultrasonic current to 150mA. Finally, measure the two-dimensional and three-dimensional surface roughness of the surface of the carbon fiber composite parts after robot laser ultrasonic milling edge. The measurement results are shown in Table 1 and Table 2.

[0070] Table 4.1 Three-dimensional roughness measurement results

[0071]

[0072] Table 4.2 Two-dimensional roughness measurement results

[0073]

[0074] The following conclusions are mainly obtained: The three-dimensional and two-dimensional roughness values of the surface after robot laser trimming and then robot ultrasonic milling are respectively smaller than those of the surface obtained by directly performing robot ultrasonic milling. Compared with single robot ultrasonic milling, the three-dimensional surface roughness is reduced by up to 20.6%, and the two-dimensional surface roughness is reduced by up to 26.6%. Under the same processing parameters, the surface roughness value of the collaborative laser-ultrasonic milling of double robots is the smallest, the surface quality is improved by more than 40%, and the processing efficiency is improved by more than 150%. Therefore, combining laser trimming and ultrasonic milling is an effective way to improve the processing quality and efficiency of robot-milled carbon fiber composite parts.

[0075] The present invention combines the advantages of two processing technologies and cleverly avoids their disadvantages, and proposes to combine robot laser trimming and robot ultrasonic milling as a new means to solve the problems of chatter and deformation in robot milling, and adopts a collaborative trimming mode of double robots to achieve high-precision and high-efficiency processing of carbon fiber composite materials.

[0076] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A dual-robot collaborative laser ultrasonic edge milling method for carbon fiber composite materials, characterized in that It includes the following steps: Step 1. Construction of a dual-robot laser ultrasonic milling-edge system: The dual-robot laser ultrasonic milling-edge system includes a robot laser cutting-edge system module, a robot ultrasonic machining system module, a measurement system module, and an interference and collision detection module; Among them, the construction of the robot laser cutting-edge system module includes: The robot laser cutting-edge system consists of hardware and software. The hardware part includes a robot system, a laser system, a laser cutting head, and a robot controller. The software part includes an offline programming system and a communication transmission system. The robot system uses a robotic arm as a motion carrier and can drive the laser cutting head to process the workpiece. Users can manually teach through a teach pendant or generate a processing trajectory matching the product through offline software. The robot controller controls the movement of the robotic arm; The construction of the robot ultrasonic machining system module includes: The ultrasonic machining system consists of an ultrasonic vibration system and a robot end effector. The ultrasonic vibration system consists of an ultrasonic generator, a power transmission module, and an ultrasonic vibration system; The measurement system module includes a digital microscope and a dynamometer; Step 2. Conduct experimental research on robot laser cutting-edge: Study the influence of different processing parameters on the width and softening degree of the thermal damage area. On the one hand, select the tool diameter accordingly. On the other hand, establish a mapping model between the processing parameters and the width of the damage area at different thicknesses. Finally, obtain the appropriate feed speed and laser power; The specific content of Step 2 includes: Step 2.

1. Selection of processing parameters for robot laser cutting-edge experimental research: Select processing parameters within the range of a carbon fiber composite part thickness of 0.5 mm - 5 mm, a laser power of 500 - 20 kW, and a cutting-edge speed of 1.0 - 10.0 m / min. Use the single-factor experimental method to conduct carbon fiber composite cutting-edge experiments under different processing parameters; Step 2.

2. Use the robot laser cutting-edge system module to conduct robot laser cutting-edge experiments; Step 2.

3. Use the measurement system module to measure the maximum thermal damage width of the edge of the carbon fiber composite part after laser cutting-edge: Observe the microscopic morphology of the cut surface using a digital microscope. Select the distance from the edge of the cut to the maximum matrix damage to represent the maximum width value of the heat-affected zone, denoted as HAZ. Measure the maximum width of the heat-affected zone of the carbon fiber composite after the laser cutting-edge experiment and record the data; Step 2.

4. Establish a mapping model between the processing parameters and the width of the damage area at different thicknesses: Therefore, use MINITAB software to analyze the experimental results after robot laser cutting-edge, obtain a mapping model between the processing parameters and the width of the damage area at different thicknesses, and obtain the laser power and feed speed corresponding to the best processing effect of the carbon fiber composite part at different thicknesses according to the established mapping model; Step 3. Experimental research on robot ultrasonic milling-edge: Study the influence of the softening of the thermal damage area after laser cutting-edge on the cutting force and milling-edge stability of ultrasonic milling-edge, study the influence of laser cutting-edge processing parameters on the quality of robot ultrasonic milling-edge, obtain the matching characteristics of the robot laser cutting-edge and robot ultrasonic milling-edge processes, and thus determine the appropriate processing parameters; The specific content of Step 3 includes: Step 3.1: Setting the processing parameters for the robot ultrasonic milling-edge experiment: Select the processing parameter range of a milling-edge length of 30 - 50 mm, a feed rate of 1.0 - 3.0 m / min, and a spindle speed of 3000 - 5000 r / min. Use a PCD milling cutter with a diameter larger than the maximum thermal damage width to conduct the robot ultrasonic milling-edge experiment on the carbon fiber composite parts after laser cutting; Step 3.2: Using the robot ultrasonic processing system module to conduct the robot ultrasonic milling-edge experiment on the carbon fiber composite parts after laser cutting, and simultaneously using a dynamometer to collect the real-time signal of the cutting force: The robot moves the end effector to the position to be processed. The robot gives a signal indicating arrival to the robot controller through I / O. The internal program of the robot controller starts to execute. When the ultrasonic milling-edge processes the carbon fiber composite parts after laser processing, the milling cutter rotates at high speed along the feed direction. At the same time, the vibration signal generated by the ultrasonic system is transmitted to the milling cutter, causing the milling cutter to generate high-frequency axial vibration, resulting in the periodic separation of the milling cutter from the carbon fiber composite parts being processed during the milling-edge process. The carbon fiber composite material to be removed is continuously removed after being subjected to high-frequency impacts by the milling cutter, thus completing the ultrasonic milling-edge processing of the carbon fiber composite parts after laser cutting. After the milling-edge is completed, the robot controller gives an action completion signal to the robot through I / O, and the end effector returns to the program-set origin, and the program ends after arrival; Step 3.3: Using the measurement system module to measure the surface roughness of the processed area of the carbon fiber composite parts after milling-edge. For each group of carbon fiber composite parts after milling-edge experiments, take 3 areas as the measurement positions for the surface roughness, measure a total of 3 groups of surface roughness data, and then calculate the average value of these 3 groups of data as the surface roughness value of the carbon fiber composite parts after each milling-edge experiment. Import the milling force data collected by the dynamometer into the MATLAB software to obtain the magnitude of the milling force during the entire milling-edge experiment; Step 3.4: Studying the influence of the softening of the laser cutting thermal damage area on the ultrasonic milling-edge cutting force and milling-edge stability; According to the experimental results, it is found that in order to minimize the milling force during milling-edge, a larger laser power and a smaller laser cutting speed are selected; Step 3.5: Studying the influence of the laser cutting processing parameters on the quality of the robot ultrasonic milling-edge, obtaining the matching characteristics of the robot laser cutting and robot ultrasonic milling-edge processes, and thus determining the appropriate processing parameters: By analyzing the quality of the robot ultrasonic milling-edge, it is found that the milling-edge quality of the carbon fiber composite materials after cutting with different laser processing parameters is different when conducting ultrasonic milling-edge experiments. According to the experimental results, it is found that the influence of different laser processing parameters on the milling-edge quality has a certain regularity, and the MINITAB software is used to analyze the experimental results to obtain the matching characteristics of the robot laser cutting and robot ultrasonic milling-edge processes. Finally, according to the matching characteristics, the processing parameters corresponding to the best milling-edge quality are determined; Step 4: Conduct dual-robot collaborative laser ultrasonic edge milling: First, formulate the processing parameters for the dual-robot collaborative laser ultrasonic edge milling scheme. Secondly, to avoid interference and collision during dual-robot collaborative processing, conduct simulation and emulation of the dual-robot collaborative laser ultrasonic edge milling scheme. Finally, carry out dual-robot collaborative laser ultrasonic edge milling processing; The specific steps of Step 4 include: Step 4.1: Formulate the processing parameters for the dual-robot collaborative laser ultrasonic edge milling scheme: Select the processing parameters obtained in Steps 2 and 3 with the best processing quality as the processing parameters for the collaborative laser ultrasonic edge milling scheme, and carry out dual-robot laser ultrasonic collaborative processing of carbon fiber composite materials; Step 4.2: Conduct simulation and emulation of the dual-robot collaborative laser ultrasonic edge milling scheme; Step 4.3: Carry out dual-robot collaborative laser ultrasonic edge milling processing: After clamping the workpiece, adjust the postures of the two robots, then set the corresponding processing parameters, and at the same time turn on the robot laser cutting system module and the robot ultrasonic processing system module. The robot moves the end effector to the position to be processed. The robot gives a signal of reaching the position to the robot controller through I / O. The internal program of the robot controller starts to execute, and starts to carry out dual-robot collaborative laser ultrasonic edge milling processing on the carbon fiber composite material part. After waiting for the final processing to be completed, the robot controller sends a signal of completing the action to the two robots respectively through I / O. The end effector returns to the origin set by the program, and the program ends after reaching the position.

2. The double-robot collaborative laser ultrasonic edge milling method for carbon fiber composite materials according to claim 1, wherein The said Step 1 further includes: The laser system includes a fiber laser, a follower, and a proportional valve. The fiber laser can generate lasers of various wavelength bands as the light source for cutting. The laser cutting focuses the laser. The follower can adjust the distance between the laser cutting head and the workpiece surface in real time and provide auxiliary gas for cutting according to different metal materials. The proportional valve is used to adjust the gas flow. The robot controller can save and modify the motion trajectory and cutting process, display the position, posture, and cutting progress of the robot in real time, and also has the function of a process database; The communication and transmission system is used to receive the robot start and emergency stop signals given by the robot controller to the robot, and at the same time receive the digital quantity signals of the laser switch, follower head switch, and solenoid valve switch given by the controller, as well as the analog quantity signals of the laser power, frequency, duty cycle, and air pressure. The offline programming system is used to realize virtual robot control, cycle time analysis, and the generation of robot programs; When building the robot ultrasonic machining system module, first, the ultrasonic signal generation module can convert the 220V voltage provided by the ultrasonic power supply into an electrical signal. Then, through the transducer, the electrical signal is converted into a vibration signal with the same frequency. After that, through the amplification of the horn, the amplitude of the vibration signal is increased, and the amplified amplitude signal is transmitted to the milling cutter, so that the milling cutter generates axial vibration with a certain frequency. The robot spindle fixes the ultrasonic vibration system on the spindle by sucking the tool holder. The non-contact power transmission port is fixed on the spindle using a bracket, keeping a certain distance from the ultrasonic transducer to facilitate the transmission of electrical signals between the magnetic coils. The gland is used to press the transducer tightly to fix the ultrasonic transducer and the horn together. The ultrasonic transducer is used to convert the electrical signal into a vibration signal, converting electrical energy into mechanical energy. The horn is used to amplify the amplitude of the ultrasonic vibration and change the vibration direction, and transmit the amplified vibration signal to the tool to make it generate high-frequency vibration. After the robot ultrasonic machining system is assembled, the power of the end effector device is turned on, and then its performance is tested. The ultrasonic transducer is separately connected to the ultrasonic power supply for a matching test, and a multimeter is used to observe the change of the resonant matching frequency. The result shows that the working frequency is within the working frequency range of the power supply. When the metal sheet contacts the end face of the transducer, a sound of metal vibration will be generated, indicating that the working performance of the ultrasonic transducer is normal; The digital microscope is used to measure the maximum thermal damage width of the edge of the carbon fiber composite part after laser cutting and the surface quality of the carbon fiber composite part after machining. The dynamometer is used to detect the milling force during the experiment; Interference and collision detection module: On the TECNOMATIX simulation software, the path of the machining end of the dual robots is simulated by adding motion commands. According to the results of kinematic calculations, the motion state of the robots is displayed in real time. Users can intuitively understand the rationality of the machining path planning and adjust the machining path points according to the corresponding prompts, so as to avoid interference and collision during the collaborative machining of the dual robots.

3. The dual-robot collaborative laser ultrasonic milling method for carbon fiber composites according to claim 2, characterized in that Step 2.2 specifically includes: First, on the robot controller, debug the ROBOGUIDE programming software for parameter setting and laser trimming programming. After the programming is completed and checked and confirmed, run the laser trimming system without turning on the laser. If an error occurs, re-debug the ROBOGUIDE programming software. If no error occurs, turn on the power of the end effector device, and officially run the robot laser trimming system module. The robot moves the end effector to the position to be processed. The robot gives a signal indicating arrival at the position to the robot controller through I / O. The internal program of the robot controller starts to execute. The laser beam moves continuously relative to the carbon fiber composite part along the processing path, so that more and more materials are removed by heat, thus forming a cut. At the same time, the residues at the cut are also removed by the high-pressure auxiliary gas, thereby completing the laser trimming of the carbon fiber composite part. After the trimming action is completed, the robot controller sends a signal indicating the completion of the action to the robot through I / O, and judges whether all trimming tasks have been completed. If all tasks have not been completed, the end effector repeats the laser trimming process; if all tasks have been completed, the end effector returns to the program setting point, and the program ends after arriving.

4. The double-robot collaborative laser ultrasonic milling edge method for carbon fiber composite materials according to claim 3, wherein The specific steps of step 3 are as follows: Step 3.4 specifically includes: During the laser trimming process, the high-energy laser beam will generate relatively large thermal stress on the heat-affected area of the carbon fiber composite, resulting in a significant phenomenon of burning and softening of the carbon fiber composite. Different laser processing parameters cause different degrees of thermal damage, and different degrees of thermal damage result in different degrees of burning and softening of the carbon fiber composite, leading to different degrees of reduction in the milling force during the subsequent ultrasonic milling experiment, and different gain effects on the milling edge stability.

5. The dual-robot collaborative laser ultrasonic milling method for carbon fiber composites according to claim 4, characterized in that Step 4.2 specifically includes: On the TECNOMATIX simulation software, simulate the paths of the processing ends of the dual robots by adding motion commands, detect interference and collision situations, and display the robot motion state in real time according to the kinematic calculation results. The user can intuitively understand the rationality of the processing path planning, and adjust the processing path points according to the corresponding prompts, so as to ensure that each module can realize the motion space required for system processing and avoid interference and collision during the collaborative processing of the robots.

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