Method for regulating and controlling surface energy of machining in-situ cutter based on laser

Abstract

The invention discloses a laser-based processing in-situ tool surface energy regulation and control method, which comprises the following steps of: calculating the laser frequency when the tool surface energy is compensated in a processing process by simulating and calculating the unit surface energy of a tool, so that a laser transmitter transmits laser with the laser frequency to carry out auxiliary processing; judging whether the total surface energy of the contact position of the cutter surface and the polytetrafluoroethylene workpiece is close or not, if so, finishing the regulation and control of the surface energy of a cutter machining area, mounting the cutter on a machine tool to machine a next workpiece, and otherwise, cleaning the cutter; and the laser frequency is corrected by detecting the total surface energy of the contact position of the tool surface and the polytetrafluoroethylene workpiece after cutting machining, so that the laser transmitter performs auxiliary machining at the corrected laser frequency, and whether the total surface energy of the contact position of the tool surface and the polytetrafluoroethylene workpiece is close or not is judged again. The surface energy of the cutter and the surface energy of a polytetrafluoroethylene workpiece tend to be the same during machining, and the adsorption phenomenon is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of ultra-precision processing of polytetrafluoroethylene materials, and in particular relates to a method for regulating and controlling surface energy of an in-situ tool during processing based on laser. Background Art

[0002] As a polymer material with excellent chemical stability, high temperature resistance, corrosion resistance and low friction coefficient, polytetrafluoroethylene has a wide range of applications. However, the surface energy of the tool used in the cutting of polytetrafluoroethylene workpieces is quite different from that of the tetrafluoroethylene workpiece. The excessive surface energy difference between the tool and the tetrafluoroethylene workpiece will produce adsorption between the material molecules, causing the tool surface to easily adsorb chips, making the processed tetrafluoroethylene workpiece have inevitable scratches and dents, increasing the roughness of the polytetrafluoroethylene surface, affecting the surface quality and processing accuracy of the workpiece, and then increasing the friction coefficient, affecting the sliding performance, and easily accumulating dirt and chemicals in actual use, affecting the corrosion resistance of the material. Therefore, it is necessary to design a method that can make the surface energy of the tool and the tetrafluoroethylene workpiece close, thereby reducing the surface energy difference between the tool and the tetrafluoroethylene workpiece, and reducing the phenomenon of chip adsorption on the tool surface during processing. Summary of the invention

[0003] The purpose of the present invention is to overcome the shortcomings of the prior art and to provide a laser-based in-situ tool surface energy regulation method.

[0004] To achieve the above object, the present invention adopts the following technical solutions:

[0005] The present invention provides a laser-based in-situ tool surface energy control method, which is as follows:

[0006] S1. Perform simulation and calculation to obtain the unit surface energy E of the tool.

[0007] S2, calculating the laser frequency f0 when compensating the surface energy of the tool during the machining process, and then performing the cutting process, and during the machining process, the laser transmitter emits a laser with a laser frequency of f0 to irradiate the position where the tool contacts the polytetrafluoroethylene workpiece to assist the cutting process, and removes the tool after the cutting process is completed; wherein, the surface energy of the tool is lower than the surface energy of the polytetrafluoroethylene workpiece, and the laser frequency f0 when compensating the surface energy of the tool is

[0008]

[0009] In the formula, E PTFE is the surface energy of the PTFE workpiece; S is the contact area between the tool and the PTFE workpiece during machining, and S = d × l, d is the width of the chip, l is the blade length of the tool during machining; E Cis the unit conversion factor from millijoules (mj) to electronvolts (eV), and 1mj = 6.2415 × 10 15 eV;P J is the maximum single pulse energy of the laser transmitter.

[0010] S3, detecting the proportion of fluorine element in a preset area at the position on the surface of the tool that contacts the polytetrafluoroethylene workpiece; if the proportion of fluorine element is lower than the preset value, the surface energy of the tool processing area is regulated, the tool is installed on the machine tool, and then the next polytetrafluoroethylene workpiece is cut; otherwise, after cleaning the chips on the tool, steps S4 and S5 are executed.

[0011] S4. Calculate the surface energy γsg of the contact position between the tool surface and the polytetrafluoroethylene workpiece after the last cutting process, and then calculate the total surface energy of the contact position between the tool surface and the polytetrafluoroethylene workpiece after the last cutting process.

[0012] E T =ysg×S.

[0013] S5. Install the tool on the machine tool. According to the calculated total surface energy E at the contact position between the tool and the polytetrafluoroethylene workpiece after processing. T Correct the laser frequency of the laser transmitter during the last cutting process, then proceed to the cutting process of the next polytetrafluoroethylene workpiece, and make the laser transmitter emit laser-assisted cutting process at the corrected laser frequency, remove the tool after completing the cutting process of the next polytetrafluoroethylene workpiece, and return to step S3; wherein the corrected laser frequency f1 is

[0014]

[0015] Preferably, the process of S1 is: writing an in file, establishing a tool surface model, importing the in file and the tool surface model into the lammps software, running a simulation to obtain the initial total energy E0 of the tool surface model and the total energy E1 after the tool surface model is divided into two parts in half, and then calculating the surface energy E of the tool; the surface energy calculation formula of the tool is:

[0016]

[0017] Where A is the area of ​​the separated cross section after the tool surface model is split in half during the simulation process.

[0018] More preferably, when writing the in file, the basic parameters, time step, neighbor list neighbor and neighbor list update frequency are set in sequence, the lattice orientation and potential function of the tool surface model are selected, the parameters are set when the energy of the tool surface model is minimized for the first time, the direction in which the tool surface model is split in half and the unit of the expansion of the simulation space range box size in the split direction are set, and the parameters are set when the energy of the tool surface model is minimized for the second time. During the simulation process, the initial total energy E0 of the tool surface model is output after the energy of the tool surface model is minimized for the first time, and the total energy E1 of the tool surface model after being divided into two parts is output after the energy of the tool surface model is minimized for the second time.

[0019] More preferably, the basic parameters include simulation area boundary, simulation units units and atomic type atom_style, the lattice orientation of the tool surface model is selected according to the crystal planes exposed on the tool surface, the parameters for minimizing the energy of the tool surface model include energy tolerance, force tolerance and maximum number of iterations, the direction in which the tool surface model is split in half is any one of the x, y and z directions, and the unit of expansion of the simulation space range box size in the separation direction is greater than 100 units.

[0020] Preferably, when detecting the proportion of fluorine elements in a preset area at a position on the tool surface that contacts the polytetrafluoroethylene workpiece, the UltumMax module attached to the scanning electron microscope is used to observe the position on the tool surface that contacts the polytetrafluoroethylene workpiece after the cutting process is completed, and the number of fluorine elements is counted, and then the proportion of fluorine elements in the preset area at a position on the tool surface that contacts the polytetrafluoroethylene workpiece is calculated.

[0021] Preferably, the EDS module counting rate of the scanning electron microscope is not less than 130,000 cps.

[0022] Preferably, the process of calculating the unit surface energy γsg at the position where the tool surface contacts the polytetrafluoroethylene workpiece after the last cutting process is as follows: using a contact angle measuring instrument to detect the position where the tool surface contacts the polytetrafluoroethylene workpiece, and obtaining the contact angle θ between the liquid used in the detection and the position where the tool surface contacts the polytetrafluoroethylene workpiece, and the interfacial tension γsl between the liquid used in the detection and the position where the tool surface contacts the polytetrafluoroethylene workpiece, then the surface energy γsg at the position where the tool surface contacts the polytetrafluoroethylene workpiece after the last cutting process is completed is

[0023] γsg=γlg×cosθ+γsl

[0024] Where γlg is the surface tension of the liquid used in the test.

[0025] The present invention has the following beneficial effects:

[0026] The present invention adopts a method of laser regulating the surface energy of the tool to compensate the surface energy of the tool, so that the surface energy of the tool is close to the surface energy of the polytetrafluoroethylene workpiece, reducing the surface energy difference between the tool and the polytetrafluoroethylene workpiece during cutting, reducing the adsorption phenomenon caused by the excessive difference in surface energy between the tool and the polytetrafluoroethylene workpiece, and improving the processing accuracy and the surface quality of the polytetrafluoroethylene workpiece. Specifically, the present invention calculates the laser frequency f0 when compensating the tool surface energy during the machining process by using the tool surface energy obtained by simulation calculation, so that the laser transmitter emits a laser with a laser frequency of f0 for auxiliary cutting processing. After the cutting processing is completed, it is determined whether the total surface energy of the tool surface and the contact position on the polytetrafluoroethylene workpiece are close. If they are close, it is considered that the regulation of the surface energy of the tool machining area is completed, and the tool is installed on the machine tool to continue to process the next polytetrafluoroethylene workpiece. Otherwise, the tool is cleaned, and the laser frequency is corrected by detecting the total surface energy of the contact position on the tool surface with the polytetrafluoroethylene workpiece after the cutting processing, so that the laser transmitter performs auxiliary cutting processing with the corrected laser frequency, and returns to the step of determining whether the total surface energy of the tool surface and the contact position on the polytetrafluoroethylene workpiece are close. Feedback adjustment is performed until the total surface energy of the tool surface and the contact position on the polytetrafluoroethylene workpiece are close, thereby realizing the regulation of the tool surface energy during machining. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a flow chart of the present invention. DETAILED DESCRIPTION

[0028] The present invention is further described below in conjunction with the accompanying drawings.

[0029] like Figure 1 As shown, the present invention provides a laser-based in-situ tool surface energy control method, which is as follows:

[0030] S1. Write the in file, build the tool surface model, import the in file and the tool surface model into the lammps software, run the simulation to get the initial total energy E0 of the tool surface model and the total energy E1 after the tool surface model is divided into two parts, and then calculate the surface energy E of the tool; the surface energy calculation formula of the tool is:

[0031]

[0032] Where A is the area of ​​the section after the tool surface model is split in half during the simulation, and the unit is It can be obtained by running the simulation process.

[0033] Among them, when writing the in file, the basic parameters, time step, neighbor list neighbor and neighbor list update frequency are set in turn, the lattice orientation and potential function of the tool surface model are selected, the parameters are set when the tool surface model is minimized for the first time, the direction of splitting the tool surface model in half and the unit of expansion of the simulation space range box size in the splitting direction are set, and the parameters are set when the tool surface model is minimized for the second time. During the simulation process, the initial total energy E0 of the tool surface model is output after the energy of the tool surface model is minimized for the first time, and the total energy E1 of the tool surface model after being divided into two parts is output after the energy of the tool surface model is minimized for the second time; the basic parameters include the simulation area boundary, simulation unit units and atomic type atom_style, the lattice orientation of the tool surface model is selected according to the crystal plane exposed on the tool surface, the parameters for minimizing the energy of the tool surface model include energy tolerance, force tolerance and maximum iteration steps, the direction of splitting the tool surface model in half is any one of x, y and z directions, and the unit of expansion of the simulation space range box size in the splitting direction is greater than 100 units.

[0034] In this embodiment, the simulation area boundary is defined as p, p, p, that is, the three directions of xyz are all set as periodic boundaries, the simulation unit units is set to metal or real, the atom type atom_style is set to atomic or full, the time step timestep is 0.1, the neighbor list neighbor is 0.6, and the neighbor list update frequency is 5; the lattice orientation of the tool surface model is selected from the 100 face, 110 face or 111 face of the tool surface model; the potential function is selected as eam potential or reaxff potential, and the reaxff potential is preferably used under the condition that the potential function allows. The use of the reaxff potential can obtain a higher-precision surface energy calculation result; the energy tolerance in the energy minimization parameters of the tool surface model is set to 1.0e -30 , the force tolerance is 1.0e -22 , the maximum number of iterations is set to 10000; the energy tolerance in the energy minimization parameters of the tool surface model is set to 1.0e -35 , the force tolerance is 1.0e -26 , the maximum number of iterations is set to 13000 steps.

[0035] S2. Calculate the laser frequency f0 required to compensate for the surface energy of the tool during the machining process, then perform cutting, and during the machining process, make the laser transmitter emit a laser with a laser frequency of f0 to irradiate the position where the tool contacts the polytetrafluoroethylene workpiece to assist the cutting process, and remove the tool after the cutting process is completed; wherein, the surface energy of the tool is lower than the surface energy of the polytetrafluoroethylene workpiece, and the part of the polytetrafluoroethylene workpiece irradiated by the laser during the machining process will be cut off by the tool, and then it is considered that during the machining process, the laser only acts on the position on the surface of the tool that contacts the polytetrafluoroethylene workpiece, then the laser frequency f0 required to compensate for the surface energy of the tool is

[0036]

[0037] In the formula, E PTFE is the surface energy of the polytetrafluoroethylene workpiece, which is calculated from the existing case that the surface energy of the polytetrafluoroethylene surface is 26 eV at 32.9 square angstroms. Specifically, it can be calculated according to step S1, except that the tool in step S1 is replaced with a polytetrafluoroethylene workpiece, and the area of ​​the separated cross section after the polytetrafluoroethylene workpiece surface model is split in half is 32.9 square angstroms, and the unit of the expansion of the simulation space range box size in the separation direction is set to be greater than 150 units, and the selection of the lattice orientation of the tool surface model is replaced with the polytetrafluoroethylene material parameter setting. The polytetrafluoroethylene material parameter setting is specifically as follows: the degree of polymerization of the polytetrafluoroethylene material is 20, and the filling density in the simulation area boundary is 2.2 g / cm 3 The polytetrafluoroethylene chains of the polytetrafluoroethylene workpiece surface model shall not be less than 1000. After the polytetrafluoroethylene workpiece surface model is established, relaxation of not less than 300 nanoseconds is performed to allow the polytetrafluoroethylene chains to fully stretch and obtain an overall reasonable structure; the surface energy E of the polytetrafluoroethylene workpiece calculated PTFE =7.90075×10 19 eV / m 2 ; S is the contact area between the tool and the polytetrafluoroethylene workpiece during processing, and S = d × l, d is the width of the chip, l is the blade length of the tool during processing, d and l are obtained from the pre-processing experiment, and the average chip width and the average blade length of the tool during processing obtained by the pre-processing experiment are regarded as d and l. In this embodiment, d = 2 mm and l = 4 mm are obtained by the pre-processing experiment, then E PTFE ×S=6.3206×10 14 eV;E C is the unit conversion factor from millijoules (mJ) to electronvolts (eV), and 1mJ = 6.2415 × 10 15 eV;P Jis the maximum single pulse energy of the laser transmitter. The laser transmitter used in this embodiment is the SpitLight series 7000 pulse Nd:YAG laser of InnoLas, with an emission center wavelength of 266nm, a minimum pulse width of less than 130fs, a maximum single pulse energy of 0.6mJ, and a spot diameter of 16mm. The calculation formula of the laser frequency f0 expresses the pulse energy required to compensate the surface energy difference in the contact area between the tool and the polytetrafluoroethylene workpiece during processing in electron volts eV. J The number of lasers.

[0038] S3. Use a scanning electron microscope (scanning electron microscope, such as Zeiss' GeminiSEM560 scanning electron microscope) with an EDS module (energy dispersive spectrometer) to observe the position on the tool surface that contacts the polytetrafluoroethylene workpiece after the cutting process, count the number of fluorine elements and calculate the proportion of fluorine elements within a size range of 50μm×50μm on the tool surface that contacts the polytetrafluoroethylene workpiece. If the proportion of fluorine elements within a size range of 50μm×50μm on the tool surface that contacts the polytetrafluoroethylene workpiece is not higher than 5%, it is considered that the amount of polytetrafluoroethylene adsorbed on the tool surface is relatively low. The total surface energy at the contact position between the tool surface and the polytetrafluoroethylene workpiece is close to the total surface energy at the contact position between the polytetrafluoroethylene workpiece and the tool, and the laser frequency does not need to be corrected. The surface energy of the tool processing area is regulated and adjusted, and the tool is installed on the machine tool, and then the next polytetrafluoroethylene workpiece is cut. On the contrary, it is considered that the amount of polytetrafluoroethylene adsorbed on the tool surface is large, and the total surface energy at the contact position between the tool surface and the polytetrafluoroethylene workpiece is much smaller than the total surface energy at the contact position between the polytetrafluoroethylene workpiece and the tool. After cleaning (using air blowing or non-woven fabric wiping) the chips on the tool, step S4 and step S5 are executed. Among them, the EDS module count rate of the scanning electron microscope is not less than 130000cps.

[0039] S4. Use a contact angle measuring instrument to detect the position on the tool surface that contacts the polytetrafluoroethylene workpiece, and obtain the contact angle θ between the liquid used in the detection and the position on the tool surface that contacts the polytetrafluoroethylene workpiece, and the interfacial tension γsl between the liquid used in the detection and the position on the tool surface that contacts the polytetrafluoroethylene workpiece, and then calculate the surface energy γsg at the position on the tool surface that contacts the polytetrafluoroethylene workpiece after the last cutting process is completed: γsg=ylg×cosθ+ysl

[0040] Where γlg is the surface tension of the liquid used in the test. The surface tension of the liquid used in the test, γlg, can be obtained by consulting materials or conducting preliminary experiments. The experimental methods include capillary rise method, spinning drop method, hanging drop method, platinum plate method, platinum ring method and bubble pressure method. If the liquid used in the test is water, the test environment gas is air, and the test environment temperature is 20 degrees Celsius, then γlg can be taken as 72.75×10 -3 N / m, where 1×10 -3 N / m=1mJ / m 2 ;

[0041] Then calculate the total surface energy E at the contact position between the tool surface and the polytetrafluoroethylene workpiece after the last cutting process is completed. T ,for

[0042] E T =ysg×S

[0043] S5. Install the tool on the machine tool. According to the calculated total surface energy E at the contact position between the tool and the polytetrafluoroethylene workpiece after processing. T Correct the laser frequency of the laser transmitter during the last cutting process, then proceed to the cutting process of the next polytetrafluoroethylene workpiece, and make the laser transmitter emit laser-assisted cutting process at the corrected laser frequency, remove the tool after completing the cutting process of the next polytetrafluoroethylene workpiece, and return to step S3; wherein the corrected laser frequency is

[0044]

[0045] Where f1 is the corrected laser frequency, E T It is the total surface energy at the contact position between the tool surface and the polytetrafluoroethylene workpiece after the last cutting process.

Claims

1. A laser-based in-situ tool surface energy control method, characterized in that: The details are as follows: S1. Perform simulation and calculation to obtain the unit surface energy E of the tool; S2, calculating the laser frequency f0 when compensating the surface energy of the tool during the machining process, and then performing the cutting process, and during the machining process, the laser transmitter emits a laser with a laser frequency of f0 to irradiate the position where the tool contacts the polytetrafluoroethylene workpiece to assist the cutting process, and removes the tool after the cutting process is completed; wherein, the surface energy of the tool is lower than the surface energy of the polytetrafluoroethylene workpiece, and the laser frequency f0 when compensating the surface energy of the tool is In the formula, E PTFE is the surface energy of the PTFE workpiece; S is the contact area between the tool and the PTFE workpiece during machining, and S = d × l, d is the width of the chip, l is the blade length of the tool during machining; E C is the unit conversion factor from millijoules (mJ) to electronvolts (eV), and 1mJ = 6.2415 × 10 15 eV;P J is the maximum single pulse energy of the laser transmitter; S3, detecting the proportion of fluorine elements in a preset area at a position on the surface of the tool that contacts the polytetrafluoroethylene workpiece; if the proportion of fluorine elements is lower than a preset value, the surface energy of the tool processing area is regulated, the tool is installed on the machine tool, and then the next polytetrafluoroethylene workpiece is cut; otherwise, after cleaning the chips on the tool, steps S4 and S5 are executed; S4. Calculate the surface energy γsg of the contact position between the tool surface and the polytetrafluoroethylene workpiece after the last cutting process, and then calculate the total surface energy of the contact position between the tool surface and the polytetrafluoroethylene workpiece after the last cutting process. AND T =ysg×S; S5. Install the tool on the machine tool. According to the calculated total surface energy E at the contact position between the tool and the polytetrafluoroethylene workpiece after processing. T Correct the laser frequency of the laser transmitter during the last cutting process, then proceed to the cutting process of the next polytetrafluoroethylene workpiece, and make the laser transmitter emit laser-assisted cutting process at the corrected laser frequency, remove the tool after completing the cutting process of the next polytetrafluoroethylene workpiece, and return to step S3; wherein the corrected laser frequency f1 is 2. The laser-based in-situ tool surface energy control method according to claim 1, characterized in that: The process of S1 is: write the in file, establish the tool surface model, import the in file and the tool surface model into the lammps software, run the simulation to obtain the initial total energy E0 of the tool surface model and the total energy E1 after the tool surface model is divided into two parts, and then calculate the surface energy E of the tool; the surface energy calculation formula of the tool is Where A is the area of ​​the separated cross section after the tool surface model is split in half during the simulation process.

3. The laser-based in-situ tool surface energy control method according to claim 2, characterized in that: When writing the in file, set the basic parameters, time step, neighbor list neighbor and neighbor list update frequency in turn, select the lattice orientation and potential function of the tool surface model, set the parameters for the first energy minimization of the tool surface model, set the direction in which the tool surface model is split in half and the unit for expanding the simulation space range box size in the separation direction, and set the parameters for the second energy minimization of the tool surface model. During the simulation process, the initial total energy E0 of the tool surface model is output after the energy of the tool surface model is minimized for the first time, and the total energy E1 of the tool surface model after being divided into two parts is output after the energy of the tool surface model is minimized for the second time.

4. The laser-based in-situ tool surface energy control method according to claim 3, characterized in that: The basic parameters include the simulation area boundary, simulation unit units and atomic type atom_style. The lattice orientation of the tool surface model is selected according to the crystal plane exposed on the tool surface. The parameters for minimizing the energy of the tool surface model include energy tolerance, force tolerance and maximum iteration steps. The direction in which the tool surface model is split in half is any one of the x, y and z directions. The unit of expansion of the simulation space range box size in the splitting direction is greater than 100 units.

5. The laser-based in-situ tool surface energy control method according to claim 1, characterized in that: When detecting the proportion of fluorine elements in a preset area at a position on the tool surface that contacts the polytetrafluoroethylene workpiece, a scanning electron microscope is used to observe the position on the tool surface that contacts the polytetrafluoroethylene workpiece after the cutting process is completed, and the number of fluorine elements is counted, and then the proportion of fluorine elements in the preset area at the position on the tool surface that contacts the polytetrafluoroethylene workpiece is calculated.

6. The laser-based in-situ tool surface energy control method according to claim 5, characterized in that: The EDS module counting rate of the scanning electron microscope is not less than 130,000 cps.

7. The laser-based in-situ tool surface energy control method according to claim 1, characterized in that: The process of calculating the unit surface energy γsg at the position where the tool surface contacts the polytetrafluoroethylene workpiece after the last cutting process is as follows: using a contact angle measuring instrument to detect the position where the tool surface contacts the polytetrafluoroethylene workpiece, and obtaining the contact angle θ between the liquid used in the detection and the position where the tool surface contacts the polytetrafluoroethylene workpiece, and the interfacial tension γsl between the liquid used in the detection and the position where the tool surface contacts the polytetrafluoroethylene workpiece, then the surface energy γsg at the position where the tool surface contacts the polytetrafluoroethylene workpiece after the last cutting process is γsg=γlg×cosθ+γsl Where γlg is the surface tension of the liquid used in the test.

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