Hole machining quality evaluation method based on drill withdrawal radial force

Abstract

The invention relates to the technical field of drill bit research and development and hole machining tests, and discloses a hole machining quality evaluation method based on drill withdrawal radial force, and the method comprises the steps: carrying out a drilling test, and drilling a hole with a preset depth in a test workpiece; measuring the generated radial force by using a radial force measuring device in the drill withdrawal process of the drilling test to obtain drill withdrawal radial force data; characteristic parameters are calculated according to the preprocessed drill withdrawal radial force data; and evaluating the quality of the hole processed by the drilling test according to the drilling retreating radial force and the characteristic parameters. According to the scheme, the drill retreating process of drilling test hole machining is creatively utilized, quality evaluation of the tool machining hole is achieved in the drill retreating process, the problems that in the existing drill bit research and development stage, the hole precision measurement efficiency is low, and the application scene is limited are solved, a new thought is provided for drill bit research and development based on the evaluation result of the drilling test machining hole quality, and the drill bit research and development efficiency is improved. The research and development period of the drill is shortened.

Description

Technical Field

[0001] The present invention relates to the technical field of drill bit research and development and hole machining tests, and specifically relates to a method for evaluating hole machining quality based on the radial force during drill withdrawal. Background Art

[0002] During the research and development of drill bits, it is necessary to know the rationality of the drill bit design structure and the machining plan. Generally, the rationality of the drill bit structure and the machining plan can be indirectly reflected by the machining accuracy of the hole. Therefore, accurately evaluating the quality of the machined hole of the drill bit during the research and development process of the drill bit is crucial for the design of the drill bit structure and the rationality of the machining plan.

[0003] The machining accuracy of the hole mainly focuses on information such as the hole diameter, hole pitch, hole shape, and hole position. In terms of the means of measuring the machining accuracy of the hole, there are existing contact measurements and non-contact measurements. Among them, contact measurements often rely on measuring tools such as micrometers and coordinate measuring machines. Such means are either easily affected by human subjectivity or have low efficiency, and there is also an impact on the machined hole itself when contacting; non-contact measurements often rely on means such as machine vision and pneumatic measurement, and are affected by the environment, and there will also be problems of unstable measurement and low efficiency.

[0004] At the same time, restricted by the machine tool space and the measurement method, most measurement methods often cannot be carried out online. When measuring, it is often necessary to stop machining; when using equipment such as coordinate measuring machines, it is even necessary to disassemble the workpiece from the machine tool, which will inevitably introduce new machining errors due to repeated clamping. Summary of the Invention

[0005] The present invention aims to provide a method for evaluating hole machining quality based on the radial force during drill withdrawal, to realize the quality evaluation of the tool's machined hole during the drill withdrawal process of the drill bit test hole machining, so as to solve the problems of low efficiency of hole accuracy measurement and limited application scenarios during the existing drilling research and development stage, and provide new ideas for the research and development of drill bits, shortening the research and development cycle of drill bits.

[0006] The basic solution provided by the present invention is: A method for evaluating hole machining quality based on the radial force during drill withdrawal, the method comprising:

[0007] Step 100, perform a drilling test and drill a hole with a preset depth in the test workpiece;

[0008] Step 200, use a radial force measuring device to measure the generated radial force during the drill withdrawal process of the drilling test to obtain radial force data during drill withdrawal;

[0009] Step 300, calculate characteristic parameters according to the preprocessed radial force data during drill withdrawal;

[0010] Step 400: Evaluate the quality of the holes processed in the drilling test based on the retraction radial force and characteristic parameters.

[0011] Glossary:

[0012] Drilling test refers to the drilling process carried out during the development of drill bits to evaluate the quality of drill bits and propose improvement ideas.

[0013] Retraction radial force refers to the force generated when part of the drill bit comes into contact with the hole wall during the retraction of the drill bit (i.e., retraction). The resultant force of these forces, projected in the radial direction, is the radial force. Specifically, the radial direction is the direction from the contact point to the center of rotation of the drill bit.

[0014] The working principle and advantages of the present invention are as follows:

[0015] Any drilling process includes the retraction process. However, this process is not fully utilized in many cases. One reason is that in existing automated machining scenarios, to ensure high-efficiency machining, additional pauses or inspection processes are usually not allowed during retraction. Another reason is that as the drill bit gradually disengages from the bottom of the hole during retraction, the contact area decreases, and the amount of effective data obtained by conventional sensors decreases. The limited data during retraction is difficult to provide sufficient information to evaluate the quality of the hole in the conventional sense. Thirdly, in specific high-demand application scenarios or the machining of special materials, it is considered that the retraction process also affects the quality of the hole. Therefore, when evaluating the quality of the hole, the performance during the retraction process also needs to be concerned. Thus, to ensure that the quality evaluation of the hole reaches a high accuracy standard, the quality evaluation of the machined hole is usually carried out after retraction.

[0016] However, with the continuous development of drilling systems and drilling technologies, the quality of machined holes is getting higher and higher. Through a large number of actual situation studies, it is found that the influence of the retraction process on the quality of machined holes is actually very small, and there is no substantial difference in the evaluation of the quality of formed holes. Therefore, this solution breaks through the conventional thinking and adopts the method of measuring the radial force during retraction to evaluate the quality of the machined hole, balancing the influence of the retraction process on the quality of the machined hole and the convenience and accuracy of the evaluation.

[0017] Compared with the measurement of the radial force during the conventional machining process, during the drill retraction process, the drill bit does not participate in cutting, so the measurement result will not be affected by the cutting force, which will bring great convenience to the analysis work. Therefore, this solution specifically proposes an effective method for measuring the radial force during the drill retraction process. During the drill retraction process, the inner wall of the machined hole may come into contact with the drill bit and generate a contact force. The drill bit undergoes elastic deformation due to the contact. Since the clamping length of the drill bit does not change, under the condition that the stiffness of the machine tool is sufficient and unchanged, the contact force and the deformation of the drill bit show a linear relationship. During the drill retraction process of the drill bit, the contact point between the drill bit and the inner wall of the hole sweeps along a helix. According to the change of the inner wall contour of the hole, the deformation of the drill bit changes accordingly, and a corresponding contact force is generated. The three show a linear relationship. It is feasible to indirectly represent the change of part of the inner diameter contour by using the radial force during the drill retraction process.

[0018] Through this solution, the drill bit structure, machining parameters, and the properties of the workpiece can directly determine the performance of the drill retraction radial force. On the premise of ensuring that the machining parameters and the properties of the workpiece remain unchanged, if the tip angle of the drill bit is asymmetric, the drilled hole will be inclined and the diameter will be enlarged. When the drill bit has problems such as an asymmetric tip angle and unequal cutting edge lengths at the same time, the phenomenon of stepped holes will also occur. These phenomena cause abnormal changes in the inner contour of the hole. The drill retraction radial force measured through this solution can reflect these abnormal changes, highlighting the outstanding advantages of the drill retraction radial force of this solution in the process of evaluating the quality of the machined hole during the drill bit R & D stage.

[0019] Compared with the prior art, the advantages of the present invention are as follows:

[0020] 1. This solution does not require disassembling the workpiece. During the drilling process, corresponding data can be efficiently obtained, and the quality accuracy of the machined hole can be obtained. Moreover, when obtaining the corresponding data, it does not affect the drilling process and does not have an impact on the machined hole itself, ensuring the accuracy of the evaluation result. It is applicable to any drilling test scenario that requires timely obtaining the accuracy of the machined hole, especially the scenario where it is not convenient to remove the workpiece to measure the hole accuracy.

[0021] 2. This solution can easily achieve automatic measurement and evaluation by combining a force measuring device and a corresponding automatic calculation program. It does not require a large amount of manual intervention, can avoid errors caused by human subjective factors, and provides a low-cost, efficient, and stable and reliable hole accuracy evaluation solution, which is applicable to drilling test scenarios where it is not convenient for manual participation.

[0022] 3. The characteristic parameters of this solution are specifically designed for the calculations related to the drilling test hole machining process. By evaluating the quality of the machined holes in the drilling test, the inclination of the machined holes is obtained from the retraction radial force and the characteristic parameters, indirectly reflecting the symmetry of the drill tip angle, and the stepped performance of the machined holes is obtained, indirectly reflecting the symmetry of the drill tip angle and the difference in the cutting edge length. Through different comparative tests, the suitable working conditions and machining materials for the drill bit are found, providing new ideas for the research and development of the drill bit and shortening the research and development cycle of the drill bit.

[0023] 4. By deeply analyzing the drilling system, the drilling process, and the contact force, it is found that on the one hand, this contact force is manifested as the force borne by the workpiece, which is transmitted to the plate - type multi - component force measuring device and measured by this device; on the other hand, it is manifested as the force borne by the drill bit, which is transmitted to the shank - type force measuring device and measured by this device. The magnitudes of the two forces are equal and the directions are opposite. Therefore, by optimizing the evaluation process of this solution, it can be adapted to a variety of radial force measuring devices, meet the installation requirements of different drilling systems, and improve the adaptability and generality. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a flowchart of a method for evaluating the quality of hole machining based on the retraction radial force provided by Embodiment 1 of the present invention;

[0025] Figure 2 It is an installation schematic diagram of the plate - type multi - component force measuring device provided by Embodiment 1 of the present invention;

[0026] Figure 3 It is a schematic diagram of the difference between the theoretical contour and the actual contour provided by Embodiment 1 of the present invention;

[0027] Figure 4 It is an installation schematic diagram of the plate - type multi - component force measuring device provided by Embodiment 2 of the present invention;

[0028] The marks in the attached drawings of the specification include: the drilling equipment workbench 1, the plate - type multi - component force measuring device 2, the test workpiece 3, the drill bit 4, the machine tool spindle 5, and the shank - type force measuring instrument 6. DETAILED DESCRIPTION OF THE INVENTION

[0029] The following is a more detailed description through specific embodiments:

[0030] It should be noted that the evaluation environment of this solution has an adaptive drilling system and a reasonable processing solution. The drilling system includes drilling equipment and its control system, and drilling tools. The drilling equipment is a machine tool, which is a vertical machining center to ensure sufficient accuracy and rigidity. The drilling tool is a drill bit, and the drill bit has reasonable structural parameters and will not have obvious diameter expansion, so that its influence can be ignored. The drill bit is installed on the spindle of the machine tool. The control system controls the normal operation of the drill bit to ensure the effective completion of hole processing, especially to keep the feed speed unchanged and the cutting fluid and air cooling turned off during the back drilling process. The existing normal hole processing environment is sufficient.

[0031] Embodiment 1

[0032] Basically as attached Figure 1 A hole machining quality assessment method based on back-drilling radial force is shown, the method comprising:

[0033] Step 100, performing a drilling test to drill a hole of a preset depth on a test workpiece;

[0034] Step 200, using a radial force measuring device to measure the radial force generated during the drill withdrawal process of the drilling test to obtain drill withdrawal radial force data;

[0035] Step 300, calculating characteristic parameters according to the preprocessed drill back radial force data;

[0036] Step 400, evaluating the quality of the hole processed by the drilling test by using the radial force of the drill withdrawal and the characteristic parameters.

[0037] Specific:

[0038] In step 100, a hole of a certain depth is drilled on the surface of the workpiece using a drilling system. The hole here refers to a theoretically cylindrical hole. In the process, the drill bit should not be broken, twisted off, or otherwise damaged. This is a conventional independent drilling process.

[0039] In step 200, the process of measuring the generated radial force and obtaining the drill back radial force data includes:

[0040] S201, during the hole processing, after the drill bit drills into position, the drill bit continues to maintain the original speed and hovers; wherein, drilling into position means that the drill bit drills downward at a preset position of the workpiece under the control of the machine tool and reaches a preset drilling position;

[0041] S202, turning on the cutting fluid, cooling the hole to room temperature and ensuring that there is no chip attached to the inner wall of the hole;

[0042] S203. Turn off the cutting fluid and turn on the radial force measuring device before retracting the drill. During the drill retraction process, retract the drill at a uniform rotational speed and feed rate. To ensure a sufficient amount of data is collected and to reduce the influence of accidental errors, the selection of the rotational speed and the drill retraction feed rate should ensure that the number of revolutions the drill has made before completely exiting satisfies the preset requirements. In this embodiment, the preset requirements are 100 - 150 revolutions; at the same time, to avoid generating a large amount of heat during the contact between the drill and the hole, the selected rotational speed is 600 - 1000 r / min; measure the radial force generated during this drill retraction process through the radial force measuring device;

[0043] S205. Continue measuring until the drill completely exits the machining hole, obtaining the drill retraction radial force data, and the number of revolutions the drill has made before completely exiting satisfies the preset requirements;

[0044] S206. Save the drill retraction radial force data and turn off the radial force measuring device.

[0045] In this embodiment, the radial force measuring device is a flat multi - component force measuring device 2, as Figure 2 shown. During installation, the lower surface of the flat multi - component force measuring device 2 contacts and is fixed to the upper surface of the drilling equipment workbench 1, and the upper surface contacts and is fixed to the lower surface of the test workpiece 3. Before installation, it should be ensured that each installation surface is clean and free of foreign objects. Use bolt connections to ensure that each installation surface is closely fitted and has sufficient residual pre - tightening force. This residual pre - tightening force ensures that friction is generated between the installation surfaces and ultimately balances the radial force. For all installation surfaces, the following relationships need to be satisfied.

[0046] aFr max ≤∑F bolt μ

[0047] bT max ≤∑F bolt μm

[0048] In the formula, Fr max is the maximum radial force, F bolt is the residual pre - tightening force provided by the bolts, μ is the friction coefficient between the installation surfaces, a is the safety factor, and a > 1; T max is the maximum torque generated by the drill on the workpiece, m is the vertical distance between the bolt axis and the action point of T max , and b is the safety factor, and b > 1.

[0049] After installation, it should be ensured that the horizontal projection contour of the workpiece does not exceed the horizontal projection contour of the flat force gauge.

[0050] Use the drilling equipment (such as a vertical machining center, the same below) in the drilling system and the flat multi - component force measuring device 2 to determine the stiffness coefficient. Before the drill approaches the test workpiece in the radial direction of the drill, lock the rotation of the drilling equipment spindle and turn on the flat multi - component force measuring device.

[0051] The flat multi-component force measuring device 2 can adopt the KISTLER 9139AA multi-component force gauge, and be equipped with a 5080A charge amplifier, a data acquisition card, and the supporting DynoWare software. Among them, when installing and using the KISTLER 9139AA multi-component force gauge on the machine tool, four multi-component force sensors are distributed inside, which can measure forces in multiple directions simultaneously and convert the force signals into electrical signals. The 5080A charge amplifier has functions such as amplifying and modulating the received electrical signals, and inputs these signals into the computer through the data acquisition card, and is presented, analyzed, and processed through the DynoWare software and other means (such as automation programs). According to the force values in the X, Y, and Z directions provided by the sensor, the radial force can be calculated by the method of vector synthesis. Assuming that the radial force is perpendicular to the spindle direction (Z-axis), the radial force can be expressed as:

[0052]

[0053] where, Fr is the radial force, F x and F y are the force components in the X-axis and Y-axis directions respectively. Specifically, it can be carried out according to the existing flat multi-component force measuring device.

[0054] To ensure the effectiveness and accuracy of the results, the flat multi-component force measuring device should ensure a sufficient sampling frequency. In this embodiment, when the spindle rotates one circle, the number of sampling times is not less than 100 times, that is, it satisfies:

[0055] f sample ≥100ω / 60

[0056] where, f sample is the sampling frequency, with the unit of Hz, and ω is the spindle speed, with the unit of r / min.

[0057] In step 300, the preprocessing includes low-pass filtering processing, which is used to remove high-frequency noise to improve the accuracy of the data.

[0058] As Figure 3 shown, there are differences between the actual contour of the hole and the theoretical contour. In the radial direction, the difference between the actual contour of the hole and the theoretical contour of the hole can be considered as a function of the angle. At the position of the contact point between the drill bit and the hole wall, the relationship between this difference and the radial force can be expressed as:

[0059]

[0060] where, x, y, and z are all functions of time t, and Fr(x, y, z) is the radial force generated when the position coordinates of the contact point are (x, y, z), When the position coordinates of the contact point are (x, y, z), it is the difference vector between the actual contour and the theoretical contour of the hole. This difference vector passes through the contact point and is perpendicular to the spindle axis. k is the stiffness coefficient, and F0 is the radial force generated when the drill bit contacts the inner wall of the hole when the hole contour is the theoretical contour and the drill bit is located at the axis of the hole.

[0061] In step 300, the characteristic parameters include the drill bit machining stability eigenvalue, the drill bit machining hole roundness eigenvalue, the drill bit machining hole direction accuracy eigenvalue, the drill bit machining hole straightness eigenvalue, and the drill bit machining hole eccentricity eigenvalue.

[0062] It should be noted that the characteristic parameters of this step are different from those calculated by the conventional scheme and cannot be used for conventional hole accuracy measurement. It is a relevant calculation for the drilling test hole machining process and provides new ideas for drill bit research and development.

[0063] Specifically:

[0064] The drill bit machining stability eigenvalue is the standard deviation of the radial force magnitude during the drill bit retraction process;

[0065]

[0066] Among them, S Fr is the drill bit machining stability eigenvalue, m is the number of samples collected during the drill bit retraction process, and i is the sample number.

[0067] Based on the magnitude and direction of the radial force during the drill bit retraction process, with the spindle preset rotation as 1 calculation unit, for example, every 1 rotation as 1 calculation unit, the resultant force of all the radial forces within this unit is obtained by force synthesis, ignoring the resultant moment. The starting point of this resultant force is placed at the midpoint of the projection line segment of the spindle axis corresponding to this unit, that is:

[0068]

[0069] Among them, is the resultant force of all the radial forces in the jth calculation unit.

[0070] The drill bit machining hole direction accuracy eigenvalue is, based on the resultant force of each calculation unit, in the force space, the end points of the resultant forces of each unit are subjected to spatial straight line fitting to obtain a fitting straight line, and then the angle between this fitting straight line and the machine tool spindle axis is calculated. This angle is used as the drill bit machining hole direction accuracy eigenvalue;

[0071] The drill bit machining hole straightness eigenvalue is, based on the resultant force of each calculation unit, in the force space, the end points of the resultant forces of each unit are subjected to spatial straight line fitting to obtain a fitting straight line, and the sum value of the minimum perpendicular distances between all the resultant force end points and this fitting straight line is calculated and statistically analyzed. This sum value is used as the drill bit hole machining hole straightness eigenvalue, that is:

[0072] $s_t = \sum d$ j

[0073] where $s_t$ is the characteristic value of the straightness of the hole machined by the drill bit, and $d$ j is the perpendicular distance from the end point of the resultant force of the $j$-th unit to the fitted straight line, and $d$ j $\geq 0$.

[0074] The roundness characteristic value of the hole machined by the drill bit is that, based on the resultant force of each calculation unit, in the force space, two coaxial cylinders are used to envelope all the end points of the unit resultant forces, and the difference between the radii of the two coaxial envelope cylinders is determined as the roundness characteristic value of the hole machined by the drill bit, that is:

[0075] $\Delta = r$ max $- r$ min

[0076] where $\Delta$ is the roundness characteristic value of the hole, and $r$ max is the maximum radius of the envelope cylinder, and $r$ min is the minimum radius of the envelope cylinder.

[0077] The eccentricity characteristic value of the hole machined by the drill bit is that, based on the magnitude and direction of the radial force during the drill withdrawal process, the resultant force is obtained by synthesizing all the radial forces, and the magnitude of this resultant force is taken as the eccentricity characteristic value of the hole machined by the drill bit, that is:

[0078]

[0079] where is the eccentricity vector, and the magnitude of this vector is the eccentricity characteristic value.

[0080] In step 400, the quality of hole machining is evaluated based on the drill withdrawal radial force and the characteristic parameters.

[0081] During the development of the drill bit, relevant characteristic parameters can be quickly obtained with the help of this embodiment. During the test, if it is found that the characteristic value of the machining stability of the drill bit increases, it indicates that the drill bit machining is unstable, which may be caused by factors such as unreasonable drill bit structure, machining parameters, and inappropriate workpieces; if it is found that the characteristic value of the direction accuracy of the hole drilled by the drill bit increases, it indicates that the drill bit has insufficient performance in maintaining a stable direction, which may be caused by factors such as insufficient symmetry accuracy of the manufactured drill bit, insufficient stiffness, inappropriate machining parameters, and non-compliant surfaces of the workpieces to be machined; if it is found that the characteristic value of the straightness of the hole drilled by the drill bit increases, it indicates that the drill bit machining is unstable, which may be caused by factors such as unreasonable drill bit structure, insufficient symmetry accuracy of the drill bit, insufficient stiffness, and poor uniformity of the workpiece material; if it is found that the characteristic value of the roundness of the hole drilled by the drill bit increases, it indicates that the roundness of the hole is poor, which may be caused by factors such as non-uniform workpiece material, insufficient drill bit stiffness, and unreasonable drill bit cutting structure; if it is found that the characteristic value of the eccentricity degree increases, it indicates that the eccentricity of the hole relative to the spindle increases, which may be caused by factors such as insufficient drill bit stiffness and workpiece displacement.

[0082] During the development of the drill bit, it is not limited to the above characteristic values.

[0083] Taking the time history curve of the radial force magnitude as the object of investigation, if it is found that the radial force corresponding to the curve is 0 for a period of time, it may be affected by factors such as asymmetric drill tip angles, unequal edge lengths, and unreasonable drill tip angle designs.

[0084] Some information is difficult to quantify through a definite characteristic value.

[0085] Taking the time history curve of the radial force magnitude as the object of investigation, if it is found that there are step phenomena in the curve, manifested as sudden changes in the average values of some segments of the curve, it indicates that stepped holes have occurred during the drilling process of the drill bit, which may be caused by factors such as asymmetric drill tip angles and unequal edge lengths.

[0086] A method for evaluating the quality of hole machining based on the radial force during drill retraction provided in this embodiment. This solution does not require workpiece disassembly and can efficiently obtain corresponding data at the same time when the drilling test hole machining is completed, obtaining the quality accuracy of the machined hole. Moreover, when obtaining the corresponding data, it does not affect the drilling process and does not have an impact on the machined hole itself, ensuring the accuracy of the evaluation results. It is applicable to any drilling test scenario where the accuracy of the machined hole needs to be obtained in a timely manner, especially in scenarios where it is not convenient to remove the workpiece to measure the hole accuracy. This solution can easily achieve automatic measurement and evaluation by combining a force measuring device and a corresponding automatic calculation program, without a large amount of manual intervention, and can avoid errors caused by human subjective factors, providing a low-cost, efficient, stable and reliable hole accuracy evaluation solution, which is applicable to scenarios where it is not convenient for manual participation. The characteristic parameters of this solution are specifically designed for the relevant calculations in the process of drilling test hole machining. By evaluating the quality of the machined hole in the drilling test, the inclination of the machined hole is obtained from the radial force during drill retraction and the characteristic parameters, indirectly reflecting the symmetry of the drill tip angle, and the step performance of the machined hole is obtained, indirectly reflecting the symmetry of the drill tip angle and the difference in cutting edge length; through different comparative tests, the suitable working conditions and machining materials for the drill bit are found, providing new ideas for the research and development of the drill bit and shortening the research and development cycle of the drill bit.

[0087] Embodiment 2

[0088] Different from Embodiment 1, the radial force measuring device is a shank-type dynamometer 6, as Figure 4 shown. When installing, one end of the shank-type dynamometer 6 is connected to the spindle 5 of the drilling equipment machine tool, and the other end is connected to the drill bit 4. The lower surface of the workpiece is in contact with and fixed to the upper surface of the working table of the drilling equipment. The shank-type dynamometer should be checked before installation to confirm its good condition. Ensure that the installation surfaces between the shank-type dynamometer and the spindle, and between the shank-type dynamometer and the drill bit are both kept clean.

[0089] The shank-type dynamometer 6 can adopt a KISTLER 9170B wireless four-component rotary dynamometer (hereinafter referred to as the shank-type dynamometer), and is equipped with a data acquisition card and supporting software for data acquisition. This dynamometer can be used to measure the three mutually perpendicular forces Fx, Fy, Fz, and the axial torque Mz acting on the drill bit. When using this device, it is necessary to ensure that the battery inside the device has sufficient power and the wireless communication with the wireless receiver is unobstructed. In addition, the "central water outlet" function of the machine tool cannot be turned on during machining.

[0090] Different from Embodiment 1, since the shank-type dynamometer rotates with the spindle, its mechanical coordinate system also rotates accordingly. Therefore, it is necessary to transform the force into a coordinate system with the machine tool as the reference, that is

[0091] F0 = RF m

[0092] Wherein, F0 is the force matrix with the machine tool as the coordinate system at a certain moment, R is the coordinate transformation matrix at a certain moment, and F m is the force matrix measured by the handle-type dynamometer at a certain moment.

[0093] Furthermore, Fr with the machine tool as the coordinate system can be obtained.

[0094] In Step 100 and Step 200, the radial forces required for each step are measured by the handle-type dynamometer.

[0095] A method for evaluating the hole machining quality based on the radial force during drill retraction provided in this embodiment deeply analyzes the drilling system, the drilling process, and the contact force, and finds that on the one hand, the contact force is manifested as the force borne by the workpiece, which is transmitted to the plate-type multi-component dynamometer and measured by this device; on the other hand, it is manifested as the force borne by the drill bit, which is transmitted to the handle-type dynamometer and measured by this device. The two forces are equal in magnitude and opposite in direction. Therefore, this solution optimizes the evaluation process, can adapt to a variety of radial force measurement devices, meets the installation requirements of different drilling systems, and improves the adaptability and versatility.

[0096] Embodiment Three

[0097] Different from Embodiment One and Embodiment Two, different drill bits are used to machine the same workpiece under the same working conditions, and the machining quality of the holes is evaluated based on the radial force during drill retraction (the method refers to Embodiment One and Embodiment Two), and the evaluation results of the hole machining quality are compared to achieve the purpose of comparing different drill bits.

[0098] The different drill bits refer to drill bits with different sizes, structural forms, used time, substrate materials, or coating materials.

[0099] The same working conditions mean that the spindle rotation speed, feed speed, cooling method, machining method, hole depth, machining machine tool, and clamping length are all the same.

[0100] The same workpiece means that the material grade, heat treatment process, and drilling surface of the workpiece are all the same.

[0101] After independent tests on these different drill bits, different characteristic parameters are obtained, including the characteristic value of the machining stability of the drill bit, the characteristic value of the direction accuracy of the hole machined by the drill bit, the characteristic value of the roundness of the hole machined by the drill bit, the characteristic value of the eccentricity of the hole machined by the drill bit, and the characteristic value of the straightness of the axis of the hole machined by the drill bit. According to the differences in the corresponding test characteristic values of each drill bit, the advantages and disadvantages of the drill bits are determined, and further, the optimization directions of the drill bit structure, size, substrate material, and coating material are found.

[0102] For example, there are three drill bits A, B, and C with the same size but different structural forms, and three groups of comparative tests A, B, and C are set up. The same machining parameters are used to drill holes in the same workpiece, and the characteristic values are obtained respectively.

[0103] Analysis found that the eigenvalue of each test in Group A is the smallest, and the eigenvalue of each test in Group C is the largest, indicating that under the current processing parameters and workpiece conditions, the drill bit corresponding to Group A has a better structure.

[0104] Example 4

[0105] Different from Examples 1, 2, and 3, drills of the same model and the same used time are used to process the same workpiece under different working conditions, and the processing quality is evaluated based on the radial force during drill withdrawal (the method refers to Examples 1 and 2), and the hole processing quality evaluation results are compared to find the appropriate working conditions.

[0106] Drills of the same model and the same used time mean that the drill bit size, structure form, used time, substrate material, and coating material are all the same.

[0107] Different working conditions refer to different rotational speeds, feed speeds, feed per revolution, cooling conditions, processing methods, processing machines, or clamping lengths.

[0108] After independent tests on these different drills, different characteristic parameters are obtained, including drill bit processing stability, drill bit processing hole direction accuracy, drill bit processing hole roundness, drill bit processing hole eccentricity, and drill bit processing hole axis straightness. According to the different test eigenvalue corresponding to each working condition, the advantages and disadvantages of the working condition corresponding to the current drill bit are determined, and the optimization direction of the working condition is further found.

[0109] For example, there are several drills of the same existing model and used time, which are divided into three groups: A, B, and C. Each group corresponds to different processing parameters, and drilling tests are carried out on the same workpiece to obtain eigenvalues respectively.

[0110] Analysis found that the eigenvalue of each test in Group A is the smallest, and the eigenvalue of each test in Group C is the largest, indicating that for the drill bit of the current model and used time, the processing parameters corresponding to Group A are better.

[0111] Example 5

[0112] Different from Examples 1, 2, 3, and 4, drills of the same model and the same used time are used to process different workpieces under the same working conditions, and the processing quality is evaluated based on the radial force during drill withdrawal (the method refers to Examples 1 and 2), and the hole processing quality evaluation results are compared to find the most suitable processing material for the current drill bit.

[0113] Different workpieces refer to different workpiece material grades, heat treatment processes, and drilling surfaces.

[0114] After independently evaluating these different drills, different characteristic parameters are obtained, including drill machining stability, drill machining hole direction accuracy, drill machining hole roundness, drill machining hole eccentricity degree, and drill machining hole axis straightness degree. According to the different test characteristic values corresponding to each working condition, the applicability differences of the current drill for different workpieces are determined, and further the optimization direction of the machined workpiece is found out.

[0115] For example, there are several drills of the same existing model and used time, which are divided into five groups: A, B, C, D, and E. Each group corresponds to a different workpiece. The workpiece material grades are the same, the heat treatment processes are the same, and the angles between the normal direction of the workpiece surface to be machined and the spindle axis are different, which are 1°, 3°, 5°, 7°, and 9° respectively. Tests are carried out respectively to obtain characteristic values.

[0116] Analysis finds that as the angle increases, the characteristic value of the hole direction accuracy increases significantly, indicating that the drill is easily affected by the machining surface, and inclined drilling should be avoided as much as possible during use.

[0117] The above are only embodiments of the present invention. Specific structures and common knowledge such as characteristics well known in the art are not described in detail here. Those of ordinary skill in the art know all the common general technical knowledge in the technical field to which the invention belongs before the application date or priority date, can know all the prior arts in this field, and have the ability to apply the conventional experimental means before this date. Those of ordinary skill in the art can, under the inspiration given in this application, combine their own abilities to improve and implement this solution. Some typical well-known structures or well-known methods should not be an obstacle to those of ordinary skill in the art to implement this application. It should be noted that for those skilled in the art, without departing from the structure of the present invention, several deformations and improvements can be made, which should also be regarded as the protection scope of the present invention, and these will not affect the implementation effect of the present invention and the practicality of the patent.

Claims

1. A hole machining quality assessment method based on back-drilling radial force, characterized in that: The method comprises: Step 100, performing a drilling test to drill a hole of a preset depth on a test workpiece; Step 200, using a radial force measuring device to measure the radial force generated during the drill withdrawal process of the drilling test to obtain drill withdrawal radial force data; Step 300, calculating characteristic parameters according to the preprocessed drill back radial force data; Step 400, evaluating the quality of the hole processed by the drilling test by using the radial force of the drill withdrawal and the characteristic parameters.

2. A hole machining quality assessment method based on back-drilling radial force according to claim 1, characterized in that: In step 200, the process of measuring the generated radial force and obtaining the drill back radial force data includes: S201, during the hole processing, after the drill bit drills into place, the drill bit continues to maintain the original speed and hovers; S202, turning on the cutting fluid, cooling the hole to room temperature and ensuring that there is no chip attached to the inner wall of the hole; S203, turning off the cutting fluid and starting the radial force measuring device before drilling back; during the drilling back process, drilling back at a uniform rotation speed and feed speed, and measuring the radial force generated during the drilling back process by the radial force measuring device; S205, the measurement is terminated until the drill is completely withdrawn from the processed hole, the radial force data of the drill withdrawal is obtained, and the number of revolutions of the drill before the drill is completely withdrawn meets the preset requirements; S206, saving the drill back radial force data and closing the radial force measuring device.

3. The hole machining quality assessment method based on back-drilling radial force according to claim 1 is characterized in that: The radial force measuring device is a flat plate multi-component force measuring device or a handle-type dynamometer; During installation, the lower surface of the flat-plate multi-component force measuring device contacts and is fixed to the upper surface of the drilling equipment workbench, and the upper surface contacts and is fixed to the lower surface of the workpiece; during installation, one end of the handle-type dynamometer is connected to the main shaft of the drilling equipment, and the other end is connected to the drill bit, and the lower surface of the workpiece contacts and is fixed to the upper surface of the drilling equipment workbench.

4. The hole machining quality assessment method based on back-drilling radial force according to claim 1, characterized in that: In step 300, the characteristic parameters include a characteristic value of drill processing stability, a characteristic value of drill processing hole roundness, a characteristic value of drill processing hole direction accuracy, a characteristic value of drill processing hole straightness, and a characteristic value of drill processing hole eccentricity.

5. The hole machining quality assessment method based on back-drilling radial force according to claim 4 is characterized in that: Based on the magnitude and direction of the radial force of the drill bit during the drill withdrawal process, the spindle is preset as one calculation unit, and all radial forces in the unit are synthesized to obtain the resultant force of the calculation unit. The resultant bending moment is ignored, and the starting point of the resultant force is placed at the midpoint of the projection line segment of the spindle axis corresponding to the unit.

6. A hole machining quality assessment method based on back-drilling radial force according to claim 5, characterized in that: The standard deviation of the radial force of the drill bit during the drill withdrawal process is taken as the characteristic value of the drill bit processing stability; Based on the resultant force of each calculation unit, two coaxial cylinders are used to envelop the end points of all unit resultant forces in the force space, and the difference between the radii of the two coaxial cylinders is taken as the characteristic value of the roundness of the drill hole.

7. The hole machining quality assessment method based on back-drilling radial force according to claim 5, characterized in that: Based on the resultant force of each calculation unit, a spatial straight line fitting is performed on the end point of the resultant force of each unit in the force space to obtain a fitting straight line. Then, the angle between the fitting straight line and the axis of the machine tool spindle is calculated, and the angle is used as the characteristic value of the accuracy of the drill hole processing direction.

8. The hole machining quality assessment method based on back-drilling radial force according to claim 5, characterized in that: Based on the resultant force of each calculation unit, a spatial straight line fitting is performed on the end point of each unit resultant force in the force space to obtain a fitting straight line. The sum of the minimum vertical distances between all the end points of the resultant force and the fitting straight line is calculated and counted, and the sum is used as the characteristic value of the straightness of the drill hole processing hole.

9. The hole machining quality assessment method based on back-drilling radial force according to claim 5, characterized in that: Based on the magnitude and direction of the radial force during the drill withdrawal process, all radial forces are synthesized to obtain the resultant force, and the magnitude of the resultant force is taken as the characteristic value of the eccentricity of the drill hole.

10. The hole machining quality assessment method based on back-drilling radial force according to claim 1, characterized in that: The method further includes step 500, in which steps 100 to 400 are repeated in different scenarios to obtain and compare multiple sets of characteristic parameters so as to analyze and optimize the drill performance and application conditions in different scenarios; wherein the different scenarios include: using different drill bits to process the same workpiece under the same working condition, using drill bits of the same model and the same usage time to process the same workpiece under different working conditions, and using drill bits of the same model and the same usage time to process different workpieces under the same working condition.

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