Milling cutter tip blunt circle radius identification method based on ploughing force

Abstract

The invention particularly relates to a milling cutter tip blunt circle radius identification method based on ploughing force. The method comprises the following steps: firstly, proposing a principle of directly matching a milling force waveform with cutter teeth according to a single-tooth milling experiment and cutter eccentric parameters; secondly, considering cutter eccentricity, cutter deformation and material accumulation phenomena in the actual milling process, establishing an actual cutting edge movement track, and further solving the actual instantaneous undeformed chip thickness; meanwhile, a pure ploughing area is determined according to the relation between the minimum undeformed chip thickness MUCT and the blunt circle radius of a tool nose; and according to the actual instantaneous undeformed chip thickness, determining the instantaneous position angle of the corresponding ploughing force and the pure ploughing area, and finally substituting the instantaneous position angle into the function relationship between the blunt circle radius of the tool nose and the ploughing force in the pure ploughing slip line model to realize identification of the blunt circle radius of the tool nose. According to the method, a milling force and cutter tooth matching principle is utilized, so that the blunt circle radiuses of cutter points of different cutter teeth are identified in different cutting states.

Description

Technical Field

[0001] The present invention relates to the technical field of machining, and particularly relates to a method for identifying the nose radius of a milling cutter based on plowing force. Background Art

[0002] The nose radius directly affects the material flow mechanism and generates a plowing effect. During the actual milling process, the nose radius of the cutter will change as the milling process progresses. Therefore, accurately identifying the nose radius of the cutter during the actual milling process is of great significance for real-time evaluation of the state of the milling cutter and in-depth study of the cutting mechanism and the quality of the machined surface. The existing methods for identifying the nose radius of a milling cutter based on measured milling forces mainly include two types. One is to establish a data-driven artificial intelligence model by training a large amount of experimental or simulation data to identify the nose radius. The second is to indirectly estimate the nose radius by solving an intermediate quantity related to the nose radius.

[0003] Document 1 "Li Y, Wan M, Wen D Y, et.al. Deep learning-based method for characterizing the cutter runout phenomenon in micro milling[J]. Journal of Materials Processing Technology, 2023, 321: 118151." discloses a method based on deep learning to identify the tool eccentricity parameter and the nose radius of the cutter during micro milling. It comprehensively considers the influence of tool eccentricity and nose radius on the cutting force, and uses a large amount of simulated cutting force data and the corresponding nose radius and eccentricity values as model training data to identify the nose radius.

[0004] Document 2 "Dib M H M, Duduch J G, Jasinevicius R G. Minimum chip thickness determination by means of cutting force signal in micro endmilling[J]. Precision Engineering, 2018, 51: 244 - 262." discloses a method for determining the minimum uncut chip thickness (MUCT) based on the change in the measured milling force at the critical chip formation moment, and indirectly estimates the nose radius according to the relationship between MUCT and the nose radius.

[0005] The typical characteristics of the above references are as follows: for the above methods of identifying the tool nose radius in the milling process, either a large amount of data needs to be trained time-consuming as input, or complex experiments are carried out to indirectly estimate the tool nose radius by solving intermediate quantities. Both require a large amount of time and do not reveal the direct relationship between the milling force and the tool nose radius from the mechanism perspective.

[0006] It should be noted that the information disclosed in the above background art section is only used to enhance the understanding of the background of the present invention, and therefore may include information that does not constitute the prior art known to those of ordinary skill in the art. Summary of the Invention

[0007] In order to overcome the defects that the existing method of identifying the tool nose radius based on the measured milling force is time-consuming and cannot directly identify the tool nose radius from the mechanism perspective, the present invention provides a method for identifying the tool nose radius of a milling cutter based on the plowing force.

[0008] Other characteristics and advantages of the present invention will become apparent through the following detailed description, or be learned in part through the practice of the present invention.

[0009] According to a first aspect of the present invention, there is provided a method for identifying the tool nose radius of a milling cutter based on the plowing force, the method comprising:

[0010] Performing a single-tooth milling experiment to obtain a milling force waveform, and matching the milling force waveform with the corresponding tooth of the cutter based on the tool eccentricity angle and the given cutter tooth space angle;

[0011] Establishing a tool eccentricity model, and calculating the actual cutting edge movement trajectory under the action of tool eccentricity based on the tool eccentricity model;

[0012] Calculating the actual tool deformation amount based on the measured milling force; combining the actual tool deformation amount and the actual cutting edge movement trajectory under the action of tool eccentricity to calculate the actual cutting edge trajectory considering tool eccentricity and deformation;

[0013] Calculating the actual instantaneous undeformed chip thickness based on the actual cutting edge trajectory considering tool eccentricity and deformation;

[0014] Determining the pure plowing region according to the magnitude relationship between the minimum undeformed chip thickness MUCT and the actual instantaneous undeformed chip thickness;

[0015] Substituting the instantaneous rotation position angle and the plowing force in the pure plowing region into the functional relationship between the tool nose radius and the plowing force in the pure plowing slip line model to calculate the tool nose radius.

[0016] In some exemplary embodiments, the matching of the milling force waveform with the corresponding tooth of the cutter based on the tool eccentricity angle and the given cutter tooth space angle is performed using the following formula:

[0017] ηj = cos(λ - (j - 1)φ p ) - cos(λ - (j - 2)φ p )

[0018] where η j represents the magnitude of the relative undeformed chip thickness of the j-th tooth, λ is the tool eccentricity angle, and φ p is the given angular pitch of the milling cutter teeth.

[0019] In some exemplary embodiments, calculating the actual cutting edge motion trajectory under the action of tool eccentricity based on the tool eccentricity model includes:

[0020] Determining the unequal rotational radii and the actual relative rotational angle between teeth caused by tool eccentricity according to the tool eccentricity model; calculating the actual cutting edge motion trajectory under the action of tool eccentricity based on the unequal rotational radii and the rotational angle between teeth caused by tool eccentricity.

[0021] In some exemplary embodiments, to determine the unequal rotational radii and the rotational angle between teeth caused by tool eccentricity according to the tool eccentricity model, the following formula is used:

[0022]

[0023] where R j is the equivalent rotational radius of the j-th tooth under the action of tool eccentricity, and α j represents the angle between the tool eccentricity direction and the line connecting the tool rotation center and the j-th tooth;

[0024] Taking the first tooth as a reference, the actual relative rotational angle is calculated by the following formula:

[0025]

[0026] where φ ar，j represents the actual relative rotational angle of the j-th tooth relative to the first tooth.

[0027] In some exemplary embodiments, to calculate the actual cutting edge motion trajectory under the action of tool eccentricity based on the unequal rotational radii and the rotational angle between teeth caused by tool eccentricity, the following formula is used:

[0028]

[0029] where (x j (t), y j (t)) are the motion coordinates of the j-th cutting edge at time t, φ1(t) is the instantaneous rotational position angle of the first tooth at time t, f z is the feed per tooth, T is the milling cutter rotation period, and N is the number of teeth of the milling cutter.

[0030] In some exemplary embodiments, the actual tool deformation amount is calculated based on the measured milling force, and the following formula is used:

[0031]

[0032] where δ j represents the actual tool deformation amount under the action of the measured milling force, F j is the measured milling force matched with the j-th tooth obtained based on Step 1, l is the tool overhang length, E represents the tool elastic modulus, and I represents the moment of inertia of the milling cutter cross-section.

[0033] In some exemplary embodiments, the actual cutting edge trajectory considering tool eccentricity and deformation is calculated by combining the actual tool deformation amount and the actual cutting edge movement trajectory under tool eccentricity, and the following formula is used:

[0034]

[0035] where represents the actual cutting edge trajectory of the j-th tooth considering the influence of tool eccentricity and tool deformation, represents the angle between the resultant force direction and the x-axis.

[0036] In some exemplary embodiments, the pure plowing region is determined according to the magnitude relationship between the minimum undeformed chip thickness MUCT and the actual instantaneous undeformed chip thickness, specifically:

[0037] When the difference between the actual instantaneous undeformed chip thickness and the minimum undeformed chip thickness MUCT is less than zero, it is denoted as the pure plowing effect region.

[0038] In some exemplary embodiments, the minimum undeformed chip thickness MUCT is calculated based on the initial tool nose radius, and the following formula is used:

[0039] h min = 0.23r e0

[0040] where r e0 is the initial tool nose radius, and h min is the magnitude of MUCT.

[0041] In some exemplary embodiments, the expression of the functional relationship between the tool nose radius and the plowing force in the pure plowing slip line model is as follows:

[0042] F y (φ(t i )) = F t sin φ(t i ) - F r cos φ(ti )

[0043] Among them, is the instantaneous rotational position angle, and F t represents the tangential force, and F r represents the radial force;

[0044]

[0045] Among them, b is the cutting width, ω0 is the angle between the bottom point of the slip-line field and the β line, and σ m is the hydrostatic stress, τ is the shear stress, is the geometric length of the pure plowing region;

[0046] σ m , τ, are calculated through the following equations:

[0047]

[0048] Among them, A JC is the material yield stress, B JC and n JC are the material strain hardening coefficient and exponent respectively, C JC is the strain rate constant, σ is the flow stress, ε is the shear strain, is the strain rate, is the reference strain rate, γ is the engineering strain, is the engineering strain rate, h1 is the material stacking height, and V A is the cutting speed.

[0049] The method for identifying the nose radius of a milling cutter based on the plowing force provided by the embodiments of the present invention first distributes the milling force waveform to the corresponding cutter teeth through a single-tooth milling experiment according to the principle of matching the milling force with the cutter tooth number; then establishes a tool eccentricity model and considers the actual cutting edge movement trajectory under the action of tool eccentricity; then substitutes the measured milling force into the calculation based on the cantilever beam theory to obtain the true tool deformation caused by the milling force, and comprehensively considers the influence of tool deformation and tool eccentricity on the actual cutting edge trajectory, thereby calculating the actual instantaneous undeformed chip thickness. Finally, the pure plowing region is determined according to the relationship between MUCT and the initial nose radius, and the corresponding plowing force and the instantaneous position angle are substituted into the slip-line model for solution to obtain the nose radius. Compared with the given document 1, the present invention only needs to conduct a set of milling experiments to achieve identification without a large number of experiments or simulation samples; compared with the given document 2, the present invention not only directly identifies the nose radius through the milling force, but also does not need to involve complex experiments.

[0050] It should be understood that the above general description and the following detailed description are merely exemplary and explanatory, and do not limit the present invention. Description of the Drawings

[0051] The drawings herein are incorporated into and constitute a part of this specification, showing embodiments consistent with the present invention, and are used together with the specification to explain the principles of the present invention. Obviously, the drawings in the following description are only some embodiments of the present invention, and those of ordinary skill in the art can obtain other drawings based on these drawings without creative efforts.

[0052] Figure 1 It is a flowchart of a method for identifying the nose radius of a milling cutter based on the plowing force provided by an embodiment of the present invention;

[0053] Figure 2 For the embodiments of the present invention, when the milling distances are 3000 millimeters and 141000 millimeters respectively, taking h j (φ(t i )) = 1 micron as an example, it illustrates how to identify the nose radius of different teeth based on the instantaneous rotational position angle of the tool and the measured plowing force;

[0054] Figure 3 It is a comparison diagram of the identification results and measurement results of the nose radius of all teeth during the entire milling process in the embodiments of the present invention. Detailed Embodiments

[0055] Now, example embodiments will be described more fully with reference to the drawings. However, the example embodiments can be implemented in various forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that the present invention will be more complete and comprehensive, and the concept of the example embodiments will be fully conveyed to those skilled in the art. The features, structures, or characteristics described can be combined in any suitable manner in one or more embodiments.

[0056] In addition, the drawings are only schematic illustrations of the present invention and are not necessarily drawn to scale. The same reference numerals in the drawings denote the same or similar parts, and thus repeated descriptions thereof will be omitted. Some of the block diagrams shown in the drawings are functional entities and do not necessarily correspond to physically or logically independent entities. These functional entities can be implemented in software form, or in one or more hardware modules or integrated circuits, or in different networks and / or processor devices and / or microcontroller devices.

[0057] A method for identifying the nose radius of a milling cutter based on plowing force applicable to different milling processes and different cutting edges is provided in the exemplary embodiment to address the drawbacks and deficiencies of the prior art, and only one set of milling experiments is required. The method first proposes a principle of directly matching the milling force waveform with the cutting edge based on single-tooth milling experiments and tool eccentricity parameters; then, considering tool eccentricity, tool deformation, and material accumulation phenomena in the actual milling process, the actual cutting edge motion trajectory is established to solve the actual instantaneous undeformed chip thickness; at the same time, the pure plowing region is determined according to the relationship between the minimum undeformed chip thickness (MUCT) and the nose radius of the cutting edge; the plowing force and the instantaneous position angle of the pure plowing region corresponding to the actual instantaneous undeformed chip thickness are determined, and finally, the function relationship between the nose radius of the cutting edge and the plowing force in the pure plowing slip line model is substituted to identify the nose radius of the cutting edge.

[0058] Expected technical effect: The method for identifying the nose radius of the milling cutter provided by the present invention is based on the characteristics that only plowing effect occurs during the pure plowing process and the chip thickness changes during the milling process. By using the principle of matching the milling force with the cutting edge, the nose radius of different cutting edges can be identified under different cutting conditions.

[0059] Reference Figure 1 As shown, the method for identifying the nose radius of the milling cutter based on plowing force may specifically include the following steps:

[0060] Conduct a single-tooth milling experiment to obtain the milling force waveform, and match the milling force waveform with the corresponding cutting edge based on the tool eccentricity angle and the given angular pitch of the milling cutter teeth;

[0061] Establish a tool eccentricity model, and calculate the actual cutting edge motion trajectory under the action of tool eccentricity based on the tool eccentricity model;

[0062] Calculate the actual tool deformation amount based on the measured milling force; combine the actual tool deformation amount and the actual cutting edge motion trajectory under the action of tool eccentricity to calculate the actual cutting edge trajectory considering tool eccentricity and deformation;

[0063] Calculate the actual instantaneous undeformed chip thickness based on the actual cutting edge trajectory considering tool eccentricity and deformation;

[0064] Determine the pure plowing region according to the magnitude relationship between the minimum undeformed chip thickness MUCT and the actual instantaneous undeformed chip thickness;

[0065] Substitute the instantaneous rotational position angle of the pure plowing region and the plowing force into the function relationship between the nose radius of the cutting edge and the plowing force in the pure plowing slip line model to calculate the nose radius of the cutting edge.

[0066] The above steps are specifically as follows:

[0067] Step 1. Measure the cutter eccentricity parameters ρ and λ, and conduct single-tooth milling experiments according to the following conditions:

[0068]

[0069] where ρ is the cutter eccentricity, λ is the cutter eccentricity angle, a p is the axial depth of cut, β s is the helix angle of the milling cutter, R is the radius of the milling cutter, a e is the radial depth of cut, and N is the number of teeth of the milling cutter. The cutter eccentricity parameters ρ and λ are measured according to the method in the literature "Wan M, Lu M S, Zhang W H, et.al. A new method for identifying the cutter runout parameters in flat end milling process. Materials Science Forum. Trans Tech Publications Ltd, 2012, 697:71 - 74.".

[0070] Step 2. According to the measured cutter eccentricity angle λ and the given tooth space angle φ p of the milling cutter, based on the principle that the undeformed chip thickness is proportional to the milling force, calculate all the teeth through the following formula, and match the tooth numbers defined by the cutter eccentricity with the measured milling force waveforms:

[0071] η j = cos(λ - (j - 1)φ p ) - cos(λ - (j - 2)φ p )

[0072] where η j represents the magnitude of the relative undeformed chip thickness of the j-th tooth.

[0073] Sort the relative undeformed chip thicknesses of each calculated tooth, and determine the corresponding milling force waveform based on the sorting relationship.

[0074] Step 3. Establish an unequal rotation radius R j and an unequal rotation tooth space angle model caused by cutter eccentricity according to the following formula:

[0075]

[0076] where R j is the equivalent rotation radius of the j-th tooth under the action of cutter eccentricity. α j represents the angle between the cutter eccentricity direction and the line connecting the cutter rotation center and the j-th tooth.

[0077] Step Four: Taking the cutting tooth 1 as the reference, the actual relative rotation angle is calculated by the following formula:

[0078]

[0079] where represents the actual relative rotation angle of the j-th cutting tooth relative to the cutting tooth 1.

[0080] Step Five: According to the tool eccentricity model in Steps Three and Four, calculate the actual cutting edge movement trajectories of different cutting teeth at any time t under the influence of tool eccentricity:

[0081]

[0082] where (x j (t), y j (t)) are the movement coordinates of the j-th cutting edge at time t, is the instantaneous rotation position angle of the first cutting tooth at time t. f z is the feed per tooth, and T is the milling cutter rotation period.

[0083] Step Six: Use the following formula to calculate the actual tool deformation amount by using the measured milling force:

[0084]

[0085] where δ j represents the actual tool deformation amount under the action of the measured milling force, F j is the measured milling force matched with the j-th cutting tooth obtained based on Step One, l is the tool overhang length, E represents the tool elastic modulus, and I represents the moment of inertia of the milling cutter cross-section and is determined by the following formula:

[0086]

[0087] where D e is the equivalent diameter of the milling cutter, expressed as 0.8 times the diameter of the milling cutter.

[0088] Step Seven: According to the calculated actual deformation amount, based on the cutting edge movement trajectory affected by tool eccentricity obtained in Step Five, the actual cutting edge trajectory considering the influence of tool deformation is determined by the following formula:

[0089]

[0090] where represents the actual cutting edge trajectory of the j-th cutting tooth considering the influence of both tool eccentricity and tool deformation. represents the angle between the resultant force direction and the x-axis.

[0091] Step 8: According to the actual cutting edge trajectory considering tool eccentricity and deformation obtained in Step 7, refer to the method in the literature "Gao S, Duan X, Zhu K, et.al. Investigation of the tool flank wear influence on cutter-workpiece engagement and cutting force in micro milling processes[J]. Mechanical Systems and Signal Processing, 2024, 209: 111104." to solve the actual instantaneous undeformed chip thickness at any instantaneous rotation position angle of when

[0092] Step 9: According to the size of the initial tool nose radius r e0 , calculate MUCT using the following formula:

[0093] h min = 0.23r e0

[0094] where h min is the size of MUCT. When , it is the pure ploughing effect area. Record the instantaneous rotation position angle corresponding to the milling force sampling points that meet the conditions and the ploughing force

[0095] Step 10: Establish the functional relationship between the tool nose radius r e and the ploughing force through the following formulas:

[0096] F y (φ(t i )) = F t sinφ(t i ) - F r cosφ(t i )

[0097] where F t represents the tangential force, and F r represents the radial force, and its calculation is:

[0098]

[0099] Among them, b is the cutting width. ω0 represents the angle between the bottom point of the slip line field and the β line, which is calculated with reference to the literature "Wan M, Wen DY, Ma YC, et.al. On material separation and cutting force prediction in micromilling through involving the effect of dead metal zone[J]. International Journal of Machine Tools and Manufacture, 2019, 146: 103452.". σ m represents the hydrostatic stress, τ is the shear stress, is the geometric length of the pure ploughing area. σ m 、τ、 are calculated through the following equations:

[0100]

[0101] Among them, A JC is the material yield stress, B JC and n JC are the material strain hardening coefficient and exponent respectively, C JC is the strain rate constant, and these material parameters are determined with reference to the material parameter manual. σ is the flow stress, ε is the shear strain, is the strain rate, is the reference strain rate, γ is the engineering strain, is the engineering strain rate, h1 is the material stacking height, V A is the cutting speed.

[0102] According to the instantaneous rotation position angle obtained in step nine and the ploughing force substitute them into the slip line model in step ten and calculate the nose radius r e , and take the average value, which is the finally identified nose radius size.

[0103] Example 1

[0104] In the experiment, a flat-bottomed carbide end mill with the number of teeth N = 3, radius R = 2 mm, helix angle β s = 45 degrees, normal rake angle α n = 5 degrees, initial nose radius r e0 = 9.39 microns, tool overhang length l = 22 mm, tool modulus E = 590 GPa is used in a three-coordinate vertical machining center with the down milling cutting method, spindle speed n = 2000 r / min, radial depth of cut a e = 1 mm, axial depth of cut ap = 0.5 mm, feed per tooth f z The milling wear test of aluminum alloy Al7050-T7451 was carried out with the cutting parameters of = 0.03 mm / tooth to verify the proposed method. The wear test measurement index was the cutting distance along the feed direction. The milling force was recorded every 3000 mm, and the nose radius was estimated online. The true nose radius of each tooth of the milling cutter was measured for comparison. The total cutting distance was 150000 mm.

[0105] Step 1: Measure the tool eccentricity parameter by referring to the method in the literature "Wan M, Lu M S, Zhang W H, et.al. A new method for identifying the cutter runout parameters in flat end milling process. Materials Science Forum. Trans Tech Publications Ltd, 2012, 697:71-74."

[0106] Through measurement, ρ = 0.0019 mm, λ = 75.2 degrees.

[0107] The cutting parameters given in this embodiment clearly meet the single-tooth milling test conditions:

[0108]

[0109] Step 2: For a three-tooth milling cutter, its tooth space angle According to the magnitudes of the tooth space angle and the eccentricity angle, calculate the corresponding η according to the following formula j :

[0110] η j = cos(λ - (j - 1)φ p ) - cos(λ - (j - 2)φ p )

[0111] We get η1 = 1.22, η2 = -0.64, η3 = -1.67. At this time, the arrangement of the milling force waveforms from large to small corresponds to teeth 1, 2, and 3. Therefore, according to this matching principle, the milling force waveforms from large to small are correspondingly matched to teeth 1, 2, and 3, as noted in the appendix. Figure 2 It is noted in the appendix.

[0112] Step 3: Establish the unequal rotation radius R j caused by tool eccentricity and the unequal rotation tooth space angle model according to the following formula:

[0113]

[0114] Among them, Rj is the equivalent rotational radius of the j-th cutting tooth under the action of tool eccentricity. α j represents the angle between the tool eccentricity direction and the line connecting the tool rotation center and the j-th cutting tooth.

[0115] Step Four: Taking tooth 1 as the reference, the actual relative rotation angle is calculated by the following formula:

[0116]

[0117] where, represents the actual relative rotation angle of the j-th cutting tooth relative to tooth 1.

[0118] Step Five: According to the tool eccentricity model in Steps Three and Four, calculate the actual cutting edge motion trajectories of different cutting teeth at any time t under the influence of tool eccentricity:

[0119]

[0120] where, (x j (t), y j (t)) are the motion coordinates of the j-th cutting edge at time t, is the instantaneous rotation position angle of the first cutting tooth at time t. f z is the feed per tooth, and T is the milling cutter rotation period.

[0121] Step Six: Use the following formula to calculate the actual tool deformation using the measured milling force:

[0122]

[0123] where, δ j represents the actual tool deformation under the action of the measured milling force, F j is the milling force matched with the j-th cutting tooth, l is the tool overhang length, E represents the tool elastic modulus, and I represents the moment of inertia of the milling cutter cross-section and is determined by the following formula:

[0124]

[0125] where, D e is the equivalent diameter of the milling cutter, expressed as 0.8 times the milling cutter diameter.

[0126] Step Seven: Based on the actual deformation amount obtained by calculation and the cutting edge motion trajectory affected by tool eccentricity obtained in Step Five, the actual cutting edge trajectory considering the influence of tool deformation is determined by the following formula:

[0127]

[0128] where, Denote the actual cutting edge trajectory of the \(j\)-th cutting tooth considering the influence of tool eccentricity and tool deformation. Denote the angle between the resultant force direction and the \(x\)-axis.

[0129] Step 8: According to the actual cutting edge trajectory considering tool eccentricity and deformation obtained in Step 7, refer to the method in the literature "Gao S, Duan X, Zhu K, et al. Investigation of the tool flank wear influence on cutter-workpiece engagement and cutting force in micro milling processes[J]. Mechanical Systems and Signal Processing, 2024, 209: 111104." to solve the actual instantaneous undeformed chip thickness at any instantaneous rotation position angle of \(\theta\).

[0130] Step 9: According to the initial tool nose radius \(r\) e0 = 9.39 μm, calculate MUCT using the following formula:

[0131] \(h\) min = 0.23\(r\) e0 = 2.16 μm

[0132] where \(h\) min is the magnitude of MUCT. At this time, substitute when \(\theta\) to obtain the pure ploughing effect region. Record the instantaneous rotation position angle

[0133] corresponding to the milling force sampling points that meet the conditions and the ploughing force e \(F_p\).

[0134] \(F\) y \((\varphi(t\) i )) = \(F\) t \(\sin\varphi(t\) i ) - \(F\) r \(\cos\varphi(t\) i )

[0135] where \(F\) t represents the tangential force, and \(F\) r represents the radial force, and their calculations are as follows:

[0136]

[0137] Here, b is the cutting width. ω0 represents the angle between the bottom point of the slip line field and the β line, which is calculated by referring to the literature "Wan M, Wen DY, Ma YC, et al. On material separation and cutting force prediction in micromilling through involving the effect of dead metal zone[J]. International Journal of Machine Tools and Manufacture, 2019, 146: 103452." σ m represents the hydrostatic stress. τ is the shear stress. is the geometric length of the pure plowing region. σ m , τ, are calculated by the following equations:

[0138]

[0139] where σ is the flow stress, ε is the shear strain, is the strain rate, is the reference strain rate, γ is the engineering strain, is the engineering strain rate, h1 is the material accumulation height, V A is the cutting speed. Referring to the material parameter manual, for Al7050 - T7451, A JC = 500 MPa, B JC = 240 MPa, n JC = 2.5, C JC = 0.003.

[0140] According to the instantaneous rotation position angle obtained in Step Nine and the plowing force Here, when the cutting distance is 141000 millimeters, micrometers is taken as an example. In the appendix Figure 1 at this time, the instantaneous position angle degrees of cutting edge 1, and the plowing force are substituted into the slip line model in Step Ten and the nose radius r e1 = 30.04 micrometers is calculated. Similarly, the nose radii of cutting edges 2 and 3 are calculated to be 24.07 and 21.09 micrometers respectively. The actually measured nose radii of the three cutting edges are 30.15, 24.37, and 22.35 micrometers respectively. It shows that the proposed method is in agreement with the measurement results.

[0141] In the appendix Figure 3It can be seen that the nose radius of the cutting tool gradually increases as the milling process progresses. For different cutting teeth in different milling stages, the method for identifying the nose radius of the cutting tool proposed in the present invention can make the identification results of different cutting teeth well match the measurement results, proving the effectiveness of the method for identifying the nose radius of the milling cutter based on the plowing force in the actual milling process.

[0142] Based on the characteristics of the milling process and the relationship between the plowing force and the nose radius of the cutting tool, the present invention proposes a new method for identifying the nose radius of the milling cutter based on the measured milling force from a mechanistic perspective. The significant advantage of this method is that it can identify the nose radius of different cutting teeth in different milling states through one or several experiments, and the identification results can well match the measurement results.

[0143] In addition, the above-mentioned drawings are only schematic illustrations of the processes included in the method according to the exemplary embodiments of the present invention, rather than for limiting purposes. It is easy to understand that the processes shown in the above-mentioned drawings do not indicate or limit the chronological order of these processes. Additionally, it is also easy to understand that these processes can be executed synchronously or asynchronously in, for example, multiple modules.

[0144] Those skilled in the art will readily think of other embodiments of the present invention after considering the specification and practicing the invention herein. This application is intended to cover any variations, uses, or adaptations of the present invention that follow the general principles of the present invention and include the common general knowledge or conventional technical means in the technical field not disclosed in the present invention. The specification and embodiments are only regarded as exemplary, and the true scope and spirit of the present invention are pointed out by the claims.

[0145] It should be understood that the present invention is not limited to the exact structures already described and shown in the drawings, and various modifications and changes can be made without departing from its scope. The scope of the present invention is only defined by the appended claims.

Claims

1. A method for identifying the nose radius of a milling cutter based on plowing force, characterized in that, The method includes: Conducting single-tooth milling experiments on the milling cutter to obtain the milling force waveform, and matching the milling force waveform with the corresponding cutter teeth based on the tool eccentricity angle and the given angular pitch between the cutter teeth of the milling cutter; Establishing a tool eccentricity model and calculating the actual cutting edge movement trajectory under the action of tool eccentricity based on the tool eccentricity model; Calculating the actual tool deformation based on the measured milling force; calculating the actual cutting edge trajectory considering tool eccentricity and deformation by combining the actual tool deformation and the actual cutting edge movement trajectory under the action of tool eccentricity; Calculating the actual instantaneous undeformed chip thickness based on the actual cutting edge trajectory considering tool eccentricity and deformation; Determining the pure ploughing region according to the magnitude relationship between the minimum undeformed chip thickness MUCT and the actual instantaneous undeformed chip thickness; Substituting the instantaneous rotation position angle and the ploughing force in the pure ploughing region into the functional relationship between the nose radius and the ploughing force in the pure ploughing slip-line model to calculate the nose radius; 2. The method for identifying the nose radius of a milling cutter based on plowing force according to claim 1, wherein The matching of the milling force waveform with the corresponding cutter teeth based on the tool eccentricity angle and the given angular pitch between the cutter teeth of the milling cutter adopts the following formula: η j = cos(λ - (j - 1)φ p ) - cos(λ - j - 2)φ p ) where η j represents the magnitude of the relative undeformed chip thickness of the j-th cutting edge, λ is the tool eccentricity angle, and φ p is the given angular pitch between the cutter teeth; Sorting the relative undeformed chip thicknesses of the calculated cutter teeth and determining the corresponding milling force waveform based on the sorting relationship; 3. The method for identifying the nose radius of a milling cutter based on plowing force according to claim 1, wherein The calculating of the actual cutting edge movement trajectory under the action of tool eccentricity based on the tool eccentricity model includes: Determining the unequal rotation radius and the actual relative rotation angle between the cutter teeth caused by tool eccentricity according to the tool eccentricity model; calculating the actual cutting edge movement trajectory under the action of tool eccentricity based on the unequal rotation radius and the angular pitch between the rotating cutter teeth caused by tool eccentricity; 4. The method for identifying the nose radius of a milling cutter based on plowing force according to claim 3, wherein The determining of the unequal rotation radius and the rotation angle between the cutter teeth caused by tool eccentricity according to the tool eccentricity model adopts the following formula: Among them, R j is the equivalent rotation radius of the j-th cutting edge under the action of tool eccentricity, and α j represents the angle between the tool eccentricity direction and the line connecting the tool rotation center and the j-th cutting edge; Taking the first cutter tooth as the reference, the actual relative rotation angle is calculated by the following formula: where φ ar，j represents the actual relative rotation angle of the j-th cutting tooth relative to the first cutting tooth.

5. The method for identifying the nose radius of a milling cutter based on plowing force according to claim 4, wherein The calculating of the actual cutting edge movement trajectory under the action of tool eccentricity based on the unequal rotation radius and the rotation angle between the cutter teeth caused by tool eccentricity adopts the following formula: Among them, (x j (t), y j (t)) are the motion coordinates of the j-th cutting edge at time t, φ1(t) is the instantaneous rotational position angle of the 1st tooth at time t, f z is the feed per tooth, T is the milling cutter rotation period, and N is the number of teeth of the milling cutter.

6. The method for identifying the nose radius of a milling cutter based on plowing force according to claim 5, characterized in that, The calculating of the actual tool deformation based on the measured milling force adopts the following formula: Among them, δ j represents the actual tool deformation under the measured milling force, F j is the measured milling force matched with the j-th tooth obtained based on the first step, l is the tool overhang length, E represents the tool elastic modulus, and I represents the moment of inertia of the milling cutter cross-section.

7. The method for identifying the nose radius of a milling cutter based on the plowing force according to claim 6, wherein The calculating of the actual cutting edge trajectory considering tool eccentricity and deformation by combining the actual tool deformation and the actual cutting edge movement trajectory under the action of tool eccentricity adopts the following formula: Among them, represents the actual cutting edge trajectory of the j-th cutting tooth considering the influence of tool eccentricity and tool deformation comprehensively, represents the angle between the resultant force direction and the x-axis.

8. The method for identifying the nose radius of a milling cutter based on plowing force according to claim 1, characterized in that, The determining of the pure ploughing region according to the magnitude relationship between the minimum undeformed chip thickness MUCT and the actual instantaneous undeformed chip thickness is specifically: When the difference between the actual instantaneous undeformed chip thickness and the minimum undeformed chip thickness MUCT is less than zero, it is denoted as the pure ploughing effect region; 9. The method for identifying the nose radius of a milling cutter based on plowing force according to claim 8, characterized in that, The minimum undeformed chip thickness MUCT is calculated based on the initial nose radius and adopts the following formula: h min ＝0.23r e0 where r e0 is the initial nose radius, and h min is the value of MUCT.

10. The method for identifying the nose radius of a milling cutter based on plowing force according to claim 1, wherein The expression of the functional relationship between the nose radius and the ploughing force in the pure ploughing slip-line model is as follows: F y (φ(t i )) = F t sin φ(t i ) - F r cos φ(t i ) Among them, is the instantaneous rotational position angle, and F t represents the tangential force, and F r represents the radial force; where b is the cutting width, ω0 is the angle between the bottom point of the slip line field and the β line, σ m is the hydrostatic stress, τ is the shear stress, is the geometric length of the pure plowing region; σ m , τ, are calculated by the following equations: Among them, A JC is the yield stress of the material, B JC and n JC are the strain hardening coefficient and exponent of the material respectively, C JC is the strain rate constant, σ is the flow stress, ε is the shear strain, is the strain rate, is the reference strain rate, γ is the engineering strain, is the engineering strain rate, h1 is the material stacking height, V A is the cutting speed.

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