A CNC machining method for controlling angular chatter

Abstract

This invention belongs to the field of aircraft manufacturing technology and discloses a CNC machining method for controlling corner chatter. Based on the classical calculation formula of cutting force and the classical formula of milling cutting thickness, a cutting force model at the milling corner is established, and the relationship expression between the cutting force at the milling corner and time is derived. The ratio of the cutting force at the milling corner to the cutting force before the milling corner is calculated as the speed reduction ratio at the milling corner. This solves the technical problems of "chatter" and "tool wobbling" that are prone to occur during corner machining. Compared with traditional methods, this method does not rely on the experience of technicians, scientifically and efficiently calculates the corner speed reduction ratio, and effectively reduces the probability of quality problems of parts caused by corner machining.

Description

Technical Field

[0001] This invention application belongs to the field of aircraft manufacturing - CNC machining technology, specifically relating to a CNC machining method for controlling angular chatter. Background Technology

[0002] Corners are a typical feature of CNC machining parts, commonly found in structural components such as frames, beams, ribs, joints, and partitions. At the corners of a machined part, the cutting area and contact area between the tool and the part increase dramatically, causing drastic fluctuations in cutting force and easily leading to "tool entrapment." This results in decreased machining quality at the corner, and may even damage the inner wall of the part and the tool. Traditional methods for corner machining include reducing the tool's cutting width and depth of cut, increasing the corner radius, and decreasing the corner feed rate. However, these methods rely heavily on the programming experience of the process engineers, demanding a high level of technical skill, and can only reduce the occurrence of "tool entrapment" to some extent. Therefore, a detailed study of the cutting force during corner machining is necessary to optimize the process programming strategy and ensure machining quality at the corners of the part. Summary of the Invention

[0003] This invention application proposes a CNC machining method for controlling corner chatter. Based on the classical calculation formula of cutting force and the classical formula of milling cutting thickness, a cutting force model at the milling corner is established, the relationship expression between the cutting force and time at the milling corner is derived, and the process programming strategy is optimized accordingly to ensure the machining quality at the corner of the part.

[0004] To achieve the aforementioned objectives, the technical solution adopted in this application is as follows:

[0005] A CNC machining method for controlling angular chatter includes the following steps:

[0006] Step 1: Calculate the four cutting force coefficient values;

[0007] Step 2: Apply the corner cutting force model calculation formula to calculate the maximum cutting force F at the corner. 2，MAX Using the traditional formula for calculating straight cutting force, the maximum cutting force F before the turning angle is calculated. 1，MAX ;

[0008] Step 3: Calculate the ratio η of the maximum cutting force before the corner and at the corner, and denot it as the corner speed reduction ratio;

[0009] Step 4: Input the corner deceleration ratio into the programming software, and start decelerating at the corner entry point to achieve stable cutting at the corner.

[0010] As a further aspect of the present invention: In step 1, given the basic conditions of a typical cutting test, K is calculated based on the average cutting forces measured in the X and Y axes of the cutting test.tc K rc K te K re Four cutting force coefficients; K tc K rc These are the cutting force coefficients for the tangential and radial directions, respectively; K te K re These are the cutting force coefficients for the tangential and radial directions, respectively.

[0011] As a further aspect of the present invention: In step 2, the tangential and radial cutting forces are calculated using the established cutting force model at the corner; when milling the corner of the part, the time interval from when the tool enters the corner at one radius to when it exits the corner at one radius is denoted as T, which is called the corner milling time; T is discretized into several time points in units of 0.001s, and the i-th time point is denoted as t. i Calculate the cutting force of the tool at all time points within time T, and take the maximum value as the angular cutting force F. 2，MAX The formulas for the radial and tangential cutting forces at the corner are as follows:

[0012]

[0013] In the above formula, a i Δa represents the radial cutting width at the i-th time point, Δa represents the smallest unit of the depth of cut, which is 0.1 mm; i represents the i-th cutting tooth of the tool; n represents the total number of teeth of the tool; ω represents the angular velocity; δ represents the angle of exit; δ represents the angle of entry.

[0014] F m立 (t i F represents the radial cutting force of the end mill at the i-th time point; n立 (t i () represents the tangential cutting force of the end mill at time point i; β represents the tool helix angle; z represents the axial height of the current infinitesimal element; r is the radius of the tool center trajectory; and the cut-out angle is... It can be expressed by the following formula:

[0015]

[0016] In the above formula, f is the feed rate, r is the radius of the tool center trajectory, θ is the rotation angle, and t1 and t2 can be expressed by the following formula:

[0017]

[0018] In the above formula, θ is the rotation angle, and a c The radial cutting width; the entry angle δ can be expressed by the following formula:

[0019]

[0020] In the above formula, y i Indicates t i At a given time point, the Y-coordinate of the tool center trajectory point; R represents the tool radius; y0 = Ra c .

[0021] As a further aspect of the present invention: in step 2, the maximum cutting force F before the turning angle is calculated. 1,MAX and the maximum cutting force F at the corner 2,MAX ;

[0022] Maximum cutting force F before the turn 1,MAX The expression is:

[0023]

[0024] In the above formula, and These are the maximum cutting forces in the x and y directions, respectively;

[0025] The expression for the maximum cutting force at the corner is:

[0026]

[0027] In the above formula, F m立,MAX F is the maximum radial cutting force of the end mill at the corner. n立,MAX This represents the maximum tangential cutting force of the end mill at the corner.

[0028] As a further aspect of the present invention: in the cutting force model, and With feed per tooth f z The relationship can be expressed by the following formula:

[0029]

[0030] in, and These are the tangential cutting forces in the x and y directions, respectively. and Let be the radial cutting forces in the x and y directions, respectively, and δ be the angle of entry. In climb milling, δ can be expressed as:

[0031] δ=arccos(2a D -1);

[0032] In the above formula, a D The radial depth of cut can be expressed as:

[0033]

[0034] In the above formula, ac Radial cutting depth, where D is the tool diameter.

[0035] As a further aspect of the present invention: in step 3, the expression for the steering angle reduction ratio is:

[0036]

[0037] In the above formula, F 1，MAX F is the maximum cutting force before the turn. 2，MAX This represents the maximum cutting force at the corner.

[0038] An electronic device includes a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that the processor executes the program to implement the steps of the numerical control machining method.

[0039] A computer storage medium storing a computer program thereon, characterized in that the computer program, when executed by a processor, implements the steps of the numerical control machining method.

[0040] Compared with the prior art, the beneficial effects of this application are:

[0041] 1. Based on the classical formulas for calculating cutting force and cutting thickness in milling, a cutting force model at milling corners is established. The relationship between cutting force and time at the milling corner is derived, and the ratio of the cutting force at the milling corner to the cutting force before the corner is calculated as the speed reduction ratio at the milling corner. Applying this method to actual production effectively reduces chatter and tool consolidation during corner machining, ensuring the machining quality of CNC milling corners.

[0042] 2. The corner speed reduction method of this application is not only simple to operate, but also quick and accurate. Compared with traditional methods, it does not rely on the experience of technicians, and scientifically and efficiently calculates the corner speed reduction ratio, effectively reducing the probability of quality problems caused by corner processing of parts and ensuring the product quality of parts.

[0043] The present application will be further described below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0044] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof.

[0045] In the attached diagram:

[0046] Figure 1 A flowchart of the machining method for controlling corner chatter according to the present invention;

[0047] Figure 2 Schematic diagram of the cutting force testing device of the present invention;

[0048] Figure 3 Schematic diagram of corner cutting of the part according to the present invention;

[0049] Figure 4 Schematic diagram of the entry angle and exit angle of this invention;

[0050] Figure 5 The i-th tooth machining milling model of this invention;

[0051] Figure 6 A schematic diagram of the cutting force components at the cutting point of the tool in this invention.

[0052] Numbering explanations in the diagram: 1-Machining tool, 2-Part, 3-Force gauge, 4-Worktable surface, 5-Displacement sensor, 6-Amplifier, 7-Filter, 8-Signal line, 9-Computer, 10-Rotation angle θ, 11-Surface to be machined, 12-Tool tooth tip trajectory circle, 13-Tool center trajectory, 14-Machined surface, 15-Radial cutting width a c 16 - X-axis of coordinate system; 17 - Y-axis of coordinate system; 18 - Infeed portion; 19 - Outfeed portion; 20 - Infeed angle δ; 21 - Outfeed angle 22 - Tool rotation direction, 23 - (i-1)th tooth, 24 - ith tooth, 25 - (i+1)th tooth, 26 - F x For the X-axis cutting force, 27-F y For the Y-axis cutting force, 28-F r Radial cutting force, 29-F t This is the tangential cutting force component. Detailed Implementation

[0053] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0054] In a first aspect, the present invention provides a CNC machining method for controlling angular chatter, comprising the following steps:

[0055] Step 1: Calculate the four cutting force coefficient values;

[0056] Step 2: Apply the corner cutting force model calculation formula to calculate the maximum cutting force at the corner; apply the traditional straight cutting force calculation formula to calculate the maximum cutting force before the corner;

[0057] Step 3: Calculate the ratio of the maximum cutting force before the corner to the maximum cutting force at the corner, and record it as the corner speed reduction ratio;

[0058] Step 4: Input the corner deceleration ratio into the programming software, and start decelerating at the corner entry point to achieve stable cutting at the corner.

[0059] See appendix Figure 1-6 The following detailed description uses a part with a rotation angle as an example. The rotation angle θ is 60°, the machining tool diameter is 16mm, the tool helix angle β is 30°, the feed rate f is 4000mm / min, the spindle speed is 10000r / min, and the radial depth of cut a c The axial cutting depth is 10mm. p The diameter is 2mm, and the radius r of the tool center trajectory is 0.5mm.

[0060] Step 1: Calculate K using a traditional cutting force model. tc K rc K te K re Four cutting force coefficients

[0061] In the design of the basic cutting force experiment, the force gauge 3 is fixed to the worktable 4, and the part 2 is fixed to the force gauge 3 with bolts. The signal measured by the displacement sensor 5 is processed by the amplifier 6, filter 7, etc., and then the collected signal is processed by the signal line 8 and analyzed in the analysis system of the computer 9. Seven groups of feed per tooth are set, the first group f z1 =0.03mm / tooth, Group 2 f z2 =0.06mm / tooth, Group 3 f z3 =0.09mm / tooth, Group 4 f z4 =0.12mm / tooth, Group 5 f z5 =0.15mm / tooth, Group 6 f z6 =0.18mm / tooth, Group 7 f z7 =0.21mm / tooth. Obtain the average cutting force in the x-direction corresponding to these seven sets of cutting parameters. Average cutting force in the y direction

[0062] In the traditional cutting force model and With feed per tooth f z The relationship can be expressed by formula (1):

[0063]

[0064] In formula (1), Here are the expressions for the cutting force components in the x and y directions, respectively, where δ is the angle of entry. In climb milling, δ can be expressed as:

[0065] δ=arccos(2a D -1) (2);

[0066] In formula (2), a D The radial depth of cut can be expressed as:

[0067]

[0068] In formula (3), a c Radial depth of cut, D is the tool diameter; a can be calculated D =0.625.

[0069] a D Substituting 0.625 into formula (2), we obtain δ as 75.5°.

[0070] Seven sets of experimental results were obtained through the experiment. and After obtaining these data and performing regression calculations, K is calculated by substituting the tool geometry parameters and machining parameters. tc 632MPa, K rc 197MPa, K te 2.58×10 3 Pa, K re It is 1.76 × 10 3 Pa.

[0071] Step 2: Calculate the theoretical cutting force of the end mill.

[0072] by Figure 3 Taking the schematic diagram of corner cutting of a part as an example, the corner cutting force model is re-established, and formulas (4) and (5) can be obtained.

[0073] Specifically, the cutting force model at the corner is established to calculate the tangential and radial cutting forces. When milling a part at a corner, the time interval from when the tool enters the corner at one radius to when it exits the corner at one radius is denoted as T, which is called the corner milling time. T is discretized into several time points in units of 0.001s, and the i-th time point is denoted as t. i Calculate the cutting force of the tool at all time points within time T, and take the maximum value as the angular cutting force F. 2，MAX The formulas for the radial and tangential cutting forces at the corner are as follows:

[0074]

[0075] In formulas (4) and (5) above, a iΔa represents the radial cutting width at the i-th time point, Δa represents the smallest unit of the depth of cut, which is 0.1 mm; i represents the i-th cutting tooth of the tool; n represents the total number of teeth of the tool; ω represents the angular velocity; δ represents the angle of entry; F represents the angle of exit; δ represents the angle of entry; m立 (t i F represents the radial cutting force of the end mill at the i-th time point; n立 (t i () represents the tangential cutting force of the end mill at time point i; β represents the tool helix angle; z represents the axial height of the current infinitesimal element; r is the radius of the tool center trajectory. Cut-out angle It can be expressed by the following formula:

[0076]

[0077] In the above formula (6), f is the feed rate, r is the radius of the tool center trajectory, θ is the rotation angle, and t1 and t2 can be expressed by the following formula:

[0078]

[0079] In formulas (7) and (8) above, θ is the rotation angle, and a c The radial cutting width; the entry angle δ can be expressed by the following formula:

[0080]

[0081] In the above formula (9), y i Indicates t i At a given time point, the Y-coordinate of the tool center trajectory point; R represents the tool radius; y0 = Ra c .

[0082] According to the classical formula for calculating cutting force, the tangential and radial cutting forces of the i-th cutting tooth are:

[0083]

[0084] In formula (10), h i Let be the machining thickness of the i-th tooth. According to the classic formula for cutting thickness in milling, we know that:

[0085]

[0086] In formula (11), Δt = 0.001s.

[0087] Substituting the parameters into formulas (7) and (8), we can calculate t1 = 0.24s and t2 = 0.73s.

[0088] K calculated in step 2 tc Krc K te K re Substituting the four cutting force coefficients into formulas (4) and (5), the cutting force at each time point at the corner is calculated. It can be seen that the maximum tangential cutting force at the corner is F. m立,MAX =328N, radial cutting force F n立,MAX =586N.

[0089] Step 3: Calculate the maximum cutting force F before the turning angle. 1,MAX and the maximum cutting force F at the corner 2,MAX ;

[0090] Maximum cutting force F before the turn 1,MAX The expression is:

[0091]

[0092] In the above formula (12), and These are the maximum cutting forces in the x and y directions, respectively;

[0093] The maximum cutting force can be calculated using the following formula:

[0094]

[0095] The expression for the maximum cutting force at the corner is:

[0096]

[0097] In the above formula (14), F m立,MAX F is the maximum radial cutting force of the end mill at the corner. n立,MAX This represents the maximum tangential cutting force of the end mill at the corner.

[0098] The maximum cutting force F before the turning angle is calculated using formulas (1), (12), and (13). 1,MAX The value is 437N, and the F in step 2 is... m立,MAX and F n立,MAX Substituting the calculated value into formula (14), the maximum cutting force F at the corner is calculated. 2,MAX It is 672N.

[0099] Step 4: Calculate the speed reduction ratio by steering angle. The expression for the speed reduction ratio by steering angle is:

[0100]

[0101] According to the above formula (15), the speed reduction ratio at the turning angle is 65%.

[0102] Step 5: Input the corner speed reduction ratio of 65% into the programming software. Start reducing speed at the corner entry point to achieve stable cutting at the corner.

[0103] Practical verification shows that the corner speed reduction method introduced in this paper is not only simple to operate, but also quick and highly accurate. Compared with traditional methods, it does not rely on the experience of technicians, scientifically and efficiently calculates the corner speed reduction ratio, effectively reducing the probability of quality problems caused by corner processing of parts, and ensuring the product quality of parts. Thus, the objective of this invention has been achieved.

[0104] In a second aspect, the present invention provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that the processor executes the program to implement the steps of the numerical control machining method.

[0105] Thirdly, the present invention provides a computer storage medium storing a computer program thereon, characterized in that the computer program, when executed by a processor, implements the steps of the numerical control machining method.

[0106] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A CNC machining method for controlling angular chatter, characterized in that, Includes the following steps: Step 1: Calculate the four cutting force coefficient values; Step 2: Apply the corner cutting force model calculation formula to calculate the maximum cutting force F at the corner. 2，MAX Using the traditional formula for calculating straight cutting force, the maximum cutting force F before the turning angle is calculated. 1，MAX ; Step 3: Calculate the ratio η of the maximum cutting force before the corner and at the corner, and denot it as the corner speed reduction ratio; Step 4: Input the corner deceleration ratio into the programming software, and start decelerating at the corner entry point to achieve stable cutting at the corner; In step 1, given the basic conditions of a typical cutting test, K is calculated based on the average cutting forces measured in the X and Y axes of the cutting test. tc K rc K te K re Four cutting force coefficients; K tc K rc These are the cutting force coefficients for the tangential and radial directions, respectively; K te K re These are the cutting force coefficients for the tangential and radial directions, respectively. In step 2, the tangential and radial cutting forces are calculated using the established cutting force model at the corner. When milling a part at a corner, the time interval from when the tool enters the corner at one radius to when it exits the corner at one radius is denoted as T, which is called the corner milling time. T is discretized into several time points in units of 0.001s, and the i-th time point is denoted as t. i Calculate the cutting force of the tool at all time points within time T, and take the maximum value as the angular cutting force F. 2，MAX The formulas for the radial and tangential cutting forces at the corner are as follows: ； ； In the above formula, a i Δa represents the radial cutting width at the i-th time point, Δa represents the smallest unit of the depth of cut, which is 0.1 mm; i represents the i-th cutting tooth of the tool; n represents the total number of teeth of the tool; ω represents the angular velocity; δ represents the angle of exit; δ represents the angle of entry. F m立 (t i F represents the radial cutting force of the end mill at the i-th time point; n立 (t i () represents the tangential cutting force of the end mill at time point i; β represents the tool helix angle; z represents the axial height of the current infinitesimal element; r is the radius of the tool center trajectory; and the cut-out angle is... It can be expressed by the following formula: ； In the above formula, f is the feed rate, r is the radius of the tool center trajectory, θ is the rotation angle, and t1 and t2 can be expressed by the following formula: ； ； In the above formula, θ is the rotation angle, and a c The radial cutting width; the entry angle δ can be expressed by the following formula: ； In the above formula, y i Indicates t i At a given time point, the Y-coordinate of the tool center trajectory point; R represents the tool radius; y0 = Ra c ; In step 2, the maximum cutting force F before the turning angle is calculated. 1,MAX and the maximum cutting force F at the corner 2,MAX ; Maximum cutting force F before the turn 1,MAX The expression is: ； In the above formula, and These are the maximum cutting forces in the x and y directions, respectively; The expression for the maximum cutting force at the corner is: ； In the above formula, F m立,MAX F is the maximum radial cutting force of the end mill at the corner. n立,MAX This represents the maximum tangential cutting force of the end mill at the corner.

2. The CNC machining method for controlling angular chatter according to claim 1, characterized in that, In the cutting force model, and With feed per tooth f z The relationship can be expressed by the following formula: ； in, and These are the tangential cutting forces in the x and y directions, respectively. and Let be the radial cutting forces in the x and y directions, respectively, and δ be the angle of entry. In climb milling, δ can be expressed as: ； In the above formula, a D The radial depth of cut can be expressed as: ； In the above formula, a c Radial cutting depth, where D is the tool diameter.

3. The CNC machining method for controlling angular chatter according to claim 2, characterized in that, In step 3, the expression for the steering angle reduction ratio is: ； In the above formula, F 1，MAX F is the maximum cutting force before the turn. 2，MAX This represents the maximum cutting force at the corner.

4. An electronic device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the program, it implements the steps of the CNC machining method as described in any one of claims 1-3.

5. A computer storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the steps of the CNC machining method as described in any one of claims 1-3.

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