Numerical control machining method for controlling corner chattering

Abstract

The invention belongs to the technical field of aircraft manufacturing, and discloses a numerical control machining method for controlling corner chattering, which comprises the following steps of: establishing a cutting force model at a milling corner based on a cutting force classic calculation formula and a milling machining cutting thickness classic formula, and deducing a relational expression between the cutting force at the milling corner and time; and calculating the ratio of the cutting force at the milling corner to the cutting force before the milling corner, and taking the ratio as the speed reduction ratio of the milling corner. The technical problems that fluttering and tool nesting phenomena are prone to being generated in the corner machining process are solved. Compared with a traditional method, the method does not depend on experience of technicians, the corner speed reduction ratio is scientifically and efficiently calculated, and the probability that quality problems occur to parts due to corner machining is effectively reduced.

Description

Technical Field

[0001] The invention belongs to the field of aircraft manufacturing-CNC machining technology, and specifically relates to a CNC machining method for controlling corner vibration. Background Art

[0002] Corner is one of the typical part features in CNC machining, which is commonly found in structural parts such as frames, beams, ribs, joints and partitions. At the corners of machined parts, the cutting area and contact area between the tool and the part increase sharply, causing violent fluctuations in the cutting force, which is very likely to cause the "tool nesting" phenomenon, resulting in a decrease in the machining quality at the corners, and even cutting the inner wall of the part and damaging the tool. For corner machining, the traditional treatment method is to reduce the cutting width and cutting depth of the tool, increase the corner radius, and reduce the corner feed speed. However, this method mostly relies on the programming experience of the process personnel, puts forward high requirements on the technical level, and can only reduce the occurrence of some "tool nesting" phenomena. In summary, it is necessary to conduct a detailed study on the tool cutting force during corner machining, and optimize the process programming strategy accordingly to ensure the machining quality of the part corners. Summary of the invention

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

[0004] In order to achieve the above invention objectives, the technical solutions adopted in this application are as follows:

[0005] A numerical control machining method for controlling corner vibration comprises the following steps:

[0006] Step 1: Calculate the values ​​of the four cutting force coefficients;

[0007] Step 2: Apply the corner cutting force model calculation formula to calculate the maximum cutting force F at the corner 2，MAX ; Apply the traditional linear cutting force calculation formula to calculate the maximum cutting force F before the corner 1，MAX ;

[0008] Step 3: Calculate the ratio of the maximum cutting force before the corner to the maximum cutting force at the corner, η, which is recorded as the corner speed reduction ratio;

[0009] Step 4: Input the corner speed reduction ratio into the programming software, start speed reduction at the entry point of the corner, and achieve stable cutting at the corner.

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

[0011] As a further solution of the present invention: in step 2, the tangential and radial cutting forces are calculated by the established cutting force model at the corner; when milling a corner of a part, the time period from the tool entering the corner by one radius to exiting the corner by one radius is recorded as T, which is called the corner milling time; T is discretized into a number of time points in units of 0.001s, and the i-th time point is recorded as t i , calculate the cutting force corresponding to the tool at all time points within T, and take the maximum value as the corner cutting force F 2，MAX ; The formulas for radial and tangential cutting forces at the corners are as follows:

[0012]

[0013] In the above formula, a i represents the radial cutting width at the i-th time point, Δa represents the minimum unit of cutting depth, 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; represents the cut-out angle; δ represents the cut-in angle;

[0014] F m立 (t i ) represents the radial cutting force of the end mill at the i-th time point; F n立 (t i ) represents the tangential cutting force of the end mill at the i-th time point; β represents the tool helix angle; z represents the axial height of the current microelement; r is the radius of the tool center trajectory; the cutting angle 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, a c is the radial cutting width; the cutting angle δ can be expressed by the following formula:

[0019]

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

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

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

[0023]

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

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

[0026]

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

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

[0029]

[0030] in, and are the tangential cutting forces in the x-direction and y-direction, respectively. and are the radial cutting forces in the x-direction and y-direction respectively, δ is the cutting angle, and when milling down, δ can be expressed as:

[0031] δ = arccos(2a D -1);

[0032] In the above formula, a D is the radial cutting depth rate, which can be expressed as:

[0033]

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

[0035] As a further solution of the present invention: in step 3, the expression of the corner speed reduction ratio is:

[0036]

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

[0038] An electronic device comprises a memory, a processor and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the numerical control machining method when executing the program.

[0039] A computer storage medium stores a computer program, wherein the computer program implements the steps of the numerical control machining method when executed by a processor.

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

[0041] 1. Based on the classic calculation formula of cutting force and the classic formula of cutting thickness in milling, the 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 ratio of the cutting force at the milling corner to the cutting force before the milling corner is calculated as the speed reduction ratio of the milling corner. This method is applied in actual production to effectively reduce the "chatter" and "tool nest" generated during the corner processing process, and ensure the processing quality of CNC milling corners.

[0042] 2. The corner speed reduction method of this application is not only simple to operate, but also short in time 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 reduces the probability of quality problems of parts due to corner processing, and ensures the product quality of parts.

[0043] The present application is further described below in conjunction with the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The accompanying drawings are used to provide further understanding of the present invention and constitute a part of the specification. They are used to explain the present invention together with the embodiments of the present invention and do not constitute a limitation of the present invention.

[0045] In the attached picture:

[0046] Figure 1 A flow chart of a processing method for controlling corner vibration of the present invention;

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

[0048] Figure 3 Schematic diagram of corner cutting of parts of the present invention;

[0049] Figure 4 Schematic diagram of the cut-in angle and cut-out angle of the present invention;

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

[0051] Figure 6 Schematic diagram of the cutting force components at the cutting point of the tool of the present invention.

[0052] Explanation of numbers in the figure: 1-processing tool, 2-part, 3-dynamometer, 4-working table, 5-displacement sensor, 6-amplifier, 7-filter, 8-signal line, 9-computer, 10-rotation angle θ, 11-surface to be processed, 12-tool tooth tip trajectory circle, 13-tool center trajectory, 14-processed surface, 15-radial cutting width a c , 16- coordinate system X axis, 17- coordinate system Y axis, 18- cut-in part, 19- cut-out part, 20- cut-in angle δ, 21- cut-out angle 22-tool rotation direction, 23-i-1th tooth, 24-ith tooth, 25-i+1th tooth, 26-F x is the X-axis cutting force, 27-F y Y-axis cutting force, 28-F r is the radial cutting force, 29-F t It is the tangential cutting force. DETAILED DESCRIPTION

[0053] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments; based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work 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 corner vibration, which comprises the following steps:

[0055] Step 1: Calculate the values ​​of the four cutting force coefficients;

[0056] Step 2: Apply the corner cutting force model calculation formula to calculate the maximum cutting force at the corner; apply the traditional straight line 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 and at the corner, and record it as the corner speed reduction ratio;

[0058] Step 4: Input the corner speed reduction ratio into the programming software, start speed reduction at the entry point of the corner, and achieve stable cutting at the corner.

[0059] See attached Figure 1-6 The following is a detailed description of a part with a corner to be processed. The corner θ is 60°, the processing tool diameter is 16mm, the tool helix angle β is 30°, the feed speed f is 4000mm / min, the rotation speed is 10000r / min, and the radial cutting depth a is c The axial cutting depth is 10 mm. p The tool center trajectory radius r is 2mm and 0.5mm.

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

[0061] Design a basic cutting force experiment, fix the dynamometer 3 on the work surface 4, and fix the part 2 on the dynamometer 3 with bolts. The signal measured by the displacement sensor 5 is processed by the amplifier 6, filter 7, etc., and the collected signal is processed and analyzed in the analysis system of the computer 9 after passing through the signal line 8. Set 7 groups of feed per tooth, the first group f z1 =0.03mm / tooth, 2nd group f z2 =0.06mm / tooth, 3rd group f z3 =0.09mm / tooth, 4th group f z4 =0.12mm / tooth, 5th group f z5 =0.15mm / tooth, 6th group f z6 =0.18mm / tooth, 7th group f z7 =0.21mm / tooth. Obtain the average cutting force in the x direction corresponding to the seven sets of cutting parameters respectively Average cutting force in y direction

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

[0063]

[0064] In formula (1), They are the cutting force component expressions in the x-direction and y-direction respectively, δ is the cutting angle, and when milling down, δ can be expressed as:

[0065] δ = arccos(2a D -1) (2);

[0066] In formula (2), a D is the radial cutting depth rate, which can be expressed as:

[0067]

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

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

[0070] Through the experiment, 7 groups of tests were obtained. and After the obtained data are subjected to regression calculation, K is calculated by substituting the tool geometry parameters and processing parameters. tc 632MPa, K rc 197MPa, K te 2.58×10 3 Pa, K re 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 parts as an example, the corner cutting force model is re-established, and formulas (4) and (5) can be obtained.

[0073] Specifically, the tangential and radial cutting forces are calculated by establishing a cutting force model at the corner. When milling a corner, the time period from the tool entering the corner by one radius to exiting the corner by one radius is recorded 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 recorded as t i , calculate the cutting force corresponding to the tool at all time points within T, and take the maximum value as the corner cutting force F 2，MAX ; The formulas for radial and tangential cutting forces at the corners are as follows:

[0074]

[0075] In the above formulas (4) and (5), a irepresents the radial cutting width at the i-th time point, Δa represents the minimum unit of cutting depth, 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; represents the cut-out angle; δ is the cut-in angle; F m立 (t i ) represents the radial cutting force of the end mill at the i-th time point; F n立 (t i ) represents the tangential cutting force of the end mill at the i-th time point; β represents the tool helix angle; z represents the axial height of the current microelement; and r is the radius of the tool center trajectory. 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 the above formulas (7) and (8), θ is the rotation angle, a c is the radial cutting width; the cutting angle δ can be expressed by the following formula:

[0080]

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

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

[0083]

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

[0085]

[0086] In formula (11), Δt=0.001s.

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

[0088] The K calculated in step 2 tc , Krc , K te , K re After 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 corner 1,MAX and the maximum cutting force F at the corner 2,MAX ;

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

[0091]

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

[0093] Among them, the maximum cutting force can be calculated using the following formula:

[0094]

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

[0096]

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

[0098] According to formula (1), formula (12) and formula (13), the maximum cutting force F before the corner is calculated: 1,MAX =437N, replace F in step 2 m立,MAX and F n立,MAX Substitute the calculated value into formula (14) to calculate the maximum cutting force F at the corner 2,MAX It is 672N.

[0099] Step 4: Calculate the corner speed reduction ratio. The corner speed reduction ratio expression is:

[0100]

[0101] According to the above formula (15), the corner speed reduction ratio is obtained to be 65%.

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

[0103] Through actual verification, it can be seen that the corner speed reduction method introduced in this article is not only simple to operate, but also short in time and highly accurate. Compared with the traditional method, it does not rely on the experience of technicians, scientifically and efficiently calculates the corner speed reduction ratio, effectively reduces the probability of quality problems of parts due to corner processing, and ensures the product quality of parts. So far, the purpose of the present invention has been achieved.

[0104] In a second aspect, the present invention provides an electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the CNC machining method when executing the program.

[0105] In a third aspect, the present invention provides a computer storage medium having a computer program stored thereon, characterized in that the computer program implements the steps of the CNC machining method when executed by a processor.

[0106] The above are only 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 in the protection scope of the present invention.

Claims

1. A CNC machining method for controlling corner vibration, characterized in that: The steps include: Step 1: Calculate the values ​​of the four cutting force coefficients; Step 2: Apply the corner cutting force model calculation formula to calculate the maximum cutting force F at the corner 2，MAX ; Apply the traditional linear cutting force calculation formula to calculate the maximum cutting force F before the corner 1，MAX ; Step 3: Calculate the ratio of the maximum cutting force before the corner to the maximum cutting force at the corner, η, which is recorded as the corner speed reduction ratio; Step 4: Input the corner speed reduction ratio into the programming software, start speed reduction at the entry point of the corner, and achieve stable cutting at the corner.

2. A CNC machining method for controlling rotation angle vibration according to claim 1, characterized in that: In step 1, the basic conditions of the typical cutting test are known, and K is calculated based on the average cutting forces in the X-axis and Y-axis directions measured in the cutting test. tc , K rc , K te , K re Four cutting force coefficients; K tc , K rc are the tangential and radial cutting force coefficients respectively; K te , K re are the tangential and radial cutting force coefficients respectively.

3. A CNC machining method for controlling rotation angle vibration according to claim 1, characterized in that: In step 2, the tangential and radial cutting forces are calculated by the established cutting force model at the corner. When milling a corner of a part, the time period from the tool entering the corner by one radius to exiting the corner by one radius is recorded 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 recorded as t i , calculate the cutting force corresponding to the tool at all time points within T, and take the maximum value as the corner cutting force F 2，MAX ; The formulas for radial and tangential cutting forces at the corners are as follows: In the above formula, a i represents the radial cutting width at the i-th time point, Δa represents the minimum unit of cutting depth, 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; Indicates the cut-out angle; δ is the cutting angle; F m立 (t i ) represents the radial cutting force of the end mill at the i-th time point; F n立 (t i ) represents the tangential cutting force of the end mill at the i-th time point; β represents the tool helix angle; z represents the axial height of the current microelement; r is the radius of the tool center trajectory; the cutting angle 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, a c is the radial cutting width; the cutting angle δ can be expressed by the following formula: In the above formula, y i Indicates t i At the time point, the Y coordinate value of the tool center trajectory point; R represents the tool radius; y0 = Ra c .

4. A CNC machining method for controlling rotation angle vibration according to claim 3, characterized in that: In step 2, the maximum cutting force F before the corner is calculated 1,MAX and the maximum cutting force F at the corner 2,MAX ; Maximum cutting force before cornering F 1,MAX The expression is: In the above formula, and are the maximum cutting forces in the x and y directions respectively; The maximum cutting force expression at the corner is: In the above formula, F m立,MAX is the maximum radial cutting force of the end mill at the corner, F n立,MAX It is the maximum tangential cutting force of the end mill at the corner.

5. A CNC machining method for controlling rotation angle vibration according to claim 4, characterized in that: In the cutting force model, and And the feed per tooth f z The relationship can be expressed by the following formula: in, and are the tangential cutting forces in the x-direction and y-direction, and are the radial cutting forces in the x-direction and y-direction respectively, δ is the cutting angle, and when milling down, δ can be expressed as: δ=arccos(2a D -1); In the above formula, a D is the radial cutting depth rate, which can be expressed as: In the above formula, a c Radial cutting depth, D is the tool diameter.

6. A CNC machining method for controlling rotation angle vibration according to claim 5, characterized in that: In step 3, the corner speed reduction ratio expression is: In the above formula, F 1，MAX is the maximum cutting force before the corner, F 2，MAX is the maximum cutting force at the corner.

7. 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, the steps of the numerical control machining method according to any one of claims 1 to 6 are implemented.

8. A computer storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the numerical control machining method according to any one of claims 1 to 6 are implemented.

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