Milling cutter relieving deformation control method for thin-wall double-lug butt joint structure

Abstract

According to the milling cutter relieving deformation control method for the thin-wall double-lug butt joint structure, the rough machining process allowance is reasonably distributed, the finish machining cutter path is dynamically adjusted, cutting deformation of the thin-wall double lugs is controlled, and the machining precision of the thin-wall double-lug butt joint structure is improved. Comprising the steps of rough machining of the inner and outer sides of the cantilever, finish machining of the inner side of the cantilever and finish machining of the outer side of the cantilever. According to the method, the problems that the thin-wall double-lug butt joint structure parts are prone to chattering and poor in surface quality in the numerical control machining process can be effectively solved, the part machining precision is obviously improved, and the overall quality of the thin-wall double-lug butt joint parts such as aircraft sliding rails and pulley yokes is improved.

Description

Technical Field

[0001] This invention belongs to the field of CNC machining technology, and particularly relates to a method for controlling the deformation of the milling tool in a thin-walled double-ear butt joint structure. Background Technology

[0002] Thin-walled double-eared structures are a typical feature of aerospace structural components, commonly found in important parts such as slide rails and pulley frames. These parts are required to possess excellent properties such as high precision, high load capacity, and wear resistance. Among commonly used metallic materials, titanium alloys have a density of approximately 4.4 g / m³. 3 With an elastic modulus of approximately 110-120 GPa and a tensile strength of approximately 300-600 MPa, it is both lightweight and high-strength, making it highly suitable for machining such critical parts. However, due to the special design requirements, such as the high demands on the dimensional accuracy and perpendicularity of the holes on the lugs, the dimensional tolerances of the slot width, and the thickness tolerances of the lugs, the parts present technical challenges in terms of machining difficulty and high precision. During machining, phenomena such as tool deflection and chatter can easily occur, leading to product defects.

[0003] Generally speaking, when processing thin-walled double-eared structures using traditional methods, technicians rely on past experience to provide processing parameters. However, the product quality is not ideal, requiring subsequent repairs by operators. Traditional methods rely too much on experience and fail to analyze the deformation mechanism or quantitatively calculate processing parameters. This makes it difficult to control the deformation of the milling tool, resulting in a low part qualification rate. Summary of the Invention

[0004] To address the problem that existing technologies rely on empirical values ​​when machining thin-walled double-ear structures, failing to analyze deformation mechanisms and quantitatively calculate machining parameters, resulting in low part yield, this invention provides a method for controlling tool deformation during milling of thin-walled double-ear butt joint structures. The technical solution is as follows: A method for controlling the cutting deformation of a thin-walled double-eared butt joint structure during milling is proposed. This method involves rationally allocating the roughing allowance and dynamically adjusting the finishing tool path to control the cutting deformation of the thin-walled double-eared structure. The method includes roughing the inner and outer sides of the cantilever, finishing the inner side of the cantilever, and finishing the outer side of the cantilever.

[0005] Optionally, rough machining is performed on the inner and outer sides of the cantilever, specifically including: Step 1: Based on the single cantilever structure, the roughing thin-walled double-ear structure is simplified to a roughing single cantilever structure. According to the cutting force model and structural deformation model, the calculation formula for the theoretical tool deflection is obtained, and the target tool deflection δ is set. 目标 For the theoretical tool deflection δ 理论 Calculate the target deflection amount δ 目标 The rough machining allowance is allocated unequally to the inner and outer sides of the cantilever using a 1:3 ratio.

[0006] Optionally, step 1 specifically includes: 1-1. Compare the values ​​of 1 / 5 of the ear plate wall thickness tolerance and 1 / 5 of the double ear plate groove tolerance, and take the minimum value as the target deflection amount δ. 目标 Set the target deflection amount δ 目标 For the theoretical tool deflection δ 理论 Based on the theoretical deflection formula, parameters such as radial cutting force coefficient, cutting depth, feed per tooth, cantilever length, width, and material elastic modulus are substituted into the theoretical deflection formula to deduce the thickness of the vertical rib when milling the inner side of the cantilever, and the roughing allowance is calculated.

[0007] The theoretical formula for calculating the tool deflection amount during rough machining of a single cantilever structure is as follows: (1) In formula (1), δ 理论 The theoretical tool deflection is expressed in mm; K r This is the radial cutting force coefficient, with units of N / mm. 2 Related to materials and cutting tools; a p f represents the axial cutting depth in mm. z The feed per tooth is in mm / z; L is the length of the vertical rib in mm; E is the material's elastic modulus in N / mm². 2 b is the width of the vertical reinforcement bar in mm; h is the thickness of the vertical reinforcement bar in mm. 1-2. Assuming that the milling deformation on the outer side is not considered, the inner and outer sides are allocated unequal allowances with a ratio of 1:3.

[0008] Optionally, the inner side of the cantilever is precision machined, specifically including: Step 2: Based on the target deflection amount, perform variable depth machining on the inner side of the ear piece using side milling. Utilize a dynamic compensation strategy to design a finishing machining scheme for the inner side of the ear piece: determine the machining tool diameter, and based on the theoretical deflection amount δ... 理论 With variable shear depth a p The formula for calculating (x) is used to set the target deflection amount δ. 目标 For the theoretical tool deflection δ 理论 Based on the target tool deflection δ 目标 It plans the variable depth of cut for different machining positions and generates specific paths based on the planned tool diameter and variable depth of cut.

[0009] Optionally, step 2 specifically includes: 2-1. Determine the diameter of the tool for finishing the inner side of the ear piece: Select a tool with the largest possible diameter while ensuring that it is smaller than the groove width; 2-2. Calculate the variable depth of cut based on the target deflection amount; 2-3. Determine the side milling toolpath based on the variable depth of cut.

[0010] Optionally, 2-2, calculate the variable depth of cut a based on the target deflection amount. p (x), specifically including: According to the theoretical tool deflection δ 理论 With variable shear depth a p The formula for calculating (x) is used to set the target deflection amount δ. 目标 For the theoretical tool deflection δ 理论 It can be seen that the target yield amount δ 目标 With variable shear depth a p The formula for calculating (x) is: (2) in, , , , h(x) is the local wall thickness that varies with the processing position, b is the rib height and width in mm, and a e The radial cutting width is in mm, z represents the effective number of cutting teeth, θ is the angle between the tool clearance angle and the cutting plane, N represents the total number of tool teeth, D is the tool diameter in mm, and I(x) represents the moment of inertia of the cross section as the machining position changes in mm. 4 .

[0011] Optionally, the outer side of the cantilever may be finished, specifically including: Step 3: Based on the target deflection amount, perform variable width finishing on the outer side of the lug using end milling. Establish a dynamic variation model of the variable width and axial cutting force to ensure that the theoretical deflection amount δ is within the entire machining process. 理论 ≤Target tool deflection δ 目标 . Optionally, step 3 specifically includes: 3-1. When finishing the outer side of the ear piece, the finishing structure of the thin-walled double ear piece is simplified to the finishing structure of the single cantilever, and the axial cutting force F is obtained. f With theoretical deflection δ 理论 Relationship: Take 1 / 5 of the ear plate wall thickness tolerance as the target deflection amount δ 目标 Based on δ 理论 ≤δ 目标 Calculate the theoretical deflection amount δ 理论 With axial cutting force F f The relationship is shown in formula (3): (3) k r The principal cutting edge angle of the tool is expressed in degrees. 3-2, Based on δ 理论≤δ 目标 Given the condition, the target deflection amount δ is obtained. 目标 With axial cutting force F f The relationship is shown in formula (4): (4) 3-3, by axial cutting force F f With theoretical deflection δ 理论 Relationship between axial cutting force F f The relationship between the cutting parameters and the cutting depth h(x) and the variable cutting width a is derived. e The relation for (x): From formula (4), it can be seen that when controlling the deflection amount, the axial cutting force F f The maximum value is: (5) The relationship between axial cutting force and cutting parameters is as follows: (6) K f This is the axial cutting force coefficient, in N / mm. 2 From formulas (5) and (6), the variable cutting width a under different cutting depths h(x) is obtained. e The relationship between (x) is shown in formulas (7) and (8). Formula (7) is applicable when the variable shear width a e When (x)≤0.3D, formula (8) applies when the variable shear width a e The case where (x) > 0.3D: (7) ; (8) 3-4. Determine the end milling cutter path with variable cut width: Based on the planned target deflection δ 目标 Design different cutting depths h(x) and variable cutting width a e (x) generates the specific path.

[0012] The beneficial effects of this application are as follows: The milling tool deformation control method for thin-walled double-eared mating structures provided in this invention can effectively solve the problems of easy vibration and poor surface quality of thin-walled double-eared mating structure parts during CNC machining, significantly improve the machining accuracy of parts, and ensure the overall quality of thin-walled double-eared mating parts such as aircraft slide rails and pulley frames. Attached Figure Description

[0013] Figure 1 A schematic diagram of the thin-walled double-eared mating structure of the part; Figure 2 A schematic diagram showing the precision machining of the inner side of the cantilever. Figure 3 Schematic diagram of the finish machining of the outer side of the cantilever; Figure 4 For the processing flow chart; Wherein: 1-Titanium alloy thin-walled double ear structure, 2-Inner side of ear, 3-Outer side of ear, 4-Machining tool, 5-Part itself. Detailed Implementation

[0014] This invention calculates the cutting force, allocates the process allowance on the inner and outer sides of the lugs, and designs a reasonable deformation control method, which is a method to control the deformation of the cutting tool when milling a thin-walled double lug butt structure.

[0015] The deformation control method provided in this invention can predict the amount of deformation and dynamically adjust the tool path and process parameters. It is highly accurate and efficient, and is suitable for machining complex thin-walled structures in aerospace, precision instruments and other fields.

[0016] This invention provides a method for controlling the milling tool deformation of a thin-walled double-ear butt joint structure. By predicting the deformation amount and dynamically adjusting the tool path and process parameters, the cutting deformation of the thin-walled double-ear is controlled. This includes roughing the inner and outer sides of the cantilever, finishing the inner side of the cantilever, and finishing the outer side of the cantilever. (See...) Figure 4 .

[0017] For example, see Figure 1 1. Titanium alloy thin-walled double-ear structure, with an ear length L of 80mm, a width b of 60mm, an ear thickness t of 10±0.1mm, an ear groove width of 25(+0.2 / 0)mm, and a cutting depth a. p The feed per tooth is 1.5mm, f z The value is 0.1 mm / z, the elastic modulus E is 110 GPa, and the radial cutting force coefficient k r 1800 N / mm 2 axial cutting force coefficient k f 800 N / mm 2 .

[0018] Step 1: Calculate the rough machining allowance.

[0019] The theoretical deflection is taken as 1 / 5 of the tolerance, which is 0.02mm. The typical calculation formula for the theoretical deflection is as follows:

[0020] The theoretical deflection amount, cutting force coefficient, axial depth of cut, feed rate, cantilever height, length, and material elastic modulus are substituted into the calculation formula.

[0021] It can be determined that t is 13.8mm, with a margin of 11.8mm, which is distributed to the inner and outer sides of the ear piece, at 3mm and 9mm respectively.

[0022] Step 2: See Figure 2 Based on the target yield control, the inner side of the ear piece is milled using a side milling method with variable cutting depth 2, generating a specific tool path. Figure 2 In this context, 4 represents the machining tool, and 5 represents the part itself.

[0023] As learned from step 1, a roughing allowance of 3mm is left on the inner side of the ear piece. A solid carbide end mill with a D=16mm diameter and 4 teeth (z=4) is selected. The inner side of the ear piece is then subjected to variable depth finishing milling using a side milling method to achieve the desired δ... 目标 =0.02mm, and calculated by formulas (5) and (7), the effective number of cutting teeth z is 0.12.

[0024]

[0025] C1 is expressed as follows:

[0026] Substituting various processing parameters into the above formula, we obtain C1=0.0028, and thus the variable cutting depth a. p The calculated value of (x) is as follows:

[0027] Step 3: See Figure 3 Based on the target yield control, the outer side of the ear piece is finished by end milling with variable cutting width.

[0028]

[0029]

[0030] Where D=16mm, δ 目标 =0.02mm, E=110GPa, b=2mm, tank r =1.73, L=80mm, k f =800N / mm 2 Precision cutting depth a p =0.5mm, f z =0.1mm / z, N=4, C2=0.078 can be calculated. The variable cutting depth a is then obtained. e The calculated value of (x) is as follows:

[0031] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A method for controlling the deformation of the milling tool in a thin-walled double-ear butt joint structure, characterized in that, By rationally allocating the roughing allowance and dynamically adjusting the finishing tool path, the cutting deformation of the thin-walled double lugs can be controlled, including roughing the inner and outer sides of the cantilever, finishing the inner side of the cantilever, and finishing the outer side of the cantilever.

2. The method according to claim 1, characterized in that, Rough machining is performed on the inner and outer sides of the cantilever, specifically including: Step 1: Based on the single cantilever structure, the roughing thin-walled double-ear structure is simplified to a roughing single cantilever structure. According to the cutting force model and structural deformation model, the calculation formula for the theoretical tool deflection is obtained, and the target tool deflection δ is set. 目标 For the theoretical tool deflection δ 理论 Calculate the target deflection amount δ 目标 The rough machining allowance is allocated unequally to the inner and outer sides of the cantilever using a 1:3 ratio.

3. The method according to claim 2, characterized in that, Step 1 specifically includes: 1-1. Compare the values ​​of 1 / 5 of the ear plate wall thickness tolerance and 1 / 5 of the double ear plate groove tolerance, and take the minimum value as the target deflection amount δ. 目标 Set the target deflection amount δ 目标 For the theoretical tool deflection δ 理论 Based on the theoretical deflection formula, parameters such as radial cutting force coefficient, cutting depth, feed per tooth, cantilever length, width, and material elastic modulus are substituted into the theoretical deflection formula to deduce the thickness of the vertical rib when milling the inner side of the cantilever, and the roughing allowance is calculated.

4. The formula for calculating the theoretical tool deflection during rough machining of a single cantilever structure is: (1) in, δ 理论 The theoretical tool deflection is expressed in mm; K r This is the radial cutting force coefficient, with units of N / mm. 2 Related to materials and cutting tools; a p f represents the axial cutting depth in mm. z The feed per tooth is in mm / z; L is the length of the vertical rib in mm; E is the material's elastic modulus in N / mm². 2 b is the width of the vertical reinforcement bar in mm; h is the thickness of the vertical reinforcement bar in mm. 1-2. Assuming that the milling deformation on the outer side is not considered, the inner and outer sides are allocated unequal allowances with a ratio of 1:

3.

5. The method according to claim 1, characterized in that, The inner side of the cantilever undergoes finishing, specifically including: Step 2: Based on the target deflection amount, perform variable depth machining on the inner side of the ear piece using side milling. Utilize a dynamic compensation strategy to design a finishing machining scheme for the inner side of the ear piece: determine the machining tool diameter, and based on the theoretical deflection amount δ... 理论 With variable shear depth a p The formula for calculating (x) is used to set the target deflection amount δ. 目标 For the theoretical tool deflection δ 理论 Based on the target tool deflection δ 目标 It plans the variable depth of cut for different machining positions and generates specific paths based on the planned tool diameter and variable depth of cut.

6. The method according to claim 4, characterized in that, Step 2 specifically includes: 2-1. Determine the diameter of the tool for finishing the inner side of the ear piece: Select a tool with the largest possible diameter while ensuring that it is smaller than the groove width; 2-2. Calculate the variable depth of cut based on the target deflection amount; 2-3. Determine the side milling toolpath based on the variable depth of cut.

7. The method according to claim 5, characterized in that, 2-2. Calculate the variable depth of cut a based on the target deflection amount. p (x), specifically including: According to the theoretical tool deflection δ 理论 With variable shear depth a p The formula for calculating (x) is used to set the target deflection amount δ. 目标 For the theoretical tool deflection δ 理论 Target yield δ 目标 With variable shear depth a p The formula for calculating (x) is: (2) in, , , , h(x) is the local wall thickness that varies with the processing position, b is the rib height and width in mm, and a e The radial cutting width is in mm, z represents the effective number of cutting teeth, θ is the angle between the tool clearance angle and the cutting plane, N represents the total number of tool teeth, D is the tool diameter in mm, and I(x) represents the moment of inertia of the cross section as the machining position changes in mm. 4 .

8. The method according to claim 1, characterized in that, The outer side of the cantilever undergoes finishing, specifically including: Step 3: Based on the target deflection amount, perform variable width finishing on the outer side of the lug using end milling. Establish a dynamic variation model of the variable width and axial cutting force to ensure that the theoretical deflection amount δ is within the entire machining process. 理论 ≤Target tool deflection δ 目标。 9. The method according to claim 7, characterized in that, Step 3 specifically includes: 3-1. When finishing the outer side of the ear piece, the finishing structure of the thin-walled double ear piece is simplified to the finishing structure of the single cantilever, and the axial cutting force F is obtained. f With theoretical deflection δ 理论 Relationship: Take 1 / 5 of the ear plate wall thickness tolerance as the target deflection amount δ 目标 Based on δ 理论 ≤δ 目标 Calculate the theoretical deflection amount δ 理论 With axial cutting force F f The relationship is shown in formula (3): (3) Where, k r The principal cutting edge angle of the tool is expressed in degrees. 3-2, Based on δ 理论 ≤δ 目标 Given the condition, the target deflection amount δ is obtained. 目标 With axial cutting force F f The relationship is shown in formula (4): (4) 3-3, by axial cutting force F f With theoretical deflection δ 理论 Relationship between axial cutting force F f The relationship between the cutting parameters and the cutting depth h(x) and the variable cutting width a is derived. e The relation for (x): From formula (4), it can be seen that when controlling the deflection amount, the axial cutting force F f The maximum value is: (5) The relationship between axial cutting force and cutting parameters is as follows: (6) Among them, K f This is the axial cutting force coefficient, in N / mm. 2 From formulas (5) and (6), the variable cutting width a under different cutting depths h(x) is obtained. e The relationship between (x) is shown in formulas (7) and (8). Formula (7) is applicable when the variable shear width a e When (x)≤0.3D, formula (8) applies when the variable shear width a e In the case where (x) > 0.3D, (7) in, ; (8) 3-4. Determine the end milling cutter path with variable cut width: Based on the planned target deflection δ 目标 Design different cutting depths h(x) and variable cutting width a e (x) generates the specific path.

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