Method for predicting cutting force of composite titanium laminated hole making of automatic equipment

Abstract

The invention relates to the field of aircraft assembling and manufacturing, in particular to a method for predicting cutting force of automatic equipment composite titanium lamination drilling. According to the method, an axial drilling force theoretical model is established according to different drilling stages by analyzing the complex titanium lamination drilling process of automatic equipment. And according to the theoretical model, a C language is applied to develop process guidance software. Cutter parameters and cutting parameters are input into software, the predicted axial drilling force can be output, and guidance is provided for selection of the cutter and the cutting parameters. And through the cutting force prediction model and process guidance software, the axial drilling force of the composite titanium laminated drilling tool can be predicted, and then the drilling quality of the tool is predicted. The tool testing cost is effectively reduced, and the model selection efficiency of the composite titanium laminated hole making tool is improved.

Description

Technical Field

[0001] The present invention relates to the field of aircraft assembly manufacturing, and particularly relates to a method for predicting the cutting force of automated equipment for drilling through titanium composite laminates. Background Art

[0002] Due to the characteristics of carbon fiber composite materials being lightweight and high-strength, and titanium alloy materials being high-hardness and high-temperature resistant, carbon fiber composite materials and titanium alloy materials are often widely selected in the aircraft product design stage. Therefore, during the aircraft product assembly process, a large number of working conditions of drilling through titanium composite laminates will inevitably occur.

[0003] Carbon fiber composite materials are typical anisotropic materials. During the hole machining process, defects such as tearing, delamination, and burrs are extremely likely to occur; titanium alloys have large cutting forces and high cutting temperatures during drilling, and chip entanglement and built-up edge are relatively easy to occur. Both carbon fiber composite materials and titanium alloys are typical difficult-to-machine materials.

[0004] For the working conditions of drilling through titanium composite laminates, the traditional manual drilling method is generally adopted: workers use the traditional drilling - reaming - boring process method to gradually complete the drilling of laminates. The above method has low drilling efficiency, requires more tools, the drilling quality is not stable enough, and the labor intensity of workers is relatively large. There is an urgent need to adopt a new process method with high efficiency and high precision to replace this drilling method.

[0005] In order to improve the aircraft product assembly efficiency and achieve the goal of digital and intelligent aircraft product assembly, a large number of automated equipment have been introduced in the aircraft assembly production line. Compared with traditional manual drilling, automated equipment drilling has the advantages of high drilling efficiency, stable drilling quality, and low labor intensity. However, the processing problems of drilling through titanium composite laminates still exist during the automated equipment drilling process. And when using the traditional drilling - reaming - boring process method for traditional manual drilling through titanium composite laminates, more tools are required and it takes a long time. To improve the processing efficiency, it is generally required that the automated equipment makes the final hole in one cut, which puts higher requirements on the automated drilling tools and process methods.

[0006] Currently, for the working conditions of drilling through titanium composite laminates in the open area of the aircraft, automated drilling equipment can be used to replace the traditional process method for drilling. Automated equipment usually makes the final hole in one cut, and the processing efficiency is relatively high. However, according to the on-site tool testing situation, problems such as composite material delamination and splitting, drilling accuracy out of tolerance, and serious tool wear and low tool life still occur.

[0007] Based on the above situation, in order to ensure the quality of aircraft products and prevent over-tolerance in hole-making, when selecting a titanium-clad laminated hole-making tool, it is necessary to conduct a pre-cutting test in advance to inspect its hole-making quality. However, frequent pre-cutting tests seriously waste time and sheet materials. Therefore, a process guidance method is needed to predict the hole-making quality of the tool in order to reduce the pre-cutting cost and save pre-cutting time. Since the axial drilling force during the tool hole-making process is an important indicator determining the tool hole-making quality. Therefore, a prediction method for the cutting force of titanium-clad laminated hole-making can be studied to achieve the prediction of the tool hole-making quality. Summary of the Invention

[0008] To solve the above technical problems, the present invention provides a prediction method for the cutting force of titanium-clad laminated hole-making of an automated device. By analyzing the drilling process of titanium-clad laminated hole-making of the automated device, an axial drilling force theoretical model is established for different drilling stages. Based on the theoretical model, a process guidance software is developed using the C language. By inputting the tool parameters and cutting parameters into the software, the predicted axial drilling force can be output, providing guidance for the selection of tools and cutting parameters.

[0009] The technical solution of the present invention is as follows:

[0010] A prediction method for the cutting force of titanium-clad laminated hole-making of an automated device, including a relationship model among tool parameters, cutting parameters, and axial drilling force, and a process guidance software.

[0011] The establishment of the relationship model among the tool parameters, cutting parameters, and axial drilling force consists of three parts: a twist drill model (1-1), a drilling force and torque model (1-2), and a drilling force prediction model for the laminated structure (1-3).

[0012] The establishment process of the twist drill model (1-1) is as follows:

[0013] Among the geometric shapes and parameters of a standard twist drill, D is the tool diameter; d c = 2t p is the core thickness of the drill; 2ρ is the drill tip angle; β 0 is the helix angle; ψ is the web shear angle.

[0014] The axial force and torque received by the twist drill during the drilling process come from three parts: the main cutting edge, the secondary edge, and the web. During the stable drilling process, the axial force generated by the two main cutting edges accounts for 40%, and the torque generated accounts for 80%. For any point on the main cutting edge, the shear angle under oblique cutting can be expressed as:

[0015]

[0016] In the formula: is the shear angle during vertical cutting; i is the inclination angle; γ d is the dynamic rake angle, and at the same time When cutting vertically, the shear angle can be expressed as:

[0017]

[0018] λ n The friction angle during vertical cutting can be expressed as:

[0019]

[0020] The inclination angle i can be obtained from the following equation:

[0021] sin i = sin ω sin ρ

[0022] γ d can be obtained through the following equation:

[0023] γ d = γ s + β

[0024] γ s can be obtained through the expression:

[0025]

[0026] The helix angle δ r can be expressed as:

[0027]

[0028] The friction angle λ can be obtained through the expression

[0029]

[0030] The establishment process of the drilling force and torque model (1-2) is as follows:

[0031] In the oblique cutting model, the axial force dF generated by the micro-element cutting at a specified radius on the main cutting edge L can be obtained from its dF in each direction T 、dF C 、dF R Get.

[0032] The differential of the resultant force in the normal direction The differential of the resultant force in the radial direction, the differential of the resultant force in the direction parallel to the cutting speed direction, can be expressed by dF T 、dF C 、dF R Indicates:

[0033]

[0034] The axial force dF of the micro-element on the main cutting edge LIt can be obtained that:

[0035]

[0036] That is:

[0037] dF L = dF T cosεsinρ - dF C sinεsinρ - dF R cosicosρ + dF C sinicosρ

[0038] Wherein,

[0039]

[0040] During the cutting process of the main cutting edge, the axial force generated on each discrete micro-element on the main cutting edge can be simplified as:

[0041] dF = F (r) dr

[0042] Therefore, integrating the axial force generated on each micro-element on the main cutting edge gives:

[0043]

[0044] Where [r A , r B is the range of the cutting radius of the main cutting edge during the drilling process.

[0045] According to experience, the proportion of the drilling force generated by the main cutting edge in the total drilling force is 40% for the axial force, 57% for the chisel edge, and 3% for the land. It can be considered that the axial force F st = 2.5F L , where F st , F L respectively represent the axial force and torque generated by the main cutting edge during stable drilling.

[0046] The establishment process of the drilling force prediction model (1-3) for the laminated structure is as follows:

[0047] Applying the previously established twist drill model (1-1) and the drilling force and torque model (1-2) to the laminated structure, a drilling force prediction model (1-3) for the laminated structure is obtained:

[0048] During the process of drilling the laminated board, as the tool feeds, from the tool contacting the first layer of material to the main cutting edge and the secondary edge fully participating in the drilling, to the tool contacting the second material and fully drilling into the second material, to fully drilling through the laminated board. The whole process can be divided into 5 stages. The situation of the main cutting edge participating in the cutting is different in each stage.

[0049] The first stage is from when the cutting tool just touches the first layer of material until the main cutting edge and the secondary edge are completely immersed in the first layer of material. In this stage, the main cutting edge gradually cuts the first layer of material, and the effective cutting range is [r c , r (t) .

[0050] The axial force generated by the main cutting edge can be expressed as:

[0051]

[0052] The second stage is the drilling stage from when the main cutting edge and the secondary edge of the cutting tool completely enter the workpiece until the cutting tool just touches the second layer of the workpiece. In this stage, the main cutting edge is fully involved in cutting the composite material, and the effective range is [r c , R].

[0053] The axial force generated by the main cutting edge can be expressed as:

[0054]

[0055] The third stage is from when the cutting tool just starts to cut the second layer of material until the main cutting edge and the secondary edge are completely immersed in the second layer of material. In this stage, the main cutting edge is simultaneously involved in cutting two material plates, and their cutting ranges are [r c , r (t) and [r (t) , R].

[0056] At this time, the axial force and torque generated on the main cutting edge are the sum of the axial force and torque generated by cutting the two parts of the material, that is:

[0057]

[0058] The fourth stage is from when the main cutting edge and the secondary edge of the cutting tool completely enter the second layer of material until the cutting tool just cuts to the bottom of the workpiece. In this stage, the main cutting edge cuts the second layer of the material plate entirely, and the effective range of participation in cutting is [r c , R], that is:

[0059]

[0060] The fifth stage is when the cutting tool gradually drills out of the workpiece until it completely penetrates. In this stage, the cutting of the workpiece by the main cutting edge gradually decreases, and the cutting range is [r (t) , R]. During the cutting process, the radius r (t) at the intersection of the main cutting edge and the bottom surface of the titanium alloy, so the axial force and torque generated by the main cutting edge in this stage are:

[0061]

[0062] According to the proportion of the drilling force generated by the main cutting edge based on experience, it can be considered that the axial force F generated by the chisel edge when stable is h = 1.5F m , which surges to the maximum value within a very short time after the tool contacts the workpiece. The variation of the drilling force with time during the entire drilling process can be expressed as:

[0063] F (t) = F h (t) + F m (t)

[0064] The process guidance software described above includes a parameter input module (2-1), a simulation module (2-2), and a cutting force curve output module (2-3).

[0065] In the parameter input module (2-1), tool structure parameters and cutting parameters need to be input, and the parameters need to be input row by row in sequence. Among them, the corresponding tool parameters need to be input in the first row: ε is a constant, and δ is the drill bit helix angle; the tool parameters and cutting parameters need to be input in the second row: D is the drill bit diameter, and f is the feed rate; the tool parameter t p is half of the core thickness, and β is the feed angle; the tool parameter θ is the cutting angle, and K AB is the shear stress intensity factor; the tool parameter 2ρ is the drill tip angle, and r c is half of the length of the tool chisel edge; the tool parameters and cutting parameters need to be input in the sixth row: R is the drill bit radius, and n is the drill bit speed.

[0066] The functions of the simulation module (2-2) are as follows: After inputting the cutting parameters and tool parameters, use the programming language to substitute the parameters into the relationship model between the tool parameters, cutting parameters, and axial drilling force for calculation. After iterative calculation, the predicted cutting force value is simulated. In the process guidance software, after inputting the tool parameters and cutting parameters, click the "Start Simulation" button to start the operation of the simulation module (2-2).

[0067] The cutting force curve output module (2-3) can convert the cutting force value calculated by the simulation into a visual cutting force prediction curve and display it on the interface of the process guidance software. By changing some parameters without changing other control factors, the output curve result can be changed. If the parameters are changed one by one on the same interface, the curves can appear in the same interface simultaneously.

[0068] The beneficial effects brought by the present invention are:

[0069] Through the cutting force prediction model and the process guidance software, the axial drilling force of the titanium-clad laminated hole-making tool can be predicted, and then the hole-making quality of the tool can be predicted. The tool trial cost is effectively reduced, and the tool selection efficiency of the titanium-clad laminated hole-making tool is improved. Description of the Drawings

[0070] Figure 1 It is a schematic diagram of the structure of a standard twist drill;

[0071] Figure 2 It is a schematic diagram of an oblique angle drilling model;

[0072] Figure 3 It is a schematic diagram of the cutting force prediction model on the main cutting edge;

[0073] Figure 4 It is a schematic diagram of different stages of the drilling process;

[0074] Figure 5 It is a schematic diagram of the cutting force prediction curve. Detailed Implementation Manner

[0075] The detailed implementation manner and steps of the present invention are as follows:

[0076] 1. Select the tool to be analyzed, and measure and calculate the required tool parameters according to the cutting force prediction model;

[0077] 2. Open the process guidance software: Select the AxForce.zip file for decompression. After decompressing the file, open the Debug folder and double-click the AxForce.exe file to run and open the software.

[0078] 3. Input the tool parameters corresponding to the first line, ε is a constant, and δ is the drill helix angle.

[0079] 4. Input the tool parameters corresponding to the second line, D is the drill diameter, and f is the feed rate.

[0080] 5. Input the tool parameters corresponding to the third line, t p is half of the core thickness, and β is the feed angle.

[0081] 6. Input the tool parameters corresponding to the fourth line, θ is the cutting angle, and K AB is the shear stress strength factor.

[0082] 7. Input the tool parameters corresponding to the fifth line, 2ρ is the drill tip angle, and r c is half of the tool chisel edge length.

[0083] 8. Input the tool parameters corresponding to the sixth line, R is the drill radius, and n is the drill speed.

[0084] 9. After the parameter input is completed, click Start Simulation to obtain the output curve of the drilling force changing with time.

[0085] 10. Change some parameters, without changing other control factors, and the output curve result can be changed. If the parameters are changed one by one in the same interface, the curves can appear in the same interface at the same time.

[0086] 11. Record the output cutting force curve results for reference in tool selection.

[0087] Finally, the present invention is not limited to the above description, but may cover any deformation scheme within the scope defined by the specification.

Claims

1. A method for predicting cutting force of titanium composite lamination hole making in automated equipment, characterized in that: Including tool parameters, cutting parameters and axial drilling force relationship model, process guidance software; The establishment of the relationship model between tool parameters, cutting parameters and axial drilling force consists of three parts: twist drill model (1-1), drilling force and torque model (1-2), and laminated structure drilling force prediction model (1-3); The twist drill model (1-1) is established as follows: In the geometry and parameters of standard twist drills, D is the tool diameter; d c =2t p is the drill core thickness; 2ρ is the drill tip angle; β0 is the helix angle; ψ is the chisel edge angle; The axial force and torque of the twist drill during drilling come from the main cutting edge, the secondary cutting edge and the chisel edge. In the stable drilling process, the axial force generated by the two main cutting edges accounts for 40%, and the torque generated accounts for 80%. For any point on the main cutting edge under bevel cutting, the shear angle It is expressed as: Where: As the shear angle during vertical cutting; i is the inclination angle; γ d is the dynamic rake angle, and The shear angle for vertical cutting is expressed as: λ n The friction angle during vertical cutting is expressed as: The equation below the inclination angle i yields: sin i = sin ω sin ρ γ d The following equation gives: c d =c s +b γ s The expression is: Helix angle δ r It is expressed as: The friction angle λ is obtained by the expression The drilling force and torque model (1-2) is established as follows: In the oblique cutting model, the axial force dF generated by the micro-element cutting at a specified radius on the main cutting edge L Through its dF in all directions T 、dF C 、dF R get; Differential of the resultant force in the normal direction The differential of the resultant force in the radial direction, parallel to the cutting speed, is expressed as dF T 、dF C 、dF R express: The axial force dF of the microelement on the main cutting edge L It turns out that: Right now: dF L =dF T cosεsinρ-dF C sinεsinρ-dF R cosicosρ+dF C sinicosρ in, During the cutting process, the axial force generated by the main cutting edge on each discrete micro-element on the main cutting is simplified as: dF=F (r) dr Therefore, the integral of the axial force generated by each microelement on the main cutting edge is: Among them [r A , r B ] is the cutting radius range of the main cutting edge during drilling; The process of establishing the prediction model (1-3) of the drilling force of the laminated structure is as follows: The twist drill model (1-1) and the drilling force and torque model (1-2) established previously are applied to the laminated structure to obtain a laminated structure drilling force prediction model (1-3): In the process of drilling the laminated plate, as the tool is fed, from the tool contacting the first layer of material to the main cutting edge and the secondary edge fully participating in the drilling, to the tool contacting the second material to fully drilling into the second material, to completely drilling through the laminated plate; the whole process is divided into 5 stages; the main cutting edge participates in the cutting differently in each stage; In the first stage, from the moment the tool contacts the first layer of material to the moment the main cutting edge and the secondary cutting edge are completely immersed in the first layer of material; in this stage, the main cutting edge gradually cuts the first layer of material, and the effective cutting range is [r c , r (t) ]; The axial force generated by the main cutting edge can be expressed as: The second stage is the drilling stage from when the main cutting edge and the secondary cutting edge of the tool completely enter the workpiece to when the tool just contacts the second layer of the workpiece; in this stage, the main cutting edge is fully involved in the cutting of the composite material, and the range of action [r c , R]; The axial force generated by the main cutting edge can be expressed as: In the third stage, the tool starts to participate in cutting the second layer of material until the main cutting edge and the secondary cutting edge are completely immersed in the second layer of material; in this stage, the main cutting edge participates in cutting the two material plates at the same time, and the cutting range is [r c , r (t) ]、[r (t) , R]; At this time, the axial force and torque generated in the main cutting are the sum of the axial force and torque generated by cutting the two parts of the material, that is: In the fourth stage, the main cutting edge and the secondary cutting edge of the tool completely enter the second layer of material until the tool just cuts the bottom of the workpiece; in this stage, the main cutting edge completely cuts the second layer of material plate, and the range of action involved in cutting is [r c , R], that is: In the fifth stage, the tool gradually drills out of the workpiece until it penetrates completely; in this stage, the main cutting edge gradually reduces the cutting of the workpiece, and the range of cutting [r (t) , R]; During the cutting process, the radius of the interface between the main cutting edge and the bottom surface of the titanium alloy is r (t) , so the axial force and torque generated by the main cutting edge at this stage are: According to the experience, the proportion of drilling force generated by the main cutting edge is considered to be the axial force F generated by the chisel edge when stable. h =1.5F m , which surges to the maximum value in a very short time after the tool contacts the workpiece; the variation of drilling force over time during the entire drilling process is expressed as: F (t) =F h (t)+F m (t)。 2. A cutting force prediction method for hole making of titanium composite laminated automated equipment as claimed in claim 1, characterized in that: The process guidance software comprises a parameter input module (2-1), a simulation module (2-2), and a cutting force curve output module (2-3); The tool structure parameters and cutting parameters need to be entered in the parameter input module (2-1). The parameters need to be entered in sequence row by row. The first row needs to enter the corresponding tool parameters: ε is a constant, δ is the drill helix angle; the second row needs to enter the tool parameters and cutting parameters: D is the drill diameter, f is the feed speed; the third row needs to enter the tool parameters: t p is half the thickness of the drill core, β is the feed angle; the fourth line requires the input of tool parameters: θ is the cutting angle, K AB is the shear stress intensity factor; the fifth line requires the input of tool parameters: 2ρ is the drill tip angle, r c It is half the length of the tool chisel edge; the sixth line requires the input of tool parameters and cutting parameters: R is the drill radius, and n is the drill speed.

3. A cutting force prediction method for hole making of titanium composite laminated layer in automated equipment as claimed in claim 1 or 2, characterized in that: The functions of the simulation module (2-2) are as follows: after inputting the cutting parameters and tool parameters, the parameters are substituted into the tool parameters, cutting parameters and axial drilling force relationship model using a programming language for calculation, and after iterative calculation, the predicted cutting force value is obtained by simulation; in the process guidance software, after inputting the tool parameters and cutting parameters, click the "Start Simulation" button to start the operation of the simulation module (2-2).

4. A cutting force prediction method for hole making in titanium composite laminated automated equipment as claimed in claim 1 or 2, characterized in that: The cutting force curve output module (2-3) converts the cutting force value calculated by simulation into a visual cutting force prediction curve and displays it on the process guidance software interface; by changing some parameters and keeping other control factors unchanged, the output curve result can be changed. If the parameters are changed one by one in the same interface, the curves can appear in one interface at the same time.

5. The method for predicting cutting force of titanium composite lamination hole making in automated equipment according to claim 3, characterized in that: The cutting force curve output module (2-3) converts the cutting force value calculated by simulation into a visual cutting force prediction curve and displays it on the process guidance software interface; by changing some parameters and keeping other control factors unchanged, the output curve result can be changed. If the parameters are changed one by one in the same interface, the curves can appear in one interface at the same time.

6. A cutting force prediction method for hole making in titanium composite laminated automated equipment as claimed in claim 1, 2 or 5, characterized in that: The ratio of the drilling force generated by the main cutting edge to the total drilling force is 40% for the axial force, 57% for the chisel edge, and 3% for the margin. The axial force F during stable drilling st =2.5F L , where F st 、F L , respectively represent the axial force and torque generated by the main cutting edge during stable drilling.

7. A cutting force prediction method for hole making in titanium composite laminated automated equipment as claimed in claim 3, characterized in that: The ratio of the drilling force generated by the main cutting edge to the total drilling force is 40% for the axial force, 57% for the chisel edge, and 3% for the margin. The axial force F during stable drilling st =2.5F L , where F st 、F L , respectively represent the axial force and torque generated by the main cutting edge during stable drilling.

8. A cutting force prediction method for hole making in titanium composite laminated automated equipment as claimed in claim 4, characterized in that: The ratio of the drilling force generated by the main cutting edge to the total drilling force is 40% for the axial force, 57% for the chisel edge, and 3% for the margin. The axial force F during stable drilling st =2.5F L , where F st 、F L , respectively represent the axial force and torque generated by the main cutting edge during stable drilling.

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