A milling machining parameter optimization method based on spindle speed sinusoidal variation

Abstract

The application relates to a milling machining parameter optimization method based on spindle speed sinusoidal variation, and belongs to the technical field of numerical control machining. The method comprises the following steps: determining a parameter range of spindle speed variation parameters according to given kinematics limits of a spindle; the spindle speed variation parameters comprise a speed amplitude variation ratio and a speed frequency variation ratio; dividing the parameter range composed of the speed amplitude variation ratio and the speed frequency variation ratio into multiple parameter sets with equal intervals; and establishing an optimization model according to axial cutting depth, radial cutting depth and the spindle speed variation parameter set, optimizing the axial cutting depth, the radial cutting depth and the spindle speed variation parameter set to obtain optimal values. The method can realize the shortest machining track through the system optimization of four groups of machining parameters, i.e., the axial cutting depth, the radial cutting depth and the spindle speed variation amplitude and frequency, so that the machining time is effectively reduced, and the machining efficiency is improved.

Description

Technical Field

[0001] This invention belongs to the field of CNC machining technology, and relates to a method for optimizing CNC machining parameters, particularly a method for optimizing milling machining parameters based on the sinusoidal variation of spindle speed. Background Technology

[0002] Existing technology discloses a method for optimizing milling parameters based on continuous triangular variation of spindle speed to suppress chatter. It first performs stability simulation analysis on different spindle speed variation parameters, then calculates the actual selectable range of spindle speed variation parameters based on spindle acceleration limitations, and finally selects the set of machining parameters with the largest limiting axial depth of cut within the allowable range as the optimal result. However, it only considers the optimization of axial depth of cut and the acceleration limitation of spindle speed during machining, without considering factors such as radial depth of cut optimization, workpiece shape, and spindle acceleration limitations.

[0003] Existing technology discloses a method for optimizing milling parameters based on continuous triangular and sinusoidal variations of spindle speed to suppress chatter. It summarizes the general expressions for triangular or sinusoidal variations of spindle speed, then calculates the selectable parameter ranges for each based on spindle acceleration limitations, and finally selects the optimal combination of machining parameters under the two different variation forms through simulation results of stability analysis. However, it only considers the spindle acceleration limitation and the optimization of axial cutting depth during machining, without considering the aforementioned factors such as spindle jerk and radial cutting depth.

[0004] The typical characteristics of the above-mentioned existing technologies are: during the optimization process, the spindle speed acceleration and the actual workpiece shape factors were not taken into consideration, and the radial cutting depth was not systematically optimized. As a result, in actual application, the optimization results of the machining parameters cannot reach the optimal level, and there is still room for further improvement in actual machining efficiency. Summary of the Invention

[0005] The technical problem to be solved by this invention is:

[0006] To improve the machining efficiency of CNC milling systems when using a continuous sinusoidal variation of spindle speed to suppress chatter, this invention provides a milling parameter optimization method that synchronously optimizes the spindle speed variation parameters and cutting parameters for milling machining methods based on continuous sinusoidal variation of spindle speed.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0008] A method for optimizing milling parameters based on sinusoidal changes in spindle speed is characterized by optimizing four sets of machining parameters: axial and radial cutting depths, spindle speed amplitude, and frequency variation ratio, to obtain the combination of milling parameters that achieves the shortest machining trajectory; including:

[0009] Based on the given kinematic constraints of the spindle, the parameter range of the spindle speed variation parameters is determined; the spindle speed variation parameters include the speed amplitude variation ratio and the speed frequency variation ratio; the parameter range composed of the speed amplitude variation ratio and the speed frequency variation ratio is divided into multiple parameter sets with equal intervals;

[0010] An optimization model is established based on the axial cutting depth, radial cutting depth, spindle speed variation parameter set, and milling trajectory length of the tool. The optimal values ​​of the axial cutting depth, radial cutting depth, and spindle speed variation parameter set are then obtained.

[0011] A further technical solution of the present invention: the parameter range for determining the spindle speed variation parameter based on the given kinematic constraints of the spindle is specifically as follows:

[0012] The parameters for spindle speed variation are:

[0013]

[0014] in, The average spindle speed, The range of change in spindle speed The angular velocity of the spindle speed; and These refer to the ratio of spindle speed amplitude variation and the ratio of spindle speed frequency variation, respectively. The specific allowable parameter ranges are as follows: It is expressed as follows:

[0015] Among them, coefficient for:

[0016]

[0017] in, and These are the acceleration and jerk limits of the main shaft, respectively.

[0018] A further technical solution of the present invention: the optimization model is as follows:

[0019]

[0020] in, Let be the objective function. and These represent the axial and radial cutting layers of the trajectory, respectively. and These represent the axial and radial cutting layers where the trajectory is currently located, respectively. This represents the length of the tool cutting trajectory at the current layer. and These are the axial and radial cutting depths of the cutting tool, respectively. The diameter of the cutting tool. Arbitrary eigenvalues ​​of the transfer matrix constructed for stability analysis of the milling process. This means that the absolute value of all eigenvalues ​​of the transfer matrix must be less than 1.

[0021] A further technical solution of the present invention: the optimization of the parameter set of axial cutting depth, radial cutting depth, and spindle speed variation of the tool to obtain the optimal value includes:

[0022] (1) Change the axial cutting depth and calculate the characteristic value until If the condition is not met, record the set of parameters for the axial cutting depth, radial cutting depth, and spindle speed variation under that condition;

[0023] (2) Change the spindle speed variation parameter set, repeat step (1), and record the axial cutting depth, radial cutting depth and spindle speed variation parameter set corresponding to the minimum objective function as the current optimal value;

[0024] (3) Change the radial cutting depth, repeat steps (1) and (2), and record the axial cutting depth, radial cutting depth and spindle speed change parameter set corresponding to the minimum objective function as the final optimal value.

[0025] A further technical solution of the present invention: the axial cutting depth optimized and changed in two adjacent cycles. and The following relationships need to be guaranteed:

[0026]

[0027] in, This represents the actual height of the workpiece's cutting area. This indicates that the current step is repeated up to the [number]th step. Second-rate, An integer represents the currently selected axial cutting depth. The number of axial cutting layers required for machining.

[0028] A further technical solution of the present invention: the radial cutting depth optimized and changed in two adjacent cycles. and The following relationships need to be guaranteed:

[0029]

[0030] in, This represents the actual width of the workpiece's cutting area. This indicates that the current step is repeated up to the [number]th step. Second-rate, An integer represents the currently selected radial cutting depth. The number of radial cutting layers required for machining.

[0031] A computer system is characterized by comprising: one or more processors, and a computer-readable storage medium for storing one or more programs, wherein when the one or more programs are executed by the one or more processors, the one or more processors cause the one or more processors to implement the method described above.

[0032] A computer-readable storage medium is characterized by storing computer-executable instructions, which, when executed, are used to implement the above-described method.

[0033] The beneficial effects of this invention are as follows:

[0034] This invention provides a milling parameter optimization method based on sinusoidal changes in spindle speed. This method achieves the shortest milling trajectory by optimizing cutting parameters and spindle speed variation parameters. Based on the principle of suppressing chatter through continuous sinusoidal changes in spindle speed, compared to existing methods, this invention obtains the combination of milling parameters that achieves the shortest machining trajectory through systematic optimization of four sets of machining parameters: axial and radial cutting depths, and the amplitude and frequency of spindle speed variations. This effectively reduces machining time and improves machining efficiency. Attached Figure Description

[0035] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0036] Figure 1 These are the parts that need to be processed in the embodiments of the method of the present invention.

[0037] Figure 2 This is a flowchart illustrating the optimization of specific processing parameters in the embodiments of the present invention.

[0038] Figure 3 This refers to the allowable range of spindle speed variation parameters solved in the embodiments of the present invention.

[0039] Figure 4 This is the actual processing result in the embodiment of the method of the present invention. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0041] This invention provides a method for optimizing milling parameters based on sinusoidal changes in spindle speed, comprising the following steps:

[0042] Step 1: Based on the given kinematic constraints of the spindle, calculate the actual allowable range of the spindle speed variation parameters. First, the sinusoidal spindle speed variation is:

[0043]

[0044] in, For time, The relationship between spindle speed and time. The average spindle speed, The range of change in spindle speed The angular velocity of the spindle speed. The phase difference between the spindle speed and the actual feed rate.

[0045] The parameters for spindle speed variation are:

[0046]

[0047] in, and These refer to the ratio of change in rotational speed amplitude and the ratio of change in rotational speed frequency, respectively. The specific allowable parameter ranges are as follows: It is expressed as follows:

[0048] Among them, coefficient for:

[0049]

[0050] in, and These are the acceleration and jerk limits of the main shaft, respectively;

[0051] Parameter range Divided into a set of spindle speed variation parameters with equal intervals For subsequent optimization.

[0052] Step 2: Define the optimization problem:

[0053]

[0054] in, Let be the objective function. and These represent the axial and radial cutting layers of the trajectory, respectively. and These represent the axial and radial cutting layers where the trajectory is currently located, respectively. This represents the length of the tool cutting trajectory at the current layer. and These are the axial and radial cutting depths of the cutting tool, respectively. The diameter of the cutting tool. Arbitrary eigenvalues ​​of the transfer matrix constructed for stability analysis of the milling process. This means that the absolute value of all eigenvalues ​​of the transfer matrix must be less than 1. Select the initial axial cutting depth. Initial radial cutting depth With the initial spindle speed parameter set .

[0055] Step 3: Based on the currently selected parameters, calculate the eigenvalues ​​using the semi-discrete method. If satisfied This increases the axial cutting depth. Calculate the eigenvalues ​​again. Does it meet the requirements? Conditions. Repeat the above steps until... If not satisfied, record satisfied. The last set of axial depths of the conditions = and the corresponding radial depth of cut and parameter set .

[0056] in, and All of these are the radial cutting depth parameters and parameter sets selected for current optimization, which are fixed values ​​in step two. and This represents the radial cutting depth at this point. The optimization of the parameter set in the nth iteration This is the second optimization. Furthermore, the axial cutting depth between two adjacent optimizations... and (for the first) Next and first (This time) the following relationships need to be guaranteed:

[0057]

[0058] in, This represents the actual height of the workpiece's cutting area. This indicates that the current step is repeated up to the [number]th step. Second-rate, An integer represents the currently selected axial cutting depth. The number of axial cutting layers required for machining.

[0059] Step 4: Based on the range, sequentially replace the parameter set P within the range, repeating Step 2 until all parameter sets within the range have been used. Based on the recorded parameters... , and Calculate the objective function value at this time. If the objective function is minimized, then the parameters at this point are... , and Set as the current optimization result:

[0060]

[0061] in, , and These represent the sets of parameters for the current optimized axial cutting depth, optimal radial cutting depth, and optimal spindle speed variation, respectively.

[0062] Conversely, if the result is not satisfactory, proceed to the next optimization step.

[0063] Step 5: Add radial cutting parameters With initial axial cutting depth The radial cutting depth between two consecutive optimizations. and (for the first) Next and first (This time) the following relationships need to be guaranteed:

[0064]

[0065] in, This represents the actual width of the workpiece's cutting area. This indicates that the current step is repeated up to the [number]th step. Second-rate, An integer represents the currently selected radial cutting depth. The number of radial cutting layers required for machining.

[0066] To simplify the optimization calculation, the initial axial cutting depth We need to ensure that the objective function does not increase at the current radial depth of cut, that is:

[0067]

[0068] axial cutting depth With parameter set Replace with initial axial cutting depth With the initial parameter set Repeat steps three and four. When the radial cutting parameters are changed again... The conditions are not met. When the time is up, the optimization ends, and the final optimized processing parameters are output. , and .

[0069] This method can simultaneously optimize four machining parameters, including axial cutting depth, radial cutting depth, and the variation range and frequency of spindle speed. It also considers the actual shape of the workpiece and the acceleration and jerk limitations of the spindle, using the actual machining path length as the optimization target to achieve the shortest machining path, thereby effectively improving machining efficiency.

[0070] Example:

[0071] Reference Figure 1-4 The workpiece to be processed in the method of this invention is as follows: Figure 1 As shown, the specific processing area that needs optimization is... Figure 1 The dark area shown in b. The machining parameters for this area are optimized using both the method of this invention and existing spindle speed variation parameter optimization methods, and machining is performed using an 8mm three-tooth flat end mill. The required average spindle speed is... The maximum feed per tooth is 0.05 mm, and the maximum spindle acceleration is limited to... The maximum jerk is limited to 8000 rpm / s. 2 The phase difference between the feed rate and the spindle speed is .

[0072] The flowchart of the milling parameter optimization method based on sinusoidal variation of spindle speed proposed in this invention is as follows: Figure 2 As shown, the specific steps are as follows:

[0073] Step 1: Based on the given kinematic constraints of the spindle, calculate the actual allowable range of the spindle speed variation parameters. First, the sinusoidal spindle speed variation is:

[0074]

[0075] in, For time, The relationship between spindle speed and time. The average spindle speed, The range of change in spindle speed The angular velocity of the spindle speed. This is the phase difference between the spindle speed and the actual feed rate. The spindle speed variation parameters are:

[0076]

[0077] and These refer to the ratio of change in rotational speed amplitude and the ratio of change in rotational speed frequency, respectively. The specific allowable parameter ranges are as follows: It is expressed as follows:

[0078] Among them, coefficient for:

[0079]

[0080] in and It refers to the acceleration and jerk limits of the spindle.

[0081] Parameter range Divided into a set of spindle speed variation parameters with equal intervals Used for subsequent optimization, specific results are as follows: Figure 3 As shown.

[0082] Step 2: Define the optimization problem:

[0083]

[0084] in Let be the objective function. and These represent the axial and radial cutting layers of the trajectory, respectively. and These represent the axial and radial cutting layers where the trajectory is currently located, respectively. This represents the length of the tool cutting trajectory at the current layer. and These are the axial and radial cutting depths of the cutting tool, respectively. The diameter of the cutting tool. Arbitrary eigenvalues ​​of the transfer matrix constructed for stability analysis of the milling process. This means that the absolute value of all eigenvalues ​​of the transfer matrix must be less than 1. Determine the initial axial cutting depth. Initial radial cutting depth With the initial spindle speed variation parameter set .

[0085] Step 3: Calculate the eigenvalues ​​based on the current parameters. If satisfied This increases the axial cutting depth. Calculate the eigenvalues ​​again. Does it meet the requirements? Conditions. Repeat the above steps until... If not satisfied, record satisfied. The last set of axial depths of the conditions = and the corresponding radial depth of cut and parameter set .

[0086] in, and All of these are the radial cutting depth parameters and parameter sets selected for current optimization, which are fixed values ​​in step two. and This represents the radial cutting depth at this point. The optimization of the parameter set in the nth iteration This is the second optimization. Furthermore, the axial cutting depth between two adjacent optimizations... and (for the first) Next and first (This time) the following relationships need to be guaranteed:

[0087]

[0088] in, This represents the actual height of the workpiece's cutting area. This indicates that the current step is repeated up to the [number]th step. Second-rate, An integer represents the currently selected cutting depth. The required number of axial cutting layers.

[0089] Step 4: Based on the set Repeat step two, changing the set in turn, until all elements in the set have been used. Based on the recorded parameters... , and Calculate the objective function value at this time. If the objective function is minimized, then the parameters at this point are... , and Each is set to the current optimal axial cutting depth. Optimal radial cutting depth With the optimal spindle speed variation parameter set :

[0090]

[0091] Conversely, if the result is not satisfactory, proceed to the next optimization step.

[0092] Step 5: Add radial cutting parameters With initial axial cutting depth The radial cutting depth between two consecutive optimizations. and (for the first) Next and first (This time) the following relationships need to be guaranteed:

[0093]

[0094] To simplify the optimization calculation, the initial axial cutting depth We need to ensure that the objective function does not increase at the current radial depth of cut, that is:

[0095]

[0096] axial cutting depth With parameter set Replace with initial axial cutting depth With the initial set of spindle speed variation parameters Repeat steps three and four. When the radial cutting parameters are changed again... The conditions are not met. When the time is up, the optimization ends and the final optimized processing parameters are output. , and .

[0097] Table 1 shows the optimization results of milling parameters for different methods in the embodiments of the present invention. It can be seen that the required machining trajectory length for the optimized machining parameters obtained by this method is 18.21 m, while the required machining trajectory length for the parameters of the existing spindle speed variation parameter optimization method used for comparison is 22.72 m, and the required trajectory length for parameters using constant speed stable machining is 28.7 m. Compared with the existing spindle speed variation parameter optimization method, this method achieves an improvement of 20%; compared with constant speed machining, this method achieves an improvement of 37%. Figure 4 The actual parts and surface results processed using three different processing parameters show that there is no significant difference in the processed surfaces of the three methods, which indicates that this method can improve processing efficiency while ensuring the same processing quality.

[0098] Table 1 Comparison of processing parameters and path length results for each method

[0099]

[0100] In summary, this invention effectively considers the acceleration and jerk limitations of the spindle speed, and optimizes milling parameters based on the actual workpiece machining trajectory, generating the shortest machining trajectory and improving milling efficiency. Compared to existing spindle speed variation parameter optimization algorithms, this invention comprehensively considers the synchronous optimization of axial and radial cutting depths, thereby effectively reducing the length of the machining trajectory and shortening machining time while ensuring stable machining, thus significantly improving the milling efficiency of the CNC system.

[0101] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the scope of the technology disclosed in the present invention, and such modifications or substitutions should all be covered within the scope of protection of the present invention.

Claims

1. A method for optimizing milling parameters based on the sinusoidal variation of the spindle speed, characterized in that The optimization of four groups of machining parameters, i.e. axial and radial cutting depths, and spindle speed amplitude and frequency change ratios, obtains the milling machining parameter combination for realizing the shortest machining track; The method comprises the steps of: According to the given kinematical limit of the spindle, the parameter range of the spindle speed change parameter is determined; the spindle speed change parameter comprises a speed amplitude change ratio and a speed frequency change ratio; the parameter range composed of the speed amplitude change ratio and the speed frequency change ratio is divided into multiple parameter sets with equal intervals; The specific process of determining the parameter range of the spindle speed change parameter according to the given kinematical limit of the spindle is as follows: The spindle speed change parameter is: wherein, is the average spindle speed, is the variation amplitude of the spindle speed, is the angular speed of the spindle speed; and are the amplitude variation ratio of the spindle speed and the frequency variation ratio of the spindle speed, respectively, then the specific allowable parameter range is represented as follows: wherein the coefficients are: wherein, with are the acceleration and jerk limits of the main shaft, respectively; According to the axial and radial cutting depths of the tool, the spindle speed change parameter set and the milling machining track length, an optimization model is established, and the axial and radial cutting depths of the tool and the spindle speed change parameter set are optimized to obtain optimal values.

2. The method for optimizing milling parameters based on the sinusoidal variation of spindle speed according to claim 1, characterized in that, The optimization model is: in, Let be the objective function. and These represent the axial and radial cutting layers of the trajectory, respectively. and These represent the axial and radial cutting layers where the trajectory is currently located, respectively. This represents the length of the tool cutting trajectory at the current layer. and These are the axial and radial cutting depths of the cutting tool, respectively. The diameter of the cutting tool. Arbitrary eigenvalues ​​of the transfer matrix constructed for stability analysis of the milling process. This means that the absolute value of all eigenvalues ​​of the transfer matrix must be less than 1.

3. The method of claim 2, wherein the method is characterized by: The optimization of the axial and radial cutting depths of the tool and the spindle speed change parameter set to obtain optimal values comprises: (1) change the axial cutting depth, calculate the eigenvalue until if not satisfied, record the axial cutting depth, radial cutting depth and spindle speed variation parameter set under this condition; (2) replacing the spindle speed change parameter set, repeating the step (1), and recording the axial and radial cutting depths and the spindle speed change parameter set corresponding to the minimum target function as the current optimal values; (3) replacing the radial cutting depth, repeating the steps (1) and (2), and recording the axial and radial cutting depths and the spindle speed change parameter set corresponding to the minimum target function as the final optimal values.

4. The method of claim 3, wherein the milling parameter optimization method is based on a sinusoidal variation of the spindle speed. The axial cutting depth of two successive optimization replacements is adjacent With The following relationship needs to be ensured: wherein, is the actual height of the workpiece cutting area, represents the current step is repeated to the time, is an integer representing the current selected axial cutting depth the number of axial cutting layers needed to be machined.

5. The method for optimizing milling parameters based on the sinusoidal variation of spindle speed according to claim 4, characterized in that, Radial cutting depth of the two successive optimization replacements With The following relationship must be ensured: wherein, is the actual width of the workpiece cutting area, represents the current step repetition to the th, is an integer representing the current selected radial cutting depth number of radial cutting layers needed for machining.

6. A computer system, characterized by The method comprises the steps of: One or more processors, a computer readable storage medium for storing one or more programs, wherein when the one or more programs are executed by the one or more processors, the one or more processors realize the method of any one of claims 1-5.

7. A computer readable storage medium characterized by Computer executable instructions are stored, and the instructions are executed to realize the method of any one of claims 1-5.

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