A machining tool path optimization system and method for a multi-axis numerical control machine tool

Abstract

The present invention relates to the field of numerical control machining technology, and specifically relates to a machining tool path optimization system and method for a multi-axis numerical control machine tool. By considering the change in machining temperature and the temperature change between adjacent machining positions, the temperature change degree of the adjacent machining positions is minimized, thereby reducing the thermal error of the machining tool, that is, reducing the wear of the moving tool. First, the initial temperature change index of the initial machining position is obtained from the initial machining position, the temperature drop index during the tool movement is calculated, and at the same time, the reference temperature change index of the next machining position connected thereto at this position is obtained, so that the tool path planning takes into account the temperature change of the connected process, and the path nodes are selected in combination with the path length, so that the path selection takes into account both efficiency and temperature influence, thereby determining a more reasonable tool machining path, that is, the effect of path planning according to the optimized machining tool path obtained in this application is better.

Description

Technical Field

[0001] The present invention relates to the technical field of numerical control machining, and particularly relates to a machining tool path optimization system and method for a multi-axis numerical control machine tool. Background Art

[0002] The machining of a multi-axis numerical control machine tool refers to adding one or more coordinate axes for simultaneous movement during three-axis milling machining and ordinary two-axis turning machining. According to the number of axes, multi-axis machine tools can be divided into four-axis and five-axis machine tools. Commonly, such as a five-axis machining numerical control machine tool, by simultaneously controlling the simultaneous movement of five coordinates, the functions of multi-process machining are combined, so that after a workpiece is clamped once, multi-process machining of the workpiece can be completed. In multi-axis machining, it is necessary to calculate the point coordinate data, and at the same time, it is necessary to obtain the vector direction data at the coordinate points. This vector direction is usually used to represent the tool axis direction during machining, so as to select the path according to the characteristics of the workpiece.

[0003] The existing optimization method for machining tool paths is to use an algorithm based on the equidistant offset method according to the requirements of the machined workpiece. After discretizing the surface, equidistant offset is performed to generate a closed equidistant ring, and then a weighted directed graph of the closed equidistant ring is generated based on graph theory. Finally, the Dijkstra algorithm is used to generate the shortest tool path, obtaining the theoretically optimal machining tool path. However, in the actual machining process of the machine tool, due to the integration and continuity of multi-axis machining, a large amount of heat will be generated during the machining process of the multi-axis tool when the rotating shaft rotates at high speed. When heat accumulates after the tool works continuously, because the shortest path is selected during tool path planning, it is difficult for the temperature of the tool to drop in time. The heat accumulation during tool machining will cause thermal error; that is, the numerical control machine tool will deform under the interaction of internal and external heat sources, and then the position of the spindle axis relative to the workbench will change, and then the offset between the tool installed on the spindle and the machined part placed on the workbench will occur. This change will ultimately cause machining error of the part, and this phenomenon is thermal error; thermal error will cause thermal deformation, accelerate tool wear and also reduce the machining accuracy of the workpiece. Therefore, the existing method of using the Dijkstra algorithm to generate the shortest tool path has a poor effect on tool path planning because thermal error is not considered. Summary of the Invention

[0004] In order to solve the technical problem that the method of using the Dijkstra algorithm to generate the shortest tool path has a poor effect on tool path planning because thermal error is not considered, the purpose of this application is to provide a machining tool path optimization system and method for a multi-axis numerical control machine tool, and the specific technical solutions adopted are as follows:

[0005] The present application proposes a method for optimizing the machining tool path of a multi-axis numerical control machine tool, and the method includes:

[0006] During the process of machining a workpiece by a numerical control machine tool, obtain the machining time of each machining position on the workpiece, as well as the spindle speed and the real-time spindle temperature of the machining tool when machining the starting machining position;

[0007] Determine the starting temperature change index of the starting machining position according to the machining time, spindle speed, and real-time spindle temperature range of the starting machining position; according to the distance between the starting machining position and each machining position, the maximum value of the real-time spindle temperature of the starting machining position, and the prior environmental temperature, determine the temperature drop index between the starting machining position and each machining position;

[0008] Based on the prior temperature drop data, determine the simulated starting temperature of each machining position according to the distance between the starting machining position and each machining position and the temperature at the end of machining of the starting machining position; according to the simulated starting temperature and the machining time of each machining position, determine the reference temperature change index of each machining position;

[0009] Determine the path passability from the starting machining position to each machining position according to the starting temperature change index, the temperature drop index, the reference temperature change index, and the relative distance; screen out the next node machining position corresponding to the starting machining position according to the path passability;

[0010] Perform iterative screening of new node machining positions with the node machining position, and obtain the optimized machining tool path of the numerical control machine tool after traversing all machining positions.

[0011] Further, the process of obtaining the starting temperature change index includes:

[0012] Determine the corresponding real-time spindle temperature range according to the difference between the maximum value and the minimum value of the real-time spindle temperature of the tool when machining the starting machining position; determine the temperature change weight according to the product of the spindle speed and the machining time when machining the starting machining position; normalize the product of the real-time spindle temperature range and the temperature change weight to determine the starting temperature change index of the starting machining position.

[0013] Further, the process of obtaining the temperature drop index includes:

[0014] Determine the corresponding machining moving distance according to the shortest equidistant circular arc length from the starting machining position to each machining position; determine the corresponding moving time length according to the ratio of the machining moving distance to the prior tool moving speed;

[0015] Determine a reference ambient temperature difference based on the difference between the maximum real-time temperature of the tool spindle during machining at the starting machining position and the prior ambient temperature;

[0016] During the moving time length, determine the reference cooling coefficient at each sampling moment according to the time difference between each sampling moment and the starting moment of the moving time length;

[0017] Determine the temperature drop index between the starting machining position and each to-be-machined position according to the reference ambient temperature difference, the reference cooling coefficient, and the moving time length.

[0018] Further, the process of determining the temperature drop index between the starting machining position and each to-be-machined position according to the reference ambient temperature difference, the reference cooling coefficient, and the moving time length includes:

[0019] Determine the local drop index at each sampling moment according to the ratio of the reference ambient temperature difference to the reference cooling coefficient; Normalize the product of the cumulative value of the local drop indices at all sampling moments and the moving time length to determine the temperature drop index between the starting machining position and each to-be-machined position.

[0020] Further, the process of obtaining the simulated starting temperature includes:

[0021] Obtain the prior temperature drop curve of the temperature at the end of the starting machining position under the prior ambient temperature; Use the temperature value corresponding to the moving time length in the prior temperature drop curve as the simulated starting temperature of each to-be-machined position.

[0022] Further, the process of obtaining the reference temperature change index includes:

[0023] Obtain the real-time temperature change curve of the tool spindle during machining at the starting machining position; Use the moment corresponding to the simulated starting temperature on the temperature change curve as the simulated sampling moment; Use the time interval length between the moment when machining at the starting machining position ends and the simulated sampling moment as the simulated time length;

[0024] Determine the cooling temperature change value according to the difference between the maximum real-time temperature of the tool spindle during machining at the starting machining position and the simulated starting temperature;

[0025] Determine the temperature rise rate of each to-be-machined position according to the ratio of the cooling temperature change value to the simulated time length; Normalize the product of the temperature rise rate and the machining time of each to-be-machined position to determine the reference temperature change index of each to-be-machined position.

[0026] Further, the process of obtaining the path passability includes:

[0027] According to the sum value of the reference temperature change index and the starting temperature change index, determine the corresponding temperature rise index; perform a negative correlation mapping on the difference between the temperature rise index and the temperature drop index to determine the temperature weight from the starting processing position to each to-be-processed position;

[0028] Perform a negative correlation mapping on the processing movement distance from the starting processing position to each to-be-processed position as the corresponding distance weight;

[0029] Normalize according to the product of the temperature weight and the distance weight to determine the path passability from the starting processing position to each to-be-processed position.

[0030] Further, the process of screening the next node processing position corresponding to the starting processing position according to the path passability includes:

[0031] Take the to-be-processed position with the maximum path passability as the next node processing position corresponding to the starting processing position.

[0032] Further, the process of obtaining the optimized path of the processing tool includes:

[0033] After taking the node processing position as the new starting processing position, calculate the new node processing position corresponding to the new starting processing position; and continue to screen the node processing positions with the new node processing position as the next starting processing position. After traversing all to-be-processed positions, obtain the optimized path of the processing tool of the CNC machine tool.

[0034] In a second aspect, the present application provides a processing tool path optimization system for a multi-axis CNC machine tool, and the system includes:

[0035] A data acquisition module, configured to obtain the processing time of each to-be-processed position on the workpiece and the spindle speed and spindle real-time temperature of the processing tool when processing the starting processing position during the process of processing the workpiece by the CNC machine tool;

[0036] A first determination module, configured to determine the starting temperature change index of the starting processing position according to the processing time, spindle speed, and spindle real-time temperature range of the starting processing position; determine the temperature drop index between the starting processing position and each to-be-processed position according to the distance between the starting processing position and each to-be-processed position, the maximum value of the spindle real-time temperature of the starting processing position, and the prior ambient temperature;

[0037] A second determination module, configured to determine the simulated starting temperature of each to-be-processed position based on prior temperature drop data, according to the distance between the starting processing position and each to-be-processed position and the temperature at the end of the processing at the starting processing position; and determine the reference temperature change index of each to-be-processed position according to the simulated starting temperature and the processing time of each to-be-processed position.

[0038] A node processing position screening module, configured to determine the path passability from the starting processing position to each to-be-processed position according to the starting temperature change index, the temperature drop index, the reference temperature change index, and the relative distance; and screen out the next node processing position corresponding to the starting processing position according to the path passability.

[0039] A processing tool path optimization module, configured to perform iterative screening of new node processing positions with the node processing positions, and obtain an optimized processing tool path for the numerical control machine tool after traversing all to-be-processed positions.

[0040] In a third aspect, the present application provides a computer device, including a memory and a processor. The memory is used to store computer program code, and the processor is used to call and run the computer program code from the memory to execute the method according to the first aspect or any embodiment of the first aspect of the present application.

[0041] In a fourth aspect, the present application provides a computer program product, where the computer program product includes computer program code, and when the computer program code is executed, it executes the method according to the first aspect or any embodiment of the first aspect of the present application.

[0042] In a fifth aspect, the present application provides a computer-readable storage medium, where the computer-readable storage medium stores computer program code, and when the computer program code is executed, it executes the method according to the first aspect or any embodiment of the first aspect of the present application.

[0043] The present application has the following beneficial effects:

[0044] Compared with the existing method of directly planning the path through the shortest distance, the present application takes into account the change in processing temperature and the temperature change between adjacent processing positions, minimizing the temperature change degree of the connected processing positions, thereby reducing the thermal error of the processing tool, that is, reducing the wear of the moving tool. First, obtain the initial temperature change index of the initial processing position through the initial processing position, calculate the temperature drop index during the movement of the tool, and at the same time, the reference temperature change index of the next connected processing position at this position, so that the path planning of the tool takes into account the temperature change of the connected processes, and combines the path length to select path nodes, making the path selection consider both efficiency and temperature impact, thereby determining a more reasonable tool processing path, that is, the effect of path planning according to the optimized path of the processing tool obtained by the present application is better. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to more clearly illustrate the technical solutions and advantages in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0046] Figure 1 Flowchart of a method for optimizing the machining tool path of a multi-axis numerical control machine tool provided by an embodiment of the present invention;

[0047] Figure 2 Structure diagram of a system for optimizing the machining tool path of a multi-axis numerical control machine tool provided by an embodiment of the present invention;

[0048] Figure 3 Structure schematic diagram of a computer device provided by an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0049] In order to further elaborate on the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the following combines the drawings and preferred embodiments to describe in detail the specific implementation manners, structures, features and effects of a system and method for optimizing the machining tool path of a multi-axis numerical control machine tool proposed according to the present invention. In the following description, different "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment, and the specific features, structures or characteristics in one or more embodiments can be combined in any suitable form. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as implying or suggesting relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of these features.

[0050] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field to which this invention belongs.

[0051] The following specifically describes the specific solutions of a machining tool path optimization system and method for a multi-axis numerical control machine tool provided by the present invention in conjunction with the accompanying drawings.

[0052] An embodiment of the present application provides a machining tool path optimization method for a multi-axis numerical control machine tool. Please refer to Figure 1 , which shows a flowchart of a machining tool path optimization method for a multi-axis numerical control machine tool provided by an embodiment of the present invention. The method includes:

[0053] Step S101: During the process of machining a workpiece by a numerical control machine tool, obtain the machining time of each machining position on the workpiece, as well as the spindle speed and the real-time spindle temperature of the tool when machining the starting machining position.

[0054] In a specific implementation manner of the embodiment of the present invention, determine the machining time of each machining position and the fixed spindle speed of each machining position through the instructions in the numerical control program of the numerical control machine tool; install a DS18B20 digital temperature sensor at the end of the spindle of the machining tool to collect the real-time spindle temperature; and set the sampling frequency to collect once per second, which can be adjusted according to the specific implementation environment.

[0055] In a specific implementation manner of the embodiment of the present invention, the starting machining position is selected as the position closest to the centroid of the workpiece. The implementer can select the starting machining position according to the specific implementation environment, and the machining positions to be machined are other unprocessed positions outside the starting machining position, which will not be elaborated further here. <C

[0056] Step S102: Determine the starting temperature change index of the starting machining position according to the machining time, spindle speed, and the range of the real-time spindle temperature of the starting machining position; determine the temperature drop index between the starting machining position and each machining position to be machined according to the distance between the starting machining position and each machining position to be machined, the maximum value of the real-time spindle temperature of the starting machining position, and the prior ambient temperature.

[0057] The main purpose of the present application is to plan the optimal path of the machining tool based on the cooling condition of the tool corresponding to different machining positions of the tool and the temperature change condition of the next machining process connected on the moving path as weights, so as to ensure that the temperature control of the tool is achieved through the cooling effect of the tool in the air during the machining process while minimizing the excessive wear of the tool, thereby reducing the wear of the tool and improving the machining accuracy, and making the effect of path planning better.

[0058] During the process of machining the machining position, the temperature corresponding to the cutting tool will gradually rise as the machining process progresses. The real-time temperature of the spindle during this process usually increases monotonically. The traditional method selects the machining position of the node in the order with the shortest machining movement distance during path selection; that is, the machining position closer to the starting machining position is machined first. However, the workpieces machined by multi-axis CNC machine tools are usually relatively complex, with high integration, many and concentrated machining positions. Then, when the cutting tool machines the concentrated machining positions, under the continuous high-intensity operation of the cutting tool, due to the long-term operation of the cutting tool, thermal error is caused, resulting in thermal deformation, which affects the life and accuracy. Therefore, on the basis of ensuring the machining efficiency, the process of shortest path planning is corrected by taking the temperature drop of the cutting tool and the temperature change of the next machining process connected on the movement path as weights, so as to obtain the optimal path.

[0059] The starting machining position is the starting point of machining, and its corresponding temperature change is related to the machining process. When the rotational speed of the cutting tool is faster and the machining time is longer, the more heat is generated when the cutting tool rubs against the workpiece, and the higher the temperature of the cutting tool; therefore, based on this principle, the temperature change of the starting machining position can be calculated. Preferably, in some possible implementation manners of the embodiments of the present invention, the process of obtaining the starting temperature change index includes:

[0060] According to the difference between the maximum value and the minimum value of the real-time spindle temperature when machining the starting machining position, the corresponding range of the real-time spindle temperature is determined; according to the product of the spindle speed and the machining time when machining the starting machining position, the temperature change weight is determined; the product of the range of the real-time spindle temperature and the temperature change weight is normalized to determine the starting temperature change index of the starting machining position. First, the real-time spindle temperature during the machining process usually shows a monotonically increasing situation. Therefore, the larger the range of the real-time spindle temperature, the more obvious the temperature change; the spindle speed can describe the severity of the temperature change. After combining the machining time, the temperature change situation of the machining process of the actual machining position is determined from the dimension of heat generation, that is, the starting temperature change index. It should be noted that the spindle speed of each machining position in the embodiments of the present invention is fixed. If the spindle speed of each machining position is not fixed in other implementation environments, the average value of the spindle speeds at all sampling moments during the machining process is calculated as the spindle speed for calculation, which will not be elaborated further here.

[0061] In a specific implementation manner of the embodiments of the present invention, the process of obtaining the starting temperature change index is expressed by the formula:

[0062]

[0063] Wherein, is the starting machining position The starting temperature change index; is the starting machining position The spindle speed; is the starting machining position The machining time during machining; is for the starting machining position The maximum value of the real-time temperature of the spindle of the cutting tool during machining; is for the starting machining position The minimum value of the real-time temperature of the spindle of the cutting tool during machining; is for the starting machining position The range of the real-time temperature of the spindle of the cutting tool during machining; is for the starting machining position The temperature change weight of the cutting tool during machining; is the linear normalization function; Since the real-time temperature of the spindle of the cutting tool during the machining process is usually monotonically increasing, the minimum value of the real-time temperature of the spindle is usually the spindle temperature at the start of machining, and the maximum value of the real-time temperature of the spindle is usually the spindle temperature at the end of machining.

[0064] When the starting machining position After machining is completed, at this time, the spindle of the machining tool reaches the maximum temperature under rotational friction. When the machining tool moves to the next machining position, the machining tool no longer rubs against the workpiece to generate heat, the heat source disappears, but the external temperature remains unchanged, and the tool starts to cool down. At this time, the cooling rate of the tool is only related to the machining movement distance between the current machining position where the tool is located and the machining position where the tool moves to the next machining position. The greater the machining movement distance to the next machining position, the greater the temperature drop. It should be noted that in the embodiments of the present invention, the way of machining movement for different machining positions is to move the machining tool while fixing the workpiece, and this way, compared with the case of fixing the tool and moving the workpiece, the ambient temperature will be lower. Therefore, when machining different machining positions in the case of fixing the tool, the ambient temperature will gradually rise and the heat dissipation capacity will decrease; while when moving the machining tool in the case of fixing the workpiece, the environment of the machining tool will change, making the ambient temperature constant, so the corresponding heat dissipation capacity is relatively stronger. Therefore, the present application selects the machining position switching method of moving the machining tool in the case of fixing the workpiece, that is, the ambient temperature during the movement is fixed. In the embodiments of the present invention, the ambient temperature is fixed at 25 degrees Celsius and needs to be adjusted according to the specific implementation environment.

[0065] Determine the corresponding machining movement distance according to the shortest equidistant circular arc length from the starting machining position to each to-be-machined position; determine the corresponding movement time length according to the ratio between the machining movement distance and the prior tool movement speed. In the embodiments of the present invention, the prior tool movement speed is a fixed value, that is, the fixed movement speed when the machining tool moves in the no-load state. In the embodiments of the present invention, the prior tool movement speed is set to 0.1 meter per second, and the implementer can adjust it according to the specific implementation environment. Moreover, the equidistant circular arc is a well-known technical means to those skilled in the art, and will not be further defined and elaborated herein. The longer the movement time length is, the longer the cooling time length of the tool in the non-machined state is, and the greater the degree of temperature drop is usually.

[0066] Preferably, in some possible implementation manners of the embodiments of the present invention, the obtaining process of the temperature drop index includes:

[0067] Determine the reference ambient temperature difference according to the difference between the maximum value of the real-time temperature of the spindle of the tool when machining the starting machining position and the prior ambient temperature; in the movement time length, determine the reference cooling coefficient at each sampling moment according to the time difference between each sampling moment and the starting moment of the movement time length; determine the temperature drop index between the starting machining position and each to-be-machined position according to the reference ambient temperature difference, the reference cooling coefficient and the movement time length. Specifically: determine the local drop index at each sampling moment according to the ratio of the reference ambient temperature difference and the reference cooling coefficient; normalize the product of the accumulated value of the local drop indices at all sampling moments and the movement time length to determine the temperature drop index between the starting machining position and each to-be-machined position.

[0068] First, for the reference ambient temperature difference, the greater the reference ambient temperature difference is, the faster the cooling speed is; and during the cooling process, the ambient temperature difference will become smaller and smaller, and the cooling speed will gradually slow down. Therefore, in order to more accurately quantify the temperature drop situation, this application disassembles and analyzes the cooling situation at each sampling moment. Based on the fact that the longer the cooling time is, that is, the greater the reference cooling coefficient is, the longer the time length passed during the cooling process is, resulting in the cooling speed becoming slower and slower, determine the local drop index at each sampling moment; since the local drop index is obtained through the ratio of the reference ambient temperature difference and the reference cooling coefficient, the local drop index conforms to the characteristic that the cooling speed becomes slower and slower as the cooling time becomes longer; finally, by combining the local drop indices at all sampling moments and through the product method, combine the movement time length representing the degree of temperature drop to more accurately represent the temperature drop index. Through the combination of dynamic local analysis, the representation of the degree of temperature drop is made more accurate.

[0069] In a specific implementation manner of the embodiments of the present invention, the obtaining process of the degree of temperature drop is expressed by the formula:

[0070]

[0071] in, Starting processing position With the Temperature drop index between the positions to be processed; Starting processing position With the The processing moving distance between the positions to be processed; is the prior tool moving speed; Starting processing position With the The length of time it takes to move between the positions to be processed; Starting processing position With the The number of sampling moments in the moving time length between the positions to be processed; Starting processing position The maximum real-time temperature of the tool spindle during machining; is the prior ambient temperature; is the reference ambient temperature difference; Starting processing position With the The length of time for moving between the positions to be processed The time difference between the sampling moment and the starting moment of the moving time length, that is, the reference cooling coefficient corresponding to the sampling moment; Starting processing position With the The length of time for moving between the positions to be processed The local decline index at each sampling moment; it should be noted that, in order to ensure that the calculation results are meaningful, when performing fractional operations in the embodiment of the present invention, when encountering a situation where the denominator is 0, it is necessary to add a parameter adjustment factor greater than 0 to the denominator to prevent the denominator from being 0. The value of the parameter adjustment factor is set by the implementer according to the actual situation. This application sets it to 0.1.

[0072] Step S103: Based on the prior temperature drop data, the simulated starting temperature of each position to be processed is determined according to the distance between the starting processing position and each position to be processed and the temperature at the end of processing at the starting processing position; and the reference temperature change index of each position to be processed is determined according to the simulated starting temperature and the processing time of each position to be processed.

[0073] For each position to be machined, during the machining process of the position to be machined, the change in the tool temperature is mainly caused by the frictional heat generated between the machining tool and the workpiece during the machining process of the position to be machined itself. The longer the machining time in the machining process, the more heat is generated. The starting temperature of the temperature change of the position to be machined is the cooling temperature when the machining tool moves to the position to be machined. In addition, if the temperature change during the machining process of the position to be machined is the same as that of the starting machining position, that is to say, the heat transfer of the tool to the outside world at different machining positions during the machining process is similar, that is, the heat dissipation degree is the same. Considering that the tool speeds of the same workpiece are usually relatively close, the influence of the tool speed adjustment on the temperature change will not be too obvious. Then, the temperature change curve of the position to be machined and the temperature rise curve of the starting machining position should be similar or relatively close.

[0074] Since the next position to be machined that the tool is to move to is to be selected at this time, it is impossible to actually measure the temperature data of each position to be machined, and the ambient temperature during the tool movement is fixed, and the temperature at the end of the machining of the starting machining position is known. Therefore, based on the prior data, the simulated starting temperature of each position to be machined can be obtained according to the temperature change under the condition that the ambient temperature is fixed. Preferably, in some possible implementation manners of the embodiments of the present invention, the process of obtaining the simulated starting temperature includes:

[0075] Obtain the prior temperature drop curve of the temperature at the end of the starting machining position under the prior ambient temperature; use the temperature value corresponding to the moving time length in the prior temperature drop curve as the simulated starting temperature of each position to be machined. The prior temperature drop curve is the prior temperature drop curve of the temperature at the end of the starting machining position obtained in advance under the prior ambient temperature. Since the time for moving to each position to be machined is known, the corresponding simulated starting temperature can be obtained based on the prior temperature drop curve; in other possible implementation manners of the embodiments of the present invention, in order to reduce the error of the simulated starting temperature, at least two prior temperature drop curves can be selected, and the average value of the temperature values corresponding to the moving time length in all the prior temperature drop curves is used as the simulated starting temperature to reduce the error.

[0076] After determining the simulated starting temperature, the estimated temperature change situation of each position to be machined, that is, the reference temperature change index, can be determined based on the temperature change trend when machining the starting machining position and the machining time length of each position to be machined in the numerical control program.

[0077] In a specific implementation manner of the embodiments of the present invention, the process of obtaining the reference temperature change index includes:

[0078] Obtain the real-time temperature change curve of the spindle of the tool during machining at the starting machining position; take the moment corresponding to the simulated starting temperature on the temperature change curve as the simulated sampling moment; take the time interval length between the moment when machining at the starting machining position ends and the simulated sampling moment as the simulated time length; determine the cooling temperature change value according to the difference between the maximum real-time temperature of the spindle of the tool during machining at the starting machining position and the simulated starting temperature; determine the temperature rise rate of each to-be-machined position according to the ratio between the cooling temperature change value and the simulated time length; normalize the product of the temperature rise rate and the machining time of each to-be-machined position to determine the reference temperature change index of each to-be-machined position. Among them, the acquisition of the real-time temperature change curve of the spindle can be carried out by curve fitting based on the real-time temperature of the spindle collected at each sampling moment to determine the corresponding real-time temperature change curve of the spindle. Curve fitting is a well-known technical means for those skilled in the art and will not be further elaborated here.

[0079] Since the vertical axis of the real-time temperature change curve of the spindle is temperature and the horizontal axis is time, the ratio between the cooling temperature change value and the simulated time length represents the change slope of temperature and can reflect the change trend of temperature; based on this trend, the longer the machining time of the to-be-machined position, the greater the amplitude of its temperature change. Therefore, by multiplying the temperature rise rate and the machining time corresponding to the to-be-machined position, the reference temperature change index characterizing the temperature change of each to-be-machined position is determined. For the acquisition process of the cooling temperature change value, because the temperature change trends or slopes at different positions on the real-time temperature change curve of the spindle are usually different, in order to make the analysis of the temperature change index in combination with the temperature change trend more accurate, according to the characteristic that the temperature change curves of different machining positions are usually similar, the temperature change trend after the simulated starting temperature is combined for analysis, so as to more accurately reflect the temperature change of the to-be-machined position and improve the accuracy of the obtained reference temperature change index.

[0080] In a specific implementation manner of the embodiment of the present invention, the acquisition process of the reference temperature change index is expressed by the formula:

[0081]

[0082] Among them, [[ID=…]] is the reference temperature change index of the th to-be-machined position; is the machining time of the th to-be-machined position; is the maximum real-time temperature of the spindle of the tool during machining at the starting machining position ; is the simulated starting temperature of the th to-be-machined position; is the starting machining position The time interval length between the moment at the end of machining and the simulated sampling moment of the th to-be-machined position, that is, the simulated time length; is the starting machining position and the th to-be-machined position; the cooling temperature change value; is the th to-be-machined position; the temperature rising rate.

[0083] Step S104: Determine the path passability from the starting machining position to each to-be-machined position according to the starting temperature change index, the temperature drop index, and the reference temperature change index; screen out the next node machining position corresponding to the starting machining position according to the path passability.

[0084] After the starting machining position is completed, the next machining position needs to be selected as the next node of the path; in the selection of the path, selecting by distance can improve efficiency, while selecting by temperature change can reduce the influence of thermal error and improve machining accuracy; therefore, a comprehensive analysis is carried out by combining distance and temperature change to determine the path passability of each to-be-machined position, so that the path normalization can take into account both efficiency and the influence of thermal error, making the path selection more reasonable and improving the effect of tool path planning.

[0085] Preferably, in some possible implementation manners of the embodiments of the present invention, the process of obtaining the path passability includes:

[0086] Determine the corresponding temperature rising index according to the sum value of the reference temperature change index and the starting temperature change index; perform a negative correlation mapping on the difference between the temperature rising index and the temperature drop index to determine the temperature weight from the starting machining position to each to-be-machined position; perform a negative correlation mapping on the machining moving distance between the starting machining position and each to-be-machined position as the corresponding distance weight; normalize according to the product of the temperature weight and the distance weight to determine the path passability from the starting machining position to each to-be-machined position.

[0087] Among them, both the reference temperature change index and the starting temperature change index characterize the degree of temperature rise in the overall machining process from the starting machining position to each to-be-machined position, while the temperature drop index characterizes the degree of temperature drop in the overall machining process from the starting machining position to each to-be-machined position; overall, the more the degree of overall temperature rise, the worse the path passability of the to-be-machined position in the dimension of temperature, and the more likely it is to have heat accumulation leading to thermal deformation. Therefore, the corresponding temperature weight should be smaller. Therefore, after combining the temperature rise index with the reference temperature change index and the starting temperature change index, the difference between the temperature rise index and the temperature drop index is negatively correlated and mapped to obtain the corresponding temperature weight; the distance weight conforms to the characteristic that the smaller the distance, the higher the path passability. Therefore, the machining movement distance is also negatively correlated and mapped; thus, the path passability is comprehensively determined by combining the temperature weight and the distance weight, making the obtained path passability more objective and accurate, and improving the efficiency and accuracy of tool path planning.

[0088] In a specific implementation manner of the embodiment of the present invention, the process of obtaining the path passability is expressed by the formula as follows: ; where is the starting machining position to the th path passability of the to-be-machined position; is the starting machining position and the th machining movement distance between the to-be-machined positions; is the starting machining position to the th temperature rise index of the to-be-machined position; is the starting machining position to the th temperature weight of the to-be-machined position; is the starting machining position to the th distance weight of the to-be-machined position.

[0089] Furthermore, the process of screening the next node machining position corresponding to the starting machining position according to the path passability includes: taking the to-be-machined position with the largest path passability as the next node machining position corresponding to the starting machining position. The larger the path passability, the better the passability of the to-be-machined position in terms of distance and temperature, and the more suitable it is as the next path node. Therefore, the to-be-machined position with the largest path passability is selected as the next node machining position.

[0090] Step S105: Iteratively screen the new node machining positions with the node machining positions, and obtain the optimized path of the machining tool of the numerical control machine tool after traversing all the to-be-machined positions.

[0091] Since the overall machining process of the machining tool needs to machinemachining positions to be machined one by one, the machining tool path needs to traverse all machining positions to be machined. Therefore, after screening out the next node machining position corresponding to the starting machining position, it is necessary to screen out new node machining positions based on the obtained node machining positions, so as to gradually complete the machining operation on all machining positions to be machined.

[0092] Preferably, in some possible implementation manners of the embodiment of the present invention, the process of obtaining the optimized path of the machining tool includes:

[0093] After using the node machining position as the new starting machining position, calculate the new node machining position corresponding to the new starting machining position; and continue to use the new node machining position as the next starting machining position to screen the node machining positions. After traversing all machining positions to be machined, the optimized path of the machining tool of the CNC machine tool is obtained. After obtaining the next node machining position of the starting machining position for the first time, after the tool machining process is performed on this node machining position, at this time, this node machining is used as the new starting machining position to screen the next node machining position. After screening out the new node machining position, perform machining on the new node machining position and continue to select the node machining position as another new starting machining position until all machining positions to be machined are completed. It should be noted that the machined machining positions to be machined are not used for screening subsequent node machining positions, and when the moment corresponding to the simulated starting temperature cannot be obtained on the real-time temperature change curve of the main shaft of the new starting machining position, the simulated sampling moment corresponding to the simulated starting temperature can be determined by combining the interpolation method, which will not be elaborated further here.

[0094] In summary, a method for optimizing the machining tool path of a multi-axis CNC machine tool minimizes the temperature change degree of the connected machining positions by considering the change in machining temperature and the temperature change between adjacent machining positions, thereby reducing the thermal error of the machining tool, that is, reducing the wear of the moving tool. First, obtain the starting temperature change index of the initial machining position through the initial machining position, calculate the temperature drop index during the movement of the tool, and at the same time, the reference temperature change index of the next machining position connected at this position, so that the path planning of the tool takes into account the temperature change of the connected processes, and combines the path length to select path nodes, making the path selection consider both efficiency and temperature influence, so as to determine a more reasonable tool machining path, that is, the effect of path planning according to the optimized machining tool path obtained in this application is better.

[0095] The present application also provides a machining tool path optimization system for a multi-axis CNC machine tool. Please refer to Figure 2, which shows the structural diagram of a machining tool path optimization system for a multi-axis numerical control machine tool provided by an embodiment of the present invention. The system includes: a data acquisition module 201, a first determination module 202, a second determination module 203, a node machining position screening module 204, and a machining tool path optimization module 205.

[0096] The data acquisition module is used to obtain the machining time of each machining position on the workpiece and the spindle speed and spindle real-time temperature of the machining tool when machining the starting machining position during the process of machining the workpiece by the numerical control machine tool.

[0097] The first determination module is used to determine the starting temperature change index of the starting machining position according to the machining time, spindle speed, and range of spindle real-time temperature of the starting machining position; and determine the temperature drop index between the starting machining position and each machining position according to the distance between the starting machining position and each machining position, the maximum value of the spindle real-time temperature of the starting machining position, and the prior environmental temperature.

[0098] The second determination module is used to determine the simulated starting temperature of each machining position based on the prior temperature drop data, according to the distance between the starting machining position and each machining position and the temperature at the end of machining of the starting machining position; and determine the reference temperature change index of each machining position according to the simulated starting temperature and the machining time of each machining position.

[0099] The node machining position screening module is used to determine the path passability from the starting machining position to each machining position according to the starting temperature change index, temperature drop index, reference temperature change index, and relative distance; and screen out the next node machining position corresponding to the starting machining position according to the path passability.

[0100] The machining tool path optimization module is used to iteratively screen new node machining positions with the node machining positions, and obtain the optimized machining tool path of the numerical control machine tool after traversing all machining positions.

[0101] It should be noted that for the system provided in the above embodiment, only the above division of each functional module is used for illustration. In actual application, the above functions can be allocated to different functional modules according to needs, that is, the internal structure of the computer device is divided into different functional modules to complete all or part of the functions described above. In addition, a machining tool path optimization system for a multi-axis numerical control machine tool provided in the above embodiment and an embodiment of a machining tool path optimization method for a multi-axis numerical control machine tool belong to the same concept. The specific implementation process is detailed in the method embodiment and will not be repeated here.

[0102] An embodiment of the present application also provides a computer device. Please refer to Figure 3, which shows a schematic structural diagram of a computer device provided by an embodiment of the present invention. The computer device includes a memory 301, a processor 302, and a computer program 303 stored in the memory 301 and running on the processor 302. When the processor 302 executes the computer program 303, the computer device can execute any one of the machining tool path optimization methods of the multi-axis numerical control machine tools introduced above.

[0103] An embodiment of the present application also provides a computer program product. When the computer program product runs on a computer device, the computer device can execute any one of the machining tool path optimization methods of the multi-axis numerical control machine tools introduced above.

[0104] An embodiment of the present application also provides a computer-readable storage medium. Computer program code is stored in the computer-readable storage medium. When the computer program code runs on a computer device, the computer device can execute any one of the machining tool path optimization methods of the multi-axis numerical control machine tools introduced above.

[0105] In the embodiments provided in the present application, it should be understood that the provided computer device, computer program product, and computer-readable storage medium are all used to execute the corresponding methods provided above. Therefore, the beneficial effects that can be achieved can refer to the beneficial effects in the methods provided above, which will not be elaborated here.

[0106] It should be noted that the above order of the embodiments of the present invention is only for description and does not represent the advantages and disadvantages of the embodiments. The processes depicted in the drawings do not necessarily require the specific order or continuous order shown to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0107] Each embodiment in this specification is described in a progressive manner. The same or similar parts among the embodiments can be referred to each other. Each embodiment focuses on the differences from other embodiments.

Claims

1. A method for optimizing tool paths for multi-axis CNC machine tools, characterized in that: The method comprises: During the process of machining a workpiece using a CNC machine tool, the machining time of each position to be machined on the workpiece and the spindle speed and real-time spindle temperature of the machining tool when machining the starting machining position are obtained; Determine the starting temperature variation index of the starting processing position based on the processing time, spindle speed, and real-time spindle temperature extreme difference of the starting processing position; determine the temperature drop index between the starting processing position and each position to be processed based on the distance between the starting processing position and each position to be processed, the maximum real-time spindle temperature at the starting processing position, and the prior ambient temperature; Based on the prior temperature drop data, determining a simulated starting temperature for each position to be processed according to the distance between the starting processing position and each position to be processed and the temperature at the end of processing at the starting processing position; determining a reference temperature change index for each position to be processed according to the simulated starting temperature and the processing time of each position to be processed; Determining the path passability from the starting processing position to each to-be-processed position based on the starting temperature change index, the temperature drop index, the reference temperature change index, and the relative distance; and selecting the next node processing position corresponding to the starting processing position based on the path passability; Iteratively screening new node processing positions based on the node processing positions, and obtaining an optimized processing tool path for a CNC machine tool after traversing all positions to be processed; Determine the corresponding processing movement distance based on the shortest equidistant loop arc length from the starting processing position to each position to be processed; determine the corresponding temperature rise index based on the sum of the reference temperature change index and the starting temperature change index; and perform negative correlation mapping on the difference between the temperature rise index and the temperature drop index to determine the temperature weight from the starting processing position to each position to be processed; Negative correlation mapping is performed on the processing moving distance between the starting processing position and each position to be processed as the corresponding distance weight; Normalization is performed based on the product of the temperature weight and the distance weight to determine the passability of the path from the starting processing position to each position to be processed.

2. The method for optimizing tool paths for multi-axis CNC machine tools according to claim 1, wherein: The process of obtaining the starting temperature change index includes: According to the difference between the maximum spindle temperature and the minimum spindle temperature when processing the starting processing position, the corresponding spindle real-time temperature range is determined; according to the product between the spindle speed and the processing time when processing the starting processing position, the temperature change weight is determined; the product between the spindle real-time temperature range and the temperature change weight is normalized to determine the starting temperature change index of the starting processing position.

3. The method for optimizing tool paths for multi-axis CNC machine tools according to claim 1, wherein: The process of obtaining the temperature drop index includes: According to the ratio between the machining moving distance and the prior tool moving speed, the corresponding moving time length is determined; Determine the reference ambient temperature difference according to the difference between the maximum real-time temperature of the spindle of the tool when machining the starting machining position and the prior ambient temperature; In the moving time length, determining the reference cooling coefficient at each sampling moment according to the time difference between each sampling moment and the starting moment of the moving time length; A temperature drop index between a starting processing position and each position to be processed is determined according to the reference ambient temperature difference, the reference cooling coefficient, and the moving time length.

4. The method for optimizing tool paths for multi-axis CNC machine tools according to claim 3, wherein: The process of determining the temperature drop index between the starting processing position and each to-be-processed position according to the reference ambient temperature difference, the reference cooling coefficient, and the moving time length includes: According to the ratio of the reference ambient temperature difference and the reference cooling coefficient, the local drop index at each sampling moment is determined; the accumulated value of the local drop index at all sampling moments is normalized by the product of the moving time length to determine the temperature drop index between the starting processing position and each position to be processed.

5. The method for optimizing tool paths for multi-axis CNC machine tools according to claim 3, wherein: The process of obtaining the simulation starting temperature includes: Obtain a priori temperature drop curve of the temperature at the end of the starting processing position under the prior ambient temperature; and use the temperature value corresponding to the moving time length in the priori temperature drop curve as the simulated starting temperature of each position to be processed.

6. The method for optimizing tool paths for multi-axis CNC machine tools according to claim 1, wherein: The process of obtaining the reference temperature change index includes: Obtaining a real-time temperature change curve of the tool spindle when machining the starting machining position; using the moment corresponding to the simulated starting temperature on the temperature change curve as the simulation sampling moment; and using the time interval between the moment when machining the starting machining position ends and the simulation sampling moment as the simulation time length; determining a cooling temperature change value according to a difference between a maximum real-time temperature of a spindle of a tool when machining a starting machining position and the simulated starting temperature; The temperature rise rate of each position to be processed is determined according to the ratio between the cooling temperature change value and the simulation time length; the product between the temperature rise rate and the processing time of each position to be processed is normalized to determine the reference temperature change index of each position to be processed.

7. The method for optimizing tool paths for multi-axis CNC machine tools according to claim 1, wherein: The process of selecting the next node processing position corresponding to the starting processing position according to the path passability includes: The position to be processed with the largest path passability is used as the next node processing position corresponding to the starting processing position.

8. The method for optimizing tool paths for multi-axis CNC machine tools according to claim 1, wherein: The process of obtaining the optimized path of the machining tool includes: After taking the node processing position as the new starting processing position, the new node processing position corresponding to the new starting processing position is calculated; and the new node processing position is continued to be used as the next starting processing position to screen the node processing position. After traversing all the positions to be processed, the optimized processing tool path of the CNC machine tool is obtained.

9. A tool path optimization system for a multi-axis CNC machine tool, characterized in that: The system comprises: A data acquisition module is used to obtain the processing time of each to-be-processed position on the workpiece and the spindle speed and real-time spindle temperature of the machining tool when processing the starting processing position during the process of machining the workpiece by the CNC machine tool; The first determination module is configured to determine a starting temperature variation index of the starting processing position based on the processing time, spindle speed, and real-time spindle temperature extreme difference of the starting processing position; and to determine a temperature drop index between the starting processing position and each position to be processed based on the distance between the starting processing position and each position to be processed, the maximum real-time spindle temperature at the starting processing position, and the prior ambient temperature; a second determining module, configured to determine, based on the prior temperature drop data, a simulated starting temperature for each position to be processed according to the distance between the starting processing position and each position to be processed and the temperature at the end of processing at the starting processing position; and determine a reference temperature variation index for each position to be processed according to the simulated starting temperature and the processing time of each position to be processed; a node processing position screening module, configured to determine the path passability from the starting processing position to each to-be-processed position based on the starting temperature change index, the temperature drop index, the reference temperature change index, and the relative distance; and to screen the next node processing position corresponding to the starting processing position based on the path passability; Determine the corresponding processing movement distance based on the shortest equidistant loop arc length from the starting processing position to each position to be processed; determine the corresponding temperature rise index based on the sum of the reference temperature change index and the starting temperature change index; and perform negative correlation mapping on the difference between the temperature rise index and the temperature drop index to determine the temperature weight from the starting processing position to each position to be processed; Negative correlation mapping is performed on the processing moving distance between the starting processing position and each position to be processed as the corresponding distance weight; Normalizing the product of the temperature weight and the distance weight to determine the passability of the path from the starting processing position to each position to be processed; The machining tool path optimization module is used to iteratively screen new node machining positions based on the node machining positions, and obtain the machining tool optimization path of the CNC machine tool after traversing all the positions to be machined.

Images